GB2561209A

GB2561209A - Cooling system and method

Info

Publication number: GB2561209A
Application number: GB1705509.6A
Authority: GB
Inventors: Berge Tore; Børsheim Eirik; Skjetne Arve; Eliassen Sivert; Holen Roy
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2017-04-05
Filing date: 2017-04-05
Publication date: 2018-10-10
Also published as: GB201705509D0

Abstract

An energy storage module cooling system for an energy storage system comprising at least one energy storage module 14, or at least one cubicle 26a, 26b, 26c, 26d housing at least one energy storage module comprises a source 10 of cooling fluid, a plurality of fluid conduits 12, 16, 20 for supplying cooling fluid to the or each stored energy module or cubicle, each fluid conduit 20 entering each module or cubicle being provided with a flow control valve 21, 28 and one or more sensors 10 19 associated with each valve and module, or cubicle. A signal from each sensor to a controller 18 controls the degree of opening of each valve 21, 28 to control the amount of cooling fluid provided to each module, or cubicle.

Description

(54) Title of the Invention: Cooling system and method

Abstract Title: An energy storage module (battery) cooling system having fluid flow valve controllers (57) An energy storage module cooling system for an energy storage system comprising at least one energy storage module 14, or at least one cubicle 26a, 26b, 26c, 26d housing at least one energy storage module comprises a source 10 of cooling fluid, a plurality of fluid conduits 12, 16, 20 for supplying cooling fluid to the or each stored energy module or cubicle, each fluid conduit 20 entering each module or cubicle being provided with a flow control valve 21, 28 and one or more sensors 10 19 associated with each valve and module, or cubicle. A signal from each sensor to a controller 18 controls the degree of opening of each valve 21,28 to control the amount of cooling fluid provided to each module, or cubicle.

FIG 2

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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FIG 3

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FIG 4

COOLING SYSTEM AND METHOD

This invention relates to a cooling system and method for a stored energy module, in particular for an electrochemical cell, or battery, providing electrical energy to an end user.

Stored electrical energy modules, or stored power units of various types are becoming increasingly common in many applications, in particular for use where there are environmental concerns relating to emissions in sensitive environments, or public health concerns. Stored electrical energy power units are typically used to provide electrical energy to operate equipment, to avoid emissions at the point of use, although that stored energy may have been generated in many different ways. Stored electrical energy may also be used to provide peak shaving in systems otherwise supplied from the grid, or from various types of power generation system, including diesel generators, gas turbines, or renewable energy sources. Aircraft, vehicles, vessels, offshore rigs, or rigs and other powered equipment in remote locations are examples of users of large scale stored electrical energy. Vehicle drivers may use the stored energy power unit in city centres and charge from an internal combustion engine on trunk roads, to reduce the harmful emissions in the towns and cities, or they may charge up from an electricity supply. Ferries which carry out most of their voyage relatively close to inhabited areas, or in sensitive environments are being designed with hybrid, or fully electric drive systems. Ferries may operate with stored energy to power the vessel when close to shore, using diesel generators offshore to recharge the batteries. In many Scandinavian countries the availability of electricity from renewable energy sources to use to charge the stored energy unit means that a fully electric vessel may be used, provided that the stored energy units are sufficiently reliable for the distances being covered, with no diesel, or other non-renewable energy source used at all. Whether hybrid, or fully electric, the stored energy units may be charged from a shore supply when docked. The development of technology to achieve stored energy units that are reliable enough for prolonged use as the primary power source must address certain technical issues.

In accordance with a first aspect of the present invention, an energy storage module cooling system for an energy storage system comprising at least one energy storage module, or at least one cubicle housing at least one energy storage module, the cooling system comprising a source of cooling fluid; a plurality of fluid conduits for supplying cooling fluid to the or each energy storage module or cubicle, each fluid conduit entering each module or cubicle further comprising a flow control valve and one or more sensors associated with each valve and module, or cubicle; wherein a signal from each sensor to a controller controls the degree of opening of each valve to control the amount of cooling fluid provided to each module, or cubicle.

Although, each valve may be provided with a local controller, preferably the controller comprises a central controller, remote from the valves.

This allows coordination of cooling amongst the energy storage modules, or cubicles.

The one or more sensors may comprises temperature sensors or flow sensors.

The system may further comprise a temperature sensor in each fluid outlet conduit.

