Abstract :
This paper explores the thermodynamic limits of solar thermal systems using absorber surfaces with high angular
selectivity. It shows that theoretical considerations regarding the behavior of non-concentrating solar thermal systems
are not enough in themselves to rule out their use in high-temperature applications. In fact, the paper demonstrates that
the maximum theoretical thermal efficiency of a non-concentrating system may equal that of a concentrating system if
the monochromatic directional emittance of its absorbing surface is sufficiently restricted. It is thus confirmed that the
fundamental parameter that determines the ability of a solar-energy system to operate at high temperatures is not
optical concentration, but angular selectivity of emittance.
2004 Published by Elsevier Ltd
