Heat and


from wood pellets




Microgen Engine Corporation has been working for many years on the development of a free-piston Stirling engine that is suitable for mass production. Since 1995, the enterprise has invested 200 million euros into the development of this concept; efforts that have been paid off with both technological and commercial success. As a result, the Microgen Engine Corporation has been the world's only successful mass producer of Stirling engines since 2010, when tey first became a commercial viability.  


World-renowned companies, such as Vaillant and Viessmann also rely on the Microgen Stirling engine.


The Microgen Stirling engine produces alternating current (50 Hz) and provides 1 kW of electrical power; ideal for use in domestic homes.




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Functional principle

  • The displacement piston pushes helium through the regenerator from the head to the cooler. 
    The spring on the opposite casing at the bottom pushes the piston back upwards.
  • The helium is alternately heated and cooled, and as a result it expands and contracts again. 
    This causes the creation of a pressure wave, which repeats as the cycle begins again. 
  • The working piston is moved up and down by these pressure waves up and down.   
  • The magnetic working piston is surrounded by a fixed magnetic coil with copper windings, which means that an alternating current is generated.


This cycle is repeated 50 times per second, generating AC power at 50Hz.




More information about the

Microgen Stirling engine




Die Verwirklichung der Vision einer Strom produzierenden Heizung ist unsere Mission.

Das Besondere daran? ÖkoFEN entwickelt eine CO2-neutrale Technologie mit Holzpellets als Energieträger, welche ein Gebäude sowohl mit Wärme als auch mit Strom versorgt.


Die wohl bekannteste und auch gängigste Form der kombinierten Wärme- und Stromgewinnung ist die Kraft-Wärme-Kopplung (KWK) oder auch Wärmekraftkopplung (WKK). Dieses System steht auch für das Projekt ÖkoFEN_e im Fokus.


Das Prinzip einer Strom produzierenden Heizung

Das Prinzip einer Strom produzierenden Heizung

Das System Kraftwerk & Heizkessel (in der Grafik links) braucht mehr Energie um die gleiche Leistung wie die stromerzeugende Heizung zu erzeugen. Der große Energiefresser ist dabei das Kraftwerk. Die bei der Stromgewinnung anfallende Wärme wird über Kühlsysteme vernichtet.


Der Heizkessel (in unserem Beispiel ein Öl-Kessel) erreicht einen besseren Wirkungsgrad. Hier gehen nur 10% der eingesetzten Energie verloren. Das Gesamtsystem weist jedoch einen Verlust von fast 34% auf.


Strom aus Wärme gewinnen

Die stromproduzierende Heizung (in der Grafik rechts) nutzt hingegen die gesamte Wärme des Systems und erreicht dadurch einen sehr geringen Verlust von nur etwa 10%. Diese Einsparung an Verlusten wird durch die Erzeugung von Strom und Wärme direkt am Ort des Verbrauchers ermöglicht. Im Fall von ÖkoFEN_e würde der Strom aus Pellets gewonnen werden. Diese stromerzeugende Pelletsheizung mit Stirlingmotor wird unter dem Namen Pellematic Smart_e vermarktet.


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Green energy in the right place at the right time 

With this method, power is generated as it is required, so that generation matches exactly with the actual consumption. During the winter, when we are at home we need both heating and a large amount of electricity. Compared to photovoltaics, a higher proportion of power needs can be generated at home, meaning that the demand of electricity from the public network is low. 

No need for costly network expansion 

The expansion of the power supply system that is now essential due to the increased use of renewable energy technologies in centralised power plants becomes unnecessary with decentralised energy generation using CHP methods. This is because the electricity is only produced where it is required and used.



Generating electricity with a CHP system allows households and communities to produce their own power. Excess power produced can then be fed or even sold back into the public power supply system. 



In traditional dedicated electricity power plants, the heat that is produced is disposed of in cooling towers. However, in CHP systems, this so-called "waste" heat is used and not wasted, leading to significantly higher efficiences.



Compared to the separate generation of electricity and heat, cogeneration reduces the energy consumption required to produce these two essential requirements of modern society by more than a third. 


By using responsibly sourced and local biomass as an energy source the total energy production is 100% ecological and sustainable. In this way, importing electricity generated by nuclear power and the burning of fossil fuels (e.g. heating oil) will become unnecessary.

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The principle of a heating system that also generates electricity has been in existence for many years, especially in relation to large-scale power generation, and is an issue that has become more and more important due to the current energy and climate change debates. The technical implementation of this principle of simultaneous heat and electricity generation is known as combined heat and power, or "cogeneration".  



Combined heat and power (CHP)

In a combined heat and power (CHP) system, the energy produced from the heating plant, in our case the boiler, is used simultaneously for power generation and the generation of heat.

Large CHPs with a capacity of up to several hundred megawatts have been reality for a considerable time, and already supply us with electricity and heat. The new development is that against the backdrop of the energy debate in recent years, more and more so-called mini- and micro-CHPs are emerging into the marketplace. 



Micro combined heat and power (mCHP)

mCHPs are combined heat and power plants with an electricity capacity of less than 50 kW, which covers the lowest power sector of the market. To give an idea of scale, a normal single-family household has a peak demand of 4 kW of electricity, and a supply of 1 kW covers 88 percent of the electrical power consumption of an average household.


Figure based on: bine.info

More about the topic

Artikel: Die andere Brückentechnologie (Autor: M. Massarrat in Blätter für dt. und internat. Politik 6/2011) (in German)
Wikipedia article: Cogeneration

Bine Informationsdienst - Energieforschung für die Praxis (basisEnergie Nr. 21) (only available in German)

Deutscher Bundesverband Kraft-Wärme-Kopplung (only available in German)

Die Kraft-Wärme-Kopplung auf 3sat (youtube Video) (only available in German)

Electricity from biomass on www.bios-bioenergy.at

Technologie Portrait: Kraft-Wärme-Kopplung (bmvit 2010) (only available in German)

www.bhkw-forum.info (in German)

www.bhkw-infozentrum.de (in German)

www.waermekraftkopplung.ch (in German)


Austrian Energy Agency (Projektseite mKWK) (in German)

Förderinformation des Landes NÖ für mKWK (in German)

Wikipedia article: micro combined heat and power

www.stromerzeugende-heizung.de (only available in German)

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