Index   ii

1       Introduction  1

2       Stirling Engine  1

3       mCHP technologies  1

4       Dish-Stirling technology  2

5       Market for mCHP   2

6       GHG Emissions  3

6.1      mCHP   3

6.2      Dish-Stirling  3

7       Cost of the electricity  3

7.1      mCHP   3

7.2      Dish-Stirling  5

8       Barriers  5

8.1      mCHP   5

8.2      Dish-Stirling  6




1                   Introduction

Stirling Engine (SE) technology presents an increase in the interest as microgeneration combined heat and power (CHP) technology as well as in high scale electricity generation.


In Alberta, with the support which represents Microgeration policy, the expectation in the use of micro CHP (mCHP) has increased and retail market participants begin to offer this technology in housing and farming sectors. WhisperTech company leads the offer of this technology in Alberta with its product WhisperGen(TM) offered by ENMAX for mCHP


Instead of this rising interest, the market share of this technology does not increase in the same order around the world and in Alberta, where we don’t still have application using this technology.


In high scale electricity generation, pilot Power Plants have been built in India and USA with promising outcomes.


2          Stirling Engine

Stirling Engine[1] (SE) is a closed-cycle regenerative heat engine with a gaseous working fluid. This categorizes it as an external heat engine which means it can be driven by any convenient source of heat."Regenerative refers to the use of an internal heat exchanger called a regenerator which increases the engine's thermal efficiency compared to the similar but simpler hot air engine. The principal characteristics of SE are:

·         It can run without combustion as source of heating (solar, geothermal);

·         In case of combustion, this is an external combustion;

·         Higher efficiency (up to 50% against 30% of Rankine cycle);

·         Simpler than others engines (less valves, lubricants);

·         It could be used as heater in winters and cooler in summers;

·         Less noisy; and

·         More efficient in cold weather.


And the limitations are:

·         Heat exchange requirements;

·         Isolation between both sides of the engine; and

·         Special materials requirement due to high temperature.


Until now, the industry offers two different uses of Stirling Engine technology:

·         As mCHP, using a fossil fuel providing the energy to produce electricity plus heating.

·         As large generation; a collector concentrates the sun radiation in a small surface which gives to the Stirling Engine the energy to produce electricity (Dish-Stirling).


3          mCHP technologies

The units offered by the different builders have a range up to 10 kW, being the most common unit of around 1 kW.

The common fuel used for mCHP unit for housing and farming is Natural Gas, but some units are offered based on liquid fuels (gasoline, diesel) and biomass.


With different state in the development of their technology, different companies are offering products for electricity generation base on Stirling Engine technology. Most of them are developing the technology and offer it in European and Japanese markets; some of them are:

·         Whisper Tech Ldt., based on New Zealand and offering WhisperGen mCHP unit.

·         Microgen Energy Ltd., based on UK and Belgium. Microgen was one of the leading European developers of a mCHP system with this technology.

·         Lion, a Denmark company offering Lion Powerblock mCHP;

·         Infinia Corp., a USA corporation offering its Infinia solar mCHP;

·         Sunpower Inc., a USA corporation offering its SunPower mCHP unit;

·         Stirling Energy Systems Inc., a USA corporation offering its solar mCHP unit;

·         Disenco Energy PLC, an England company offering its Disenco mCHP unit;

·         Cogeneration & On-Site Power, an England company offering Ecowill mCHP unit;

·         EcoPower, a Denmark company offering its EcoPower mCHP unit;

·         SenerTec GmbH, a German company offering its Dachs mCHP unit.

·         Stirling System GmbH, a Swiss corporation offering its SOLO Stirling mCHP unit.

·         Sunmachine, offering Sunmachine mCHP unit based on biomass.

·         Microgen Energy Ltd, subsidiary of the BG Group has developed a 1 kW mCHP for the European market.

·         ENATEC, a joint venture between Dutch utility ENECO and Research Centre of the Netherlands is developing a 1 kW mCHP unit.

·         Honda is planning to introduce in 2008 a mCHP based on Stirling Engine in Europe.


4          Dish-Stirling technology

The energy to impulse the Stirling Engine equipment comes from the Sun. A collector concentrates the Sun radiation in the base of the engine providing the enough energy to produce electricity.


