Renewable energy storage device and power generation method

Abstract

To efficiently store generated power in a secondary battery.SOLUTION: A natural energy storage device 50 includes a plurality of DC power sources 30,35 being combinations of natural energy power generating apparatuses 10,20 and secondary batteries 12,22 that charge power generated by the natural energy power generating apparatuses 10,20, respectively. The secondary battery 12 of the DC power source 30 which generates more power is connected to a load 60, whereas the secondary battery 22 of the DC power source 35 which generates less power is not connected to the load 60. In the natural energy power generating apparatuses 10,20, switching between solar cells and wind power generation facilities is performed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a natural energy power storage device that stores natural energy such as sunlight and wind power in a secondary battery ,oh and a power generation method.

Background Art

[0002] There is a technology that uses solar cells and secondary batteries to wirelessly transmit sensor information such as water level, flow velocity, bridge vibration and captured images to a remote location regardless of day and night. For example, Patent Document 1 discloses a water level gauge that performs measurement and wireless transmission every predetermined time (for example, 30 minutes or 1 hour).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Not limited to water level, when captured images are periodically transmitted wirelessly, if the imaging cycle is short, the power consumption of the imaging camera is larger than the power generated by photovoltaic power generation, which causes the problem that the stored energy of the secondary battery decreases.

[0005] The present invention has been made to solve such problems, and is a natural energy power storage device capable of efficiently storing generated power in a secondary battery ,oh and an object of the present invention is to provide a power generation method.

Means for Solving the Problems

[0006] In order to achieve the above object, The present invention relates to a renewable energy storage device that stores electricity using renewable energy, comprising: a plurality of DC power sources, each having a power generation unit and a secondary battery for charging the power generated by the power generation unit; a voltage measuring unit for measuring the voltage of each secondary battery; and a first switch for connecting any one of the plurality of DC power sources to a load; each power generation unit comprising: a plurality of types of renewable energy power generation equipment; a power generation current monitor for measuring the power generation current of each renewable energy power generation equipment; and a second switch for connecting any one of the plurality of types of renewable energy power generation equipment to the secondary battery; the first switch connects the secondary battery of the DC power source with the highest voltage to the load, and disconnects the secondary batteries of the other DC power sources from the load; and the second switch connects the secondary battery of the renewable energy power generation equipment with the highest power generation, and disconnects the secondary batteries of the other renewable energy power generation equipment from the secondary battery.

Effects of the Invention

[0008] According to the present invention, generated electricity can be efficiently stored in a secondary battery. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing the configuration of a natural energy wireless communication device, which is an embodiment of the present invention. [Figure 2] This is a diagram showing the configuration of the first power generation unit. [Figure 3] This is a diagram showing the configuration of the second power generation unit. [Figure 4] This is a flowchart illustrating the operation of a natural energy wireless communication device, which is an embodiment of the present invention. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the drawings are only schematic representations to the extent necessary to fully understand the embodiments. Furthermore, common or similar components in the drawings are denoted by the same reference numerals, and their redundant descriptions are omitted.

[0011] (Embodiment) Figure 1 is a diagram showing the configuration of a natural energy wireless communication device, which is an embodiment of the present invention. The natural energy wireless communication device 100 is comprised of a natural energy energy storage device 50 and a wireless sensor device 60. The renewable energy storage device 50 is characterized by having multiple DC power sources (e.g., first DC power source 30, second DC power source 35) that combine power generation units (e.g., first DC power generation unit 10, second DC power generation unit 20) and multiple secondary batteries 12, 22 charged by each power generation unit. The first characteristic is that the secondary battery (e.g., secondary battery 12) of the DC power source with high power generation (e.g., first DC power source 30) is connected to the load (wireless sensor device 60), while the secondary battery (e.g., secondary battery 22) of the DC power source with low power generation (e.g., second DC power source 35) is not connected to the load (wireless sensor device 60). As a result, the first DC power source 30, which generates a lot of power, charges the secondary battery 12 and supplies power to the load. On the other hand, the second DC power source 35, which generates little power, does not supply power to the load. Regardless of the amount of power generated, the first DC power source 30 charges the secondary battery 12, and the second DC power source 35 charges the secondary battery 22.

[0012] Furthermore, each power generation unit (first power generation unit 10, second power generation unit 20) is composed of a combination of multiple types of renewable energy power generation equipment. Power generation equipment that generates a large amount of power charges the secondary batteries 12 and 22 and also supplies DC power to the load (wireless sensor device 60), while power generation equipment that generates a small amount of power is configured to only charge the secondary batteries 12 and 22.

