Passive Solar Mobile kiln demonstrated

June 21, Oregon - Oregon State University has gone on the road to show small-scale timber growers and handlers how they can save money drying small lots of wood.All it takes is a partnership with the sun, in a passive sort of way.

For several years OSU forestry extension has been touring Oregon with a portable, passive solar dry kiln.

"It's been all around the state," said Scott Leavengood, OSU Extension Service forestry specialist and director of the Oregon Wood Innovation Center on campus.

"It's kind of like a little greenhouse," said OSU Extension Service forester Mike Bondi. Being a passive solar system, there are no photovoltaic cells on the unit. Instead, several panes of plexiglas are used to capture the sun's energy to heat up the small drying chamber. The only electricity required is that used to operate a fan that moves humid air out of the kiln.

The little mobile kiln was designed to show people how passive solar can save energy dollars as well as add a green premium to their wood.

The idea of mounting a passive solar kiln on a trailer and hauling it around the state to show passive solar's potential came from Extension Service wood products specialist Jim Reeb, who, along with the OSU Forest Research Lab, designed the kiln. Molalla master woodlands manager Monte Waldorf designed the plexiglas panel arrangement, which always faces south.

The 8-foot by 20-foot portable kiln can hold up to 1,500 board feet of lumber.

"If a small woodland owner had a portable sawmill, or had someone cutting wood for him, this would be a way that they could dry the wood for exterior or interior use," Leavengood said.

Bondi said that energy savings are one of the main selling points of the kiln. "It takes a whole bunch of energy to (operate) a conventional kiln, whether you run it with steam or electricity."

The solar kiln's drying time depends on a number of factors, including weather, species of wood and desired moisture content.

Last winter Kevin Kaster, owner and operator of Kaster's Kustom Cutting in Mulino, Ore., took a batch of western red cedar down to 6 percent moisture in about six weeks using the kiln.

"And that was in the winter when there wasn't a whole lot of solar heating going on," Bondi said.

"Air drying would have taken twice as long," Leavengood said.

The kiln is mounted on a trailer so that it can be hauled from site to site. In stationary mode the cost would be much lower, as the trailer added around $5,000 to the cost, Leavengood said.

Also, if the kiln were on a concrete slab, loading it would be much easier, with the wood to be dried easily wheeled into and taken out of the end of the unit, instead of out of the back. On a slab, the kiln could also be longer and wider. The cost of a stationary unit with the same measurements of the OSU demo model would be similar to building a garage, Leavengood said.

He added that with a stationary unit less costly tempered glass could be used. "We used poly-carbonate, pretty expensive stuff, which is similar to plexiglas, because we're hauling this down the road."

As for the energy savings, they could be as high as 50 percent.

The kiln, which is believed to be the only portable one in the country, has been at numerous sites around the state, including Astoria, Bend, Burns, Corvallis, Klamath Falls, Oregon City.

Leavengood said that one of the questions he's asked most often is: "Is the kiln feasible in western Oregon, where there isn't much sun during a good part of the year?"

He tells people the drying process will be a little bit slower, but it's better than keeping the wood outside and a lot cheaper than conventional kiln drying.

OSU has built a website - owic.oregonstate.edu/solarkiln - that tells all about the kiln, including plans on how to build one.

The website was recently upgraded to include tracking data on when the kiln was loaded, with what species, what the original moisture content of the wood was and the weather conditions. Also depicted will be data on when the wood was removed from the kiln and the state of dryness.

The kiln is presently being used to dry some black walnut slabs in Aurora at Toby Sart's woodworking business, Toby J's. In addition to custom carvings, Sart also makes wood furniture and is drying the black walnut for tabletops.

Kaster, who custom cuts high-end logs and is certified by the Forest Stewardship Council, said the passive solar dryer adds a green dimension to his business.

Freelance writer John Schmitz is based in Salem, Ore. E-mail: johns6869@msn.com.

Original Source:  Capital Press Oregon