Seminar Report on

Solar Power Tower

By

Name :Kaushik Kishore

Roll No: 1230931022

Course: B. Tech

Department of Electronics &Communication EngineeringRAJ KUMAR GOEL ENGINEERING COLLEGE,

HAPUR- 245304 (U.P.) (Affiliated to UPTU, Lucknow)

RAJ KUMAR GOEL ENGINEERING COLLEGEHAPUR- 245304 (U.P.)

(Affiliated to UPTU, Lucknow)

CERTIFICATE

This is to certify that the Seminar Report entitled “Solar Power Tower Technology” is

submitted by Kaushik Kishore bearing Roll No 1230931022 in B.Tech.(ECE) VI semester .

Supervisor Head of the Department

ABSTRACT

The Solar power station uses the Sun's heat to make steam, and drive a generator to make electricity. The station looks a little like the Odellio solar furnace , except that the mirrors are arranged in -circles around the "power tower". As the Sun moves across the sky, the mirrors turn to keep the rays focused on the tower, where oil is heated to 3,000 degree Celsius, The heat from the oil is used to generate steam, which then drives a turbine, which in turn drives a generator capable of providing 10kW of electrical power. A large pressure tank, or “steam accumulator”, stores energy as pressurized hot water and allows the plant to continue generation in cloudy conditions for up to an hour. Solar power tower was very expensive to build, but as fossil fuels run out and become more expensive, solar power stations may become a better option.

CONTENT

1. Introduction

2. Methodology

3. Details

4. Results / Applications

5. Conclusions

6. Bibliography

INTRODUCTION:-

The sun's rays, or solar energy, have been used since the beginning of time and is vital to all living things. In addition to solar energy being a constant resource, heat and electricity are other forms of energy that can be made from solar energy. The largest advantage of solar energy is that it is a free and unlimited source of energy. Solar energy is also the cleanest energy source that does not compromise or add to global warming. The solar tower is a concept invented with an intention to generate efficient green energy. Resembling an inverted funnel in shape, the solar tower is a huge source for generating renewable energy. The technology is based on the concept developed by renowned German structural engineer Professor Jorge Schlaich. The most fantastic thing about this new technology is the simplicity of its design, and its ingenious use of basic principles of physics to create energy.

SOLAR POWER TOWER

System DESCRIPTION:

Solar power towers generate electric power from sunlight by focusing concentrated solar radiation on a tower-mounted HEAT EXCHANGER (RECEIVER). MANY SUN-TRACKING MIRRORS CALLED HELIOSTATS ARE USED TO REFLECT THE INCIDENT SUNLIGHT ONTO THE RECEIVER. UTILITY-SCALE APPLICATIONS IN THE 30 TO 400 MWE RANGE CAN USE THIS KIND OF TOWERS.

Molten-salt solar power tower:

In a molten-salt solar power tower, liquid salt at 290ºC (554ºF) is pumped from a Ëœcoldâ„¢ storage tank through the RECEIVER WHERE IT IS HEATED TO 565ºC (1,049ºF) AND THEN ON TO A ËŒHOT„¢ TANK FOR STORAGE. HOT SALT IS PUMPED TO A STEAM GENERATING SYSTEM WHEN POWER I NEEDED. THE HOT SALT PRODUCES SUPERHEATED STEAM FOR A CONVENTIONAL RANKINECYCLE TURBINE/GENERATOR SYSTEM.

Solar One. SOLAR TWO:

They are operating power tower plants. Solar One, which operated from 1982 to 1988, was the worldâ„¢s largest power tower plant.It made large scale power production with power towers was feasible. Here, water was converted to steam in the receiver and used DIRECTLY TO POWER A CONVENTIONAL RANKINE-CYCLE STEAM TURBINE. THE SOLAR ONE THERMAL STORAGE SYSTEM STORED HEAT FROM SOLAR-PRODUCED STEAM IN A TANK FILLED WITH ROCKS AND SAND USING OIL AS THE HEAT-TRANSFER FLUID.

