A Rhino Grasshopper Plugin for Spectral Daylight Simulation & Analysis in Controlled Environment Agriculture

Abstract

Controlled environment agriculture (CEA) requires stable and accurate light for consistent photosyntheticplant production, with consideration given to both duration and quality. In agricultural lighting, light quantity is the most significant metric in plant production since it directly correlates to the photosynthetic activity necessary for plant growth. However, light quality, which describes the relevance of light in a given spectrum as it relates to the specific needs of a plant’s growth stage, is also important and has been shown to impact many other variables aside from growth, including flowering, fruiting, flavor, and color. CEA has experienced rapid growth and large-scale adoption over the last decade, standardizing the presence of artificial lighting and making lighting the greatest energy consumer within this sector. While lighting technology has seen increases in efficiency, including the ability to tune lights to specific spectra most suitable for plant production, attempts to build agricultural operations that rely solely on electric lighting have shown to be not economically viable and sustainable. Greenhouses, a form of controlled environment agriculture, utilize solar radiation as the primary light source for plant growth, relying on supplemental electric lighting only during reduced photoperiods of available daylight, such as during winter. Combining daylight with spectrally tunable LED lights offers the most promising area of energy reduction within CEA. However, most research is currently focused on the spectra of LED lights, with little consideration given to the spectra of daylight, which changes throughout the day. By accurately simulating the quality of light at the plant canopy from natural daylight and supplemental light sources, a hybrid model may be developed that offers deeper insights into not just quantity but quality. This project develops a modeling tool allowing daylight and electric light sources in a given controlled environment to be assessed for spectral qualities related to the region, climate, weather, building envelope, and surrounding context. By providing greater color accuracy of daylight at the plant canopy level, supplemental lighting for controlled environment greenhouses could shift from static to dynamic light output, reducing light in non-relevant spectra for a given plant phase and supplementing only specific spectra when necessary.