NL1042087B1

NL1042087B1 - Illumination system for greenhouses with remote monitoring

Info

Publication number: NL1042087B1
Application number: NL1042087A
Authority: NL
Inventors: Petrus Van Vliet Wilhelmus; Jacobus Smits Johannes
Original assignee: Nges Holding B V
Priority date: 2016-09-30
Filing date: 2016-09-30
Publication date: 2018-04-10
Also published as: WO2018062989A2; EP3536128A2; WO2018062989A3

Abstract

An illumination system (20) for greenhouses comprises: a plurality of lamp units (1 01) comprising at least one LED load (12) and a driver (17); a central monitoring device (200) adapted for remotely monitoring at least one operational parameter of the lamp units and for generating an alerting signal (Sa) for service personnel when it detects that the monitored parameter is outside a predetermined range. A lamp unit may be provided with at least one sensor (22) for sensing the at least one operational parameter, and with communication means for communicating information to the central monitoring device. If a group of lamp units is supplied by a common mains supply line (201 ), the system may include a current sensor (203) arranged in or at the common supply line, for communicating to the central monitoring device a current sense signal (Se) indicating the actual current flowing in the common supply line.

Description

FIELD OF THE INVENTION

The present invention relates in general to the field of plant growth, specifically but not exclusively the field of large-scale commercially growing plants for production. The invention contributes to enhance the illumination conditions in greenhouses in a controlled manner.

BACKGROUND OF THE INVENTION

In greenhouses, crop like tomatoes, cucumber, pepper, or more in general plants, are cultivated for an optimal yield. It is a general desire that crop grows as fast as possible in order to be able to harvest as early as possible and to obtain a commercial value as high as possible. Crop growth and the enhancement of crop growth is dependent on many factors. Apart from nutrients, the most important growth factors are water, air (with a substantial percentage of carbon dioxide), temperature, and light, and a commercial plant grower will try to control these factors to some optimum values. Crop growth is basically dependent on the photosynthesis of the plant. Photosynthesis is basically the conversion of carbon dioxide into sugar and oxygen stimulated by photons (light). This process can be optimized (or hindered) by the adjustment of specific environmental parameters. Important factors in this respect are light spectrum and light intensity at the location of the leaves.

SUMMARY OF THE INVENTION

In modern greenhouses, artificial illumination as part of creating an optimal set of conditions for the stimulation of crop or ornamental plant growth is quite common. Especially when sun light is fading and/or periods of daylight are getting shorter, like in autumn and winter season, artificial illumination of plants is essential for obtaining good growth. Such artificial illumination is also indicated as assimilation lighting.

Light sources can be considered as sources of energy. This energy is emitted by means of photons with different wavelengths (blue to red, respectively 400 - 700 nanometres), which are used by plants for photosynthesis. However, not every wavelength is efficient for crop growth. The photosynthesis creates nutrients required for growth.

The type of artificial illumination depends on the application, e.g. stimulation of crop growth, ripening of crop fruits, root stimulation etc, or simply type of crop.

Mostly, high or low pressure gas discharge lamps (sodium lamps) are used for assimilation lighting. However, these lamps have a limited lifespan of typical 6 months to one year and therefore need regular replacement. Further, these lamps consume a lot of energy, typically 600 W to 1000 W for approximately 10 square meters of crop. Unfortunately, the energy to light conversion rate is quite low: about 30 percent of the energy input is converted into usable light (photons), and the remaining energy is converted into heat and usually lost in the ridge of the greenhouse where it is of no use for crop. The excess heat must be discharged by ventilating the greenhouse in order to keep temperature at a optimal level.

This waste of energy (heat and energy consumption) is not acceptable anymore for economic, environmental and sustainability reasons. Also the limited lifetime of gas discharge lamps puts an economic pressure on business, mainly, but not only, because of labour costs for replacement.

