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New wave of greenhouses use PCM to regulate temperature

Ben Welter - Monday, December 12, 2016

Traditional greenhouses are not all that green. Poor insulation and inefficient heating and cooling systems boost energy consumption and operating costs.

Colorado-based Ceres Greenhouse Solutions is among the growing number of companies offering commercial growers and backyard gardeners a better way. Ceres has designed and built hundreds of energy-efficient, year-round greenhouses since 2011. Key features include the use of free solar energy for both heating and cooling, improved insulation and phase change materials. Ceres says it is the first greenhouse company to integrate PCMs into its residential and commercial installations.

"We specialize in passive solar design — maximizing the use of solar energy for year-round heating," says Lindsey Schiller, director of marketing and business development. "These [greenhouses] use a combination of insulation and strategic placement of glazing (glass or plastics). The result is a more insulated and energy-efficient greenhouse capable of growing year-round in harsh climates with very little energy use. We also are well known for using a ground-to-air-heat exchanger we call the GAHTTM system, as well as integrating other sustainable / energy-efficient / renewable heating cooling systems."

Ceres greenhouse wall with PCM facingCeres uses film panels filled with phase change material to provide passive temperature control. The panels, sized to fit in a typical stud bay, help even out day-night temperature swings and reduce the need for active heating and cooling. The peak melting point of the PCM varies by climate.

"We usually recommend 60 F for cold-climate greenhouses with cold-tolerant crops where heating is needed, 80 F for hot-climate areas with heat-tolerant crops where cooling is the primary focus and 70 where both is desired," Schiller says. The panels are typically installed on the inner face of the north wall, as shown here.

The company originally used Phase Change Energy Solutions' BioPCM but recently switched to Insolcorp's Infinite R, a salt hydrate. Ceres sells the PCM for $3.50 a square foot. 

“One of the major things we have to think about is the durability of the packaging, particularly since it is exposed to direct light,” says Schiller. “We were concerned about the lifetime of BioPCM and switched to make sure we had a durable product that will hold up in a greenhouse environment.”

Another method for passive temperature regulation: fish tanks. Ceres recently announced a partnership with Colorado Aquaponics, a company that specializes in pre-fabricated aquaponic greenhouses. Ceres now offers kits that pair space-efficient aquaponic systems with highly efficient year-round greenhouses. Can PCMs play a role in these hybrid greenhouses?

"Yes," says Schiller, describing the technologies as complementary. "Greenhouses usually need several strategies to help control temperatures … not just one."

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