Journal of the Society of Agricultural Structures, Japan

This study describes the use of water heating by fermentation heat recovery from a suction-vented composting system of dairy farming. We elucidated the characteristics of water heating using exhaust gas from a composting facility with fermentation heat recovery, which generated a calorific value of 30 kW using two heat exchangers (Exp. 1), and we also determined the capacity of a heated water supply of drinking water for dairy cows in full-scale dairy farming (Exp. 2). In Exp. 1, the flow rate was 1–14 L·min⁻¹ and temperature of the heated water was 48.3–31.0 ℃, and the heat was used to heat the water up to 1.41 MJ·min⁻¹. The heat exchange efficiency reached approximately 90 % under these conditions, and the overall heat transfer coefficient was stable at 80–90 W·m⁻²·K⁻¹. In Exp. 2, to construct a system for supplying drinking water to a milking herd of 118 cows, water at 33.3 ℃ was supplied at 14.4 m³·d⁻¹ (122 L·d⁻¹ per head of cow). During this period, the amount of heat used for heating the water was 1630 MJ·d⁻¹. In addition, to ensure that the fermentation heat recovery facilities remained in good working conditions, we treated or used the dew condensation water generated by the heat exchange process.

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In February 2014, numerous greenhouses were damaged by heavy snow in the Kanto-Ko-Shin region. We surveyed pipe-framed greenhouses, reinforced pipe-framed greenhouses, angle-steel frame greenhouses, steel frame greenhouses, glass houses, and greenhouses for fruit trees in Gunma, Nagano, Yamanashi and Tochigi prefectures, and classified them by failure mode and cause of failure. For single-span greenhouses, the covering net on the roof prevented snow sliding off. For multi-span greenhouses, snow load near valley gutter did not melt sufficiently causing collapse of the structure. Overfl owing water from the gutter decreased the bearing capacity of soil and settlement of foundations. Strong wind and unmelted snow of past snowfall affected the loading condition of snow on the roof. There were frequent failures of columns in greenhouses with insufficient bracing. For greenhouses without bracing, the connections between column and beam, and column and foundation were the major cause of failure. In the most fragile structure, the connection between column and beam was by only one bolt. In this structure, a large bending moment at the weak connection between column and foundation caused failure. In order to increase the strength of the greenhouse for snow load, we propose the development of a new attachment that can be easy to put on and take off temporary bracing of the structure before a storm. Also proposed are the modification of the connection between the column and foundation using concrete and the addition of the covering film at the valley gutter.

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