A downhole heat exchanger is a heat exchanger that transfers ambient thermal energy or geothermal energy to a working fluid. It consists of plastic pipes installed vertically or inclined in a borehole.
A subsurface collector is a heat exchanger that transfers ambient thermal energy to a working fluid. It consists of plastic pipes laid horizontally under the ground.
An energy converting component is an artificial object that is usually a discrete part of an energy transformation unit with the function of transforming, transferring or changing a certain type of energy.