Extending the growing season to year-round in a Northern climate, and using only renewable energy to do so, Minnesota organic farmer Steven Schwen, explains how his thermal banking greenhouse works, and with the help of the Sustainable Agriculture Research and Education (SARE) grant, how it came into being.
"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."
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