Knowledge Transfer: Commercial review of lighting systems for UK horticulture

The rapid development of high intensity lighting systems, including the availability of LED’s, has created a number of new opportunities for the use of artificial light in UK horticulture. In particular, LED lighting systems are viewed as being highly electrically efficient, potentially reducing the energy use of supplementary photosynthetic illumination. They may also offer defined spectral outputs to elicit specific plant responses.

 

A number of new lighting systems have been produced for and made available to the horticultural industry, primarily by Philips and European manufacturers, but also Phytolux in the UK. However, there is no comparative information of new lighting system electrical efficiencies or spectral outputs. There is also no comparative information on the impact of their luminaires. Potential implications of lamp life cycle, ease of maintenance and worker health and safety have not been widely considered. It is therefore not possible to make simple informed decisions on lamp selection for horticultural application.

 

If new lighting systems are highly electrically efficient, then there may be substantive capital cost benefits from installing a smaller and simpler wiring installation. Higher efficiency may also lead to additional secondary effects, such as impacts on total greenhouse energy loading / heating costs. Moreover, it is also known that LED light output efficiency is temperature dependent per se. These secondary impacts have not been considered.

 

The global lighting industry is also innovating at a very high rate. A very large number of new lighting systems are emerging into the global market, these include very high light output LED arrays (used for street lights), new luminaires for LED’s (designed as heat sinks), new LED lights (wider colour outputs) and new discharge lamps including induction and plasma lamps. The later types of lamps have spectral outputs closely aligned to the solar spectra.

 

In the UK, the main industry body which represents the interests of manufacturers is the Lighting Trade Association (LIA), based in Telford. The LIA represent the interests of the lighting industry and also hosts an independent UKAS accredited lighting test facility. The facility is well equipped and includes a 1.8m integrating sphere (used to measure spectral output and electrical efficiency of lamps up to 1.5m in length, as well as a goniometer, used to measure the directional light output from lamps and luminaires. The goniometer can also be used to measure the light scattering patterns from diffusing cladding materials, and may be engaged in a further project on optical coatings now under consideration. Tests are calibrated against a National Physical Laboratory standard lamp. The lab also routinely conducts a wide range of lamp safety tests. The LIA test lab can be used to develop simple comparative tests of lighting systems marketed for horticultural application. Furthermore, a recent visit to the LIA demonstrated that they have access to a far wider range of lamps and manufacturers than just those focusing on the horticultural sector. The LIA also provide advisory services to manufactures (a separate section to the UKAS lab), and , in collaboration, can provide horizon scanning on lamps and lighting technology which may have future application for horticultural use.

 

The HDC are already funding a large program of work at the Stockbridge technology Centre on the use of LED’s for horticulture. This work focusses on the use of LED’s in growth rooms, but at a later stage may examine greenhouse applications. The project does not have funding to conduct large scale comparative tests of different lamp sources, or funds to engage the LIA. This project is designed to dovetail into the STC project and to provide additional support. A further complimentary proposal on plant light responses to glazing optical coatings is also under consideration by the PC panels.

 

The aims of this project are to produce a simple and up to date lighting guide for the UK horticultural sector. This will be based on up to date comparative measurements of new light sources (by the LIA), benchmarked against current knowledge of plant responses to light. We will also engage with the LIA to provide horizon scanning of likely lighting opportunities for the horticultural sector. The project will provide factual data on light performance to help growers make informed decisions, it cannot provide recommendations on which specific lamps to use in different circumstances. Recommendations of which lamp source to use for specific crops and circumstances will require thorough crop response experimentation combined with estimates of running and capital costs.

 

The target crops where supplementary lighting could be of benefit include all glasshouse grown crops, including high wire vegetables (tomatoes, peppers), soft fruit, ornamentals and herbs.

 

We will achieve our aims by;
• Conducting comparative tests at the LIA of the electrical input versus light spectral output of a wide range of lighting systems being marketed for the horticultural sector, this will include LED and plasma sources benchmarked against SON/T’s.
• Measuring the variance in light distribution from commercial luminaires.
• Engaging with the LIA to suggest new lighting systems which may have application in horticulture.
• Gaining a wider understanding of maintenance requirements, impacts on health and safety and lamp life cycles.
• Developing a lighting technology transfer event in conjunction with the STC, using an LIA consultant as a primary presenter.
• Working with the STC, and using the data developed above to provide an up to date lighting guide for the horticultural industry. This guide will then provide a framework for future reporting of the STC program, as this develops.
• The Farm Energy Centre will provide outline advice on implications for the electrical installation costs of new installations.