donovan fourie 13 january 2015

Sustainable solutions for Cooling Towers

Donovan Fourie January 2015

Copyright: Donovan Fourie

UOC Dissertation Final paper

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TABLE OF CONTENT

List of exhibits 3 1. Abstract 4 2. Introduction 5

Key terms 6 3. Literature review 7 4. Methodology 14

4.1. ESKOM Sustainable business practices 14 4.2. Sustainable maintenance for power station cooling towers 15 A. Measurability of the current maintenance practices on cooling towers 20

1. Profit 20 i. Project cost for maintenance 20 ii. Loss of income during maintenance 21 iii. Lower income from reduced production 21

2. Planet 24 i. Water 24 a. Water disposed of during outage 24 b. Evaporation of water 25 ii. CO2 emissions 26

3. People 27 B. Measurability of sustainable maintenance of cooling towers 28

1. Profit 29 i. Project cost for sustainable maintenance 29 ii. Loss of income during sustainable maintenance project 29 iii. Impact on operational income 29

2. Planet 30 i. Water 30 a, Water disposed of during outage 30 b. Evaporation of water 30 ii. CO2 emissions 30

3. People 30 i. Healthy working environment 30 a. Blocked pipes 30 b. Sludge 31

5. Analysis of results 32 1. Profit 32

i. Direct cost of cooling tower maintenance 32 ii. Impact on income during outage 32 iii. Impact of operating temperatures on income 33

2. Planet 34 i. Water 34 a. Water lost through disposal during maintenance 34 b. Impact of maintenance on evaporation losses 35 ii. CO2 emissions 35

3. People 35 Summary of analysis 36

6. Conclusion 38 7. References 39 8. Reviewed literature 43 9. Bibliography 44 10. Appendices 46 11. Interviews 55 12. Acknowledgements 55 13. Statement of originality 55


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LIST OF EXHIBITS FIGURES

1. Eskom statement of sustainable development 46 2. Eskom sustainable assurance statement 46 3. CO2 emissions vs. plant efficiency 47 4. Relation between cooling-water temperature and condenser pressure 47 5. Schematic layout of the steam-electric process of a power plant 48 6. Cooling tower efficiency with enhanced distribution system 48 7. Cooling tower efficiency uniform sprayer layout vs enhanced sprayer layout 49 8. Illustration of the power generation process equipment 15 9. Heat-liquid cycle in coal-fired power generation 16 10. Heat balance of coal-fired power generation 16 11. Hypothetical heat balance diagram for coal-fired power station 17 12. Hypothetical relationship between heat used in generation and heat rejection 18 13. Carnot thermal efficiency of the liquid cycle in power generation 18 14. Estimated maintenance cost for a cooling tower 21 15. Potential loss of income contributed to cooling towers during an outage 21 16. Kriel average yearly temperatures 49 17. Relationship between cooling-water temperature and generation output 22 18. Eskom tariffs 50 19. Average weighted selling price of electricity 50 20. Relationship between cooling-water temperature and loss of income 22 21. Relationship between temperatures of serviced / un-serviced cooling towers 23 22. Water consumption by economic sector 24 23. Average water consumption of South Africa family 50 24. Quantity of water lost during maintenance on a cooling tower 25 25. Coal-fired plants in ESKOM data set 51 26. Efficiency related water losses 25 27. Relationship between CO2 emissions and plant efficiency 26 28. Comparison of legionella counts at KPS 51 29. On-site data taken during sustainable maintenance project 52 30. On-site cooling-water temperatures vs ambient temperatures 28 31. Actual data from KPS for the combined cooling-water temperature 28 32. Estimated cost of sustainable maintenance on a cooling tower 29 33. Blocked distribution pipes found at KPS pipes 30 34. Sludge removed from cooling tower no 4 31 35. Comparable costs of maintenance process 32 36. Loss of income during outage 33 37. Impact of maintenance on cooling-water temperatures 33 38. Loss of income contributed to a two yearly maintenance program 34 39. Water lost through maintenance 34 40. Water lost through lower efficiency 35 41. Water tariffs from the South African Rand Water Board 52 42. Triple bottom-line results 37

TABLES

A. KPS technical data 53 B. Evaporation losses in cooling towers 54


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1. ABSTRACT This paper examines the effect that sustainable on-line maintenance of cooling towers will have on the sustainability of a power station. By examining the sustainable issues at a power station, 1) profit 2) planet 3) people, it comes to light that the maintenance on the cooling towers does has a direct impact on the triple bottom line of a coal-fired power station. Evidence shows that irregular maintenance will have a negative impact on the income of the power station, CO2 emissions will be higher, water will be wasted and even human life can be lost Cooling towers are auxiliary equipment at the power station, it is often neglected and the effect that the cooling towers have on the sustainability is not seen as very important. Maintenance are often neglected and not done at the required intervals due to the high demand of electricity in South Africa. Cooling of the heat-liquid cycle in the coal-fired electricity generation process is a critical factor in the efficiency of the generation process and irregular maintenance of the cooling towers does have a negative impact on the efficiency of the cooling system. A loss of generation capacity is evident in the event of a faltering cooling system; this leads to substantial financial losses, the faltering cooling system also leads to the waste of valuable water and have a negative impact on the carbon footprint of the power station. Finally the lack of regular maintenance can lead to the loss of life where fouling in the cooling towers creates breeding environments for legionnaires bacteria On-line sustainable maintenance is possible and can be done at regular intervals without affecting the electricity generation process. Quantitative research from data collected from literature, published reports and other sources gives evidence of the effects that a faltering cooling system will have on the efficiency of the generation process. Actual data collected and interviews done during a sustainable on-line maintenance project show the advantages achieved by doing on-line sustainable maintenance. Millions of Rands will be saved, CO2 emissions will be lower, enough water to sustain thousands of families will be saved and it can save a life Sustainable on-line maintenance of cooling towers should be implemented at coal-fired power stations


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2. INTRODUCTION CSR / Sustainable business practices are the key to success for any enterprise in today’s complex world where natural resources are dwindling UNAC, (2013), the markets are more competitive Tirole. (2014) and an increasing population growth WHO, (2014) that puts more pressure on business to ensure a sustainable future. For a greener future all facets of business must be put under the spotlight and sustainable solutions must be found. At Eskom’s Kriel power station an attempt has been made to implement an innovative on-line sustainable maintenance solution for the maintaining of the cooling towers giving the opportunity the study the effects of on-line maintenance on the cooling towers As sustainability stands on three legs, Profits, the Planet (Natural environment) and the People, the objective off this research is to investigate the effects that sustainable maintenance practices will have on the sustainability of the power station. Firstly by looking at the financial impact of sustainable maintenance, secondly to see whether it will be beneficial to the environment by examining the impact it will have on the CO2 emissions of the power station and whether it will save enough water to be seen as a sustainable route for the power station to follow on the quest to sustainable business practice and finally to see if sustainable maintenance will improve the quality of the environment in and around the cooling towers to create a healthier working environment for the employees at the power station Current maintenance practices only allows for periodic maintenance on the power station cooling towers; either during a scheduled outage at the power station or in the event of an emergency breakdown giving an window of opportunity for maintenance. The problems associated with this maintenance philosophy are that this modus operandi leads to higher operating temperatures over extended periods causing lower production levels (loss of income), higher CO2 emissions (already over the legal GHG emission levels at KPS), excessive water losses (higher temperatures leads to higher water evaporation rates) and creating a breeding environment for legionella (a life threatening bacterium). This research aims to investigate the possibility to employ an alternative philosophy for innovative maintenance procedures and to prove that sustainable on-line maintenance practices can increase the production of the power station, lower the CO2 emissions, save water and create a healthier working environment To understand the extent of the problem regarding cooling tower maintenance, we need to understand that most industrial processes, in this case the generation of electricity, generates heat while in operation, excessive heat in the process or in the equipment will lead to failure of the process or the process equipment, thus effective cooling of these processes and equipment are crucial for sustained production Industrial cooling towers are part of the critical chain in any industrial manufacturing process. “It is commonly used to dissipate heat from power generation units, water-cooled air-conditioning units and industrial manufacturing processes” Shah, Rathod (2012). Cooling towers are however by nature of design unsustainable; firstly due to the water evaporation “required to affect the cooling of the water heated during the process” Fisenko, et al (2001) Jagadeesh and Reddy (2013) and secondly due to the resulted contamination of the water caused by the fact that pure water that escapes during the evaporation process and dissolved solids contained in the cooling water is left behind in the process. The air scrubbing effect of the water falling through the cooling tower causes further contamination of the cooling towers; Dust carried by the air flowing through the cooling tower is captured by the falling water and deposited in the cooling pond Haines, Myers. (2009). The final contributing factor of contamination of the cooling tower ponds comes from the scale build-up in the pipe network and condensers that breaks loose from inside the pipes/condensers and is carried by the flow of the water to the cooling towers. It should be noted that a lack of maintenance to prevent the above issues further leads to less effective cooling and higher water temperatures, resulting in more loss of water through greater evaporation at higher temperatures. From these points we can also make the assumption that cooling towers are one of the culprits that can lead to water shortages if unchecked Naidu-Hoffmeester (2014). Current practices at power stations for the maintenance of the cooling towers, or rather the lack of regular maintenance, leads to more wasted water and loss of production to the related industries. In these conditions of blocked pipes, dirty water (big quantities of sludge accumulated in the bottom of the cooling ponds) and higher temperatures, we also find the possible growth of the legionella bacteria, which is a life-threatening bacterium, creating a very dangerous working environment The maintenance process currently/historically in practice for maintaining cooling towers is restricted to periods when there can be an outage on an electricity generation unit or a break in the production


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schedule of a manufacturing process; the maintenance process followed is thus shutting down a production unit, disposal of the water used in the cooling system and cleaning the cooling towers and the cooling water reservoirs/ponds by manual/mechanical methods and cleaning/servicing the water distribution system after which the water is replaced from commercial sources. A new sustainable approach in the process of maintenance, which is working on-line to do cleaning of the reservoirs/ponds and servicing the distribution system while in operation, is possible. This on-line cleaning of cooling towers in the power generation industry can provide a sustainable alternative to improve the PPP of a power station Key terms. ESKOM – Electricity Supply Corporation of South Africa. A state owned corporation responsible for provision of electricity to the whole of South Africa GHG – Green House Gasses. Gasses releases into the atmosphere contributing to global warming HR – heat rate. Thermal efficiency of a power generation plant kj/kg – kilojoules per kilogram Kj/kWh – kilojoules per kilowatt-hour KPS – Kriel power Station. Coal-fired power generation plant near Witbank in South Africa Load shedding – Shutting down the electricity supply the areas periodically as the demand for electricity exceeds the supply from the electricity grid. CFU – Colony forming units. Unit to measure the presence of legionella bacterium CSP – Corporate social practices CSR – Corporate social responsibility CO2 – Carbon dioxide. Poisonous gas that is the greatest contributor to global warming PPP – Profit, planet and people. Also known as the triple bottom line Outage – Scheduled shutting down of production for a period enabling maintenance On-line maintenance – working on a production unit without stopping production DEA – Department of environmental affairs SHE – Safety Health Environment η(cc) – cooling tower efficiency


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3. LITERATURE REVIEW Finding answers to improve the sustainability for a power station faces many challenges and the key to achieving sustainability at a power station is to understand the principles of sustainability and identifying the various components of a power station and to understand where they fit into the overall sustainability picture. Major concerns at power stations are the level of electricity generation output and the resulted effect on the environment. But what are the causes of the sustainability problems and how can these causes be eliminated. Cooling towers are often neglected as it is generally seen as auxiliary equipment and the importance of the maintenance thereof does not receive the priority it deserves. Identifying the cooling towers as a key component in the electricity generation process, it does have an influence on the power station sustainability and finding a sustainable solution for the maintenance of the cooling towers can bring relieve to some of the sustainability challenges Numerous studies such as Quinn, Baltes (2007) Laasch, Connaway (2013) have been undertaken on CSR and sustainability. The Coal Advisory Board (2008) explains the reason of the existence of coal-fired power stations and the negative effect from coal-fired power stations on the environment caused by the CO2 emissions from the coal-fired power stations. Research into the process of coal-fired electricity generation and the related issues such as power plant efficiency and cooling systems for the power plants comes from a multitude of sources. Naijar Shaw, Adams, Jirka, Harleman (1979), Randhire (2014) Hill, Osborn (1990) Scott (1995) provides investigations into the performance and efficiency of the coal-fired electricity generation process and the effect that cooling-water and the cooling towers has on the process. Note that Randhire (2014) was included out of chronological order to provide an explanation required in the sequence of the research. Delgado, Hertzog (2012) provides research regarding the water consumption of power plants. The European Commission IPPC (2001) conducted an investigation into the best available practices for maintaining cooling towers and that a lack of maintenance will lead to the growth of the legionella bacteria, a life threatening disease, in cooling towers. Investigations and research done by Srisawai (2000) and Health and Safety Executive (1999) proves that the maintenance of cooling towers are essential for the control of the growth of colony forming legionella bacteria in the cooling tower environment. Literatures into the specific issues of maintaining the power station cooling towers are however fairly vague with a lack of rigorous research into the topic. There are numerous articles and opinions by private companies doing maintenance work on cooling towers but without any substantiating evidence. Maintenance is crucial to sustainability of the cooling-water systems and current maintenance practices leads to the neglect of maintaining the cooling towers. Finding a sustainable solution for maintenance must be prioritized Sustainability of an organization can only be successful if there is a team effort and commitment from not only the management but from every person involved in the organization. Quinn (2007) discusses the commitment from leadership and states that in many instances there are a commitment and an understanding from leaders but it is debatable whether this commitment is also from the lower ranks of the organization. Eskom has a commitment from the top management structure but does this commitment go through to the lower ranks? Sustainability is everybody’s business. The author further discusses the role of leadership and the concept of implementing strategies that will bring the TBL to everybody’s attention. Understanding the challenges of implementing sustainability throughout an organization is the only way to achieve real results. Even if management is committed, they need to understand what the obstacles are in the way of reaching their sustainable goals. These sustainability goals must be communicated clearly throughout the organization and a commitment from everybody is required to achieve these sustainability goals. The author has a PHD in Organizational communication and Co-author a master’s degree in business. The authors have supplied various sources that will support their viewpoints of the importance of a TBL implementation

In conclusion it can be said that communication from the top down to the lower ranks is the way to achieve better sustainability. Strategies, goals and clear guidelines must be clear throughout an organization and the results have to be measured to ensure the successful implementation thereof. As the author states, “…. as any leader knows, what gets measured gets attention”

We must take into consideration that Eskom is a semi-state owned entity, which makes their responsibility towards the people of South Africa and towards the environment even greater. Laasch (2013) quotes the sustainability mission of a certain company and he states that this quote displays the very essence of what sustainable management is all about. “We strive to do business in a more enlightened way, where we take responsibility for the impact of our business on the society and the environment, aiming to move these impacts from negative to neutral or (better still) positive. It’s part of


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our quest to become a truly sustainable business where we have a net positive effect on the wonderful world around us.”

By implication, it is not about doing something regarding some of the actions we take. Rather, it is about what we do in every action that we take

Eskom has made a commitment to being sustainable Figure 1 and Figure 2. The author classifies sustainable business into 5 categories; (1) A below average unsustainable business, (2) An average unsustainable business, (3) A sustainable business, (4) A neutral impacts business, (5) A restorative business. Where does Eskom’s KPS fit into this picture? According to eNCA; KPS is exceeding the legal CO2 emission limits and “The DEA has said that Eskom is breaking the law by continuing to run Kriel power station …... DEA Deputy Director General for Quality and Climate Change Judy Beuamont told eNCA that the issue of non-compliance affects people’s health …... ” Bothma (2013). KPS has been reported as non-compliant regarding its CO2 emissions Greenbusiness guide (2013), Jans (2014). This gives the indication that KPS will fall under category (1), defined as a business with a net negative triple bottom line. Further investigation Eskom Integrated report (2014) reveals that Eskom is not only attempting to be fully sustainable but also employs an auditing process that incorporates PPP. The author discusses of the essence of managing for stakeholders value where we find that CSP can only be evaluated correctly by using quantitative assessment methods. Eskom’s integrated report succeeds in giving in depth information about its activities and the effort made to achieve a measurable CSP with current and historic reflections of the components of sustainability giving an indication of the corporations’ continuous commitment from top management to be sustainable Furthermore as the author discusses the corporate and employees’ responsibilities towards sustainability, it should be questioned whether everybody working at Eskom carries this commitment?

