There are two principal types of Stirling Engine, kinematic and free-piston.  All Stirling engines have two pistons (functionally speaking), one of which shuttles the working gas between the hot and cold zones and is known as a displacer, whilst the other is subject to the resulting pressure changes and does work to drive the engine.  In the kinematic engine, these two pistons are physically connected by a crank mechanism, whereas in the free-piston engine, there is no physical linkage and the displacer oscillates resonantly.  In theory the LFPSE (Linear Free Piston Stirling Engine) is much simpler as it contains fewer moving parts.  In practice, the challenges of differential expansion and linear generator design have so far proved a major obstacle to commercialisation.

For further discussion of the relative merits of these engine types see section on papers.

WhisperGen MEC (Microgen) Infinia (STC) Disenco

The WhisperGen micro CHP unit  is marketed by the UK energy company, E.ON (formerly Powergen).

It is a four cylinder unit which leads to smooth, vibration free operation, with noise levels similar to a domestic freezer.  The MkV unit, incorporating a supplementary burner, was introduced in 2005 to provide additional flexibility, making the unit suitable for larger homes.  This variant also incorporated an integral acoustic enclosure which made kitchen installation possible.

Both these models, hand built in New Zealand, are being superseded by mass produced European units.

The Microgen unit, developed by BG Group from a US (Sunpower) design, is a LFPSE which is intended for wall-mounting; it contains a supplementary burner which enables it to meet the full heating requirements for even larger homes. 

Following disposal by BG Group in 2007, development of the Microgen unit was taken over by MEC, a consortium of gas boiler companies (Viessmann, Baxi, Vaillant, Remeha) and Sunpower.   Each of the boiler companies is expected to market their own variant of micro CHP unit incorporating the MEC engine, currently being produced in Japan.

The Infinia (formerly known as STC) LFPSE is now being used by MTS, Bosch and Enatec in Europe as well as Rinnai in Japan. 

 

Rinnai will produce the LFPSE module for integration into micro CHP packages by the other partners for the European market, with a trial of 1000 units planned for 2008-2010.  Rinnai will also produce a packaged unit for the Japanese market.

The Disenco unit is a kinematic design with an electrical output of around 3kWe, significantly higher than the other products.  It is based on a design originating in Lund University and has recently been substantially redesigned by Ricardo in the USA.

The high electrical output enhances payback of the unit (which is anticipated to be significantly higher then the other three products).  This does, however, make the unit susceptible to the recoverable value of exported power from the unit unless it can achieve high utilisation such as in a small hotel.

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For UK sales contact:

whispergen@powergen.co.uk

For further information see:

Rinnai

Enatec

Bosch

MTS

Electrical output

1kWe

Electrical output

1kWe

Electrical output

1kWe

Electrical output

3kWe

Thermal output

7kWt (engine) plus 5kWt (burner)

Thermal output

4-40kWt

Thermal output

4-40kWt

Thermal output

9kWt

Application

Individual family homes

Application

Individual family homes

Application

Individual family homes

Application

Homes & small commercial

Supply only cost

1350 plus VAT

Supply only cost

Supply only cost

Supply only cost

Installed cost

3000 including VAT

Installed cost

Installed cost

Installed cost

Availability:

East Anglia, East Midlands, NW England - 2004

Initial production runs sold out very quickly, and all production until 2007 is already committed.  Mass produced units expected to become available again in 2008.

Availability:

2008 trial

Availability:

2008-2010 trial

Availability:

2009?

 
Contact : info@microchap.info
Disclaimer:  Information is provided for general information only and no endorsement or recommendation of any company or product should be inferred.  This is not a commercial site and none of the companies mentioned are sponsors of the site.  Please note that the views expressed on this site are  entirely my own and do not represent the official position of my current or previous employers.  This page was last updated on 15th December 2007  Jeremy Harrison

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