suitable energy system determination for a university campus prepared by : olcay kincay zehra...

SUITABLE ENERGY SYSTEM DETERMINATIONFOR A UNIVERSITY CAMPUS

Prepared by : Olcay Kincay Zehra Yumurtaci

YILDIZ TECHNICAL UNIVERSITY

IGEC-2INTERNATIONAL GREEN ENERGY

CONFERENCE

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INTRODUCTION


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Yildiz Technical University is established in 1911, and today serves with;


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• 9 faculties,

As the student number and required space increased, Davutpasa campus is added to current campus located in Besiktas.

• 2 Institutes,

• Foreign Languages College,

• vocational high school and

•approximately 20000 students.

INTRODUCTION


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Davutpasa Campus is located on a 1.312.500 m2 field and has newly built and historical buildings inside.


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Turkey’s largest techno park project is going on a 40 acre area. Today, approximately 5000 students study in this campus. In time, as other buildings are finished, some other departments will be moved to Davutpasa campus and student number will increase considerably.

This campus also has closed and open sports halls, stadium, and indoor swimming pool. Istanbul Science Center is planned to be built here and 1 million people of yearly visitors are expected.

INTRODUCTION


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Additionally, it is planned to have a campus where education and daily life are combined with dormitories and lodgments of 3000 capacity, social facilities.


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All this data show the importance of this campus (www.yildiz.edu.tr).

2004 values of electricity and heat consumption of this campus show that the most suitable system to supply energy is cogeneration system.

It will be possible to add cooling system and turn the system into a trigeneration system in the future.

WHAT IS COGENERATION?


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Cogeneration is producing both power and heat together where they both will be used. Working principle of cogeneration is very simple.


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Cogeneration system consists of an electrical generator and a heat source. Dual production of heat and energy together is known as “total energy”. Known power generation systems have an efficiency of about 35%. 65% of the energy potential remains as waste energy.



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This heat energy can be used in industry, residential heating and cooling and the total efficiency can get to 55%. As seen in Figure 1, with usage of heat energy, the thermal efficiency of the cogeneration plant can be 90% or higher.


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Additionally, since the electricity generated by the cogeneration systems used locally, conduction and distribution losses are at minimal level therefore, compared to a conventional electricity generating plant, 15 to 40 % economy is obtained.



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Thus, cogeneration systems are applicable on chemical facilities, refineries, paper industry, food industry, educational facilities and hospitals, large residential facilities where heat and electricity are needed together.


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Today, the electricity and heat power produced in American universities is at 600MW level. In Figure 1, a gas turbine cogeneration system is shown. (Yumurtacı, Z.,et al.,2002)



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Fig. 1. Gas turbine cogeneration system


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System and Capacity Determination of Cogeneration


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System determination criteria for such applications are as follows: (Aras, H. et al., 2004) (Aras, H., 2003)


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• Electricity heat consumption structure of the establishment and electricity-heat balance,

• Annual working time of the establishment,

• Energy need level of the establishment,

• Availability and feasibility of primary energy sources.



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The first two are the most important criteria.


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Primary objective is to determine electrical capacity. After the electrical capacity of the plant is determined, heat production values are investigated.

In order to make a healthy plant selection, if possible, annual, monthly or weekly consumption values must be determined and indicated with graphics. First the annual electricity consumption values are analyzed and capacity is determined as a little lower than this value, to prevent idle capacity.



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Another important feature of the cogeneration systems is the quality of the useful heat. In case of gas turbine, exhaust gases can be utilized as direct usage of heat. For instance, drying processes in cement industry, ceramic factories ( Hepbasli.A. and Ozalp.N., 2002).


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Cogeneration plants are known to have a total efficiency above 90% diesel engines and combined cycle plants have a higher electrical efficiency, on the other hand, gas engines, gas turbines and steam turbines are capable of higher thermal efficiency values.



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Bound to compliance with maintenance procedures, cogeneration technologies have a long working life (Atikol.U. , et al., 2003).


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Power values for different cogeneration systems are given in Table 1.

After analyzing this table, gas turbine is the most appropriate selection.



