Lighting system, plant factory, and control method

Abstract

To provide a technique for reducing heat generation in a growth chamber more than before in an illumination system applied to a plant factory SOLUTION: An illumination system applied to a plant factory includes a plurality of illumination devices each having an LED element and provided in a temperature-controlled growth chamber, and a power supply circuit for supplying power from a DC power supply provided outside the growth chamber to the plurality of illumination devices in the growth chamber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lighting system, a plant factory, and a control method. [Background technology]

[0002] An artificial lighting device applicable to a plant factory is known (Patent Document 1). This artificial lighting device includes an LED lighting device equipped with a large number of LED elements, an input splitter that splits three-phase power supplied from a three-phase AC power source as an input power source into UV and W inputs, full-wave rectifiers that individually full-wave rectify each input of the input splitter, a single-phasing unit that superimposes the outputs full-wave rectified by each full-wave rectifier to form a single phase, and a single-phasing power supply unit that uses the output of the single-phasing unit as the power supply for the LED lighting device. The artificial lighting device supplies power to the LED lighting device from the single-phasing power supply unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-16580 Summary of the Invention [Problem to be solved by the invention]

[0004] Plant factories often have relatively large-scale lighting equipment, and reducing electrical losses in the power supply to the lighting equipment is desirable from the perspective of cost reduction. If the heat generated by electrical losses is large, the power consumption required to exhaust heat to maintain an appropriate environment inside the growth chamber may also increase.

[0005] The present invention provides a technology for reducing heat generation in a growth chamber in a lighting system applied to a plant factory compared to conventional technology. [Means for solving the problem]

[0006] The present invention includes the following aspects. [Aspect 1] A lighting system applied to a plant factory, a plurality of lighting devices each having an LED element and installed in a temperature-controlled growth chamber; a power supply circuit that supplies power from a DC power source provided outside the growth chamber to the plurality of lighting devices inside the growth chamber; Equipped with Lighting system. [Aspect 2] 2. The lighting system of embodiment 1, Further comprising a current limiting element that limits the current flowing to the LED element. Lighting system. [Aspect 3] 3. The lighting system of claim 2, The current limiting is performed by a PWM (pulse width modulation) method. Lighting system. [Aspect 4] The lighting system according to any one of aspects 2 and 3, the power supply circuit includes a PWM control circuit; The PWM control circuit sends a pulse signal to the plurality of lighting devices, thereby controlling the current flowing through the LED elements. Lighting system. [Aspect 5] The lighting system according to any one of aspects 2 to 4, the plurality of current limiting elements are field effect transistors; Lighting system. [Aspect 6] The lighting system according to any one of aspects 1 to 5, In the power supply circuit, a step-down circuit is not provided inside the growth chamber. Lighting system. [Aspect 7] The lighting system according to any one of aspects 1 to 7; The growth chamber; Equipped with plant factory. [Aspect 8] A method for controlling lighting in a plant factory, comprising: The plant factory comprises: A temperature-controlled growth chamber; A plurality of lighting devices each having an LED element and installed inside the growth chamber; Equipped with The control method includes: supplying power to the plurality of lighting devices inside the growth chamber from a DC power source provided outside the growth chamber; Including, Control method. [Effects of the Invention]

[0007] According to the present invention, a technology is provided for reducing heat generation in a growth chamber in a lighting system applied to a plant factory compared to conventional techniques. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an overview of a plant factory according to an embodiment. [Figure 2] Lighting system circuit configuration diagram [Figure 3] A diagram showing an example of a circuit configuration in which AC current is converted to DC current within a lighting device and the DC current is guided to an LED element. [Figure 4] 4A is a diagram showing the efficiency of the LED lighting device having the circuit configuration shown in FIG. 3, and FIG. 4B is a diagram showing the efficiency of the lighting system according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Plant factory] FIG. 1 is a diagram illustrating an overview of a plant factory 1 according to one embodiment. The plant factory 1 includes a growth chamber 10, a lighting system 20, and a DC power supply 30. In this specification, the plant factory 1 refers to a system capable of artificially cultivating plants. For example, in addition to the lighting system 20 described below, the plant factory 1 may be equipped with plant production shelves on which cultivated plants are placed, an air conditioning device that maintains the temperature, humidity, etc., inside the growth chamber 10 at levels suitable for the growth of cultivated plants, and a device that supplies carbon dioxide to the cultivated plants inside the growth chamber 10.

