ISHS Acta Horticulturae 148: III International Symposium on Energy in Protected Cultivation
SURFACE-HEATING GREENHOUSES WITH REJECT WARM WATER |
| Author: | P.N. Walker |
| Abstract:
Surface Heating is a technology for heating greenhouses with reject warm water by applying that water over the outside surface of the greenhouse. If the greenhouse is to be maintained at 18°C then 30°C water is more than adequate to supply all the heat needed. If 15°C water is the warmest available this water can still be used to considerably reduce the conventional heat requirement because it warms the outside surface of the greenhouse. Experimental surface heated greenhouses were tested at two Illinois Power Company plants. A near-commercial surface heated greenhouse has been constructed at a power plant in Canada. It began operation in the 1982–83 heating season. A mathematical greenhouse heating model was used to predict the annual heating energy consumption of a 4000 m2 glass greenhouse with and without a surface-heating system for a range of water, air and greenhouse temperatures similar to conditions at the Baldwin Power Plant experimental greenhouse. The annual energy savings for surface-heating ranged from 22.5% for water 5°C cooler than Baldwin water temperatures to 80.4% for water 5°C warmer than Baldwin. Using 1980–81 prices, annual monetary savings corresponding to the energy savings were 11.2% and 71.5%. A present-value analysis showed that the surface heating system more than paid for itself under all but one of the conditions studied. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
