A thermodynamic system and method for performing work includes a working fluid and a fluid pump for pumping the working fluid through a cycle. A thermal input supplies heat to the working fluid. An expansion device downstream of the thermal input converts at least the heat of the working fluid to useful work. A heat exchanger downstream of the expansion device has a first portion to transfer heat from downstream said expansion device to a second portion at or upstream of said thermal input. A conversion device expands the working fluid with constant enthalpy from a higher to a lower pressure.

An Ocean Thermal Energy Conversion (OTEC) system having a turbine with an upstream side and a downstream side. Warm water under a partial vacuum is converted into a vapor, the vapor being supplied to the upstream side of the turbine at a pressure controlled by the temperature of the warm water. A condenser is situated on the downstream side of the turbine to cause the vapor, after passing through the turbine, to undergo a phase change back to a liquid, which can be used as potable water. The condenser is coupled to a source of a cooling liquid, and the pressure of the vapor on the downstream side of the turbine is determined by the temperature of the cooling liquid. A flexible floating solar collector supplies the warm liquid to the upstream side at a temperature higher than normal ambient temperature.

Systems and methods for collecting, storing, and conveying aqueous thermal energy are disclosed. In a particular embodiment, a floating film retains solar energy in a volume of water located under the film. A series of curtains hanging from a bottom surface of the film define a passage between a periphery of the film and a center of the film to direct the heated water at the center of the film. The heated water is circulated to deliver the heat to a dissociation reactor and/or donor substance. The donor is conveyed to the reactor and dissociated.