This allows an increase in temperature within a module or cubicle to be detected, even if communication between a controller in that module or cubicle and the central controller is lost.

The system may further comprise a store, for storing a sensor reference value for each module.

The system may further comprise a frequency converter on the pump supply to reduce or increase the total flow rate in the system.

In accordance with a second aspect of the present invention, a method of controlling cooling of a stored energy module system comprises receiving sensor data from sensors in a cubicle or module of the stored energy module system; comparing the sensor data with a reference value to obtain a difference value; determining whether the difference value falls outside a tolerance range; if the difference value falls outside the tolerance range, adjusting one or more flow control valves associated with the stored energy modules, or cubicles to increase or decrease the flow of cooling fluid to each, based on the difference value.

The adjusting may comprise increasing cooling fluid flow to one or more stored energy modules, or cubicles, by increasing opening of the valve associated with that module, or cubicle, and reducing opening of the valve associated with other modules or cubicles, in the system.

If the majority, or all of the modules or cubicles are at the lower end of their desired temperature range, requiring a reduction in overall cooling, the method may further comprise diverting cooling fluid away from the stored energy modules, or cubicles, on a bypass path.

If the condition persists, the central controller may stop pumping cooling fluid for a period.

The comparison of the sensor data and reference value and the adjustment of the valves may be carried out under the control of a central controller

Receiving the sensor data may comprise receiving data from a temperature sensor.

The method may further comprise reducing the flow rate, or volume of fluid pumped from the cooling system, if all modules, or cubicles, require a reduction in cooling effect.

The method may further comprise increasing the flow rate, or volume of fluid pumped from the cooling system, if all modules, or cubicles, require an increase in cooling effect.

An example of cooling system and method according to the present invention will now be described with reference to the accompany drawings in which:

Figure 1 illustrates a battery cooling system;

Figure 2 illustrates one embodiment of a cooling system according to the present invention for a modular stored energy system;

Figure 3 illustrates an alternative embodiment of a cooling system according to the present invention for a modular stored energy system; and,

Figure 4 is a flow diagram of a method of operation of a cooling system according to the invention.

Early large scale batteries were lead acid, but more recently, lithium ion batteries have been developed for electrical energy storage for large scale applications. Li-ion batteries are typically pressurised and the electrolyte is flammable, so they require care in use and storage. A problem which may occur with Li-ion batteries is thermal runaway, which may be caused by an internal short circuit in a battery cell, created during manufacture. Other causes, such as mechanical damage, overcharge, or uncontrolled current may also cause thermal runaway, but the battery system design is typically adapted to avoid these. Manufacturing issues with the cells cannot be ruled out entirely, so precautions are required to minimise the effect should thermal runaway occur. In a large scale Li-ion battery system, the amount of energy that is released during a thermal runaway is a challenge to contain. A thermal event may increase temperatures in a single cell from a standard operating temperature in the range of 20°C to 26 °C to as much as 700°C to 1000°C. Safe operating temperatures are below 60 °C, so this is a significant problem.

There are strict regulations in the marine and offshore industries regarding risk to the vessel or rig, one requirement being that there should be no transfer of excess temperature from one cell to another. If overheating occurs, then it should be contained in a single cell and not allowed to spread. In addition, for marine and offshore applications, weight and volume of any equipment is severely restricted, leading to compact, lightweight systems being preferred. It is a challenge to produce a compact, lightweight, system that achieves the required thermal isolation and cools the cell in which excess heating occurs, quickly and efficiently. Another problem is that in a thermal event there may also be release of a large amount of flammable gasses, which may self-ignite at elevated temperatures

The problem may be addressed by allowing whole modules to enter thermal runaway and simply control the resulting flames and fire with an external fire extinguishing system. In this case there are open flames in the battery space and controlling the resulting flames and fire does not ensure safe transportation and storage. Alternatively, potentially expensive insulation material may be used to thermally isolate the cells from one another, but this compromises cooling system performance and adds volume. A conventional approach is to use thick aluminium fins between each cell to provide the cooling, but this adds weight and volume and still does not ensure safe transportation and storage because heat is conducted extremely well through aluminium (>300 W/mK) and will heat neighbouring cells quickly, if not cooled. During transport and storage, cooling may not be available. The problem of release of flammable gas may be handled by providing a pressure valve in the module casing, releasing the gas at a certain pressure, either into the battery space or into a separate exhaust system. However, conventional pressure release valves are designed to burst under pressure, which leads to other problems. In addition, active cooling may be provided in the exhaust outside the module to avoid self-ignition.

