1992 Volume 76 Issue 10 Pages 523-529
We developed an experimental plant factory equipped with fluorescent lamps to illuminate plants closely and the inside wall coated with highly reflectable paint to use reflected light effectively (close illumination method). In this paper, saving degree of lamp energy of the close illumination method on lettuce cultivation was experimentally and theoretically investigated by employing this plant factory.
(1) The mean photon density on the cultivation panel (area of 12 m2) was as highas 650μEm-2S-1, when 42 fluorescent lamp S (110W) were installed 30 cm above the surface of cultivation panel to illuminate plants.
(2) The coefficient of utilization (U), which indicates the light utilization efficiency in this cultivation room of this plant factory, was about 1.7. The measured value of U is well coincide to the value calculated by Moon's equation, and was nearly 2.5 times higher than high pressure sodium lamps installed about 80 cm above the cultivation panel.
(3) The electric energy consumption for lighting and total electric power consumption for the production of lettuce (75gfresh weight) was about 1.1 kwh and 2.5kwh respectively. Thus, the electric energy consumption for lighting was about half that of conventional high pressure sodium lamps.
On the other hand, the lighting power consumption for the production of seedlings weighing about lOg and 0.2g was about 0.3 kwh and 0.06kwh, respectively.