Development and Testing of a Solar Greenhouse, with a Transparent-Heat-Insulating Collector Layer, and a Rock Pile Storage Unit

Abstract

The paper dealt with a solar greenhouse constructed at Hokkaido national expriment station located at 43°N, Japan. The greenhouse was designed and constructed at reasonable cost in such a way that it could be heated all through the winter without any “artificial” energy supply except the main source of solar energy.
The heat requirement could be reduced with energy conservation arrangements, such as double glazing air inflated house-covering, air inflated plastic film duct (i. e., collector) on the ceiling of the house and multiple movable inside film covering.
The dimensions of the greenhouse are 10.8m of length, 10.8m of width, and 3.5m of height. The solar heating system consists of a tall sidewall of the house, a 77²m double tube collector (a transparent outer tube with an inner acceptor tube) of polyethlene (or vinyl) film, and a 29m³ rock pile stsrage unit (insulated with 10cm of polystrene insulator) under the ground inside the house. The system worked well at the effective use of the beam radiation, diffuse radiation and solar radiation reflected from the ground, and re-use of lost heat from the house and from the storage.
In 1977 to 78 winter, the operation of the solar system were conducted. The system worked well to keep the vegetation area over 0°C, to prevent from freezing, even at the outdoor temperature of -26°C. A leafy vegetable variaty, “TAINA” grew well without any supplementary seat source auring in the cold winter.
In this system, solar energy was collected actively through the collector, and passively through the house and soil surface. In the coldest month, Feburary, the total useful heat gain was nearly in in the level of the heat leak from the house at night. The overall collector efficiency was around 30% in winter.