Energy Conservation and Solar Heating of a Central Florida Commercial Nursery

摘要

This project investigated solar heating and energy conservation strategies in an older central Florida greenhouse. Emphasis was placed on cost effective techniques that were easy to retrofit without disturbing plant production. Techniques were developed to install an insulating air inflated double layer of clear polyethylene. The polyethylene is placed underneath the existing fiberglass roof and is fastened to the top cords of the roof trusses. Without being directly exposed to the harsh Florida sun, the useful life is expected to double that of external double poly roofing systems. The feasibility of low cost trickle type solar collectors for soil heating was studied. A large 1344 ft exp 2 Rutgers University style collector was built and tested. Soil heating utilizing hot water from solar storage was provided by a grid of PVC pipe suspended from the plant benches. Using entirely solar heat, this system maintained soil temperatures 3 to 5 exp 0 F above non-heated soils. To match the 10 exp 0 F temperature rise common with propane powered soil heating systems, the effective heat exchange surface area would need to be doubled and water temperatures boosted 10 to 15 exp 0 F. The importance of efficient heat exchanger design to utilize low grade hot water is stressed. (ERA citation 10:000412)