Method and apparatus for converting thermal energy into work

A method for the conversion of thermal energy into mechanical energy in an apparatus comprising a first part in which a liquid working medium is heated using a heat source in the form of a liquid medium causing it to expand and a second part in which the working medium is cooled causing it to contract, wherein the first and the second part are effectively connected forming a closed circulation system containing the working medium, whereby as a result of heating, the working medium contained in the closed circulation system expands in the first part without phase change from liquid to gas, the working medium produces mechanical energy, the heated working medium is subjected to a heat exchange process for the recovery of thermal energy, which thermal energy is further utilized to do work, the liquid is in at least the second part in a counter-current heat-exchanging relationship and the transferred heat is used for the production of mechanical energy, characterized in that the liquid heat source medium is in a counter-current heat exchanging relationship with the liquid working medium in the first part to transfer substantially the entire heat content from the liquid heat source medium to the working medium in the first part.