NL2023151B1

NL2023151B1 - Assimilation lighting with improved spectrum

Info

Publication number: NL2023151B1
Application number: NL2023151A
Authority: NL
Inventors: Mennink Twan
Original assignee: Oreon Holding B V
Priority date: 2019-05-16
Filing date: 2019-05-16
Publication date: 2020-12-01

Abstract

The invention is directed to an assimilation lighting system for growing plants, said lighting system comprising at least an deep-red solid-state light source adapted for emitting light having a peak wavelength in the range of 680 to 710 nm. In particular embodiment, the lighting system further comprises white-light sources, blue solid-state light source and/or red solid-state light sources. The assimilation lighting system can suitably be applied in enclosures for growing plants, in particular for enclosures comprising farming facility and/or vertical farming facility. Another aspect of the invention is directed to a method for growing plants with the lighting system,

Description

P122361NL00 Title: Assimilation lighting with improved spectrum The invention is directed to a method for growing plants. In addition, the invention is directed to assimilation lighting systems comprising solid-state light (abbreviated as SSL) sources to be used in such methods.

Traditional assimilation lighting systems are based on sodium or metal halide lamps to illuminate plants. In the recent period, such assimilation lighting systems have been replaced by solid-state light sources (e.g. LED-based), primarily to save the amount of energy required to provide the plants with sufficient light.

Besides the energy saving aspect, solid-state lighting system also enable optimization of the spectral distribution of the light provided to the plants. An example of such a lighting system is described in WO 2009/022016, wherein a lighting system comprising a blue light source and a red light source. Typically, a blue light source provides light of a wavelength in the range of 375 to 500 nm, while the red light sources provides light of a wavelength in the range of 600 to 750 nm. This spectral range is beneficial for plant growth as red light is very efficient for photosynthesis while blue light stimulates for instance stomata opening and induces chloroplast development. In a process called non-cyclic photophosphorylation two photosystems (PSII and PSI) are working together to transport an electron towards creating NADPH, each requiring a number of photons of 680nm (PSII) or 700nm (PSI). Furthermore PSI and PSII contain several pigments that use the mechanism of stokes shift to catch and transform a higher energy photon to a photon that the respective photosystem can use to transport the electron. These complexes of pigments are called light harvesting complexes.

Since PSI and PSII function in series, it is efficient to illuminate both systems in a balanced ratio. To provide an appropriate balanced irradiation of PSI and PSII, it has been suggested to complement the assimilation lighting with far- red light having a peak wavelength of 730 nm. Based on the Emerson-effect, it is believed that far-red light only stimulates PSI (PSII being insensitive to such light). The present inventor realized that a drawback of using such far-red light however, is that plants can poorly, if at all, absorb this light. Since the far-red light source is generally replacing another light source (e.g. a red light source), it may even be less efficient to complement the assimilation lighting with the far-red light.

It is an object of the present invention to provide an improved assimilation lighting system that can provide a balanced illumination of PSI and PSI while maintaining efficient lighting by limiting or preventing illumination with light of wavelength outside the absorbance of the plant.

Accordingly, the present invention is directed to an assimilation lighting system for growing plants, said lighting system comprising at least a deep-red solid-state light source adapted for emitting light having a peak wavelength in the range of 680 to 710 nm.

The present inventor realized that it may not be required to provide light that can only be (in part) absorbed by PSI (and not by PSII), but that it is sufficient to provide light that results in a higher absorption yield of PSI compared to the yield of PSII (herein also referred to a PSII/PSI yield ratio). It was realized that as such, the PSII/PSI yield ratio can be influenced while maintaining an overall good absorbance of the light. Accordingly, it was advantageously found that in accordance with the present invention, the deep-red light results in a higher yield of PSI than of PSII and that as such, the illumination of PSI and PSII can be balanced, without sacrificing or spilling emitted light that can not be absorbed by the plant, resulting in an overall improved efficiency (see also Laisk et al., Biochimica et Biophysica Acta 1837 (2014) 315-325). The deep-red light is thus believed to balance the desired ratio of PSII/PSI yield ratio and a good absorbance of the light by the plant. Accordingly, in a preferred embodiment, said deep-red solid-state light source is adapted for emitting light having a peak wavelength in the range of 680 to 695 nm, preferably in the range of 682 to 692 nm such as about 690 or 685 nm. At a peak wavelength of 685 nm, the PSII/PSI yield ratio is about

0.65.

