Isothermal open cycle thermodynamic engine and method

Abstract

A pollution-free thermodynamic engine system and method for converting thermal potential energy to useful mechanical energy employing an isothermal or quasi-isothermal primary working fluid thermodynamic expansion cycle. A relatively cold primary working fluid is conducted from a low temperature storage tank, through a plurality of engine stages each comprising a heat exchanger and an expansion engine operated on an isothermal of quasi-isothermal expansion cycle, and finally exhausted. A relatively warm secondary fluid is circulated through the engine stages to provide a heat input thereto. The engine stages are connected to the primary working fluid path in parallel to operate on a first isothermal expansion cycle; the engine stages are cascaded to operate on a second serial isothermal expansion cycle. A plurality of preliminary heat exchangers in the primary fluid loop enable operation of the engine system on an alternate quasi-isothermal cycle in which the primary working fluid is cycled a plurality of times in a closed loop to improve the energy conversion efficiency of the system.