CONFERENCEYILDIZ TECHNICAL UNIVERSITY

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Prime Mover Fuel UsedSize Range(MWe)

Heat:Power ratioElectrical Generating Efficiency

Typical Overall Efficiency

Heat Quality

Steam Turbine Any fuel 1 to 100+ 3/1 to 8/1+ 10-20 % up to 80%Steam at 2 press or more

Back Pressure Steam Turbine

Any fuel 0.5 to 500 3/1to 10/1+ 7-20 % up to 80%Steam at 2 press or more

Combined cycle gas turbine

Gas,biogas,gasoil,LFO,LPG,Naphtha

3 to 300+ 1/1 to 3/1 * 35-55 % 73-90 %

Medium grade steam high temperature hot water

Open cycle Gas turbine

Gas,biogas,gasoil,HFO, LFO,LPG,Naphtha

0.25 to 50+ 1.5/1 to 5/1* 25-42 % 65-87 %

High grade steam high temperature hot water

Compress.Ignitionengine

Gas,biogas,gasoil,HFO, LHO,Naphtha

0.2 to 200.5/1 to 3/1*Alfa value 0.9-2

35-45 % 65-90 %

Low pressure steam low and medium temperature hot water

Spark Ignition Engine

Gas,Biogas,LHO,Naphtha

0.003 to 6 1/1 to 3/1 alfa value 0.9-2 25 - 43 % 70- 92 %Low and medium temperature hot water

Table 1. Typical Cogeneration Systems (Guide to Cogeneration)

Information about Cogeneration System


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There are some points to be taken into consideration while designing cogeneration system of Yildiz Technical University Davutpasa campus. For instance; when the system demand of electricity and heat are maximum, whether their peak is at the same time or separate etc.


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In this study, in order to analyze feasibility, it is considered that electricity and heat demand is between 07:00 and 22:00 hours. These values will decrease in summer season because the heat demand will almost become zero. However, since there is summer classes in the campus, decrease of electricity demand will not be as much as heat demand decrease.

Information about the Facility


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Facility type: University campus


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Annual work hours: 8000 h / year (one year is assumed to be 24 x 365 = 8760 hours)

Load factor: 8000 / 8760 = 0, 91

Average temperature: 20 °C

Elevation: 70 meters

Fuel to be used: Natural gas



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There is no demand for steam at the facility; only 70-90 °C hot water is demanded.


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Monthly distribution of the annual electricity consumption of Yildiz Technical University Davutpasa Campus is given in Figure 3 (YTU data, 2004).

Monthly distribution of the annual fuel consumption of Yildiz Technical University Davutpasa campus (according to fuel costs paid) is given in Figure 2. (YTU data, 2004).



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Fig. 2. Monthly distribution of natural gas bills of YTU Davutpasa campus


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050

100150200250300350

months

natu

ral-

gas

co

nsu

mp

tio

n(1

000*m

3)



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Fig. 3. Monthly distribution of electricity gas bills of YTU Davutpasa campus


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050

100150200250300350400450

months

ele

ctr

cit

y

co

nsu

mp

tio

n(1

000*k

Wh

)



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Table 2 shows the equivalent kWh values of the payment values given in Fig.2 and Fig.3.


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Considering that the facility is working 20 hours a day and 26 days a month, the power of the system can be calculated as follows:

403920 / 15* 26 = 1035,7 kW

As it can be seen in this table, the moth that maximum electricity demand takes place is December and the electricity demand is 403.920 kWh.



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Considering that the system will be working at higher power, electrical power (EP) of the system is selected 1155 kW.


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Approximately 4-5% of this power is alternator loss. Generator efficiency is 95%

After taking the alternator losses into account, and selecting a standard turbine from the catalogues, the turbine with 1204 kW mechanical power is selected.

Annual electricity energy (AEG) generated by the system (8000 hours) is calculated as:

AEG= EP x working hours= 1204*8000 = 9.632.000

kWh/year



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Table 2.Monthly electricity and heat consumption


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Month Heat (kWh) Electricity (kWh)

January 633822,68 120960

February 1103664,11 111283

March 991696,78 126317

April 733391,72 120960

May 101828,09 99360

June 21795,77 89543

July 16844,94 81489

August 4913,66 73440

September 11231,07 79920

October 17648,48 114480

November 2233038,50 120960

December 3521305,31 403920

Total: 9391181,11 1542632



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The system generates 9.632.000 kWh electrical energy each year.


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After the demands are analyzed, it is obvious that electricity demand is high, and the heat demands are lower. For such facilities, it is recommended to choose a counter-pressure steam turbine. However, the costs of a steam turbine are high and operation and maintenance of such systems are more difficult, thus steam turbine is not selected in this case.



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There is a steam demand by the industrial facilities around the campus; therefore, any steam generated in the campus can be utilized as profit.