The goals of the redesigned plant, called Solar Two, are to validate nitrate salt technology, to reduce the technical and ECONOMIC RISK OF POWER TOWERS, AND TO STIMULATE THE

COMMERCIALIZATION OF POWER TOWER TECHNOLOGY.

PRINCIPLE:- The solar updraft tower is a proposed type of renewable-energy power plant. It combines three old and proven technologies: the chimney effect, the greenhouse effect, and the wind turbine. Air is heated by sunshine and contained in a very large greenhouse-like structure known as collector, around the base of a tall chimney, and the resulting convection causes rising airflow to rise through the updraft tower. The air current from the greenhouse up the chimney drives turbines, which produce electricity. The generating ability of a solar updraft power plant depends primarily on two factors: the size of the collector area and chimney height. With a larger collector area, a greater volume of air is warmed to flow up the chimney; with a larger chimney height, the pressure difference increases the stack effect. The tower works on centuries-old tried-and-true principles of updraft. This is the same principles used for chimneys in open fire places. The reason our house doesn't fill up with smoke when we light a fire in our fireplace, is due to the suction created by the hot air rising up through the chimney. This pulls the smoke up through the chimney as well. But in the case of the solar tower, we are not using a fire to create hot air. We are simply allowing the sun to heat stuff up. In this case, the sun heats the air up, and the air rises through the solar chimney as a result.

The ground under the collector absorbs some of the radiated energy during the day and releases it into the collector at night. This enables solar towers to produce a significant amount of electricity throughout the night.

OVERVIEW

To date, the largest power towers ever built are the 10 MW Solar One and Solar Two plants. Assuming success of the Solar Two project, the next plants could be scaled-up to between 30 and 100 MW in size for utility grid connected applications in the Southwestern United States and/or international power markets. New peaking and intermediate power sources are needed today in many areas of the developing world. India, Egypt, and South Africa are locations that appear to be ideally suited for power tower development. As the technology matures, plants with up to a 400 MW rating appear feasible. As non-polluting energy sources become more favored, molten-salt power towers will have a high value because the thermal energy storage allows the plant to be dispatch able. Consequently, the value of power is worth more because a power tower plant can deliver energy during peak load times when it is more valuable. Energy storage also allows power tower plants to be designed and built with a range of annual capacity factors (20 to 65%). Combining high capacity factors and the fact that energy storage will allow power to be brought onto the grid in a controlled manner (i.e., by reducing electrical transients thus increasing the stability of the overall utility grid); total market penetration should be much higher than an intermittent solar technology without storage. One possible concern with the technology is the relatively high amount of land and water usage. This may become an important issue from a practical and environmental viewpoint since these plants are typically deployed within desert areas that often lack water and have fragile landscapes. Water usage at power towers is comparable to other Rankine cycle power technologies of similar size and annual performance. Land usage, although significant, is typically much less than that required for hydro [3] and is generally less than that required for fossil (e.g., oil, coal, natural gas), when the mining and exploration of land are included.

HISTORY:-

In 1903, Spanish Colonel of the Isadora Cabanyes first proposed a solar chimney power plant in the magazine La energía eléctrica.

One of the earliest descriptions of a solar chimney power plant was written in 1931 by a German author, Hanns Günther.

Beginning in 1975, Robert E. Lucier applied for patents on a solar chimney electric power generator; between 1978 and 1981 these patents (since expired) were granted in Australia, Canada, Israel, and the USA. For many years Professor Jorge Schlaich and his team at Schlaich Bergermann and Partner (SBP) of Stuttgart, Germany, have been vitally interested in large scale solar energy applications. In the late 1970’s and early 1980’s the team developed a detailed proposal for a Solar Tower. An experimental 50kW capacity pilot plant was then built to SBP’s design in Manzanares, Spain, some 50km south of Madrid, which collapsed in a sand storm after six years.

