COST EFFECTIVE SOLAR HEATING FOR SEASON EXTENSION OF VEGETABLE PRODUCTION
Proposed by: William D.Lantz
Presenter: Lantz, W. D., Extension Educator, University of Maryland Extension, Mt. Lake Park, MD 21550
Local food production is limited by the growing season. While high tunnels protect crops from adverse weather and increase the heat units crops receive, high tunnels cannot keep crops at ideal growing temperatures during extended cold weather in early spring and late fall. Heating a high tunnel with traditional fuels would be very costly and not environmentally sound. The goal of this project was to evaluate the use of water heating solar panels designed for heating swimming pools to heat high tunnels. Five 4’ X 8’ solar panels were installed and connected to an 800 gallon in ground water tank. Fountain pumps are used to pump water through the solar panels and move water from the tank through radiators to heat the greenhouse. Heat from the system was used in April, May, October and November. The system produced 3.1 million BTU of heat and 1.6 million BTU of heat was required from a backup propane heater to keep the greenhouse at a minimum of 50oF. This period of time would allow farmers to confidently start growing 30 days earlier than is currently practiced and would allow production to continue 30 days longer in the late fall. While some supplemental propane heat was needed in this research to maintain 50oF, falling below that for short times at night would not be problematic for most crops. The cost for the system installation and use is around $35 per million BTU which is less expensive than the operation and installation of propane heat.