A thermal energy conversion plant, wherein a pressurized liquefied working fluid gasifies in an evaporator unit located at the lower level of a closed-loop thermodynamic circuit, ascends through a widening ascending conduit to a condenser unit located at the upper level of said thermodynamic circuit, condenses and falls because gravity powering a power extraction apparatus, before entering back into the evaporator, and restarting the cycle. A much lighter pressuring gas could be optionally included in the widening ascending conduit.