Photovoltaics (PVs) are an effective technology to harvest the solar energy and satisfy the increasing global electricity demand. The effectiveness and life span of PVs could be enhanced by enabling effective thermal management. The conversion efficiency and surface temperature of PVs have an inverse relationship, and hence the cooling of PVs as an emerging body of work needs to have attention paid to it. The integration of a thermoelectric generator (TEG) to PVs is one of the widely applied thermal management techniques to improve the performance of PVs as well as combined systems. The TEG utilizes the waste heat of PVs and generate the additional electric power output. The nanofluid enables superior thermal properties compared to that of conventional cooling fluids, and therefore the performance of photovoltaic/thermal–thermoelectric generator (PV/T-TEG) systems with nanofluid cooling is further enhanced compared to that of conventional cooling. The TEG enables a symmetrical temperature difference with a hot side due to the heat from PVs, and a cold side due to the nanofluid cooling. Therefore, the symmetrical thermal management system, by integrating the PV/T, TEG, and nanofluid cooling, has been widely adopted in recent times. The present review comprehensively summarizes various experimental, numerical, and theoretical research works conducted on PV/T-TEG systems with nanofluid cooling. The research studies on PV/T-TEG systems with nanofluid cooling were reviewed, focusing on the time span of 2015–2021. This review elaborates the various approaches and advancement in techniques adopted to enhance the performance of PV/T-TEG systems with nanofluid cooling. The application of TEG with nanofluid cooling in the thermal management of PVs is an emerging research area; therefore, this comprehensive review can be considered as a reference for future development and innovations.

The rapidly growing commercialization of electric vehicles demands higher capacity lithium-ion batteries with higher heat generation which degrades the lifespan and performance of batteries. The currently widely used indirect liquid cooling imposes disadvantages of the higher thermal resistance and coolant leakage which has diverted the attention to the direct liquid cooling for the thermal management of batteries. The present study conducts the experimental investigation on discharge and heat transfer characteristics of lithium-ion battery with direct liquid cooling for the thermal management. The 18,650 lithium-ion cylindrical battery pack is immersed symmetrically in dielectric fluid. The discharge voltage and capacity, maximum temperature, temperature difference, average temperature, heat absorbed, and heat transfer coefficient are investigated under various conditions of discharge rates, inlet temperatures, and volume flow rates of coolant. The operating voltage and discharge capacity are decreasing with increase in the volume flow rate and decrease in the inlet temperature for all discharge rates. At the higher discharge rate of 4C, the lowest battery maximum temperatures of 60.2 °C and 44.6 °C and the highest heat transfer coefficients of 2884.25 W/m2-K and 2290.19 W/m2-K are reported for the highest volume flow rate of 1000 mLPM and the lowest inlet temperature of 15 °C, respectively.

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Electric vehicles (EVs) are incorporated with higher energy density batteries to improve the driving range and performance. The lithium-ion batteries with higher energy density generate a larger amount of heat which deteriorates their efficiency and operating life. The currently commercially employed cooling techniques are not able to achieve the effective thermal management of batteries with increasing energy density. Direct liquid cooling offers enhanced thermal management of battery packs at high discharging rates compared to all other cooling techniques. However, the flow distribution of coolant around the battery module needs to be maintained to achieve the superior performance of direct liquid cooling. The objective of the present work is to investigate the heat transfer characteristics of the lithium-ion battery pack with dielectric fluid immersion cooling for different fin structures. The base structure without fins, circular, rectangular and triangular fin structures are compared for heat transfer characteristics of maximum temperature, temperature difference, average temperature, Nusselt number, pressure drop and performance evaluation criteria (PEC). Furthermore, the heat transfer characteristics are evaluated for various fin dimensions of the best fin structure. The heat transfer characteristics of the battery pack with dielectric fluid immersion cooling according to considered fin structures and dimensions are simulated using ANSYS Fluent commercial code. The results reveal that the symmetrical temperature distribution and temperature uniformity of the battery pack are achieved in the case of all fin structures. The maximum temperature of the battery pack is lower by 2.41%, 2.57% and 4.45% for circular, rectangular, and triangular fin structures, respectively, compared to the base structure. The triangular fin structure shows higher values of Nusselt number and pressure drop with a maximum value of PEC compared to other fin structures. The triangular fin structure is the best fin structure with optimum heat transfer characteristics of the battery pack with dielectric fluid immersion cooling. The heat transfer characteristics of a battery pack with dielectric fluid immersion cooling are further improved for triangular fin structures with a base length -to -height ratio (A/B) of 4.304. The research outputs from the present work could be referred to as a database to commercialize the dielectric fluid immersion cooling for the efficient battery thermal management system at fast and higher charging/discharging rates.