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Masonry cookstove




The following correspondence was received from Jorg Ostrowski, an architect
in Alberta who specializes in sustainable construction. I thought that it
might be of interest to the list. "Cookstoves", in this context, refers to
the typical North American or European kitchen range, with a cast iron or
steel cooking surface. "Heat transfer efficiency" refers to heat transfer to
the house, not necessarily the cooking pot.

Best........Norbert Senf
--------------------------------------------------------
>
>Date: Fri, 29 Nov 1996 10:26:04 -0400
>>To: Jorg Ostrowski <ash@freenet.calgary.ab.ca>
>>From: Norbert Senf <mheat@mha-net.org>
>>Subject: Re: masonry cookstove
>>
>>At 07:38 PM 28/11/96 -0700, you wrote:
>>>
>>>Norbert: Have you build the above with a water jacket? Even without that,
>>>what combustion and thermal efficiency could be expected? Thank you for
>>>your response. Have a warm day. Jorg Ostrowski
>>>
>>
>>Hello Jorg:
>>
>>Adding a water jacket to a cookstove is fairly simple. We had one hooked
up to our own cookstove (until we changed tank locations), and it easily
generated 60 gal of boiling water/day due to the fact that our cookstove is
on all day.
>>
>>We've never done efficiency testing on cookstoves, and I don't know of
anybody who has. I would expect overall efficiency to be in the 65% range -
you might be able to stretch this to 70-75% with an optimized system. I
wouldn't expect much effect from a water jacket, although I would steer away
from airtight cookstoves.
>>
>>A fellow near Kingston (Ontario) buys up old Findlay Oval cookstoves and
rebuilds them - he has a whole barn full of them, and you can get one with
new nickel in the 1500 - 2000 range.
>>
>>Building a masonry cookstove is expensive due to the cost of the imported
European hardware.
>>
>>We're building a custom system north of Toronto next week in a house
designed by Greg Allen that includes a Wamsler woodburning cookstove that we
imported from Germany - it is a compact one (24 x 24" cooktop) designed as
an insert into a masonry surround and cost a little over $2000 by the time
it got here. We used one a few years ago and the client is extremely happy
with it. The company also makes several other, larger models including
models with water jackets. You can get their catalogue from:
>>
>>Hannes Langeder, dir. Export
>>Wamsler Haus und Kuechentecknik (Munich)
>>Fax (49)89/5896-238
>>
>>Finnish hardware for masonry cookstoves can be obtained from:
>>
>>Maine Wood Heat Co.
>>RFD 1, Box 640
>>Norridgewock
>>ME  04957
>>207-696-5442
>>FAX 207 696-5856
>>
>>Best............Norbert
>>
>------------------------------------------------
>At 07:51 AM 29/11/96 -0700, Jorg Ostrowski wrote:
>>
>>Thank you for your response. We left room in our demo project for Larry
>>Dobson's cook stove. He claimed a 99.9% combustion efficiency on some of
>>his 3-stage gasifier combustor prototypes! An EPA report is available on
>>his work. I think you would find it of interest, if you are not familiar
>>with his work. Have a wonderful day. Jorg
>>
>
>Would love to get a copy of any test data that Larry Dobson has to back up
his claim. Items of most interest would be: either O2 or CO2 content of flue
gas, and flue gas temperature. Also moisture content of wood. CO content of
flue gas would be the indicator for combustion efficiency. Also - is this
real-world or lab data, and what is the fueling protocol?
>
>Typical combustion efficiencies that we've seen on masonry heater testing
are in the 97 - 98% range. Overall efficiency, which is (combustion
efficiency) X (heat transfer efficiency) is of more interest, as are
particulate emissions. If you burn 20% moisture wood, you lose about 13% in
latent heat loss (turning water into steam). You can't recover that unless
you go to a condensing flue. In addition, you need to run some excess air
(about 100%) and you need some stack temperature, unless you have mechanical
draft. This puts the maximum theoretical overall efficiency that you can get
in the 80% range. We've seen about 76% - 77% with masonry heaters.
>
>Best........Norbert
>
----------------------------------------------------------
Norbert Senf 			email: 	mheat@mha-net.org
Masonry Stove Builders		website: www.mha-net.org
RR 5 Shawville			fax:	819.647.5092	
Quebec J0X 2Y0