Apparatus or devices using heat produced by exothermal chemical reactions other than by combustion.
Use of solar heat and solar heat collectors.
Parabolic, Hemispherical, Semi-cylindrical, Cylindro-parabolic, Conical, Flat plates, Spaced solar heat collectors
Solar heat systems using thermosiphonic circulation
Natural heat - Geothermal heat & devices for producing mechanical power from geothermal energy