[0010] DC power supply 30 is provided outside growth chamber 10 and supplies power to lighting system 20. DC power supply 30 may convert commercial AC power into DC power and supply it to lighting system 20. DC power supply 30 may also supply power generated by solar power generation to lighting system 20. The specifications of DC power supply 30 may be determined depending on the number of lighting devices 21 arranged in parallel and the specifications of the lighting devices 21. [Lighting System] <Summary> 2 is a schematic diagram of a circuit configuration of the lighting system 20. The lighting system 20 is applied to the plant factory 1. The lighting system 20 includes a plurality of lighting devices 21 and a power supply circuit 22. <Lighting equipment>

[0011] A plurality of lighting devices 21 are provided inside the temperature-controlled growth chamber 10. The number of lighting devices 21 is not limited, but for example, 100 or more lighting devices 21 may be provided in parallel. Each of the lighting devices 21 includes an LED element 211 and a current-limiting element 212.

[0012] A plurality of LED elements 211 are provided in each lighting device 21. The LED elements 211 can emit light of a wavelength necessary for photosynthesis of cultivated plants, and are used as artificial light sources in the plant factory 1. In this embodiment, the plurality of LED elements 211 are arranged in series. However, the plurality of LEDs 211 may also be arranged in a combination of series and parallel. The number of LED elements 211 included in a lighting device 21 may be 10 to 200. All of the LED elements 211 may be arranged on one board within the lighting device 21, or the lighting device 21 may have a plurality of boards connected in series or in parallel, each with an LED element 211 arranged on it.

[0013] The current limiting element 212 limits the current flowing to the LED element 211. In this embodiment, the current limiting element 212 is a field-effect transistor. More specifically, the current limiting element 212 may be a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). Alternatively, a constant current diode or the like may be used as the current limiting element 212. Note that, although each of the multiple lighting devices 21 includes a current limiting element 212 in this embodiment, the current limiting element 212 may be provided separately from the lighting device 21. That is, it is sufficient that the overall circuit is configured so that the current after current limiting flows to each LED element 211 of each lighting device 21. In this case, the lighting system 20 may include a current limiting element 212 corresponding to each lighting device 21, or may include a number of current limiting elements 212 fewer than the number of lighting devices 21.

[0014] In addition, the lighting device 21 may include a substrate (not shown) on which the plurality of LED elements 211 and one current limiting element 212 are provided, a casing (not shown) that covers these, and the like. Furthermore, the lighting device 21 of this embodiment does not include elements for converting AC current to DC current (rectifying and smoothing circuit, switching unit, high-frequency transformer, high-frequency rectifying circuit, etc.) that are generally provided in LED lighting devices that connect to a commercial AC power source. In other words, the lighting device 21 does not require conversion from AC current to DC current or stepping down, etc., and therefore can suppress heat generation that would otherwise occur. This will be described in more detail below. <Power supply circuit> Power supply circuit 22 supplies power from DC power supply 30 provided outside growth chamber 10 to multiple lighting devices 21 inside growth chamber 10. Power supply circuit 22 includes conductor section 221 that conducts DC current from DC power supply 30 to lighting devices 21, a PWM (pulse width modulation) control circuit 222 described below, and conductor section 223 that conducts current from PWM control circuit 222 to each lighting device 21.

[0015] The PWM control circuit 222 is a circuit that generates a square-wave pulse signal. A known configuration can be used as the specific configuration of the PWM control circuit 222. The PWM control circuit 222 sends a pulse signal to the current limiting element 212 of the lighting device 21, thereby controlling the current flowing through the LED element 211. The PWM control circuit 222 controls the duty ratio of the pulse signal, thereby adjusting the brightness of the lighting device 21. For example, the PWM control circuit 222 generates a pulse signal at a frequency of 1 to 100 kHz. The PWM control circuit 222 may be installed inside or outside the growth chamber 10.

[0016] In this embodiment, current is constantly supplied to each lighting device 21 from the DC power supply 30, but when no pulse signal is sent from the PWM control circuit 222 to the current limiting element 212, no current flows between the drain and source of the current limiting element 212 (MOSFET), and the LED element 211 does not emit light. On the other hand, when a pulse signal is sent from the PWM control circuit 222 to the current limiting element 212, current flows between the drain and source of the current limiting element 212 (MOSFET), and the LED element 211 emits light.

