FOCUS ON ENERGY: QUESTIONS AND ANSWERS

Answers provided by Dick Hill, a retired emeritus professor of engineering at the University of Maine

Jessica Gosselin, Hersey asks: What are the available options for a LARGE wood furnace-stove with Btus ranging anywhere from 100,000 to 250,000?

This would be going inside a very large metal building. Any information you could give me would be very much appreciated.

I am sure the local stove shops can provide some information. Kerr Heating Co. of Parrsboro, Nova Scotia, makes a 100,000 Btu unit. I am not sure that it has an EPA rating. Here is a generalization on all wood stoves: The best stove (cleanest, most efficient, etc.) will burn a large fraction of each fuel load in the first hour of operation. A large firebox with long duration burns will be inefficient, and polluting. One way out is to burn the wood in a two-step process. Hire a mason to build a Dutch oven from brick. Feed the exhaust into a traditional heat exchanger. Let the Dutch oven replace the oil burner in a traditional furnace or boiler. The basic problem in wood burning is carburetion – the mixing of the air and the fuel. Both gas and oil burners are very good at this; but wood burners – particularly those with big fuel boxes, tend to distill much of the volatile energy of the wood into the chimney, resulting in wasted energy, creosoting the chimney and polluting the atmosphere. I have an excellent EPA-approved stove, but the combustion chamber is very small: about 7inches by 9 inches by 16 inches. I feel like Humphrey Bogart and the African Queen.

It takes constant attention. But it is very efficient and very clean.

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