Monday, December 8, 2014
by David Brooks
|Tom Butcher from Brookhaven Lab,
second from right, tests an automated
stove from New Zealand. Ben Myren,
left, did R&D work on it.
I don’t think very hard when I light up the old wood-burning stove in my basement. Turns out, that might be a problem.
“Combustion technology is incredibly complex. Numerous chemical engineers, combustion engineers, mechanical engineers around the world are constantly trying to understand the intricacies associated with combustion. It is absolutely not what you and I would think – just light a match … especially when you want to get clean combustion and use wood efficiently,” said Rob Rizzo, manager of the Renewable Thermal Program for the Massachusetts Department of Energy Resources.
Rizzo was among the organizers of the 2014 Stove Design Workshop held in November at Brookhaven National Laboratory in New York, the latest in a number of attempts to add some high-tech wizardry to that staple of New England life, the wood stove. (For details, see forgreenheat.blogspot.com/2014/11/rookie-wood-stove-makers-get-highest.html)
Why tinker with something as well-established as wood stoves?
Because, like me, most people don’t think too hard when using them, which makes them inefficient and polluting.
We use green wood or wet wood, and we fiddle with the damper in the wrong way, causing partial combustion and thus more pollution.
The Stove Design Workshop, like a national Stove Design Challenge in 2013 that featured two New Hampshire entries, wants to find technology that can better cope with our stupidity.
The five finalists in the design workshop used a variety of techniques to work around people, including oxygen sensors that control fuel-to-air ratio, a common emission-control technique in cars, and a New Zealand stove that has a “barometrically operated variable choke venturi tube” to control the amount of combustion air entering a stove, particularly at lower burn rates.
“The whole concept with the design challenge is to come up with solid-wood stove that eliminates the human interface. Basically hit a start button and walk away; that is the concept we’re aiming at,” he said.
This already happens with pellet stoves, of course, which is why pellets has led a wood-burning renaissance for building heat.
The drawback is that they burn pellets made of compressed sawdust rather than the wood I can snag for free off my property, especially after the Thanksgiving snowstorm knocked down so many big limbs.
The lure of free fuel means that a lot of people still burn non-pelletized wood for some or all of their heat, although it’s not clear how many.
I have never been able to find good data about people who use cordwood (a.k.a. “roundwood”) as their principal heat source, partly because it’s hard to pin down. I, for example, use it only as a minor supplement of the pellet stove in the living room and our oil-fired furnace.
Rizzo said he didn’t know any data either, but he said that wood stoves remain important, especially in western Massachusetts.
Just as important as convenience is cleanliness. Wood stoves can produce a lot of pollution, particularly fine-particle soot, that is a health hazard. This is particularly a problem around Keene, which has a lot of wood-burning stoves and a geography that traps air in certain weather conditions.
New Hampshire has used rebates to get people to turn in their old stoves for cleaner versions, although with limited success.
But those cleaner stoves aren’t all that great; they’re little more than old stoves with catalytic converters in the stovepipe. Hence the push to build a better mousetrap, so to speak.
“It’s exciting to see new ideas coming forward. We have some educated guesses but we need to do better,” Rizzo said.
“We need to collect more data, about efficiency, emissions, consumption volumes, and also source of wood, sustainability of wood source, quality of wood source. Because rural America is always going to be burning round wood.”