WO2007147242A1

WO2007147242A1 - Led luminaire

Info

Publication number: WO2007147242A1
Application number: PCT/CA2007/001096
Authority: WO
Inventors: François TREMBLAY; Charles-Benoit Germain
Original assignee: Theoreme Innovation Inc.
Priority date: 2006-06-19
Filing date: 2007-06-18
Publication date: 2007-12-27

Abstract

The led luminaire includes a heat sink and a plurality of high-power LEDs thermally linked to the heat sink. The LEDs can be of wavelengths specifically selected to match a response spectrum of a predetermined type of plant. The LEDs can be provided on removable segments. One or more strings of serially connected LEDs can be connected to respective current sources, and the current sources can be connected to a power factor corrector. In one embodiment, the current sources and the power factor corrector have heat-emitting components which are also thermally linked to the heat sink.

Description

LED LUMINAIRE

FIELD

The specification relates to a luminaire which incorporates high power LEDs (light-emitting diodes) as the light source.

BACKGROUND

Studies have shown that plants do not respond evenly to different wavelengths of light. In particular, chlorophyll α, chlorophyll β, and bacteriochlorophyll have specific response peaks at certain wavelength ranges. The wavelengths to which plants respond to are different to the wavelengths of light the human eye can detect. Different plants used in horticulture can have different response curves from one another. An example of a response curve is presented in Fig. 1 where the curves for chlorophyll α 210, chlorophyll β 220, and bacteriochlorophyll 230 are depicted.

Known luminaires for horticulture include high-pressure sodium luminaires. Such luminaires typically convert electricity into light and heat. The spectrum of light emitted by such luminaires is not adjusted to the response curves of plants, and therefore a non-negligible percentage of the light which is emitted by these luminaires is not optimized for plant production. This results in wasted energy.

There was thus a need to increase energy efficiency in horticulture lighting.

SUMMARY

Energy efficiency can be increased by providing a luminaire which uses LEDs at one or more specific wavelengths to better match a response spectrum of plants, for example.

Existing luminaires such as high-pressure sodium luminaires emit a relatively high intensity of light from a relatively small surface. Hence, several challenges were met when attempting to replace existing luminaires with LED luminaires. One of these challenges was to include a sufficient quantity of LEDs, each individually having a relatively high illumination power, on a surface of a limited area, and evacuating the heat generated by these LEDs. It was found that this can be achieved by thermally linking the LEDs to a heat sink.

By thermally linked, what is meant is that the LEDs are connected to the heat sink via one or more heat-conductive elements. Some materials are more heat-conductive than others, and such materials can be favored over other materials in the elements that thermally link the LEDs to the heat sink.

Another one of the challenges faced was to find an efficient way to power the LEDs. This can be achieved by providing the LEDs in one or more serial circuits, and by powering these circuits with current sources. To provide a sufficient amount of voltage to the current sources, a power factor corrector can be used between the current sources and an AC outlet.

Yet another one of these challenges was to evacuate the heat generated by the power supply unit in the luminaire. This can be achieved by thermally linking the heat-emitting components of the power factor corrector and current sources to the heat sink.

Henceforth, in accordance with one aspect, there is provided a luminaire comprising : a heat sink, at least one string of serially interconnected, high-power LEDs, in which each one of the LEDs is thermally linked to the heat sink for transferring heat thereto during operation of the luminaire; at least one current source, each current source being connected to at least one of the at least one string, each current source being at least partly thermally linked to the heat sink for transferring heat thereto; and a housing receiving the heat sink, the at least one string, and the at least one current source.

In accordance with another aspect, there is provided a luminaire for horticulture, the luminaire comprising : a heat sink having a heat sink surface, a plurality of serially interconnected segments being thermally connected to the heat sink surface, each segment having a plurality of serially interconnected high-intensity LEDs on an exposed surface thereof for providing photonic energy to plants. In accordance with another aspect, there is provided a luminaire for use with a predetermined type of plants, the luminaire having a selection of high-intensity LEDs of different wavelengths, the high-intensity LEDs being sufficiently proximate from one another to be substantially equivalent to a spot having an emission spectrum, the wavelength selection being made for the emission spectrum to be substantially adjusted to the predetermined response spectrum of the predetermined type of plants.

In accordance with an other aspect, the improvements provide a method of providing photonic energy to plants comprising : identifying a response spectrum of the plants; and selecting a quantity of LEDs having wavelength ranges corresponding to at least two peaks of the response spectrum to provide the photonic energy to the plants.

