Light-emitting diodes in greenhouses

Energy-efficient LED-based crop lighting in the horticulture industry

In order to produce vegetables and flowers in the winter months, when the days are short and the natural light intensity is low, growers often use greenhouses with artificial lighting. However, the standard current practice of lighting greenhouses with high-pressure sodium lamps is very energy-intensive. DNV KEMA has therefore started a ‘project line’ aimed at finding an energy-efficient alternative.

Since the beginning of the decade, light-emitting diodes (LEDs) have evolved from lowintensity signal indicators into powerful light sources. Modern LEDs are suitable for many applications, such as traffic signaling, street lighting, vehicle lighting, etc. Their advantages include relatively high efficiency, long life expectancy, small physical dimensions, low operating temperatures and ease of control. We therefore expect LEDs to develop further and become a light source with considerable potential for high-power lighting, as used in greenhouses where production continues all year round.

Project
> Investigation of the (energetic and economic) potential of LEDs for crop lighting
> Crop lighting with high-frequently pulsating LEDs; proof of principle
> Pulsating lighting in comparison with continuous lighting with equal light sums
> Position Paper Light: parameters for energy-neutral greenhouses with artificial lighting in 2020 and beyond
> Roadmap for the transition to LED-based crop lighting
> Unambiguous protocols for measuring the performance of crop lighting systems.

The projects are partly desk studies and partly experimental work. For the pulsating LED studies, special high-power, pulsating LED lamps with frequencies of up to 100 kHz have been developed. In cooperation with a plant research institute, growth experiments have been performed in a climate chamber, where, for example, the photosynthesis associated with continuous and pulsating lighting can be measured.

Objectives
The objective of the project line is to help the greenhouse horticulture sector find an artificial light source and to develop lighting systems that reduce net energy consumption, have a longer service life and greater spectral quality, and are associated with lower total ownership costs. The intention is to gather and present relevant information that encourages industrial producers/vendors to start their (own) product development projects once the potential has been demonstrated.

Clients
> Dutch Ministry of Agriculture, Nature and Food Quality, the Netherlands
> Dutch Horticulture Board (Productschap Tuinbouw), the Netherlands

Project coordinator
> DNV KEMA, the Netherlands

Project partner
> Wageningen University and Research, Dept. Horticulture, the Netherlands

Project details
> Duration: 2004 – 2010