Electricity plays a significant role in daily life and is the main component of countless applications. Thus, ongoing research is necessary to improve the existing approaches, or find new approaches, to enhancing power generation. The thermoelectric generator (TEG) is among the notable and widespread technologies used to produce electricity, and converts waste energy into electrical energy using the Seebeck effect. Due to the Seebeck effect, temperature change can be turned into electrical energy; hence, a TEG can be applied whenever there is a temperature difference. The present paper presents the theoretical background of the TEG, in addition to a comprehensive review of the TEG and its implementation in various fields. This paper also sheds light on the new technologies of the TEG and their related challenges. Notably, it was found that the TEG is efficient in hybrid heat recovery systems, such as the phase change material (PCM), heat pipe (HP), and proton exchange membrane (PEM), and the efficiency of the TEG has increased due to a set of improvements in the TEG’s materials. Moreover, results show that the TEG technology has been frequently applied in recent years, and all of the investigated papers agree that the TEG is a promising technology in power generation and heat recovery systems.

Energy has become the backbone of humanities daily activities. Heating, ventilating, and air conditioning systems (HVAC), which consume around 39% of energy in the residential sector, have turned into an essential constituent for providing fresh air, especially after COVD-19, not only in hospitals but also in any simple construction. Thus, decreasing this percentage or recovering part of the energy lost is an essential issue in today’s energy management scenarios. In this context, the present manuscript suggests a comprehensive review, classifications, critical analysis, and potential recommendations for energy recovery in air conditioning systems. It classifies energy recovery into two main categories: using lost energy for external uses, such as heating domestic water, or with other devices; and using lost energy for internal uses, such as the hot airflow which can be reused again for increasing efficiency of HVAC. In addition, this paper presents a summary of previous research and undertakes a review of the devices used for recovering energy. Furthermore, this review identifies superior devices in terms of climate and weather conditions. These objectives are accomplished by investigating around 190 published papers to conclude that energy recovery devices show a considerable effect on energy consumption in HVAC, mainly the heat pipe, fixed plate, and rotary wheel devices.

One of the most promising solution for the current energy crisis is recovering lost energy. Indeed, in many energy systems the percentage of energy loss could exceed 60%. To put it another way, in some applications, recovering energy is as much beneficial as finding new source of energy. Moreover, finding new concepts of energy recovery offers wider horizons to reduce energy consumption. The present work investigates new energy recovery system that combines heat recovery and energy generation using thermoelectric generators (TEG). The proposed system is a triple Thermoelectric-Energy recovery coupled system that from one hand allows to recover the heat of condenser and to reuse the lost energy of exhaust airflow of HVAC all-air system and from the other hand it permits to produce green electricity using TEG. The air of the condenser is considered the heat source, whereas the exhaust air flow is utilized as cooler. To proceed, a mathematical tool is first developed it allows to thermally simulate TEGs for different boundary conditions. The heat and cold source are then modeled where the heat transfer coefficient is determined from the Nusselt number. Furthermore, a parametric analysis is then conducted to evaluate the power generated with the new concept when the air velocity of the exhaust airflow and that of the condenser vary. It is shown that for a space cooling load of 100 kW, a 40×40 cm2 flat plate is capable to generate 90 W of electrical power