Diagram illustrating the principle:

WORKING:-

Air is heated by solar radiation under a low circular glass roof open at the periphery; this and the natural ground below it form a hot air collector. In the middle of the roof is a vertical tower with large air inlets at its base. The joint between the roof and the tower base is airtight. As hot air is lighter than cold air it rises up through the chimney. Suction from the tower then draws in more hot air from the collector, and cold air flows in from the outer perimeter. The solar radiation is responsible for causing a constant up-draught in the tower. The energy created through this process is converted into mechanical energy by the rising air passing through the pressure-staged wind turbines at the base of the tower, and into electrical energy by conventional generators. Moreover the ground below the collector absorbs solar energy during the day which is released at night, so that the rising air column is continuous.The Solar Tower can simplistically be likened to an inverted hydroelectric plant. The sun is analogous to rain (except it is more regular), the collector and ground storage analogous to dam, the tower analogous to the penstock and the turbines broadly similar to hydroelectric machines with air as the working fluid.

DESIGN ANALYSIS:-

TOWER:

The tower is a 1000m tall thin concrete shell of 120m internal diameter. It is based on a slab Foundation. Wall thickness at the top is expected to be around 30cm. The first 80m of the tower comprise 32 radial support buttresses (inlets) arranged circumferentially, between each of which is a single turbine exhaust duct. This represents a huge design and construction challenge that has required exacting studies especially with respect to wind loadings. The size and design of the slab foundation and the complex structural base of the tower is not only dependent on the wind loads but on the soil properties of the selected site that has been found to be geotechnically appropriate. However temperature loads and construction imperfections may contribute to induced stress and should all be carefully studied.

COLLECTOR:

The collector is essentially a very large circular greenhouse with a radius of 3500m designed to maximize the absorption and minimize the re-radiation of incident solar energy. The collector is open for the entry of ambient air at the periphery where the translucent surface is some 3.5m above the ground. At this point the air velocity is low and the air under the collector has adequate time to heat up by about 14°C on average, although the maximum temperature rise has been calculated at up to 46°C. The maximum design collector exit temperature at the turbine generators, where the roof rises to around 25m as it joins the tower, is calculated at 73°C and around 83°C at the tower base. The air temperature fallsprogressively up the tower due to expansion, not thermal loss through the walls.In terms of cost versus durability and optical properties, such as IR-reflection and light transmission, tempered glass is still preferred for the inner perimeter. Recent advances in polycarbonates and polymer materials that also require lighter support systems are proving an attractive technical and economic alternative for the outer collector perimeter. Design issues which impact on collector material economics at all radii include physical strength, transportability, storage ability, ease of erection, fastening details, drainage arrangements, hail resistance, joint air tightness, erection safety and handling and price.

TURBINE GENERATORS:

The horizontal axis turbines are arranged radially outside the tower support walls, equally spaced and concentric. This arrangement makes it easier to optimize machine layout with tower base design. 32 shrouded axial turbines are proposed for the 200MWe Solar Tower. The advantages claimed for shrouded turbines are greater power output for a given rotor diameter (up to 8 times with double the on-blade air velocity) and higher efficiency (up to 80% compared with 20% to a maximum of 30% for conventional open wind turbines). Individual turbine peak ratings of 6.25MWe would meet the 200MWe plant design output. Wind velocity over the turbine blade cross section will range between approximately 4m/s and 18m/s.

GENERATORS:

The generators proposed are 11kV synchronous machines with either static or brushless Excitation. Grid connection of the 32 Solar Tower generators will require step up transformers with on load tap changing facilities to meet voltage regulation and reactive power requirements. The control system will be simple and no unusual risks are foreseen.