[0017] [Heat generation in plant factories] In general, in a plant factory, it is desirable to reduce heat generation due to electrical losses in the power supply to the lighting devices. If heat generation is large, in addition to the electrical losses themselves, a large amount of power may be required to exhaust the heat to maintain an appropriate environment inside the growth chamber 10.

[0018] For comparison with this embodiment, consider a case where current from a commercial AC power source is introduced to a lighting device in growth chamber 10, where the AC current is converted to DC within the lighting device, and the DC current is introduced to an LED element. Figure 3 is a diagram showing an example of a circuit configuration where the AC current is converted to DC within the lighting device, and the DC current is introduced to an LED element.

[0019] In such a case, the lighting device 900 may include a rectifying and smoothing circuit 901, a switching unit 902 such as a transistor or MOSFET, a high-frequency transformer 903, a high-frequency rectifying circuit 904, and the like. The lighting device 900 may also include a detecting unit 905 that detects and compares the output voltage, and a pulse-width control unit 906 that controls the pulse width of the signal output to the switching unit by feeding back the results of the detection and comparison by the detecting unit 905. This configuration is technically established and relatively inexpensive to implement, and is therefore commonly used in LED lighting devices. However, the rectifying and smoothing circuit 901, the switching unit 902 such as a transistor or MOSFET, the high-frequency transformer 903, the high-frequency rectifying circuit 904, and the like can generate significant heat loss. In a typical LED lighting device, such heat loss is not a problem because LED lighting is more efficient than other lighting sources such as fluorescent lamps. However, the lighting devices used in the plant factory 1 often use a large number of LED elements, and such heat loss can become significant.

[0020] In this embodiment, no conversion from AC to DC is performed inside the growth chamber 10, and therefore no heat is generated inside the growth chamber 10 due to the above-mentioned elements for AC-DC conversion. Therefore, heat generation inside the growth chamber 10 can be suppressed. When conversion from AC to DC is performed in the DC power supply 30, electrical loss occurs in the DC power supply 30, but no power is required to exhaust the heat generated by the electrical loss. Therefore, total power consumption can be suppressed.

[0021] In addition, in this embodiment, by supplying direct current to the lighting device 21 and configuring it so that a step-down circuit is not installed inside the growth chamber 10, heat generation inside the growth chamber 10 can be suppressed compared to a lighting device with a circuit configuration such as that shown in Figure 3.

[0022] A typical AC-DC switching power supply such as that shown in Figure 3 is said to have an efficiency of approximately 80%. For example, if the DC output of the power supply is 50V·0.44A=22W, the power consumption on the power supply side is 200V·0.41A=28W, resulting in an efficiency of approximately 80% and approximately 20% being heat loss. In the lighting device 21 of this embodiment, heat loss in the current limiting element 212 constitutes heat loss for the lighting device 21, but this is extremely small compared to lighting devices with typical AC-DC switching power supplies. Specifically, if the DC output is 22W, heat loss in the current limiting element 212 can be suppressed to approximately 0.1W.

[0023] Furthermore, when a lighting device includes a rectifying / smoothing circuit or a high-frequency rectifying circuit, the electrolytic capacitors included in these circuits generally have a shorter device lifespan than LED elements. Therefore, the lifespan of the lighting device depends on the lifespan of the electrolytic capacitor, and there is a risk that the lifespan may be shorter than that of the LED elements. The lighting device 21 of this embodiment is expected to have a longer lifespan than lighting devices that include electrolytic capacitors.

[0024] Furthermore, when a MOSFET is used as the current limiting element 212, the current supplied to the LED elements 211 can be adjusted by the control of the PWM control circuit 222 without changing the power supply voltage. This allows the lighting device 21 to operate with higher efficiency. For example, if the current is halved without changing the voltage, the illuminance of the LED elements 211 is approximately halved because it is proportional to the current. On the other hand, the heat generated by the LED elements 211 is approximately halved because it is proportional to the square of the current. Therefore, for example, by halving the current and doubling the number of LED elements 211 while maintaining the original voltage, current, and number of LED elements 211, the amount of heat generated can be reduced to approximately halved while maintaining the original illuminance, thereby improving efficiency. As an example, it is possible to pass half the rated current through the LED elements 211 and use twice the number of LED elements 211 compared to when the rated current is passed through the LED elements 211.

