Energy storage module rack

Abstract

The invention relates to a rack for holding energy storage modules such as batteries, an energy storage unit, an energy storage system, and a method for cooling energy storage modules stored in the rack or suppressing a fire in the rack. The rack comprises one or more structural frame elements for supporting the plurality of energy storage modules; at least one fluid inlet; and at least one fluid outlet; wherein the one or more structural frame elements form a continuous fluid channel from the at least one fluid inlet to the at least one fluid outlet.

Description

[0001] ENERGY STORAGE MODULE RACK

[0002] Technical Field

[0003] The invention relates to the field of energy storage, in particular to a specialised rack for holding energy storage modules such as batteries.

[0004] Background

[0005] Energy storage systems are used for storing and delivering electrical energy, e.g. to / from an electrical grid. Such systems typically include multiple battery modules arranged in close proximity, e.g. in a battery rack. Battery modules and other energy storage modules may be susceptible to thermal runaway both in an individual module and across the rack, where overheating of one module may lead to overheating of adjacent modules. There is therefore a need for cooling systems for stopping thermal runaway and fire suppression systems for extinguishing fires in the even that a fire breaks out. It is also desirable to make such systems as compact as possible in order to increase the energy storage density of the energy storage system; however, making the systems more compact reduces the available space for cooling and / or fire suppressant fluids to move within the system, exacerbating the problem of thermal runaway and potential fires. There is therefore a need for a compact energy storage system with effective cooling and / or fire suppression systems.

[0006] Summary of the Invention

[0007] A rack for holding a plurality of energy storage modules comprises one or more structural frame elements for supporting the plurality of energy storage modules; at least one fluid inlet; and at least one fluid outlet, wherein the one or more structural frame elements form a continuous fluid channel from the at least one fluid inlet to the at least one fluid outlet.

[0008] At least one structural frame element may be hollow and the hollow interior of the structural frame element may form the continuous fluid channel.

[0009] The hollow interior may comprise a cavity extending along a longitudinal axis of the structural frame element. The cross-section of the cavity may have one of the following shapes: a circle, a square, a rectangle, or a triangle.

[0010] The at least one fluid outlet may be an opening or a nozzle located on the one or more structural frame elements.

[0011] The rack may be configured to hold the plurality of energy storage modules in at least two vertical stacks, and at least one of the one or more structural frame elements may extend between the at least two vertical stacks.

[0012] The at least one fluid outlet may be configured to provide fluid to the exterior of one or more energy storage modules when loaded into the rack.

[0013] The at least one fluid outlet may be configured to provide fluid into an interstitial space formed between two or more energy storage modules when loaded into the rack.

[0014] The rack may comprise a plurality of energy storage module support structures connected to at least one of the one or more structural frame elements, each energy storage module support structure being configured to support an energy storage module when loaded into the rack, and a plurality of fluid outlets may be positioned on the one or more structural frame elements such that the plurality of fluid outlets are configured to provide fluid into an interstitial space formed between two or more energy storage modules when the energy storage modules are loaded into the rack.

[0015] The rack may be configured to hold generally rectangular cuboid shaped energy storage modules.

[0016] The fluid may be a gas, liquid, or foam.

[0017] The fluid channel provided by the one or more structural frame elements may be air-tight and / or water-tight.

[0018] The rack may further comprise a fluid collection system configured to collect fluid that exits the at least one fluid outlet. The at least one fluid outlet may comprise a plug that closes the fluid outlet, and the plug may be configured to vacate the fluid outlet when overheating or a fire is present within the rack.

[0019] The rack may further comprise a cooling system configured to circulate a cooling fluid within the fluid channel by pumping coolant into the fluid inlet and extracting coolant from the fluid outlet.

[0020] The one or more structural frame elements may be made of extruded metal, optionally wherein the metal is aluminium or steel.

[0021] The rack may further comprise one or more gas sensors configured to sense the composition of ambient gas sampled adjacent to the rack.

[0022] The gas sensors may be configured to sense the composition of ambient gas through the at least one fluid outlet.

[0023] The one or more structural frame elements may further comprise one or more gas sampling inlets configured to sample ambient gas surrounding the rack, and the one or more gas sampling inlets may be in fluid communication with the one or more gas sensors via the fluid channel formed by the one or more structural frame elements.

[0024] The rack may be configured to suck ambient gas to the one or more gas sensors.

[0025] The rack may further comprise a control system configured to pump coolant or fire suppressant into the fluid inlet in response to a signal generated by the one or more gas sensors indicative of overheating or a fire.

[0026] The control system may be configured to end suction of ambient gas in response to the signal indicative of overheating or a fire.

[0027] An energy storage unit comprises the rack and an outer enclosure covering the rack on one or more sides.

[0028] The energy storage unit may further comprise a plurality of energy storage modules.

[0029] An energy storage system comprises a plurality of energy storage units. A method for cooling a plurality of energy storage modules stored in the rack or suppressing a fire in the rack comprises pumping fluid into the fluid channel provided by the one or more structural frame elements.

[0030] The fluid may be a coolant.

[0031] The fluid may be a fire suppressant.

[0032] Pumping fluid into the fluid channel may cause fluid to exit the at least one fluid outlet and come into contact with the energy storage modules.

[0033] The method may further comprise, prior to pumping fluid into the fluid channel, detecting an alarm condition, the alarm condition comprising one or more of: overheating in one or more energy storage modules, and a fire in one or more energy storage modules and / or the rack.

