Analysis of Electricity Demand during Nighttime Cooling and Establishment of Year-Round Energy Management Indices in a Solar-Light Plant Factory

Abstract

Investigations conducted in a solar-light plant factory cultivating tomatoes using air-source heat pumps revealed that nighttime cooling could be performed with less monthly electricity consumption and monthly electricity demand than those of heating. We proposed an energy management index （daily area intensity）， calculated monthly for one year, to evaluate the electricity consumed to maintain the required temperature environment in the cultivation facility. Moreover, we proposed an index （daily saleable yield intensity）， calculated for each month in the harvest period, to evaluate the compatibility between increasing the saleable yield and reducing electricity consumption. The electricity consumption per unit area and electricity consumption per unit saleable yield during cooling were approximately 40 ％ and 12 ％ of those during heating, respectively.