DESCRIPTION OF THE FIGURES

Further features and advantages of the present improvements will become apparent from the following detailed description, taken in combination with the appended figures, in which:

Fig. l is a schematic diagram showing an example of a response spectrum for a plant;

Fig. 2 is a perspective view of an example of an improved LED luminaire;

Fig. 3 is an exploded view of the luminaire of Fig. 2;

Fig. 4 is a block diagram illustrating the electrical circuit of the luminaire of Fig. 2;

Fig. 5 is an enlarged perspective view of some components of the luminaire of Fig. 2;

Fig. 6 is an enlarged perspective view of a segment of the luminaire of Fig. 2;

Fig. 7 is a schematic of an electrical circuit of the segment of Fig. 6;

Fig. 8 is an enlarged perspective view of a power factor corrector of the luminaire of Fig. 2;

Fig. 9 is a schematic of an electrical circuit of the power factor corrector of Fig. 8; Fig. 10 is an enlarged perspective view of the current sources of the luminaire of Fig. 2;

Fig. 11 is a schematic of an electrical circuit of one of the current sources of Fig. 10; and

Figs. 12A to 12G are schematic views showing different possible configurations for a heat sink of a LED luminaire.

DETAILED DESCRIPTION

Fig. 2 shows an example of an improved luminaire 10. The luminaire 10 generally includes a body 12, a shade 14, and a light source 16. The light source 16 includes a plurality of LEDs 20.

When the luminaire 10 is used in a greenhouse, as artificial lighting for a predetermined type of plant, LEDs of specific frequencies can be selected to provide an emission spectrum which is at least partly adjusted to a response curve of the predetermined type of plant. Typically, two or more selected frequencies are used. A first frequency can be of the blue color, and a second frequency can be of the red color, for example. A third frequency, such as an infrared frequency suitable to stimulate bacteriochlorophyll, can also be used. Additional frequencies can include other wavelengths in the visible light spectrum for the greenhouse owner to see better.

If the luminaire 10 is used for lighting in the visible spectrum, such as white lighting, the selection of LEDs is done accordingly.

In this example, the LEDs used are high-intensity LEDs. It will be understood that other high- power LEDs can also be used.

The shade 14 is optional, but can advantageously be used to focus the emitted light. The luminaire 10 can have various shapes as will be detailed further below. However, in the case of a square luminaire 10 as illustrated, the shade 14 can include four reflectors 14a, 14b, 14c, 14d.

Turning to Fig. 3, the body 12 includes a housing 22 which is shown removed. The LEDs 20 are thermally linked to a heat sink 24 as will be detailed below. The heat sink 24 is normally received in the housing. In this example, the heat sink 24 has an array of fins 28 which extend away from a common base 26 (see also Fig. 5), opposite the LEDs 20.

In this example, four fans 30, each driven by a DC motor (not shown), are secured to the housing 22, and are used to ventilate the fins 28, for removing heat from the heat sink 24. In this example, the upper face 29 of the housing 22 is partially open, thus defining an air inlet which allows air in. In use, the air is blown by the fans 30 towards the heat sink 24, and escapes through apertures 32 which are defined in the housing 22 at a position adapted to correspond with the longitudinal ends of the fins 28. In operation, air is drawn by the fans through the upper face 29, and against the heat sink 24, and is evacuated along the grooves defined between the fins 28 and out the longitudinal ends thereof, through the apertures 32 in the housing 22. It will be understood that other suitable types of heat sinks and cooling systems may be used as well. For example, a single AC-motor driven fan can alternately be used.

The heat sink 24 allows evacuating the heat generated by relatively high concentration of LEDs 20 on the heat sink 24. The proximity, or high concentration, of the LEDs 20 results in the LED luminaire 10 approaching the effect of a single light source having a substantially evenly distributed emission spectrum. The emission spectrum can be adapted by selecting a different number of LEDs 20 having different wavelengths. For example, roughly one third of the LEDs 20 can be of red color, one other third of the blue color, and the remaining third being of an infrared and/or white color.

With the desire to optimize the efficiency of the luminaire 10, it is advantageous that the LEDs 20 be grouped in strings of serially interconnected LEDs 20, and to have a relatively high number of LEDs 20 so connected in each string. Each string can be supplied with a satisfactory amount of current using a respective current source 114, and a power factor corrector 112 can be used to convert power from an AC source to DC of a satisfactory voltage to supply the current sources 114.

