A comparative study of solar photovoltaic operated milk cooler for realizing the need for load management and starting circuits

Abstract

A study on the working characteristics of a variable speed DC compressor for variable solar irradiance has been carried out. Two compressors (total cooling capacity of 300 W) were directly connected to the solar photovoltaic (PV) panel, with both having the ability to start when solar irradiance reached 700 W/m2. When individually connected, the minimum solar irradiance required for a single compressor to start and run were 400 W/m2 and 200 W/m2. However, when two compressors in the loop were at rest, and when the solar irradiance was just above 400 W/m2, it was not sufficient to start both compressors. As a result, single compressor only began to run and another one took more time to start. Thus, a load management circuit is necessary for starting and sustaining the load for two compressors. A starting circuit is essential for the supply of the required starting current so that the single compressor and double compressors can start with the minimum irradiance of 200 W/m2 and 400 W/m2 respectively. Lab test (LTs) were performed using a regulated DC power supply (RPS) for the same test conditions as the field tests (FTs). The PV output was predicted using the PVsyst software and fed into the RPS. The results reveal the discrepancies in the behavioral characteristics of the DC compressors between FT and LT conditions.