Journal of the Society of Agricultural Structures, Japan

Greenhouse cooling systems with three types of heat pumps: air source-air supply, water source-air supply and water source-water supply types, are evaluated by hourly calculations based on a simple heat balance model. Cases considered are for the current 4 most typical greenhouses at 4 locations in Japan. Cooling requirements for two combinations of day and night cooling as well as two night only cooling set points are determined. Peak daytime cooling requirements are similar for all locations and greenhouse types and may be too great to justify fully meeting without any ventilation. Meeting half the full day cooling requirements with heat pump systems may be more practical. In this case the water source-water supply system is shown to require only one sixth the size heat pump unit relative to the other two types, due to the utilization of the cool water storage. This type system sized to meet 90% of night heating requirements can meet almost all night cooling needs. Even modest sized systems are shown capable of meeting cooling needs many hours of the year extending the opportunity for closed operation with carbon dioxide enrichment.

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This paper studies the establishment of a livestock barn adjacent to a biogas power generation facility. In the barn, electricity necessary for the management of livestock and the barn itself is self-supplied via biogas power generation alone, and as much surplus power as possible is sold to other power users. A breakdown of daily power consumption by dairy farmers in Hokkaido showed that ventilation fans accounted for the largest percentage (37 to 76 %; 41 % on average), followed by bulk coolers (4 to 37 %; 20 % on average). Power consumption on farms was influenced more by equipment operated for long periods than by the rated power consumption of individual pieces of equipment. Based on these findings, it is suggested that for equipment used over extended periods, reviewing how machinery that can be used flexibly is operated would support the reduction of overall power consumption and maximum power demand. Additionally, the use of ventilation fans, livestock waste treatment units and other types of low-capacity equipment during non-milking times resulted in lower maximum power demand.　Since the output of biogas power generators is stable throughout the day, the electric demand of barns facility is able to be covered mostly. It is important for barns with biogas generators to be applied the flexible operation system for equipments during milking, and to be able to supply the whole electricity at the farm using biogas generators.

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