Effects of infrared radiation (IR) on growth parameters of eggplant cultivation and greenhouse energy efficiency

Greenhouses are an exceptionally energy consuming sector of rural production with important contribution in the environmental imprint. This is because they are complex and sophisticated productive systems of intensive exploitation and require optimal management of radiation, heating and cooling. Energy consumption for greenhouse heating represents a serious concern for greenhouse operators throughout Europe that is further aggravated by the present oil price. An alternative method of heating the plants in a greenhouse is the use of infrared (IR) radiation. Infrared radiation heating systems possess the advantage of high directional control and focused compensation of energy losses, appropriate for creating local temperature conditions in thermally unprotected spaces like greenhouses. The advantages of infrared heating are verified and demonstrated in an experimental greenhouse with eggplant cultivation. The objective of this research is to investigate the effect of infrared radiation on growth parameters of eggplant. Extensive experimental results are presented from a full cultivation period inside two identical, small scale experimental greenhouses, with IR and forced air heating system, correspondingly, in South-West of Peloponnese, Greece. Eggplant (Solanum melongena L.) is used as the test crop for a three months' period. The design, energy performance and plant growth results from the two greenhouses are presented, regarding the effect of IR heating to the cultivated plant. The produced data include solar radiation, relative humidity, and greenhouse indoor air temperature and plant growth. Results are compared to conventional cultivation. The implementation of an IR heating system in a greenhouse for eggplants production had satisfactory results, establishing a smooth distribution of the temperature at the canopy, while inside greenhouse air temperature was maintained at lower values than in the conventionally heated greenhouse. Quantitative results on plant growth and yield have been collected, and the favourable conditions resulted in better plant growth than in the conventionally heated greenhouse.