From this the question arises whether Eskom does have a responsible attitude towards the problems that it faces regarding the excessive CO2 emissions at KPS. An indication of the extent of this problem is only understandable when looking at the pressure on Eskom to deliver electricity to all its consumers and the possibility of load shedding if it does not employ all its resources to provide electricity to the national grid. The shortage of electricity supply capacity is seen from this statement, “International standards of a 15% surplus energy compared to only an 8% margin achieved by Eskom confirms that any problem in the grid might cause disruptions” ESKOM. surplus capacity. (2010). Today the situation is far worse. “In a statement to The New Age, Eskom spokesperson in the province Stefanie Jansen van Rensburg said the power system was currently severely constrained, meaning that any extra load or faults in the system would likely result in load shedding” Semela. (2014). These statements together with further more current news paints a picture of a critical situation in the power grid of South Africa and all Eskom’s’ resources are required to keep up with demand Crowley, Jansen van Rensburg (2014). Thus, it seems that although there is a serious problem with the planet (CO2 emissions) at KPS, there is also a responsibility towards the people to keep the lights on. Looking at this argument, the triple bottom line is not really affected only in a negative way as the negative point added to planet is countered with a positive to people by the commitment to keep the lights on. Let us keep in mind that KPS is only one of the sustainability issues for Eskom. By understanding this problem at KPS we can look deeper into this issue of exceeding the GHG emission limits and attempt to provide some answers to bring some relieve to the situation. As CO2 emissions is not only confined to KPS, these answers could be relevant to all coal-fired power stations employing cooling towers for their cold water needs

The author not only used his own knowledge but had contributions made from 35 knowledgeable people form a wide field of various universities and other institutions. Based on this broad spectrum of knowledge, the information provide in this book can be seen as accurate and usable. This information can help in the quest to understand the problems related to the sustainability issues at KPS and by providing answers to improve sustainability at KPS, it can lead to industry-improving solutions and these principles learned at KPS can be applied throughout the industry. It is clear that the sustainability factors at Eskom that need to be addressed are related to the objectives as seen by the Laasch (2013)

The question remains, will sustainable maintenance improve the triple bottom line?

Simply put; maintenance will improve the situation, and due to circumstances in the South African environment, where demand for electricity is greater than the supply, it is not possible to do maintenance at the regular required intervals. So, if at least some of the maintenance can be done


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on-line in a sustainable manner, can there be a positive impact on the triple bottom line at KPS?

IOL reported that Eskom spokesman said, “The lack of maintenance and refurbishment at power stations, because of the need to generate power in a crisis situation, has led to poor generation capacity” Cox, Flanagan (2014). This explanation also reveals a possible contributing factor to high CO2 emissions at KPS; a lack of regular maintenance to the cooling towers resulting in higher operating temperatures resulting in higher CO2 emission. Let us bear in mind that this problem of CO2 emissions from coal-fired power stations will not go away in the future and solutions must be found

Coal Industry Advisory Board (2008) reports; Coal-fired power generation is representing 42% of global electricity generated, with the availability of coal as a fuel source; this will not change in the foreseeable future. Growing concerns about the CO2 emissions from coal-fired power stations has placed an emphasis on more efficient operations from power stations. CO2 emissions are related to plant efficiency Figure 3. Plant efficiency is a complex combination of the components in the coal-fired electricity generation process pages 75 to 84 and cooling-water is one of the components directly related to the efficiency of the electricity generation process, thus the cooling towers and the maintenance there off is an important factor in the quest for efficiency Page 22 Figure 2.4. Page 25 shows the relation between cooling-water temperatures and condenser pressure Figure 4. Higher condenser pressure directly affects the efficiency of the electricity generation process and plant CO2 emissions. Maintenance of the cooling system is important to keep cooling-water temperatures low and furthermore, the cooling tower ponds must be kept clean to ensure clean process water to prevent fouling of condenser tubes that will result in higher process temperatures due to lower heat exchange through the condenser tubes where the fouling has caused build-up of scale on the tube walls or if the tubes are blocked by fouling resulting in lower water flow volumes. Coal Industry Advisory Board (2008) research and findings gives clear evidence that cooling towers are part of the chain that needs to be improved in the quest for achieving efficiency in coal-fired power plants.

Although coal-fired power stations worldwide represent only 42% of the electricity generated, in South Africa the picture is far worse as coal-fired power stations represent a much higher percentage with 13 out of 16 power stations in South Africa are using coal as a fuel source. Better plant efficiency at these power plants is thus more crucial to minimize the effect of GHG emissions in South Africa. From the information given by Coal Industry Advisory Board (2008) it is very clear that higher cooling-water temperatures will increases CO2 emissions and that by maintaining the cooling towers, lower cooling-water temperatures can be sustained. As a research report prepared for the G8 World Summit and with numerous references the information can be seen as accurate and used as a reputable source of information on CO2 emissions at power plants. Limitations on this paper is that it does not directly give information about maintenance procedures for cooling towers, it does however emphasize the importance of keeping cooling-water temperatures low for improving of plant efficiency resulting in a reduction of CO2 emissions from the coal-fired electric generation process. From Coal Industry Advisory Board (2008) it can be concluded that regular maintenance must be done on cooling towers to assist in maintaining plant efficiency and if solutions can be found to do on-line sustainable maintenance, it will be beneficial to the whole of the coal-fired electricity generation industry

The coal-fired electricity generation process is a conversion process of chemical energy to electric energy. In this cycle of fuel – heat –mechanical-energy – electric-energy, we find the answer to why the cooling towers are essential. Naijar (1979) provides evidence so that this process can be described as; the burning of fuel (in this case coal) that produces heat, this heat is then used to turn water (in a high pressure boiler) into steam. From the boiler the steam (at a high temperature and pressure) is fed to a turbine that is used to turn a generator that converts the mechanical energy into electric energy that is fed into the power grid supplying the end users with electricity. The steam used in the process completes its journey by entering into a condenser (heat exchanger) where the steam is cooled down, back to its original state of water and from there returns to the boiler to be heated again to begin the next cycle. This is a closed repetitive cycle. The cooling-water (a cooling tower in the case of KPS) is an external part of the process that is employed to cool down the condenser in the process of converting the steam back to water. Naijar (1979) gives a schematic layout of the process of steam-electric power generation shows the dual circuits of the water in the electric generation process Figure 5

KPS does employ natural draught cooling towers for the cooling-water needs of the power generation process, so although it seems irrelevant to look at the comparisons given by the author to the various sources for cooling-water, such as sea water, river water, open ponds and cooling towers, it must be


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understood that clean cold water is required in this process and as opposed to once through water (ocean or river water); cooling towers, that recirculates water, needs to be maintained to ensure the ongoing supply of cold clean water. Throughout the paper the author gives insight into the effect that the cooling-water will have on the performance of the steam electric generation plant. He gives an insight into the workings of natural draught cooling towers and discusses some of the environmental impact issues arising from natural draught cooling towers. The author explains the different options for cooling-water for electric generation plants and he analyses the performance of the various cooling-water options; which is relevant in the proof it provides of the importance of the cooling-water in the process of steam-electric generation plants and the effect of cooling-water on the plant efficiency, this is irrespective of where the water comes from or what the fuel sources for the power plant are, his research provides proof of the importance of maintaining a cold water supply to ensure the efficient operation of the plant. The study done was by the author in conjunction with various other people from Energy Laboratory and Ralph M. Parsons Laboratory under MIT supervision and it was done for the U.S. Department of Energy. It also gives a wide range of bibliography from reputable sources to give creditability to the information given and the evidence the paper provides

From Naijar (1979) it can be concluded that natural draught cooling towers used in the power generation process, must be kept in a well-maintained state to ensure efficient operation of the plant through the supply of clean cold cooling-water. The schematic layout showing the external nature of the cooling-water in the steam electric generation process allows the thoughts of the possibility of maintaining the cooling towers without interrupting the generation process. Thus sustainable on-line maintenance solutions for the cooling towers are possible

But what exactly needs to be maintained to improve the performance of the cooling towers? Randhire (2014) discuss the improvement of the performance of natural draught cooling towers and in the abstract he states that the improved cooling tower performance is the result of optimizing the mass flow rate of the cooling-water. He gives evidence that the process of heat transfer in the cooling tower is majorly through evaporation and that the balance of heat transfer is by convection. Thus, the air flowing through the cooling tower cools the water that is distributed throughout the cooling tower by a pipe and sprayer system. Due to the size of the cooling tower, the airflow volumes through the cooling tower are greater nearer the perimeter of the cooling tower and the core of the cooling tower receives the lesser volume of airflow. As the total airflow is fairly constant (atmospheric arguments set aside) it is the distribution of the water inside the cooling tower that can make an improvement to the efficiency of the cooling process inside the cooling tower where the heat transfer must take place. He provides evidence that with small changes to the distribution system more efficient cooling can be achieved. Taken into account that some factors are a constant, by altering the layout of the sprayer nozzle sizes of the distribution system, he optimizes the water-flow volumes in the different areas in relation to the available airflow in the corresponding areas and achieves an improvement of 7% or 1 degree Celsius at the outlet temperature Figure 6 and Figure 7

The objective of this paper is the improvement of the triple bottom line of the power station, thus an improvement of the cooling-water outlet temperatures as discussed by Randhire will make a positive impact on plant efficiency resulting in an improvement in many of the aspects of the triple bottom line. Now, let us think from an opposite direction. If a small change in the distribution system and sprayer configuration can make an improvement in the water cooling outlet temperature, just think what havoc a failing distribution system will cause. Randhire by careful manipulation of sprayer nozzle sizes achieved a 7% improvement, can we then not say, that if the distribution system is 25% blocked from lack of maintenance, the cooling efficiency will be much lower and outlet temperatures much higher?

If a small change for the good can make a big difference, then a lack of maintenance causing a negative impact on the distribution of the water in the cooling tower should be the last thing that can be allowed. But, as seen previously, the current state of affairs of the electricity supply in South Africa does not always allow timely and regular maintenance

But why will the distribution system get blocked? This is a bit of a vicious circle. As the hot water returning from the power plant is cooled down through evaporation in the cooling tower, only pure water evaporates in the process and it leaves behind dissolved solids that contaminate the water in the cooling tower. Evaporation is thus the cause of increased levels of dissolved solids in the cooling-water that is circulated through the condenser. This contaminated cooling-water is used and re-used for cooling the condenser and this recirculation of the water leads to scale build-up and corrosion in the condenser and pipe networks. In time the scale and corrosion scabs from this fouling breaks loose


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and through the water circulation process, these loose particles is carried to the cooling towers and will cause blockages in the sprayers of the distribution system. The pipes of the distribution system is also susceptible for build-up of scale and through time thick scale build-up will restrict the flow of water in these pipes. Hill (1967) investigated the problems related to the cooling water. Corrosion, fouling and the growth of bacteria. He explains the mechanics of heat transfer in a water droplet in the evaporation process and the resulted solids that is left behind in the water through this evaporation process. The various deposits left behind in the cooling-water accumulates in the cooling tower causing continuous fouling of the water. This dirty water is then used in the cooling process and this dirty water cause problems such as corrosion and the forming of scale in the pipes and equipment. An overview of cooling towers, what it is and how it works is clear from the study by the author. His research gives information regarding the problems related to the lack of maintenance to the cooling towers and what the expectations for cooling-water should be. As the objective of this paper is sustainable maintenance solution, a broad understanding of the basic working of cooling towers will help finding sustainable solution. This study has already had 3 editions printed, which implies that it contains valuable information and could be seen as reputable. The information gathered from the literature gives the insight to the basic function of a cooling tower and how it works. It lays the foundation for understanding the challenges involved in finding sustainable maintenance solutions for cooling towers but the limitations in this research is the lack of information on maintenance procedures

Scott (1995) further explains the fouling of cooling-water and discusses the cooling-water problems as experienced in the sugar industry. As cooling towers and cooling principles are similar irrespective of the industry, the problems he experienced such as corrosion is common to all cooling towers and water treatment to try and improve water quality is used widely used in all cooling-systems. He also concludes that frequent maintenance is required to ensure reliable operations. Monitoring of the water quality is required to have an idea of the extent of fouling to the water and when maintenance will be required. Cooling towers re-circulates cooling-water over and over. Build up of contaminants increases with each cycle and the water quality must be monitored, as this ever-increasing fouling will multiply the problems such as the blockages in the condensers. This is a common problem in any cooling tower irrespective of the industry. The author emphasizes the importance of monitoring and maintenance of cooling towers and actual facts from the mill have been used for research and were included to illustrate the effect of water fouling. This illustration of maintenance and monitoring of cooling water proves that regular maintenance can lead to prevention of untimely failures in the cooling system and loss of production. A regular maintenance program must be implemented Cooling towers is one of the major water consumers and South Africa is a water poor country. The majority of Eskom’s’ power stations use recirculate water for their cooling and the quantity of water used is related to the operating temperatures or efficiency of the generation process. Delgado, Hertzog (2012) has used Eskom to validate a model for water use. The author compares results obtained from Eskom, South Africa being a water scarce country, and states that Eskom has made efforts to minimize wasted water by not only using water-cooling but also dry-cooling and hybrid-cooling systems for the electricity generation plants The interdependency between cooling and energy generation is a constant factor but where the generation process becomes inefficient, it can lead to excessive use of water and thus the water-use by the industry will become a sustainability issue. The growing demand for energy and the scarcity of water in South Africa are both major sustainability concerns, as economic growth (the welfare of the people) will require additional electrical power (more cooling required) in the future to sustain growth in South Africa The demand for water in the electric generation process goes hand in hand with the heat that is generated from the process and a direct correlation exists between the two. As seen previously, electricity is generated from converting chemical energy to electric energy. Fuel – heat – mechanical – electricity. This would be simple enough if the process was 100% efficient. But it is not. The amount of heat required to generate one unit of electricity is far less than the heat generated in the conversion process, this is called the heat rate of the generation plant (HR, kj/kWh.) and this is an indication of the efficiency of the generation plant. Plant efficiency is mostly depended on fuel type and plant design. Thus, when plant efficiency is less than 100%, the balance of the heat that was required to produce one unit of electricity, must be dissipated else where and a great part of this dissipation of excess heat is achieved by heat rejection through the cooling system thus through the cooling towers using water as the medium for heat rejection. So, if a plant is only 50% efficient, then 50% of the heat


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generated by the fuel source must be dissipated elsewhere. The author explains that heat content of electricity is 3600kj/kWh and from information that Eskom supplied it is clear that the heat rate at the power stations are substantially higher that the heat content of electricity. By implication, lots of heat must be removed through the evaporative cooling system and large quantities of water are consumed during this process Delgado explains water consumption in a simplified manner that illustrates the relation between plant efficiency and water consumption. Using a mathematical equation, where the heat load is taken as a constant, the consumption of water can be calculated for the electricity generation process. In-depth information on the process of electricity generation and the related water consumption by the author is well referenced and done through MIT as part of an Energy Initiative The limitations of this literature are seen in the lack of considering the efficiency of the cooling system A study done by the European Commission IPPC (2001) confirms previous finding and in the light of their findings a guideline for the Best Available Techniques for maintaining cooling towers was done and published. Cooling systems are seen as auxiliary equipment to the actual production units. In this light we must understand that due to the auxiliary status of the cooling towers it is in many cases neglected. However, it does affect the generation of the electricity, as the generation process is reliant on cooling for efficiency and thus a very important component in the production cycle. The authors also shed a light on further problems related to cooling-water such as ambient weather conditions Water is used for rejection of process heat (cooling-water in the cooling system) but it not only receives heat from the process; it also receives other emissions such as water treatment additives, air-born substances entering through the cooling tower, corrosive product from corrosion in the systems equipment and some cases chemicals from leakages in the process plants. This fouling of the cooling water will cause slower heat transfer from the process to the water and leads to blockages in the cooling system. Furthermore, the cooling towers are also ideal environments for the growth of the legionella bacteria with water temperatures ranging between 25deg C. to 50deg C. and a PH between 6 and 8, the presence of fouling will promote the occurrence of the legionella bacteria The build-up of sludge due to water fouling (collected in the cooling pond) is also a major concern as the legionella and amoeba can be found in high concentration in the sludge. Actions to eliminate this build-up of sludge is important Preventative measures include

a. Avoiding stagnant areas in the cooling water ponds b. Prevention of algae and amoeba growth by the application of biocides to the water c. Regular cleaning of the distribution system d. Keeping the temperatures as low as possible e. Avoid scale build-up causing loose particles leading to blocked pipes f. Regular removal of sludge from the cooling-water ponds