In a Li-ion battery system, it is very important that the temperature of the battery cells does not exceed the prescribed operating temperature and that the cell temperature in the entire system is uniform. Sustained operation outside the prescribed operating temperature window may severely affect the lifetime of the battery cells and increases the risk of thermal runaway occurring. The present invention addresses the problem of preventing thermal runaway spreading to other cells, should it occur in one cell, as well as helping to increase the operating lifetime of a cell. The invention may also be used for long-term regulation of the flow through the modules to ensure even temperature distribution throughout the system. Having the facility to temporarily increase the cooling performance reduces the negative consequences of operation outside the prescribed temperature window. Conventionally, any cooling steps applied to battery operation have been of a fixed nature and no attempt has been made to control the cooling performance during operation.

Other types of stored energy units, such as capacitors, supercapacitors and fuel cells may also suffer if the temperature of modules of the stored energy units regularly goes outside a preferred operating range, reducing the overall lifetime and increasing maintenance costs. For a vessel, or system, relying on stored energy as its primary, or only power source, reliability is particularly important and optimising operating conditions is desirable. The detailed examples given are for batteries, or electrochemical cells, but the principle of the invention is applicable to other types of energy storage unit.

In the example of Fig. 1, a battery cooling system 1 is shown which provides a flow of cold water in pipes 2 in the direction of arrows 3 to a plurality of battery modules 4 in an energy storage system. The flow of cold water may go in parallel to each battery 4 of a group 5 of batteries, or to more than one group 5 of batteries 4, dependent on the layout of the system. Separate pipes 6 carry away, in the direction of arrows 7, the warm water that has been heated up by heat exchange in each of the battery modules and then returns this warm water to the cooling system 1, where the water is cooled again. Thus, the cooling system 1 provides a flow of water around a circuit via pipes 2, 6 passing into and out of each battery module 4. Substantially the same amount and flow of water is provided to and removed from each battery module by virtue of the arrangement of the pipes.

An example of a battery cooling system according to the present invention is shown in Fig.2. This shows a system comprising a plurality of energy storage modules.

One or more energy storage modules may be mounted in a cubicle 26. Each energy storage module is electrically connected in series with its neighbour and typically comprises a stack of energy storage devices, for example battery cells, also electrically connected in series. A single cell may have a capacity between 20Ah and 100 Ah, more commonly between 60Ah and 80 Ah, although cells with a capacity as low as a couple of Ah, or over 100 Ah, may be used. In one example, there may be up to thirty cells (not shown) per module 14 and up to nine modules per cubicle 26. Multiple cubicles 26 may be installed on a vessel, or platform, or other installation.

In the energy storage system, cooling fluid, which, for example, may be cold water, or a water glycol mixture is pumped as shown by arrows 13 from an outlet 24 of a cooling system 10 via conduits, such as pipes, or tubes 12, for example stainless steel tube, or plastic pipes, to stored energy modules 14, for example electrochemical cells, fuel cells, capacitors, or other energy storage for which it is important to achieve even temperature distribution throughout the system. The stored energy modules 14 may be arranged to receive the cooling fluid in parallel and separate groups 15 of modules 14 may be fed with cooling fluid in parallel. Each module has its own input cooling pipe 20 and in this pipe, a control valve 21 is provided for each module 14. The valve is typically a remote controlled valve and the cooling system 10 includes a controller 18 which receives signals from one or more sensors 19, such as a temperature sensor, in each module, indicating the temperature of the module. Use of multiple sensors provides redundancy.

An additional feature is that a temperatures sensor may be provided at a cooling fluid outlet 25 from each module, the temperature of the cooling fluid at the outlet giving an indication of whether that particular module is at a higher than expected temperature, so transferring more heat to the cooling fluid as it passes through. From this, it can be implied that there may be a thermal event in a single cell within the module. This sensor allows that information to be obtained even if communication with that module is prevented, such as a fault in the module CPU, or electrical interference in the communication between the module 14 and the controller 18. The controller 18 then adjusts the cooling flow or volume through the valves 21 accordingly, to direct more flow to the module with the potential thermal event. Each outlet 25 feeds into return pipe 16. If required, a temperature sensor in the fluid at the outlet of each cubicle may be provided. Another option is to use flow sensors to measure and compare flow of cooling fluid in the modules with regulation of the control valve based on flow differences. A combination of flow and temperature measurements may be used, although this adds costs, as compared with using only a single sensor type.

