GB2561212A

GB2561212A - Housing

Info

Publication number: GB2561212A
Application number: GB1705523.7A
Authority: GB
Inventors: Børsheim Eirik
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: GB201705523D0

Abstract

An energy storage module housing 50 comprises a perimeter wall, a neck 71 and an opening 57 in the neck of the perimeter wall to allow escape of gases from the module. The opening 57 further comprises a closure member 51. The closure member may include a resilient member 58 to hold the closure member against the housing and further, the closure member may be heat resistant. Also claimed is an energy storage system comprising an exhaust channel, the channel comprising two or more mounting openings each of which includes a closure member and a resilient member adapted to hold the closure member against the wall of the opening (Fig 7B)

Description

(54) Title of the Invention: Housing

Abstract Title: Energy storage module (battery) housing having a vent (57) An energy storage module housing 50 comprises a perimeter wall, a neck 71 and an opening 57 in the neck of the perimeter wall to allow escape of gases from the module. The opening 57 further comprises a closure member 51. The closure member may include a resilient member 58 to hold the closure member against the housing and further, the closure member may be heat resistant. Also claimed is an energy storage system comprising an exhaust channel, the channel comprising two or more mounting openings each of which includes a closure member and a resilient member adapted to hold the closure member against the wall of the opening (Fig 7B)

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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HOUSING

This invention relates to an energy storage module housing for an energy storage module, in particular for an electrochemical cell, or battery, providing electrical energy to an end user.

Stored electrical energy modules, or 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 some 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 housing, the housing comprising a perimeter wall, a neck and an opening in the neck of the perimeter wall to allow escape of gases from the module; wherein the opening further comprises a closure member.

The closure member may comprise a resilient closure member fitted to the opening, which flexes in response to pressure of gas within the housing, to allow escape of gas, but preferably the closure member comprises a rigid closure member and a resilient member adapted to hold the closure member against the wall of the opening.

The closure member may comprise a heat resistant plate.

The resilient member may be pivotally mounted to a lower extension of the perimeter neck; and adapted to rest its end remote from the pivot on an upper extension of the perimeter neck.

In accordance with a second aspect of the present invention, an energy storage system comprises an exhaust channel, the channel comprising two or more mounting openings, each mounting opening comprising a closure member and a resilient member adapted to hold the closure member against the wall of the opening.

The closure member may be adapted to open to allow a neck of a module housing perimeter wall to be mounted to the exhaust channel.

The system may further comprise a mounting rack to support each energy storage module, the mounting rack located adjacent the exhaust channel.

The system may further comprise one or more energy storage module housings according to the first aspect, each mounted in a mounting opening.

An example of an energy storage module housing according to the present invention will now be described with reference to the accompany drawings in which:

Figure 1 is a block diagram of an example of a cooling system for a modular stored energy system;

Figures 2a and 2b illustrate more detail of a carrier for energy storage devices using the cooling system according of Fig.l;

Figures 3a and 3b show more detail of coolers which may be used in the examples of Figs. 1 and 2;

Figure 4 illustrates how multiple energy storage device carriers may be stacked together to form a module for use with the housing of the present invention;

Figure 5 shows more detail of part of the stack of Fig.4;

Figures 6a and 6b illustrate one example of a housing according to the present invention with a non-return valve for a module of an energy storage system;

Figures 7a and7b illustrate an exhaust channel and mounting arrangement for module housings according to the present invention; and,

Figures 8a and 8b illustrate an alternative example of a closure for a housing according to the present 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 controlling 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.

For marine applications, there is a particular focus on using energy storage modules, such as batteries, at their maximum charge or discharge rate due to cost of installation and the weight and space taken up by the modules when on a vessel or offshore platform. Furthermore, maintenance and repair, or replacement is complicated and expensive compared to land based uses of stored energy systems, so extending the lifespan of stored energy modules is particularly important. For the example of Li- ion batteries, these are sensitive to high temperature, so it is important to ensure that the operating and ambient temperature are control for all cells of a Li-ion battery system to ensure the design lifetime is met. Local variations or hot spots on a single cell may also compromise the total lifetime achievable.

