Thermoelectric systems are solid-state devices that convert heat into electricity or electricity into heat, offering potential for cooling, heating, and power generation. They can compete with fluid-based systems like air conditioners and heat pumps, and are used in small-scale applications such as car seats, night vision systems, and electrical enclosure cooling. However, widespread adoption requires improving material efficiency and system design. Thermoelectric devices are solid-state heat engines that use electrons as a working fluid, unlike traditional systems that use two-phase fluids. The Peltier and Seebeck effects are key to their operation, with the Seebeck effect enabling power generation from temperature differences. The figure of merit ZT measures efficiency, with higher ZT values indicating better performance. Current ZT values are around 1.0, but research has achieved ZT values up to 3.2, with potential for further improvements through nanotechnology and material optimization. Efficiency gains can also be achieved through improved thermodynamic cycles and system designs, such as the Brayton cycle analog, which enhances performance by optimizing each element along the thermal gradient. Alternative junction geometries reduce parasitic losses, improving efficiency. TE systems are already used in various applications, including infrared imaging, DNA analysis, and vehicle cooling. Future applications could include room, home, and commercial heating and cooling systems, replacing refrigerants with electric current. Higher ZT values could enable waste-heat recovery and primary power generation, reducing fossil fuel use and emissions. TE technology has the potential to address sustainability issues by providing efficient, environmentally friendly solutions for energy conversion and management. Despite challenges in efficiency and cost, ongoing research and development are making TE systems more viable for broader applications.Thermoelectric systems are solid-state devices that convert heat into electricity or electricity into heat, offering potential for cooling, heating, and power generation. They can compete with fluid-based systems like air conditioners and heat pumps, and are used in small-scale applications such as car seats, night vision systems, and electrical enclosure cooling. However, widespread adoption requires improving material efficiency and system design. Thermoelectric devices are solid-state heat engines that use electrons as a working fluid, unlike traditional systems that use two-phase fluids. The Peltier and Seebeck effects are key to their operation, with the Seebeck effect enabling power generation from temperature differences. The figure of merit ZT measures efficiency, with higher ZT values indicating better performance. Current ZT values are around 1.0, but research has achieved ZT values up to 3.2, with potential for further improvements through nanotechnology and material optimization. Efficiency gains can also be achieved through improved thermodynamic cycles and system designs, such as the Brayton cycle analog, which enhances performance by optimizing each element along the thermal gradient. Alternative junction geometries reduce parasitic losses, improving efficiency. TE systems are already used in various applications, including infrared imaging, DNA analysis, and vehicle cooling. Future applications could include room, home, and commercial heating and cooling systems, replacing refrigerants with electric current. Higher ZT values could enable waste-heat recovery and primary power generation, reducing fossil fuel use and emissions. TE technology has the potential to address sustainability issues by providing efficient, environmentally friendly solutions for energy conversion and management. Despite challenges in efficiency and cost, ongoing research and development are making TE systems more viable for broader applications.