Energy storage system

Abstract

An energy storage system (10) having cells (11) arranged in series and a battery management system for monitoring voltages of the cells (11). Connection lines extend from a battery management controller to cell junctions. A voltage generator generates a first voltage on the first connection line and a second voltage on the second connection line and a control circuit is provided between each of the first and second connection lines and each of the junctions to which the connection line is connected. When the first and second voltages are generated, the control circuits will connect between the first connection line and a first cell junction where the voltage at said first cell junction is within a range of the first voltage and will connect between the second connection line and a second cell junction where the voltage at said second cell junction is within a range of the second voltage.

Description

“ENERGY STORAGE SYSTEM”Field of the Invention

[0001] The present invention relates to a system for storage of energy within batteries.Background to the Invention

[0002] With increasing use of renewal energy power sources such as solar and wind, the ability to store this generated energy for use as required is becoming increasingly important. Energy storage devices comprising batteries contained within a suitable housing can certainly be used for this purpose but present a variety of problems, such as high cost, lifespan limitations and safety and maintenance issues.

[0003] The use of battery storage utilising a number of standard cells stored within a housing provides for advantages in the cost of production and maintenance. In order to effectively manage operation of such a system, it is particularly useful to be able to monitoring the state of individual batteries within the system and control the rate of charging and / or discharging for each cell. In order to achieve such control, it would generally be necessary to having individual addressed connections to each individual cell to monitoring the individual voltage of each cell and control current flow in and out. Such an arrangement however can be relatively complex and expensive to implement.

[0004] The present invention comprises an energy storage system provided to store energy within batteries where individual connection to cells within the system is provided in a way which aims to overcome, at least in part, the abovementioned issue.Summary of the Invention

[0005] According to one aspect of the present invention there is provided an energy storage system comprising: a housing having a plurality of cells arranged in a series, each cell having terminals at opposite ends such that adjacent terminals of the cells connect at one or more cell junctions within the series of the cells; a battery management system provided for monitoring voltages of the cells and controlling current flow in and out of the cells; a first connection line extending from a battery management controller of the battery management system to cell junctions within the series of cells; a second connection line extending from the battery management controller of the battery management system to cell junctions within the series of cells; a voltage generator provided to generate a first voltage on the first connection line and a second voltage on the second connection line; and a control circuit provided between each of the first and second connection lines and each of the junctions to which the connection line is connected; wherein when the first and second voltages are generated on the first and second connection lines, the control circuits will connect between the first connection line and a first cell junction where the voltage at said first cell junction is within a voltage range of the first voltage and will connect between the second connection line and a second cell junction where the voltage at said second cell junction is within a voltage range of the second voltage.

[0006] Preferably the first and second connection lines may connect across a single cell within the series of cells or a set of cells within the series.

[0007] Preferably the first and second connection lines are connected to alternate junctions within the series of cells.

[0008] Preferably the cells are connected in a column contained within a tubular member.

[0009] Preferably each column includes two or more columns of cells.

[0010] Preferably the first and second connection lines extend to connection boards provided in the column between adjacent pairs of cells, the connection boards including tabs extending outwardly to connect to the junctions between adjacent cells.

[0011] Preferably the control circuits are provided on the connection boards.

[0012] In a preferred embodiment, the tubular members mounted to a base frame.

[0013] Preferably an upper frame is provided connected to upper ends of the tubular members, the upper frame including the battery management system.

[0014] Preferably each of the connection boards is oriented parallel to a longitudinal axis of the tubular member and includes first tabs extending outwardly from a first side thereof to connect to electrical contacts on an adjacent pair of cells from the first column and second tabs extending outwardly from a second side of each of the connection boards to connect to electrical contacts on an adjacent pair of cells from the second column.

[0015] Preferably each of the tubular members includes first and second side walls being parallel and planar first and second end walls each being arcuate in transverse cross section.

