Seminar on

The Solar ChimneyPresented By:

Arup Kumar SikdarRoll No – ME/MHPE/02/14

Topic to be Discuss1. Introduction2. The Solar Chimney

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

b. Working Principles of Solar Chimneyc. Technology

3. Cost5. Advantages6. Disadvantages7. Conclusion

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.

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 1.

Fig. 1 The Prototype Manzanares Solar Chimney [2].

2.a. Parts of the Solar Chimney2.a.i. 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.

Fig. 2 The Collector [2].

Collector

Turbines, seen in figure 4, are used to convert air current to the mechanical energy. Turbines are placed horizontally in chimney, vertically in the collector.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. 4 Turbine for Solar Chimney Power Station [2].

2.a.ii. Turbines

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

The most important part of the plant is the chimney,seen in fıgure 7. It acts as a thermal engine. Since the friction loss is minimum in the chimney it likes a pressure tube.Longer the chimneys height, the more the energy produced from the chimney.The efficiency of the chimney is not depend on the amount of the temperature rising, but depends on the outside temperature.Thus, efficiency directly proportional to the ratio between the height of the chimney and the outside temperature. [5]

Chimney

Fig. 7 The chimney [2].

2.a.iii. The chimney

2.b. Working principles of Solar Chimney

Transparent roof, which is seen in fıgure 10, 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 fıgure 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 [6].

Fig. 10 Transparent

roof [4].

Fig. 11 Schematic seen of the solar chimney [6]

Heat Output

Collector Area Solar Radiation

Specific heat capacity of the air

Mass flow

Collector Efficiency

The temperature differences between the collector and out flow

Air speed at collector outflow

Specific dendsity of air at temperature To + ΔT at collector outflow

Chimney cross-section area

2.c. Technology•Solar chimneys are large-scale power plants with an output of 5 to 200 MW each [4].•A 100 MW plant will produce about 750 GWh/year at 2.300 kWh/m² global horizontal radiation [4].•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 [4]. •The turbines are basically more closely related to the pressure-staged hydroelectric turbines than to the speed-stepped wind turbines. Therefore they have been developed and designed in collaboration with hydroelectric power plant manufacturers [4].• The turbine’s life span is based on its resistance to rapid pressure and speed changes of the air [5].

4.Cost“With the support of construction companies, the glass industry and turbine manufacturers a rather exact cost estimate for a 200 MW solar chimney could be compiled. We asked the utility "Energie Baden Württemberg" to determine the energy production costs compared to coal- and combined cycle power plants based on equal and common methods” [8]. (Table. 1).

Fig. 13 Energy production costs from solar chimneys, coal and combined cycle power plants depending on the interest rate [8].

6.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.

7.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 [2]. The structure itself is massive and requires a lot of engineering expertise and materials to construct [2].

8.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 [2].It is very important for the future, because our resources are limited, except our sun.