Evaluation of Coaxial Pipes for Basal Heating as Alternative for Energy Saving in Heating System for Leafy Vegetables

Protected horticulture is a high energy-demanding sector where the optimization of energy use and cost for heating facilities are strategic to achieve high environmental and economic sustainability of productions. The main aim of the work was to evaluate coaxial pipes, used for basal heating, as an alternative system for growing crops with small canopies such as leafy vegetables. For the tests, coaxial pipes were lied on the substrate surface in the cultivation benches of the greenhouse. In a separate area, a traditional (air-burner) heating system was installed to heat the whole greenhouse air volume. The set temperature was maintained at 15 ℃ by means of thermostats positioned at canopy level in the basal heating system and at a height of 1.00 m above the canopy in the traditional system. No significant difference was detected between the two systems in terms of produced yield while the energy use efficiency of the basal heating systems was significantly enhanced compared with the traditional heating. Indeed, the monitoring of temperatures by means of data loggers in both systems, confirmed that coaxial pipes used for basal heating can guarantee constant temperature at canopy level and thermal energy saving.