Nocturnal Warming of Greenhouses using Solar-Heated Water

Beginning in 2006, the National Institute of Floricultural Sciences (NIFS) of the National Agriculture and Bio-oriented Research Organization (NARO) in Tsukuba City, Ibaraki Prefecture, has been testing a new system developed to warm greenhouses for vegetables and flowers using water heated by solar energy.

In this system, the greenhouse is covered with three layers of film. The space between the outer and middle layers is filled with air, while water circulating between inner and middle layers is heated by the sun during daylight hours. The warmed water is then stored in an underground tank and a pump is used to recirculate it when the temperature cools at night.

The water temperature in this system can be kept at around 14 to 15 degrees Celsius, even in winter, and the heated water is pooled in a 30-centimeter-deep thermal storage tank placed at a depth of 10 centimeters underground. This temperature is sufficient to grow strawberries without any additional heating. For flowers, although supplementary heaters are needed, heating costs can be cut drastically. For example, if the system is introduced for rose cultivation, heating costs are expected to be reduced by 60 to 70 percent from when heavy-oil heaters are used.

Because greenhouse culture requires substantial amounts of heavy oil for heating, the recent upsurge in oil prices is putting farmers under increasing economic stress. With the aim of promoting the system widely, the Laboratory of Cultivation Technology, the Department of Production of the NIFS, which developed the system, is endeavoring to reduce costs in cooperation with manufacturers.

http://flower.naro.affrc.go.jp/index-e.html

Posted: 2006/04/23 01:13:59 PM
Japanese version