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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASAE. Vol. 45(5): 1547–1558 . (doi: 10.13031/2013.11060) @2002
Authors:   D. A. Jack, T. Nakamura, P. Sadler, J. L. Cuello
Keywords:   Solar collector, Fiber optic cable, Advanced life support, Controlled environment, Hydroponics

Growing plants in an enclosed controlled environment is crucial in developing bioregenerative lifesupport systems (BLSS) for space applications. The major challenge currently facing a BLSS is the extensive use of highly energyintensive electric light sources, which leads to substantial energy wastes through heat dissipations by these lamps. An alternative lighting strategy is the use of a solar irradiance collection, transmission, and distribution system (SICTDS). Two types of fiber opticbased SICTDS, a Fresnellens Himawari and a parabolicmirror optical waveguide (OW) lighting system, were evaluated. The overall efficiency for the OW SICTDS of 40.5% exceeded by 75% that for the Himawari of 23.2%. The spectral distributions of the light delivered by the Himawari and the OW SICTDS were almost identical and had practically no difference from that of terrestrial solar radiation. The ratios of photosynthetically active radiation (PAR) to total emitted radiation (k) of 0.39 0.02 for the Himawari and 0.41 0.04 for the OW SICTDS were statistically indistinguishable, were not significantly different from that of 0.042 0.01 for terrestrial solar radiation, and were comparable to that of 0.35 for a highpressure sodium (HPS) lamp. The coefficients of variation (CV) of 0.34 and 0.39 for PPF distributions, both at 50 mm 50 mm square grid arrays, corresponding to the Himawari and the OW SICTDS, respectively, were comparable with each other but were both significantly greater than the CV of 0.08 corresponding to the HPS lamp. The average fresh weight or dry weight of lettuce grown in the solar chamber with either the Himawari or the OW SICTDS showed no statistical difference from the average fresh weight or dry weight of lettuce grown in the reference chamber with the HPS lamp. The results of this study suggest that an SICTDS could help reduce the electric power demand in a BLSS.

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