REDUCTION IN ELECTRIC-ENERGY CONSUMPTION FOR COOLING IN A PLANT FACTORY WITH ARTIFICIAL LIGHT
The commercial use of plant factories with artificial light (PFAL) is limited by its high initial construction and operation costs. The electric-energy consumed by air conditioner (AC), applied mainly for cooling, accounts for 15-35% of the total electric-energy used in a PFAL. To reduce this electric-energy consumption, an air exchanger (AE) with low electric power was used for cooling by introducing outdoor cold air. In this experiment, the indoor air temperature in two PFALs (floor area: 10.5 m2 each) was maintained at 25 and 15°C during photoperiod and dark period, respectively. In one PFAL, an AE (air flow rate: 250 m3 h-1) was used along with an AC (cooling capacity: 6.3 kW) to maintain the indoor air temperature at the set-point, the other without AE was the reference. The AE was used when outdoor air temperature was lower than Tf, standing for the highest temperature of outdoor air allowing into PFAL, 22 and 12°C during photoperiod and dark period, respectively. When the indoor air temperature could not be maintained at the set-point by using AE, AC was started. The results show that, when outdoor air temperature ranged from -4 to 12°C, the electric-energy consumption in the PFAL with AE was reduced by 24.6-63.0% and 2.3-33.6% during photoperiod and dark period, respectively, compared with the reference PFAL. A negative correlation existed between the reduction rate and outdoor air temperature in the range of -4 to 12°C. The results indicate that the electric-energy consumption for cooling could be reduced by using AE in combination with AC when outdoor air temperature is relatively low. Thus, during photoperiod and dark period, as long as outdoor air temperature is lower than Tf, using AE in a PFAL will be an effective way to reduce electric-energy consumption for cooling and the operation costs, especially during cold winter.
Wang, J., Yang, Q., Tong, Y. and Wei, L. (2014). REDUCTION IN ELECTRIC-ENERGY CONSUMPTION FOR COOLING IN A PLANT FACTORY WITH ARTIFICIAL LIGHT. Acta Hortic. 1037, 293-298
energy-saving, outdoor air temperature, air conditioner, COP, electric-energy use efficiency