A common approach for large scale, marine, or offshore, stored energy systems is to use air cooling, with air flowing between cells of a battery system. Another option is to use water cooling in combination with aluminium cooling fins. The water cooling is by flowing over heat exchangers and cooler blocks and the aluminium cooling fins are provided between each cell of the battery system. However, this system is not particularly efficient at removing heat and also adds substantial weight to the energy storage system. Aluminium is chosen for its thermal conductivity and relatively low cost, rather than its lightness. Heat from the batteries must pass to the aluminium cooling fins and those fins are then cooled by the liquid which loses its heat at the heat exchanger and is recirculated.

These systems may be acceptable for normal operation, but are unable to respond to sudden temperature increases, such as may occur during thermal runaway.

Fig. 1 illustrates an example of a stored energy module cooling system for cooling energy storage modules. An energy storage module 4 typically comprises an energy storage device, in this example, a battery cell (not shown) electrically connected together in series with a neighbouring energy storage device in the next carrier. The cells are preferably prismatic or pouch type cells to get a good packing density. Typically, a single cell has a capacity of between 20 Ah and lOOAh, 60Ah to 80Ah being most common, but capacities of only a few Ah or above 100 Ah are not excluded. The energy storage modules 4 are also electrically connected together in series. A plurality of energy storage modules are combined to form an energy storage unit 2, or cubicle. A cooling unit 1 provides a cooling fluid to the modules 4 of the energy storage unit 2 via inlet pipes 3. In this example, the energy storage unit comprises a plurality of modules 4, each module supplied in parallel with cooling fluid through inlet tubes 5. The warmed cooling fluid is removed through outlet tubes 6 and returned to the cooling unit 1 via outlet pipes 7. Typically, the warmed fluid is cooled again in the cooling unit and re-circulated in a closed system.

Figs.2a and 2b show more detail of the modules 4. Each module comprises a cell carrier, or casing 20, as shown in Fig.2a, into which an energy storage device (not shown), such as a battery cell, is fitted. The carrier is typically made from a polymer plastics material for light weight and low cost. As shown in Fig.2b, a cooler 22 may be formed by additive manufacturing techniques, or may be formed by laminating, or welding, a plate 21 alongside a series of raised sections 23 formed, typically by moulding, in another piece of the same polymer plastics material to form closed channels, or conduits, through which cooling fluid may flow from one end to another.

A battery cell may be installed in each carrier 20, for example on outer surface 27 of the cooler. The outer surface of the cooler 22 may be in direct contact with one surface of the battery cell to provide effective cooling over a large surface area, without any direct contact of the cooling fluid to the energy storage device, or cell.

Cooling fluid flows from the inlet pipe 3 through the channels, or conduits 23 of the cooler 22, cooling the cell by thermal transfer from the surface of the cell through the thin tubing 23 to the cooling fluid. The cooling fluid channels or tubing have a typical overall thickness in the range of 5mm to 20mm, with a wall thickness in the range of 1mm to 5mm and preferably, no more than 3mm for a polymer plastics material. The cooling fluid is carried away into the outlet pipe 7 and returned to the cooling unit 1 to be cooled again. The tubing 23 formed under plate 21 covers a substantial part of the cell surface on the side that it contacts, anything from 30% to 75% of the cell surface area on that side of the cell.

The overall design has a significantly reduced total material weight and cost by using the cooling liquid pipes to flow cooling fluid directly adjacent to the cell surface, instead of conventional cooler block, heat exchanger designs. In addition, this cooling is provided for normal operation, to keep the cell within a temperature range that is beneficial to performance and operational lifetime, rather than as a one off, only in the case of a thermal event. The water channels 23 may be formed in any suitable form, connected between the inlet and outlet pipes 3, 7 via the tubes 5, 6. Preferably, the cross section of the channels is square to maximise the contact and minimise the amount of plastics material between the cooling fluid and the energy storage device. However, other cross sections could be used, such as circular cross section tubing. The tubing 23 may be in the form of a continuous serpentine 11 connected between the inlet and outlet tubes 5, 6, as shown in Fig. 3a and the example of Fig.2b, or there may be multiple parallel rows 12 of tubing fed by a common supply from the inlet pipe 3 connected to the inlet tube 5 and exiting through outlet tube 6, as shown in Fig.3b, to outlet pipe 7.

