Tuesday, 20 December 2011

:. Solar Power Generation Station.:


Introduction

Sensible technology for the wide use of renewable energy must be simple and reliable, accessible to the technologically less developed countries that are sunny and often have limited raw materials resources. It should not need cooling water and it should be based on environmentally sound production from renewable or recyclable materials.

The solar tower meets these conditions. Economic appraisals based on experience and knowledge gathered so far have shown that large scale solar towers ( ≥ 100 MW) are capable of generating electricity at costs comparable to those of conventional power plants (Badenwerk and EVS, 1997). This is reason enough to further develop this form of solar energy utilization, up to large, economically viable units. In a future energy economy, solar towers could thus help assure the economic and environmentally benign provision of electricity in sunny regions.

The solar updraft tower’s three essential elements – solar air collector, chimney/tower, and wind turbines - have been familiar for centuries. Their combination to generate electricity has already been described in 1931 (Günther, 1931). Haaf (1983, 1984) gives test results and a theoretical description of the solar tower prototype in Manzanares, Spain. Transferability of the results obtained in Manzanares is discussed by Schlaich et al. (1990).

The same author provides an overview (Schlaich 1995). Kreetz (1997) introduces the concept of water-filled bags under the collector roof for thermal storage. Gannon and V. Backström (2000) present a thermodynamic cycle analysis of the solar tower, and also an analysis of turbine characteristics (v. Backström and Gannon 2003). Ruprecht et al. (2003) give results from fluid dynamic calculations and turbine design for a 200 MW solar tower. A thermal and technical analyses targeting computer-aided calculation is described by dos Santos Bernardes et al. (2003).


Generation Process

1.    The solar power tower is a system that uses many solar reflectors called heliostats to reflect the energy of the sun to a central tower.

2.    The generating ability of a solar updraft power plant depends primarily on two factors: the collector area and the chimney height. With a larger collector area, a greater volume of air is warmed to flow up the chimney; collector areas as large as 7 kilometres (4.3 mi) in diameter have been considered. With a larger chimney height, the pressure difference increases the stack effect; chimneys as tall as 1,000 metres (3,281 ft) have been considered.

3.    Heat can be stored inside the collector area greenhouse to be used to warm the air later on. Water, with its relatively high specific heat capacity, can be filled in tubes placed under the collector, increasing the energy storage as needed.

4.    Turbines can be installed in a ring around the base of the tower, with a horizontal axis, as formerly planned for the Australian project and seen in the diagram above; or—as in the prototype in Spain—a single vertical axis turbine can be installed inside the chimney.

5.    Carbon dioxide is emitted only negligibly  while operating, but is emitted more significantly during manufacture of its construction materials, particularly cement. Net energy payback is estimated to be 2–3 years.

6.    A solar updraft tower power station would consume a significant area of land if it were designed to generate as much electricity as is produced by modern power stations using conventional technology. Construction would be most likely in hot areas with large amounts of very low-value land, such as deserts, or otherwise degraded land.

7.    A small-scale solar updraft tower may be an attractive option for remote regions in developing countries. The relatively low-tech approach could allow local resources and labour to be used for its construction and maintenance.

8.    The turbine turns a shaf that rotate a series of magnate (rotor) past coper coils (stator) in a generator to create electricity. From the power hause, transmission carry electricity to communities.

Advantages and Disadvatages


Advantages

1.    Particularly suitable for generating electricity in deserts and sun-rich wasteland.

2.    It provides electricity 24 hour a day from solar energy alone.

3.    It is particularly reliable and a little trouble-prone compared with other power plants.

4.    The materials concrete, glass and steel necessary for the building of solar chimney power stations are everywhere in sufficient quantities.

5.    Greatly reduced pollution. Having much better credentials than fossil fuel for polluting emissions, the environmental costs of manufacturing and constructing than solar energy appliances.

6.    Greatly reduced contribution to global warming. No carbon dioxide, methane or other emissions that warm the atmosphere. Again, manufacturing and installation of solar appliances are necessarily accompanied by some of those emissions.

7.    Infinite energy resource. Solar energy is not a finite resource as fossil fuels are. While the sun is up there it constantly produces all the energy we can use.

8.    No fuel is needed. It needs no cooling water and is suitable in extreme drying regions.

9.    Reduced maintenance costs. Power facilities are in place, no fuel or lubricants need to be supplied.

10. Falling production costs. The financial costs of producing appliances such as solar cells and solar hot water panels are falling as technology develops. Comparatively solar energy is competing with fossil fuels as fossil fuel prices have risen steeply globally in the last few years. Solar energy technology is becoming increasingly efficient.

11. Low running costs. With prices of traditional fuels solaring the cost advantages of solar energy are becoming obvious. After installation of the appliance, solar energy is free.

12. Local application. Suitable for remote areas that are not connected to energy grids. Fossil-fuel poor countries can kick their dependency on this energy and spend their funds on other things through application of solar energy.

Disadvantages

1.    Some 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.

3.    It is available most abundantly in areas with a high number of sunshine hours. Cold countries in high northern or southern latitudes, it is less easily captured    and used.

4.    It is not directly available at night or under cloud cover and conversion into another.

5.    DC power is produced by solar cells which must be converted to AC power before it can be used.

6.    Initial installation cost may be too pricey for consumers.

7.    Solar panels require large land/roof areas to be effective.





















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