an energy technology that continues to meet current and future energy demands without risking longterm human or environmental health machinery and equipment developed from the application of scientific knowledge and used for practical purposes the energy of an object due to the random motion of its particles (a.k.a. heat) to move energy from one object or system to another object or system to change energy from one form or type to another form or type * \"The work done on a system is equal to the change of energy of that system."