The efficiency of this system is around 33%, significantly higher than the solar panel efficiency which range is between 10 and 17%.


5          Market for mCHP

Microgen Energy and Whisper Tech are the companies which more quickly developed the technology in Europe, offering:

·         On grid product for housing; and

·         Off grid products for marine, homes, remote and on-road uses.


Starting early in 2000, the European market for SE technology moved on housing generation, for mCHP. The main industries have installed in Europe more than 10,000 units (overcoming the stages of pilot tests and market test) and a sequence of market development agreements has significantly jumped the installed unit during 2008.


The landing in the North American market is imminent and some companies started the process to offer their technology in The States.


In Alberta, ENMAX will offer Whisper Tech (WhisperGen(TM)) technology. Whisper Tech expects beginning to offer its technology for mCHP during early 2009 in Canada after to complete the last two developments:

·         Development of 60 Hz, 110 V unit; and

·         Fulfill Natural Resources Canada homologation.


Whisper Tech will offers its technology in Canada based on Natural Gas fuel.


6          GHG Emissions

6.1         mCHP

The mCHP builders do not still provide information about GHG emission, but a study[2] of the different providers says that the GHG emission for a mCHP based on Stirling Engine and using Natural Gas as fuel is close to Cogeneration Gas Plant Unit:

·         The small units (around 1 kW) produce a GHG emission between 400 to 580 Kg GHG/MWh;

·         The medium units (around 3 kW) produce a GHG emission between 300 to 470 KgGHG/MWh; and

·         The high units (around 9 kW) produce a GHG emission between 240 to 370 Kg GHG/MWh.


These emission levels mean:

6.2         Dish-Stirling

The technology is based on solar energy as fuel. Its emission is extremely low and it is calculated between 20 and 80 Kg GHG/MWh.


7          Cost of the electricity

7.1         mCHP

There is not still cost for North American market, but estimation could be reached based on European[3] cost. AB profits several benefits face on this technology:

·         Deregulated electricity market;

·         Microgeneration regulation;

·         Non joining Natural Gas and Electricity seasonal prices;

·         High availability of Natural Gas; and

·         Low Natural Gas price.


The following figures show (first level analysis, based on annual based average values) the COE for a 1 kW of capacity Stirling Engine technology. The figures represent in AB:

·         COE for electricity generation only;

·         COE as mCHP optimised for microgeneration.




The following figure shows the analysis of sensibility for the more significant variables in the business case in AB.



7.2         Dish-Stirling

Several companies are working in the development of Stirling Engine technology as renewable technology for Power generation. All cases are based on solar radiation as source of energy to impulse the engine (Dish-Stirling). Pilot projects are being developed in India and two big scale projects are being developed by Stirling Engine Systems (SES) in California:

The Capital Cost for these projects is around 10,000 U$S/kW installed. They are one of the first big projects using this technology and SES expects to reduce significantly this cost in next years. Due to low maintenance and very low operative cost, when Capital Cost drops up to 3,000 U$S/kW, the technology will be market competitive in USA. SES alleges that Capital Cost could be reduced up to 1,000 U$S/kW.


The use of Dish-Stirling technology for housing is not market competitive.


8          Barriers

8.1         mCHP

The main barriers for this technology are:


8.2         Dish-Stirling

The main barriers for this technology are:



In AB, mCHP based on Stirling Engine will present an interesting technology due to:


Dish-Stirling presents as mayor constraint the Capital Cost, but it is a technology in the beginning of it development. It presents several advantages:


In AB, during next years, we could attend the market development of Stirling Engine technology as mCHP. 


Dish Stirling technology will take more time to be developed and to reach levels of applicability in AB Wholesale market.



[1] The Stirling engine technology was invented by Reverend Dr. Robert Stirling and patented by him in 1816.

[2] Pehnt, M., (2008) “Environmental Impacts of Distributed Energy Systems – The Case of Micro Generation” Environmental Science & Policy Journal, Issue II, pp. 25-37

[3] Kuhn, V. et al. (2008) “MicroCHP: Oveview of Select Technologies, Products and Field Test Results” Applied Thermal Engineering Journal, Issue 28, pp. 2039-2048.