SITE SELECTION:

The adequacy of solar radiation and proximity of power transmission infrastructure generally govern Solar Tower location. The following factors should be kept in mind while selecting the site for solar tower;

• Region should be non-cyclonic.• Region should be non-seismic.• Ideally with underlying rock strata for economic tower foundation design and adequate bearing safety and stability.• Not subject to excessive precipitation as hail or desert sandstorms.

TECHNICAL SPECIFICATIONS:

The following specifications are purposed for 200 MW Solar.

Solar Tower power plant rated capacity 200MW

Tower height 1000 meters

Tower internal diameter(constant over full height) 120 meters

Collector diameter 7000 meters

Number and configuration of turbine generators 32 units

Maximum continuous rating (MCR) of each turbine 6.25MW

Plant land usage 3800 hectares

SOME MORE APPLICATIONS OF SOLAR TOWER:-

The solar chimney could be constructed up a mountainside using inclined terrain for support; this could draw power from updraft out of a thermal inversion and improve urban air quality.

The inverse of the solar updraft tower is the downdraft-driven energy tower. Evaporation of sprayed water at the top of the tower would cause a downdraft by cooling the air and driving wind turbines at the bottom of the tower.

The solar distiller could adapt the collector-tower system to provide large-scale seawater desalination.

MERITS:

The Solar Tower has a number of advantages:

*Solar towers generate electricity without any negative environmental consequences.*The collector can use both direct and diffused solar radiation; this is in contrast to other major large-scale solar-thermal power plants that can only use direct radiation. *The collector provides storage for natural energy, at no additional cost. The ground under the glass roof absorbs some of the radiated energy during the day and releases it into the collector at night. This enables solar towers to produce a significant amount of electricity throughout the night.*Solar Towers are particularly reliable and not liable to break down, in comparison with other solar generation plants. Turbines, transmissions and generator are the plant’s only moving parts. This

simple and robust structure guarantees an operation that needs little maintenance, and of course no combustible fuel.

The building materials needed for solar towers, mainly concrete and glass, are available everywhere in sufficient quantities. In fact, with the energy taken from the solar tower itself and the stone and sand available in the desert; building materials can be produced on site.

Solar towers can be built now, even in less industrially developed countries. The industry level already available in most countries is entirely adequate for their requirements. Investment in a high-tech manufacturing plant is therefore not needed.

Even in poor countries it is possible to build a large plant without high foreign currency expenditure as their own resources and work-force can be utilized; this creates large numbers of jobs and dramatically reduces investment requirement and the cost of generating electricity.

DEMERITS:

Solar Towers can not convert the entire proportion of solar heat collected into electricity, but manages to compensate for this disadvantage by their cheap, robust construction and low maintenance costs. Solar Towers need large collector areas. For economically viable operation of solar electricity production plants it is essential they operate in regions with high solar radiation, this is not a fundamental disadvantage; as such regions usually have enormous deserts and unutilized areas.

COMPANIES BEHIND THE IMPLEMENTATION:

Siemens Energy is to supply an industrial steam turbine for one of the world’s first commercial solar tower power plants. The Spanish company Sener will build the innovative solar thermal power plant.Siemens is market leader for steam turbines for solar thermal power plants and has already secured orders for the supply of more than 40 of these specially adapted turbines. Unlike the Sener solar tower power plant, most of the solar power plants planned to date featured parabolic mirrors in a parallel configuration, which focus the solar radiation on piping.

CONCLUSION:

The solar tower can produce electrical generation in large-scale quantities and be a competitive alternative to coal and gas based electricity generation. Moreover, Solar Tower will produce an abundance of clean electricity by capitalizing on clean solar energy. Thus, it’s time to switch on to a new era of technology.

To conclude with the words of the great German poet Goethe:

“Whatever you can do, or dream you can do, begin it. Boldness has genius, power and magic in it.”

REFERENCES:

• www.enviromission.com.au • www.sciencedaily.com • Schlaich Bergermann and Partner (SBP), Homepage

http://www.sbp.de/home.sieve.html• www.indianenvironmentportal.com • www.naturalnews.com