Development of the Greenhouse Growing-System with Cooling and Heating Facility Using Geothermal Energy (I)

Vegetables Growing by Means of Night Cooling in Summer

Abstract

The purpose of this paper is to make sure if the cooling of greenhouse at night only in summer makes it possible to produce vegetables. The authors constructed an experimental apparatus constituting of a vapor compression refrigerator, an unit cooler, a vinyl greenhouse and air circulating ducts (Fig. 2). Spinach, lettuce, welsh onion and peas were grown experimentally.
A summary of the results were shown below.
1) It was considered that the estimated values of heat transfer coefficients and thermal conductivities used for design of the apparatus were appropriate, because the air in greenhouse was cooled to the desired temperature 15°C (Fig. 3).
2) In the open division, experimental vegetables almost died back during growing, furthermore, a few vegetables grew, but the products were not marketable, while in the cooling divisions, all of the vegetables were grown up satisfactorily by means of night cooling only and were harvested (Table 1-7).
3) In the cooling divisions, the optimal harvesting times of spinach, lettuce, welsh onion and peas were about 30, 70, 75 and 60days respectively after sowing.
4) From the above results, the authors conclude that vegetables production in summer was possible by means of cooling of greenhouse at night only.