SOLAR POWER TOWER123.docx (Size: 50.09 KB / Downloads: 111)
Solar thermal power tower
The Solar power station uses the Sun's heat to make steam, and drive a generator to make electricity. The station looks a little like the Odellio solar furnace , except that the mirrors are arranged in -circles around the "power tower".
As the Sun moves across the sky, the mirrors turn to keep the rays focused on the tower, where oil is heated to 3,000 degree Celsius, The heat from the oil is used to generate steam, which then drives a turbine, which in turn drives a generator capable of providing 10kW of electrical power. A large pressure tank, or “steam accumulator”, stores energy as pressurized hot water and allows the plant to continue generation in cloudy conditions for up to an hour.
Solar power tower was very expensive to build, but as fossil fuels run out and become more expensive, solar power stations may become a better option.
The Solar thermal power tower (also knows as 'Central Tower' power plants or 'Heliostat' power plants or power towers) is a type of solar furnace using a tower to receive the focused sunlight. It uses an array of flat, moveable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the target). The high energy at this point of concentrated sunlight is transferred to a substance that can store the heat for later use. The more recent heat transfer material that has been successfully demonstrated is liquid sodium. Sodium is a metal with a high heat capacity, allowing that energy to be stored and drawn off throughout the evening. That energy can, in turn, be used to boil water for use in steam turbines. Water had originally been used as a heat transfer medium in earlier power tower versions (where the resultant steam was used to power a turbine). This system did not allow for power generation during the evening. Their obvious advantages include that they w the sun for fuel and they do not pollute. Current studies predict commercial plants sized between 100 and 200 megawatts could supply power at a cost competitive with other sources. A 200- megawatt plant generates enough power for a city of about 200,000 people. The availability of efficient, low cost storage is a key advantage of power towers.
To date, the largest power towers ever built are the 10 MW Solar One and Solar Two plants. Assuming success of the Solar Two project, the next plants could be scaled-up to between 30 and 100 MW in size for utility grid connected applications in the Southwestern United States and/or international power markets. New peaking and intermediate power sources are needed today in many areas of the developing world. India, Egypt, and South Africa are locations that appear to be ideally suited for power tower development. As the technology matures, plants with up to a 400 MW rating appear feasible. As non-polluting energy sources become more favored, molten-salt power towers will have a high value because the thermal energy storage allows the plant to be dispatch able. Consequently, the value of power is worth more because a power tower plant can deliver energy during peak load times when it is more valuable. Energy storage also allows power tower plants to be designed and built with a range of annual capacity factors (20 to 65%). Combining high capacity factors and the fact that energy storage will allow power to be brought onto the grid in a controlled manner (i.e., by reducing electrical transients thus increasing the stability of the overall utility grid); total market penetration should be much higher than an intermittent solar technology without storage. One possible concern with the technology is the relatively high amount of land and water usage. This may become an important issue from a practical and environmental viewpoint since these plants are typically deployed within desert areas that often lack water and have fragile landscapes. Water usage at power towers is comparable to other Rankine cycle power technologies of similar size and annual performance. Land usage, although significant, is typically much less than that required for hydro  and is generally less than that required for fossil (e.g., oil, coal, natural gas), when the mining and exploration of land are include