The deep-red solid-state light source (herein also referred to as the deep-red light) is typically complemented in the assimilation lighting system by other light sources. These other light sources can be traditional sodium or metal hydride lamps, but this is not preferred. Preferably, the system only comprises solid-state light sources as the light source or sources. Typical solid-state light sources include semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), perovskite light-emitting diodes (PeLEDs), polymer light-emitting diodes (PLED) or a combination thereof. These types of light sources can also be used for the deep-red light source of the present system. Preferably, LEDs are used for the deep-red light source, more preferably for all light sources.

For an optimal use of the deep-red light it is preferably mixed in a particular ratio with the other light sources in the system. In a preferred embodiment, which gives good results in terms of plant growing yield, the deep-red solid-state light source is adapted to emit light of a relative intensity of up to 50%, preferably in the range of 15 to 30%, more preferably in the range of 20 to 25% such as about 22%, based on the total amount of light emitted by the lighting system.

The complemental solid-state light sources can comprise solid-state so- called “white-light” sources, blue-light sources, red-light sources or a combination thereof. Examples of solid-state “white-light” sources include single light-emitting diodes (LEDs) light sources with one or more phosphor materials that partially or fully convert the LED emission (phosphor converted LEDs). Preferably, the solid- state white-light source is adapted to emit light in the range of 375 to 680 nm, as this matches the absorption spectrum of plants. In a further preferred embodiment, the solid-state white-light source has a peak wavelength in the range of 375 to 500 nm and having a peak wavelength in the range of 550 to 650 nm.

In Figure 1, the emission spectrum of a particular embodiment of the invention is compared to a conventional white-light and red-light system, the latter having a peak wavelength of about 660 nm. By substituting the red-light source in the system with a deep-red light source having a peak wavelength of about 685 nm, an emission spectrum is obtained that is optimized to (more) selectively activate the PSI.

Alternatively, or in addition to the white-light source, the deep-red light may be complemented by blue-light sources, red-light sources or a combination thereof. Accordingly, the assimilation system may further comprise a) a blue solid-state light source adapted for emitting light having a peak wavelength in the range of 375 to 500 nm; and/or b) a red solid-state light source adapted for emitting light having a peak wavelength in the range of 600 to 680 nm.

In a preferred embodiment, said blue solid-state light source is adapted for emitting light having a peak wavelength in the range of 425 to 475 nm, preferably in the range of 440 to 460 nm such as about 450 nm; and/or said red solid-state light source is adapted for emitting light having a peak wavelength in the range of 640 to 675 nm, preferably in the range of 650 to 670 nm such as about 660 nm.

In Figure 2, the emission spectrum of a particular embodiment of the invention is compared to a conventional blue-light and red-light system. By complementing the system with a deep-red light source having a peak wavelength of about 685 nm, an emission spectrum is obtained that is optimized to (more) selectively activate the PSI thereby obtaining a better PSII/PSI balance. Notably, all emitted light has a wavelength of less than 710 nm, therewith minimizing or preventing spilling of emitted light.

The correct emission spectrum of the light sources can be set using conventional techniques, e.g. by influencing the desired band gap of solid-state light sources. For instance, blue-light LEDs can be based on GaN while the red- light and deep-red light LEDs can be based on AlGalnP.

For the embodiment wherein the lighting system comprises the blue- light, red-light and deep-red light sources, it was found that particular good results are obtained when said blue light solid-state source is adapted to emit light of a relative intensity up to 25%, said red light solid-state source is adapted to emit light of a relative intensity in the range in the range of 45 to 97%, and said deep- red solid-state light is adapted to emit light of a relative intensity of up to 50%.

In yet a further preferred embodiment, the intensity ratio of the light sources based on the total amount of light emitted by the system may be as follows: a) said blue light solid-state source is adapted to emit light of a relative intensity in the range of 3 to 15% such as about 10%; b) said red light solid-state source is adapted to emit light of a relative intensity in the range of 55 to 97% such as about 65%; and/or Cc) said deep-red solid-state light is adapted to emit light of a relative intensity in the range of 5 to 30%, preferably in the range of 20 to 25% such as about 22%, based on the total amount of light emitted by the system.

The intensity ratio of the various light sources can be set in various ways. In case the system comprises separate units comprising one or more of said various light sources, switching on or off one or more of these units can change the overall emission spectrum. In a particular embodiment of the invention however, the assimilation lighting system comprises a light unit comprising all of said light sources. This is preferred for each of installation and control of the system.