In this example, the current sources 114 are provided on one transversal side 25 of the heat sink 24, whereas the power factor corrector 112 is provided on the other transversal side 27 of the heat sink 24. A block diagram illustrating an example of such a configuration of a power supply 111 is presented in Fig. 4. The power factor corrector 112 receives power from an AC power source 110. The AC power source 110 can be of between 85 V and 265 V and between 47 Hz and 63 Hz, for example. The power factor corrector 112 both converts the AC to DC and boosts the voltage. The output of the power factor corrector is 400V DC in this example. One or more current sources 114a, 114b, 114c, 114n are connected to the power factor corrector 112. A LED string 116a, 116b, 116c, 116n is connected to a respective one of each current source 114a, 114b, 114c, 114n. The LED strings 116a, 116b, 116c, 116n can have LEDs 20 of the same, or of different colors. Having LED strings 116a, 116b, 116c, 116n with LEDs of the same color can be advantageous because it can allow adjusting the relative intensity of the different colors of two or more strings by adjusting the respective current source. When used in a greenhouse, for example, one or more of the current sources can be connected to a photodetection system to automatically adjust the intensity of the respective LEDs with variations in the natural sunlight.

One drawback which can occur when connecting LEDs in series is that when LEDs die out, they may create an open circuit, in which case current cannot pass, and the entire string can stop illuminating. This difficulty can be dealt with by using a bypass system with the LEDs strings

116a, 116b, 116c, 116n. For example, groups of one or more LEDs in a string can have a protector connected in parallel. The protector normally acts as an open circuit, but switches to a closed circuit when current stops passing due to a burnt LED. Sidacs and/or zener diodes can be used as protectors, for example.

In this example, an electromagnetic interference (EMI) filter 113 is connected between the AC source 110 and the power factor corrector 112. An auxiliary power supply 118 is also connected to the AC source 110 via the EMI filter 113. The auxiliary power supply is a 12 V DC power source and is used to power the fans 120 and to provide suitable power to some components of the current sources 114a, 114b, 114c, 114n. Alternately, if the LED strings 116a, 116b, 116c, 116n have compatible specifications, all the LED strings 116a, 116b, 116c, 116n can be energized using a single current source. One way to embody the LED strings 116a, 116b, 116c in the luminaire 10 is shown in Fig. 5. LEDs 20 can be provided in rows 34 of serially connected LEDs. Furthermore, two or more adjacent or non-adjacent rows can be serially interconnected to form a section 36, having all the LEDs of one string 116a. Hence, the LEDs 20 of the luminaire 10 can be separated into two or more sections independent from one another, which can correspond to two or more strings 116a, 116b, 116c, 116n. LEDs 20 of different wavelengths can be grouped into respective sections. Alternately, LEDs 20 of different wavelengths can be mixed in a single section.

If respective wavelengths of LEDs are separated into respective sections, the intensity of the different wavelengths can be adjusted independently by varying the electrical current in that respective section while maintaining the electrical current constant in the other sections.

Although LEDs have a high durability when compared to other types of lights, it remains that statistically, a given percentage of LEDs will typically die out before their projected lifespan. When they malfunction, LEDs can either create an open circuit or a closed circuit. If a number of LEDs die out into a closed circuit, the illuminating power of the luminaire 10 decreases, and the emission spectrum thereof may vary. It may therefore be desired to change the specific LEDs which have died out. It is therefore desirable that the LEDs 20 can be removably mounted to the heat sink 24 while being thermally linked to the heat sink 24 to dissipate heat generated by the LEDs.

One way to achieve this is to use LEDs 20 which are mounted to removable segments 38. In the illustrated example, the segments 38 were chosen to be metal core PCB (MCPCB) boards 38a due to the enhanced heat transfer characteristics of MCPCBs relatively to the more common PCBs. However, it will be understood that other types of heat-transmitting segments can alternately by used.

In the example, the LEDs 20 are soldered to the MCPCB 38a, to enhance heat transfer between the LED and the MCPCB 38a. The segments are removably held in place on a flat segment- receiving surface 39 of the heat sink 24 by means of fasteners 40. Electrically insulating bushings 40a can be used to prevent the conduction of electricity from the MCPCB 38a to the fasteners 40.

A thermal grease can be used between the MCPCB 38a and the segment-receiving surface 39 of the heat sink 24,to enhance heat transfer between the MCPCBs 38a and the heat sink 24. However, in some applications, the simple abutment of the MCPCB 38a against the heat sink 24 may suffice to maintain an effective thermal link therebetween.

