The air temperature in a greenhouse on a sunny day often exceeds the optimum temperature level for the growth of crops. Therefore, there are frequent occasions when it becomes necessary to discharge the excess heat. This has given rise to the development by some investigators of an underground heat exchange system for heating greenhouses which utilizes this excess heat. The efficiency of this
... [Show full abstract] system is influenced by many variables and the available experimental data on such a system are insufficient for good design. The goal of the present research is to obtain the fundamental knowledge necessary to plan such a system. Performance tests of a greenhouse located in Kawanishi city in Japan (lat. 34° 47'n. and Long. 135° 23'e.) were carried out without growing crops during the cold season. This greenhouse is a new type, equipped with a heat collector inside the north wall designed to decrease the heat loss through it. The solar radiant energy and the temperatures of the air and of the ground at several locations in the system were measured. The response of the quantity of stored or recovered heat to the variation of the insolation was determined from these experiments. Furthermore, these results were compared with the numerical solutions of the computer model.