Journal of Solar Energy Engineering

Journal of Solar Energy Engineering

J. Sol. Energy Eng. / Volume 128 / Issue 2 / TECHNICAL BRIEFS

Analysis of Potential Conversion Efficiency of a Solar Hybrid System With High-Temperature Stage

J. Sol. Energy Eng.  -- May 2006 --  Volume 128,  Issue 2, 258 (3 pages)
http://dx.doi.org/10.1115/1.2189865

Author(s):
Y. V. Vorobiev
CINVESTAV-Querétaro, Libramiento Norponiente 2000, Querétaro 76230, QRO, México

J. González-Hernández
CIMAV, Miguel de Cervantes 120, Chihuahua 31109, México

A. Kribus
Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel

The analysis is given of hybrid system of solar energy conversion having a stage operating at high temperature. The system contains a radiation concentrator, a photovoltaic solar cell, and a thermal generator, which could be thermoelectric one or a heat engine. Two options are discussed, one (a) with concentration of the whole solar radiation on the PV cell working at hightemperature and coupled to the high-temperature stage, and another (b) with a special PV cell construction, which allows the use of the part of solar spectrum not absorbed in the semiconductor material of the cell ("thermal energy") to drive the high-temperature stage while the cell is working at ambient temperature. The possibilities of using different semiconductor materials are analyzed. It is shown that the demands to the cell material aredifferent in the two cases examined: in system (a) with high temperature of cell operation, the materials providing minimum temperature dependence of the conversion efficiency are necessary, for another system (b) the materials with the larger band gap are profitable. The efficiency of thermal generator is assumed to be proportional to that of the Carnot engine. The optical and thermal energy losses are taken into account, including the losses byconvection and radiation in the high-temperature stage. The radiation lossesimpose restrictions upon the working temperature of the thermal generator in the system (b), thus defining the highest possible concentration ratio. The calculations made show that the hybrid system proposed could be both efficient and practical, promising the total conversion efficiency around 25–30  % for system (a), and 30–40  % for system (b).

©2006 American Society of Mechanical Engineers

History:	Received 20 September 2005; revised 30 September 2005
Digital Object Identifier	http://dx.doi.org/10.1115/1.2189865