LED grower lighting systems

The 'LED revolution' is seeing more updated lighting products come onto the market to help growers save energy and improve efficiency, says Sally Drury.

GreenPower: interlighting system for flavourful tomatoes or cucumbers all year round no matter where production is located - image: Philips Lighting Holding
GreenPower: interlighting system for flavourful tomatoes or cucumbers all year round no matter where production is located - image: Philips Lighting Holding

LED systems have made great strides in horticulture over the past few years but who could have foretold of the rapid uptake around the world? "We are currently looking at an LED revolution," says Unigro managing director Keith Hamp.

"It is a more efficient light source than traditional lighting and emits lower levels of heat. Unlike fluorescents that lose efficiency at cooler temperatures and emit different spectral qualities depending on manufacturer, age and environment, LEDs offer a stable and long-life spectral output.

"With a large portion of green light in a fluorescent spectrum, not all of which is absorbed by the plant, LED offers a targeted, more efficient spectral output whilst maintaining the key element of the fluorescent spectrum, allowing continuation of comparable research."

In short, this means it is possible to make real energy savings using LEDs. Hamp adds: "Our LED control and lighting system is providing up to 50% energy savings relating to lighting and cooling costs whilst creating and controlling specific growing environments allowing replication of existing research."

Bespoke solutions

Unigro produces project-specific bespoke solutions tailored to meet research requirements. The company's LED control and lighting system can be retrofitted into any existing lighting environment and interfaces with all current control and management systems. Furthermore, this can often qualify for various grant schemes.

Technology is moving on fast with different colour recipes, and new products are coming to market each year specifically aimed at the horticulture market and applicable to ornamental and edible crops.

Senmatic, based in Sonderso, Denmark, has developed a new controller. The company produces two kinds of LED fixtures - the FL100 and FL300 - available in Sunlight, Grow White and Grow Fixture types. The FL100 Grow LED and FL300 Grow White top lights emit light in the photosynthetic active region of the visible spectrum and suit most modern greenhouses. Their minimalistic design should make installation easy using standard connection technology and give a minimal shadow footprint. Both can be used as replacements for conventional high-pressure sodium (HPS) systems.

The FL100 Grow, based on its FL300 big brother, has been tested by one the of the largest flower growers in Europe. Over four successive growth seasons, PKM tested it to produce more than 300,000 campanula flowers. The system was found to give a saving of 53% in electricity compared with conventional HPS and a 43% saving compared with a new 1,000W HPS system. The same plant quality was obtained as well as the same sales price as crops produced under new 1,000W HPS lamps.

When evaluating possible LED solutions it is important to check on two parameters - temperature of the LED when the fixture is running and the distribution profile on your plants. The FL300 Grow White is equipped with a patented active cooling system that enables a low LED temperature and therefore a long lifetime. Both the FL100 Grow and FL300 Grow White are designed with an optical lens system that enables a traditional installation plan similar to HPS with homogenous distribution profile at plant level.

Senmatic's latest development, a new LED controller, can be connected to any kind of climate-control system. It means that Senmatic's LEDs can now be better controlled if a grower is using a third-party climate-control system.

"We know that the blue light from 400-500nm is controlling the length of the stem but also many other things," says Senmatic manager Johnny Rasmussen. "Basil, for example, can have a stronger taste if we add blue light.

"Our fixtures can be controlled in the spectra. We can control the blue from 2% in the fixture up to 14% of blue. With 14% blue it means we have 86% of red light left in the Grow fixtures. When we add 14% blue light to a plant crop it is normally showed with a shorter internode, but also the structure on the leaf is changing to a thicker and darker leaf. With regard to herbs this is because there is more oil coming into the plants."

He adds: "We know also that when the plants have reached the stage of flowering it is important to add more red light, so in that stage it is normal to turn the amount of blue light down. But for every plant crop there is a special way to treat the plant with LED light. It's like fertiliser - for every type you need a special fertiliser.

"Our fixtures can also be dimmered up and down depending on how many specific hours of light you want in a day. This is being controlled with a light sensor outside the house, measuring the sun, and then we of course have a quantum sensor inside to measure the LED light. All this together is saving a lot of electricity and it is all controlled with the LED controller."

