‘Solar Wall’ Warms Up Wentzel Apiaries

By MREAOn 26 Feb 20164 Jun 2018

Shawn Wentzel is a third-generation beekeeper and owner with his wife Allison of Wentzel Apiaries in Twin Bridges, Montana. In addition to keeping bees and processing honey, they grow 350 acres of sainfoin hay and raise cattle. Bees are attracted to the sainfoin and use it to produce high-quality honey; and after the sainfoin flowers, it’s harvested and fed to the cows.

Several years ago Shawn and Allison reached out to Wayne Baker, owner of Baker Light Industries, a renewable energy business in Alder, Montana. At the time they were burning $8,000 worth of propane each year and looking for a way to reduce fuel costs. Wayne suggested a high-efficiency wood boiler. Today, the wood boiler saves the Wentzels $7,000 per year in fuel costs while providing the heat that they need for processing honey as well as heating their home, garage, shop, and greenhouse.

Shawn reached out to Wayne again this year when he started building a pole barn on the cattle ranch. The barn will be used to store a tractor, and it’s far from the nearest power line. Shawn was interested in either a heating or electric system to warm up the tractor enough to start it on subzero winter days. Shawn and Wayne discussed several options, including a wood boiler with an off-grid solar electric system to run the boiler’s pumps and fan. Ultimately, however, Wayne recommended a much lower-cost and lower-tech solution: a south-facing ‘solar wall,’ also known as a passive solar air collector, that would draw heat into the barn on sunny winter days.

When Wayne explained the idea, Shawn was concerned about summer: would the solar wall make the barn too hot? Wayne explained that a large eave over the solar wall would shade it from the high summer sun, while allowing it to be warmed in winter when the sun stays lower in the sky. Shawn plans on installing a wood stove in the shop for cloudy winter days when he needs more heat than the wall provides.

Wayne was able to construct the solar wall using only materials that Shawn had already purchased to build the barn, with just one addition: polycarbonate greenhouse glazing. The glazing was used to make a 8’x30’ window on the south-facing wall of the barn, starting four feet up the wall and reaching the eaves. The tin that would have covered the south wall was painted black and hung on the inside of the framing 11 inches behind the glazing. They left an 18 inch gap from the floor to the bottom of the inner wall, and left the top 18 inches of the clear glazing exposed along the top so light could get in. When the wall warms up, cold air is drawn in the bottom and the heated air floats out the top into the barn.

The solar wall was just completed last week, and the barn is still under construction. Shawn says, “I thought [the solar wall] was a pretty neat idea. If it works on this little building, we’ll put another one on a bigger shop we’re going to build in the next year or two.”