5 Moreover, it may allow for an even distribution of the emitted spectrum over the plants. The even, homogeneous emission be achieved in an embodiment wherein each of said three light sources comprises a plurality of light sources, which light sources are essentially evenly distributed over a mount of the unit onto which the sources are mounted. A homogeneous distribution is particularly preferred for illumination of the plants at close distance. At a longer distance, for instance in a greenhouse wherein the plants may be illuminated by a grid of light units, a homogeneous distribution of the light sources in each individual unit may be of less importance since each light unit is relatively small an may be considered as a point source.

Unless indicated otherwise, light intensities (including relative intensities of the various light sources) are herein expressed or based on photon flux. The intensity of the light sources can thus be expressed in umol photons per second (umol/s). By setting the amount of individual light sources in a particular unit, the intensity ratio of the light sources can be set as well as the light intensity of the unit can be influenced. Typically, a light intensity per unit in the range of 1500 to 3000 umol/s such as about 2000 pmol/s is preferred when units are mounted on the roof structure of a greenhouse. A lower intensity would require more units per surface area. For applications such as vertical farming, an light intensity of 100-200 pmol/s is preferred because the close proximity to the plants. It may be appreciated that for the application of the light units in greenhouses, the actual light intensity applied is generally lower. For instance, for growing certain lettuce species, maximum 75 umol/s/m? is typically applied such that one light unit per 27 mè suffices. Other plant species however, e.g. cannabis plants may require much higher light intensities such as about 600-700 umol/s/m?. The light unit of the present invention can provide sufficient light to illuminate all types of plants, even in the full absence of sunlight.

In a preferred embodiment, the intensity ratio of the various light sources can be controlled by a controller that is adapted to individually control the light output of each light source.

In this particular embodiment, the system thus further comprises a controller suitable for independently controlling the light output of the deep-red light source and the other light sources, for instance the white-light, blue-light and/or red-light sources if present.

The controller can function by selectively switching off or on a number of individual light sources in the unit (if the unit comprises a plurality of light sources). Alternatively, or additionally, the controller can be adapted to independently dim the light output using dimming method known in the art.

The system in accordance with the present invention preferably further comprises a means for cooling the light sources.

As is described in WO 2009/022016 (which is incorporated herein in its entirety), solid-state light sources function particularly well upon cooling (in contrast to sodium or metal hydride lamps). In a particularly preferred embodiment, the means for cooling comprise a passage such as a tube adapted for a cooling fluid flowing through the tube.

The fluid may be air or another type of gas, but is preferably a liquid such as water.

In addition to the passage, the means for cooling may also comprise other means such as one or more heat sinks.

In a particularly preferred embodiment, the unit comprising all light sources as described herein-above, comprises a mount comprising an aluminum heat sink that is in heat connection with a passage adapted for a cooling fluid flow.

In another aspect, the present invention is directed to an enclosure for growing plants comprising the assimilation lighting system according to any of the previous claims.

The enclosure may comprise a greenhouse further comprising one or more windows for admitting sunlight in the greenhouse to complement the lighting system of the invention.

Sunlight also has inter alia a wavelength in the range of 680 to 720 nm and if the intensity of the sunlight is sufficient (e.g. during daytime in summer), it may not be required to illuminate the plants in the greenhouse at full power, if at all, with the deep-red light source.

In such case, illumination of plants by the assimilation lighting system can accordingly be reduced.

At other moments, in in the absence of sufficient sunlight, for instance in during twilight, dusk, night, dawn or daytime in winter, said illumination of plants is carried out in part or fully by the assimilation lighting system.

In another embodiment, the enclosure comprises an indoor farming facility and/or vertical farming facility.

Such facilities differ from greenhouse in that, although they may comprise one or more windows as well, these windows are typically not specifically meant to provide sunlight to the plant as is the case for the greenhouse. If any windows are present at all, the windows do not provide sufficient light for plants to be farmed in the facility. For this reason, assimilation lighting is required at all time, independent of the amount of sunlight outside the facility.

Yet another aspect of the invention is directed to a method for growing plants comprising illuminating of plants by the assimilation lighting system. In a particular embodiment, the plants are illuminated by the system in the absence of sufficient sunlight, for instance in during twilight, dusk, night, dawn or daytime in winter due to the plant being grown in the indoor farming facility and/or vertical farming facility as described above.

The method may comprise reducing the amount of illumination by the system (e.g. by dimming or switching off the light sources) in case there is sufficient sunlight present (for instance during daytime in summer).

In Figure 3, a particular embodiment of a light unit (1) according to the present is illustrated. The light unit (1) is provided with a mount (2) onto which a plurality of light sources can be mounted. Figure 4 depicts a plurality of light sources (5) that can be mounted. The light unit (1) as depicted in Figure 3 further comprises a tube (3) adapted for a cooling fluid flowing through the tube and a power connector (4) to connect the unit to the electric power grid.

