solar chimney power plant

The Solar Chimney Power Plant

Contents:1. Introduction2. The Solar Chimney

a. Parts of the Solar Chimney i. Collectorii. Turbinesiii. Chimney

b. Working Principles of Solar Chimneyc. Technology

3. The Mildura Solar Chimney

4. Advantages

5. Disadvantages

6. Conclusion

Contents:

1.Introduction:In many parts of the world , there is a growing awareness that some alternative energy sources could have an important role to play in the production of electricity.

However , only the solar energy represents totally nonpolluting inexhaustible energy resource that can be utilized economically to supply Man’s energy needs for all time.

Fig. 1 The Prototype Manzanares Solar Chimney.

There are lots of methods of using the solar energy , and the Solar Chimney

is one of them, which can be seen below, in figure.

2.The Solar Chimney

In 1978, it was suggested by Professor Schlaich of Stuttgart university that power could be produced by a hybrid solar system. The solar chimney system consists of three parts; The collector , turbines and the chimney.

2.a. Parts of the Solar Chimney2.a.i. The CollectorCollector is the part , which is used to absorb hot air. It is usually 5-6 meters high and covers a very large area about thousands of m² as seen in fıgure.

Fig. 2 The Collector.

Collector

• There is no limitation for the surface area. The larger the area, the more energy generated from the chimney.

• Covering materials may be different, such as; glass, plastic film or glazed collector.The most efficient one is glazed collector.It can convert up to 70% of irratiated solar energy into heat a typical annual average is 50%. Also, with proper maintenance, its life span can easily be 60 years or more.

2.a.ii. Turbines

Turbines, seen in figure, are used to convert air to the mechanical energy.

Fig. 4 Turbine for Solar Chimney Power Station .

Turbines are placed horizontally in chimney.In order to obtain maximum energy from the warmed air,turbines blades should cover all the cross-sectional area of the chimney.

To do this,one big turbine or a few small turbines should be used in chimney, as can be seen from the figure 5. and figure 6.

Fig. 5 Turbine with large diameter. Fig. 6 Small turbines.

2.a.iii. The chimney

The most important part of the plant is the chimney,seen in fıgure 7. It acts as a thermal engine.

Chimney

Fig. 7 The chimney.

• Longer the chimneys height, the more the energy produced from the chimney.

• The efficiency of the chimney does not depend on the amount of the temperature rising, but depends on the outside temperature.

Thus, efficiency is directly proportional to the ratio between the height of the chimney and the outside temperature.

There are two types of different chimneys using for the plant. Free standing chimneys and guyed tubes (Figure 8. and figure 9. ) .

The life span of a free standing chimney is longer than that of the guyed tubes. It lasts about a hundred years, while the guyed tubes’ is much shorter.

Although, the efficiency is proportional to the height of the chimney, there is a limitation in practice.

Fig. 8 Fig. 8 Free-standing.Free-standing. Fig.Fig. 9 9 Guyed Tubes. Guyed Tubes.

2.b. Working principles of Solar Chimney

• Solar chimney consists of large area of transparent covers which receive solar radiations.• The cold air flows from the bottom of the chimney due to natural draught produced due to density difference of high density surrounding cold air & low density hot air below the transparent covers heated by the solar energy.

Fig. 10 Transparent roof .

•It is called chimney draught.

•The flow rate of air depends on the draught produced due to density difference of cold and hot air and the height of the chimney.

•Inside the chimney, turbines with electric generator,produce electricity.

Fig. 11 Schematic seen of the solar chimney

2.c. Technology•Solar chimneys are large-scale power plants with an output of 5 to 200 MW each.

•A 100 MW plant will produce about 750 GWh/year.

•For that the glass roof has to be several kilometers in diameter and the tube has to be as high as possible to achieve a large annual output.

3.The Mildura Solar ChimneyThe 1000m Solar Chimney in Mildura, Australia, is the highest man-made structure on Earth, and can produce 200MW of electricity, providing power to 200,000 homes.Schematic seen of a construction of a chimney is in figure 14.

Fig. 14 Construction of a chimney.

•The cost to build the tower is estimated at $395 million. (About 14 percent more than an equivalent coal-fired power station, and about 70 percent more per installed megawatt than a comparable wind farm).

• The Australian government target of producing 2% of energy from renewable sources by 2010 (9500 GigaWatt hours) could be met easily.

4.AdvantagesSolar chimney power stations are particularly suitable for generating electricity in deserts and sun-rich wasteland. It provides electricity 24 hour a day from solar energy alone.No fuel is needed. It needs no cooling water and is suitable in extreme drying regions.

It is particularly reliable and a little trouble-prone compared with other power plants.The materials concrete, glass and steel necessary for the building of solar chimney power stations are everywhere in sufficient quantities. No ecological harm and no consumption of resources.

5.DisadvantagesSome estimates say that the cost of generating electricity from a solar chimney is 5x more than from a gas turbine. Although fuel is not required, solar chimneys have a very high capital cost. The structure itself is massive and requires a lot of engineering expertise and materials to construct.

6.ConclusionSolar chimney power stations could make important contributions to the energy supplies in Africa, Asia and Australia, because there is plenty of space and sunlight available there.

It is very important for the future, because our resources are limited, except our sun.

THE END