July 11, 2007 A new test facility that aims to cut the cost of large-scale solar thermal energy production has been inaugurated at Almería in southern Spain. Research scientists from Europe’s largest solar energy research institute, the Fraunhofer Institute for Solar Energy Systems, helped to develop the facility which uses a linear Fresnel reflector one hundred meters long to focus sunlight onto a steel absorber tube in which water is heated up to 450 degrees Celsius and used to drive electricity producing turbines. Finding more efficient ways to harness the sun’s rays is a key part of the shift towards renewable energy and solar thermal power, as one of the most efficient methods currently under development, is predicted to provide about 10% of the world's electricity by 2050.
Fresnel reflectors are a low-cost alternative to the use of expensive parabolic mirrors as a means of concentrating the suns rays.
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“We anticipate that half the global energy requirement will be met from sustainable sources such as wind, water and solar power by 2050” states Professor Eicke Weber, director of the Fraunhofer ISE in Freiburg. “Linear Fresnel reflectors are cheaper than parabolic mirrors, take up less space and are less sensitive to the wind,”
A linear Fresnel reflector power plant uses a series of long, shallow-curvature (or sometimes flat) mirrors to focus light onto one or more linear absorbers positioned above the mirrors.
Prototypes have been built elsewhere in the world including the Solarmundo project in Belgium, which was the precursor to the new pilot plant in Spain. In Australia a prototype known as the Compact Linear Fresnel Reflector (CLFR) is under development at the Liddell power station in the Hunter Valley in New South Wales.
Three different types of large scale solar thermal technologies are being developed around the world: the solar tower approach, which uses flat plate reflectors to focus to a central point which can be heated to temperatures up to 800°C; the linear Fresnel approach and parabolic trough technology which has been implemented on a large scale in California and also uses linear focusing techniques.
The linear Fresnel approach aims improve on weaknesses found in parabolic trough systems by providing greater cost effectiveness through cheaper and larger mirrors that are not affected by wind, eliminating the need for a heat exchanger because of direct steam generation and reducing maintenance costs.
The demonstration plant in Almería was designed by Weber’s team in collaboration with other research groups, including scientists from the DLR, under a contract to MAN Ferrostaal Power Industry GmbH, whose goal it is to commercialize linear Fresnel collectors for use in solar thermal power stations.
The plant’s inauguration marks the beginning of comprehensive practical tests which it is hoped will lead to the construction of commercial solar thermal power plants using this technique.
For further reading see the Solar Power Group website and The Fraunhofer Institute for Solar Energy Systems ISE.