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You are here: > Directory > Stirling Engine

Stirling Engine
Generates Energy from Small External Temperature Gradients -- No Longer the Neglected Technology

Tap waste heat or cold. Displacer piston moves enclosed air back and forth between cold and hot reservoirs.

Page Contents:
Featuring Overview Working Demo Units & Kits Comparison How it works Applications Related Sites

Van Arsdell Stirling Engine

Some of the contents on this page have been adapted from

Wikipedia > Stirling Engine
Open Source Encyclopedia; June 15, 2004


  • WhisperGen Gearing Home Use - Whisper Tech has received a $300 million contract to supply tens of thousands of its WhisperGen units to homes in the UK.  Powered by natural gas, it provides electricity and heat at a cost savings and cut in CO2 emissions.
  • Great Primer:
    Stirling engines, invented nearly 200 years ago, are being built by North County man
    - Features Van Ardsell of whose passion is to promote Stirling engine technology via educational kits. (San Diego Union-Tribune; June 1, 2004)
  • Feasibility > Could a 200-year-old engine solve today's petrol crisis? - a leading expert on the Stirling engine has claimed it could reduce petrol and diesel consumption in motor vehicles by more than half. "The problem was that it would cost a pile of money to re-tool up to build Stirling engines." (The Scottsman; June 5, 2004)
  • Solar Application > US DOE homing in on Stirling engines to boost solar efficiency - Stirling solar dish directly converts solar heat into mechanical energy, which turns an ac electrical generator.  (EE Times, NY, Nov. 20, 2004)
  • Open Sourcing > Stirling Engine -- Simplified Plans - Collection of proof of concept designs that you can build for as little as $99.  "This small-scale model situated on one boiling cup of boiling water and cooled by a cube of ice, can turn for 35 minutes."  English translation of French site, by Pure Energy Systems.
  • Book > Around the World by Stirling Engine by Brent H. Van Arsdell
    Probably the best general book on Stirling engines. Explains how Stirling engines work.  Covers all the current power producing uses of Stirling engines along with how to contact the people who build them.  Covers everything from Stirling engines in military submarines, to a Stirling engine that powers the rotisserie for an Oklahoma mechanic's barbecue.
  • Kits > Stirling Engine kits - range in price from $16.70 to $19.95.
Simplified Stirling Engine

The Stirling engine was invented in 1816 by the Rev. Robert Stirling who sought to create a safer alternative to the steam engines of the time, whose boilers often exploded due to the high pressure of the steam and the primitive materials of the time. Stirling engines convert heat (actually, any temperature differential) directly to movement: they use a displacer piston to move enclosed air back and forth between cold and hot reservoirs. At the hot reservoir the air expands and pushes a power piston, producing work and displacing the air to the cold reservoir. There the air contracts and pulls the power piston, closing the cycle.

In more sophisticated Stirling engine a regenerator, typically a mesh of wire, is located between the reservoirs. As the air cycles between the hot and cold sides, its heat is transferred to and from the regenerator. In some designs, the displacer piston is itself the regenerator.

Stirling engines can also work in reverse: when applying motion, a temperature differential appears between the reservoirs. Incidentally, one of their modern uses is in supercooling. However they are difficult to construct and require precise machining, and thus never replaced the steam engine despite being much more fuel efficient than steam engines or even the modern internal combustion and Diesel engines.

Stirling engine types

Stirling Engines come in three distinct types:

  • An alpha Stirling contains two separate power pistons, one "hot" piston and one "cold" piston. The hot piston is situated after the higher temperature heat exchanger and the cold piston is situated after the low temperature heat exchanger. This type of engine has a very high power-to-volume ratio but has technical problems due to the (often) high temperature of the "hot" piston and its seals.
  • A beta Stirling has a single power piston arranged coaxially with a displacer piston. The displacer piston does not extract any power from the expanding gas but only serves to shuttle the working gas from the hot heat exchanger to the cold heat exchanger. This engine does not require moving seals in the hot portion of the engine and can achieve high compression ratios due to pistons being able to overlap in their motions.
  • A gamma Stirling is simply a beta Stirling in which the power piston is not mounted coaxially to its displacer piston. This configuration produces a lower compression ratio but is often mechanically simpler and often used in multi-cylinder Stirling engines.

Working Demo Units & Kits

  • - Features array of kits, includes instructions of how to build a Stirling Engine (from a kit).
    See San Diego Union Tribune feature article June 1, 2004: "Stirling engines, invented nearly 200 years ago, are being built by North County man."
  • / - " Sophisticated demonstration models, using alternative energy technologies for universities, schools and interested individuals like Stirling and Steam engines, fuel cells, photovoltaic objects, toys and more."
    Ready-built unit of dimensions 3.5 x 5 inches.  "This little charmer will run on any warm surface (the warmer the faster), even the palm of your hand and, amazingly, backwards (anticlockwise) on a shallow tray of ice cubes."
    See: Explanation and Analysis of Commercially Available Stirling Engine Demo Unit by
  • Simple Do-It-Yourself Stirling motor, links Only requires a temperature difference on 8C to run. A hot hand and/or an icecube is enough to keep it running.
  • Koichi Hirata: Welcome to Stirling Engine Home Page
  • Adresse til: Stirling Engine Home Page at National Maritime Research Institute
  • Test-Tube Stirling Engine
  • Web archive mirror, Melbourne Society of Model & Experimental Engineers Journal: A Novel Stirling Cycle Hot Air Engine To Build


