Power Gen from a residential boiler?

[gallen]

I have been interested by the Stirling cylce and the possible
applications for a few years now. Particulary, the improved
efficiency over traditional internal combustion engines. I have
recently plumbed in a wood furnace/boiler to heat my house. It has
been working great and saving me lots of money due to the increase
costs of oil. I have standard hydronic baseboard heat registers
through out my house that are connected to my boilers (i have a oil
boiler too). I would love to become independant or not as dependant
from the local electric company as well.
Is it possible to "piggy back" a stirling engine onto my wood boiler
to produce electricity? I suspect the costs may not make it worth
it, but is the idea any good?

Thanks,
Greg

[stan.hornbaker]

It's a good idea but at present the game isn't worth the chase.

Combined Heat & Power, CHP, units burn natural gas for domestic heating and the flue gases power a Stirling engine driven generator to provide electricity. Any power not used domestically is supplied to the grid with the proper connections and approvals.

There are no units specifically made to utilize the waste heat from a wood burning heater. Cost of the CHP's is something like $10,000 US.

[tmckissick]

Greg,

You're on the right track, however there is more to this question than whether something's available yet. The first issue is that since the Stirling would benefit more from the higher temp differential, it needs to receive the heat first with the boiler receiving it's waste heat. A really good Stirling 'could' start making usable power in the 650 F range, so that would be the temp of its waste heat which is still high enough to operate the boiler. Now the only problem becomes sizing the quantities produced vs. being used in each stage to maintain those temps. This would allow any heat source capable of sufficient quantities above that temp to efficiently supply the heat, electricity and possibly the cooling for a house. In addition to that, a good heat pump circuit can increase the differential by lowering the cold side another 60 deg from ambient or from a well. With a COP of >3.5 and these temps, the Stirling would make a significant positive power output. This is in development right now but it isn't available off the shelf yet because of the next reason.

The real delay is purely financial. The current perception of Stirlings is that they have been tried so often that that many failures couldn't possibly be incorrect. This isn't exactly accurate. New designs, materials and computer modeling have brought the virtual development capabilities to the masses. In my personal experience, it doesn't matter what the computer modeling results show, that perception problem still exists for the stage of raising prototype money. This has proven very expensive, since professional engineers, patent lawyers and machinsts didn't come cheap. So anyone looking for an off the shelf Stirling, you might consider supporting that stage of development.

Todd
todd.mckissick@charter.net

[gallen]

Thanks for the responses,
As i suspected, much needs to be done in terms of research to make my particular application feasible. I am a civil engineer and only know the basics regarding thermodynamics. It may be an attractive alternative to the masses some day, especially to those of us who live in the Northeast and Canada. 600 deg F is on the high end of a typical wood burning furnace, but it sounds like it has potential. If energy costs continue to rise, demand should go up, and perhaps the government will provide subsidies to alternative and renewable energy technology.

Thanks,
Greg

[jhdean]

Has anyone researched and had response from this German company about their solar and
wood pellet fired Stirling generators?

http://www.sunmachine.de/english/main.html

Thanks,
Jeff

[shep]

Greg,
I am doing the same research it appears you did over a year ago. I am also in the NE and will
have a wood fired boiler. I am wondering if you had any luck piggybacking a Stirling or not?
Thanks for any input.
Andy