The plurality of light sources can be distributed over the mount a for instance illustrated in Figure 7. Of a total of 40 light sources, 26 light sources are adapted to emit light of 660 nm, 10 light sources are adapted to emit light of 685 nm and 4 light sources are adapted to emit light of 450 nm. This distribution results in an emission spectrum as shown in Figure 8.

The light units (1) can be placed in a greenhouse as illustrated in Figure

9. A plurality of light units (1), connected by cooling tubes (6) between the light units (1) are position over the crops (7). The light units are placed inside the greenhouse, below a transparent panel that is suitable to allow sunlight to enter the greenhouse.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and/or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features.

For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features deseribed.

The various aspects and embodiments of the invention may be summarised, in a non-limitative way, by means of the following numbered embodiments:

1. Assimilation lighting system for growing plants, said lighting system comprising at least a deep-red solid-state light (SSL) source adapted for emitting light having a peak wavelength in the range of 680 to 710 nm.

2. Assimilation lighting system according to embodiment 1 wherein said deep- red solid-state light source is adapted for emitting light having a peak wavelength in the range of 680 to 695 nm, preferably in the range of 682 to 690 nm such as about 685 nm.

3. Assimilation lighting system according to any of the previous embodiment, further comprising at least one further solid-state light source, for instance a white-light source, adapted for emitting light in the range of 375 to 680 nm, preferably for emitting light having a peak wavelength in the range of 375 to 500 nm and having a peak wavelength in the range of 550 to 650 nm.

4. Assimilation lighting system according to any of the previous embodiments wherein said deep-red solid-state light source is adapted to emit light of a relative intensity of up to 50%, preferably in the range of 5 to 50%, more preferably in the range of 20 to 25% such as about 22%, based on the total amount of light emitted by the lighting system.

5. Assimilation lighting system according to any of the previous embodiments, further comprising a) a blue solid-state light source adapted for emitting light having a peak wavelength in the range of 375 to 500 nm; and b) a red solid-state light source adapted for emitting light having a peak wavelength in the range of 600 to 680 nm.

6. Assimilation lighting system according to the previous embodiment wherein a) said blue solid-state light source is adapted for emitting light having a peak wavelength in the range of 425 to 475 nm, preferably in the range of 440 to 460 nm such as about 450 nm; and/or b) said red solid-state light source is adapted for emitting light having a peak wavelength in the range of 640 to 675 nm, preferably in the range of 650 to 670 nm such as about 660 nm.

7. Assimilation lighting system according to any of embodiments 5-6 wherein a) said blue light solid-state source is adapted to emit light of a relative intensity up to 25%, preferably in the range of 5 to 15% such as about 10%, based on the total amount of light emitted by the system; b) said red light solid-state source is adapted to emit light of a relative intensity in the range of 45 to 97%, preferably in the range of 55 to 75% such as about 65%, based on the total amount of light emitted by the system; and/or ¢) said second red solid-state light is adapted to emit light of a relative intensity of up to 50%, preferably in the range of 5 to 30%, more preferably in the range of 20 to 25% such as about 22%, based on the total amount of light emitted by the system.

8. Assimilation lighting system in accordance with any of the previous embodiments, wherein the light sources comprises semiconductor light- emitting diodes (LEDs), organic light-emitting diodes (OLED), polymer light- emitting diodes (PLED), Perovskite light-emitting diodes (PeLEDs) or a combination thereof.

9. Assimilation lighting system according to any of the previous embodiments comprising a means for cooling the light sources, preferably a means for cooling comprising a passage adapted for a cooling fluid flowing through a tube.

10. Assimilation lighting system according to any of embodiments 3-9 comprising a light unit comprising all of said light sources.

11. Enclosure for growing plants comprising the assimilation lighting system according to any of the previous embodiments.

12. Enclosure for growing plants according to the previous embodiment, wherein said enclosure comprises an indoor farming facility and/or vertical farming facility.

13. Method for growing plants, said method comprising illuminating of plants by an assimilation lighting system according to any of embodiments 1-10, preferably wherein said method is carried out in an enclosure according to any of embodiments 11-12.

14. Method according to the previous embodiments, wherein said illumination of plants is carried out in the absence of sufficient sunlight, for instance in during twilight, dusk, night, dawn or daytime in winter.

