Cooling Capacity Assessment of Semi-closed Greenhouses

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Title: Cooling Capacity Assessment of Semi-closed Greenhouses
Creators: Lee, Wee Fong
Contributors: Keener, Harold M.; Ling, Peter P.
Keywords: heat storage
heat recovery
decision support tool
benefits of closed greenhouse
northern climate
net solar radiation
growing season extension
cooling systems
Issue Date: 2011-05-02
Series/Report no.: Food, Agricultural, and Biological Engineering. Graduate student poster competition, 2011
Abstract: Energy and labor are the two largest expenditures of greenhouse operations. High energy cost and large CO2 footprint associated with greenhouse heating have motivated research activities in the areas of energy conservation and alternative energy. Dutch researchers have demonstrated energy saving potential of closed greenhouse operation in the Netherlands. This study hypothesized that semi-closed operation was better suited for Ohio and other US northern climate regions. A decision support tool has been developed to assess energy recovery potential and other benefits of semi-closed operations. The results showed that a greenhouse can be closed 90% of the time using only 50% of the maximum cooling capacity required to keep a greenhouse closed 100% of the time. Also, heat recovered from cooling operations of a closed greenhouse in Ohio can contribute 23-98% of total annual heating needs. This study also found large disagreement when using a commonly used tool for heat loss calculation. The tool performed poorly with a 30% error under nighttime clear sky conditions. The evaluation suggested that accurate estimation of net solar radiation transmittance is important, e.g. a 5% change of the transmittance caused a 9% prediction performance shift. In addition to the originally designed functions, the decision support tool is extended to predict the performance of external shade curtains for cooling purposes. The development of this tool has established a solid foundation for the evaluation of greenhouse energy management strategies, including feasibility studies of alternative energy sources, and of sizing of greenhouse heating and cooling equipments.
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