LED (Light Emitting Diode) lighting is gaining popularity in the field of agriculture, especially in animal husbandry, greenhouses, and indoor farming, where it provides several benefits over traditional lighting methods such as being maintenance-free and having a higher energy efficiency—LEDs convert more than 80% of the electricity they consume into light and consume 60% less energy for the same lighting intensity. However, the biggest advantage is spectrum control: different crops and animals require different wavelengths of light for optimal growth, yield, and well-being, and LED lighting can provide the exact spectrum needed with the added benefit that this spectrum can be optimized in real-time. This ability to fine-tune the color temperature makes LED lighting a cost-effective solution, even though its initial cost may be higher than that of traditional lighting methods.
The Importance of LED Lighting in Animal Husbandry
LED lighting is used in animal husbandry to improve animal welfare, growth, and productivity. Proper and adequate lighting is crucial for animal well-being and growth, and LED lighting can provide the exact spectrum of light needed for different stages of animal development.
For example, in poultry farming, UV and visible light LED lighting is used to regulate the circadian rhythm of chickens. The right amount and spectrum of light promotes increased egg production, reduces stress, and improves the overall welfare of the birds. As birds have a different visual response than humans (tetrachromatic rather than trichromatic receptors in the retina), they can perceive ultraviolet light that we cannot see. They use this ability to identify each other to establish their pecking order, and hens utilize it to assess the healthiness of their brood (healthier chicks have denser feathers that reflect UV light more strongly, so a mother hen can quickly identify weak from strong chicks). In low UV light conditions, poultry cannot use this extra sense and so become uncomfortable and even aggressive. Ideally, the illumination level should be 30–50 lux over 80% of the space (poultry also have a wider field of vision (300°) than humans (180°), and therefore the whole space needs to be well-lit with no dark or shaded areas that could be perceived as being threatening to the birds).
Fig. 1: Comparison of avian and human phototropic response
In dairy farming, LED lighting can be used to increase milk production. Dairy cows require a specific amount of light per day for optimal milk production (typically 150 lux for 16 hours per day), and LED lighting can provide the exact spectrum and intensity needed. Tests show that a 5–16% increase in milk yield can be achieved when the lighting is optimal compared to too dark or short lighting times. Like poultry, cows have a very wide field of vision and become unsettled by dark or shaded areas in view, thus broad, even illumination is required. It is also important to have a period of low lighting (<50 Lux) to allow the cows to rest properly. As cattle cannot see red light, LED lighting can also be switched to the red spectrum during this time to allow farm workers to check on the cows without waking them.
Fig 2.1: “Night-time” illumination is visible to humans but not to cattle.
The Benefits of LED Lighting in Horticulture
As previously mentioned, LED lighting offers precise spectrum control, which means that the light can be tailored to the specific needs of plants; the classic grow lamps radiate more strongly in magenta and blue colors. However, different wavelengths of light are required for different stages of plant growth, and LED lighting can provide the optimal spectrum for each stage. Another advantage is that it produces less heat and infrared radiation than traditional lighting methods, thus reducing the risk of heat stress on plants under high illumination levels. This is especially important in indoor farming and greenhouse cultivation, where temperature control is critical.
Fig 3: Vertical indoor farming used artificial light.
Indoor farming involves growing crops in an indoor environment using purely artificial lighting, which allows for year-round crop production. Vertical farming involves growing crops in stacked layers, making it a space-efficient option for urban areas. LED lighting provides the necessary light for plant growth in each layer, reducing energy consumption and heat output. In hydroponic farming, plants are grown in a nutrient-rich water solution without soil, and LED lighting can offer the right spectrum of light for photosynthesis, allowing plants to grow faster and produce higher yields; it can also be customized to match the specific light requirements of different plant species. A variation on soil-less horticulture is aeroponic farming, where plants are grown in an air or mist environment, and aquaponic farming, where plants are grown in a water-based environment with fish. Again, LED lighting is used to provide the necessary spectrum of light for optimum plant growth and to support the growth of aquatic organisms. Indoor farming is becoming increasingly popular, especially in urban areas where space is limited. Here, LED lighting plays a critical role, as it provides the necessary light for plant growth while reducing energy consumption and heat output.
On a larger scale, LED lighting is used in greenhouse cultivation to provide the necessary light for plant growth, regardless of weather conditions. Artificial lighting is also used to extend the growing season, which means that crops can be grown outside of their normal growing season.
A Practical LED Solution for Agricultural LED Lighting
The following schematic shows a concept for a very flexible and low-cost solution for large-area indoor LED lighting for agriculture. The heart of the system consists of a cheap single-board computer (SBC), such as a Raspberry Pi or an Arduino with a WiFi communication module and a small LCD (optionally with a touchscreen), plus a RACM1200 digital power supply capable of delivering 1000W in a sealed, dust-tight, and fan-less enclosure.
The RACM1200 is ideal for this application because it has a separate “always on” 5V output that will continue to power the SBC even when the main output is completely switched off; furthermore, it includes a separate 12V fan output, used in this example to boost the logic level output of the I/O pins on the SBC to a higher voltage signal that can switch the power MOSFETs more efficiently and at full power.
The LED luminaires are operated at a safe 48VDC, meaning that there is no risk that animals can be electrocuted if they chew on any exposed wiring and ensuring that the luminaires can be hung from the ceiling at the optimum height for even illumination although they are within easy reach of farm workers. In vertical farming, where each stack is individually lit at close quarters in a wet or damp mist environment, worker protection requires such safe extra-low voltage wiring. Of course, the RACM1200 is continuously short-circuit proof and will not be damaged if the output is shorted.
Fig. 5:Varying the PWM signal for each bank of LEDs changes the apparent lighting (color temperature)
The color temperature of the lighting is set by modifying the PWM signal from the SBC for each channel, offering more red, more blue, whiter, or more UV illumination as necessary. The LEDs are switched with a PWM signal at above 200Hz so that poultry cannot be disturbed by the flicker (humans cannot see flicker at 100Hz or above, so many cost-effective LED power supplies have a very high output flicker at double the mains frequency of 50Hz or 60Hz. This can be a problem for birds who can perceive lighting flicker up to 190Hz. The output of the RACM1200 is flicker-free and the PWM dimming is at a higher frequency than the animals can see).
The whole system can be fitted into an enclosure no larger than a shoebox, even though the RACM1200 is powerful enough to light a whole barn or greenhouse by itself (output power 1000W without fan cooling). Another advantage is the wide input voltage range of 80-264VAC so that even unstable or erratic main supplies to remote barns or distant outhouses are not a big problem.