[0013] The first power generation unit 10 is equipped with a first solar cell 1a (Figure 2) and a first wind turbine 2a (Figure 2) as other power generation equipment, and generates DC power with voltage V1 and output current I1. The second power generation unit 20 is equipped with a second solar cell 1b (Figure 3) and a second wind turbine 2b (Figure 3) as other power generation equipment, and generates DC power with voltage V3 and output current I2. In other words, the first power generation unit 10 and the second power generation unit 20 store natural energy (solar energy, wind energy, etc.) in secondary batteries 12 and 22. Note that the wind receiving area A [m 2 ], wind speed v[m / s], air density ρ[kg / m 3 When ] is given, the kinetic energy W[J] due to wind force is W=(1 / 2)mv 2 =(1 / 2)ρAv 3This energy (electricity) is then stored in secondary batteries 12 and 22.

[0014] In the first power generation unit 10, the unit that generates more power from the first solar cell 1a and the first wind turbine 2a charges the secondary battery 12 and supplies DC power to the load, while the unit that generates less power charges the secondary battery 12 but does not supply DC power to the load. Similarly, in the second power generation unit 20, the unit that generates more power from the second solar cell 1b and the second wind turbine 2b charges the secondary battery 22 and supplies DC power to the load, while the unit that generates less power charges the secondary battery 22 but does not supply DC power to the load.

[0015] In Figure 1, the renewable energy storage device 50 is configured to include a first DC power source 30, a second DC power source 35, two voltage measuring units 40 and 41, a switch SW1, and a capacitor 45. The first DC power source 30 includes the first power generation unit 10, a power generation current monitor 11, and a secondary battery 12. The second DC power source 35 includes the second power generation unit 20, a power generation current monitor 21, and a secondary battery 22.

[0016] The secondary batteries 12 and 22 are, for example, nickel-metal hydride battery packs with a nominal voltage Vn, consisting of single cells with a nominal voltage of 1.2V connected in series and parallel. The secondary batteries 12 and 22 have a rated capacity C [Ah] and are charged with a constant current of K·C [Ah] / 1h = K·C [A] to prevent overcurrent. Furthermore, the secondary batteries 12 and 22 have the property that the secondary battery charging power (= generated power) increases when no load current is flowing compared to when a load current is flowing. Therefore, in this embodiment, multiple secondary batteries 12 and 22 are provided, and one of the secondary batteries is charged only and not discharged.

[0017] Furthermore, the secondary batteries 12 and 22 have the characteristic that charging cannot be performed with a minute current, and charging is started at a specific current (minimum charging current). Also, this minimum charging current is smaller for a small-capacity secondary battery than for a large-capacity secondary battery. Therefore, when a plurality of secondary batteries 12 and 22 are used as in the present embodiment, charging can be performed even with minute generated power, compared to the case of using a single secondary battery having a capacity equal to the sum of the rated capacities C of each of the secondary batteries 12 and 22. Note that the secondary batteries 12 and 22 are not limited to nickel-metal hydride assembled batteries, and may also be lithium-ion batteries or the like.

[0018] The generated current monitors 11 and 21 detect output currents I1 and I2 (see FIG. 3) of the first power generation unit 10 and the second power generation unit 20. Note that the output current I1 of the first power generation unit 10 is equal to the sum (I3+I4) of a charging current I3 flowing to the secondary batteries 12 and 22 and a load current I4 flowing to a load (wireless sensor device 60) via the switch SW1.

[0019] The voltage measuring units 40 and 41 measure voltages V2 and V4 of the secondary batteries 12 and 22. The switch SW1 is a three-contact switch. Contact a is connected to the first DC power source 30, contact c is connected to the second DC power source 35, and contact b is in an OFF state where it is not connected to either the first DC power source 30 or the second DC power source 35.

[0020] The capacitor 45 is maintained at the voltage of either one of the first DC power source 30 and the second DC power source 35, and supplies DC power to the load (wireless sensor device 60) for a certain period of time even when the switch SW1 is in the OFF state at contact b.

