POWER FROM THE SUN: PRINCIPLES OF HIGH TEMPERATURE SOLAR THERMAL TECHNOLOGY

ABSTRACT:
The research and development described in this document was conducted within the U.S. Department of Energy's Solar Thermal Technology Program. The goal of this effort is to advance the engineering and scientific understanding of solar thermal technology and to establish the technology base

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from which private industry can develop solar thermal systems for introduction into the competitive energy market. Solar thermal technology uses tracking mirrors or lenses to concentrate solar flux onto a receiver where the solar energy is absorbed as heat and converted into electricity or used directly by industry as process heat. The two primary solar thermal technologies, central receivers and distributed receivers, employ various point- and line-focus optics to concentrate sunlight. Current central receiver systems use fields of heliostats (two-axis tracking mirrors) to focus the sun's radiant energy onto a single tower-mounted receiver. Distributed receiver technology currently includes parabolic dishes, Fresnel lenses, parabolic troughs, and spherical bowls. Parabolic dishes up to 17 m in diameter track the sun on two axes and use mirrors to focus radiant energy onto a point-focus receiver. Troughs and bowls are line-focus tracking reflectors that concentrate sunlight onto receiver tubes along their focal lines. Distributed receiver concentrating collector modules can be used alone or in a multi-module system. The concentrated radiant energy absorbed by the solar thermal receiver is transported to the conversion process by a circulating working fluid. Receiver temperatures range from 100ºC in low temperature troughs to close to 1500ºC in dish and central receiver systems. The Solar Thermal Technology Program is directing efforts to advance and improve each system concept through the research and development of solar thermal materials, components, and subsystems, and the testing and performance evaluation of subsystems and systems. These efforts are carried out through the technical direction of the U.S. Department of Energy and its network of national laboratories that work with private industry. Together they have established a comprehensive, goal-directed program to improve performance and provide technically proven options for eventual incorporation into the nation's energy supply

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