|Authors: ||C.E. Sams, T. Hayden, S. Amundson|
|Keywords: ||renewable energy, subterranean heating|
A study was conducted to assess the effectiveness of a subterranean rock-bed in heating and cooling a greenhouse and determine its capacity for saving energy.
Temperatures were measured throughout the experimental greenhouse and compared to a neighboring conventionally heated greenhouse.
Temperature data and energy use were taken from four periods: winter with no propane use, winter with supplemental propane use, summer, and an extended season combining winter and spring with supplemental propane use.
The rock-bed system alone was capable of increasing greenhouse temperatures by 5°C on average and at most by 14°C. The rock-bed in conjunction with supplemental propane use increased greenhouse temperatures by 8°C on average and at most by 15°C. During the warmer months, rock-bed cooling reduced greenhouse temperatures between 5-7°C. Propane savings due to the rock-bed were estimated at 41.4 MJ m-2, and a conservative total energy use was found to be comparable to the conventional system by using only 7 MJ m-2 more.
There is potential for further increasing savings by utilizing other renewable energy sources and optimizing the rock-bed system.
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