Research on an increase of PV-efficiency and electrical power output by means of a reduction in operating cell temperature has been carried out by the author since 1989 in a Ph. D. thesis (see Krauter 1993c).
The energy consumption of an active cooling system would not be compensated by the gain in increased energy generation, at least for small systems. Operational temperatures were kept at low levels by mounting the module on a water-filled tank. This allowed for an effective reduction in operating cell temperatures without spending any energy for refrigeration. The water virtually soaks up the heat flow generated by the module. Due to the high thermal capacity of the incorporated water (Cpwater= 1,254 kJ K-1) the temperature increases gradually (see also results below). Also, the peak temperature is shifted from midday to afternoon. The principle was proven and validated with different prototypes in Europe and in Africa built over previous years.
History – The first cooling device which followed the “cooling by an extended heat capacity” concept was built in 1992. The tank was integrated into the original framing of an M55 PV module by SSI (former Siemens Solar Industries, now Shell Solar) with a volume of 12 liters, so it could be used with conventional mounting. This prototype provided a 2.6% increase in the daily electrical energy yield. Subsequent tests, which utilized latent heat storage material (sodium sulphate), showed significantly better results but caused severe corrosion (see Krauter 1993c).