[0016] Preferably the tubular members are obround in transverse cross-section such that a first column of cells is received adjacent the first end wall and a second column of cells is received adjacent the second end wall.

[0017] Preferably each of the tubular members includes first and second guide rails extending longitudinally down inner surfaces of the first and second side walls, each of the first and second guide rails including a channel to receive an edge of the connection boards.

[0018] Preferably each of the guide rails includes a longitudinal groove which receives in use a corresponding rib extending along an inner surface of the first and second side walls of the tubular member.

[0019] Preferably the tubular members are provided in a generally rectangular array.Brief Description of the Drawings

[0020] The invention will now be described, by way of example, with reference to the following drawings, in which:

[0021] Figure 1a is an upper perspective view of an energy storage system in accordance with the present invention;

[0022] Figure 1 b is a front view of the energy storage system of Figure 1 a;

[0023] Figure 2 is a perspective view of a row of the tubular members of the energy storage system of Figure 1 ;

[0024] Figure 3 is a perspective view of an end of the tubular members of Figure 4;

[0025] Figure 4 is a perspective view of the energy storage system in a tilted position;

[0026] Figure 5 is a perspective view of upper ends of the first and second columns of cells to be received in the tubular members of the energy storage system; and

[0027] Figure 6 is a view of examples of control circuits for controlling connection between the connection lines and junctions between adjacent cells.Detailed Description of Preferred Embodiments

[0028] Referring to the Figures, there is shown an energy storage system 10 comprising a housing 18 for storing a plurality of cells 11. The cells 11 may comprise cylindrical batteries of a standard construction for receiving and storing energy and delivering electrical energy as required.

[0029] In the embodiment shown, the housing 18 comprises a base frame 12, an upper frame 14 and a plurality of tubular members 16. The base frame 12 is to be mounted adjacent the ground in use such that the tubular members 16 extend upwardly from the base frame 12 and the upper frame 14 engages withupper ends of the tubular members 16. Each of the tubular members 16 is provided for receiving a plurality of cells 11 .

[0030] The housing 18 is provided for receiving columns of cells 11 , where each column comprises a series of cells 11 stacked end to end to create a column voltage. The energy storage system 10 may include an inverter such that the voltages produced by the columns of cells may be switched in and out of series connections to provide a stepwise approximation of an AC signal which is then smoothed by suitable means to generate an output AC signal.

[0031] In the embodiment shown, each of the tubular members 16 is provided for receiving a first column 13 of cells 11 adjacent a first side thereof and a second column 15 of cells 11 adjacent a second side. The first and second columns 13 and 15 of cells 11 are parallel in use and extend throughout the length of the tubular members 16. Each of the tubular members 16 includes a first side wall 22, a second side wall 23, a first end wall 24 and a second end wall 25. The first and second side walls 22 and 23 are parallel and planar and each of the first and second end walls 24 and 25 are arcuate in transverse cross section. The tubular members 16 in the embodiment shown are therefore generally obround in transverse cross section to receive the first and second columns 13 and 15 of cylindrical cells 11 .

[0032] The tubular members 16 in the embodiment shown are provided in a generally rectangular array and lower ends thereof engage with the base frame 12 which is rectangular in shape. The tubular members 16 are arranged in the array into rows, where each tubular member 16 within the row has the second side wall 23 thereof located parallel and adjacent to the first side wall 22 of an adjacent tubular member 16, and columns, where each tubular member 16 within the column has the second end wall 25 thereof located adjacent the first end wall 24 of an adjacent tubular member 16.

[0033] The base frame 12 comprises generally a planar member having a plurality of openings 26. The openings 26 corresponds in shape to the cross- sectional shape of the tubular members 16 and are dimensioned such thatlower ends of the tubular member 16 engage around the periphery of the openings 26.

