Greenhouses of the future will be lit with LEDs
According to Professor Liisa Halonen from the School of Electrical Engineering, in coming years the sodium vapour lamps currently used in greenhouses may be replaced by LED lamps. LED lamps would reduce energy consumption at greenhouses and aid plants to grow abundantly.
“During recent years, development of LED lamps has been tremendous and is continuing to speed up. If you are planning lighting for your greenhouse today in just six months time vendors will be able to offer even better LED lamps,” explains Halonen.
Light from LEDs is a targeted therapy for plants
Liisa Halonen compares light from LED lamps to a targeted therapy. People can be treated so that the right amount of drugs is targeted at an exact point of pain and not equally to the entire body. With LED lamps, we can provide plants with exactly the kind of light they need; the correct colour, targeted at the right spot and at the right time.
Factors other than light, such as humidity and temperature, must of course also be taken into account in greenhouses, but the correct type of light can bring about savings and improve plant growth.
“The colour of light affects qualities such as the shape of a plant as well as its weight and rate of growth,” explains Paulo Pinho a researcher at the School of Electrical Engineering’s Lighting Unit. However, different plant types have different requirements. The spectrum that suits salads may not be suitable for cucumbers.
For example, a study at the Lighting Unit is looking into the different effects of red and blue light on the blooming of strawberries. A correctly selected spectrum can significantly affect a plant’s quality and even its health promoting attributes.
“LEDs also make it possible for us to have an effect on a plant’s nitrate content, the amount of vitamins it contains and its antioxidants,” Halonen assesses.
Smaller greenhouses, decreased energy consumption
When driving along dark roads one may come across buildings that are shining balls of light. They are large greenhouses lit with traditional sodium vapour lamps and in which energy constantly goes to waste. Currently, greenhouses are major energy guzzlers.
“Greenhouses constructed today are massive buildings measuring several metres in height, in which small salads are grown. Greenhouses lit with LEDs could be considerably smaller, as plants would receive optimal targeted light,” Halonen explains.
It is also possible to control the amount of light from LED lamps according to the daylight entering a greenhouse. Paulo Pinho has developed a DLC system (DynamicLightingControl) with which to control LEDs. When the system is connected to a daylight sensor energy consumption can be regulated constantly. When a greenhouse receives plenty of daylight, there is no reason to use excessive amounts of energy.
“Reducing energy use and improving plant quality! These are our goals,” Halonen sums up.
Text: Tea Kalska