Here is A Good Approach to the Energy Problem
Here is more from Kokhala:
Kokhala's solution uses a unique heat-to-electricity closed loop power cycle solution optimized to generate electricity from external heat sources above 120F. The heart of the EnergyCell® are two proprietary, oil-free variable speed positive displacement expander engines, optimized to efficiently convert the external heat into mechanical rotary power, and then into electricity. The modular components are designed to function in a compound thermal relationship such that a high temperature power cycle is optimized with working fluid circulates between 600F and 250F and a low temperature power cycle is optimized with a different working fluid circulates between 250F and 120F. Since the heat transfer and expansion occurs in a biphase mode, cycle efficiency are optimized and the heat exchangers are minimized. Each expander turns an efficient permanent magnet DC generator with a high turned down ratio. The residual heat from the low power temperature cycle is provide to heat domestic hot water and provide comfort heating for the facility. Based on principles of organic Rankine thermodynamics, the EnergyCell®. exhibit excellent efficiency, low acoustical and electrical noise, no polluting emissions, high reliability and long life.Source.
Hat tip Peswiki.