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Taking all these points into consideration, an easier operational, multi-fuel driven system that has a short installation process, a low establishment cost, and that can easily start/stop must be preferred.According to these criteria, from Table 2, a gas turbine system is preferred.

Information on selected gas turbine


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After the explanations and calculations mentioned above, the gas turbine with the technical data given in Table 3 is selected.


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The average electrical efficiency of the system is (ηe) 40%. Average thermal efficiency of the system is also assumed to be (ηı) 45%.

The efficiency rate of the present boiler is 90%. The fuel of the system is natural gas. (Z.Yumurtacı, H.Obdan,2005).

All the cost calculations are conducted according to these assumptions and data.

Information on selected gas turbine


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Table 3. The specifications of the selected Gas turbine (www.turbomach.com)


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Electrical Power: kW 1204

Fuel consumption: kW 4949

Turbine efficiency: % 24,58

Exhaust gas flow rate kg/s 6,45

Exhaust gas temp. °C 500

Fuel: * A/B/C/D

Start system: AC

Generator Voltage: V 400

A:Gas, B:Liquid fuel, C:LPG, D:Medium/low BTU Gas

Specifications and the price of natural gas


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Higher heating value of natural gas is= 9155 kcal/Nm3

= 38267,9 kJ/Nm3 (January,2005)(www.botas.gov.tr)


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Lower heating value of natural gas is (Hu)

= Higher heating value x 0.90

Hu= 8239,5 kcal/Nm3 = 34441,11 kJ/Nm3

Unit cost: 0,438609 YTL/Nm3

= 0,04122 YTL/kWh =0,0556 $/kWh = 0, 324 $/Nm3

(January, 2005) (www.igdas.com.tr) ($=1,35 YTL)

Specifications and the price of natural gas


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• Specific fuel consumption of the system is: 0,235 kg/kWh


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• Hourly fuel consumption of the system is: 282,94 kg/h • Annual fuel consumption of the system: 2263520 kg/year • Annual heat generation of the system: 10.827.519,63 kWh

Calculations according to these statements show that there is no need for an additional boiler since the heat generated from cogeneration is higher than the heat the system consumes.

(10.827.519, 63 kWh > 9.391.181, 11 kWh)

Operational economy of the system


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Economy of electricity:


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The amount not to be bought from TEDAS: 9.632.000 kWh/yearAverage electricity price: 0,094 $/kWh (January, 2005) (www.tedas.gov.tr)Economy from generation of electricity: 905.408 $/year Amount to be sold to TEDAS: 8.089.368 kWh/year

Buying price of TEDAS: 0,094 x 0, 8 = 0, 0752 $/kWh (TEDAS buys approximately 20% cheaper)

Annual net profit of selling to TEDAS: 608.320, 47 $/year Annual total profit of electricity: 905.408 $/year + 608320, 47 $/year = 1.513.728, 47 $/year



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Economy of heat:


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Economy from the heat to be generated at the boiler: 10827519,63 kWh/year

Annual natural gas saving: 1.131.760 Nm3/year

Annual saving of cogeneration heat: 496.400 $/year Heat to be sold: 1.436.338,52 kWh/year

Natural gas consumed in order to generate that heat: 135.121,56 Nm3 natural gas.

Cost of that amount of natural gas: 43.779,38 $/year



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Total annual operation income of the system :


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1.513.728,47 $/year + 496.400 $/year + 43.779,38 $/year = 2.053.907 $/year

Operational costs of the system


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Annual Fuel Cost :


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Lower heating value of natural gas Hu= 38.267,9 kJ/Nm3

Specific fuel consumption: 14.798 kJ/kWh, Fuel consumption: 4.949 kJ/h (www.turbomach.com)

m=515, 8 (Nm3/h) x 8000(h) =4.126.400 Nm3/year

Annual fuel costs of the system: 4.126.400 Nm3/year x 0, 324 $/Nm3 = 1.336.953, 6 $/year



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Annual Service, spare part and oil costs of the system:


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Annual service, spare part and oil cost of the system is assumed to be 10% of the first establishment costs.

Annual service, spare part and oil cost of the system: 70.000 $/year



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Personnel costs:


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Personnel gross cost: 2 $/h

System supervision time of the personnel: 8350 h/year

Annual personnel cost: 2 $/h x 8.350 h/year=16700 $/year



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Internal consumption cost:


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Internal electricity consumption amount: 45kW

Annual internal electricity consumption cost: 15.000 $/year



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Total costs:


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1.336.953, 6 $/year + 70.000 $/year + 16.700 $/year + 15.000 $/year = 1.438.653, 6 $/year

As it can be seen, about 95% of the costs consist of fuel cost. Therefore the unit price of natural gas has a great importance. Especially in countries that are out-dependant on fuel, the unit price has a great effect on the case.

