Abstract
Greenhouse heating using heat pumps has become widespread recently due to soaring oil prices. Due to lack of time, some methods of heating have been implemented without any definite technical background. A typical example is the so-called “Eco-mode” system, which collects energy from air inside the greenhouse, and air passed through an evaporator is circulated between the space above the thermal screen and the glass. In the present study, the consumption of electricity for a system in “Eco-mode” was compared with that of a system in “Normal-mode” which utilizes outside air as an energy source. It was found that the consumption of electricity in “Eco-mode” was approximately 40 % larger than that in “Normal-mode”, and an unanticipated large electricity loss occurred when heat lost to the outside decreased. From heat loss calculations, the system in “Normal-mode” had the largest electric energy utilization coefficient, followed by the system that utilized the air between the outside cover and the inside thermal screen. The smallest coefficient was found for the system that utilized inside air, since this system is equivalent to an electric heater. The coefficient for “Eco-mode” was between the last two systems.
https://ror.org/05n9nqv74 
