一, Technical adaptability: How can LED plant lights be used in greenhouses with multiple spans?
1. The ability to control spectral precision: this solves the problem of illumination that isn't even in multi-span greenhouses.
Because they are so big and the covering materials let in different amounts of light (for example, plastic film lets in 85% to 90% of light, solar panels let in 75% to 80%, and glass lets in almost 100%), huge connected greenhouses tend to have unequal light distribution within. Traditional light sources, like high-pressure sodium lamps, have fixed spectra that can't be changed to meet the needs of the crop. LED plant lights, on the other hand, can provide customised spectra for different growth stages. For example, blue light (450-470nm) is needed to promote root development during the seedling stage, and red light (620-660nm) is needed to enhance flower bud differentiation during the flowering stage. For instance, the LED inter-plant lighting system from Guangdong Weizhaoye Optoelectronics changed the ratio of red to blue light from 3:1 to 3:1, which led to a 42.67% rise in the number of tomato fruits hanging in multi-span greenhouses and a 16.97% increase in the weight of each fruit.
2. Features of a cold light source: Getting around space limits and growing more plants in a smaller area
Multi-span greenhouses need to make the most of vertical space, but standard light sources like high-pressure sodium lamps have surface temperatures over 200 °C and need to be at least 1.5 meters apart. This means that only 60% of the light energy they utilise is used efficiently. LED plant lights stay cool to the touch, with a surface temperature of less than 40 °C. You may put them 10 cm away from the plants to light them up. They make the most of space by adding multi-layer schemes like canopy and inter-plant supplemental lighting. A linked greenhouse in Japan employs low-power LED top fill light and inter-plant LED light strips to enhance the density of lettuce plants by 30% and the yield per unit area by 45%.
3. Smart Control: Making the light environment change all the time
Greenhouses with several spans have to deal with complicated circumstances, like fluctuations in temperature from day to night and across seasons. Light sensors and IoT technology can be built into LED plant lights so that they can automatically change the brightness and spectrum based on real-time light intensity (PPFD value), CO₂ content, and other factors. For instance, the Three Think Plant Lighting Growth Lamp mimics the spectrum of sunlight at different times of the day and adjusts the lighting between the light compensation point (point B) and the light saturation point (point D) to make the leaves of cucumbers have 23% more chlorophyll and slow down their decay.
二, Economic feasibility: Can LED plant lights make costs and benefits equal?
1. The balance between the initial cost and the long-term savings on energy
LED plant lights cost 2 to 3 times as much as high-pressure sodium lights at first, but they are 50% to 60% more efficient at converting light into electricity (high-pressure sodium lights are only 30% efficient), and they last more than 50,000 hours (high-pressure sodium lights last 20,000 hours). For a one-acre connected greenhouse, a 400W LED system uses 1200 kWh of electricity per year, while a 1000W high-pressure sodium lamp system uses 3600 kWh. The LED system saves 1440 yuan a year on electricity bills, based on an electricity price of 0.6 yuan per kilowatt hour. LED systems can pay for themselves in 3 to 5 years, and using them for a long time can cut greenhouse operating expenses by more than 30%.
2. The immediate economic benefits that come from making more and better products
Regulating the spectrum of LEDs can make crops much more marketable. For instance, in a connected greenhouse where strawberries are grown, LED top lights and flower lights are used together to get three planting cycles per year, boost output by 50%, improve the sugar-acid ratio of the fruit, and raise the market unit price by 20%. LED fill light may also lower the amount of nitrates in lettuce by 15% and raise the amount of vitamin C in tomatoes by 18%. This meets the high-end market's need for quality.
3. Government support for policies and market movements
The "dual carbon" goal has led several areas to offer energy-saving subsidies for facility agriculture. For example, LED fill light systems can earn a 30% to 50% purchasing discount. The worldwide LED plant lighting industry is also predicted to increase at a rate of 15% per year, with a penetration rate of 75% by 2028. This will create a virtuous cycle of large-scale use to lower costs.
三, Being good for the environment: How do LED plant lights support green farming?
1. Low carbon emissions: in line with the goals of sustainable development
LED plant lights use only 40% as much energy as high-pressure sodium lamps. Based on a connected greenhouse of 10,000 acres, the amount of carbon dioxide released into the air each year is more than 100,000 tonnes less. Also, LEDs don't have any dangerous chemicals like mercury, which cuts waste disposal expenses by 60% and meets environmental requirements like EU RoHS.
2. Use less pesticides: keep pests and diseases at bay by exposing them to light
Pests and diseases can have trouble with their biological clocks when the lighting is right. For instance, blue light (450-470nm) can stop aphids from reproducing, and alternating red light (660nm) and far red light (730nm) can cut the number of tomato grey mould cases by 30%, cut the use of pesticides by 40%, and make production greener.
3. Adapting to Extreme Weather: Making Sure There Is Always Enough Supply
In the northern winter, when it is always gloomy and snowy, multi-span greenhouses don't get enough natural light, which means that crop yields drop by 20% to 30%. LED plant lights can give constant light, and when used with ground source heat pumps, they can control the temperature and light levels at the same time. This can increase cucumber yields by 2.3 times compared to growing them in the open air, making sure there is a steady supply of "vegetable baskets."
