Abstract: In an installation for harnessing thermal energy, in which in a first part of an operating cycle the working fluid is positively displaced out of a first chamber into a second chamber, in which a higher temperature prevails than in the first, and in a second part of the operating cycle working fluid is positively displaced from the second chamber back into the first chamber, wherein thermal energy is supplied to the working fluid on its passage from the first to the second chamber and removed from the working fluid on its passage from the second to the first chamber, the chambers are formed by variable-volume working chambers of piston machine units (10, 12, 14, 16) coupled with one another and operating out of phase with one another, which communicate with one another by fluid ducts (18, 20, 22, 24) in such a way that the working fluid is positively displaced out of a shrinking work chamber having a relatively high temperature through a first duct, into an expanding work chamber having a lower temperature, a

Abstract: A heat transformation device which is compact and effective for recovering waste heat from one or more sources which sources may have different temperatures, comprises a closed cylinder containing a working piston made of heat conducting material and at least one impact piston which is constructed to act as a recuperator. Electromagnetic means are provided to suddenly move the impact piston when it absorbs heat from an end of the cylinder into contact with the working piston. The cylinder is filled with a low molecular weight, low density gas which has high specific heat and is preferably compressed.