The tubing 23 may be metal, but more typically is a synthetic material, such as polymer plastics, for example polythene, polyamide, such as PA66 plastics, or thermoplastics such as TCE2, TCE5, or other suitable materials, which may be moulded or extruded to the required shape and is able to withstand normal operating temperatures of the energy storage modules. The cell is cooled directly by flowing cooling fluid on a substantial part of the cell surface, with very little thermal resistance. Conventional cooling arrangements have suffered from hot spots for areas of the cell which were far away from the cooler block, or heat exchanger, but this laminated cooler and cell module avoids this problem. This has the effect of slowing down the aging process of the cell, so increasing its lifetime.

Multiple energy storage modules 4, each provided with an integral cooler 22, are formed from the cells stacked together in their carriers 20, as shown in Fig.4. Cooling fluid enters the tubes of each cooler from an opening 70 in the common inlet pipe 3 that runs along the stack and exits through an opening 71 in the common outlet pipe 7 that runs along the stack. In a closed system, the cooling fluid is pressurised and circulates around the stack of modules via the common pipes 3,7 and individual coolers 22 of each module 4.

The common inlet pipe 3 and common outlet pipe 7 of the stack are formed with pipe connections, illustrated as washers 30, 31, between each adjacent carrier of the stack. The washers 29, 30 of the inlet pipe 3 comprise a flame retardant material, which may be chosen to be effective up to at least 400°C for at least 10s, preferably up to 500°C, so in the event of thermal runaway and ignition of a cell, the washers remain intact, ensuring that cooling water continues to be supplied from the cooling unit 1, along the inlet pipe. However, optionally, the washers 28, 31 of the outlet pipe 7 on the outlet side may be made from a material that melts at a relatively low temperature when subjected to heat or flames, the temperature being above the safe operating temperature of the cells, i.e. above 60 °C, but typically in the range of 130 °C to 180 °C and preferably below 150°C. In normal operation, the pipe connections 30, 31 at the inflow and outflow side are both intact, so the cooling fluid flows in parallel through all of the coolers of all of the cells at an equal flow rate, or equal volume. There may be a pressure difference between points 30 and 31 due to the flow through the cooling channels. In this example, the pressure of the closed system is set to be above ambient pressure.

However, if the pipe connection 31 on one of the outflows fails, for example, when the pipe connection melts due to thermal runaway occurring, then the now much lower pressure where that connection has failed makes that the path of least resistance and all of the water flow tries to go towards that opening, rather than being shared amongst all the coolers of all the cells. The consequence of this is that, for a short time, until the no longer closed system runs out of water, a very substantial volume of water is provided through the cooler of that cell in a relatively short time, taking more heat away more quickly than in standard operation. Unlike the prior art systems referenced above, the design of Figs. 1 to 5 retains the benefit of cooling the cell surface by close contact of the cooling channels to the cell surface, even when a pipe connection fails.

Thus, the substantial increase in heat removal is applied over the whole of the cell surface, rather than limited parts close to the supply. Furthermore, a pipe connection between cell carriers may be replaced once the fire has been brought under control, allowing the battery stack to be put back into operation more quickly. Generally, it is more efficient for the module to be removed for maintenance and replaced with a complete new one initially, even if the pipe connections are subsequently replaced in the removed module. The design keeps the advantage that the cooler 22 in each module transfers developed heat directly to the cooling liquid through the whole cell surface, on at least one side of the cell, whilst allowing for a short term, but substantial increase in cooling if required. The developed heat is transferred directly to the cooling liquid through the whole cell surface giving very effective cooling, reducing the temperature difference between cell and coolant. The design ensures flowing water in the coolers in the event that a given point of the system is opened up, as there is a certain pressure in the module.

