Experimental investigation of the energy needs for a conventionally and an infrared (IR)-heated greenhouse.

The potential advantages of heating greenhouses by infrared (IR) heaters, instead of conventional hot air, are examined experimentally. Measurements of indoor and outdoor conditions during a typical cold night and whole thermal period in Central Greece are taken in two experimental greenhouses using conventional and IR heating respectively. Data confirm that, the conventional system inside air and cover temperature remains always higher than the temperature targeted for the plants. On the contrary, with IR heating, inside air and cover temperatures are several degrees lower than the desired temperature sustained at the plantation level, and that this temperature difference increases proportionally to the drop in outside temperature. Since all thermal losses are almost proportional to the inside and outside temperature difference it is surmised that IR heating systems successfully implemented may present significant advantage over conventional heating setups. Direct measurements of energy consumption for the two test cases indicated 35-40% savings for infrared heated greenhouse. Besides, infrared heating contributed to improved total quality of the cultivated lettuce.