Comparative study of the performances of four photovoltaic/thermal solar air collectors.

An extensive investigation of the thermal, electrical, hydraulic and overall performances of flat plate photovoltaic/thermal (PV/T) air collectors has been made. Four popular designs are considered with the air flowing either over the absorber (Model I) or under it (Model II) and on both sides of the absorber in a single pass (Model III) or in a double pass fashion (Model IV). Heat balance equations are written for each model and are numerically solved, incorporating measured climate data. The effects of air specific flow rate and the selectivity of the absorber plate and PV cells on the performances have been examined. It is found that under similar operational conditions, the Model I collector has the lowest performance, while the other models exhibit comparable thermal and electrical output gains. Nevertheless, the Model III collector demands the least fan power, followed by Models IV and II. It is also shown that selective properties are inappropriate for these PV/T collectors due to the resultant reduction in the generated PV energy, especially at low flow rates. The study provides valuable information regarding the design and operation of such types of PV/T air collectors.