The present disclosure relates to thermoelectric devices useful for a range of thermoelectric applications (e.g., high temperature thermoelectric generation, fluid conditioning). Thermoelectric devices may include one or more heat exchangers (e.g., coolant heat exchanger(s)) and one or more thermoelectric layers adjacent to the heat exchanger(s). An enclosure may surround the thermoelectric layer(s) and heat exchanger(s), providing a barrier from outside fluid (e.g., hot fluid flow). The enclosure may conduct heat between the outside surroundings and the thermoelectric layer(s). The heat exchanger(s) may be spaced from and movable or slidable relative to the enclosure, which may accommodate for certain thermal expansion effects. The enclosure may include a conformable surface adapted to conform substantially to the shape of the thermoelectric layer(s) (e.g., when a vacuum is applied). One or more thermally conductive members (e.g., fins) may extend from the conformable enclosure. Various embodiments of a thermal switch are also described.