New technology cuts the price of solar energy
Not only are fossil energy sources dwindling, but burning them produces greenhouse gases. “That’s why we must look to regenerative energies in future,” states Professor Eicke Weber, director of the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg. “We anticipate that half the global energy requirement will be met from sustainable sources such as wind, water and solar power by 2050.” The most important source of energy will always be the sun: The amount of solar energy that reaches Earth in a single hour is theoretically sufficient to supply the whole of humanity for a year. All we need to do is harness it – but even today, that still poses a tremendous technical challenge. In sunny countries, it is worthwhile building large-scale solar thermal power plants in whose solar fields thermo-oil is heated. A heat exchanger is used to create steam that drives a turbine to generate electricity. Up to now, engineers have used gigantic parabolic mirrors that focus the sunlight on a central absorber tube. Fresnel reflectors represent a low-cost alternative. Flat mirrors arrayed in long rows are so aligned that, with the aid of a small secondary mirror, they focus the sunlight on a linear tube running along the row of mirrors. Water is vaporized directly in this tube and heated up to 450 degrees Celsius at high pressure. “Linear Fresnel reflectors are cheaper than parabolic mirrors, take up less space and are less sensitive to the wind,” states Weber. In his opinion, this means the technology has a good chance of gaining wide-scale market acceptance. The demonstration plant in Almería was designed by Weber’s team in collaboration with other prestigious research groups, including scientists from the DLR, under a contract to MAN Ferrostaal Power Industry GmbH. The plant’s inauguration marks the beginning of comprehensive practical tests. If the linear Fresnel reflectors pass muster, they can be used in the construction of commercial solar thermal power plants. MAN Ferrostaal AG With a workforce of 4300 and an annual turnover of 1.4 billion euros (2006), MAN Ferrostaal AG, Essen, is the MAN Group’s industrial service provider. MAN Ferrostaal’s “Projects” and “Services” divisions serve customers in over 60 countries around the world. MAN Ferrostaal is a subsidiary of MAN Aktiengesellschaft, Munich. The MAN Group is one of Europe’s leading vehicle, motor and machine construction companies, reporting an annual turnover of roughly 13 billion euros. MAN employs some 50,000 people worldwide. Fraunhofer-Gesellschaft The Fraunhofer-Gesellschaft is the leading organization for applied research in Europe. Its research activities are conducted by 56 Fraunhofer Institutes at over 40 different locations throughout Germany. The Fraunhofer-Gesellschaft employs a staff of around 12,400, who work with an annual research budget totaling 1.25 billion euros. Roughly two thirds of this sum is generated through contract research on behalf of industry and publicly funded research projects. Branches in the USA and Asia serve to promote international cooperation.
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