More detail of the stack of carriers and energy storage devices is shown in Fig.5. An energy storage device 40, in this example, a battery cell, is mounted to the carrier 20 with one surface of the cell in contact with the cooler 22. The other surface may be provided with a flexible sheet 32 between that surface of the battery cell 40 and a surface of an adjacent cooler 22a in a stack of the type shown in Fig.4. This flexible sheet 32 allows the cell to swell over time, yet still allows the carrier 20 to maintain compression on the cell mounted within it. The sheet of flexible material increases thermal contact between the cell and the surface of its cell carrier 27, when placed between the cell and the carrier on one side. Such a material applies a low pressure, typically below 0.2bar, on the cell wall to increase performance and lifespan and accepts swelling due to normal operation and degradation during the complete life of the cell. The carriers 20 are mounted on one another and fixed together via fittings, such as bolts in fittings 24, 25. Between each water inlet section 3 and outlet section 7 on each carrier 20, a spacer, or washer 29, 28 may be provided.

The cooling system may be operated such that the time for which the additional cooling is provided is increased over that available simply from the cooling fluid reservoir of the closed circuit system. In normal operation, cooling fluid is circulated via the inlet and outlet pipes 3, 7 to the coolers 22 of each energy storage module 4. In the event of an outlet pipe connection 31 melting and a consequential pressure drop being detected by a controller of the cooling unit 1 and if the closed circuit cooling unit has access to an alternative source of cooling fluid, such as a mains water supply, or a fire hydrant, then the controller in the cooling unit may respond to the detected pressure drop in the system. For example, after a predetermined time, during which the cooling fluid reservoir is emptied, the cooling unit may connect the reservoir, or cooling unit, to the alternative cooling fluid. The controller may be set to only connect to the alternative supply for a limited time period to prevent all of the energy storage units from being swamped by the cooling fluid that exits through the failed pipe connector.

To increase thermal contact between cell and cell carrier, a flexible material can be placed between the cell and the carrier on one side. Such a material can be used to apply pressure on the cell wall (to increase performance and lifespan) and accept swelling due to normal operation and degradation during the complete life of the cell.

The direct contact of cooler and cell in the modules makes the cooling more effective than air cooling, or conductive fins with water cooling, so reducing the temperature difference between cell and coolant in normal operation. This cooling method works with asymmetric cooling, meaning that only one side is cooled and thermal insulation is used to prevent heat propagation on the other side, so the other side is completely thermally isolated in case of a thermal runaway. The method also works with stacking the integral cells and coolers as shown in Fig.4, without thermal insulation on one side, allowing the opposite surface of the cell to be cooled by the cooler of the neighbouring cell in the stack. In this case, either an extra cooler, or a single layer of thermal insulation at one end caters for the cells without two neighbours. . The low difference in temperature between cell surface and cooling fluid is due to the low thermal resistance between the cooling fluid and the cell. The only resistance is over the plastic material, which typically comprises a thermoplastic with up to 1 W / mK thermal conductivity. The stacking arrangement using one cooler to cool two adjacent cells helps to reduce weight and material cost.

Another benefit of the direct contact over the surface of the cell, is that this allows the operating temperature of the cooling liquid to be increased, thereby reducing the likelihood of condensation occurring inside the system. The use of polymer plastics materials for the cooler, rather than metal allows weight and cost to be reduced to a fraction of the conventional solutions. In addition, the modules no longer require a cooler block or heat exchanger, as is required with conventional air or water cooled systems, so the volumetric footprint can be reduced. This is particularly useful for marine and offshore applications, where space is at a premium. Direct heat transfer from the cell to the cooling fluid is made possible by constructing the cooling channels from tubes of a polymer material, the tubes having a sufficiently thin wall that thermal conductivity of the material is not a significant consideration. This allows a much wider choice of material to be used, so that weight and cost reduction can also be addressed.

As referenced hereinbefore, 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. The valves are typically small which does not allow a large amount of gas to be removed quickly. Conventional pressure release valves are designed to burst under pressure. As a consequence of this, any valve which has burst leaves an opening, so there is a risk that a thermal event could lead to flames emerging from that module into the exhaust system being transferred through the opening and coming into contact with a module that has already suffered from an overpressure that has caused its exhaust valve to burst.