In order to avoid these disadvantages, a system for stimulating plant growth has been developed that comprises light sources based on a different technology,

i.e. LEDs. Light Emitting Diodes (LEDs) have all kinds of advantages, including compact size, high efficiency, and long life expectancy. In principle, an LED generates light within a narrow spectral range only but, in contrast to the sodium lamp whose narrow spectral range is fixed, it is possible to design an LED such that it generates its light output in a desired spectral range. Of course, it is possible to combine LEDs of different types, each generating light in mutually different spectral ranges, to obtain an overall light output having a certain desired spectral distribution.

The present invention aims to further elaborate on the LED technology to optimize an illumination system for stimulating plant growth.

It is very important to assure a reliable illumination for the plants, which implies that defective or failing lamps should be repaired as soon as possible. In this respect, it is a problem that in a normal greenhouse setup each assimilation lamp illuminates approximately 10 square meters of crop. The crop illumination density is dependent on the type of crop, and the output power of the lamp, but often each illuminated hectare (100 x 100 meters) is covered with a grid of 1000 assimilation lamps. Traditionally, defective lamps are found via visual inspection of all lamp units, but with such large numbers of lamp units such visual inspection is very timeconsuming. On the other hand, without real inspection, one can not rely on a defective lamp being noted by personnel from a distance, because a defective lamp is easily over-radiated by its neighbours, so it may take some time before the defective lamp is found by coincidence. On the other hand, the plants serviced by the failing lamp suffer from insufficient illumination and quickly run behind in their development.

It is therefore desirable to be able to spot a failing lamp unit quickly and automatically, ideally even before it actually fails.

The present invention overcomes the above problems and drawbacks by providing a system that enables remote monitoring of the lamp units, and that is capable of early signalling a defective or failing lamp unit.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of the present invention will be further explained by the following description of one or more preferred embodiments with reference to the drawings, in which same reference numerals indicate same or similar parts, and in which:

figure 1 schematically shows a longitudinal cross section of an exemplary embodiment of an assimilation lamp device according to the present invention; figure 2 schematically shows a block diagram of an LED lamp unit; figure 3 is a diagram schematically showing an illumination system for greenhouses in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 schematically shows an exemplary embodiment of a compact and relatively low cost assimilation lamp device 101 useful for application in the present invention. The lamp device 101 comprises a central lamp unit 10 which includes a body 14 of a general rectangular block shape. The lamp device 101 further comprises a plurality of LEDs 12 mounted to an under surface of the body 14, preferably in a recessed portion 11 thereof. The body 14 has a cabinet 15 accomodating driving and control circuitry 17 for the LEDs. The cabinet 15 will receive an electric supply cable for electrical supply, but this is not shown for sake of simplicity. The driving and control circuitry 17 generates driving current for the LEDs 12, which current is transported to the LEDs via conductors extending through the body 14, but this too is not shown for sake of simplicity.

The LEDs may be selected to emit light in (different) parts of the 300 - 700 nm spectrum. A 300W lamp version emits approximately 200 pmol/s, compared to a 600W gas discharge sodium lamp which emits approximately 140 pmol/s. In this respect, a mol indicates a number of photons, 1 mol being Avogadro's number, i.e. 6.02 x 10²³.

The LEDs 12 are mounted to have a good thermal conduction towards the body 14. The body 14 is made of a thermally well conducting material, for instance aluminum. Thus, the body 14 acts as a heat sink for the heat generated by the LEDs.

This in any case has the effect that the temperature of the LED’s remains at such a level that the lifetime of the LED’s is not affected.

The lamp device 101 comprises a fan 42 or any other type of air stream generating means for generating a downward air stream 43, as well as heat transfer and exchange means 20 for transferring heat from the body 14 to the air stream 43, so that the air stream cools the body 14 and the heat from the LEDs 12 is used to warm said downward air stream 43. This warm air stream 43 ultimately reaches the plants, so that all in all the heat generated by the LEDs is not a loss any more but is advantageously used to warm the environment of the plants.

The precise structure of the heat transfer and exchange means 20 is not essential for understanding the present invention, and therefore this structure will not be discussed in detail here.

