ISHS Acta Horticulturae 174: Symposium Greenhouse Climate and its Control
WIND DEPENDENT CONTROL OF GREENHOUSE TEMPERATURE |
| Author: | B.J. Bailey |
| Abstract:
Recent studies have indicated that average temperature may be a more important factor in determining plant growth than short term temperature variations. If so the greenhouse temperature could be controlled to minimise energy use but give the desired average value over selected time periods. As greenhouse heat loss increases linearly with wind speed, reducing the temperature below the required average value when the wind speed is higher than average, and vice versa, would provide a reduction in the total energy requirement. The potential of this form of temperature control for saving energy was investigated theoretically using a steady-state energy balance model with hourly values of temperature, wind speed and solar radiation. Compared to a greenhouse heated to a constant 15°C, controlling the temperature in response to wind speed gave a reduction of 5–10% in the annual energy requirement. The reduction was influenced by the time period selected for temperature integration, the amount by which the temperature was allowed to deviate from the required mean value, the change in greenhouse temperature per unit change in wind speed and the rate at which the greenhouse temperature could be increased by the heating system. | |
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