From: ken rauen
Sent: Tuesday, June 15, 2004 10:51 AM

Stirling engines qualify for "free energy" designation when they allow us to tap previously inaccessible sources of naturally occurring energy. Stirling cycle engines are very efficient for a given temperature difference between the heat source and the heat sink. Actually, steam engines (the Rankine cycle) fall into this category, too; depending upon what kind of hardware and its maintenance you prefer, one or the other will be preferred. Steamers have fewer parts and higher power density. Other fluids, such as a variety of refrigerants, can be used instead of water. Stirlings avoid fluid containment problems, as they can run with air as the working fluid, and will have less maintenance issues.

Solar collectors are a source of low grade thermal energy that has largely gone untapped for electricity. Mount Stirlings of a variety similar to what is show in the aforementioned website, though more robustly designed and constructed, along the back wall of a solar collector, and let the cold side of the Stirling engine bank radiate the waste heat into the shade. 100 W per square foot insulation can translate to almost 10 W/sq ft of electricity with the hot side of the collector reaching only 150F with ambient T at 70F. No high-tech materials are needed. A 25 square foot collector can generate about 200 W of cheap electricity! This competes with solar cells.

Steamers can utilize this size very well with a tube boiler and just one expander connected to one generator. I recommend a "steamer."

Ken Rauen
Science Advisor, Pure Energy Systems

How it works

  • How Stuff Works: Stirling-engine
  • University of Canterbury: An introduction to Stirling-cycle machines (PDF)
  • Stirling-Cycle Research Group
  • About The Stirling Heat Engine
  • (Good information to builders:) Why Aviation Needs the Stirling Engine by Darryl Phillips, main address (, mirror Quote: "...This 4-part series appeared in the March 1993 through March 1994 issues of Stirling Machine World...Common four cylinder engines such as Lycoming and Continental show torque that varies from a negative 100% to a positive 350% of the nominal torque...A Stirling with the same number of cylinders and identical power has a torque variation of +/- 5%!..."
  • Stirling fly motor animation
  • Animations: [1] , [2] , [3]
  • Israel Urieli: Stirling Engine Simple Analysis, main address, Alpha Stirlings, Beta Stirlings, Gamma Stirlings
  • Peter Fette: Stirling Engine Research and Computer (simulation) Programm Development, animation, prozess, mirror
  • Quote: "...One possibility of equalizing the regenerators loss in double acting engines is to design it as a counterflow heatexchanger as described in [1 ..."]
  • Quote: "...This Stirling Engine with 8 cylinders is twice double acting.  Its special highlight is the facility for the heat transfer from a liquid [eg. water] to the working fluid [eg. air] which results in extremely low temperature losses....Because of the nearly isothermalized heat transfer the efficiency is near carnot's ..."
  • Amitabha Mukerjee: Stirling Engine, usage, How does it work? Quote: "...As a final note a solar powered stirling engine coupled with a generator achieved a record solar-to-electric efficiency of 30%!..."


  • Ecoliving: Homegrown micropower has macro prospects
  • Home-scale generators, Micro Combined Heat and Power MCHP
  • Power Producing Engines - American Stirling Company
  • Stirling Technology, Inc.-- The leader in energy recovery ventilator technology
  • Stirling Cryogenics & Refrigeration BV, SPC: Stirling Process Cryogenerator, SGL: The Stirling gas liquefier, StirLIN: Stirling liquid nitrogen production plants, StirLOX: Stirling liquid oxygen production plants, Power Coolers
  • The Stirling and Miller-Cycle Engines Quote: "...The main advantage of the Stirling engine is that it is remarkably efficient. It extracts up to 50 percent of the possible mechanical energy contained in the fuel it uses, compared to a high of about 25 percent for a standard internal combustion engine (ICE)..."

Related Sites


  • PESWiki Directory Listing for "Stirling Engine" - user editable index page of Stirling Engine information and links.
  • PowerPedia > Stirling_engine - Pure Energy System's encyclopedia wiki
  • Google: Stirling Engines
  • DMOZ: Stirling Engines
  • Yahoo!: Stirling Cycle
  • Books: Stirling Engines
  • Web archive: Sun Power vejviser
  • Red Rock Energy Solar Heliostats: This is the start of Will's Stirling engine links
  • Adam's place > projects > stirling engines
  • Robert Sier: Stirling Engine and Hot Air Engine
  • Webring: Home > Hobbies & Crafts > Models, Stirling and Hot Air Engine Ring

Information media

  • Stirling Machine World SMW
  • Stirling News is published quarterly in the UK by The Stirling Engine Society
  • More Stirling News papers, Search for "Stirling News" on this page
  • 10th Stirling Engine Conference 2001 ISEC


Index created by Sterling D. Allan, June 14, 2004
Last updated December 03, 2004



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