With the growing concerns about environmental pollution, climate change, and the global fossil energy crisis, research and development of renewable clean energies has received more attention. The sun as one of the renewable energy sources is the most potent source for human kind. This is because the solar radiation that reaches the Earth surface is about 1.2 × 10 5 TW, which is far greater than the energy consumed by humans [1,2].The most common way to utilize solar energy is to convert it into two easily harnessed forms; electricity and thermal energy. Apart from photovoltaic (PV) which can convert solar radiations to electricity directly, thermal energy also can be converted to electricity, and one promising method is utilizing the thermoelectric generator (TEG). Thermoelectric (TE) devices have many advantages such as gas-free emissions, solid-state operation, maintenance-free operation without any moving parts and chemical reactions, vast scalability, a long life span of reliable operation and no damage to the environment. Therefore, the combination of PV and TE could be considered to produce more electricity.Combining a photovoltaic module and a solar thermoelectric generator would enable photons outside the range of a particular solar cell's narrow absorption wavelength to be directed to the TE modules which generates electricity by the thermoelectric effect. Doing this would allow energy conversion efficiency to be increased while simultaneously reducing the heat dissipated by the PV module. This paper presents a detailed review of the current state of art in solar photovoltaic-thermoelectric hybrid system for electricity generation. It begins with the analysis of the groundwork and feasibility of PV-TE system. An overview of the two main types and Review

Nomenclature r radius, mm angle of a single thermoelectric leg, degree half of the angle between two legs, degreeHigh performance and thermal stress analysis of a segmented annular thermoelectric generator

Thermal management of photovoltaic cells is an essential research objective for increasing the conversion efficiency of the photovoltaic. Flat plate heat pipe is a passive cooling device capable of effectively reducing the solar cell temperature. Therefore, this study presents a numerical investigation of a hybrid photovoltaic-thermoelectric system with and without a flat plate heat pipe. A detailed comparative analysis of the electrical performance of the photovoltaic only, photovoltaic-thermoelectric and photovoltaic-thermoelectric-heat pipe systems is performed. The influence of solar concentration ratio, ambient temperature, wind speed and thermoelectric generator cold side temperature on the efficiency and power output of the photovoltaic only and hybrid photovoltaic-thermoelectric systems are studied using COMSOL 5.4 Multiphysics software. A three-dimensional finite element study is carried out and temperature dependent thermoelectric material properties are considered to increase the simulation accuracy. Results show that the photovoltaic-thermoelectric-heat pipe efficiency is 1.47% and 61.01% higher compared to that of the photovoltaic-thermoelectric and photovoltaic only systems respectively at a concentration ratio of 6. In addition, the photovoltaic-thermoelectric-heat pipe is recommended for highly concentrated systems because of its superior performance. Furthermore, the photovoltaic-thermoelectric system is a better alternative to the photovoltaic only system because of its enhanced performance which is second only to that of the photovoltaic-thermoelectric-heat pipe system. Results also show that ineffective cooling of the thermoelectric generator can adversely affect the performance of the hybrid systems. This study will proper valuable information on the feasibility of hybrid photovoltaic-thermoelectric systems with and without heat pipe. Finally, the three-dimensional nature of this study makes it very useful in understanding the actual temperature distribution in the hybrid systems.

Effective thermal management of photovoltaic cells is essential for improving its conversion efficiency and increasing its life span. Solar cell temperature and efficiency have an inverse relationship therefore, cooling of solar cells is a critical research objective which numerous researchers have paid attention to. Among the widely adopted thermal management techniques is the use of thermoelectric generators to enhance the performance of photovoltaics. Photovoltaic cells can convert the ultra-violent and visible regions of the solar spectrum into electrical energy directly while thermoelectric modules utilize the infrared region to generate electrical energy. Consequently, the combination of photovoltaic and thermoelectric generators would enable the utilization of a wider solar spectrum. In addition, the combination of both systems has the potential to provide enhanced performance due to the compensating effects of both systems. The waste heat produced from the photovoltaic can be used by the thermoelectric generator to produce additional energy thereby increasing the overall power output and efficiency of the hybrid system. However, the integration of both systems is complex because of their opposing characteristics thus, effective coupling of both systems is essential. This review presents the concepts of photovoltaics and thermoelectric energy conversion, research focus areas in the hybrid systems, applications of such systems, discussion of the most recent research accomplishments and recommendations for future research. All the essential elements and research areas in hybrid photovoltaic/thermoelectric generator are discussed in detailed therefore, this review would serve as a valuable reference literature.

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