Tuesday, January 26, 2010

Sustainable Energy: Thermal Banking Greenhouse Design

Source: Cooking Up A Story (CUPS)

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.

As you watch the video, you’ll appreciate the level of detail Schwen provides about the greenhouse’s design and construction. In addition, he has made the design drawings available for reference (PDF), and viewers are encouraged to download those and follow along as Schwen talks about the construction process. Note that in this set-up, it’s more about what you don’t see underground, than the greenhouse structure itself!

Schwen views this technology as a key component of his farming operation, particularly in this time of global climate change and energy insecurity. He feels this project moves him closer to his ultimate goals of energy independence and self-sufficiency.


To view another CUPS video about Steven Schwen, click here.

To read more about Schwen's NCR-SARE Farmer Rancher grant project, visit the SARE online reporting website here.

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