Manuel De Souza
Concentrated Solar Power – (CSP) Explained
Concentrated Solar Power (CSP) is the most forward thinking innovative concept currently being used in the Solar Power Industry. Here we will explain the benefits, technology and the real world applications of this major move forward in sustainable alternative energy.
Concentrating solar power (CSP) technologies produce electricity by using concentrated sun rays to heat a medium (usually a liquid or gas) that is then used in a heat engine process (steam or gas turbine) to drive an electrical generator. CSP uses only the beam component of solar radiation (direct normal irradiance), and so its maximum benefit tends to be restricted to a limited geographical range.
The Technology behind the Scenes:
Like nearly all other current means of producing electricity, concentrated solar power ultimately involves heating a fluid. The three main CSP technologies are the parabolic trough, the solar tower and the dish/engine system. The parabolic trough works by concentrating the suns solar rays 70 to 100 times via parabolic curved solar reflectors onto a heat absorber a fluid-filled metal tube enveloped in glass, receiver. The solar collectors track the sun continuously. The absorbed solar radiation warms up the fluid to almost 400C and, through a heat exchanger, produces steam to drive turbines and generate power. Solar Central Tower systems have a single receiver placed on top of a tower. Hundreds of mirrors (heliostats) placed around the tower track the sun, redirecting and focusing the solar radiation onto the receiver.
The heat collected is used to drive steam turbines, which generate power. Pointfocus CSP systems like the central tower can generate higher temperatures than troughs (over 1 000°C). Dish/engine systems use parabolic dishes to capture solar radiation and transfer it to a so called Stirling engine placed in the focus of the dish. This engine uses the heat to expand and contract a fluid or gas and drive a turbine to produce power, with a typical output of about 10 to 15 kWe from each Stirling engine.
A typical parabolic trough power plant uses long rows of parabolic reflectors, with a land requirement of about 20 000m2 for a capacity of 1 MWel or 1km2 for a typical 50 MW plant. Trough concentrators and central receivers also need relatively flat land (less than 1% slope). Alternative heat-transfer fluids, such as steam and molten salt, are being studied to enable higher temperatures to be achieved and to increase efficiency. The use of molten salt eliminates the need for expensive heat exchangers and allows the solar field to operate at higher temperatures.
Care must be taken to ensure the molten salts do not freeze in the pipes at night.
An important aspect of CSP is the ability to store the heat temporarily, to smooth out dips and interruptions in output due to clouds, etc. Storage media include molten salt, steam accumulators, solid ceramic particles and high temperature concrete. The heat can currently be stored for 20 minutes to one hour designed for 6 to 7.5 hours of full-load storage, which is enough to allow operation into the evening when peaks in demand occur.
Research spending on Concentrated Solar Power
This has been relatively limited until recently (86 million in 2007), as interest is only now starting to grow. As the potential for concentrated solar power plants is greatest around the Mediterranean, public R&D support is dominated by Italy and Spain (about 75% of EU Member State funding), while Germany contributes another 18% because of its technological skills in this field. EU support under FP6 reached 20 million, while corporate investment has been estimated at around 50 million, accounting for some 56% of overall spending. Capital investments could be reduced by 25% to 35% with the technological innovations that are being explored.
About the Author
Sol Solar Power Co., Ltd. is a world-leading manufacturer of high-performance solar power products. The company sells its products to solar manufacturers worldwide, who assemble and integrate solar cells into modules and systems that convert sunlight into electricity for residential, commercial, and utility-scale power generation
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Manuel De Souza
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