Posted on January 26, 2010 - by Lisa Madison

Sustainable Energy: Thermal Banking Greenhouse Design

This post and accompanying video was originally published by our friends at Cooking Up a Story.

This is the second in a series of “how-to” videos showcasing the knowledge and creativity of farmers who are have worked with the Sustainable Agriculture Research and Education program (SARE)—either as grant recipients, cooperators or leaders. In the first video, Jeanne Carver (Imperial Stock Ranch, Eastern Oregon) described her ranch’s approach to value-added marketing. Now we turn to the Midwest where Steven Schwen of Earthen Path Organic Farm (Lake City, Minnesota) has built an innovative greenhouse that allows him to extend his growing season while reducing energy costs. SARE’s Farmer-Rancher Grants program provided critical assistance for Schwen in the beginning phases of his project.

At Minnesota’s latitude, farmers who can extend their growing season have a distinct advantage in the marketplace: By offering a product outside the “normal” growing season, they can receive a higher price. That’s what Schwen has done with his greenhouse vegetable production, starting earlier in the year with seedlings of warm-season vegetables (tomatoes, cucumbers, basil and peppers), and continuing production into the fall and even the winter months when he grows cold-tolerant crops such as salad mix, cilantro, scallions and carrots. Season extension is a common enough practice, but what makes Schwen’s operation so unique is the added innovation of thermal banking, which significantly reduces the energy costs of running a greenhouse for cold-season production. Schwen’s simple description of thermal banking is that it’s like a savings account: Instead of money, you save (or store) energy for future use. In this case we are talking about the heat that accumulates in a greenhouse during the daytime, especially on sunny days.

For more, click through to Cooking Up A Story