In the example shown in Fig.2, the controller 18 takes the sensor data, in this case received detected temperature of the module, or fluid outlet and compares this with a stored reference value, either common to all battery modules, or cubicles, or specific to each. If the difference between the detected value and stored reference value exceeds a certain amount, e.g. showing the detected temperature to be more than 10% above or below the reference value, then the controller checks the results for all the other battery modules, or cubicles and adapts the amount of valve opening of each in order that the total available cooling liquid flow is better distributed amongst the battery modules, or cubicles. For example if all except one have a detected temperature close to the expected reference value, then the amount of cooling liquid to those modules, or cubicles, may be reduced by a certain amount and the cumulative cooling water flow that reduction represents is redirected to the one module which has too high a temperature.

Fig.3 illustrates an example in which the cooling flow control may be performed on a cubicle level 26, in which case one valve 28 controls the flow of cooling fluid to all of the modules 14 located in the same cubicle 26a, 26b, 26c, 26d as opposed to a valve for each module as illustrated in Fig.2. If there are many cubicles, there may be a pressure drop along the main pipes 27 between the first cubicle 26a and the last cubicle 26d in which case the valve 28 may comprise a controllable valve to ensure all cubicles have the same flow.

An alternative is to use the local sensor 19 to sense temperature, or other indication of heat, in combination with a local comparator (not shown) to compare the sensor value with a stored value and a local controller to control the valve opening for each stored energy module 14 and its associated valve 21. Using a local controller allows the degree of valve opening to be adapted according to the output of the comparator, but without coordination of all the valves of all the stored energy modules, as is possible with a central controller 18.

A further modification is to add a return line 22 of cooling fluid to the cooling system, so that if all the stored energy modules are detected as being at the lower end of their preferred operating temperature, then all of the valves 21 may be closed a little more to reduce cooling and the excess cooling fluid is returned to the cooling system via a short circuit 22 between the cold fluid outlet 24 and the warm fluid line 16 to mix with the warmed fluid, starting the re-cooling process, rather than distributing the cooling fluid amongst all the modules, so cooling them further, which may have an impact on performance. Typically, a remotely controlled valve 23 is provided in this return line 22 to control whether or not cold fluid is returned and the proportion of cold fluid returned. If necessary, the controller may subsequently reduce the flow rate or volume of fluid pumped from the cooling system to reduce the cooling effect further, or even stop pumping cooling fluid entirely for a period, until the temperature sensors indicate that cooling is required again. Similarly, the controller may increase the flow rate or volume of fluid pumped from the cooling system if all the sensor values indicate that all the modules are at the upper end of their allowable temperature range and more cooling is required for them all. A reduction, or increase, in flow rate from the cooling system may be achieved by using a frequency converter on the pump supply to reduce or increase the total flow rate in the system, thereby optimising the energy used by the pump by not pumping more water than necessary. The heat losses from the systems vary depending on whether the cells are charged or discharged. Although the cooling system is designed to cope with the highest losses expected, a frequency converter is an effective way of dealing with operation during times when the losses are lower.

By contrast with the battery cooling system, instead of simply pumping the same fixed amount of water to each of the battery modules, the remote controlled valves 21, 28 may be controlled to adapt to the specific requirements of each stored energy module 14, or cubicle either locally operated, or by a central controller 18 sending a signal to open or close each valve based upon detected temperature levels for each battery module. The individually controlled valves 21 on each module allow an increase or reduction of the cooling fluid flow in each module to be achieved, for example, if a temperature sensor detects that one particular module is at a significantly different temperature to the others. This may be by flow through one or more of the other valves being reduced or cut off by the controller, directing all or most of the cold water to an overheating stored energy module, or by re-circulating, or reducing cooling fluid flow, if the modules become too cold.