The heat sink 24 can include a central temperature sensor (not shown), powered by the auxiliary power supply 118 (Fig. 4), and which is adapted to provoke an automatic shutdown of the current sources 114a, 114b, 114c, 114n if the temperature of the heat sink 24 exceeds a predetermined safety limit. Alternately, the luminaire can have a fan failure detection module, powered by the auxiliary power supply 118 (Fig. 4), which can be adapted to cut the power supply to the current sources 114a, 114b, 114c, 114n upon detection of the failure of one of the fans.

If there are more than one segment 38 per row 34, the segments 38 of the row 34 can be interconnected to maintain the serial connection of the LED section 36. hi the example, each row has two segments 37a, 37b. Rows having only one, or more than two segments can alternately be used.

In this example, a connecting circuit 41 is provided on the heat sink 24. The connecting circuit 41 receives power from the current sources 114. The connecting circuit 41 includes a plurality of connectors 43 which are adapted to connect with mating connectors 47a or 47b provided on the removable segments 37a, 37b. The connecting circuit can include the necessary circuit paths to connect two or more rows 34 of LEDs 20 in series, into a LED section 36.

It will be noted that the connecting circuit connectors 43 are provided on a single side 27 of the heat sink 24. The segments 37a include a first connector 47a at one end, and a second connector 49a at the other end. The segments 38 include interconnecting segments 37a and end segments 37b. The interconnecting segments 37a are connected to the connecting circuit 41 with the first connectors 47a, and have the second connector 49a connected to the first connectors 47b of the end segment 37b. Both segments 37a, 37b form a loop of serially interconnected LEDs, the loop being connected to the connecting circuit by the first connector 47 a.

Fig. 6 shows a segment 38 in greater detail. The segment 38 includes a first connector 47 to connect the segment 38 to the connecting circuit 41 of the luminaire 10 (Fig. 5). The segment 38 also includes a leading branch 42, having several serially interconnected LEDs 20, and a return branch 45, also having several serially interconnected LEDs 20. The segment 38 also has a secondary connector 49 between the leading branch 42 and the return branch 45. In operation, current travels from the connecting circuit 41 through the first connector 47, along the leading branch 42, optionally through an adjacent segment via the second connector 49, and back along the return branch 45 and to the connecting circuit 41 through the first connector 47.

For simplicity of manufacturing, similar segments 38 can be used as both the interconnecting segments 37a and the end segment 37b (Fig. 5), with the difference that in the end segment 37b, the second connection 49b is closed. In such a case, it is possible to use only an end segment 37b in a row 34 by connecting it directly to the connecting circuit 41.

Two way segments are advantageous because they allow using either one or two segments in each row. However, it will be understood that in alternate embodiments, the segments can be only one way, and the connecting circuit can have connectors on both sides 27, 25 of the heat sink receiving surface 39 (Fig. 5). The adjacent segments of a such a row complete the circuit between the opposite connectors.

A different number of LEDs can be used per segment. Having a small number of LEDs per segment has the advantage that less functioning LEDs are wasted when changing a segment having a prematurely expired LED. However, having a larger number of LEDs per segment makes it somewhat faster to change all the segments of the luminaire when the LEDs have reached their standard life expectancy.

A schematic of the circuitry of the segment 38 is shown in Fig. 7. An expired LED 20 can provoke an open circuit. This would result in the entire serial connection of a LED string to be broken. To avoid this, a bypass system is used. In this example, the bypass system includes one protector 50, 52 for each of the two branches 42, 45 of the segment 38. Each of the protectors 50, 52 is connected in parallel with the series of LEDs 20 of the respective branch 42, 45. If a LED 20 dies out into an open circuit, the respective protector 50, 52 acts to maintain the serial connection. Protectors 50, 52 can alternately be used with each LED, or with groups of two or more LEDs. Having more protectors per LED is typically more expensive, but allows less LEDs to be affected when one LED prematurely dies out in an open circuit. The protectors 50, 52 normally offer a relatively high resistance, approximately an open circuit, but switches mode to allow current to pass when one LED dies out in an open circuit, bypassing the series of LEDs to which it is connected in parallel.

The particular type of protector 50, 52 used can vary depending on the particular applications. In the example, a sidac is used. Alternately, a zener diode can be used, for example.

