|
Solar Thermal Power Plant The benefits of solar power are compelling; the fuel is free, abundant and inexhaustible. In fact in just 1 year, six times as much useable solar energy hits the Earth as there is in total reserves from non-renewable sources. It is environmentally friendly, aids in the diversification of our fuel and energy supply, and is rapidly deployable.
Technology for Generating Electricity
Thermal energy generated by using Concentrated Solar Power, generate high temperature working fluid to drive either an organic rankine cycle power block that includes a turbine and generator or other thermally driven engines.
Advantages of Concentrated Parabolic Trough Technology Over Non-Renewable Fuels
The primary advantage of the Concentrated Solar Power parabolic trough over non renewable technologies is that it is environmentally responsible using an emission free fuel source. Non-renewable technologies, require a renewed fuel source, which is diminishing at an alarming rate, andare anything but environmentally benign.
Concentrated Solar Power Plant Using Parabolic Trough Design
Where temperatures below about 95oC are sufficient, as for space heating,flat-plate collectors of the nonconcentrating type are generally used. The fluid-filled pipes can reach temperatures of 150 to 220 degrees Celsius when the fluid is not circulating. This temperature is too low for efficient conversion to electricity.
The efficiency of heat engines increases with the temperature of the heat source. To achieve this in solar thermal energy plants, solar radiation is concentrated by mirrors or lenses to obtain higher temperatures — a technique called Concentrated Solar Power (CSP). The practical effect of high efficiencies is to reduce the plant's collector size and total land use per unit power generated, reducing the environmental impacts of a power plant as well as its expense.
As the temperature increases, different forms of conversion become practical. Up to 600oC, steam turbines, standard technology, have an efficiency up to 41%. Above this, gas turbines can be more efficient. Higher temperatures are problematic because different materials and techniques are needed. One proposal for very high temperatures is to use liquid fluoride salts operating between 700oC to 800oC, using multi-stage turbine systems to achieve 50% or more thermal efficiencies. The higher operating temperatures permit the plant to use higher-temperature dry heat exchangers for its thermal exhaust, reducing the plant's water use — critical in the deserts where large solar plants are practical. High temperatures also make heat storage more efficient, because more watt-hours are stored per unit of fluid.
Since the CSP plant generates heat first of all, it can store the heat before conversion to electricity. With current technology, storage of heat is much cheaper and more efficient than storage of electricity. In this way, the CSP plant can produce electricity day and night. If the CSP site has predictable solar radiation, then the CSP plant becomes a reliable power plant. Reliability can further be improved by installing a back-up system that uses fossil energy. The back-up system can reuse most of the CSP plant, which decreases the cost of the back-up system.
With reliability, unused desert, no pollution (so long as gas turbines aren't used)and no fuel costs, the obstacles for large deployment for CSP are cost, aesthetics,land use and similar factors for the necessary connecting high tension lines. Although only a small percentage of the desert is necessary to meet global electricity demand, still a large area must be covered with mirrors or lenses to obtain a significant amount of energy. An important way to decrease cost is the use of a simple design.
|
