There are three types of concentrating solar power (CSP) technology: trough, parabolic-dish and power tower.9 Trough and power tower technologies apply primarily to large, central power generation systems, although trough technology can also be used in smaller systems for heating and cooling and for power generation. The systems use either thermal storage or back-up fuels to offset solar intermittency and thus to increase the commercial value of the energy produced.
The conversion path of concentrating solar power technologies relies on four basic elements: concentrator, receiver, and transport-storage and power conversion. The concentrator captures and concentrates solar radiation, which is then delivered to the receiver. The receiver absorbs the concentrated sunlight, transferring its heat to a working fluid. The transport-storage system passes the fluid from the receiver to the power-conversion system; in some solar-thermal plants a portion of the thermal energy is stored for later use.
The inherent advantage of CSP technologies is their unique capacity for integration into conventional thermal plants. Each technology can be integrated in parallel as "a solar burner" to a fossil burner into conventional thermal cycles. This makes it possible to provide thermal storage or fossil fuel backup firm capacity without the need of separate back-up power plants and without disturbances to the grid. With a small amount of supplementary energy from natural gas or any other fossil
9 CSP is used interchangeably with solar thermal power. D 0.72 per kWh by 2050.
fuel, solar thermal plants can supply electric power on a steady and reliable basis. Thus, solar thermal concepts have the unique capability to internally complement fluctuating solar burner output with thermal storage or a fossil back-up heater.
The efficiency and cost of such combined schemes, however, can be significant. Current costs are about USD 0.10 per kWh and are expected to fall to about USD 0.72 per kWh by 2050. This technology relies on small-scale gas-fired power plants with low efficiency (40-45%), compared to 500-MW centralized plants with efficiencies of 60%. If the efficiency loss is allocated to the hybrid scheme, the economics would be less encouraging.
Fresh impetus was given to solar thermal-power generation by a Spanish law passed in 2004 and revised in 2005. The revised law provides for a feed-in-tariff of approximately EUR 0.22 (USD 0.27) per kWh for 500 MW of solar thermal electricity. In several states in the United States and in other countries, the regulatory framework for such plants is improving. At present, solar plant projects are being developed in Spain (50 MW), in Nevada in the United States (68 MW) and elsewhere. Two U.S. plants will also be constructed in southern California under the state's Renewable Portfolio Standard. A 500 MW solar thermal plant, expected to produce 1,047 GWh, is due for completion in 2012.
There is a current trend toward combining a steam-producing solar collector and a conventional natural gas combined-cycle plant. Projects in Algeria and Egypt, currently at the tendering stage, will combine a solar field with a combined-cycle plant. There are also plans to add a solar field to an existing coal plant in Australia. On a long-term basis, the direct solar production of energy in transportable chemical fuels, such as hydrogen, also holds great promise.
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Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.