Conversion efficiency in solar thermal systems
The viability of solar thermal power systems depends on how effectively they convert sunlight into a useful form of energy. Relative to many human needs, the solar power reaching the earth per unit area is small. Large collector surfaces are needed; in addition, for many utilization schemes, it is desirable to increase the intensity of the radiant flux incident on active absorbers by using concentrators. When the collected sunlight is reflected or refracted onto an absorber surface which is smaller than the collector surface, radiative and convective losses are lowered and the system has the potential to produce more work. This potential depends on the ability of the designer to lower the resistance to heat transfer between the absorbing surface and the working fluid. Low thermal resistance may be even more important for high temperature applications: those applications may be simply not feasible if the resistance is not low enough. This thesis discusses the thermal performance of several systems, and the dependence of this performance on concentration, thermal resistance, and coolant flow rates. Various realistic solar plant configurations have been evaluated, where different optical systems reflect light upon absorbers cooled by a variety of means. Results are obtained in terms of the operating temperatures at which collected solar energy can be most efficiently converted to work. The dependence of the optimum operating temperature on the resistance to thermal heat transfer between the surface temperature and the working fluid at a given concentration is also analyzed. The improvements in the overall system performance achieved using enhanced heat removal schemes by nonconventional means (direct absorption in solid particles or liquids, heat pipes, etc.) from the absorber surface are shown to be necessary for the attainment of very high temperatures.
- Research Organization:
- Massachusetts Univ., Lowell, MA (United States)
- OSTI ID:
- 6158104
- Resource Relation:
- Other Information: Ph.D. Thesis
- Country of Publication:
- United States
- Language:
- English
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SOLAR ABSORBERS
HEAT TRANSFER
PERFORMANCE
SOLAR POWER PLANTS
EFFICIENCY
VIABILITY
CONCENTRATORS
ENERGY CONVERSION
SOLAR COLLECTORS
WORKING FLUIDS
CONVERSION
ENERGY TRANSFER
EQUIPMENT
FLUIDS
POWER PLANTS
SOLAR EQUIPMENT
140700* - Solar Thermal Power Systems
141000 - Solar Collectors & Concentrators