heat or thermal reservoir for thermal engine to transfer and use heat energy.

 reservoir reserves heat. thermal engine works between two reservoirs by transferring the heat..

ground source heat pump - very costly to setup.

air source heat pump (ASHP) - 

vapor-compression refrigeration - for cooling houses and hot water.

Air-to-water heat pump - for heating rooms.

Electric heat pump water heaters are significantly more efficient than electric resistance water heaters, but also more expensive to purchase.

hot engine coolant to heat a vehicle using waste heat from industries and environment.

Thermal energy storage (TES) is achieved with widely different technologies. Depending on the specific technology, it allows excess thermal energy to be stored and used hours, days, months later, at scales ranging from the individual process, building, multiuser-building, district, town, or region.