PV power operation of a solar driven cooling compressor cluster - Battery charging level controlled PV electric energy self-consumption
Abstract
A 24 V (voltage) DC driven cooling compressor cluster of two parallel compressors of (Comp1) 1.6 kWp and (Comp2) 2.5 kWp cooling power was integrated in a simple cold distribution system for room cooling. A battery and a sensible cold storage allow room cooling in periods of no solar irradiation. The cold distribution is performed through capillary tubes in a cubic duct. The air flow in the duct is sustained through gravitational force i.e. natural convection. To start one of compressors of the cluster the requirement of the min. DC power from the PV field is at least 30 %-50 % of the maximum electric power needed. The compressor cluster operation is battery charging level controlled. A coincidence of available PV power and compressor cluster electric power consumption is in most of the time reached. But at high battery charging level ( >75% of max. level) and low PV power the coincidence is interrupted by a switch on of the second compressor to discharge the battery to a level range of 65 % -75 %. Nevertheless a 90 % direct self-consumption of the PV electric energy is reached by the solar compressor cooling system.