Optimal Supplemental Lighting Control for an Extended Photoperiod in Controlled Environment Agriculture

Abstract

In this paper, a new optimization problem is formulated for supplemental lighting control using light-emitting diode (LED) fixtures in greenhouses. The proposed optimal control formulation is based on only Daily Light Integral (DLI) that can be applied for generic crops in contrast to other approaches in the literature that use Electron Transport Rate (ETR) function, which in practice is more complex (and in some cases impossible) to approximate. Moreover, the duration of photoperiod can be extended in the proposed formulation that can be employed along with sunlight prediction, for which a learning-based algorithm is given to find an optimal solution. Finally, results using realistic data for lettuce are provided demonstrating the effectiveness of proposed formulation to regulate photosynthetic photon flux density (PPFD), minimize the cost of electricity used, and/or minimize demand charge, independent of approximating/knowing ETR function.