Controlled Environment Agriculture (CEA) systems significantly enhance crop yields per unit area in comparison to traditional open-field farming methods. Moreover, they contribute to reduced water consumption and offer extended and more predictable growing seasons. While CEA systems show promise in meeting urban vegetable demand, the question remains what the required inputs are (water, fertilizer, energy, labor) for different systems (vertical farm, greenhouses) in different climate locations. In this work, an easy-to-use transient energy model that simulates the internal microclimate of CEA systems is developed. The microclimate will include changes in temperature, humidity, water, nutrient, and carbon dioxide while also computing the energy costs associated with conditioning the space and electricity. This model will also accurately map the leaf temperature and hence compute the transpiration water loss accounting for the spectra of different artificial light sources. The energy model will be linked to a functional crop growth model that can simulate the yield of the plant over multiple growth cycles and quantify water and nutrient uptake. The potential of the developed model is demonstrated by performing simulations of year-around greenhouse operation within the U.S. Two climates categorized into hot, and cold based on annual temperature are selected for the simulation of tomato production. Results indicate that supplemental lighting energy requirement ranged between 128-160 kWh/m2-year across the selected climate zones to achieve target yield in a given duration. Overall energy consumption ranges from 200 - 400 kWh/m2-year. Overall, the supplemental lighting requirement makes upto 75 percent of the total required DLI and provides comparable improvements in biomass compared to yield in greenhouses without supplemental lighting. Finally, the model indicates that upto 90 percent of total supplemental lighting requirements require light intensities in the combination of 250 and 500 µmoles m-2 s-1 to satisfy the additional DLI requirement. However, a higher lighting intensity of 1000 µmoles m-2 s-1 is required sporadically at night during winter between October – March in the northern latitudes. Overall, this model integrates energy, temperature, nutrition, and crop yield considerations for various crops and acts as a useful predictive tool for assessing operational costs based on target yield and duration of growth for greenhouses operating in any given climate.
