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Comparison of Greenhouse Dehumidification Strategies in Cold Regions

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Applied Engineering in Agriculture. 31(1): 133-142. (doi: 10.13031/aea.31.10723) @2015
Keywords:   Cold region, Greenhouse dehumidification, Heat exchanger, Mechanical dehumidifier.

Abstract. Two dehumidification methods, including air-to-air heat exchangers and mechanical refrigeration dehumidifiers, were compared with dehumidification using a conventional exhaust ventilation system. The comparisons included capital cost, operating cost, durability, ease of installation and maintenance, and effectiveness for different seasons of the year. The heat exchangers were more effective for moisture control during cold and mild seasons than during humid and warm periods, while the dehumidifiers were effective in controlling the indoor moisture year-round due to their independence from outside air conditions. While the dehumidifiers consumed the highest amount of electrical energy thus resulting in the highest cost, they consumed the lowest amount of total energy, defined as the sum of the electrical energy consumption and the resultant heat loss from the greenhouse due to dehumidification. Although the heat exchanger method consumed approximately 81% of the total energy consumed by the exhaust fan dehumidification system due to the sensible heat recovered from the exhaust air, the total costs of the two methods were similar due to the lower electrical energy consumption by the latter. Considering a 10-year payback period, dehumidification by the exhaust fan system was the most cost-effective method with the lowest capital and maintenance cost. However, it is only effective during cold and mild seasons, and not during warm weather conditions. Mechanical refrigeration is recommended for summer dehumidification, and both methods could be used during different seasons to achieve good moisture control year-round. After the application of dehumidification, the crop loss rate was reduced by 1.6% to 2.5%, which led to an annual revenue increase of $3,000 per year. Although the average dehumidification cost was approximately 10% of the annual heating cost of the greenhouse, when considering the reduced crop loss and yield increase, dehumidification is strongly recommended.

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