Optimum lighting angles

As well as colour control, design and use we have also moved forward with a positive trend towards vertical lighting and lighting between plants as well as from above. After 45 years mostly making speciality lighting, Lohuis Lighting of Naaldwijk, Holland, has now turned to LED and developed a special lamp for use in between vegetable plants such as tomatoes and cucumbers. The company has two pilot projects - at Noordhuys Tomatoes and with cucumber grower Jan Reijm in Holland.

At Jan Reijm's production site the fixtures are 1m long and emit a soft red glow that is hardly visible by day or night. "It is far-red light, which humans notice in a reduced manner," says Lohuis Lighting sales and product manager Rene Grootscholte. "We use the light as post-exposure. The other exposure mode emits a red-blue spectrum.

"A plant mostly absorbs light on a specific plant part of about 1m in length, but with horizontal fixtures in reality only one single strip is illuminated. This is not an optimal exposure for the growth potential." Based on this belief, Grootscholte developed 1m-long vertical fixtures that provide light all round.

Another point that separates these fixtures from others is that the lamps have two colour modes - one providing red-blue light, the second offering far red. "To switch on those two together does not make sense," says Grootscholte. "This was evident from testing, including from Wageningen University & Research. Just one hour of additional exposure with far red light puts the plant in generative mode.

"At Noofhuys Tomatoes we are employing a fixture that spreads light on two sides at an angle of 150 degs. At Jan Reijm, on 540sq m of cucumbers, we have a different light fixture that thanks to adjusted shape and different technique spreads the light almost 360 degs around in a diffuse manner. It is expected that the use of mMols will be more efficient. Total exposure for the cucumber testing is 95.6 mMols/sq m. This requires nine light fixtures per 5sq m. The light fittings can be raised during the growing season."

Lighting in the tomatoes has been operational since October, the cucumbers since December. The first cucumbers at Jan Reijm were harvested mid February and quality was satisfactory. It is expected that the high-wire growth will produce in excess of 300 cucumbers. "This season we monitor all aspects and this would mean a large step forward. Even with the best and most costly available LEDs we can design a fixture that after 10 years will be competitive with HPS lighting," says Grootscholte.

Next-generation products

The Horticulture LED Solutions division of Philips Lighting Holding has produced three new products over the past year. Two of them - GreenPower LED Interlighting module and GreenPower LED flowering lamp 2.0 - are described as "next-generation" products.

Philips LED interlighting system is for the production and harvest of fresh and flavourful tomatoes or cucumbers all year round, no matter where production is based. "Placing light between your plants lets you achieve maximum value and return from your production and your electricity costs for lighting," says Philips Horticulture LED Solutions marcom support Ilvy de Haas.

The interlighting system comes with an easy plug-and-play connector and just a few cables and accessories. Up to 33 interlighting modules can be connected with just one power connection, saving time, materials and installation costs. The system, which works by focusing growth-stimulating light on the most vital part of the crop, boosts production by applying the right light at the right spot with efficacy of up to 3.0umol/J. Lights come in 2m and 2.5m versions, allowing the system to be tailored to the situation for uniform light distribution right to the end of the row.

As well as using Philips GreenPower LED toplighting, both Flavourfresh Solfresh Group and APS Salads have been using the LED interlighting to produce healthy and tasty tomatoes all year round. In Lancashire, Flavourfresh grows Sweet Rosso, Piccolo, Santini and Tomkin varieties and opted for LED interlighting after visiting a grower in the Netherlands. Previously the Landsdale Nursery site used natural light to grow the crop, which meant no tomatoes were harvested between December and March.

Maximum returns

With energy costs ever increasing, it is important that the correct course of light energy is selected to provide maximum return in terms of crop yield and quality per kilowatt of energy. At the Landsdale site, Philips LED partner Agrolux and LS Systems UK installed Philips GreenPower interlighting modules in two rows (delivering 110umol/m2/s) and GreenPower toplighting modules (delivering 112umol/m2/s).

The benefit of having light and heat within the crop and light in the right spectrum from above meant that after just two days plants looked stronger, had darker leaves, more purple anthocyanin in the head and a stronger truss. Flavourfresh production manager Andy Roe says: "The total LED installation gives 100% control to use as growers. The lighting and heating work hand in hand to reduce the need for ventilation and in turn this reduces the total energy requirement by up to 35%." Flavourfresh expects to increase yield by a minimum of 30% using this technology.

