Stirling Engine
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the big picture
By Jeremy Harrison

 

Stirling Engine | Rankine Engine

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 (Inspirit)

The WhisperGen micro CHP unit  is marketed in the UK by 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 Mk5 unit, incorporating a supplementary burner, was introduced in 2005 to provide additional flexibility, making the unit suitable for larger homes. 

In January 2008, WhisperGen announced the establishment of a joint venture (EHE) with Spanish white goods manufacturer Mondragon CC to mass produce units for the European market.

Since that time several hundred units have been undergoing field trials in Europe.

E.ON announced product launch in 2012.

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, now being manufactured in China.

The UK variant manufactured by Baxi, is available from British Gas.

The Infinia (formerly known as STC) LFPSE is now being used by Ariston (formerly MTS) and Bosch 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.

Although based on a virtually identical core LFPSE as the MEC derivatives, this unit is more realistically housed within an integrated floor-mounted unit incorporating a hot water cylinder.

The Disenco unit is a kinematic design with an electrical output of around 3kWe, significantly higher than the other products.  The high electrical output enhances payback of the unit (which is anticipated to be significantly higher then the other three products), although this makes 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.  In January 2008, Disenco announced a manufacturing partnership with Autocraft to produce the core engine, with packaging by Malvern boilers and recently announced marketing deals with Endesa and Centrica.

In early 2010 Disenco was placed in receivership; the design has been taken over by Inspirit Energy who expect to trial the unit in 2011.

For UK sales contact:

E.ON Energy

 

For Germany sales see:

Sanevo

Baukontakt

For UK sales contact:

British Gas

 

For further information see:

Baxi

Remeha

Vaillant

Viessmann

For further information see:

Rinnai

Enatec

Bosch

Ariston

Infinia

For further information:

Inspirit

Electrical output

1kWe

Electrical output

1kWe

Electrical output

1kWe

Electrical output

0.5-3kWe

Thermal output

7kWt (engine) plus 7kWt (burner)

Thermal output

3-24kWt

Thermal output

4-40kWt

Thermal output

12-17.4kWt

Application

Individual family homes

Application

Individual family homes

Application

Individual family homes

Application

Homes & small commercial

Supply only cost (UK)

£contact supplier

Supply only cost (Germany)

€10,000

Supply only cost

NL  2010  €10,000* (less €4000 subsidy)

Supply only cost

UK  2010  £6-8000 (depending on FIT)*

Supply only cost

Installed cost (UK)

2004  £3000 including VAT (initial units subsidised by E.ON)

2010  £6-8000 (depending on FIT)*

Installed cost (Germany)

2010  €14,000

Installed cost

UK  2010  £6-8000

 

Installed cost

Installed cost

Availability:

Initial production runs sold out very quickly.  Mass produced units available in limited numbers 2010 in Germany & Netherlands.

E.ON announced 2012 launch in December 2011

Availability:

2010 limited availability (Baxi via BG)

2010 limited availability from Remeha (NL)

Availability:

2008-2011 trial

2012 limited availability

Availability:

 

Page updated January 2012      
 

the big picture
By Jeremy Harrison

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This site was last updated on 9th January 2012  © Jeremy Harrison