[0034] The base frame 12 is mounted to a base plate 20. The base plate 20 is to be secured to the ground in use by suitable means, such as by threaded fasteners passing into the ground. The base frame 12 is connected by one or more hinges to the base plate 20 such that that the tubular members 16 can be tilted (as shown in Figure 4) to access the cells 11 .

[0035] Inner sides of each of the first and second side walls 22 and 23 of the tubular members 16 are provided with corresponding first and second ribs 42 and 43 extending along the length of the tubular member 16 (as shown in Figure 3). Each of the first and second ribs 42 and 43 are located centrally on the first and second side walls 22 and 23 such that the ribs 42 and 43 are located generally between the first and second columns 13 and 15 of the cells 11 .

[0036] The upper frame 14 is provided to engage with upper ends of the tubular members 16 and to engage upper ends of the columns of 13 and 15 of cells 11. The upper frame 14 includes circuitry provided to electrically connect to each column 13 and 15 of cells 11 such that the voltages produced by the columns 13 and 15 of cells 11 may be switched in and out of series connections to provide a stepwise approximation of an AC signal. The stepwise approximation of an AC signal formed may be smoothed by suitable means to generate an output AC signal.

[0037] The upper frame 14 includes a fan 54 provided to direct airflow upwardly or downwardly between the tubular spaces defined between each adjacent set of four tubular members 16 for cooling purposes.

[0038] The energy storage system 10 includes a battery management system provided to allow balancing of the voltages of each individual cell 11 within the columns 13 and 15. Connections are therefore provided to each individual cell 11 by means of connection boards 56 provided within each of the tubular members 16. Each of the connection boards 56 provides connection to adjacent pairs of cells 11 in both the first and second columns 13 and 15.

[0039] As can be seen in Figure 3, each of the tubular members 16 includes first and second guide rails 58 and 59 extending longitudinally down inner surfaces of the first and second side walls 22 and 23. Each of the guide rails 58 and 59 includes a longitudinal groove 60 which receives in use the corresponding rib 42 or 43. Extending outwardly from adjacent the groove 60 there is provided a channel 62 in each of the guide rails 58 and 59. The channels 62 are provided such that the connection boards 56 may be slid longitudinally into the tubular members 16 so that opposed edges of the connection boards 56 are received in the channels 62 and located between the adjacent columns 13 and 15 of cells 11.

[0040] Each of the connection boards 56 includes a first tab 64 extending outwardly from first side thereof and a second tab 65 extending outwardly from a second side thereof. The first tabs 64 are provided to engage between an adjacent pair of cells 11 in the first column 13 and the second tabs 65 are provided to engage between adjacent pair of cells 11 in the second column 15. The connection boards 56 thereby provide connection to opposed ends of each individual cell 11 and the connection boards 56 are connected and controlled by the battery management system to allow energy to be extracted from or injected to each individual cell 11 to allow balancing of the cells within the columns 13 or 15. The connection boards 56 are connected together by flexible cables including wires provided to pass electrical signals to and from the connection boards 56. The flexible cables may comprise flexible ribbon cable.

[0041] It will be appreciated that while the embodiment described shows first and second columns of cells 11 in each of the tubular members 16, the tubular members 16 may also include additional columns of cells 11. In a further embodiment for example (not shown), each of the tubular members 16 may have greater width in order to accommodate third and fourth columns of cells.

[0042] The energy storage system 10 includes also a battery management system. The battery management system is provided for monitoring the voltage of cells 11 within the system and controlling the flow of current into or out of individual cells 11 , or sets of cells 11 , to control the voltage on the cells 11 .

[0043] The battery management system includes connection lines which extend from a battery management controller to junctions between adjacent pairs of cells 11 within each column 13, 15 of cells 11. The connection lines therefore extend downwardly through the flexible cables within the tubular members 16 to each of the connection boards 56.

