Transmission and Distribution of Photosynthetically Active Radiation (PAR) from Solar and Electric Light Sources

Abstract

This paper discusses the development and initial testing of a solar plant lighting system which collects, transmits and distributes photosynthetically active radiation (PAR) for controlled environment crop production. In this system, solar light, or light from an electric lamp, is collected by refl ector optics and focused on the end of an optical wave guide cable. The light is fi ltered by the selective beam splitter to reject non-PAR (λ < 400 nm and λ > 700 nm) from the light path to minimize the introduction of heat into the plant growth chamber. The PAR (400 nm < λ < 700 nm) is transmitted to the plant growth chamber where the light is distributed uniformly over the growing area. The lighting capability of the system was evaluated for solar and electric light sources. Based on the results we conclude that the solar plant lighting system with a supplemental electric light source is a viable and effective concept for space based crop production.