Supplemental Terrestrial Solar Lighting for an Experimental Subterranean Biomass Production Chamber

The long-term supplemental terrestrial solar lighting made available to the Biomass Production Chamber (BPC) located in the Subterranean Plant Growth Facility (SPGF) at The University of Arizona was determined for two cases where two types of Solar Irradiance Collection, Transmission and Distribution System (SICTDS) were used for the facility. Databases for hourly solar irradiance incident upon Tucson, AZ compiled over a 12-year period from 1987 through 1998 were used to calculate the projected average instantaneous PPF within the BPC per hour and per day throughout the year. The results showed that replacing the available solar irradiance within the BPC as delivered by the Himawari SICTDS in June would require either 97.7 W m⁻² of HPS lighting or 185.9 W m⁻² of CWF lighting supplied continuously for 450 hrs. In energy terms, these would be equivalent to 44.0 kW-hr m⁻² for the HPS lamp and 83.7 kW-hr m⁻² for the CWF lamp. For a whole year, the equivalent energy expenditures would be 0.4 MW-hr m⁻² for the HPS lamp and 0.7 MW-hr m⁻² for the CWF lamp. Replacing the available solar irradiance within the BPC as delivered by the OW SICTDS in June would require either 229.9 W m⁻² of HPS lighting or 437.4 W m⁻² of CWF lighting supplied continuously for 450 hrs. In energy terms, these would be equivalent to 103.5 kW-hr m⁻² for the HPS lamp and 196.8 kW-hr m⁻² for the CWF lamp. For a whole year, the equivalent energy expenditures would be 0.9 MW-hr m⁻² for the HPS lamp and 1.7 MW-hr m⁻² for the CWF lamp. Meanwhile, a plant lighting regime in the BPC, consisting of 100 or 200 μmol m⁻² s⁻¹ of PPF at 16 hours of photoperiod per day and operated for a whole year, could be supplemented with available solar irradiance on average by 54.3% or 48.9%, respectively, when using the Himawari SICTDS. Also, a plant lighting regime in the BPC, consisting of 200 or 400 mmol m⁻² s⁻¹ of PPF at 16 hours of photoperiod per day and operated for a whole year, could be supplemented with available solar irradiance on average by 57.8% or 34.1%, respectively, when using the OW SICTDS.