The power factor corrector 112 and the current sources 114A, 114B, 114C typically include heat-emitting components, such as transistors for example, which generate heat during normal operation of the luminaire. In order to appropriately remove the generated heat, the heat- emitting components included in the power supply can be thermally linked to the heat sink 24 to transfer heat thereto.

Fig. 8 shows the power factor corrector 112. The power factor corrector 112 is mounted to a thermally conductive L-shaped bracket itself fastened against the outer surface of the last fin 56.

In the example, the power factor corrector 112 has four heat-emitting components : a diode 58, two MOSFETs 60, 62, and a diode bridge 64. Each one of these heat-emitting components is mounted to the flange 66 of the L-shaped bracket 54, and is thus thermally linked to the heat sink 24. During operation, the heat-emitting components 58, 60, 62, 64 emit heat which is conducted to the L-shaped bracket 54. The heat of the L-shaped bracket is conducted to the heat sink 24, where it is evacuated by convection using the fans 30 (Fig. 3).

Fig. 9 shows a schematic of the circuit of the power factor corrector 112 used in this example. The heat-emitting components 58, 60, 62, 64 are identified in the circuit.

Fig. 10 shows the three current sources 114a, 114b, 114c used in this example. The current sources 114a, 114b, 114c are mounted to a thermally conductive L-shaped bracket 68 itself fastened against the outer surface of a last fin 70. hi the example, each current source 114a, 114b, 114c has a respective MOSFET 72a, 72b, 72c. The heat-emitting MOSFETs 72a, 72b, 72c of the current sources 114a, 114b, 114c are mounted to the flange 74 of the L-shaped bracket 68, and are thus thermally linked to the heat sink 24.

Fig. 11 shows a schematic of the circuit of one current source 114a used in this example. The heat-emitting MOSFETs 72a is identified in the circuit. The other current sources 114b, 114c are based on the same circuit configuration.

Turning to Figs. 12A to 12G, various alternate configurations of heat sinks are shown. A flat heat sink such as the one illustrated in Fig. 1 is shown in Fig. 12 A. It is to be noted that this configuration of heat sink can be made of various rectangular shapes. For example, it can be made into an elongated rectangle with the LED segments on its lower face, opposite the fin tips, in order to be provided under a beam of a greenhouse. This configuration would reduce the amount of shade from sunlight associated to the luminaire by placing the luminaire in the existing shade from the beam. Figs 12B, 12C, 12D, and 12E illustrate different polygonal configurations. In these examples, the LEDs can be placed around the heat sink to illuminate the plants horizontally, for example. In Fig. 12D, the fins have no end, and cross the entire heat sink structure. Fig. 12F shows a configuration in which two planes of LEDs at slightly different angles can be used. Fig. 12G shows a cylindrical configuration.

Fig. 1 showed exemplary response curves. Chlorophyll α 210 can be seen to have response peaks at about 420 and 650 nm. Chlorophyll β 220 can be seen to have response peaks at about 450 and 630 nm. Bacteriochlorophyll 230 can be seen to have a peak in the infrared and in the UV. Using the LED luminaire, LEDs having wavelengths selected to be adjusted to such a response spectrum can be used to provide photonic energy to the plants. Various wavelengths can be selected for various plants. For example, blue wavelengths between 425 and 470 nm can be used, red wavelengths between 660 and 690 nm can be used, infrared wavelengths between 700 and 780 nm can be used, UV wavelengths of 280 and 425 can be used, and in some R&D applications, wavelengths between 550 and 600 nm can also be used. Still other wavelengths can be used for specific plants. Wavelengths below 350 nm or above 800 nm can be useful in certain applications.

In one example, dominant wavelengths of 455 nm and 690 nm are used. In another example, dominant wavelengths of 455 nm, 660 nm and 730 nm are used. Alternately, a UV wavelength range having a dominant wavelength of about 375 nm can be used instead of or in combination with the infrared wavelength.

Instead of being used with specific wavelengths for horticulture, the LED luminaire can be used to provide white lighting in an industrial or commercial setting, for example, by an appropriate selection of LEDs.

In the example, aluminium is used for the heat sink and the L-shaped brackets. In other embodiments, other heat-conductive materials can be used as well.

As can be seen therefore, the examples described above and illustrated are intended to be exemplary only. The scope of the patent is intended to be determined solely by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A luminaire comprising : a heat sink, at least one string of serially interconnected, high- power LEDs, in which each one of the LEDs is thermally linked to the heat sink for transferring heat thereto during operation of the luminaire; at least one current source, each current source being connected to at least one of the at least one string, each current source being at least partly thermally linked to the heat sink for transferring heat thereto; and a housing receiving the heat sink, the at least one string, and the at least one current source.