[0021] The wireless sensor device 60 comprises a sensor unit 61, a control unit 65, and a wireless unit 62, and wirelessly transmits information from various sensors to the outside. The sensor unit 61 is composed of any one or a combination of an unillustrated imaging device, a water level gauge, a vibration sensor, and the like. The imaging device, for example, captures images of a river water level periodically (for example, every 1 minute, every 5 minutes). The water level gauge, for example, periodically observes the river water level. The vibration sensor, for example, detects vibration of a bridge constructed over a river.

[0022] The wireless unit 62 wirelessly transmits data detected by the sensor unit 61 (image capture, water level data, vibration data, etc.) to other renewable energy wireless communication devices (not shown) and a server (not shown) using LTE (Long Term Evolution). The wireless unit 62 also communicates with a wireless base station (not shown) that uses Sub-GHz band wireless communication. Furthermore, the wireless unit 62 of this device receives data (image capture, water level data, vibration data, etc.) from other renewable energy wireless communication devices (not shown). In other words, the renewable energy wireless communication device 100 functions as a zero-energy gateway. The control unit 65 is a CPU (Central Processing Unit) that controls the sensor unit 61, the wireless unit 62, and the renewable energy energy storage device 50.

[0023] Figure 2 is a diagram showing the configuration of the first power generation unit 10, and Figure 3 is a diagram showing the configuration of the second power generation unit 20. The first power generation unit 10 (Figure 2) is comprised of a first solar cell 1a, a maximum power point tracking control unit 3a, a constant voltage circuit with overcurrent limiting function 4a, a first wind turbine generator 2a, a rectifier and smoothing circuit 5, a maximum power point tracking control unit 3b, a constant voltage circuit with overcurrent limiting function 4b, and a switch SW2. Similarly, the second power generation unit 20 (Figure 3) is comprised of a second solar cell 1b, a maximum power point tracking control unit 3c, a constant voltage circuit with overcurrent limiting function 4c, a second wind turbine generator 2b, a rectifier and smoothing circuit 5, a maximum power point tracking control unit 3d, a constant voltage circuit with overcurrent limiting function 4d, and a switch SW3.

[0024] The first solar cell 1a and the second solar cell 1b convert solar energy into DC power with voltage V1 and output current I1. The maximum power point tracking control units 3a and 3c vary the voltages V5 and V6 of the first solar cell 1a and the second solar cell 1b to output a current that results in maximum power. The constant voltage circuits 4a and 4c with overcurrent limiting function boost or step down the output voltages V5 and V6 of the first solar cell 1a and the second solar cell 1b, which are controlled by the maximum power point tracking control units 3a and 3c, to charge the secondary batteries 12 and 22 (Figure 1) to nominal voltage Vn. In addition, the constant voltage circuits 4a and 4c with overcurrent limiting function limit the output currents I1 and I2 by the limiting current setting value IL to prevent the secondary batteries 12 and 22 (Figure 1) from being overcharged.

[0025] Furthermore, if the output current I6 of the first solar cell 1a and the second solar cell 1b is less than the limiting current IL, the constant voltage circuit 4a with overcurrent limiting function will not perform current limiting. In this case, the output current I6 = I1 = (power at the maximum power point / voltage V2 of the secondary battery 12 (Figure 1)). In other words, the current (output current I1) obtained by dividing the output power at the maximum power point of the renewable energy power generation equipment (first solar cell 1a, second solar cell 1b, first wind turbine 2a, second wind turbine 2b) (V5 × I6 = V1 × I1 = V2 × I1) by the voltage V2 of the secondary batteries 12 and 22 is less than the allowable charging current IAL of the secondary batteries 12 and 22 (IAL > limiting current setting value IL).

[0026] The first wind turbine 2a and the second wind turbine 2b are rotating electric machines connected to propellers that generate electricity using wind power. Wind power generation is useful at night, during rainy weather, or when solar panels are installed under bridges and sunlight is difficult to reach.

[0027] The rectifier-smoothing circuit 5, which includes diodes and electrolytic capacitors (not shown), converts the AC voltage output by the first wind turbine 2a and the second wind turbine 2b into a DC voltage. The maximum power point tracking control units 3b and 3d vary the output voltage of the rectifier-smoothing circuit 5 to output the current that provides the maximum power. The maximum power point tracking control units 3b and 3d use the voltage fluctuations of the rectifier and smoothing circuit 5 to output the current that results in maximum power. The constant voltage circuits 4b and 4d with overcurrent limiting function boost or lower the output voltage of the first wind turbine 2a and the second wind turbine 2b, which are controlled by the maximum power point tracking control units 3b and 3d, and charge the secondary batteries 12 and 22 (Figure 1) to their nominal voltage Vn.