The objective of European Commission IPPC (2001) was to find the Best Available Techniques for operating cooling towers. This BAT is in line with the objectives of this paper, in finding sustainable solutions for maintenance on the cooling towers. The authors’ provides an in-depth study to the problems related to cooling towers, giving substantial evidence and advises on the issues related to cooling towers and the maintenance thereof. As a prescribed BAT for the EU with numerous referencing and valid information is must be considered as important and reputable. Limitations of the document are seen by the lack of information on actual maintenance procedures

KPS is an existing plant, through maintenance and careful application of the recommendations as given in this BAT improvement to the condition of the cooling towers is possible. The dangers from fouled cooling towers are clearly seen in the evidence given and cooling tower fouling needs to be eliminated or minimized to the highest degree to counter the effects of the problems like legionella related to cooling towers

Through this literature it is also clear that the maintenance issues at hand is much further reaching than only production, it can kill people

Killing people is a dangerous statement. But it can happen in the event of employees working in the cooling towers or in the vicinity of the cooling towers contaminated by legionnaires bacterium


13

Legionella is not only water bound and can also be air-born to the areas surrounding the cooling towers, causing a widespread outbreak of legionnaires disease “SHE” is probably the most important word in today’s industrial environment. Eskom is committed to safety and will go to far reaching measures to ensure the safety of its employees. Srisawai (2000) discuss what legionella is, where it comes from and how it works. He also states that the fatality rate can be as high as 20%. He speaks of outbreaks that has occurred throughout the world and emphasize the danger of legionella. Australia has regulations regarding the prevention of legionella and there are statuary penalties from not complying It all comes back to regular maintenance Cooling towers are a perfect breeding ground for legionella. The aim of this paper is sustainability and people are our concern. Answers regarding a life-threatening disease coming from cooling towers are very relevant to what the aim of this paper is. Legionella must be prevented at all cost. Else it might be at the cost of human life. The author is from the Royal Irrigation Hospital in India and the document was accepted and published in the Journal of Health Science. Ample references are given to confirm the information given

If maintenance can prevent the loss of human life, then it should be of the highest priority

These concerns are clearly shared by others as can be seen from the Code of Practice for water systems. Health And Safety Executive (1999) in the UK gives a background on legionella and the paper describes the identification and assessment of the risks, managing the risks, responsibilities and implementation of a control scheme for legionella. It further gives guidance on the control of legionella and the managing, operation and maintenance of cooling towers Water treatment is of utmost importance in the control of legionella. Understanding the limitations of water treatment is just as important. Factors that can inhibit the effectiveness of the water treatment such as corrosion, scale formation, fouling and microbiological activity must be taken into consideration Water treatment such as biocides can kill the legionella bacteria, but it needs to reach the bacteria to be able to kill it. Fouling mostly congregates at the bottom of the cooling pond in a sludge layer and the bacteria living in this layer of sludge are very difficult to reach being embedded in the sludge and the sludge protecting the bacteria from biocides added to the water. Removing the sludge or stirring it will enable the biocides to reach the bacteria. Cleaning of the cooling towers is recommended at least once a year but preferably every six months. A further point to ponder is that legionella will grow in pipes where water does not flow. Fouling cause distribution pipes in a cooling tower to block, any of these blocked pipes can be the breeding ground for a legionella colony

Legionella is real. It kills people. We must understand where it comes from and how to eliminate it. This Code of Practice for Water Systems has been printed and reprinted over and over again to emphasize the importance of this issue. The UK government is doing their best to ensure everybody takes the necessary precautions. Seen previously that is also the case with Australia

Shouldn’t we all be doing the same?

Maintenance is important, without maintenance there can be no sustainability. Your house will fall to pieces, your car will stop running and your clothes will soil and turn to tatters. Just the same, your industrial process will cease to operate

Understandably, due to production schedules, it is not always possible to do maintenance when it is needed, maintenance must wait for a break in production. And if the demand, as in the case of Eskom, is overshadowing the production, then the maintenance will have to wait. Postponing maintenance will only lead to greater problems in the future. Finding a sustainable maintenance solution that enables maintenance while on-line will be to the benefit of all the stakeholders


14

4. METHODOLOGY 4.1. ESKOM SUSTAINABLE BUSINESS PRACTICES Looking at Eskom as a corporation, what is the top managements attitude towards sustainability? A well-documented sustainable business practice assurance is published. Top management is committed to sustainable development Figure 1, Figure 2 Further gathering information regarding the current state of affairs from the media, we find various reports and some statements from Eskom spokespeople that at some power stations sustainability proves to be a problem Bothma (2013), Cox, Flanagan (2014), Crowley, Janse van Rensburg (2014), Semela (2014), Zunckei, Raghunandan (2013) We must consider that in many instances, it might be in-activity in areas of importance that causes sustainabillity problems rather than the attempts at some activities in general to promote sustainability From Eskom’s 2014 year-end integrated report we see that maintenance, the key to sustainability, has taken a back seat in the light of the demand on the power grid “Previously, Eskom had no choice but to defer power station maintenance in order to keep the lights on, which was not a sustainable approach. At the end of 2012, Eskom’s board approved the Generation sustainability strategy. The plan spans five years, with 2013/14 being the first full year that the plan has been in place. The “keeping the lights on” strategy now also includes managing the demand such that the Generation sustainability strategy can be achieved, while avoiding rotational load shedding, as well as tracking the status of reduction in the maintenance backlog”. Eskom integrated report. (2014) Concerns about responsible business logic was first discussed in 1927, “Wallace Donham prophetically warned that “civilization may well head for one of its periods of decline” if business leaders do not “ learn to exercise their powers and responsibilities with…. responsibility towards other groups in the community”. The great depression came only two years afterwards. History repeats itself. CSR was a buzzword and peak topic right before the economic crisis triggered by the use of subprime loans in 2009. Has business not learned anything about taking responsibility throughout the last century? “ Laasch, Conaway. (2013). Learning from history, CSR should be on the high priority list of every major corporation in the world and also the implementation of a measurable triple bottom line that can act as a watchdog to ensure that CSR is not use as a tool for green washing. According to Chris Adam the drive to a triple bottom line is also fuelled by the awareness of the community to social and environmental issues by high profile incidents covered by the media such as the Shell oilrig disaster. Adam, C. (2000) In the case of ESKOM, demand for electrical power in South Africa has led to firstly the inability to do the required maintenance on time every time and secondly to the deferred upgrading of power plants that is required to reduce the CO2 emissions of the power plants to bring these power plants to within the legal GHG emission limits as required by law Is it possible to find some relieve through sustainable on-line maintenance practices in some aspects of sustainability?


15

4.2. SUSTAINABLE MAINTENANCE FOR POWER STATION COOLING TOWERS For this paper a case study done at the Kriel Power Station in South Africa will be used for collecting of data as a project to implement sustainable on-line maintenance solutions on the cooling towers has been done by KPS Eskom, Kriel Power Station, Stock photo, Kriel Power Station Methodology to measure the impact on sustainability through the maintenance process of the cooling towers, is firstly to collect data to find out what is the role that cooling towers play in the power station and then to look at the specifics of maintenance on the cooling towers, our objective being to prove that sustainable on-line maintenance on the cooling towers can improve overall sustainability at power stations. From the illustration below we can see the integrated role of the cooling towers at a power station Figure 8 Illustration of the power generation process equipment

Organic Rankine Cycle - CARE Transenergy (2014) Initial investigation gathering information regarding the role that cooling towers play in the power generation process, was done by researching existing literatures to provide an overall picture of the power generation process as can be seen in schematic layout of the steam-electric power plant Figure 5 The cooling towers at a power station are auxiliary equipment but still a key component of the electricity generation process IPPC(2001). This said, being a key component, if better sustainability in the cooling towers is achieved, that is “to be able to use without being completely used up or destroyed” Miriam-Webster dictionary, it can be assumed that the overall sustainability of the power station can be improved As the cooling towers are designed to operate at an optimum cooling capacity to serve the designed cooling needs of the electricity generation plant Kroger, Detlev(2004), then maintaining the cooling towers is critical to sustain the cooling capacity of the cooling towers. Variation in cooling-water temperatures will affect the efficiency of the electricity generation process. There is a direct correlation between

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cooling-water temperature and condenser pressure Figure 4. Condenser pressure again has a direct influence on the generation plant efficiency and by keeping the temperatures of the cooling-water low will result in better generation plant efficiency COAL INDUSTRY ADVISORY BOARD (2008) To simplify the overall picture of the function of the cooling towers and its influence on the generation process we can look at the following diagram that illustrates to us the heat-liquid cycle of the electricity generation process of a coal-fired power station. The heat required to generate electrical power will only used a percentage of the heat that comes from the fuel source. The excess heat must be removed through the condenser to keep the heat-liquid cycle of the process in a balance Figure 9 Heat-liquid cycle in coal-fired power generation

Waste Heat Recovery, Power Generation, Organic Rankine Cycle . 2014. Waste Heat Recovery, Power Generation, Organic Rankine Cycle This heat-liquid cycle is regulated by the hear rate (HR) of the power generation plant and to understand the heat cycle, the diagram below, we find that from the total heat-input only a certain percentage is used for electricity generation and the balance of the heat generated by the fuel source is dispersed through the cooling system (As KPS is not equipped with a flue gas system and the “other” is insignificant small, we will ignore “B” for the moment) Figure 10 Heat Balance of coal-fired power generation

Delgado, A. Hertzog, H J. (2012). A simple model to help understand water use at power plants. Working paper. See references

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page 3

Figure 2. Simplified Visualization of Heat Balance of a Power Plant

Parameter B is determined from the overall heat balance of the power plant (see Figure 2) and represents

all heat flows out of the power plant except the heat flows to cooling water. The amount of heat that is

rejected to the cooling water system is simply HR-B. Parameter A represents the water needed per unit of

energy rejected through the cooling water (L/kJ). It will depend on the type of cooling system (e.g., once-

through, wet cooling, dry cooling, etc.). Parameter C represents the water used in other processes not

related to cooling. Thus, the total amount of water required in the power plant (I) depends on the amount

of heat to be dissipated through the cooling system (HR-B), the type of cooling system (A) and the water

needs of the other processes in the plant (C).

These parameters are discussed in more detail below.

3.1 Parameter B: Heat dissipated through other mechanisms than the cooling system

The major heat flows occur in streams leaving the power plant (e.g., electricity, flue gas, etc). In addition,

heat losses account for 3% to 5% of the total energy input depending on the type of power plant [10] [11].

These include steam turbine heat losses, generator heat losses, radiation losses, etc.; most of the processes

in the power plant dissipate small amounts of heat into the environment.

The streams leaving the power plant can be classified into three categories: electricity, flue gas and other

streams. Electricity, by definition, accounts for 3,600 kJ/kWh. “Other streams” includes small streams

such as slag and sulfur, which carry some heat to the environment [10]. However, these streams are

negligible compared to the overall energy balance. On the other hand, the flue gas is typically a

significant stream for combustion-based plants. The flue gas from the combustion of fossil fuel and/or


17

To illustrate the effect that the cooling tower has on this process, a hypothetical scenario of this heat-liquid cycle is sketched where the electric generation efficiency of the power plant is taken at 50% efficiency. Thus, the generation of electricity uses 50% of the heat generated by the fuel source, the cooling tower has to removes the remaining 50% of the heat from this heat-liquid cycle and if this is the case then a 100% balanced heat-liquid cycle will exist (All other factors are taken as a constant, we are only interested in the influence the cooling towers have on the generation process.) Figure 11 Hypothetical heat balance diagram for coal-fired power station

But this is in a perfect world where the cooling tower operates at optimum designed efficiency. What will happen when the cooling towers are not functioning at optimum? When a lack of maintenance has caused inefficient cooling by the cooling towers? For illustration purposes, comparable graphs was created using the hypothetical scenario to show the effect that declining cooling system efficiency will have on the electricity generation process output The first graph illustrates 100% cooling system efficiency Result: Zero losses occur in the electricity generation process Graph 2 reflects an 80% cooling system efficiency Result: A 20% drop in the electricity generation capacity of the power plant Graph 3 reflects a 60% cooling system efficiency

Result: The electricity generation capacity of the plant has declined severely and the heat retained in the heat-cycle is even greater than the rejected heat that is dissipated through the cooling system Not only will this drop in efficiency effect generation output, the retained heat in the generation plant can cause further problems such as high operation temperatures the generation equipment such as the turbine bearings that can and will lead to excessive wear and bearing failure in the turbines causing massive damage to the generation equipment

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18

Figure 12 Hypothetical relationship between heat used in generation and heat rejection to cooling towers

From this hypothetical scenario we can see a clear indication of the direct correlation between electricity generation output and cooling-water temperature in a coal-fired power plant This argument is further substantiated through the Carnot efficiency formula Coal industry advisory board (2008), Randhire (2014), Hill (1967). The thermal efficiency of the heat-liquid cycle declines directly related to the increase of the cooling-water temperature in the heat-liquid cycle Figure 13 Carnot thermal efficiency of the liquid cycle in power generation

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Electricity generation efficiency will determine the electricity available to feed the power grid taking the electricity to the end-user and thus relates to the income that is generated from this process. This has a direct affect on the profits of the power station. It also relates to the volume of green house gases released through the coal-fired generation process having an effect on the carbon footprint of the power station. Furthermore, the volume of water consumed by the plant will increase when the temperatures are higher and in a water scares environment this wasted water can have a negative effect on the wellbeing of the community around the power station who needs water for survival every day. In conclusion, the cooling towers do have a direct impact on profits, planet and people Sustainability of the current maintenance practices can be measured in terms of financial cost, the effect on a healthy working environment, volume of water lost and CO2 emissions As the maintenance of the cooling towers at a power station directly influences the above, these issues must be measured, addressed and possibilities for improved sustainable maintenance solutions must be identified and implemented


20

A. Measurability of the current maintenance practices on cooling towers The cost of maintenance is not merely buying a few spares, doing some repairs and the service of a component somewhere along the line of the electric generation process To enable a maintenance exercise, the electricity generation process must be stopped to enable safe access to the component that needs maintenance, repairs or service. Stopping the process leads to production losses. Loss of electricity production goes hand in hand with the loss of income and in the case of electricity generation this amounts to large sums of money lost In the case of KPS, at least two electricity generation units needs to be shut down to enable the maintenance on a single cooling tower. This halting of generating power for maintenance on a single cooling tower has a high impact on the income of KPS However, the outages at KPS usually arrange, called a half station outage, are for three electricity generation units to be taken out of production at the same time and then enabling maintenance work on two cooling towers during the outage period

Notes 1. An outage to do maintenance on the cooling towers is usually scheduled for about a period of about 10 days

Interview with Mathebebe (2014) 2. The cooling towers are scheduled for maintenance every two years. A half station outage is arrange each year during the festive

season when the demand on electricity is lower. Thus each pair of cooling towers gets the window of opportunity for maintenance every alternating year Interview with Mathebebe (2014)

The impact of these half-station outages can be measured for profit, planet and people 1. Profit

Profitability is the main concern for most enterprises and the key to sustaining the enterprise As the maintenance of the cooling towers is a cost factor that must be brought into the calculation of the profit/loss bottom-line, any savings achieved on this expense will improve the profit/loss bottom line. According to literature, optimizing the temperature of cooling water is one off the most efficient ways of reducing operating costs. Savings of up to 15% is possible Liptak (1987) It must further also be acknowledged that the extent of the financial implications of maintenance, or the lack of maintenance, goes further than just the actual project cost of maintenance Cost factors that needs to be considered, the direct and in-direct factors i. Project cost for maintenance The direct cost for the maintenance on a cooling tower as shown is ignoring the spares that might be required during maintenance as this will be equal regardless of the method used for maintenance Costs as shown is for a single cooling tower and may vary depending on circumstances and the scope of work to be done. Cost used in this document is estimated costs supplied by Wasser Cooling Towers for maintenance on the distribution systems and cleaning of the cooling pond of a cooling tower


