Wood Stove Decathalon underway in Washington, D.C.

The Alliance for Green Heat’s Wood Stove Decathalon is underway at the National Mall in Washington, D.C., an event during which twelve teams from the U.S., Denmark, New Zealand, Austria and Finland are competing for the title of the cleanest, most efficient and innovative wood stoves.

Experts from a U.S. EPA-accredited wood stove test lab are on site conducting extensive  emission and efficiency testing using mixed hardwood, which is being cut, weighed and tested for moisture content prior to being used in any of the stoves.

The winner will be chosen by an expert panel of judges who are inspecting stove designs, components and construction to assess durability and the potential of innovative technological features.  John Ackerly, president of the Alliance for Green Heat, said stoves are being tested and judged in five areas—efficiency, emissions, affordability, consumer appeal and innovation. “Three of these [areas] are pretty objective; the judges don’t have much of a say for those. Affordability is harder to determine because some aren’t on the market and don’t have retail prices.”

“We had hoped to test each stove three times, because when doing this kind of testing—especially with cord woods—you get variability,” said Ackerly. “We think we’ll only be able to test each stove two times, just because the mechanics of the testing has gone a little slower than we thought. “

So far, testing has yielded some extremely interesting results, Ackerly told Biomass Magazine, which was on site for the event. “For example, the Wittis is number one for efficiency, but number ten for emissions,” he said. “The Austrian one (Ofenbau and Feuerstellen) is doing very well, and that’s a technology that was actually invented 400 years ago, they have just refined it.”

Niels Wittus, team captain of Wittus-Fire By Design, said there isn’t a clear answer for the odd tests results—a very good efficiency rating but higher emissions—but many factors can play a role, particularly the amount of wood being put into the stove.

“The fueling protocol was the big debate we had,” said judge Norbert Senf of the Masonry Heater Association. “This just hasn’t been done before. If you test with EPA, there’s a very prescribed fueling protocol. Here, to make it challenging, we’re trying to duplicate real world conditions. What people are going to want to do is stuff the firebox full of wood, so we’ve been doing 12 pounds of wood per cubic foot for loading. That turned out okay for largest stoves, but puts the smallest stoves—like Wittus’s, which is the smallest—at a disadvantage.”

 “We did try a smaller fuel load and it did better,” said Wittus.

Acklery said that during the next round of testing, competitors will be allowed to use less wood. He added that stoves are being tested at optimal conditions. “We’re using all dry wood, we’re not operating on the lowest air setting—which consumers often do—and we’re taking snapshots, as the testing equipment gets a 15-minute reading of the emissions. The manually operated stoves do well when tuned into sweet spots, but unless you manually adjust through the burn, it’s tough to beat the automatic stoves.“

Cordwood is a complex, complicated fuel, particularly when used on a domestic scale, emphasized Senf. “When you have a small stove and put a piece of wood in, the size, geometry, species, and density can have an effect on the stove’s performance.”

The issue of complication stems from the fact that the U.S. has no firewood standardization, unlike Austria, where there is no debate as to what firewood is, he said. “I manufacture masonry heaters and during start-up, if there are any problems, 90 percent of the time it’s the wood.”

“We don’t have the same wood culture than they do in Europe,” Wittus added. “That’s what we need to teach people.”