[0028] Switch SW2 is a switch that switches between the output voltage of the overcurrent-limiting constant voltage circuit 4a and the output voltage of the overcurrent-limiting constant voltage circuit 4b. In other words, switch SW2 switches between the power generated by the first solar cell 1a and the power generated by the first wind turbine 2a. Switch SW3 is a switch that switches between the output voltage of the overcurrent-limiting constant voltage circuit 4c and the output voltage of the overcurrent-limiting constant voltage circuit 4d. In other words, switch SW3 switches between the power generated by the second solar cell 1b and the power generated by the second wind turbine 2b.

[0029] Figure 4 is a flowchart illustrating the operation of a natural energy wireless communication device 100, which is an embodiment of the present invention. This flowchart is activated by power-on or reset. Voltage measuring units 40 and 41 (Figure 1) measure the voltage of each secondary battery 12 and 22 (S1). After processing in S1, the control unit 65 (Figure 1) determines whether the voltages of both secondary batteries 12 and 22 are below a threshold (S2). If the voltages of both secondary batteries 12 and 22 are below the threshold (YES in S2), the control unit 65 sets switch SW1 to contact b, turning it OFF (S3). As a result, the wireless sensor device 60 stops working, but the secondary batteries 12 and 22 continue to charge.

[0030] On the other hand, if the voltage of either secondary battery 12 or 22 exceeds the threshold (NO in S2), the control unit 65 compares the voltages of secondary batteries 12 and 22 (S4). If the voltage of secondary battery 12 is higher than the voltage of secondary battery 22, the control unit 65 sets switch SW1 to contact a, creating path 1 (S5). After processing in S5, the control unit 65 determines whether the power generation current measured by the power generation current monitor 11 (Figure 1) is below the threshold (S6). If the power generation current is below the threshold (YES in S6), the control unit 65 switches switch SW2 (Figure 2) (S7). In other words, if the power generation current of the first solar cell 1a is below the threshold, the secondary battery 12 is charged by the first wind turbine 2a. Conversely, if the power generation current of the first wind turbine 2a is below the threshold, the secondary battery 12 is charged by the first solar cell 1a. After processing in S7, or if the generated current exceeds the threshold in S6 (NO in S6), the control unit 65 returns the process to S1 and measures the voltages of the secondary batteries 12 and 22.

[0031] On the other hand, in S4, if the voltage of the secondary battery 22 is higher than that of the secondary battery 12, the control unit 65 sets the switch SW1 (Figure 1) to contact c and switches to path 2 (S8). After processing in S8, the control unit 65 determines whether the power generation current measured by the power generation current monitor 21 (Figure 1) is below a threshold (S9). If the power generation current is below the threshold (YES in S9), the control unit 65 switches the switch SW3 (Figure 2) (S10). In other words, if the power generation current of the second solar cell 1b is below the threshold, the secondary battery 22 is charged by the second wind turbine 2b. Conversely, if the power generation current of the second wind turbine 2b is below the threshold, the secondary battery 22 is charged by the second solar cell 1b. After processing in S10 or if the power generation current exceeded the threshold in S9 (NO in S9), the control unit 65 returns to processing in S1 and measures the voltages of the secondary batteries 12 and 22.

[0032] Conventional charge-discharge systems discharge to the load while simultaneously charging the secondary battery. In the natural energy storage device 50 of this embodiment, both a discharge path (for example, path 1 when switch SW1 is set to contact a (Figure 1)) that charges the secondary battery and discharges from the secondary battery to the load, and a separate path that is dedicated to charging (for example, path 2 when switch SW1 is set to contact a (Figure 1)) are provided. As a result, the charging efficiency and amount of the secondary battery 22 in path 2, which does not carry load current, are increased. Furthermore, since the natural energy storage device 50 is equipped with multiple secondary batteries 12, 22, the minimum charging current is smaller than that of a single secondary battery with a combined capacity of all secondary batteries, so charging can be performed even with a small amount of generated power.

[0033] Furthermore, the renewable energy storage device 50 of this embodiment can be charged at night or during rainy weather by providing charging lines from other power generation equipment (for example, the first wind turbine 2a and the second wind turbine 2b) that are different from the solar cells (first solar cell 1a and second solar cell 1b). As a result, the amount of charge in the secondary batteries 12 and 22 increases, leading to an increase in communication frequency and the amount of sensor information.

