Using refrigerant as the working fluid, large scale geothermal waste heat generators are now a reality.

We're taking the idea to the next level - by using the waste heat from the microturbine, we can generator additional power and still have heat left over for space heating.

If you already have a CHP unit, you can add on this concept to run an electrical generator off of the hot water.

http://www.discturbine.com

The technology developed using a ORC (Organic Rankine Cycle) can operate off any heat source, with a minimum of 125 deg F temperature differential between the heat source and sink.  Geothermal energy is only one potential application.  Similar systems are already in operation off heat generated from landfill flares and gas turbine exhaust.  Other applications may include using biomass as a fuel.

The oil and gas also provides another possible application for the ORC power plant.  Because most oil and gas wells are quite deep, they are warmed by the natural thermal gradient of the earth.  In 2004 the U.S. produced over 2 billion bbl of “waste” water along with the oil and gas production, primarily from the Gulf States with temperatures high enough to produce electricity.  This hot water could be used to generate power directly, without impacting oil and gas production.