In this embodiment of the assimilation lamp 101, the fan 42 is arranged above the heat exchanger structure 20 to generate a vertical air flow towards the heat exchanger structure 20; the air flow is blocked by the body 14 and is deflected in a horizontal direction. The precise horizontal direction is determined by the design of the heat exchanger structure 20.

The heat exchanger structure 20 in this embodiment comprises a plurality of relatively thin cooling fins or lamellae 41 that in between them define flowing paths for the air. Tthe fins or lamellae 41 are all mutually parallel and extend in XZ-planes, with the X-direction parallel to the longitudinal direction of the assimilation lamp 101. To assure the downwards air stream 43, this embodiment of the assimilation lamp 101 comprises a guiding hood 160 having a substantially inverse-U shaped profile with a top wall 161 and substantially vertical side walls 162. At its underside, the hood 160 is open. The top wall 161 has a raised portion 163 having a central opening 164, provided with a protective grating 165. Under the opening 164, surrounded and protected by the raised wall portion 163, the fan 42 is arranged. The top wall 161 lies in close proximity to the upper side of the fins or lamellae 41, so that in operation air is sucked in via the opening 164 and is forced to pass between the body 14 and the top wall 161 of the hood 160, following in X-direction the flow channels between the fins or lamellae 41. In this X-direction, the hood 160 is wider than the body 14, so that a collective flow path is defined between the side walls 162 and the body 14 where the air can do nothing else but flow down in vertical direction, to exit the device at the underside of the hood 160, which may be flush with or lower than the lower surface of body 14. It is noted that, in X-direction, the fins or lamellae 41 may have the same size as the body 14, as shown, but it is also possible that these fins or lamellae may extend as far as to meet the hood side walls 162.

It is to be noted that assimilation lamp devices of a different design may be used in the system of the present invention. It is further noted that, depending on climate conditions such as time of day and date of year, the illumination by the LEDs 12 is not needed and is therefore switched off, so that the air flow 43 is not heated. It is even possible that controllable downflow generators are used that comprise one or more fans but that do not include any LED or other heating means for the airflow.

Figure 2 schematically shows a block circuit diagram of an exemplary LED lamp unit 101, that comprises an electronic driver 17 and an LED load 12. The driver 17 comprises an input 3 for connection to mains to receive alternating voltage, and an output 9 for providing output current to the LED load 12. By way of illustrative example, the driver 17 may comprise a rectifier and filter section 5, and a converter section 6. As will be known to persons skilled in the art of electronic drivers, the converter section 6 comprises a control device 7, typically implemented as a suitably programmed micro-controller or the like, that controls on or more switches 8 in the converter section 6.

Since driver designs are known per se, and prior art driver designs can be used in the present invention, a further more detailed explanation will be omitted here.

The LED load 12 may consist of one single LED, but will more generally comprise a plurality of LEDs arranged in series (string) and/or in parallel. Since the precise design of the LED load 12 is not relevant to implementing the present invention, while prior art LED loads can be used in the present invention, a further explanation will be omitted here. It is noted, however, that the LEDs in the LED load may have mutually identical characteristics or may have different characteristics to provide for an overall light output having a desired overall spectral content.

It is also possible that a single driver supplies two or more LED loads.

LEDs have a quite long life expectancy, as long as they are operated in accordance with specifications. Undetected or late detection of failed lamp units in a greenhouse can cause severe damage to crop and consequently loss of profit. If crop is not illuminated in winter time, deterioration of crop sets in fast and will cause a lag in growth or a complete loss of crop yield. Although it seems to be easy to detect whether a light is on or off, in an array of hundreds of lamps and a blurred view due to high crop, it is in practice difficult to detect defect lamp units.

An important cause of LED failure is insufficient cooling: the temperature of the LED becomes too high. Typically, therefore, LED lamp units are provided with sensors to sense operational parameters, such as for instance one or more temperature sensors 22 generating a temperature sense signal for the control device

7. If there is for instance a malfunction of the cooling system, for instance because the ventilator 42 breaks down or gets stuck, the temperature of the cooling body 14 rises quickly. This will be detected by the sensors 22 and hence by the control device 7, who in response will switch off the driver 17 to prevent further temperature rise. Other sensors may for instance detect the electrical behaviour of the LEDs 12, and if their behaviour is outside an expected range, the control device 7 may switch off the driver 17 to prevent damage. And of course, if the LEDs fail in the form of an open circuit or a short circuit, voltage and/or current sensors will detect this and the control device 7 may switch off the driver 17.

