engine that will burn their favorite fuel. I recently had the
opportunity to read, "Principles and Applications of Stirling Engines"
by Colin West and on page 206 it tells about a 4.5 kW rice husk
burning Stirling engine that was financed by the US Agency for
International Development and built by Sunpower of Athens Ohio.
The book is available from Stirling Machine World.
I'm taking the liberty to be re-post a 1998 letter by L. Merrick
Lockwood that I found here:
The e-mail address that I have for Mr. Lockwood bounces. If anyone
knows how I can get in touch with him please contact me at the phone
number on our contact us page.
From: Merrick Lockwood
House 43, Road 23, Banani
Dear Tom and Ronal,
I have been tuned in on the stoves list for quite some time and I
guess I should be contributing my two cents worth. Tom's
upcoming trip has prodded me to do this now in the hope that this
reaches him before he leaves for India and the Philippines.
I have been involved with Stirling engines since 1979 when I
proposed a project to The Asia Foundation in Bangladesh to
develop a small (5hp) rice husk fueled Stirling engine for use in
rural rice mills. Ultimately this project was funded by the
United States Agency for International Development (USAID) and
ran from 1981 to 1986 as the Rice Husk Energy Project (RHEP). The
design of the Stirling engine was sub-contracted by the Asia
Foundation to Sunpower, Inc. in Athens, Ohio. The engine was
completed in the first year of the project and by 1982 a
prototype rice husk fueled Stirling engine had been designed,
built and demonstrated at Sunpower's facility in Ohio. The
engine had a bore of 300 mm, displacement of 7 liters and was
designed to operate at 5 bar air pressure at 600 rpm.
During the next 4 years here in Bangladesh we went through three
iterations of design modification and fabrication in a facility
we had set up near Dhaka. In this process many snags in the
prototype design were worked out but we continued to have
problems with lack of durability in the Ericsson linkage which
incorporated a bell crank system to drive the displacer. This
mechanism (excluding the crankshaft) had 8 moving parts and 12
bearings. For our last engine which was designed and made in a
crash program during the last 3 months of the project, we re-
designed the engine, switching to a massively built but simple
Ross linkage with only 4 moving parts and 5 bearings. This
engine ran quietly and promised good durability but.... falling
world oil prices and vanishing interest in alternative energy
within the US Govt. scheme of things, scratched funding for
HOWEVER, the original RHEP Stirling engine design with Ericsson
linkage survived. By 1984 two of Sunpower's people had set up
their own company (Stirling Technology, Inc.) and went into
business with an an Indian company in Madras (Stirling Dynamics)
to manufacture a improved version of the original RHEP prototype.
By incorporating the engine's compressor with the displacer rod
to double as a bounce chamber they hoped to relieve the stresses
that had been fatal for the bellcrank displacer drive mechanism
in the prototype. Their engine, the ST-5, was manufactured for a
period in Madras and generated a lot of interest in India and
abroad. I think about one or two hundred were manufactured. Of
these around 40 were procured by the Indian Government's
Department (now Ministry) of Non-conventional Energy Sources and
put in different locations in India for field testing. The
compressor "fix" worked initially, but when the compressor itself
wore out the linkage again took the load and eventually the
likleyhood of mechanical failure increased. This and other
problems, including increasing costs, eventually put the engine
into mothballs, though some are still being nursed along by a few
Since 1986 I have continued working, part time or full time, on
Biomass fueled Stirling engines. As a matter of convenience I
have aimed at running them on charcoal, thus my interest in the
stoves list. My target engine sizes keep getting smaller, first
to 500-1,000 watts, now the latest is aimed at 100-200 watts for
electricity at the rural household level, perhaps in conjunction
with a cookstove. More on this another time.
The question for Tom is, are you going to be visiting Bangalore?
I suspect you might as Dr. H.S. Mukunda with his combustion and
gasification team at the Indian Institue of Science have done a
lot of work on gasifiers for conversion of biomass to mechanical
power in association with ASTRA. Though maybe you are focusing
on some of the commercial groups who are manufacturing and
selling gasifiers in other parts of India. In a week or so I'm
headed to south India for a few weeks and will be visiting
Bangalore which is not far from where I stay when there. If you
are going to be in that area it would be interesting to meet,
time permitting. Any possibility?
With best regards,