Cost Effective Solar Heating for Season Extension of Vegetable Production Lantz, W.D.* Malone, 1; Swartz, P.S.2; H.J. 3 1Extension Educator, University of Maryland Extension, Mt. Lake Park, MD, 21550 2Physicist and Software Developer, Garrett Engineering and Robotics Society, McHenry, MD, 21541 3Owner and Operator, 5 Aces Breeding, Oakland, MD, 21550 PurposeDetermine if commercially available thermal solar Tank Temperature Abstract increased 50oF in 5 Tank Temperature drops 39oF inpanels used to heat swimming pools can be Local food production is limited by the growing days three days = 258,960 Btu of heat season. While high tunnels protect crops from adverseeconomically used to heat a greenhouse structure weather and increase the heat units crops receive, high tunnels cannot keep crops at ideal growing temperaturesfor vegetable production in early spring and late during extended cold weather in early spring and late fall. Heating a high tunnel with traditional fuels would befall in Garrett County, Maryland. 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 Methods connected to an 800 gallon in ground water tank. Fountain pumps are used to pump water through the solar panels and Outside Temperatures in move water from the tank through radiators to heat theA solar thermal heating system composed of greenhouse. Heat from the system was used in April, May, the mid 30oF October and November. The system produced 3.1 millioncommercially available swimming pool heating BTU of heat and 1.6 million BTU of heat was required from a backup propane heater to keep the greenhouse at apanels was used to heat water. The heated water minimum of 50oF. This period of time would allow farmers to 1 BTU = ∆1oF / lb water confidently start growing 30 days earlier than is currentlythat was stored in an 800 gallon insulated water practiced and would allow production to continue 30 daystank attached to the greenhouse. Water from the 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 Resultstank was circulated through a truck radiator to for most crops. The cost for the system installation and use is o 100 F water with 3-4 sunny days around $35 per million BTU which is less expensive than theheat the greenhouse to maintain a minimum o o operation and installation of propane heat. Maintain 55 F for 3-4 days without sunshinetemperature of 50 F. A microprocessor with inputfrom sensors, controlled the operation of the Worked best in the late fall months of Octobersystem. The microprocessor also recorded data and Novemberand exported the data to a server on the internet Project supported through a grant from October of 2011- produced over 1 million BTUs Northeast SARE Partnership Grant Fund.allowing remote control of the system and viewing A full report of the project activities can of heat requiring no additional heat from the be found by searching the SARE reportsof the system on the internet. The data from the at: propane back up heater http://mysare.sare.org/mySARE/Projectsystem allowed for the calculation of the BTU’s of Report.aspx. For the time period of the study - February 1,heat produced from the solar thermal system. 2011 to December 31, 2011, the system produced nearly 6 million BTUs of heat which is 23’ X 25’ 4’ X 8’ Swimming Pool Thermal Heating Panel equal to 66 gallon of propane for a savings of Greenhouse 800 Gallon Water Reservoir $158.40 at a propane cost of $2.40 per gallon. Evaluation Microprocessor Control The solar thermal heating system cost $2,000 for Truck Radiator use to Distribute Heat this application. At an annual cost savings of $158.40 the system will have a payback of 13 years.
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