By: Deborah Johnson Wood
A Portage organic grower is the first to heat its greenhouses using a new hybrid solar/geothermal system invented by Holland-based GMB Architects-Engineers. Last summer, GMB installed the solar/geothermal system at Elzinga and Hoeksema Greenhouses. The system incorporates 200 eight-foot by four-foot ground-mounted solar collectors.
The greenhouse, which covers four acres, is heated by 60,000 gallons of 180-degree water circulated through a closed-loop pipe system. Heating the water using a natural gas boiler costs $400. In extremely cold weather, the heat may last only a couple of hours and then the water must be re-heated.
By comparison, the electricity to run the hybrid geothermal system is just $67 for 60,000 gallons, but the water only reaches 120 degrees.
“We need to supplement it using the gas boiler,” says Mark Elzinga, greenhouse owner. “But we’re only heating the water for that extra 60 degrees instead of 180 degrees.”
Typical geothermal systems pull heat out of the ground and put it in the building. In the summer it does the opposite, putting the heat back into the ground.
Because greenhouses need heat about 10 months a year, very little heat is re-deposited in the ground in the summer. To pull enough heat the following winter, the system requires a large heat exchanger—which carries a large price tag.
“With our hybrid system, solar collectors capture the sun’s energy in the summer and heat the ground,” says Steve Hamstra, vice president. “The ground holds the heat until it’s needed in the winter, acting as a huge thermal battery. We can store millions of BTUs. One advantage is that the system uses a smaller, less expensive heat exchanger.”
Mark Elzinga adds, “I’m excited about this system. We spent a lot of money on it and we feel that alternative energy is definitely part of our future.”
Source: Steve Hamstra, GMB Architects-Engineers; Mark Elzinga, Elzinga and Hoeksema Greenhouses
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Deborah Johnson Wood is development news editor for Rapid Growth Media. She can be contacted at [email protected].
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