Using LED lighting to reduce energy costs by 50%

By making use of LED lighting in greenhouses, the energy consumption of tomato growers can be reduced by 50%, thinks Leo Marcelis, Professor of Horticulture and Product Physiology at Wageningen University. Eight doctoral candidates and three postdoctoral students will conduct research to make this possible. Technology Foundation STW and ten companies have agreed to fund the research, as was announced on November 18, 2014.

Switching from pressure sodium lights to LED lighting already saves 25 percent of energy consumption, probably even 30 percent in a few years’ time. Marcelis thinks another 30 percent might be saved on the electricity bill by placing LEDs more sensibly, by using different colours of light and giving them the right intensity and by using varieties that are better adapted to energy-efficient lighting. A total of 60 percent could thus be saved on electricity. Further savings can be made by clever use of LED light for controlling humidity in greenhouses. Because LEDs give off little heat themselves, the nursery will have to be heated. A net energy saving of 50 percent is realistic, Marcelis states.

Light and heat separated
Since LED lamps do not become hot, they can be placed between the tomato plants. By allowing the light to shine on the sides of the plants, much can be gained. What colour light can best be used in different phases, must be examined. Of great importance to the grower is that the plant uses the extra energy from the optimized photosynthesis to produce fruit, and not just additional leaf. One tomato variety will show a different light response than another, so that is looked at by researchers as well.

Humidity management in greenhouses changes
The humidity in greenhouses will change when using LED lighting. Using light colours affects stomata and may increase the resistance of plants to disease. Under sunny conditions, stomata are best opened to absorb CO2, which is then converted to growth of the plant. Open stomata, however, also means more evaporation and thus more humidity in the greenhouse - and a greater risk of fungal diseases.

Conversely, on cold dark days and during the night, energy can be saved by making sure the stomata are more closed. During these moments, much heating is spent to keep humidity stable. By reducing evaporation in these moments, energy can be saved.

Participants and financiers LED it be 50%
In the project, entitled LED it be 50%, Wageningen University is working with the universities in Utrecht, Leiden, Delft and Eindhoven. Wageningen University also includes several groups in this study: the chair groups Horticulture & Product Physiology, Farm Technology and Wageningen UR Plant Breeding. In addition, there is cooperation with growers organization LTO Glaskracht Netherlands, Philips, plant breeders Rijk Zwaan, Nunhems and Bejo, automation companies HortiMax and B-Mex, cultivation companies Van der Lugt Plantenkwekerij and Westlandse Plantenkwekerij and research institute Wageningen UR Greenhouse Horticulture.

Source: WageningenUR