15. Method according to any of the embodiments 13-14, wherein illumination of plants by the assimilation lighting system is reduced in the present of sufficient sunlight, for instance during daytime in summer.

The invention can be illustrated by the following non-limiting examples. Example 1 In a experimental setup, a comparative, first batch of plants basilicum plants (Ocimum basilicum) were illuminated by a conventional lighting system (as illustrated in Figure 5) comprising a blue-light source (450 nm) of 10% photon flux and a red-light source (660nm) of 90% photon flux, based on the total photon flux of the light. The conventional lighting system emits light with a spectrum as shown in Figure 6.

Another, second batch of plants were illuminated by a lighting system according to the invention (as illustrated in Figure 7) comprising a blue-light source (450 nm) of 10% photon flux and a red-light source (660nm) of 67.5% photon flux, and a deep-red light source (685 nm) of 22.5% photon flux, based on the total photon flux of the light. The lighting system according to this experiment emits light with a spectrum as shown in Figure 8.

Both batches of plants were otherwise treated equally. After 2 weeks, the second batch of plants has shown a significantly higher growth progress.

Claims

Conclusions

An assimilation lighting system for growing plants, which system comprises at least one deep red solid-state lighting (SSL) light source adapted to emit light having a peak wavelength in the range of 680 to 710 nm.

An assimilation lighting system according to claim 1, wherein said SSL light source is adapted to emit light having a peak wavelength in the range of 680 to 695 nm, preferably in the range of 682 to 690 nm such as about 685 nm.

Assimilation lighting system according to any one of the preceding claims, further comprising at least one further SSL light source, for example a white light source, adapted to emit light in a range of 375 to 680 nm, preferably to emit light with a peak wavelength in the range of 375 to 500 nm and a peak wavelength in the range of 550 to 650 nm.

Assimilation lighting system according to any one of the preceding claims, wherein said deep red SSL light source is adapted to emit light with a relative intensity of up to 50%, preferably in the range of 5 to 50%, more preferably in the range of 20 to 25%, such as about 22%, based on the total amount of light emitted from the illumination system.

An assimilation lighting system according to any of the preceding claims, further comprising a) a blue SSL light source adapted to emit light having a peak wavelength in the range of 375 to 500 nm; and b) a red SSL light source adapted to emit light having a peak wavelength in the range of 600 to 680 nm.

An assimilation lighting system according to the preceding claims wherein a) said blue SSL light source is adapted to emit light having a peak wavelength in the range 425 to 475 nm, preferably in the range 440 to 460 nm such as about 450 nm; and / or b) said red SSL light source is adapted to emit light having a peak wavelength in the range of 640 to 675 nm, preferably in the range of 650 to 670 nm, such as about 660 nm.

An assimilation lighting system according to claim 5 or 6 wherein a) said blue SSL light source is adapted to emit light with a relative intensity of up to 25%, preferably in the range of 5 to 15% such as about 10% , based on the total amount of light emitted from the system; b) said red SSL light source is adapted to emit light having a relative intensity in the range of 45 to 97%, preferably in the range of 55 to 75% such as about 65%, based on the total amount of light emitted from the system; €) said deep red SSL light source is adapted to emit light with a relative intensity of up to 50%, preferably in the range of 5 to 30%, more preferably in the range of 20 to 25 % such as, for example, about 22%, based on the total amount of light radiated from the system.

An assimilation lighting system according to any one of the preceding claims, wherein the light sources comprise semiconductor light emitting diodes (LEDs), organic light emitting diodes (OLED), polymer light emitting diodes (pled), Perovskite light emitting diodes (Peleds) or a combination thereof.

An assimilation lighting system according to any of the preceding claims comprising means for cooling the light sources, preferably means comprising a passageway adapted for a cooling fluid flowing through a tube.

Assimilation lighting system according to any of claims 3 to 9 comprising a light unit comprising all light sources.

An enclosure for growing plants comprising the assimilation lighting system according to any one of the preceding claims.

An enclosure for growing plants according to the preceding claims, wherein said enclosure comprises an indoor horticulture facility and / or a vertical horticulture facility.

A method of growing plants, which method comprises illuminating plants with the assimilation lighting system according to any of claims 1 to 10, preferably which method is carried out in an enclosure according to claim 11 or 12.

A method according to the preceding claims, wherein said illumination of the plants is carried out in the presence of sufficient sunlight, for example during twilight, semi-darkness, night, dawn, or during the day in winter.

A method according to claim 13 or 14, wherein the exposure of the plants with the assimilation lighting system is reduced in the presence of sufficient sunlight, for example during the daytime in summer.