21

Figure 14 Estimated maintenance cost for a cooling tower

Information supplied by Wasser Cooling Towers. Kenny (2014)

ii. Loss of income during maintenance For maintenance to be done on a cooling tower an electric generation unit must be shut down, the half-station outage. Outages for maintaining the cooling towers are usually scheduled in conjunction with other maintenance projects to save on the costs and minimized the effect of the financial loss during an outage. Looking at the greater picture, a 20% cost contribution can be allocated to the cooling towers The cost reflected is for a half station outage scheduled annually. Cost shown is for a single cooling tower

Figure 15 Potential loss of income contributed to cooling towers during an outage

Table A. Eskom. Kriel power station technical date iii. Lower income from reduced production due to higher operating temperatures

caused by extended maintenance schedules In an energy hungry economy and a constant high demand of electricity, the scheduled outages are dragged out to the maximum intervals between the outages, which lead to a lack of, or rather insufficient maintenance on the cooling towers. This is a major concern as a lack of maintenance will lead to higher temperatures in the cooling towers after a period following maintenance due to blocked or partially blocked distribution systems and dirt/sludge build up in the cooling ponds which can lead to various problems such as reduced water flow in the condensers and fouling of pipes. “As air circulates through the cooling tower, it carries solids in

Spares'required not'applicable

Supervision'from'Eskom R30'000,00

Contractors'price'(based'on'historic'tender'prices) R791'466,00

Utility'power'and'water'suppllied R25'000,00

Loss'contributed'to'one'cooling'tower R846'466,00

Kriel&Power&StationMaintenance&cost

Direct&cost&of&maintenance&of&a&cooling&tower

Number'of'units'down'during'outage 3'units

Total'work'rate'of'turbine'train' 513,1'MW'

Total'production'capacity 1539,3MW

Efficiency'of'units 98,15%

Lost'production 1510,8'MW

Weighted'average'selling'price R218,20

Number'of'days'lost 10

Total'loss'of'income'during'outage R79'118'776,25

20%'of'loss'alucated'to'cooling'towers R15'823'755,25

No'of'cooling'towers'on'outage 2

Loss'contributed'to'one'cooling'tower R7'911'877,62

Kriel&Power&StationMaintenance&cost

Loss&of&income&during&an&outage


22

the form of small dust particles. These solids are captured by the downward flow of the water and collected in the catch basin where they form sludge. Sludge is removed through the blow down system. Suspended solids can build-up inside the tubes of a heat exchanger and cause fouling” Thomas (2011). These resulted higher temperatures cause a decline to the production capacity of the electric generation units as these units are designed to operate optimally at a certain temperature Micheletti, Burns (2002). Thus, production and temperature will follow a curve where higher temperatures cause lower production Vosough, et al (2011) Efficiency changes of the cooling system are further sensitive dependant on the local ambient temperatures. At around 0 degree Celsius ambient temperature, a 1 degree Celsius increase in cooling-water temperature can reduce electricity generation output by between 0,5% and 1,0%, and around an ambient temperature of 15 degree Celsius the reduction of generation output will be between 1% and 2% Linnerud et al (2009) Kriel has a yearly mean ambient temperature of between 8 degrees Celsius and 20 degree Celsius Figure 16. Thus, using a 1,5% electricity generation output decrease per degree Celsius increase in cooling-water temperature for a hypothetical estimate will give a fair understanding of these generation losses, the graph illustrates the relationship between cooling–water temperature and electricity generation output Figure 17 Relationship between cooling-water temperatures and generation output

In this case, as electricity is the product, a lower generation output means less electrical units (MwH) that can be sold. In monetary terms each electric unit lost is a loss of R 218,20 Figure 18 and Figure 19 Over a period of a month this can grow into significant sums of money lost. The table below is an indication of the cost of lost production in relation with cooling-water temperature Calculations done is representing the output of a single 500MW electricity generation unit Figure 20 Relationship between cooling-water temperatures and loss of income

Cooling Toweroutlet watertemperature

Generation1unit outputMW at1,5%1decrease

As a % of thedesigned1output

MW lostdue todecrease inefficiency

Variation inoperating1temperature1(1deg1C1)

Possible1production1rate

Lost1production1MW

Monthly Incomelost

251deg1C 500,001111111 97,47% 13,0011111111111 0 100,00% L111111111111111 R0,00261deg1C 492,501111111 96,00% 20,5011111111111 1 98,50% 7,501111111111111 R111781271,36271deg1C 485,111111111 94,56% 27,8911111111111 2 97,02% 14,891111111111 R213381868,65281deg1C 477,841111111 93,15% 35,1611111111111 3 95,57% 22,161111111111 R314821056,98291deg1C 470,671111111 91,75% 42,3311111111111 4 94,13% 29,331111111111 R416081097,49301deg1C 463,611111111 90,37% 49,3911111111111 5 92,72% 36,391111111111 R517171247,38311deg1C 456,651111111 89,02% 56,3511111111111 6 91,33% 43,351111111111 R618091760,03321deg1C 449,801111111 87,68% 63,2011111111111 7 89,96% 50,201111111111 R718851884,99

Kriel&Power&StationRelationship&between&temperature&and&the&cost&of&lost&production

1440,0011

1450,0011

1460,0011

1470,0011

1480,0011

1490,0011

1500,0011

1510,0011

251deg1C1 261deg1C1 271deg1C1 281deg1C1 291deg1C1 301deg1C1 311deg1C1 321deg1C1

Output&MW&

Output1MW1

Cooling Toweroutlet watertemperature

Generation1unit outputMW at1,5%1decrease

As a % of thedesigned1output

MW lostdue todecrease inefficiency

Variation inoperating1temperature1(1deg1C1)

Possible1production1rate

Lost1production1MW

Monthly Incomelost

251deg1C 500,001111111 97,47% 13,0011111111111 0 100,00% L111111111111111 R0,00261deg1C 492,501111111 96,00% 20,5011111111111 1 98,50% 7,501111111111111 R111781271,36271deg1C 485,111111111 94,56% 27,8911111111111 2 97,02% 14,891111111111 R213381868,65281deg1C 477,841111111 93,15% 35,1611111111111 3 95,57% 22,161111111111 R314821056,98291deg1C 470,671111111 91,75% 42,3311111111111 4 94,13% 29,331111111111 R416081097,49301deg1C 463,611111111 90,37% 49,3911111111111 5 92,72% 36,391111111111 R517171247,38311deg1C 456,651111111 89,02% 56,3511111111111 6 91,33% 43,351111111111 R618091760,03321deg1C 449,801111111 87,68% 63,2011111111111 7 89,96% 50,201111111111 R718851884,99

Kriel&Power&StationRelationship&between&temperature&and&the&cost&of&lost&production

1440,0011

1450,0011

1460,0011

1470,0011

1480,0011

1490,0011

1500,0011

1510,0011

251deg1C1 261deg1C1 271deg1C1 281deg1C1 291deg1C1 301deg1C1 311deg1C1 321deg1C1

Output&MW&

Output1MW1


23

With two-yearly maintenance schedules it can be expected that the cooling-water temperature will remain relative low for several months and then have a gradual rise in temperature as the fouling in the cooling tower increases. This increased fouling is the cause of partially blocked distribution systems and build-up of sludge that accumulates in the cooling tower pond After the cooling towers at KPS have been serviced during the outage the temperatures will be close to designed temperatures and will sustain that temperatures for several months. From on-site data it shows an increase in water temperatures from the 8th month on and reaching a sustained peak from the 12th month onwards. The temperatures will only drop again after the following two-yearly scheduled maintenance has been done Temperatures as shown below reflect a two-year trend of the rising cooling-water temperatures after the maintenance has been done on the cooling towers

Figure 21 Relationship between cooling-water temperatures of serviced and un-serviced cooling towers

On-site data provided by Wasser Cooling Towers. McGillivray (2014) To simplify this argument, if your car’s radiator is partially blocked from dirt in the engine, it will cause reduced flow of water through the radiator reducing the efficiency of your car’s cooling system leading to overheating of the engine at full performance due to the blocked/dirty radiator, thus with a reduced cooling system the performance will be limited, you will have to drive very slowly or risk damage to the motor. Thus, at a power station we can expect that from more regular maintenance to keep the cooling towers clean, the power station will be able to achieve higher generation performance and a higher income due to increased productivity made possible by sustained lower temperatures by well maintained cooling systems for the electric generation plant

Month

Cooling towers serviced duringoutage3(deg3C3)

Cooling Towers not servicedduring3this3outage3(deg3C3)

Temperature difference (deg C)

1 26 32 62 26 32 63 26 33 74 27 34 75 26 32 66 25 31 67 26 30 48 27 30 39 29 31 210 29 32 311 31 33 212 32 33 1

Water3temp3in3feed3pipe3to3generation3units

Kriel&Power&StationMonthly3average3water3temperature

Starting3at3the3month3following3an3outage3where3cooling3towers3were3service


24

2. Planet i. WATER Cooling towers are one of the highest water-consuming culprits in the industrial world. From Figure 22 below we can see that thermo-electric plants are one off the greatest users of water and it is important to minimize to quantity of water consumed. Saving of water can be achieved through maintenance keeping the operating temperature as low as possible, or the opposite is also true, wasted water can be caused through the lack of regular maintenance of the cooling towers Figure 22 Water consumption by economic sector

Feeley et al. (2005) Department of energy/office of fossil energy’s water management R&D program. See references South Africa has already reached a point where water is a scarce commodity Earle (2005) and it has been predicted that by 2020 there will be a shortage of water in South Africa Naido-Hoffmeester (2014). It has already reached a point where water supply needs to be managed to balance the supply and demand Banda et al (2007) The volume of water going to waste during the maintenance process is calculable and it is sufficient to sustain a large number of families for a period Figure 23 a. Water disposed of during outage

To enable maintenance to the cooling tower and gain access to the cooling ponds for the maintenance process of a cooling tower, the water is drained from the cooling pond by pumps. Also the water from the feeder pipes is drained in the same time to allow access to the cooling tower pond to do maintenance This might be a controversial argument as the water is pumped to the ash-ponds or sediment dams for possible re-use, but this water is still lost for human consumption and water from potable sources is used for the make-up water for the cooling-water needs of the power station. The monetary value of the water can also be argued but as we are looking at the effect of this lost water on people, the cost of water used for this argument is the price that the people must pay for their household water Volumes of water calculated is for the maintenance on one cooling tower

BACKGROUND

Water Use for Thermoelectric Power Generation Thermoelectric generation represents the largest segment of U.S. electricity production and coal-based power plants alone generate more than half of the nation’s electricity supply. According to USGS water use survey data, 346 billion gallons of freshwater per day (BGD) was used in the United States in 2000. Figure 1 presents the percentage of total U.S. freshwater withdrawal by source category. Thermoelectric generation accounted for 39% (136 BGD) of all freshwater withdrawals in the nation in 2000, second only to irrigation. Each kWh of thermoelectric generation requires approximately 25 gallons of waterd, primarily used for cooling purposes – a 500 MW power plant would use approximately 300 million gallons of water per day. However, power plants also use water for operation of pollution control devices such as flue gas desulfurization (FGD) technology as well as for ash handling, wastewater treatment, and wash water. When discussing water and thermoelectric generation, it is important to distinguish between water use and water consumption. Water use represents the total water withdrawal from a source and water consumption represents the amount of that withdrawal that is not returned to the source. Although thermoelectric generation is the second largest user of water on a withdrawal basis, it was only responsible for about 3% of the total of 100 BGD freshwater consumed in 1995 compared to 81% for irrigation as shown in Figure 2.3 Figure 1 – U.S. Freshwater Withdrawal (2000 ) Figure 2 – U.S. Freshwater Consumption (1995)

Freshwater Withdrawal by Sector

Thermoelectric39%

Public Supply13%

Aquaculture1%

Industrial5%

Mining1%

Livestock1%

Irrigation40%

Domestic1%

Freshwater Consumption by Sector

Commercial1%

Domestic7%

Irrigation81%

Livestock3%

Thermoelectric3%

Mining1%

Industrial3%

As discussed above, large quantities of cooling water are required for thermoelectric power plants to support the generation of electricity. Thermoelectric generation relies on a fuel source (fossil or nuclear) to heat water to steam that is used to drive a turbine-generator. Steam exhausted from the turbine is condensed and recycled to the steam

2 DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005

d This number is a weighted average that captures total thermoelectric water withdrawals and generation for both once-through and recirculating cooling systems.


25

Figure 24 Quantity of water lost during maintenance on a cooling tower

b. Evaporation of water A further concern from a lack of regular maintenance is the loss of cooling efficiency that progressively leads to higher than designed temperatures that cause excessive evaporation due to higher water temperatures during the generation process, this leads to even more water losses. The excessive loss of water due to evaporation can be calculated and quantified “An average of 1,6 -2,5 litres of cooling water will be required for cooling per kWh (e) of net generation“ Kroger (2004). That is a variation of 36% of water consumed. From Figure 25 we can see that the consumptions of water by the power stations in South Africa vary between 1,819 and 2,327 litres of cooling-water per kWh with a corresponding cooling system efficiency of η(cc) 39 and η(cc) 20 The latent heat of evaporation of water is 2270 kj/kg Water Properties (2014). Heat rejection through evaporation is thus a fixed equation where 1000kj of heat is dissipated for every 0,440 litres of water evaporated. It can thus be said that if all other factors are taken as a constant, then better plant efficiency resulting in lower operating temperatures will improve the water consumption by the evaporative cooling process Cost calculation done for a single cooling tower Figure 26 Efficiency related water losses

Diameter 85*********************** mDepth*of*water 2************************* mTotal*volume*in*pond 11*353*571******** liters

Pipe*diameter 2,5 mPipe*length 100********************* mVolume*of*water*in*pipe 491*071************* liters

Total&water&lost&during&outage 11&844&643&&&&&&&& liters

Cooling&tower&pondVolume&of&water&disposed&of&during&outage

Water&in&pipe&lines

Cooling'system'efficiencyη(cc) 20 1,819 lt'per'kWh 3'732'588''''''''''''''' litersη(cc) 39 2,327 lt'per'kWh 4'775'004''''''''''''''' liters

Water'lost'due'to'efficiency 1'042'416''''''''''''''' liters

Increase'in'water'consumption 28%The'rated'2001'capacity'for'KPS'was'used'to'caculated'water'volumes'(TABLE'A)

Water comsumption inrelation'to'efficiency

Eskom&Power&StationsWater&losses&related&to&efficiency

Water comsumed over aone'month'period


26

ii. CO2 EMISSIONS CO2 emissions at KPS are at a critical level and the existence of the power station is threatened. Taking into consideration that CO2 emission is a global problem and power stations are one of the main culprits “Coal produces almost three-quarters of the 40% of energy-related CO2 emissions that comes from the generation of electricity. Reducing CO2 emissions from coal-fired electricity generation would have a significant impact on global emissions and, therefore, on climate change.” International energy agency (2012) it is clear that finding a solution to improve the level of CO2 emission at power stations are an important consideration at all coal-fired power stations and this problem is not present only at KPS At KPS the improvement of process efficiency to reduce CO2 emissions should be on the highest priority list and if keeping the temperatures of the cooling-water as low as possible can give any level of relieve then maintenance of the cooling towers should be on the same priority level. “Increases in the efficiency of electricity generation are essential in tackling climate change. A one percentage point improvement in the efficiency of a conventional pulverized coal combustion plant results in a 2-3% reduction in CO2 emissions.” World Coal Association (2014)

Figure 27 Relationship between CO2 emissions and plant efficiency of a coal-fired generation plant

Campbell. Richard J. (2013). Increasing the Efficiency of Existing Coal- Fired Power Plants. See references

Increasing the Efficiency of Existing Coal-Fired Power Plants

Congressional Research Service 10

Figure 5. Carbon Dioxide Emissions vs. Net Plant Efficiency Based on Burning Pittsburgh #8 (Bituminous) Coal

Source: Booras, G. and N. Holt, Pulverized Coal and IGCC plant Cost and Performance Estimates, Gasification Technologies Conference Washington D.C. 2004.

Notes:

1) One tonne (also known as a metric ton) is a unit of mass equaling 1,000 kilograms.

2) This chart assumes subcritical plants (using bituminous coal) would be near the top of the range for efficiency. Improvements at the higher end of the range are now considered to be based on advanced ultrasupercritical technology, which while technologically possible, is unlikely to be implemented in the next few years.

