NOVELTY - Thermally activated system (I) for increasing the pressure of a gaseous working fluid (306), comprises a working fluid having a bubble point of less than 20 degrees C when the working fluid is at 1 atm pressure, and a solvent comprising an organic oxygenate containing at least one oxygen atom and at least one atom comprising nitrogen, phosphorus and/or fluorine, in its molecule, and the dew point of the solvent is greater than 130 degrees C when the solvent is at 1 atm.    USE - The thermally activated system is useful: for increasing the pressure of a gaseous working fluid used in power generation process (claimed); for heating or cooling an enclosed space or process stream, comprising interior of a building or vehicle or a process stream in an industrial process; and for both winter heating and summer cooling e.g. by switching the roles of the condenser and the evaporator as season changes.    ADVANTAGE - The thermally activated system: is lower cost, highly efficient thermally activated heat pump and air conditioning system that works at a higher pressure than the conventional lithium bromide chillers; is capable of working at below sub water freezing temperatures; can be thermally activated, especially with low level of heat, from commercial solar water heaters and the cooling water from vehicle engines; does not use corrosive materials and has no potential issue of absorbing freeze out during operation; and provides non-ozone depleting working fluid and solvent, which improves the performance of a heat activated pressure booster.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) thermally activated system (II) for increasing the pressure of a gaseous working fluid;    (2) a power generation system, comprising the thermally activated system (I) and an expander, where at least a portion of the higher pressure, substantially vaporized stream of the working fluid from a generator (34) is expanded in the expander to generate mechanical energy, and at least a portion of the exhaust stream of the working fluid from the expander is absorbed into the lower pressure, liquid stream of an absorbent (314) in an absorber (31);    (3) a thermally activated process (III) for increasing the pressure of a gaseous working fluid, comprising using the working fluid and the solvent;    (4) thermally activated process (IV) for increasing the pressure of a gaseous working fluid; and    (5) a power generation process, comprising the thermally activated process (III), expanding at least a portion of the higher pressure, substantially vaporized stream of the working fluid in an expander to generate mechanical energy and absorbing at least a portion of the exhaust stream of the working fluid from the expander into the lower pressure, liquid stream of the absorbent in the absorber.    DESCRIPTION OF DRAWING(S) - The figure shows a single effect absorption heat pump process.    Evaporator (13)    Absorber (31)    Generator (34)    Working fluid (306)    Absorbent (314)