[0025] FIG. 4(a) is a diagram schematically illustrating the efficiency of the LED lighting device having the circuit configuration of FIG. 3. FIG. 4(b) is a diagram schematically illustrating the efficiency of the lighting system 20 according to this embodiment. Here, efficiency refers to the ratio of the light output emitted by the lighting device to the power consumption of the commercial AC power supply. FIG. 4(a) shows the efficiency when a rated current is passed through the LED elements 211. FIG. 4(b) shows the efficiency when a MOSFET is used as the current limiting element 212, half the rated current is passed through the LED elements 211, and twice the number of LED elements 211 is used compared to when the rated current is passed through the LED elements 211.

[0026] First, let us refer to Figure 4(a). In the circuit configuration of Figure 3, commercial AC power is directly supplied to the lighting device 900. In this case, as described above, the efficiency of AC / DC conversion and voltage step-down by the rectifying and smoothing circuit 901, switching unit 902, high-frequency transformer 903, and high-frequency rectifying circuit 904 is approximately 80%. Therefore, at the stage of conversion to DC, approximately 20% is lost. As an example, if two-thirds of the power supplied to the LED element 211 is lost as heat and one-third is light output, the efficiency is approximately 27%.

[0027] Next, refer to FIG. 4(b). In this embodiment, a DC power supply 30 installed outside the growth chamber 10 converts commercial AC current to DC current. The DC power supply 30 converts commercial AC current to DC current supplied to each lighting device 21 in the lighting system 20 in a centralized manner, enabling more efficient conversion than when each lighting device uses its own AC-DC conversion circuit. For example, the DC power supply 30 is expected to perform AC-DC conversion with approximately 90% efficiency. Furthermore, as described above, the lighting device 21 may experience heat loss from the MOSFET current-limiting element 212 (e.g., approximately 0.1 W for a 22 W DC output). Even if this is reduced to 1%, halving the current flowing through the LED element 211 halves the heat loss in the LED element 211. Therefore, for an LED element 211 similar to the one illustrated in FIG. 4(a), two-thirds of the supplied power is lost as heat and one-third is used as light output. Therefore, the final efficiency is approximately 59%.

[0028] In addition, even if the current value flowing through the LED elements 211 and the number of LED elements 211 in the lighting system 20 of this embodiment are the same as those in the example shown in Fig. 4(a), the efficiency up to DC conversion is 89%, which is higher than the 80% in the example shown in Fig. 4(a). Therefore, higher efficiency can be achieved compared to the circuit configuration in Fig. 3.

[0029] The present invention has been described above based on the respective embodiments. However, the present invention is not limited to the above embodiments, and modifications may be made without departing from the spirit of the present invention. Furthermore, the techniques described in the respective embodiments may be appropriately combined, or the techniques of the above embodiments may be appropriately combined with known techniques. [Explanation of symbols]

[0030] 1 Plant factory, 10 Growth chamber, 20 Lighting system, 21 Lighting device, 22 Power supply circuit, 211 LED element

Claims

1. A lighting system applied to a plant factory, a plurality of lighting devices each having an LED element and installed in a temperature-controlled growth chamber; a power supply circuit that supplies power from a DC power source provided outside the growth chamber to the plurality of lighting devices inside the growth chamber; Equipped with Lighting system.

2. 10. The lighting system of claim 1, Further comprising a current limiting element that limits the current flowing to the LED element. Lighting system.

3. 3. A lighting system according to claim 2, The current limiting is performed by a PWM (pulse width modulation) method. Lighting system.

4. 3. A lighting system according to claim 2, the power supply circuit includes a PWM control circuit; The PWM control circuit sends pulse signals to the plurality of lighting devices to control the current flowing through the LED elements. Lighting system.

5. 3. A lighting system according to claim 2, the plurality of current limiting elements are field effect transistors; Lighting system.

6. 10. The lighting system of claim 1, In the power supply circuit, a step-down circuit is not provided inside the growth chamber. Lighting system.

7. A lighting system according to any one of claims 1 to 6; The growth chamber; Equipped with plant factory.

8. A method for controlling lighting in a plant factory, comprising: The plant factory comprises: A temperature-controlled growth chamber; a plurality of lighting devices each having an LED element and installed inside the growth chamber; Equipped with The control method includes: supplying power to the plurality of lighting devices inside the growth chamber from a DC power source provided outside the growth chamber; Including, Control method.

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