Energy saving by LED lighting in greenhouses

Summary:

High-tech greenhouses, equipped with heating, lighting, and CO2 enrichment of the air, are major consumers of energy, which results in considerable carbon emissions. Light-emitting diodes (LEDs) are a novel technology for greenhouse lighting, which has been promoted as a potential solution to the energy problem of illuminated greenhouses. This thesis explores how LEDs can be used to save energy in illuminated greenhouses. The main questions it investigates is how much energy can be saved by transitioning to LEDs and how LEDs will influence greenhouse energy use in future scenarios. The approach used is a process-based modelling approach, based on GreenLight: a new, open-source model for illuminated greenhouses growing a tomato crop, available at is offered in an open source format at https://github.com/davkat1/GreenLight. Based on this model, it is predicted that transitioning from the currently used high-pressure sodium lamps to LEDs at equivalent intensities would result in a 40% reduction of the lighting energy input and a 10-25% reduction of the total greenhouse energy input. However, LEDs could also be used to increase the lighting intensity of the greenhouse. The scenarios explored in this thesis predict that increasing the lamps' intensity without modifying the control strategy would result in higher energy consumption and lower energy efficiency of a greenhouse. Based on these results, the thesis discusses some of the possible consequences of the widespread adoption of LEDs, and offers further recommendations to reduce the energy use and environmental impacts of intensive greenhouse horticulture.