Review of cooling techniques using phase change materials for enhancing efficiency of photovoltaic power systems

A significant fraction of the solar radiation falling on photovoltaic (PV) panels gets converted into heat thus reducing the efficiency of photovoltaic power plants. Generally the performance of PV panels falls by 0.5% for every degree rise in temperature, depending on the type of solar cells used. The temperature regulation of PV power systems therefore becomes important especially for areas experiencing consistently high temperatures to improve PV efficiency. The objective of the study is to review literature on photovoltaic cooling techniques using phase change materials (PCM) including PV-thermal systems and building integrated photovoltaic systems. The main aim is to identify important research areas to ensure reliable performance and commercially viability of the technology. Various parameters are required to be evaluated and optimized for the geographical location of interest to obtain the best output. Increase in electrical efficiency as high as 5% is observed with PV-PCM integrated systems. Study suggests that inorganic PCMs have a good potential for PV cooling. PCM based PV systems will be cost effective only for areas with high insolation year round with less inter-seasonal climatic variations. However, poor thermal conductivity and large undercooling are major problems associated with PCM. There are only few studies on performance testing, economic benefit identification, increase in PV panel lifetime and LCA analysis for testing the suitability of PCM as coolant for PV panels. In this study the research gaps are identified for follow up work. Market review suggests that PCM based PV cooling technology is not yet commercialized due to its inefficiency primarily because of technological challenges, high system costs and non availability of reliable operating designs. The study suggests that PCM is still not an economic cooling technique for PV systems and further research is required.