Efficiency Improvements to Reduce GHG Emissions The overall efficiency of a power plant encompasses the efficiency of the various components of a particular generating unit. Sometimes these systems are unique to a generating unit, while in other instances these systems may be shared between generating units at a power plant site. This section will summarize the results of several U.S. and international studies which present options for improvements to power plant systems capable of increasing system heat rate efficiency and reducing GHG emissions. While the focus of this report is improving the efficiency of U.S. coal-fired power plants, studies from the international community are also presented as suggested improvements apply generally to coal-fired power plants. Further, a key report from an Asia-Pacific Economic Cooperation (APEC) working group report laid the groundwork for several U.S and international studies. (...continued) August 2013, http://www.iea-coal.org.uk/documents/83185/8784/Upgrading-and-efficiency-improvement-in-coal-fired-power-plants,-CCC/221.


27

3. People Cooling towers are by nature a collection point for dust, dirt and all impurities in the air that passes through the cooling tower Sinha Parameswar (2012). The collection of these impurities results in the build-up of sludge in the cooling-water. This sludge creates a natural breeding ground for various algae and other undesirable organism such as protozoa, which can sustain the growth of legionnaires bacteria commonly known as legionella. “The bacteria require nutrients such as algae or dead algae in sludge… “ Mills (1995) and “In USA and Europe, poorly maintained cooling towers have been implicated in many outbreaks of this disease” Srisawai (2000). Levels of legionella measured in CFU can be checked in the cooling towers at various stages of maintenance. In extended periods between the maintenance of the cooling towers, a much more ideal breeding ground is created for legionella in the blocked or partially blocked distribution pipes and in the layer of dirt/sludge building up in the bottom of the cooling ponds. If unchecked this bacteria can spread throughout the water system and infection of the workers at the power station is possible. The greatest danger lies with the workers doing maintenance on the cooling towers after an extended period of none maintenance where legionella has had time to grow and proliferate in the cooling towers. Regular maintenance is an important factor to eliminate the growth of legionella in cooling towers. It must be noted that tests for the presence of legionella in done by water sampling and the most dangerous areas where the legionella might be present, in blocked pipes and contained in the layer of sludge, will not be accessed by these water tests. It is quite possible to have a report of good results whilst having an infestation of legionella bacteria at the same time At KPS it was found that a substantial increase in the legionella bacteria was measured after some of the distribution pipes of the cooling tower was cleaned, and during the process of removal of sludge from the cooling tower pond Figure 28. This is a clear confirmation that breeding colonies of legionella bacteria proliferate in dead zones of the cooling tower Only with regular maintenance can this be prevented


28

B. Measurability of sustainable maintenance of cooling towers KPS has undertaken a project to do on-line maintenance on some of the cooling towers As high cooling-water temperature has become a critical problem and no possibility for an outage was foreseen for the near future, the option for doing on-line sustainable maintenance was opted for as an alternative The effect that the sustainable maintenance work had on the cooling water temperatures can be seen in Figure 29 and is reflected in the following graph. Figure 30 On-site cooling-water temperatures taken during a sustainable maintenance project

On-site data as recorded by Wasser Cooling Towers. McGillivray (2014) At the beginning of the project the cooling-water temperatures in relation with the ambient temperatures showed at difference of around 9 degrees Celsius and an improvement was seen gradually throughout the contract period to the point where the cooling-water and ambient temperatures nearly converge towards the end of the project. A clear indication of the improved efficiency to the cooling system that can be achieved through on-line sustainable maintenance This downward trend in the cooling-water temperature was confirmed by data received from the power station for the corresponding period as can be seen from the condenser in-let cooling–water temperatures Figure 31 reflecting similar trends as the on-site data in Figure 30 Figure 31 Actual data from KPS for the combined condenser in-let temperatures of CT 3 and CT 4

Data supplied by KPS Auxiliary Engineering. Mathibebe (2014)

Date%recorded Water%temperature Ambient%temperature Differential296Sep 37 21,1 15,9306Sep 32 25,6 6,4016Oct 31 21,9 9,1026Oct 37 23,1 13,9036Oct 29 19 10066Oct 29 26,1 2,9076Oct 29 26,9 2,1086Oct 30 29,1 0,9096Oct 29 30 61106Oct 29 22,4 6,6136Oct 29 19,1 9,9146Oct 29 26,1 2,9156Oct 27 20,8 6,2166Oct 27 23,8 3,2176Oct 29 18,5 10,5206Oct 24 18,3 5,7216Oct 28 28,8 60,8226Oct 29 26 3236Oct 28 24 4246Oct 25 29,1 64,1276Oct 24 21,8 2,2286Oct 26 26,6 60,6296Oct 26 28,4 62,4306Oct 26 28,7 62,7316Oct 26 27,4 61,4036Nov 26 26 0046Nov 27 20,4 6,6056Nov 23 24,5 61,5066Nov 23 25,3 62,3076Nov 23 26,1 63,1036Jan 25 18,8 6,2046Jan 25 25,2 60,2056Jan 22 23 61066Jan 25 24,3 0,7076Jan 24 21,5 2,5

Temperatures*taken*during*the*sustainable*maintenance*project

15%

17%

19%

21%

23%

25%

27%

29%

31%

33%

35%

37%

39%

1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 16% 17% 18% 19% 20% 21% 22% 23% 24% 25% 26% 27% 28% 29% 30% 31% 32% 33% 34% 35%

Daily%temperatures%as%measured%

Ambient%


29

1. Profit The impact of sustainable on-line maintenance on the cost / income equation at KPS i. Project cost for a sustainable on-line maintenance project

The cost reflected is for the cleaning of the distribution system and partial removal of the sludge accumulated in the pond Cost shown are the actual project cost for cleaning of the distribution system and removal of sludge for a single cooling tower Figure 32 Estimated cost of sustainable maintenance on a cooling tower

Information supplied by Wasser Cooling Towers. Kenny (2014)

According to the contractor, due to operational limitations while working on-line in the cooling-water pond, it will only be possible to remove the majority of the sludge if the cleaning of the pond has undergone three cycles of the cleaning process. Due to economic and time issues a single sweep of the pond is done during a sustainable on-line maintenance project. This single sweep of the pond will only remove an estimated 50% of the sludge but the improvement achieved through this single sweep is sufficient to achieve acceptable levels of sludge for the operation of the cooling system for a year

ii. Loss of income during sustainable maintenance project

As the work was done on-line while the generation process was on going, there was no loss in production during the contract period that could be related to the sustainable maintenance project

iii. Impact on operational income forthcoming from the sustainable maintenance project

Throughout the project duration an improvement of the cooling-water temperatures could be measured Figure 29. The end results of the cooling-water temperatures were on par or better than the results that can be achieved through normal maintenance procedures This process has brought a reversal in the loss of income through a steady decrease in the cooling-water temperatures and the resulted improvement to the efficiency of the generation process Figure 20 gives an indication of the amount of money lost for each degree difference in operating between 25 degree Celsius and 32 degree Celsius where 25 degree Celsius is taken as optimum operating temperature

Spares'required not'applicable

Supervision'from'Eskom R30'000,00

Contractors'price'(based'on'historic'tender'prices) R1'007'000,00

Utility'power'and'water'suppllied R25'000,00

Loss'contributed'to'one'cooling'tower R1'062'000,00

Kriel&Power&StationSustainable&maintenance&costaintenance&cost

Direct&cost&of&sustainable&maintenance&of&a&cooling&tower


30

2. Planet The impact on the planet through sustainable maintenance is positive and the effect can be seen in the saving of water and improvement to the GHG emissions

i. WATER a. Water disposed of during outage

No water was disposed of during the sustainable maintenance process b. Evaporation of water

Lower cooling-water temperatures lead to higher efficiency and thus less heat needs to be dissipated through the cooling system. Less heat equals less water used for evaporative cooling

ii. CO2 Emissions Lower operating temperatures achieved through the on-line sustainable maintenance will reduce the CO2 emissions. Higher plant efficiency equals lower CO2 emissions Figure 27 The carbon footprint of the power station is improved by sustainable on-line maintenance

3. People

The elimination of legionella can be achieved with sustainable maintenance i. Healthy working environment In the process of doing on-line sustainable maintenance on the cooling towers, it is possible to access the complete distribution system of the cooling towers and each of the multitude of pipes can be isolated and cleaned by high pressure washing. After cleaning the pipes, each pipe can be flushed to ensure no debris or sludge is left in the pipes The cooling tower sump can be accessed and the complete area of the cooling pond can be swept and large quantities of sludge can be removed during the cleaning process Through the on-line maintenance process the areas where legionella can proliferate and where the bacteria is protected from biocides will be eliminated and thus enabling the killing of the legionella bacteria by water treatment with biocides a. Blocked pipes During the sustainable on-line maintenance project done at KPS, it was found that a large number of distribution pipes were completely blocked. High pressure cleaning opened these pipes and the scale and dirt that was taken out from the pipes had a foul smell indicating bacterial presence These dead zones cause by the blocked pipes cannot be treated by biocides through normal water treatment programs. Only by opening the blocked pipes can these areas be reached and treated by biocides to eliminate the possible presence of legionella Figure 33 Blocked distribution pipes found at KPS pipes

Information supplied by Wasser Cooling Towers. McGillivray (2014)

Total&number&of&distribution&pipes 480Number&of&pipes&completely&blocked 146%&of&blocked&pipes 30%

Total&number&of&distribution&pipes 480Number&of&pipes&completely&blocked 93%&of&blocked&pipes 19%

Maintenance&report&Distribution&systemKRIEL&POWER&STATION

Cooling&tower&3

Cooling&tower&4


31

b. Sludge Cooling tower no. 4 pond was cleaned while the cooling tower was in operation during the sustainable on-line maintenance project A single sweep of the pond was completed in this process and an estimated 43% of the sludge that had accumulated in the pond was removed Although not all the sludge was removed, the entire pond area was swept thus allowing biocides to penetrate and reach all the areas in the pond after on-line cleaning of the pond was done and thus eliminating the dead zones where legionella can proliferate Figure 34 Sludge removal from cooling tower no. 4

Information supplied by Wasser Cooling Towers. McGillivray (2014) Comments on information by McGillivray a. The composition of the sludge at KPS contained a greater number of sub 5 micron particles than anticipated and as the plant was designed to removed a D50/5 micron cut, the percentage of sludge removed by a single sweep was lower than the expected 50% b. The areas in the cooling tower pond not swept is the area taken up by the feeder pipe and columns in the pond

Total&area&of&cooling&tower&pond 6361&m2Area&swept 6020&m2Quantity&of&sludge&estimated&in&cooling&pond 60&tonsQuantity&of&sludge&removed 25,9&tonsPersentage&of&sludge&removed 43%

KRIEL&POWER&STATIONOnLline&sludge&removal

Cooling&tower&4


32

5. ANALYSIS OF RESULTS As sustainability is standing on three legs, profits, people and planet, presentation of the results is given in a three-way conclusion showing the effect of on-line sustainable maintenance on all three legs of the triple bottom line

1. Profit

Comparing the costs of regular maintenance and sustainable maintenance over a two year period (a two year period is used due to current two-yearly outage schedules) give current information on the effect of maintenance on the profit / loss bottom-line. It also gives an indication of the long-term effect that on-line sustainable maintenance solutions will have on the profit bottom-line at KPS

i. Direct cost of cooling tower maintenance

At first glance the cost of on-line sustainable maintenance is higher than regular maintenance A cost increase of 25,4% on a project can be added to the actual direct project costs of doing maintenance on-line. The figure for sustainable maintenance will be much higher as several maintenance projects will be done over a two year period as compare to the single maintenance project for normal maintenance Cost calculation done for a single cooling tower for a single maintenance project Figure 35 Comparable costs of maintenance process

See Figure 14 and Figure 32 The total effect of the multiplied cost of 4 sustainable on-line maintenance projects per cooling tower over a two-year period is seen in the final summary of costs Figure 42

ii. Impact on income during maintenance No outage or standing time in production is required for sustainable on-line maintenance to be done, thus a huge saving can be achieved by doing maintenance on-line. It must be noted that this cost might still be applicable as the balance of the power generation equipment needs to be maintained and the outage might still occur to do this maintenance However, as a half station outage, that is three generation units are required to be shut down to effect normal cooling tower maintenance, a loss of 50% generation capacity, this half station outages can be eliminated by on-line maintenance and a single generation unit can be maintained at any time resulting in only a 16,6% loss of power station production during the time required to do maintenance on the generation equipment such as the condenser tubes, turbines, boiler and other related equipment Cost calculation shown are done for maintenance on a single cooling tower

Description+of+cost+factor Direct+maintenance Sustainable+maintenance

Spares'required not'applicable not'applicable

Supervision'from'Eskom R30'000,00 R30'000,00

Contractors'price'(based'on'historic'tender'prices) R791'466,00 R1'007'000,00

Utility'power'and'water'suppllied R25'000,00 R25'000,00

Total'for'one'cooling'tower R846'466,00 R1'062'000,00

Additional'expense R215'534,00Percentage'increase'in'cost'of'maintenance 25,46%

Kriel+Power+StationMaintenance+cost


33

Figure 36 Loss of income during outage

See Figure 15

iii. Impact of operating temperatures on income With a two-yearly maintenance program on the cooling towers the effect of the rise in operating temperatures in the cooling-water cause losses to be incurred from the 8th month on-wards Calculating the potential losses for a two-year period, it is clear that if on-line sustainable maintenance is done every six months these losses can be eliminated to a great extend Note must be taken that the sustainable on-line project completed achieved even better results Figure 29 than the figures in the graph below thus the six monthly period as suggested to ensure sustained performance of the cooling towers Figure 37 Impact of maintenance on cooling-water temperatures

Allowing for some margin of error, a 27 degree Celsius base line cooling-water temperature is used to calculate loss of income related to higher cooling-water temperatures. Various factors such as local ambient temperatures, fluctuating wet-bulb temperatures, wind conditions and level of contamination of water can influence the cooling efficiency of the cooling system effecting the efficiency of the generation process and 2 degree Celsius margin as used will allow for these factors The losses shown is for a single generation unit, for the full power station losses it will be 6 times these figures

Description+of+cost+factor Estimated+amount

Loss$of$income$during$outage R7$911$877,62

Loss$of$income$during$on9line$maintenance nil

Cooling$tower$water$optimal$operating$temperature 3$unitsTotal$work$rate$of$turbine$train$ 513,1$MW$Total$production$capacity 1539,3MWEfficiency$of$units 98,15%Lost$production 1510,8$MWWeighted$average$selling$price R218,20Number$of$days$lost 10Total$loss$of$income$during$outage R79$118$776,2520%$of$loss$contributed$to$cooling$towers R15$823$755,25No$of$cooling$towers$on$outage 2Loss$contributed$to$one$cooling$tower R7$911$877,62

Kriel+Power+StationEstimated+loss+contributed+to+maintenance+period

Kriel+Power+StationMaintenance+cost

Estimated+loss+contributed+to+maintenance+period

20#

22#

24#

26#

28#

30#

32#

34#

36#

1# 2# 3# 4# 5# 6# 7# 8# 9# 10# 11# 12# 13# 14# 15# 16# 17# 18# 19# 20# 21# 22# 23# 24#

Opera1ng#cooling#water#temperature#

Temperatures in degree Celsius

24 month period

Upward curve of temperatures

Cold months

Cold months


34

Figure 38 Loss of income contributed to a two yearly maintenance program

If an optimum cooling-water baseline temperature of 25 degree Celsius is used, the losses are substantially higher; figures will in this case increase to loss of R33 million after 12 months and R88 million after 2 years for a single generation unit. This will be a total loss of R528 million for the power station over a two-year period These figures are shown only to substantiate the 6-monthly suggested sustainable on-line maintenance period for the cooling towers

2. Planet

i. Water The volume of water saved by sustainable maintenance can be seen when compared to the water consumption and losses for a two-yearly maintenance schedule on the cooling towers a. Water lost through disposal during maintenance

Calculation done is for the full power station Figure 39 Water lost through maintenance

Data$starting$at$the$month$following$an$outage$and$corresponding$data$from$previous$year$outage

Months frommaintenance

Operating$temperatures ofcooling towersserviced duringoutage$(deg$C$)

Excessive temperatureallowing for anexceptable$temperature$of 27 deg C achievablethrough$maintenance$

