Abstract
An experimental plant factory using flourescent lamps was developed, and its performance, productivity, and power consumption were investigated through cultivation tests of lettuce. The results are as follows.
(1) Using a close illumination method with fluorescent lamps, three stages of the planting bed could be vertically stacked for cultivation of seedlings and two stages for growth, and the compact cultivation system could be realized. When all 42 flourescent lamps of 110 W/stage were illuminated, the mean light intensity on the floor was as high as 650μE/m2/s (45 klx) .
(2) The environmental conditions were adjusted by an ON/OFF control using a programmable controller. The air temperature, relative humidity, CO2 concentration, electric conductivity of hydroponic solution and pH were found to be regulated in the range of, respectively, 25±0.5°C in light period/20±0.2°C in dark period, 70±5%, 900±50 ppm, 1.3± 0.1 mS, and 5.5±0.5 under conditions of light intensity of 330μE/m2/s, lighting time of 16 hr/day, and wind velosity of 0.5 m/s.
(3) The lettuce (Kuroha and Greenwave) grew to weigh more than 75 g in 29 days, and the production of an experimental facility was 120 stocks/day. At this time, the seedling weighing about 0.25 g grew acceleratedly, and the fresh weights increased by about 40 times in 9 days.
(4) The daily average power consumption throughout the year was about 300 kWh (45% for lighting, 35% for air-conditioning, and 20% for others) . The power consumption for lighting and the total power consumption for the production of lettuce was found to be about 1.1 and 2.5 kWh/75 g-fresh weight respectively, and energy was saved as compared with the conventional apparatus. However, about 75% of total energy was spent on the growth unit, so to reduce the production cost it seems effective to cut the input of energy and equipment to the growth unit, and invest particularly in the seedling unit which contributes greatly to growth promotion.
