Reconfigurable LED Lighting System Development: Potential Energy Savings for CEA

Abstract

Electrical cost, primarily for lighting, is one of the largest factors inhibiting the development of “warehouse-based” controlled environment agriculture (CEA). In a jointly sponsored collaboration, we have developed a reconfigurable LED lighting array aimed at reducing the electrical energy needed to grow crops in controlled environments. The lighting system uses LED “engines” that can operate at variable power and that emit radiation only at wavelengths with high photosynthetic activity. These light engines are mounted on supports that can be arranged either as individual intracanopy “lightsicles” or in an overhead plane of lights. Heat is removed from the light engines using air flow through the hollow LED strip mounts, allowing the strips to be placed in close proximity to leaves. Different lighting configurations depend on the growth habit of the crops of interest, with intracanopy lighting designed for planophile crops that close their canopy, and close overhead lighting intended for erectophile and rosette crops. Tests have been performed with cowpea, a planophile dry bean crop, growing with intracanopy LED lighting compared to overhead LED lighting. When crops are grown using intracanopy lighting, more biomass is produced, and a higher index of biomass per kW-h is obtained than when overhead LEDs are used. In addition, the oldest leaves on intracanopy-grown plants are retained throughout stand development, while plants lit from overhead drop inner-canopy leaves due to mutual shading after the leaf canopy closes. Research is underway to increase the energy efficiency and automation of this lighting system. This work was supported in part by NASA: NAG5-12686.