Loss contributed tohigher operatingtemperatures

Months frommaintenance

Operating$temperatures ofcooling towers inthe year followingan$outage$(deg$C$)

Excessive temperatureallowing for anexceptable$temperature of 27 degC achievable throughmaintenance$

Loss contributed tohigher operatingtemperatures

1 26 0 ER$$$$$$$$$$$$$$$$$$$$$$$$$$$ 13 32 5 5$717$247,38R$$$$$$$$$$$2 26 0 ER$$$$$$$$$$$$$$$$$$$$$$$$$$$ 14 32 5 5$717$247,38R$$$$$$$$$$$3 26 0 ER$$$$$$$$$$$$$$$$$$$$$$$$$$$ 15 33 6 6$809$760,03R$$$$$$$$$$$4 27 0 ER$$$$$$$$$$$$$$$$$$$$$$$$$$$ 16 34 7 7$885$884,99R$$$$$$$$$$$5 26 0 ER$$$$$$$$$$$$$$$$$$$$$$$$$$$ 17 32 5 5$717$247,38R$$$$$$$$$$$6 25 0 ER$$$$$$$$$$$$$$$$$$$$$$$$$$$ 18 31 4 4$608$097,49R$$$$$$$$$$$7 26 0 ER$$$$$$$$$$$$$$$$$$$$$$$$$$$ 19 30 3 3$482$056,98R$$$$$$$$$$$8 27 0 ER$$$$$$$$$$$$$$$$$$$$$$$$$$$ 20 30 3 3$482$056,98R$$$$$$$$$$$9 29 2 2$338$868,65R$$$$$$$$$$ 21 31 4 4$608$097,49R$$$$$$$$$$$10 29 2 2$338$868,65R$$$$$$$$$$ 22 32 5 5$717$247,38R$$$$$$$$$$$11 31 3 3$482$056,98R$$$$$$$$$$ 23 33 6 6$809$760,03R$$$$$$$$$$$12 32 5 5$717$247,38R$$$$$$$$$$ 24 33 6 6$809$760,03R$$$$$$$$$$$

nil

R13$877$041,66

R67$364$463,55

Accumalated$losses$after$8$months



Kriel&Power&StationAccumalated$losses$due$to$variance$in$operating$temperatures

Description+of+cost+factor Unit Direct+maintenance Sustainable+maintenance

Water&lost&through&disposal&per&cooling&tower liters 11844643 0

Number&of&cooling&towers no 4 4

Total&volume&of&water&lost&through&maintenance liters 47378572 0

Water&required&by&family&per&month liters 7500 7500

Families&sustained&for&a&month no 0 6317

Kriel+Power+StationWater+losses+through+maintenance


35

b. Impact of maintenance on evaporative losses Calculation done is for the full power station Figure 40 Water lost through lower efficiency

The water wasted by a lack of maintenance can support a total of 9653 families for a month This waste can also be converted into monetary terms The cost of water in South Africa is around R0.39 per litre Figure 41, this relates to a loss of about R28 million of a two year period for a power station

ii. CO2 emission

Figure 30 shows an improvement in the cooling-water temperatures, it is clear from that improved cooling-water temperatures will relate to improved plant efficiency that will in turn improve the GHG emissions Figure 3 Figure 4. As the CO2 emission is also related to other factors such as the moisture content in the coal-fuel, quantifying the CO2 emissions is beyond the effect of sustainable maintenance on the cooling towers. It can thus only be said that a lower carbon footprint is possible by the improved efficiency of the cooling system of a power station achieved by sustainable maintenance that will result in better power generation efficiency

C. People Quantifying the value of a human life is near impossible. During the sustainable maintenance project the legionella count at the cooling towers was measured and was substantially higher than safe levels for the CFU allowable Figure 28. This can be contributed to the exposure of previous dead or protected areas in the cooling tower where legionella can proliferate and that was cleaned during the sustainable on-line maintenance project. Dangerously high levels of legionella in the cooling-water were found and at least one person was admitted to the hospital after contracting legionella whilst working in the cooling tower. It was fortunate that the person infected was knowledgeable regarding legionella and reported for medical attention within two days of being infected He would have died if medical attention were delayed Interviews with Drotski (2014) and McGillivray (2014) It is clear from Figure 32 and Figure 34 that numerous blocked pipes have been opened and a substantial amount of sludge was removed during the sustainable on-line maintenance to the cooling towers eliminating the breeding areas for legionella bacterium. This elimination of breeding areas has made the cooling towers a far safer environment for human activity

Cooling'system'efficiencyη(cc) 20 1,819 lt'per'kWh 3'732'588''''''''''''''' litersη(cc) 39 2,327 lt'per'kWh 4'775'004''''''''''''''' liters

Water'lost'due'to'efficiency 1'042'416''''''''''''''' liters

Increase'in'water'consumption 28%

Volume'of'water 25'017'984''''''''''''' liters

Water'required'by'family'per'month 7'500''''''''''''''''''''''' liters

Families'sustained'for'a'month 3'336'''''''''''''''''''''''The'rated'2001'capacity'for'KPS'was'used'to'caculated'water'volumes'(TABLE'A)

Water&lost&over&a&two&year&period&

Water comsumption inrelation'to'efficiency

Eskom&Power&StationsWater&losses&related&to&efficiency

Water comsumed over aone'month'period


36

SUMMARY OF ANALYSIS The direct cost of a sustainable maintenance project is marginally higher than the related cost of a regular maintenance project, R0.215 million per cooling tower per project Regular maintenance is done only once on each cooling tower over a two-year period as opposed to the 6-monthly maintenance period as suggested for sustainable on-line maintenance for each cooling tower. This relates to an increase in the number of projects to be undertaken, 12 additional maintenance projects over a two-year period and a huge increase in maintenance expenses. Compared to the money lost due to irregular maintenance, this amount is insignificant small For an outlay of an additional estimated R8 Million a year for maintenance, the power station could gain in excess of R200 Million a year in profits and that does not include the benefits to the planet or the possible saving of a life Figure 42 Quality improvement of maintenance during on-line sustainable maintenance is also possible. A statement made earlier in the paper claims that the sustainable on-line maintenance projects can achieve better results than normal maintenance. This is made possible by that fact that when an outage is arranged for normal maintenance, the time allowed for doing the maintenance work on the cooling tower is limited to the outage period, usually around 10 days. This maintenance will include cleaning the cooling tower pond and servicing / repairs of the distribution system. Due to the nature of this work, it is usually not possible to work at the same time on both the pond and the distribution system and very limited time is allowed for maintenance on either of these. This limited time will result in doing the most obvious maintenance in the shortest possible time hoping for the best results from doing the maintenance Doing on-line sustainable maintenance there are few limitations on the period to do the work (20 working days are suggested and this can be extended) and much more care can be taken whilst doing the work to deliver high quality maintenance work and ensure excellent results in the maintaining of the distribution system. This will deliver superior results for the maintenance work completed and thus achieving better results for the efficiency of the cooling system The results over a two-year period shows that the advantages of sustainable on-line maintenance is substantial in comparison to the normal maintenance done during outages Over a two-year period sustainable on-line maintenance will generate around R 458 000 000,00 additional income for the power station. More than 9000 families will have water to live for a month. The carbon footprint of the power station will be reduced. And finally a safe environment for the people working at KPS will be created Projected advantages over extended periods are huge and financial gains after ten years can reach figures as high as R 2 Billion. Vast quantities of water can be saved and we will have an improved carbon footprint resulting in a much friendlier environment To finalize, we can say that sustainable on-line maintenance will improve the overall sustainability of KPS


37

Figure 42 Triple bottom-line results

Description+of+cost+factor Unit Direct+maintenance Sustainable+maintenanceDirect'cost'of'maintenance'project Amount 2R846'466,00 2R1'062'000,00Number'of'projects'over'two'years No 4 16Total+for+direct+maintenance+costs Amount 7R3+385+864,00 7R16+992+000,00

Cost'contributed'to'outage'per'cooling'tower Amount 2R7'911'877,62 R0,00Number'of'projects No 4 16Total+for+outage+costs Amount 7R31+647+510,48 R0,00

Cost'contributed'by'low'production'per'unit Amount 2R67'364'463,55 R0,00Electricity'generation'units No 6 6Total+for+production+losses Amount 7R404+186+781,30 R0,00

Total+cost+contributed+to+maintenance Amount 7R447+132+033,40 7R16+992+000,00

Savings+contributed+to+sustainable+maintenance R430+140+033,40

Description+of+cost+factor Unit Direct+maintenance Sustainable+maintenanceWater'lost'during'maintenance Volume 247378572 0Cost'of'water Rate R0,40 R0,40Total+for+lost+water+costs Amount 7R18+904+050,23 R0,00

Water'lost'through'evaporation Volume 225017984 0Cost'of'water Rate R0,40 R0,40Total+for+lost+water+costs Amount 7R9+982+175,62 R0,00

Total+cost+contributed+to+maintenance Amount 7R28+886+225,84 R0,00

Savings+contributed+to+sustainable+maintenance R28+886+225,84

9653

Reduced+CO2+emissions

Description+of+cost+factor Direct+maintenance Sustainable+maintenance

Creating+a+save+working+environment No Yes

Carbon+footprint

Kriel+Power+StationTriple+bottom+line+implications+of+maintenance+over+a+two7year+period

PROFIT

PLANET

Number+of+families+sustained+by+water+savings

PEOPLE


38

6. CONCLUSION The evidence leaves no question. It is clear that sustainable on-line maintenance on cooling towers is the only way to ensure an efficient cooling system to sustained power generation and to compliment the triple bottom line of the power station. Cooling towers are an important component of the power generation cycle and should be treated as such Neglect will cause loss of income, wasted water, a spoiled environment and even the loss of a life Look at the bigger picture; on-line sustainable maintenance must be implemented


39

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Zunckei, M. Raghunandan, A (2013) Atmospheric impact report. In support of. Eskom’s application for postponing of the minimum emissions standards compliance timeframes for the Kriel Power Station. [ONLINE] Available at: http://cer.org.za/wp-content/uploads/2014/03/1_Kriel-AIR-FINAL_2013_12_17.pdf [Accessed 03 November 2014]

Najjar, Kenneth F. Shaw John J. Adams, Eric. Jirka, Gerhard H. Harleman, Donald R F (1979). Environmental and economic comparison of cooling systems design for steam-electric power plants. Energy Laboratory Report No. MIT-EL 79-037. January 1979. Massachusetts Institute of technology, Cambridge, Massachusetts. [ONLINE] Available at: https://dspace.mit.edu/bitstream/handle/1721. 1/35208/MIT-EL-79-037-09555116.pdf?sequence=1 [Accessed 21 February 2014]


43

8. REVIEWED LITERATURE

Coal industry advisory board (2008). Power generation from coal. Measuring and reporting efficiency performance and CO2 emissions. [ONLINE] Available at: http://www.iea.org/ciab/papers/power_generation_from_coal.pdf. [Accessed 05 May 2014]

Delgado, Anna. Hertzog, Howard J (2012). A simple model to help understand water use at power plants. Working paper. Massachusetts Institute of Technology. Energy Initiative. 77 Massachusetts Ave. Cambridge. MA. [ONLINE] Available at: http://sequestration.mit.edu/pdf/2012_AD_HJH_WorkingPaper-WaterUse_at_PowerPlants.pdf. [Accessed 20 October 2014]. European Commission (2001). Reference document on the application of Best Available Techniques to Industrial Cooling Systems. Integrated pollution prevention and control. (IPPC). Available on-line: http://eippcb.jrc.ec.europa.eu/reference/BREF/cvs_bref_1201.pdf. [Accessed 18 November 2014] Health and safety executive (1999). Legionnaires disease. The control of legionella bacteria in water systems approved Code of Practice and guidance ISDN 978-0-7176-1771-2. First published in 1999, Second edition 1995, Third edition 2000. Reprinted 2002, 2004, 2006, 2007, 2008, 2012. Copyright Crown Hill, Gerald.B. Pring, E.J. Osborn, Peter D (1967). Cooling Towers. Principle and practice. Third edition. First published by Carter Thermal Engineering Ltd, 1967. Second edition, 1970. Third edition published by Butterworth-Heinemann, 1990. ISDN 0-7506-1005-0.

Laasch, Oliver. Conaway, Roger N (2013). Principles of responsible management: Global sustainability, responsibility and ethics. ISBN 13-978-1-285-08026-0. Cencage learning, 200 First Stamford place, 4th floor, Stamford. CT. USA

Quinn, Laura. Baltes, Jessica (2007). Leadership and the triple bottom line. A CCL Research white paper. . [ONLINE] Available at: http://www.ccl.org/leadership/pdf/research/tripleBottomLine.pdf. [Accessed 09 November 2014]

Randhire Mayur A (2014). Performance Improvement of Natural Draught Cooling Towers. Lakshmi Narayan College of Engineering and Technology, Bhopal, India. International Journal of Engineering Research and Reviews. Vol. 2, Issue 1, pp: (7-15) Month: January-March 2014. [ONLINE] Available at: www.researchpublish.com. [Accessed 03 May 2014]

Scott, R.P (1995). Cooling water – The unseen problems. Tongaat-Hulett Sugar Limited. Amatikulu Mill. Proceeding of the South Africa Sugar technologists association – June 1985. Pages 115 -117. [ONLINE] Available at: http://www.sasta.co.za/wpcontent/uploads/Proceedings/1980s/1985_Scott_Cooling%20 Waters%20The%20Unseen.pdf [Accessed 03 May 2014] Srisawai, Pairat (2000). Legionnaires disease and cooling towers. Page 3. Journal of health science. Vol 9 No 1 January – march 2000. Royal Irrigation Hospital. Pak-kret, Nonthaburi 11120


44

8. BIBLIOGRAPHY

Printed books

Kroos, Kenneth A. Potter, Merle C (2013). Thermodynamics for Engineers. Cencage learning, 200 First Stamford Place. Stamford, CT. Published by Timothy Anderson Lefebvre, Clement M (2007). Electric Power Generation transmission and efficiency. ISDN-10:1-60021-979-9.Nova Science Publishers, Inc, New York

Book previews available in page-image format at books.google.com/books

Breeze, Paul (2005). Power generation Technologies. Second edition. Copyright Paul Breeze. ISDN: 978-0-08-098330-1. Published by Elsevier Ltd. The Boulevard, Langford lane, Kidlington, Oxford, UK Barnet, Dave. Bjornsgaard, Kirk (2000). Power generation: A Nontechnical guide. ISDN13 978-0-87814-753-3. Copyright PennWell Corporation. 1421 South Sheridan road, Tulsa, Oklahoma, USA Curtis, Peter (2011). Maintaining mission critical systems in a 24/7 environment. Second edition. Copyright by the institute of electrical and electronics engineers, inc. Published by John Wiley and sons, inc. Hoboken, New Yearsey Mungan,I. Wittek,U (editors) (2004). Natural draught cooling towers. Proceeding of the fifth international symposium on natural draught cooling towers.2004, IASS, Mimar Sinan University. Istanbul and University of Kaiserlautern. Printed by AA Balkema Publishers, a member of Taylor & Fransis Group plc.Netherlands Parker , Sybil P (1980). McGraw-Hill Encyclopedia of Environmental Science. McGraw-Hill , professional publishing. Boston, USA

Petchers, Neil (2002). Combined heating, cooling, power handbook: technologies and applications: an integrated approach to energy conservation/resource optimization. ISBN 0-88173-433-0. Published by The Fairmont Press, Inc. 700 Indian Trail, Lilburn, GA Rajput, R K (2010). Thermal Engineering. Eighth Edition. ETE 0609-750-thermal engg. Published by Laxmi Publications ltd. Copyright Author and publisher. Golden House, Daryaganj,New Delhi

Rathore, Mahesh M (1997). Comprehensive Engineering Heat transfer. Published by Laxmi Publications (P) Ltd, 7/21, Ansari road, Daryaganj, New Delhi Sivanagaraju, S. Balasubba Reddy, M. Srilatta, D (2010). Generation and utilization of electrical energy. Copyright 2010. Dorling Kindersley (India) pvt ltd. ISDN 978-81-317-3332-5. Published by Dorling Kindersley (India) pvt ltd. Licensees of Pearson education in South Asia. Knowledge Boulevard, Noida, India Wadhwa, C L (1989). Generation Distribution and Utilization of electric energy. Revised edition. Copyright 1989, 1993. New Age International. ISDN 81-224-0073-6. First edition 1989. Revised edition 1993. Reprint 2005. New age International Ltd. Ansari road. New delhi. India

