Abstract
This paper investigates the transient performance of a DC compressor fridge incorporated with Phase Change Material (PCM) for weak/off-grid setting regions. A photovoltaics (PV) module is directly connected to the DC compressor without use of batteries and inverter, in order to simplify the system and reduce its cost. The DC compressor speed can be adjusted according to the radiation intensity for an optimum match between PV output and the efficiency of refrigeration. During the daytime, the PCM is charged for cold storage by refrigeration; when solar radiation is weak or during the night, the PCM releases cooling to maintain the required cabinet temperature. A transient mathematical model is built for the whole system including PV module, DC compressor refrigeration system, fridge cabinet and PCM packs. The model is coded and solved in MATLAB while CFD method is used to produce some additional information. The simulations are conducted to evaluate the effect of solar radiation intensity, thermostat setting and the number of PCM packs on the fridge refrigeration performance. Moreover, the study aims to investigate and present benefits of incorporating PCM with a direct PV powered DC compressor fridge in weak/off-grid setting areas. When the fridge cabinet temperature varies between 4℃ and –2℃, the average COP of the fridge refrigeration system was found 1.7 for high solar radiation day due to the high rotation speed of the compressor, but for low solar radiation day, the average COP was calculated as 1.95. The analysis also shows that a variable speed DC compressor can keep the foods in the desired temperature range for two days of power outage by using 1 m<sup>2</sup> PV module and 3.6 kg of thin PCM packs.
Highlights
Electricity is the most important energy source for residential populations to maintain comfort and health in everyday life
4.1 CFD analysis for heat transfer coefficient The study aims to find out the impact of the amount of Phase Change Material (PCM) placed in the cabinet on performance of a fridge operating in standard conditions
The PCM packs are placed in the fridge and air temperature is at uniform 0°C and PCM temperature is assumed as the same with the air temperature initially
Summary
Electricity is the most important energy source for residential populations to maintain comfort and health in everyday life. 590 million people did not have access to electricity in Sub Saharan Africa (SSA) and 240 million in India in 2016. The number of people decreased for India from 2000 to 2016, the population who cannot access electricity is increasing in SSA (International Energy Agency IEA 2019). As a result of this, food spoilage is a significant problem facing Africa/developing countries. Cities in many SSA countries face the combined problems of rising temperatures and inadequate power supply. They do not have access to reliable electricity, if at all, and do not have proper refrigeration/air conditioning systems since existing technologies require higher quality grid electricity
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