Another potential problem is that if a module is withdrawn, for example for maintenance, this leaves a space where the module used to be in the exhaust channel. Similarly, during installation when not all modules are in place, there are open spaces in the exhaust channel. This gives rise to the potential for gas or flames emerging due to a thermal event in another module. This may be hazardous if an operative is working where the energy storage modules are located, as gas or flames might come out through the space into the working area.

An embodiment of the present invention addresses these problems by providing a closure member to act as a lightweight, non return valve in a housing, or in a mounting, for each energy storage module, or in both the housing and the mounting.

The pressure at which this non-return valve lifts and opens may be set to be quite low, so that there is very little risk of a build up of gas pressure in the module itself. However, by means of the closure member, any opening where a module has previously suffered a thermal event, or gas overpressure, remains closed after the gas has been dispersed and any module that has been removed from the mounting does not leave an opening, through which gas and flames from a subsequent thermal even in another module can escape.

For marine and offshore markets, in particular, standards require energy storage design to avoid propagation from a module suffering thermal runaway to other modules in the system. The amount of energy in a module is so high that athermal runaway in all cells is very difficult to contain. It is desirable to constrain a thermal event to a single cell to reduce the likelihood of the temperature increase in the affected cell causing thermal runaway propagation to neighbouring cell and more particularly to prevent propagation to neighbouring modules.

A typical module 4, for example of the type as described hereinbefore, is illustrated in Fig.6a. Each module 4 is provided with a housing 50 adapted to fit into an opening 54 in a mounting rack 60 as shown in Fig.7a. For clarity, the cooling system as illustrated in Fig.l is not shown in Fig.7a, but is typically present to provide cooling of the module to help reduce propagation due to a thermal event. At one end of the housing 50, is an opening 57 corresponding to the opening 54 in the mounting, to allow the flow of gas from inside the housing into an exhaust system behind the mounting rack opening.

The housing 50 is comprises a one-way, or non-return, valve 51 across the opening 57. If a thermal event occurs in the module 4, any gases that build up in the housing 50, or flames 52 from the thermal event, may escape from the housing simply by virtue of the increased pressure within the housing as compared to that outside the housing causing the closure member 51 to open. The closure may comprise a plate 51 of stiff material, such as aromatic polyamide (aramid) in conjunction with a resilient member 58, such as a spring, coil or elastic, or other means of applying pressure.

Preferably, the housing is shaped such that even without the resilient closure member 58, the valve is stable and closed in its natural rest position, for example by having a reduced length of the housing at its upper edge, relative to the length of the housing at the lower edge and pivoting the closure at the lower edge, so that the closure plate falls onto the upper edge if no pressure is applied from within the housing. This can be seen in the examples of Figs. 6a and 6b.

An alternative, as shown in Figs.8a and 8b, is to fix the closure member 51 in position at opposing points across the opening, without a spring, but to use a flexible, or resilient, material for the closure plate 51, rather than a rigid material, as shown in Fig.8a. An increase in pressure within the housing 50 causes the flexible plate 51 to bend as shown in Fig. 8b, to release gas, or flames, under pressure from the housing.

The plate 51 then springs back to close the opening when the internal pressure in the housing is no longer greater than the pressure in the exhaust channel.

One wall of the exhaust system may comprise the mounting rack, with additional walls 62, 63 to contain exhaust gas and flames and direct them to an outlet 64 as shown in Fig.7a, typically to a larger system exhaust. By connecting the module 4 to an exhaust system 61 flames and gas from a thermal event may be directed out of the system. As can be seen in Figs. 7a and 7b, the part of the exhaust channel formed from the mounting rack is also provided with a one-way, or non-return, valve. The construction of the valve may take a similar form to the rigid housing valve 51 described above, with a resilient closure 66 to hold the valve 65 normally closed. The mounting for the resilient closure may extend into the exhaust channel 61 to allow it to rest in a stable manor against the racking wall 60 above the opening 54.