2. The luminaire of claim 1 further comprising a power factor corrector also received by the housing, the power factor corrector having an AC inlet and a DC outlet, and being at least partly thermally linked to the heat sink for transferring heat thereto, wherein each current source has a DC inlet connected to the DC outlet of the power factor corrector.

3. The luminaire of claim 1 wherein the at least one string also has a bypass system to maintain functionality of the string upon failure of one or more of its LEDs.

4. The luminaire of claim 1 wherein the at least one string of LEDs is provided on two or more interconnected segments, the segments being removably fastened to a receiving surface of the heat sink.

5. The luminaire of claim 4 wherein the segments include MCPCBs.

6. The luminaire of claim 1 wherein the heat sink has a flat receiving surface, and a plurality of fins extending normally away from the flat receiving surface, including two opposite edge fins, and wherein the at least one string is received on the flat receiving surface.

7. The luminaire of claim 6 wherein the power factor corrector is mounted to one of the two opposite edge fins, and the at least one current source is mounted to another one of the two opposite edge fins.

8. The luminaire of claim 7 wherein the power factor corrector and the at least one current source are received on respective L-shaped brackets made of thermally conductive material and having a portion thereof in contact with the respective edge fins, wherein the power factor corrector and the at least one current source are at least partly thermally linked to the heat sink by having at least one heat-emitting component thereof mounted to a flange of the L-shaped brackets.

9. The luminaire of claim 1 having at least two strings, wherein each string has LEDs of the same wavelength.

10. The luminaire of claim 9 having at least two independently adjustable current sources.

11. The luminaire of claim 1 further comprising at least one fan received in the housing and associated with the heat sink, the at least one fan being operable to evacuate heat from the heat sink.

12. A luminaire for horticulture, the luminaire comprising : a heat sink having a heat sink surface, a plurality of serially interconnected segments being thermally connected to the heat sink surface, each segment having a plurality of serially interconnected high-intensity LEDs on an exposed surface thereof for providing photonic energy to plants.

13. The luminaire of claim 12 further comprising a power factor corrector having an AC inlet and a DC outlet, and being at least partly thermally linked to the heat sink for transferring heat theret, and a current source connected to the plurality of serially interconnected segments, having a DC inlet connected to the DC outlet of the power factor corrector, and being at least partly thermally linked to the heat sink for transferring heat thereto.

14. The luminaire of claim 12 wherein the plurality of serially interconnected segments has a bypass system to maintain functionality of the string upon failure of one or more of its LEDs.

15. The luminaire of claim 12 wherein the heat sink has a flat receiving surface, and a plurality of fins extending normally away from the flat main surface, including two opposite edge fins, and wherein the segments are received on the flat receiving surface.

16. The luminaire of claim 15 wherein the segments include MCPCBs.

17. The luminaire of claim 15 further comprising a power factor corrector is mounted to one of the two opposite edge fins, and at least one current source connected between the power factor corrector and the plurality of segments, and mounted to another one of the two opposite edge fins.

18. The luminaire of claim 17 wherein the power factor corrector and the at least one current source are received on respective L-shaped brackets made of thermally conductive material and having a portion thereof in contact with the respective edge fins, wherein the power factor corrector and the at least one current source are at least partly thermally linked to the heat sink by having at least one heat-emitting component thereof mounted to a flange of the L-shaped brackets.

19. The luminaire of claim 15 further comprising at least one fan received associated with the heat sink, the at least one fan being operable to evacuate heat from the heat sink.

20. A luminaire for use with a predetermined type of plants, the luminaire having a selection of high-intensity LEDs of different wavelengths, the high-intensity LEDs being sufficiently proximate from one another to be substantially equivalent to a spot having an emission spectrum, the wavelength selection being made for the emission spectrum to be substantially adjusted to the predetermined response spectrum of the predetermined type of plants.

21. The luminaire of claim 20 wherein the LEDs are provided on a heat sink having a plurality of fins extending in a direction opposite the LEDs, further comprising at least one fan associated with the fins for evacuating heat therefrom.

20. A method of providing photonic energy to plants comprising : identifying a response spectrum of the plants; and selecting a quantity of LEDs having wavelength ranges corresponding to at least two peaks of the response spectrum to provide the photonic energy to the plants.