On the Isle of Wight, APS Salads is a leading supplier to many UK food retailers. The company's mission has always been to grow the highest-quality delicious tomatoes all year round in the most environmentally friendly way possible. With this philosophy, APS ran trials with a hybrid HPS/LED lighting system.

"Growing in a protected environment in winter requires both heat and light. With the hybrid HPS/LED system we couldn't achieve consistent crops at an affordable cost and we were also producing too much heat via HPS lighting in the winter," recalls APS Salads group development director Phil Pearson. After a visit to the Philips GrowWise Center and witnessing the leap forward that LEDs have made over the past few years, a 100% LED system was installed with the support of Philips business partner Cambridge HOK.

Using a combination of Philips toplighting and a double row of LED interlighting, the facility now produces 220umol/m2/s. The interlighting system can be lifted and lowered to satisfy the needs of the crop and different varieties in future. "I'm seriously blown away by this technology," says Pearson. "You can almost watch the plants growing as you look at them."

For Flowers

The Philips LED flowering lamp (below) is intended as an energy-efficient way to extend daylight in greenhouses that cultivate cut flowers, bedding plants, perennials or strawberries. The first-generation flowering lamp provided a proven benchmark for energy efficiency, with trials carried out at the independent Research Centre Hoogstraten. The new and improved version provides the optimum spectrum and high light output.

As well as boosting crops, the LED flowering lamp also offers greater energy efficiency. In fact, it is said to cut energy use by up to 90% compared with incandescent lamps and offers savings over halogen and compact fluorescent lamps. Two versions are available with dedicated light recipes. One, offering a combination of deep red and white (DR/W) to inhibit the flowering of short-day plants, has proved particularly effective in chrysanthemums. The other, with a combination of deep red, white and far red (DR/W/FR), is suitable for photoperiodic lighting of bedding and perennials. It can extend the day or interrupt night cycles to promote elongation of strawberry stems and stimulate flowering.

Clearly LEDs are making a huge impact in horticulture both in the UK and around the rest of the world, yet the number of companies that are involved in developing products remains relatively small. Does that mean price will continue to command a premium? Perhaps not. Lohuis Lighting owner Anton Lohuis has the last word: "We have reached the tipping point where LEDs need not be more expensive than HPS lighting."

Light colours

- Deep red (DR) is most efficient for photosynthesis, vegetative production and stimulating shoot development.

- Blue (B) has positive effects on compactness and hardening.

- White (W) for working light/full spectrum.

- Far red (FR) has positive effects on generative properties, flower formation and rooting.

Dynamic module

A completely new product from Philips Lighting Holding is its Dynamic LED production module. It allows growers to create light recipes that can be dynamically adjusted to give the right light intensity and colour spectrum during the day or growing process. Unlimited spectral recipes can be created by tuning the four colours - deep red, blue, white and far red - in each module.

Dynamic can be used to grow an ever-changing variety of crops during the year or to investigate the effects of different light recipes or for use as a pre-harvest treatment, enhancing efficiency and flexibility.

It is ideally suited to research facilities that want to deepen their knowledge about the impact that light and light recipes have on crop growth as well as growers who want to improve and expand high-wire crops and growers whose crops require an adaptive range of light intensities.

Plessey Hyperion

Launched this year by Plessey, the Hyperion family of high-powered horticultural LED grow lights is designed to provide supplementary lighting in greenhouses.

Hyperion 1000 and 1600 units are said to deliver greater returns through increased productivity while achieving a 40% energy saving compared with equivalent 600W and 1,000W sodium grow lights.


Hortisystem UK has been selling supplementary lighting for more than 25 years and this year decided to supply the Growstack. Designed for research and growth trials, it is capable of supporting up to four growing levels simultaneously.

The LED lighting cassette uses Valoya LED technology and can be located onto the base unit at various spacings. Grow trays are inserted either alone or directly onto the light cassettes to suit plant height. As plant height increases, so the light cassette can be raised to match. Control is via a touchscreen on the top of the unit, with individual timing for each level.

Sally Drury

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