[0034] (modified version) The present invention is not limited to the embodiments described above, and various modifications are possible, for example, as follows. (1) In the above embodiment, in addition to solar cells (first solar cell 1a, second solar cell 1b), wind turbines (first wind turbine 2a, second wind turbine 2b) were used. However, water-flow generators that convert river water flow into electrical energy, thermoelectric generators that utilize the temperature difference between a structure and its surroundings, and vibration generators that utilize the vibration of a structure can also be used. (2) In the above embodiment, constant voltage circuits 4a, 4b, 4c, and 4d with overcurrent limiting function were used. However, if the power generated by the solar cell or wind turbine is small and the charging current is less than or equal to the charging current limit value of the secondary batteries 12 and 22, there is no need for a function to limit the overcurrent. (3) In the above embodiment, the maximum power point tracking control units 3b and 3d were connected to the wind turbines (first wind turbine 2a and second wind turbine 2b), but it is not necessarily required to connect the maximum power point tracking control units 3b and 3d. (4) The natural energy wireless communication device 100 of the above embodiment can be applied to a system in which data from a high-power sensor (e.g., an imaging camera) used for monitoring infrastructure structures is sent to a server or a short-range wireless base station at short intervals. [Explanation of symbols]

[0035] 1a First Solar Cell (Renewable Energy Power Generation Equipment) 1b Second solar cell (renewable energy power generation equipment) 2a. First wind turbine (renewable energy power generation equipment, other power generation equipment) 2b. Second wind turbine (renewable energy power generation equipment, other power generation equipment) 3a,3b,3c,3d Maximum power point tracking control section 4a, 4b, 4c, 4d Constant voltage circuit with overcurrent limiting function (overcurrent limiting circuit, low voltage circuit) 5 Rectifier smoothing circuit 10. First power generation unit 12,22 Secondary battery 20 Second power generation unit 50 Renewable Energy Storage Devices 60 Wireless sensor device (load) 100 Renewable Energy Wireless Communication Devices

Claims

1. A natural energy storage device that stores electricity using natural energy, A plurality of DC power sources, each having a power generation unit and a secondary battery that charges the power generated by the power generation unit, A voltage measuring unit for measuring the voltage of each of the aforementioned secondary batteries, The system includes a first switch that connects one of the multiple DC power sources to a load, Each of the aforementioned power generation units is The system comprises multiple types of renewable energy power generation equipment, a power generation current monitor for measuring the power generation current of each of the renewable energy power generation equipment, and a second switch for connecting any one of the multiple types of renewable energy power generation equipment to the secondary battery. The first switch connects the secondary battery of the DC power source with the highest voltage to the load, and disconnects the secondary batteries of the other DC power sources from the load. The second switch connects the renewable energy power generation device that generates the most power to the secondary battery, and disconnects the other renewable energy power generation devices from the secondary battery. A renewable energy storage device characterized by the following features.

2. A renewable energy storage device according to claim 1, The aforementioned renewable energy power generation equipment is a combination of a solar cell and a wind turbine. The secondary battery is charged using the power generated by the solar cell or the wind turbine, whichever generates more power. A renewable energy storage device characterized by the following features.

3. A renewable energy storage device according to claim 1 or claim 2, The current obtained by dividing the output power at the maximum power point of the renewable energy power generation device by the voltage of the secondary battery is less than the allowable charging current of the secondary battery. A renewable energy storage device characterized by the following features.

4. A method for generating electricity for a renewable energy storage device that stores electricity using renewable energy, The aforementioned natural energy storage device is A plurality of DC power sources, each having a power generation unit and a secondary battery that charges the power generated by the power generation unit, A voltage measuring unit for measuring the voltage of each of the aforementioned secondary batteries, The system includes a first switch that connects one of the multiple DC power sources to a load, Each of the aforementioned power generation units is The system comprises multiple types of renewable energy power generation equipment, a power generation current monitor for measuring the power generation current of each of the renewable energy power generation equipment, and a second switch for connecting any one of the multiple types of renewable energy power generation equipment to the secondary battery. A first switching step involves using the first switch to connect the secondary battery of the DC power source with the highest voltage to the load, and disconnecting the secondary batteries of the other DC power sources from the load. The system includes a second switching step in which the second switch connects the renewable energy power generation device with the highest generated power to the secondary battery, and disconnects the other renewable energy power generation devices from the secondary battery. A power generation method characterized by the following features.

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