Amortization calculation of the system


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Total investment costs of the system: 700.000 $ (www.turbomach.com)


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Net operational income of the system: 2090128, 47 $/year – 1.438.653,6 $/year = 651.474,87 $/year

Amortization time of the system: 1,1 year

All the assumptions and the resulting values are given in Table 5.

GAS TURBINE EMISSIONS


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When the emission value of the selected turbine system is analyzed, it can be seen that the system is environment-friendly.


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Since the system is located in a residential area, the emission values must be at decent levels.

Emission values of an approximately 1.000 kW turbine energy plant are given in Table 4.

These values are significantly lower compared to the other fossil fuel plants. Today, there are studies to decrease these values.



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Table 4. Gas turbine emission characteristics


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(Environmental Protection Agency Climate Protection Partnership Division, 2002)

Electricity capacity (kW) 1000

Electrical Efficiency(HHV) 22%

NOx(ppm) 42

NOx(lb/MWh) 2,43

CO (ppm) 20

CO (lb/MWh) 0,71

CO2 (lb/MWh) 1,887

Carbon (lb/MWh) 515



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Table 5. Assumptions and calculations used in analysis


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TECHNICAL DATA

Unit number 1 Unit

Electricity Power 1204 kWe

Mechanical Power 1155 kWm

Electrical Efficiency 40 %

Thermal Efficiency 45 %

Generator Efficiency 95 %

Working hours 8000 h/year

Load factor 0,91

Average Temperature 26 °C

Fuel Used Natural gas

Lower heating value of the fuel34441.11 kJ/Nm3

34541Kj/Nm3



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PRICES

Unit price of the fuel 0,324 $/Nm3

Cost to TEDAS 0,094 S/kWh

ELECTRICITY-HEAT GENERATION AND CONSUMPTION VALUES

Annual Electricity generation 9632000 kWh/year

Annual Electricity demand 1542632 kWh/year

Annual heat Generation10827519,63 kWh10854509

kWh/year

Annual heat Demand 9391181,11kWh/year



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OPERATIONAL COSTS

Total Fuel Consumption 4126400 Nm3/y

Annual Fuel cost 1336953, 6 $/year

Annual oil+service+maintenance cost 70000 $/year

Personnel cost 16700 $/year

Internal Electricity consumption cost 15000 $/year

Total costs 1438653,6 $/year

INVESTMENT COSTS

Investment cost of the system 700000 $

AMORTİZATION TIME

Net operational income 651474,87 $

Amortization 1,1 year

RESULTS AND RECOMMENDATIONS


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In this study, the cogeneration system to be applied at the university has shown a total income of 2.053.907,85 $ and a total cost of 1.438.653, 6 $.


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The system amortizes itself in 1,1 years. Net operation income of the system is 651.474, 87 $.

As the campus enlarges, the heating demand will increase, the heat generated by the cogeneration system will become more efficient, and the costs will decrease. As these values are analyzed, the system is profitable. The most important factors that determine the costs of the system are electricity and natural gas unit prices.



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As these increase the amortization period becomes longer. One of the most important advantages of this system is that it is an independent system.


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In today’s world that the energy resources are decreasing and the environmental pollution is rapidly increasing.It has gained a great importance to use clean energy sources and to use them more efficiently.

Especially in the developing countries energy generation without being out-dependant is one of the first things to be considered. In this study, the analyzed cogeneration systems are leading systems regarding the efficient resource utilization and environmental sensitivity.



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As seen in the case study of Yildiz Technical University Davutpasa Campus, although the investment cost are high for a cogeneration system, the opportunities as selling redundant energy and efficient utilization of resources makes cogeneration systems attractive for such applications.


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Pre-design studies must be carried out carefully and the demands must be fully evaluated. It is easily possible to gain great economy using a cogeneration system that has adapted present conditions.



CONFERENCEYILDIZ TECHNICAL UNIVERSITY

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In this study, cogeneration system is calculated using 2004 electricity and natural gas values of Davutpasa Campus.

As the campus enlarges, some other faculties are planned to be moved, constructions to be completed, and techno park to be completed, thus, the energy demand values should be re-evaluated in order to make a healthy system design.



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THANK YOU

PrPreepared bypared by : : Olcay Kincay,Olcay Kincay,[email protected]

Zehra YumurtaciZehra [email protected]