Analysis and performance of a greenhouse with water filled passive solar sleeves

Abstract An experiment was conducted to study greenhouse heating using a passive solar system based on water as a collection and storage medium. In this system, the water is stored in inexpensive transparent polyethylene tubes, placed on the soil of the greenhouse, between the rows of the plants. In a greenhouse with tomato plants (2.2 m high) and passive solar sleeves the average minimum temperature was up to 3–4°C higher than the outside air and about 1°C higher than the control greenhouse (without any heating system). During January the solar energy collection factor of the greenhouse with the solar sleeves increased by up to 90%. A heat transfer model was tested and a computer model was derived for calculation of the storable heat in the passive solar sleeves. The agreement between the experimental results and the calculations based on the heat transfer model was excellent. Theoretical calculations show that using solar sleeves in a conventionally heated greenhouse could save up to 8% input energy. In a greenhouse with small plants the performance of the passive solar sleeves is much higher than in a greenhouse with tall plants. Passive solar sleeves with less water but the same effective surface release most of the heat early during the night.