Electrical savings comparison of supplemental lighting control systems in greenhouse environments

Abstract. Greenhouse vegetable production can be optimized by properly controlling the conditions in the growing environment. Supplemental light and shade systems in a CEA greenhouse are typically controlled using manual control or time-clock control. Previous work describes a Light and Shade System Implementation (LASSI) that controls lighting to a consistent daily light integral (DLI) of photosynthetically active radiation (PAR) by predicting daily insolation. LASSI also schedules as much supplemental light as possible during hours when off-peak electric rates apply. Annual energy consumption, energy cost, and carbon footprint are compared in simulation for LASSI and simple threshold control with two parameter sets. The models include energy consumed for heating and supplemental lighting. Each controller is used in simulating greenhouses in four different climates using Typical Meteorological Year (TMY) data sets. Three crops are considered for their differing light requirements, lettuce, tomato, and floriculture. In each simulation, energy consumption, cost, and carbon footprint are shown to be significantly reduced by using LASSI.