In a possible embodiment, the control device 7 of the lamp unit 101 may be provided with communication means 23 for communicating the sensed values and/or the failure condition to a central monitoring device 200. Information defining the expected range may be stored in a single memory associated with the central monitoring device 200, or in individual memories associated with the lamp units. In response, the central monitoring device 200 may generate an alerting signal Sa for service personnel, for instance in the form of a text message to their mobile phone, so that the failing lamp may be serviced as quickly as possible. It is now not necessary any more to rely on time-consuming visual inspection.

The communication from the control device 7 of the lamp unit 101 to the central monitoring device 200 may take place via wired or wireless link. A wired link may include a separate network of communication wires, or a communication bus. A wired link may include a supply line. A wireless link may include a wireless communication network, for instance Bluetooth, Zigbee, WiFi.

The lamp unit 101 may be provided with a unique ID code, and the control device 7 may communicate this ID code to the central monitoring device 200. The lamp unit 101 may be provided with a GPS receiver, and the control device 7 may communicate its exact location to the central monitoring device 200. In the alerting signal, the central monitoring device 200 may include a description identifying the failing lamp unit and/or or its location, to further assist the personnel in quickly finding the failing lamp unit.

Figure 3 illustrates another possible embodiment, that has among other things an advantage that it can be used with lamp units that do not have the sensing and communication abilities discussed above.

It should be clear to persons skilled in the art of electrical supply that a main supply line from the mains grid will enter the greenhouse premises and will then first enter a fuse box with a plurality of fuses. Each fuse will service a portion of the electrical circuitry at the premises, with a group of apparatuses, in this case lamp units. The number of lamp units within one group has a maximum, that depends on the rating of the fuse and on the power rating of the lamp units. Assume a power voltage of 400 VAC and a fuse of 25A. This means that a group may contain a maximum of 10 kW consumers. Assume lamp units of 1.3 kW per unit: in such case it is possible to connect 7 lamp units in one group.

Based on this example, figure 3 shows a group of 7 lamp units 101 connected to a mains supply line 201. A fuse is schematically indicated at 202. Between the fuse 202 and the lamp units 101, or in any case in a portion of the supply lines that is exclusively common to this group of lamps, a current sensor 203 is arranged. This sensor 203 gives a current sense signal Sc to the central monitoring device 200. Advantageously, the current sensor 203 is mounted close to or even within the fuse box (not shown). It is noted that a sensor does not need to interrupt the sensed line.

The current in the supply line, and hence the current sense signal Sc, is a good indicator of the operation of the lamp units. In steady state, each lamp unit in the above example should consume about 3.25 A. Deviations in current consumption may indicate abnormal lamp behaviour. Especially if a lamp unit is shut down by its control device 7, for instance in response to a rising temperature, the current in line 201 drops by 3.25 A, i.e.14%, which can be detected easily by the central monitoring device 200, so that servicing personnel can be alerted. The same will happen when a power supply unit fails. It is not necessary to monitor the current consumption of each lamp unit individually, which would require the need to arrange multiple current sensors always close to the respective lamp units, because information defining a failure somewhere in a group will narrow down the visual inpection to only a few lamp units. This also applies if the number of lamp units in a group is larger than the exemplary seven.

Summarizing, the present invention provides an illumination system for greenhouses, which comprises:

a plurality of lamp units comprising at least one LED load and a driver;

and a central monitoring device adapted for remotely monitoring at least one operational parameter of the lamp units and for generating an alerting signal for service personnel when it detects that the monitored parameter is outside a predetermined range. A lamp unit may be provided with at least one sensor for sensing the at least one operational parameter, and with communication means for communicating information to the central monitoring device. If a group of lamp units is supplied by a common mains supply line, the system may include a current sensor arranged in or at the common supply line, for communicating to the central monitoring device a current sense signal indicating the actual current flowing in the common supply line.