Websites

Beér, Janos (2014). High Efficiency Power Generation, The Environmental Role. Massachusetts Institute of Technology Cambridge, MA 02139 USA . 2014. [ONLINE] Available at: http://mitei.mit.edu/system/files/beer-combustion.pdf. [Accessed 08 August 2014]

Berg, Brian. Lane, R W. Larson, T E (2014). Water use and related cost with cooling towers. [ONLINE] Available at: http://www.isws.illinois.edu/pubdoc/c/iswsc-86.pdf. [Accessed 03 May 2014]

Booras, George. Holt, Neville (2004). Pulverized coal and LGCC plant cost and performance estimates. [ONLINE] Available at: http://large.stanford.edu/courses/2012/ph240/mao2/docs/booras.pdf. [Accessed 16 May 2014]


45

Farris, Andrew (2012). Coal. Copyright, University of Victoria. [ONLINE] Available at: http://www.energybc.ca/profiles/coal.html [Accessed 12 August 2014]

Greenbusiness guide (2013). Kriel power station one of many that are non-compliant. [ONLINE] Available at: http://www.greenbusinessguide.co.za/kriel-power-station-one-of-many-that-are-non-compliant/l [Accessed 18 November 2014]

Jans (2014) Press release: Eskom’s application for increased air pollution from its Kriel Power Station refused. . [ONLINE] http://earthlife.org.za/2014/03/press-release-eskoms-application-for-increased-air-pollution-from-its-kriel-power-station-refused/ [Accessed 18 November 2014]

US department of energy. (2014). Cooling Towers: Understanding Key components of cooling towers and how to improve water efficiency. [ONLINE] Available at: https://www1.eere.energy.gov/femp/pdfs/waterfs_coolingtowers.pdf [Accessed 03 May 2014]

Reports and papers

IEA (2014) Projected cost of generation electricity. 2010 edition. ISDN 978-92-64-08430-8. International Energy Agency. Nuclear Energy Agency. Organization for Economic co-operation and development. . [ONLINE] Available at: http://www.iea.org/publications/freepublications/publication/projected_costs.pdf [Accessed 09 December 2014]

Kang,Y M. Park, G C (1996) A Study of the evaporative heat transfer reactor containment. Seoul National University, Department of Nuclear engineering, Korea. Journal of the Korean Nuclear Society, Vol 29, No 4, pp 291-298, August 1997. [ONLINE] Available at: http://kns.org/jknsfile/v29/A04803285640. pdf [Accessed 09 December 2014]

Kapooria, RK. Kumar,S. Kasana,K S (2007). An analysis of a thermal power plant working on a Rankine cycle: A theoretical investigation. National institute of Technology, Kurukshetra, India. Journal of Energy in Southern Africa. Vol 19. No1. February 2008. [ONLINE] Available at: http://www.erc.uct.ac.za/jesa/volume19/19-1jesa-kapooria-etal.pdf. [Accessed 09 December 2014]

Senges, D C. Alsentzer, H A. Englesson, G A. Hu, M C. Murawczyk, C (1979). Closed cycle Cooling Systems for Steam-electric Power Plants: A state of the art Manual. EPA-600/7-79-001. January 1979. Industrial Environmental Research Laboratory. Office of Energy. Minerals and industry. Research Triangle Park, NC. [ONLINE] Available at: http://nepis.epa.gov/Exe/ZyPDF.cgi/9101E22B.PDF?Dockey=9101E22B.PDF. [Accessed 30 November 2014]

Shaw, John J. Adams, Eric. Barbera, Robert J. Arntzen, Bruce C. Harleman Donald R F (1979). Economic implications of open versus closed cycle cooling for new steam electric power plants: a national and regional survey. Energy Laboratory report no. MIT-EL 79-038. September 1979. [ONLINE] Available at: http://dspace.mit.edu/bitstream/handle/1721.1/35213/MIT-EL-79-038-09510283.pdf?sequence=1 [Accessed 09 November 2014]

World Nuclear Association (2014) Cooling power plants. [ONLINE] Available at: http://www.world-nuclear.org/info/Current-and-Future-Generation/Cooling-Power-Plants/ [Accessed 08 September 2014]


46

9. APPENDICES

Figure 1 Eskom statement of sustainable development

(Eskom. Sustainable development. Available online. See references) Figure 2 Eskom sustainable assurance statement

(Eskom. Sustainability assurance statement. Available online. See references)

INTEGRATED RESULTS PRESENTATION KING III APPLICATION GRI INDEX

HOME INTEGRATED REPORT ANNUAL FINANCIAL STATEMENTS SUPPLEMENTARY AND DIVISIONAL REPORT CORPORATE SOCIAL INVESTMENT INTERIM REPORT ESKOM FACTOR

Integrated report: Currently viewing: Appendix C - Sustainability responsibilities, approval and assurance statements / Next: Appendix D - Online references and supplemental reports

A ' Key performance indicators

B ' Awards

C - Sustainability responsibilities,approval and assurance statements

D - Online references andsupplemental reports

E - Abbreviations, acronyms andglossary

F - Contact details

3/3: If you experience power outages in the Western Cape tomorrow, please contact your local municipality.

Eskom Hld SOC Ltd @Eskom_SA

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2/3: Please note that this is not true; there is no scheduled maintenance at Koeberg power station.


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Appendix C - Sustainability responsibilities, approval and assurance statementsSustainability assurance statements

Sustainability key performance indicators, set out within this report, measure performance on issues material to stakeholders. Thesekey performance indicators have been prepared in accordance with the GRI G3 guidelines, supported by Eskom’s internal reportingguidelines. Eskom’s declaration on its GRI B+ application level is located on page 19. The King Code advocates that sustainabilityreporting and disclosure should be independently assured. KPMG Services (Pty) Limited provided reasonable assurance on selectedsustainability key indicators marked with an “RA” in Appendix A of this report and limited assurance on Eskom’s self-declared GRI B+application level. KPMG’s assurance report is presented in the Eskom supplementary and divisional report. For a morecomprehensive understanding of Eskom’s sustainability performance and its assurance, please refer to the supplementary anddivisional report here.

The board acknowledges its responsibility to ensure the integrity of the integrated report. The directors have collectively reviewed thecontent of the integrated report and believe it addresses the material issues and is a fair presentation of the integrated performance ofthe group.

BA Dames PS O’FlahertyChief executive Finance director

30 May 2013 30 May 2013

Assurance provider's report on extracted sustainability information To the directors of Eskom Holdings SOCLimited

We have conducted an engagement to agree the extracted key performance indicators (or “indicators”), marked “RA” and presentedin Appendix A (“the Appendix”), with the assured key performance indicators presented in the Eskom supplementary and divisionalreport of Eskom Holdings SOC Limited for the year ended 31 March 2013 (“the Eskom supplementary and divisional report”), andreport thereon.

The extracted key performance indicators presented in the Appendix are in support of the material issues presented in the integratedreport. The assured key performance indicators presented in the Eskom supplementary and divisional report were selected by thedirectors for assurance. In our report, dated 30 May 2013, on the sustainability information presented in the Eskom supplementaryand divisional report, we expressed unmodified conclusions inter alia on the selected key performance indicators, prepared inaccordance with Global Reporting Initiative G3 guidelines.

The directors are responsible for identifying the material issues and extracting the appropriate supporting key performance indicators.We report that we have agreed the extracted key performance indicators presented in Appendix A, marked “RA”, with the assured keyperformance indicators presented in the Eskom supplementary and divisional report, also marked “RA”.

The extracted key performance indicators presented in the Appendix are not intended as a fair summary of the assured indicatorspresented in the Eskom supplementary and divisional report. For a better understanding of the sustainability information reported in

the Eskom supplementary and divisional report, the scope of our assurance engagement, the respective responsibilities of thedirectors and assurance provider, a summary of our work performed in the context of the assurance provided and our independentassurance opinions on the identified subject matters, users are referred to the Eskom supplementary and divisional report, which maybe accessed here.

KPMG Services (Pty) Limited

Per PD Naidoo A JafferDirector Director

Johannesburg Johannesburg

30 May 2013 30 May 2013

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47

Figure 3 CO2 emissions vs plant efficiency

COAL INDUSTRY ADVISORY BOARD (2008) Power generation from coal. Measuring and reporting efficiency performance and CO2 emisions. Available online. See references

Figure 4 Relation between cooling-water temperature and condenser pressure

(COAL INDUSTRY ADVISORY BOARD (2008) Power generation from coal. Measuring and reporting efficiency performance and CO2 emisions. Available online. See references)

Figure 2.8: example of relationship between Co2 emissionsand net plant efficiency (with and without CCS)

0

200

400

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800

1 000

1 200

1 400

1 600

25% 30% 35% 38% 40% 42% 45% 50% 55% 55%+CCS

Efficiency (LHV, net output basis)

Spec

ific

CO

emis

sions

(g/k

Wh)

2

Hard coal

Lignite

note: specific co2 emissions are calculated here using iPcc default emission factors for stationary combustion in the energy industries: 94.6 kgco2/gJ for bituminous coal used for power generation and 101.0 kgco2/gJ for lignite (iPcc, 2006). it is assumed that 98% of the fuel carbon is oxidised, the remaining 2% being retained in ash, although this varies in practice (iPcc, 1996). for the case shown with ccs, a co2 capture rate of 90% is assumed.

source: iea analysis.

Determination of emitted CO2

Commercial instrumentation is available for monitoring CO2 concentration and flue gas volume flows. Given the limitations of such instrumentation, the accuracy of directly measured CO2 release is probably no better than that derived by indirect calculation. Moreover, many plants do not measure flue gas volume flow and CO2 concentration, so indirect calculation of emitted CO2 is the only option and can be applied consistently.

Where FGD processes are employed for SO2 removal, the mass release (MFGD) of carbon from the reaction between limestone (CaCO3) and flue gas should be considered in the plant assessment, although its contribution to total emissions will be relatively small. The release mechanism is:

CaCO3(s) + SO2(g) + ½O2(g) + 2H2O(l) Ö CaSO4.2H2O(s) + CO2(g)

The treatment of CO2 emissions from plant incorporating carbon capture is more difficult since the removal efficiency of the capture plant needs to be included in the calculation. It is likely that a removal efficiency factor (XCCS) of 90% or more would be achieved. The calculation of CO2 emissions must account for all these additions and reductions, such that the mass release (Mout) is:

Mout = 3.6632 × (Min + MFGD – Mash) × (1 – XCCS)

Where Min is the mass of carbon in the fuel input and Mash is the mass of unburned carbon retained in ash.

The use of further correction factors for CO2 emissions follows similar principles to those for efficiency calculations. For the purposes of developing a common plant assessment methodology, specific greenhouse- gas emissions analysis is limited only to the CO2 produced during fuel conversion into useful supplies of energy, including electricity and heat. As with efficiency, proper account must be taken of any heat supplied when calculating specific CO2 emissions per unit of electricity supplied.

factors influencing Power Plant efficiency and emissions

35

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010

factors influencing Power Plant efficiency and emissions

25

Ambient conditions change both seasonally and diurnally. In the case of a closed-circuit cooling system, there will be feedback effects from the load on other units which may be using the same cooling system. These all affect heat consumption. Examples of the impact of cooling-water temperature on condenser pressure and the impact of condenser pressure on heat consumption in conventional steam plants are shown in Figures 2.4 and 2.5.

Figure 2.4: example of the impact of cooling-water temperature on condenser pressure for constant unit load

Condenser cooling-water inlet temperature (°C)

90

80

70

60

50

40

30

20

10

0

0 5 10 15 20 25 30

Conden

ser

pre

ssure

(mbar)

source: e.on uk plc.

Figure 2.5: impact of condenser pressure on heat consumption

Hea

tco

nsu

mptio

nco

rrec

tion

fact

or

Back pressure (mbar)

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04

1.05

1.06

1.07

0 20 40 60 80 100

source: gill (1984). reprinted by permission of the publisher. © elsevier, 1984.

© O

ECD

/IEA

2010


48

Figure 5 Schematic of a power plant

Najjar, et al. (1979)Environmental and economic comparison of cooling systems design for steam-electric power plants. See references Figure 6

Cooling tower Cooling tower efficiency

Randhire, M A. (2014)Performance Improvement of Natural Draught Cooling Towers. See references

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International Journal of Engineering Research and Reviews (IJERR) Vol. 2, Issue 1, pp: (1-6), Month: January-March 2014, Available at: www.researchpublish.com

Page | 13 Research Publish Journals

4.6 CALCULATION The calculations are performed to compare the present performance of NDCT (with optimal water distribution) with previous performance of NDCT (with uniform water distribution). The past record of NDCT available with company is as follows. 4.6.1 Previous Performance (with Uniform Water distribution): Flow: 66250 cum/hr WBT: 28 ºC HWT: 41.44 ºC RH: 60% Wind velocity=15 km/h CWT: 33.15 ºC Range = HWT-CWT

= 8.290C Approach = CWT-DBT

=5.350C Efficiency = Approach / (Range + Approach) = 60.77% 4.6.2 Current Performance (with optimal water distribution): Flow: 65372 cum/hr WBT: 27.8 ºC HWT: 41.44 ºC RH: 58 Wind velocity=15 km/h CWT=33.15 ºC Range = HWT-CWT = 9.290C Approach =CWT-DBT=4.350C Efficiency = 68.10%

TABLE II. COMPARISON OF ACTUAL AND PREDICTED PERFORMANCE OF NDCT Sr. No. Parameter Previous Current

1 Range 8.29 9.29

2 Approach 5.35 4.35

3 Efficiency 60.77 68.10

Present CWT is less than past cold water temperature. Thus we obtained a lower water outlet temperature from cooling tower which is 1ºC lower than with a uniform water distribution system. This results in improvement in efficiency by @7%. 4.7 GRAPHICAL REPRESENTATION OF READINGS

TABLE III. PSYCHROMETRIC CHART


49

Figure 7 Cooling tower efficiency uniform sprayer layout vs enhanced sprayer layout

Randhire, M A. (2014)Performance Improvement of Natural Draught Cooling Towers. See references Figure 16

Kriel average yearly temperatures

World weather online. (2014) Average high/low temperatures for Kriel, South Africa. See references

International Journal of Engineering Research and Reviews (IJERR) Vol. 2, Issue 1, pp: (1-6), Month: January-March 2014, Available at: www.researchpublish.com

Page | 14 Research Publish Journals

TABLE IV: RANGE Vs. HWT TABLE V: APPEOACH Vs. HWT

TABLE VI: EFFICIENCY Vs. HWT

5. CONCLUSION

Measurements of the temperature and velocity fields in a cooling tower were performed for the given power

plant parameters, cooling tower constructional characteristics and ambient air velocity conditions in the vicinity of the cooling tower. The last two parameters influence the homogeneity of the heat transfer, from which we can see the anomalies in the cooling towers operation. Homogeneity in the heat transfer could not only be achieved with fault free construction characteristics but also with a proper distribution of water across the plane area of the cooling tower.

In this study, we have analyzed the water distribution across the plane area of the cooling tower. We have

adjusted the amount of water to suit the air flow conditions, which cannot be influenced with natural draft cooling towers. In this way, the optimal moistening of the cooling tower packing is ensured, which results in a more effective heat transfer. With a optimal water distribution, a constant local water outlet temperature is obtained, which decreases the entropy generation and the exergy lost from the cooling tower. The result is lower outlet water temperature from the cooling tower and, thus, from the condenser, which results in greater efficiency of the power plant.

