A holistic review on the integration of heat pipes in solar thermal and photovoltaic systems

Solar energy is a potential clean source of energy to meet our thermal and electrical energy demands but its penetration is hindered by the factors such as intermittency of solar radiation, lower thermal efficiency, and capital requirement for the solar energy systems. Improving the thermal performance of the solar collectors and effectively collecting the thermal energy from photovoltaic panels can pave the way to promote clean energy utilization. Heat pipe, being a passive energy system with a high heat transfer rate ability, can aid in ameliorating the performance of solar collectors as well as photovoltaic panels. This review study is proposed to discuss the theoretical and experimental aspects of the design and integration of heat pipes with various solar applications including solar thermal, freshwater production, and photovoltaic-thermal systems. In addition, numerical models relevant to heat pipe and solar energy systems are highlighted. An elaborate analysis of various influencing factors on the thermal performance of heat pipe integrated solar energy systems is also presented. The critical observations from experimental aspects are elucidated, and the future scope of heat pipe systems are also substantiated. This review encourages the selection of a particular heat pipe and the heat transfer enhancement method to attain higher energy conversion rate and the productivity corresponding to various solar energy systems.