It should be clear to a person skilled in the art that the present invention is not limited to the exemplary embodiments discussed above, but that several variations and modifications are possible within the protective scope of the invention as defined in the appending claims.

Even if certain features are recited in different dependent claims, the present invention also relates to an embodiment comprising these features in common. Any reference signs in a claim should not be construed as limiting the scope of that claim

Claims

CONCLUSIONS

1. Greenhouse lighting system (20), comprising:

a plurality of lamp units (101) comprising at least one LED load (12) and a driver (17);

a central monitoring device (200) adapted to remotely monitor at least one parameter of the lamp units and to generate an alarm signal (Sa) for service personnel when it detects that the monitored parameter is outside a predetermined range .

The lighting system according to claim 1, wherein a lamp unit is provided with at least one sensor (22) for measuring the at least one parameter, and with communication means (23) for communicating information to the central monitoring device.

The lighting system of claim 2, wherein the operational parameter comprises temperature.

The lighting system according to claim 2 or 3, wherein the information communicated by the lamp unit to the central monitoring device comprises the measured parameter value, and wherein the central monitoring device has an associated memory with information stored therein defining the predetermined range, and wherein the central monitoring device is arranged to compare the received parameter value with the information stored in its memory in order to check whether the monitored parameter is outside the predetermined range, and whether or not to generate the alarm signal (Sa) based on the outcome of this investigation .

The lighting system according to claim 2 or 3, wherein the lamp unit has an associated memory with information stored therein defining the predetermined range, and wherein the lamp unit is adapted to compare the measured parameter value with the information stored in its memory for checking or the monitored parameter is outside a predetermined range, and wherein the lamp unit is adapted to communicate a language condition to the central monitoring device if it detects that the monitored parameter is outside the predetermined range.

6. Lighting system as claimed in any of the foregoing claims 2-5, wherein the communication from the lamp unit to the central monitoring device takes place via a wired link, for example a separate or integrated network of communication wires, or a communication bus, or a supply line.

7. Lighting system as claimed in any of the foregoing claims 2-6, wherein the communication from the lamp unit to the central monitoring device takes place via wireless coupling, for example a wireless communication network, such as Bluetooth, Zigbee, WiFi.

8. Lighting system as claimed in any of the foregoing claims 2-7, wherein the information communicated by the lamp unit to the central monitoring device comprises a unique ID code of the lamp unit and / or of the LED load and / or of the drive device.

9. Lighting system according to any of the preceding claims 2-8, wherein the information communicated by the lamp unit to the central monitoring device comprises information which defines the exact location of the lamp unit.

The lighting system of claim 1, wherein a group of lamp units is powered by a common net supply line (201), and wherein the system comprises a current sensor (203) disposed in or near the common power supply line, to send a current measurement signal (Sc) to the central monitoring device ) to communicate that actually indicates the current flowing in the common power line.

The lighting system of claim 10, wherein the central monitoring device generates the alarm signal (Sa) if the received current measurement signal (Sc) indicates that the total power consumption through the group of lamp units is outside a predetermined expectation range.

The lighting system of claim 10, wherein the central monitoring device generates the alarm signal (Sa) if it detects a sudden current drop from above a predetermined threshold value to below said predetermined threshold value, indicating that one of said lamp units is being switched off.

The lighting system of claim 1, wherein a group of lamp units is powered by a common mains supply line (201) provided with a protected ground line, and wherein the system comprises a current sensor (203) arranged in or near the protected ground line for moving to the central monitoring device communicating a current measurement signal (Sc) which indicates the actual current flowing in the protected earth line.

The lighting system of claim 10, wherein the central monitoring device is adapted to analyze the spectral content of the current and / or the power factor of the current in real time.

The lighting system according to any of the preceding claims, wherein the LED loads are dimmable and the central monitoring device (200) receives information about the dimming states of the LED loads.

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