01-06-2013, 12:36 PM
The Solar Chimney
Solar Chimney.ppt (Size: 952 KB / Downloads: 92)
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.
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 namely;
The collector,
The turbines and
The chimney.
Parts of the Solar Chimney
The Collector
Collector is the part, which is used to produce hot air by green-house effect. It is usually 5-6 meters high and covers a very large area about thousands of m² as seen in fıgure 2.
Since glazing increases the mass of the roof, glazed collectors should have stronger rods and should be attached as in figure 3.
There is no limitation for the surface area. The larger the area, the more energy generated from the chimney.
There should be slightly increasing height towards to the chimney in order to obtain minimum friction loss.
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.
Working principles of Solar Chimney
Transparent roof,which is seen in fıg10, admits the short wave solar radiation component and retains long-wave radiation from the heated ground.Thus,when solar radiation pass through the transparent roof it is absorbed by the ground elements and it converts into heat energy. Since air is heated, it starts to rise up and move towards to chimney,seen in fıg 11.Also, it gains velocity.
Heated air enters the chimney placed at the center of the roof and creates an up draught there. Inside the chimney, turbines with electric generator, produce electricity.
The Mildura Solar Chimney
Solar Chimney in Mildura, Australia, will be 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.
The base of the tower will be between 170 to 200 metres. The chimney is basically a very simple tube with wall thickness of 25cm, diameter of 150m and a height of 1000m. The collector roof will be 5000m in diameter.
Conclusion
Solar 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.