A tale of two chrysanthemums: It was the brightest of times. It was the most efficient of times.

Two different chrysanthemum growers in Holland are deploying LED toplighting in greenhouses under construction, with one opting for optimal brightness and the other prioritizing energy efficiency. Both are also using high-pressure sodium (HPS) luminaires, in a hybrid lighting deployment.

De Lier based U-Grand is installing Signify LED units in a 10-hectare facility, and Nieuwaal-based Linflowers is also going with Signify, at a 7.5-hectare greenhouse.

Both growers chose Signify’s Toplighting Force (TLF) units, which Signify introduced earlier this year as a higher-light-output alternative to its Toplighting Compact (TLC) model, which it is still offering. Toplighting Force emits up to 3600 µmol/s with an efficiency of up to 3.7 µmol/J.

U-Grand is going for all-out brightness, tapping the 3600-µmol/s edition, with the LED units delivering 128 µmol/m²/s and an equal number of HPS lights delivering 70 µmol/m²/s.

“200 µmol with LED and HPS is no longer an exception in chrysanthemum cultivation,” said U-Grand co-owner Jeffrey van Uffelen. “This allows you to achieve a higher plant density while fully maintaining quality. As a result of the light distribution and the high output of the TLF — 3,600 µmol/s — we need relatively few lights, while the light level is still very homogeneous. That is a hard requirement in chrysanthemum cultivation.”

The LED lights are rated at 1040W, the same as the HPS lights that are also going in, but the LEDs have “almost double the light output, allowing the grower to use the energy he has available in his greenhouse and increase light levels,” a Signify spokesperson explained to LEDs Magazine.

Neither Signify nor U-Grand revealed who is providing the HPS lighting, or how many lights in total they have planned for the installation, which is scheduled for next month. It is also not clear how many of both light sources Linflowers is planning.

While light output was the priority at U-Grand, Linflowers placed a premium on energy efficiency, planning 2750 µmol/s with an efficiency of 3.4 µmol/J. Their light recipe of far-red combined with red and blue abetted the efficiency choice because of the recipe’s less energy-demanding nature.

“In trials we found that with some additional far-red light, you need fewer micromoles to grow branches with the desired length and weight,” said David van Tuijl, co-owner of the 120-year-old family-run business. “This allows us to efficiently increase plant density. We also feel that the chosen spectrum gives a wider cultivation range. By that, I mean that almost all varieties respond very well to it. Without that little bit of far-red light, this module has a higher output (2850 µmol/s) and is more efficient (3.7 µmol/J), but you may run into limitations sooner.”

Like van Uffelen at U-Grand, van Tuijl said the hybrid system will deliver 200 µmol/m²/s.

Linflowers expects to open its new greenhouse this fall.

It is common these days for horticultural operations to use a mix of LED and HPS, for various reasons. Sometimes too much of the more efficient LED technology deprives a cultivar of the heat that HPS emits; sometimes HPS can emit too much heat for a particular cultivar, but often all LED can be too expensive, for example.

Signify markets the new TLF as a technology to be combined on a 1:1 basis with HPS, drawing on the same 1040W of an HPS unit but emitting more light. It is now positioning its earlier TLC model as an energy-saving HPS replacement fitting. TLC tops out at 2650 μmol/s and an efficacy up to 3.7 µmol/J to save overall energy costs.

MARK HALPER is a contributing editor for LEDs Magazine, and an energy, technology, and business journalist ([email protected]).

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