How can you improve the efficiency of your greenhouse lights?

GE Current LEDs offer controlled environment growers improved efficiency and flexibility over high pressure sodium lamps.

As light recipes for controlled environment crops are identified and refined, LED lighting manufacturers are also making improvements to their fixtures. Technological advancements in LEDs enable them to deliver the optimum light wavelengths and intensities to maximize plant growth and flowering and to increase energy efficiency.

“The Arize Element L1000 from GE Current, a Daintree Co., is a top light LED fixture,” said Bruno D’Amico, horticulture product manager at Current. “The L1000 provides the equivalent amount of light output compared to a 1,000-watt, double-ended high pressure sodium (HPS) lamp. This product was developed in response to growers’ demands for a more efficient and powerful fixture capable of replacing a 1,000-watt, double-ended HPS from a quantity of light standpoint.

“The L1000 platform is a continuation of the LED fixture Current released last year, the 200-watt L400. The L1000 offers a photosynthetic photon flux (PPF) increase of 23 percent compared to the L400, while increasing efficiency up to 3.5 micromoles per joule (µmol/J). With its flexible installation options, the L1000 is a powerful tool for growers to improve their quality and yields.”

Improved flexibility, efficiency

The L1000 can be installed in various configurations. Multiple mounting hardware options are available that allow the L1000 to be installed on existing structures regardless of the type of greenhouse. The fixture is also equipped with a separate power supply that can be remotely mounted for flexibility and ease of maintenance.

“Another advantage of remotely mounting the power supply is a reduction of its footprint over the crop, reducing shadowing,” D’Amico said.
According to D’Amico, one of the main drivers for conversion from solid state to LED lighting is the massive efficiency gains.

“HPS lamps typically offer an efficiency level of 1.8 µmol/J,” he said. “The L1000 nearly doubles this level reaching 3.5 µmol/J. The increased capital cost of investing in LED lighting is offset over the years by this gain in efficiency, as well as reduced maintenance. We also work with growers’ local utility providers on rebate packages to further sweeten the deal.”

Another important factor in the design of the L1000 was optimizing its thermal management.

“LEDs don’t like hot temperatures,” D’Amico said. “To ensure years of reliable service, it was imperative that the L1000 be able to efficiently dissipate heat. Our unique heat sink keeps the LEDs cool while reducing shadowing. In a greenhouse, the size of a light fixture must be minimized to allow for maximum natural light penetration. We set out to deliver more micromoles for less money. That is what we achieved with the L1000 platform.”

The L1000 LED is UL wet-rated and IP66. It’s made from extruded aluminum with a polycarbonate lens.

“Operating temperature tests, a key component of reliability testing, were performed in some of the worst production conditions the light could operate under,” D’Amico said. “We worked with Hort Americas to test the lights in the Texas heat, which is a tough proving ground. The light has been tested to operate with temperatures reaching 122ºF (50ºC).”

The L1000 is offered with multiple spectra options and it is also dimmable.

“The light output of the L1000 matches the light output of a HPS fixture,” said Hans Spalholz, a plant scientist at Current. “That was one of the foundations of this project: to match HPS while reducing the electrical wattage input. The light is also dimmable in order to increase or decrease the total micromole output.

“Being able to dim the L1000 gives growers versatility on how to treat their crops. By dimming or intensifying the light, growers can achieve cost savings if the natural light levels are already high by illuminating the crop at a lower light level.”

The standard life expectancy for a 1,000-watt HPS lamp is a L90 of 10,000 hours.

“With HPS, growers can expect a 10 percent degradation in terms of micromole output after 10,000 hours,” D’Amico said. “With the L1000 we are able to achieve 10 percent degradation after 36,000 hours. This is a 3½ times increase in lifespan. There is much better micromole maintenance with the L1000 compared to a HPS fixture, ensuring steady, predictable crops over the years.”

Choosing the right light spectrum strategy

Current offers a wide range of products for the specific lighting needs of growers.

“If growers want a specific light spectrum we can provide that for them,” Spalholz said. “We can also offer recommendations.

“There are two distinct scenarios: one is the greenhouse and the other is the indoor grow or vertical farm. For a greenhouse, we recommend a dichromatic or blue and red light recipe because the sun already provides natural green, orange and yellow wavelengths. In the photosynthetic active radiation (PAR) range, sunlight is composed of roughly 1/3 green light, 1/3 blue light and 1/3 red light under clear sky conditions. In indoor farms, we promote a more balanced or broad spectrum so growers can utilize the advantages of green and white wavelengths.”

Spalholz said the light recipes for some controlled-environment crops have been determined, but there can be differences between varieties.

“Especially with new varieties, there may be differences and it may take some trial and error to determine the best light recipes,” he said.

“Research has really opened up with the use of LEDs to test multiple factors, including the impact of light quality on transpiration, nutrient uptake and plant nutrient levels. From a practical aspect for optimizing production for some crops like lettuce, we’re very close. Other crops like strawberries with long life cycles where there are increased influences on the crop, the impact of light may not be readily seen until later into the crop life cycle. There is still a lot of research that has to be done on berry crops like strawberries. There can also be big differences in cultivar performance with cannabis and hemp relative to light quality.”

D’Amico said Current offers a wide variety of spectra to cater to the needs of growers.

“We work with growers to help them identify the spectrum that is best suited to their farm,” D’Amico said. “It’s not one size fits all. Having a large variety of spectra allows us to meet the growers’ unique needs. We look at our spectra as a way to an optimized grower outcome.

“We have discussions with growers and work with them to co-develop a lighting strategy. We want to be sure the growers’ operations are being run as efficiently as possible. We will always recommend a spectrum solution that maximizes efficiency to save them as much as possible over the years.”

This article is property of Hort Americas and was written by David Kuack, a freelance technical writer in Fort Worth, TX.