Modeling and Simulation of a Photovoltaic Powered Vapour Compression Refrigeration System

Abstract

This paper presents a mathematical model of a solar vapour compression refrigeration system. The system consists of a D.C. vapour compression refrigerator, a controller that prevents the battery from being over charged or deep-discharged, a D.C inverter which converts direct current from the solar photovoltaic panel or the battery into alternating current that can be fed to the  refrigerator’s compressor, a battery to store and supply energy when the sun is not available and a photovoltaic (PV) generator which supplies power to the refrigerator and charges the battery with excess energy. The different components of the system are modeled, the output from one component becoming the input to the next component. The significance of the resulting photovoltaic powered vapour compression refrigeration is to develop a computer model and simulation for a photovoltaic powered refrigeration system and MatLab is used to simulate the system performance. The simulation gives the system relationship between the freezer temperatures that can be attained and incident solar radiation on the solar PV panel using different solar panels. The battery size required to run the system for a maximum period of 12 hours was derived. It was determined that as the system voltage increased, the battery size required to run the system decreased. The current-voltage and power-voltage characteristics of the KC65T PV panel by Kyocera were studied. It was observed that the open circuit voltage (voltage produced when the PV panel’s terminals, shorting it out) increased linearly. This behavior indeed showed that a PV cell behaves more like a current source than a voltage source. It was also observed that the power at MPP (maximum power point) increased with increasing solar insolation while the V_mp (Voltage at MPP) remained constant at 14.2 volts irrespective of the level of incident solar insolation. This finding suggested that for any particular solar PV panel model, maximum power can be obtained at a particular voltage (14.2 volts in this case), when working at any given solar insolation level. The current at maximum power, I_mp was observed to increase with increasing solar insolation.

Keywords: photovoltaic system, vapour compression refrigeration, inverter, solar photovoltaic panel, solar energy and insolation, solar cells and battery.