SOLAR UPDRAFT TOWER PLANT

Contents INTRODUCTION.

MAIN COMPONENTS.

WORKING.

THEORY.

HEAT STORAGE UNDER COLLECTOR.

ELECTRICITY GENERATION COST.

ADVANTAGES.

DISADVANTAGES.

RECENT DEVELOPMENTS.

PROTOTYPE.

CONCLUSION

INTRODUCTIONThe present energy production is damaging the environment and is non- sustainable.Remedy- building of nuclear power plant

Unacceptable risk. High cost. Less availability of nuclear fuel.

Solar updraft tower Sensible technology.Uses renewable energy. Accessible to the technologically less

developed countries.An updraft solar power plant utilizes a combination of solar air collector and central updraft tube to generate electricity.

MAIN COMPONENTS

THE COLLECTOR

THE TOWER

THE TURBINE

SCHEMATIC DIAGRAM

THE COLLECTOR Usually 2 -6 meters height from ground. Top surface is covered by glass or plastic film glazing. Opened at its periphery for continuous air flow. Height of the collector is more towards the base of the tower. Heating effect increased by green house effect. Water filled black tubes are used for additional thermal storage. Stored thermal energy in the water tubes can be used during the night (24 hr power generation).

HEAT STORAGE UNDERNEATH COLLECTOR

THE TOWER Tower is a pressure tube with low friction loss.Efficiency of the plant is proportional to the tower height.Updraft of air in the tower is approximately proportional to rise of air temperature in the collector.Air velocity at the bottom of tower reaches about 15m/s.

THE TURBINEShrouded pressure staged turbine.Static pressure is converted to rotational energy.Speed of air before and after turbine is almost same.Output is proportional to product of change in pressure and volume flow per unit time.There is no much change in velocity of air.Maximum output obtained when pressure drop at turbine is 80% of total pressure drop.

WORKINGAir is heated by solar radiation.Heated air moves towards the tower.The pressure energy of air is increased at the base of the tower.The pressure energy is converted to rotational energy in the turbine. keeping the velocity almost constant.The turbine is coupled to electric generator.The low density air moves upwards in the tower and escapes through the opening.fresh air moves in through the periphery to the collector.

PICTORIAL VIEW OF WORKING

THEORYThe amount of heat obtained Q = Gh * Acollector = ma * Cpa* ∆T Gh is the insolation factor.

The pressure difference created

∆p=g * ( ℘a-℘c) ∫dH. integral is from 0 to Hc. (Hc is the tower height)Power developed P=∆p * Vair * Area.If the pressure difference is completely used for accelerating the air then By using modified Torricelli equation

Vair.max=√(2 * g * Hc * [∆T/To])Kinetic energy generated E=1/2 ma (Vair.max)²Efficiency η=(power/heat supplied)

=g * H/Cp * To

ELECTRICITY GENERATION COST

PROTOTYPEEstablished in 1981-82 in Manzanares .Fund was provided by German Ministry of Research and Technology.Worked for 7 years on experimental basis.Main dimensions and technical data of the Manzanares prototype .

PROTOTYPE IN MANZANARES

ADVANTAGES

Renewable source of energy is used.

Continuous energy is available.Maintenance is less.No pollution.Unlike other power plants no cooling water is required.Simple design.Raw material needed for construction are easily available.

DISADVANTAGES

Requires large areas of flat land.

Not adequate for earthquake prone areas.

Areas with frequent sand storms should be avoided.

RECENT DEVELOPEMENTS

A solar tower plant with 200MW capacity is

about to be constructed in Australia.

Estimated to provide power to 2,00,000

homes

Estimated to keep 3,80,000 tons of

greenhouse gases out of the atmosphere

annually.

Weather patterns at four sites in U.S are

under studies.

CONCLUSION

Works on a simple proven principle.

As thermodynamic efficiency of plant increases

with tower height, such plants have to be large to

become cost competitive.

No consumption of costly fossil fuels. Especially

beneficial for developing countries.

No ecological harm .

The plant consists of concrete and glass which are

made from sand and stone. thus they can be even

constructed in desert areas.