The provision of a valve arrangement in the exhaust channel and module mounting addresses the problem of gas or flames escaping into the energy storage working area from an opening where no module is installed, or if a module is being removed. Module 55 illustrates an example where the module is being removed. As it is extracted, the force applied by the neck 59 of the housing 50 no longer holds the valve 65 open against the resilient member, but the resilient closure 66 forces the valve into contact with the wall mounting 60 of the exhaust channel, closing off that opening. Thus, the present invention further ensures that flammable gasses and actual flames do not exit from one module and enter one of the other modules connected in the system through the exhaust system.

It can be seen in Fig. 6b that in the event of flames or gas being created within the module and escaping into the housing, the pressure inside the housing opens the otherwise closed valve, when it exceeds the pressure setting of the valve, or the external pressure in the exhaust system, if the valve setting is close to zero, so as to allow the flames 52 and gas to escape through the exhaust channel rather than building up and causing an explosion within the housing. In Fig.7b, if a thermal event occurs, gas and flames may exit from a module 53, but the one way valves in the exhaust channel mountings ensure that the valves close off those exits where no module is present 54 in the racking mount of the exhaust channel, or where a module 55 is being removed. When a module is inserted, the pressure of the module holds the rack valve open, but the housing module valve provides protection against such an event instead.

The solution of the present invention improves reliability and reduces costs as compared to conventional overpressure valves. Using valves on both the exhaust channel and on the module increases reliability, but using such valves in either situation is still beneficial. The dual valve arrangement ensures that there are no open areas in the exhaust system during installation or service of modules as the module connection to the exhaust channel is protected by valve, which may be constructed as part of the manufacturing process for the energy storage system. Cost savings are possible by limiting the number of different geometries and materials used and the design allows for more mass export of flammable gas out of the module at a lower pressure, than current pressure release valves open at. This means that there is less pressure build up, reducing the risk of explosion. The overpressure at which the valve releases may be set to be close to zero as the only requirement to maintain the valve functionality is to ensure that it is in position under normal operational conditions. Any change from these circumstances can be assumed to require the valve to open.

System safety is improved by reducing the chances of fire or gas from a module escaping into the battery room when modules are not connected to the cubicle. Increased mass flow out of the module in a thermal event improves safety by releasing flammable gases, or fire before pressure is built up and heat is distributed to healthy cells in the module. The simple and flexible design allows lower cost materials and simpler geometries to be used, enhancing the production process. As the exhaust valve is opened and closed by the introduction and removal of the battery module the openings in the exhaust system are sealed unless they need to be open, when in operation.

Although the detailed examples have been given with respect to electrochemical cells, such as batteries, for example Li-ion, alkaline, or NiMh batteries, or others, the invention applies to other types of stored energy units, in particular non-cylindrical capacitors, ultracapacitors, or supercapacitors, fuel cells, or other types of energy storage which have a surface that can be cooled by a cooler and which 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.

Claims

1. An energy storage module housing, the housing comprising a perimeter wall, a neck and an opening in the neck of the perimeter wall to allow escape of gases from the module; wherein the opening further comprises a closure member.

2. A housing according to claim 1, wherein the closure member comprises a rigid closure member and a resilient member adapted to hold the closure member against the wall of the opening.

3. A housing according to claim 2, wherein the resilient member is pivotally mounted to a lower extension of the perimeter neck; and adapted to rest its end remote from the pivot on an upper extension of the perimeter neck.

4. A housing according to any preceding claim, wherein the closure member comprises a heat resistant plate.

5. An energy storage system, the system comprising an exhaust channel, the channel comprising two or more mounting openings, each mounting opening comprising a closure member and a resilient member adapted to hold the closure member against the wall of the opening.

6. A system according to claim 5, wherein the closure member is adapted to open to allow a neck of a module housing perimeter wall to be mounted to the exhaust channel.

7. A system according to claim 5 or claim 6, wherein the system further comprises a mounting rack to support each energy storage module, the mounting rack located adjacent the exhaust channel.

8. A system according to any of claims 5 to 7, wherein the system further comprises one or more energy storage module housings according to any of claims 1 to 4, each mounted in a mounting opening.

Intellectual

Property

Office

Application No: Claims searched:

GB1705523.7

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