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.
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).
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.
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%.
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.
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:
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.
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.
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.
The main barriers
for this technology are:
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.