[0044] There is provided first and second connection lines within each of the tubular members provided such that the first and second connection lines can each selectively connect to one of junctions between adjacent cells 11 within the column. By connecting, for example, the first connection line to a junction above a particular cell 11 and the second connection line to a junction below said cell 11 , the battery management system can detect the voltage on the cell 11 and also vary the charge level of the individual cell 11 by controlling current flow along the first and second connection lines. The first and second connection lines may also be connected to junctions separated across multiple cells 11 to control charging or discharging of multiple cells 11 together.

[0045] Each of the first and second connection lines is provided with a control circuit between the battery management controller and each of the junctions to which the connection line extends. The control circuits in the embodiment shown are provided on each of the connection boards 56. The battery management controller is also provided with a voltage generator provided to generate a particular voltage level to be provided on the connection line to the control circuits.

[0046] Each of the control circuits is provided to connect between the first or second connection line and one of the junctions where the voltage at that junction is within a voltage range of the voltage generated by the voltage generator. The voltage range is chosen to be around or below half a cell voltage. As the cells 11 are connected in series within each column, the voltage at each junction will be the voltage at the previous junction plus the current voltage of the cell 11 . The voltages at each junction will therefore be different and the battery management system can selectively connect to any one cell 11 or a set of cells 11 by selectively connecting the first and second connectionlines to the junctions on either side of that cell 11 or on either side of that set of cells 11.

[0047] Figure 6 shows examples of a pair of control circuits provided between each of the first and second connection lines and junctions between adjacent pairs of cells 11 . The circuit shows emitter coupled transistors that detect the differential voltage between a multiplexing line and its connection to a cell junction. When the voltage exceeds the chosen allowed voltage range, the transistors are turned on, ensuring a positive voltage step on the series capacitor resistor from the signal marked ON cannot activate the source coupled MOSFETs via their gates.

[0048] When the voltage of the cell junction is proximate to associated multiplexing line voltage the emitter coupled transistors are disabled so that a positive step, in this case of 10V on the line marked ON turns the MOSFETs hard on.

[0049] The line marked “Enable”, is set to 0V for a complete zero power shutdown or the positive rail or above to enable the system.

[0050] The collector emitter resistor is a high value, chosen to be low enough to prevent the MOSFETs being turned on by leakage currents and high enough that the series capacitor does not discharge in the period a cell junction is to be connected for charging or discharging.

[0051] The two series connected reverse junction emitter base junction are chosen to give a 10V clamp with very little leakage current. These forward bias, recharging the series capacitor when the ON signal is low.

[0052] The voltage splitters to the bases of the transistors are chosen to set the differential voltage between multiplexing line and cell junction that disables the MOSFETs from being turned ON.

[0053] The series capacitor is chosen to be small enough so that protection is provided against persistent excess current flowing through the MOSFETs where cross connection occurs. Cross connection with two cell junctionsconnecting to the same multiplexing line can initially occur where the chosen voltage is within range of the two junctions. This quickly resolves as either both series capacitor are discharged or one discharges first, causing the other to drive the multiplexing line to the cell voltage. When an even such as this is detected, the controlling means should reset the multiplexing line voltage and try again, to avoid a situation where the MOSFETs may not be fully turned ONThe circuit with features commensurate with the above may be mass produced as an ASIC.

[0054] The first and second connection lines may not connect to every junction within a column of cells 11 . For example, the first connection line and second connection line may connect to alternate junctions within the column. This will allow only connection across odd numbers of cells 11 within the column and not across even numbers of cells 11 but it is expected that the reduced connections therefore required would outweigh the disadvantages of not being able to connect to any number of cells 11 .

[0055] The battery management system includes also memory provided to store the voltages of each cell 11 within a column based on the voltages determined at each junction. In this case, the means is a switching regulator that can drive to a voltage and then isolate, turning of both +ve and -ve PWM generating switching devices. At start up, the voltage generator may generate increasing voltage levels, isolating and attempting to connect to a cell junction repeatedly until the first connection line connects to one of the junctions. This first connection will be to the first junction in the column and the voltage of the first cell may therefore be stored in memory. The process may be repeated by increasing the generated voltage to connect to the second junction to determine the voltage at this junction and therefore across the second cell in the column.

