CHP is a well known green technology, saving energy by using low grade waste heat to heat water. Applications requiring a lot of hot or warm water are particularly suitable, eg some factories or swimming pools, because the natural output from an engine consists of a small amount of useful work and a large amount of waste heat.
Recovering energy from exhaust gases, or converting work into electricity more efficiently, improves the ratio of work to heat. Small CHP units, particularly in domestic systems, are now reaching the market and have the potential to greatly reduce central heating bills and overall carbon emissions, but these need to have a high work:heat ratio at a low cost. Larger CHP systems have significant potential as well, particularly in colder countries where the demand for hot water is high.
Permanent magnet brushless generators are a popular technology for this kind of application, particularly at low powers or high speeds, and asynchronous induction generators are suitable for the larger applications. For instance, a high speed (100 krpm+) PM alternator, coupled to an automotive turbo-charger, could be used to extract 1 or 2 kW from a typical engine exhaust.
EMX has experience in CHP, and holds a patent which could be applied to such systems. We are looking to continue developing this kind of technology.