micro CHP products
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the big picture
By Jeremy Harrison

 
 

This section is intended for those who are considering the purchase of a micro CHP system, either for their own home or for clients.  Although technical details are generally available from the links to suppliers' web sites, specifiers and other professionals may wish to consult the PAPERS section to gain a better understanding of the wider issues surrounding micro CHP. 

Products which are available on a commercial basis are clearly identified as such in their descriptions and contain a link to the supplier.  Before considering the purchase of a micro CHP system, however, you should consult the ECONOMICS section, or undertake some other economic viability assessment, to see whether your investment is reasonable.

Information on enabling technologies, which enhance the value of micro CHP, is also included.

EXTERNAL COMBUSTION  ENGINES INTERNAL COMBUSTION ENGINES FUEL CELLS OTHER MICRO CHP TECHNOLOGIES ENABLING TECHNOLOGIES

The first true micro CHP systems were based on external combustion engines as the characteristics of this technology are well suited to this stationary, constant running application.

External combustion engines separate the combustion process (which is the energy input to the engine) from the working gas, which undergoes pressure fluctuations and hence does useful work.

As the combustion process is used to provide a continuous heat input to the working gas, it is more controllable and generally more efficient, cleaner and quieter than internal combustion engines and can be relatively easily adapted to make use of a wide range of fuels.

External combustion engines have the potential for long life and service intervals similar to the annual maintenance of a gas boiler.

Internal combustion engines inject fuel and air into the cylinders where combustion occurs. 

The resulting temperature and pressure changes of the fuel/air mixture (which is also the working gas) act on the piston to produce useful work.

As the combustion process is cyclical, rather than continuous, it is more difficult to ensure complete combustion of the fuel, and noise and pollutant emissions tend to be higher than for external combustion engines.

However, the inherent technical challenges of ICE technology are being gradually overcome and current engines outperform external combustion engines significantly in efficiency terms, although with significant cost and size penalties..

In a fuel cell, the chemical energy within the fuel is converted directly into electricity (with by-products of heat and water) without any mechanical drive or generator.

This can result in high electrical conversion efficiencies and low emissions.  However, numerous additional components are required to condition the fuel and to convert the DC electrical output into AC suitable for domestic installations, adding to the cost and complexity of fuel cell micro CHP.

Commercially available domestic products, based on PEM technology typically achieve electrical efficiencies of around 35% whilst SOFC based products have demonstrated up to 60%.

Total efficiencies tend to be somewhat lower than for engine based technologies.

There are numerous experimental technologies which may at some future date result in useable products. 

These include thermo-electric technologies which utilise temperature difference acting on metals or semi-conductors to produce electricity and thermo-photovoltaic units which convert the radiant energy emitted by the burner to produce electricity from infra-red sensitive PV cells. 

There are also novel engine designs such as the MTT pico-turbine illustrated above.

Although many of these concepts are relatively inefficient and produce little power, there may be applications, for example, in "self-powered boilers" for which such concepts are of value.

 

Micro CHP has implications not only for the immediate installation, but also for the electricity system to which it is connected. 

Gas fired micro CHP technologies may play a key role in supporting the widespread introduction of electrically driven heat pumps and of supporting intermittent renewable generation.

This section covers technologies, products and concepts which are either essential  to enable the operation of micro CHP within the energy system, or which enhance the performance or value of micro CHP products themselves.

These include thermal and electrical energy storage systems  and "smart" load management concepts, intended to optimise self-consumption of generated electricity.

 

For those of you who are not particularly interested in the engine technology and just want to obtain a micro CHP product:
For your home: For very large homes (with swimming pools), small hotels, schools, etc:

WhisperGen (outside EU)

Baxi Ecogen (UK)

Honda Ecowill (Japan, USA)

EHE, European supplier of the WhisperGen unit unfortunately no longer exists

Baxi Dachs (UK, Europe)

EC Power (UK, Europe)

Ecopower (EU, USA)

Page update 14th February 2014

 

the big picture
By Jeremy Harrison

Contact : info@microchap.info

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This site was last updated on 23 February 2014  Jeremy Harrison