What is Waste heat?
'''Waste heat''' is the [[by-product]] [[heat]] of [[machine]]s and technical [[wikt:process|processes]] for which no useful application is found. A fraction of input [[energy]] is always [[Energy conversion|converted]] to heat by [[friction]] between machine parts and other processes such as liquid friction (see: [[viscosity]]). Mechanical drives can be designed to run smoothly, with little loss of energy to heat. Machines for [[energy conversion|conversion of energy]] contained in fuels to [[mechanical work]] or [[electric energy]] produce large amounts of waste heat (see: [[Second law of thermodynamics]]). This waste heat can be re-used if a [[cogeneration]] system is used. It is hard to use waste heat because it is difficult to transport the heat to another place, and it is difficult to store the heat for use at another time. In electrification of waste heat, [[organic matter]] can be used as a working medium to produce electricity on much lower temperatures compared to the [[water steam cycle]]. {{physics-stub}} [[Category:Heat]] [[Category:Energy]] [[Category:Waste]]