Master of Science, The Ohio State University, 2010, Food Agricultural and Biological Engineering

Leading Dutch researchers reported significant benefits to closed greenhouse systems. Ooteghem (2007) simulation studies of optimal control in a closed greenhouse environment predicted 52% heating fuel saving and 39% increase of tomato crop yield using a heat recovery system whose major components included heat pumps, heat exchangers and aquifers. Opdam et al. (2005) reported 19% primary energy saving, 22% yield increase, 80% chemical reduction, and 50% irrigation water saving for tomato production in a closed greenhouse. Although the Dutch researchers successfully demonstrate year-round operation of closed greenhouses, their success benefited from the mild weather and availability of aquifers, not always the case for other geographical regions. Results of this study using Ohio conditions estimated that 90% and 92% of CO2 loss through cooling and dehumidification ventilations when an elevated CO2 level of 800 ppm must be maintained. This study also found that for Wooster, Ohio to achieve economical year-round closure, due to the larger weather variation and lack of accessibility to aquifers, a better economical return would be expected with semi-closed designs that allow the greenhouse to vent when the heat load is approaching a certain percent of peak levels. For example, a 50% peak load design can meet the cooling and dehumidification needs of a closed greenhouse for 92% and 90% of the year, respectively. Also determined in this study was the amount of heat which can be recovered with thermal storage. Potential recoverable heat of a closed greenhouse at Wooster, Ohio can contribute up to 23%, 25% and 98% of total heating needs of the year, 2006, with 1-day, 2-day and year-round thermal storage capacities, respectively. The models used for the above analyses were evaluated using data collected in a greenhouse located at Wooster, OH. Convection and infiltration heat loss prediction were validated during cloudy and clear sky nights. The results gave prediction disagr (open full item for complete abstract)

Committee: Peter P. Ling PhD (Advisor); Harold M. Keener PhD (Committee Member) Subjects: Agricultural Engineering; Engineering