[0056] Once voltages of each cell 11 within a column are known and stored, these levels can be used to generate voltages on the first and second connection lines to connect to particular junctions, and therefore across individual cells or sets of cells 11 as required. The generated voltages may beadjusted based on charging or discharging information available during operation since the connection lines were last connected to a cell 11 .

[0057] The energy storage system thereby includes an arrangement where cells can be individually monitoring and controlled by direct connection across the cells without the need for additional connections and / or cell addressing.

[0058] It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention.

Claims

Claims1 . An energy storage system comprising: a housing having a plurality of cells arranged in a series, each cell having terminals at opposite ends such that adjacent terminals of the cells connect at one or more cell junctions within the series of cells; a battery management system provided for monitoring voltages of the cells and controlling current flow in and out of the cells; a first connection line extending from a battery management controller of the battery management system to cell junctions within the series of cells; a second connection line extending from the battery management controller of the battery management system to cell junctions within the series of cells; a voltage generator provided to generate a first voltage on the first connection line and a second voltage on the second connection line; and a control circuit provided between each of the first and second connection lines and each of the junctions to which the connection line is connected; wherein when the first and second voltages are generated on the first and second connection lines, the control circuits will connect between the first connection line and a first cell junction where the voltage at said first cell junction is within a voltage range of the first voltage and will connect between the second connection line and a second cell junction where the voltage at said second cell junction is within a voltage range of the second voltage.

2. An energy storage system in accordance with claim 1 , wherein the first and second connection lines may connect across a single cell within the series of cells or a set of cells within the series.

3. An energy storage system in accordance with claim 1 or 2, wherein the first and second connection lines are connected to alternate junctions within the series of cells.

4. An energy storage system in accordance with any one of claims 1 to 3, wherein the cells are connected in a column contained within a tubular member.

5. An energy storage system in accordance with claim 4, wherein each column includes two or more columns of cells.

6. An energy storage system in accordance with any one of the preceding claims, wherein the first and second connection lines extend to connection boards provided in the column between adjacent pairs of cells, the connection boards including tabs extending outwardly to connect to the junctions between adjacent cells. . An energy storage system in accordance with claim 6, wherein the control circuits are provided on the connection boards.

8. An energy storage system in accordance with claim 4 or 5, wherein the tubular members mounted to a base frame.

9. An energy storage system in accordance with any one of claims 4 to 8, wherein an upper frame is provided connected to upper ends of the tubular members, the upper frame including the battery management system.

10. An energy storage system in accordance with any one of claims 6 to 9, wherein each of the connection boards is oriented parallel to a longitudinal axis of the tubular member and includes first tabs extending outwardly from a first side thereof to connect to electrical contacts on an adjacent pair of cells from the first column and second tabs extending outwardly from a second side of each of the connection boards to connect to electrical contacts on an adjacent pair of cells from the second column.

11. An energy storage system in accordance with claim 10, wherein each of the tubular members includes first and second side walls being parallel and planar first and second end walls each being arcuate in transverse cross section.

12. An energy storage system in accordance with claim 11 , wherein the tubular members are obround in transverse cross-section such that a first column of cells is received adjacent the first end wall and a second column of cells is received adjacent the second end wall.

13. An energy storage system in accordance with claim 12, wherein each of the tubular members includes first and second guide rails extending longitudinally down inner surfaces of the first and second side walls, each of the first and second guide rails including a channel to receive an edge of the connection boards.

14. An energy storage system in accordance with claim 13, wherein each of the guide rails includes a longitudinal groove which receives in use a corresponding rib extending along an inner surface of the first and second side walls of the tubular member.

15. An energy storage system in accordance with any one of the preceding claims, wherein the tubular members are provided in a generally rectangular array.

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