LED-lit urban farms aim to transform blighted cities with jobs, fresh food article tells about an interesting application for LEDs: A group of high-tech urban pioneers is using LEDs to power a large indoor vertical farming system in Newark, NJ. When complete, AeroFarms‘ latest urban agriculture system is expected to enough produce pesticide-free greens and herbs to feed over 50,000 people while using 3% of the space required by conventional dirt farming.
The so-called “Aeroponic system is a type of hydroponic technology that grows plants in a mist. The seeds are embedded within a cloth medium where they are germinated and exposed to with LEDs which emit specific wavelengths of light for more efficient photosynthesis and less energy consumption.
What types of LEDs are needed for urban agriculture system? A grow light or plant light is an artificial light source, generally an electric light, designed to stimulate plant growth by emitting an electromagnetic spectrum appropriate for photosynthesis. Grow lights either attempt to provide a light spectrum similar to that of the sun, or to provide a spectrum that is more tailored to the needs of the plants being cultivated.
Plants do not effectively use the entire spectrum of light. LEDs allow production of bright and long-lasting grow lights that emit only the wavelengths of light corresponding to the absorption peaks of a plant’s typical photochemical processes. There are multiple absorption peaks for chlorophyll and carotenoids, and LED grow-lights may use one or more LED colors overlapping these peaks. Here is graph from EarthLED GrowLED™ Series LED Grow Lights page:
Often blue LEDs are preferred, where the light has a wavelength in the mid-400 nm range (blue). For growing fruits or flowers, a greater proportion of red LEDs is considered preferable, with light very near 600-640 nm(red). So you can make greenhouses glow with blue and red. LEDs can be easily adjusted. By varying the output power of individual colors, the grower can simulate seasonal light changes over a multi-week growing cycle: more blue light mimics the summer sun (vegetative phase), and more red light simulates the sunlight in the fall (flowering phase).
Research is rapidly advancing in the horticulture industry that indicates LED-based solid-state lighting (SSL) might boost productivity in greenhouse and plant-factory operations and reduce energy consumption. More and more, plant scientists are integrating LEDs into their research programs to meet their needs for a specific light spectrum and to reduce the operational cost of their controlled growth environments.