1. alien-not contained in or deriving from the essential nature of something; an economic theory alien to the spirit of capitalism; the mysticism so foreign to the French mind and temper; jealousy is foreign to her nature. foreign.
1 the quality of being hot; hotness: in physics, heat is considered a form of energy existing as the result of the random motion of molecules and is the form of energy that is transferred between bodies as a result of their temperature difference.  much hotness; great warmth: stifling heat.
Definition of Solar Heating. What Is Solar Heating? Solar heating refers to the renewable energy system that collects energy from the sun in the form of heat rather than using the sunâs energy to produce electricity, as is the case with solar photovoltaics. Solar heating systems can be used to provide space heating and water heating to be used in residential, commercial, or industrial facilities.