7.67.8

88.28.48.68.8

99.29.4

30 35 40 41.44 45

Current

Previous

0

1

2

3

4

5

6

30 35 40 41.44 45

Current

Previous

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30

40

50

60

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30 35 40 41.44 45

Current

Previous


50

Figure 18 Eskom tariffs

Eskom. Charges and tariffs booklet 2014/15. Available online. See references

Figure 19 Average weighted selling price of electricity

Calculated weighted average cost of Eskom tariffs Figure 23 Average water consumption of South Africa family

Green Living Science Community (2012). See references

User%type Ave%tariff.%(R/MWh) %"of"total"usage Weighted"usageDomestic 288,20R"""""""""""""""""""""""""""""""" 16,80% 48,42"""""""""""""""""""""Agriculture 311,30R"""""""""""""""""""""""""""""""" 2,40% 7,47""""""""""""""""""""""""Mining 153,70R"""""""""""""""""""""""""""""""" 16,00% 24,59"""""""""""""""""""""Manufacturing 183,10R"""""""""""""""""""""""""""""""" 38,00% 69,58"""""""""""""""""""""Commercial 284,50R"""""""""""""""""""""""""""""""" 11,30% 32,15"""""""""""""""""""""Transport 221,30R"""""""""""""""""""""""""""""""" 2,70% 5,98""""""""""""""""""""""""General 234,50R"""""""""""""""""""""""""""""""" 12,80% 30,02"""""""""""""""""""""Weighted"average"price"for"electricty 218,20R""""""""""""""""""""""""""""""""

Kriel%Power%StationWeighted%average%selling%price%of%electricity

Science Communication, Group M

Science Communication | Food Label Cards | Resources | List of Outputs | UP with SCIENCE Home

Green LivingScience Communication, 2012

Activity 9c Energy & water consumption - How do you compare?

Mentors:Koena & Given

Have you ever thought about how much electricity and water you use daily? Let's find out how youcompare.

According to the Department of Water Affairs and Forestry 61% of water is used by the agriculturalsector and 11% by the urban and domestic sector, .

"The typical household in South African uses about250 litres of water a day. That amounts to 7500 litresa month" (Typical household water consumption)What the water is used for is show in the pie-graphon the right.

Water & Energy consumption homework

Let's play "The Brain of WES (Water and Energy Saving)"

1. Divide into 6 Groups, ABC and XYZ.2. Decide on a name for your groups starting with 'A' or 'B' or ...3. Each groups has to compile 2 x 5 questions; the questions have to be energy and water related

(2:3 or 3:2) with the following restrictions:i. one question should have a true / false answer;ii. one questions should have yes / no answers;iii. one questions should be a multiple choice question with 3 answer choices;iv. one question should have an answer that has to be calculated;v. all questions should refer to South African issues.

4. Let's play: Group A will pose questions to group B, group C to keep time - 1 minute for 5

questions - (X to Y and Z as time keeper); then group A will pose questions to group C and groupB will be the time keeper, etc.Marks: One markd for each correct answer.

5. The winning groups of groups A, B and C and groups X, Y and Z will compete against each other ina round of questions compiled by Koena and Given.

Ideas for your questions

1. Look at the climate of the capitals of the nine provinces of South Africa. Find out what the averagemonthly rainfall is for each of the capitals as well as average monthtly minimum andmaximum temperature. Use this inforamtion in your questions.

2. Find out what the annual average rainfall for South Africa is. 3. Look at water saving suggestions (aimed at people of your age group) and ask question around

that.4. Ask question based on the results of your Energy and Water Worksheet.

References & Resources

Department of Water Affairs and Forestry, 2003. Water Conservation and Water Demand Management Strategy forIndustry, Mining and Commercial water use sector. Viewed online ON 1 aPRIL 2012 atwww.dwaf.gov.za/WaterConservation/Programs_IMP.htm#_Toc44209430Water Rapsody. ???? Typical household water consumption. Viewed online on 1 April 2012 atwww.capewatersolutions.co.za/2010/02/06/typical-household-water-consumption/Water Rapsody. September 2009. Water Facts in South Africa. Viewed online on 1 April 2012 at:


51

Figure 25 Coal-fired plants in Eskom data set

Delgado, A. Hertzog, H J. (Date unknown). A simple model to help understand water use at power plants. Working paper. See references Figure 28 Comparison of legionella counts at KPS

On-site data by Wasser Cooling Towers. McGillivray (2014)

page 10

Plant Cooling System Type Heat Rate (kJ/kWh)

Water Consumption (L/MWh)

Arnot Wet tower (ncc = 20) 11,030 2,074

Duvha Wet tower (ncc = 20) 10,686 2,005

Hendrina Wet tower (ncc = 20) 11,747 2,327

Kendal Indirect dry 11,002 136

Matla Wet tower (ncc = 14) 10,265 1,994

Lethabo Wet tower (ncc = 39) 10,308 1,819

Matimba Direct dry 10,670 106

Tutuka Wet tower (ncc = 39) 10,230 1,915

Table 3. Coal-fired power plants in the Eskom data set, with median values of heat rate and water consumption intensity

Parameter A was estimated using Equation 8. The value of ncc was given for each power plant, kbd is

zero, since all plants follow a zero liquid discharge policy and ksens was estimated at 15%, which would be

typical for a wet-cooled coal plant in a dry location [17]. This resulted in a value of A between 3.5E-04 –

3.7E-04 L/kJ (depending on the ncc of the plant).

The parameter B includes 3,600 kJ/kWh of heat that is contained in the electricity generated plus all the

heat that is rejected to the environment through the flue gas and other heat losses. For this case, sub-

critical power plants with no FGD systems, a value of B = 5,400 kJ/kWh was assumed.

The parameter C was estimated as 0.1 l/kWh. This value was chosen roughly in the middle of the values

found in the literature for PC power plants without FGD (0.06 l/kWh) and the Eskom field data from the

two dry-cooled plants (0.106 l/kWh and 0.136 l/kWh).

Even using estimated values for C, B and ksens,, the agreement of the model values with field data values is

quite good (see Figure 4); the standard deviation of the fit is 131 L/MWh (i.e., agreement in the range of

5-7%). The agreement is even better when looking at yearly average values for each plant (see Figure 5).

If values for the parameters, would be calculated specifically for each power plant, we would get better

estimates. However, since the heat rate explains much of the variation in water use, we can get a good

estimate of water use in power plants using the model by just knowing the heat rate and making

reasonable estimates for the other variables.

Central Microbiology Laboratory

Tests marked "Not SANAS accredited" in this report are not included in the SANAS Schedule of Accreditation for this laboratory.

Opinions and interpretations expressed herein are outside the scope of SANAS accredition,PLEASE NOTE: The test results relate only to the specified samples tested as identified in this report.This test report shall not be reproduced except in full, without written approval of ESKOM holdings (Cleveland) Chemical Technologies.

Lower Germiston Road Private Bag 40175 Cleveland 2022Tel +27 11 629 5339 Fax +27 11 629 5528 [email protected]

Eskom Holdings Reg No 2002/015527/06

Laboratory Number T0055

Final Task Report

Address P/Bag x5009Kriel

Attention M. MasokoamengClient Name Kriel P/S

Fax Telephone 8258 2152

Report ReferenceML2014-010334

Date ReportedDate Registered

Description of SamplesNumber of Samples

15-July-201409-July-2014

4

Task authorised by:

Dipuo Chaha

Microbiologist

Legionella Cooling waterDate Received 08-July-2014

Page 1 of 3Report Ref: ML2014-010334

The analyses were performed using the following methods:Legionella CW/ Raw Water Eskom Method E431 Rev.3 Not Accredited

Result UnitValueCWS MAIN

5593439 MICRO-2014-07-7/013949Customer Sample IDSample ID

Legionella Count MPN/L7500

Result UnitValueCWS EAST



Result UnitValueCWS WEST


Legionella Count MPN/L>55000

Result UnitValueCLEANING TANK



Task Comments:Eskom Generation Legionella Guideline: GGL 36-104 and SANS 893-1 and 2.System under control: 100 cfu/L or lessReview programme operation: >100 up to 1000 cfu/LImplement corrective action: >1000 cfu/L. MPN/L is equal to CFU/L.

Page 2 of 3Report Ref: ML2014-010334


52

Figure 29 On-site temperatures taken during sustainable maintenance project

On-site data taken and recorded by Wasser Cooling Towers. McGillivray (2014)

Figure 41 Water tariffs from the South African Rand Water Board

Rand water board (2014). See references

Date%recorded Water%temperature Ambient%temperature Differential296Sep 37 21,1 15,9306Sep 32 25,6 6,4016Oct 31 21,9 9,1026Oct 37 23,1 13,9036Oct 29 19 10066Oct 29 26,1 2,9076Oct 29 26,9 2,1086Oct 30 29,1 0,9096Oct 29 30 61106Oct 29 22,4 6,6136Oct 29 19,1 9,9146Oct 29 26,1 2,9156Oct 27 20,8 6,2166Oct 27 23,8 3,2176Oct 29 18,5 10,5206Oct 24 18,3 5,7216Oct 28 28,8 60,8226Oct 29 26 3236Oct 28 24 4246Oct 25 29,1 64,1276Oct 24 21,8 2,2286Oct 26 26,6 60,6296Oct 26 28,4 62,4306Oct 26 28,7 62,7316Oct 26 27,4 61,4036Nov 26 26 0046Nov 27 20,4 6,6056Nov 23 24,5 61,5066Nov 23 25,3 62,3076Nov 23 26,1 63,1036Jan 25 18,8 6,2046Jan 25 25,2 60,2056Jan 22 23 61066Jan 25 24,3 0,7076Jan 24 21,5 2,5

Temperatures*taken*during*the*sustainable*maintenance*project

15%

17%

19%

21%

23%

25%

27%

29%

31%

33%

35%

37%

39%

1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 16% 17% 18% 19% 20% 21% 22% 23% 24% 25% 26% 27% 28% 29% 30% 31% 32% 33% 34% 35%

Daily%temperatures%as%measured%

Ambient%

ALL TARIFFS (c/kl) Tarriffs 1 July 2010 - 30 June 2011PERCENTAGE INCREASE IN TARIFF 14.1% 14.1% 14.1% 14.1% 14.1%

Bulk Municipal Bu Mines - lk/Domestic

Crushing Mines - Operational

Non Crushing Mines -

OperationalSpoornet / Railways

RW Tarriff (excl)VAT 399.208955 399.208955 598.813437 598.813437 619.232638VAT on RW tarriff 56.889254 56.889254 83.833881 83.833881 86.692569

Rand Water tarriff (incl VAT) 455.098209 455.098209 682.647318 682.647318 705.925207(Amount shown on Tariff increase letter)

WRC Levy 3.850000 3.850000 3.850000 3.850000 3.850000

(Amount shown on RW invoice)Total RW + Levy 458.948209 458.948209 686.497318 686.497318 709.775207Total VAT (RW+Levy) 60.739254 60.739254 87.683881 87.683881 90.542569

Total RW + Levy (incl VAT) 458.948209 458.948209 686.497318 686.497318 709.775207

Retail CustomersPERCENTAGE INCREASE IN TARIFF 14.10%

0 - 6 kl 6.1 - 15 kl 15.1 - 20.0 kl 20.1 - 40kl > 40 klRW Tarriff (excl)VAT 0.000000 605.615624 660.045727 720.056786 750.037006VAT on RW tarriff 0.000000 84.786187 92.406402 100.80795 105.005181

Rand Water tarriff (incl VAT) 0.000000 690.401811 752.452129 820.864736 855.042187(Amount shown on Tariff increase letter)

WRC Levy 0.000000 3.850000 3.850000 3.850000 3.850000

(Amount shown on RW invoice)Total RW + Levy (excl VAT) 0.000000 694.251811 756.302129 824.714736 858.892187Total VAT (RW+Levy) 0.000000 88.636187 96.256402 104.657950 108.855181

Total RW + Levy (incl VAT) 0.000000 694.251811 756.302129 824.714736 858.892187


53

Table A KPS technical data

Eskom, Kriel Power Station. Available online. See references

Location:))Between)the)towns)of)Kriel)and)Ogies)in)MpumalangaTechnical)details:)Six)500MW)units)Installed)capacity: )3)000MW)2001)capacity:) 2)850MW)Design)efficiency)at)rated)turbine)MCR)(%): )36.90%)Ramp)rate:) 45.45%)per)hour)Average)availability)over)last)3)years: )93.37%)Average)production)over)last)3)years:) 17)452GWhTechnical)Data:Fuel)Calorific)value)(underground)coal) 23,4)MJ\kg)(dry)basis)(opencast)coal)) 18,2)X)20,4)MJ\kg)(dry)basis)Ash)content)(underground)coal) 23,4%)(dry)basis)(opencast)coal)) :)32%)(dry)basis))Sulphur)content)(underground)coal) :)1%)(dry)basis)(opencast)coal) :)1%)(dry)basis))Coal)consumed)at)full)load) :)1400)tons\hTotal)annual)consumption) :)8)X)9)million)tons)Coal)staithe)capacity 120)620)tonsStaithe)1 72)000)tonsStaithe)2 48)620)tonsStockpile)capacity 1,7)million)tons)Boiler)bunker)capacity 19)900)tons)per)unitFuel)oil LO)5Storage)capacity 2000)tonsAnnual)consumption)(total) :)4000)klAnnual)consumption)per)unit :)750)klMills)Manufacturer:) BABCOCK)&)WILCOX)(SA))Type:) Medium)speed,)vertical)spindle)Number:) 6)per)unitTurbines)Manufacturer:) Brown)Boveri)\)CEM)Type:) Multi)cylinder)impulse)reaction)Rating)(generator)output)) 550)MVA)Speed) 3000)r\min)Total)work)rate)of)turbine)train) 513,1)MW)Total)efficiency 98,15%Boilers)Manufacturer) Steinmuller)(Africa))Pty)Ltd.)Type) Benson)Number) 6Maximum)continuous)rating) 440)kg\sGenerators)Manufacturer) CEM\BBC)Rated)capacity) 555)MVA)Total)efficiency)of)generators) 98,15%

Kriel)Power)StationTechnical)information)of)Power)Station


54

Table D Evaporation losses in cooling towers

(Kim, C. (2008) Increased Cooling Tower efficiency. Available online. See references.)

Note. This graph is representative of USA weather conditions, thus the higher losses is during the warm summer temperatures when operating temperatures in the cooling towers rises with the ambient temperatures. For South African conditions the graph will be inverted as the coldest months is June and July

Figure 4 | Total water make-up (MU), blowdown (BD) and evaporation loss by central and satellite Cooling

Towers and Cooling Degree Days (CDD). Water consumption by the cooling towers generally follows the trend of CDD as expected. However, it is noticeable that the water consumption during the summer break (June, July and August) does not increase as sharply as the CDD do.

Figures 3 and 4 show that cooling water is lost more through evaporation than through

blowdown. Numerical data of total make-up, blowdown and evaporative loss show that only 9 to 24 per cent of make-up water is lost through blowdown (Table 1).

2. Vapor Recovery Experiment In order to estimate how much vapor can be absorbed by different filters and parameters,

a simple experiment was designed using an ultrasonic humidifier (Fig. 5) as a cooling tower prototype.

Supply rate of vapor from the humidifier was calculated by dividing the difference of water remaining in the tank of the humidifier by amount of time passed.

Time Passed Water Initial (ml) Water After (ml) Difference (ml) Rate (ml/min)

137 min 1000 738 262 1.912 308 min 20 sec 2000 1302 698 2.264 739 min 1 sec 2000 355 1645 2.226

Table 2 | Amount of water emitted by the ultrasonic humidifier over different periods of time


55

10. INTERVIEWS The interviews conducted were free conversations and both formal and informal meetings were held with between the parties at various intervals

Kenny, Brian. Technical Director at Wasser Cooling Towers. Research and development head for sustainable maintenance solutions for cooling towers Various interviews held during the period from March 2013 to October 2014 McGillivray, Glen. Project controller for Wasser Cooling Towers. On site expertize at Kriel Power station Various interviews held during the period from January 2014 to October 2014 Mathebebe, Gontsi. Systems Engineer. Employed at Kriel Power Station Various interviews held during the period from January 2014 to October 2014 Drotski, Ivan. Electrical/Mechanical Engineer. Specializing in Power generation. Auxiliary systems. Acting as a consultant to Eskom, Employed by Tekniva South Africa Various interviews held during the period from March 2013 to October 2014

11. ACKNOWLEGEMENTS Thanks to all my lecturers throughout my studies for the valuable aid and information given by them. My advisor, Prof Neil McGregor, thanks you for your inputs and advise on completing the dissertation. Finally my gratitude to Brian Kenny, Glen McGillivray, Gontsi Matibebe and last but not least, Ivan Drotski 12. STATEMENT OF ORIGINALITY The work in this paper is my own and all phrases, scriptures, quotes and reference to other work has been acknowledged and referenced accordingly

donovan fourie 13 january 2015

Documents

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evaporation of water

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