Thermodynamic limitations to solar energy conversion

Solar energy is heat of 5800 K. Any system converting solar energy in mechanical. chemical or electrical energy is a heat engine. The second principle of thermodynamics stating that entropy cannot be destroyed limits the efficiency of solar energy conversion to 0.93 for reversible operation. In addition, it is recognized that processing the incident solar energy current is not possible without the generation of entropy. This sets an upper limit of 0.86 for maximally concentrated solar radiation. Several processes which allow to achieve this limit are discussed and how they can possibly be realised in photovoltaic solar energy conversion. (C) 2002 Elsevier Science B.V. All rights reserved.