Fig.4 is a flow diagram showing a typical method of controlling cooling of a stored energy system. Each of the stored energy modules has sensors which provide condition data, typically one temperature sensor per cell of the module 14. Sensor data is received 30 from each stored energy module in the system and compared 31 with a reference value to produce a difference value. The reference value is typically the same for all the stored energy modules, but if they have different characteristics, the reference may be set to be module specific. The determined difference value (which may be zero, if the actual temperature and reference temperature are the same) is then checked 32 to determine whether it is within a permissible tolerance. The tolerance may be expressed as a percentage, or absolute value. If the difference value falls outside the tolerance 33, more or less cooling is required to bring it back into the tolerance limits. If the difference value is within the tolerance 34, the current level of cooling is assumed to be acceptable. In a system with a central controller 18 providing remote control of all the valves 21, 28, the controller then coordinates the results of steps 32 to 34 for all the energy storage modules in the system and controls 35 the degree of valve opening for each valve as required. In some cases, that may mean no change is made, in others, there may be an increase or decrease in the degree of opening of some or all of the valves to achieve additional cooling for specific modules, or specific cubicles where cooling is controlled on a per cubicle basis. The sensing and comparison steps may be repeated 36 at set intervals, or there may be continuous monitoring and change initiated in response to one sensor indicating an out of tolerance result.

A substantial change in the fluid flow to an affected module, or cubicle, is made possible by changing the flow to the other modules, or cubicles with the advantage that a more precise control of each module or cubicle’s temperature is made possible using the individually controlled valves 21, 28 to control the module flow rate. This ensures that the user is able to operate the energy storage system within an optimal temperature window, as well as reducing the possibility that, for an electrochemical cell, a thermal event in a module will develop into a thermal runaway.

The controlled cooling system described protects the energy storage device whilst it is in operation, but with suitable adaptation, this type of cooling system may be used to protect the energy storage devices throughout their lifecycle process, from initial construction through transport and installation, as well as when in operation, to protect against the consequences of faults occurring.

Claims

1. An energy storage module cooling system for an energy storage system comprising at least one energy storage module, or at least one cubicle housing at least one energy storage module, the cooling system comprising a source of cooling fluid; a plurality of fluid conduits for supplying cooling fluid to the or each energy storage module or cubicle, each fluid conduit entering each module or cubicle further comprising a flow control valve and one or more sensors associated with each valve and module, or cubicle; wherein a signal from each sensor to a controller controls the degree of opening of each valve to control the amount of cooling fluid provided to each module, or cubicle.

2. A cooling system according to claim 1, wherein the controller comprises a central controller, remote from the valves.

3. A cooling system according to claim 1 or claim 2, wherein the sensor comprises a temperature sensor or a flow sensor

4. A cooling system according to any preceding claim, wherein the system further comprises a temperature sensor in each fluid outlet conduit.

5. A cooling system according to any preceding claim, wherein the system further comprises a store, for storing a sensor reference value for each module.

6. A cooling system according to any preceding claim, wherein the system further comprises a frequency converter on the pump supply to reduce or increase the total flow rate in the system.

7. A method of controlling cooling of a stored energy module system, the method comprising receiving sensor data from sensors in a cubicle or module of the stored energy module system; comparing the sensor data with a reference value to obtain a difference value; determining whether the difference value falls outside a tolerance range; if the difference value falls outside the tolerance range, adjusting one or more flow control valves associated with the stored energy modules, or cubicles to increase or decrease the flow of cooling fluid to each, based on the difference value.

8. A method according to claim 7, wherein the adjusting comprises increasing 5 cooling fluid flow to one or more stored energy modules, or cubicles, by increasing opening of the valve associated with that module, or cubicle, and reducing opening of the valve associated with other modules or cubicles, in the system.

9. A method according to claim 7 or claim 8, wherein the method further

10 comprises diverting cooling fluid away from the stored energy modules, or cubicles, on a bypass path.

10. A method according to any of claims 7 to 9, wherein the comparison of the sensor data and reference value and the adjustment of the valves are carried out under

15 the control of a central controller

11. A method according to any of claims 7 to 10, wherein receiving the sensor data comprises receiving data from a temperature sensor.

20

12. A method according to any of claims 7 to 11, wherein the method further comprises reducing the flow rate, or volume of fluid pumped from the cooling system, if all modules, or cubicles, require a reduction in cooling effect.

13. A method according to any of claims 7 to 12, wherein the method further

25 comprises increasing the flow rate, or volume of fluid pumped from the cooling system, if all modules, or cubicles, require an increase in cooling effect.

Intellectual

Property

Office

Application No: GB1705509.6 Examiner: Dr Lyndon Ellis