[0034] The type of fluid pumped into the fluid channel may depend on the alarm condition.

[0035] The method may further comprise opening at least one fluid outlet such that fluid exits the at least one fluid outlet and comes into contact with the energy storage modules.

[0036] The method may further comprise, prior to opening the at least one fluid outlet, detecting an alarm condition, the alarm condition comprising one or more of: overheating in one or more energy storage modules, and a fire in one or more energy storage modules and / or the rack.

[0037] The method may further comprise pumping fluid into the fluid channel and / or opening the fluid outlets in response to a signal from one or more gas sensors, the signal from the one or more gas sensors being indicative of overheating or a fire within the energy storage modules.

[0038] The method may further comprise sucking ambient gas to the one or more gas sensors.

[0039] The method may further comprise ending suction of ambient gas in response to the signal indicative of overheating or a fire. The method may further comprise circulating or cycling cooling fluid within the fluid channel such that the cooling fluid cools the one or more structural frame elements without coming into direct contact with the energy storage modules.

[0040] The rack, the energy storage unit, or the energy storage system may further comprise a control system configured to perform the method.

[0041] Brief Description of the Drawings

[0042] FIG. 1 shows a front view of a rack according to an embodiment of the invention;

[0043] FIG. 2 and FIG. 3 illustrate a second embodiment of a rack according to the invention; and FIG. 4 and FIG. 5 illustrate an embodiment of an energy storage unit according to the invention.

[0044] Detailed Description of the Invention

[0045] Embodiments of the rack, the energy storage unit, the energy storage system, and the method described herein provide multi-functional solutions for storing energy storage modules, with integrated cooling and / or fire suppression systems. The rack not only provides structural support to withstand the weight of energy storage modules, but also contains fluid paths which can be used to suck and provide fluids to the energy storage modules.

[0046] FIG. 1 shows front view of a rack 100 according to an embodiment of the invention. The rack 100 comprises structural frame elements 102-106 for supporting energy storage modules 110-114 loaded into the rack. Structural frame elements 102-104 provide vertical supports, and structural frame elements 105, 106 provide horizontal supports for the rack.

[0047] The energy storage modules 110-114 may be chemical battery modules or (super)capacitors, for example. The energy storage modules may be rechargeable. Malfunction of the energy storage modules can result in the uncontrolled escape of energy stored in the modules, and a large amount of energy can be released in this manner from high energy density storage modules. Different types of energy storage modules may be susceptible to specific malfunctions, such as thermal runaway in the case of lithium-ion batteries. The structural frame elements 102-106 are made of extruded metal. Aluminium provides ease of manufacturing, especially when manufacturing the continuous fluid channel as an integral part of a structural frame element by extrusion. However, steel is preferred for obtaining a strong yet compact structure for carrying the weight of the energy storage modules 110-114. Steel also tolerates higher temperatures (e.g. in the case of fire) without collapsing due to its higher melting point.

[0048] The energy storage modules 110-114 have a generally rectangular cuboid shape, and the rack of FIG. 1 is configured to hold energy storage modules having such a shape. The rack 100 comprises energy storage module support structures 116 connected to structural frame elements 102-104 for supporting the energy storage modules loaded onto the rack. The support structures are made of the same material as the structural frame elements. The support structures extend from the structural frame element towards another structural frame element in a horizontal direction. The support structures may further extend along the structural frame element, i.e. into the viewing direction of FIG. 1. Each energy storage module 110-114 is supported by at least two support structures arranged at substantially the same level on two structural frame elements facing each other in the embodiment of FIG. 1. The support structures are spaced out so that the space between the structural frame elements is not completely filled by the energy storage modules, allowing for fluid flow within the rack even when it is filled with energy storage modules.

[0049] A first continuous fluid channel 122 is formed by the structural element 103. In the embodiment of FIG. 1 , the structural element 103 is hollow and the hollow interior of the structural frame element forms the first fluid channel 122. The hollow interior comprises a cavity extending along a longitudinal axis of the structural frame element 103. The crosssection of the cavity, the cross-section being perpendicular to the longitudinal axis, may take various shapes, such as a circle, a square, a rectangle, or a triangle. The shape and / or size of the cross-section may vary along the longitudinal axis of the structural frame element, and / or one or both the shape and / or size of the cross-section may be the same along the along the longitudinal axis of the structural frame element. The cavity may be symmetric or asymmetric with respect to the (central) longitudinal axis of the structural frame element. Here the symmetry refers to rotational and / or reflection symmetry.

[0050] The rack 100 further comprises a first fluid inlet 118 and first fluid outlets 120, 121. The continuous fluid channel extends between the first fluid inlet and the first fluid outlets. A second continuous fluid channel 130 is formed by structural frame elements 102, 104, 105 and 106. The second continuous fluid channel 130 extends from a second fluid inlet 132 to a second fluid outlet 134.

[0051] In the embodiment of FIG. 1 , each structural frame element 102-106 forms at least a part of a continuous fluid channel. Although not shown in FIG. 1 , it is evident to the skilled person that each structural frame element of the rack does not need to form any part of a continuous fluid channel. For example, the rack of FIG. 1 might comprise further structural frame elements that do not form any part of a continuous fluid channel.

[0052] The continuous fluid channels are used to provide fluid for cooling the energy storage modules or suppressing a fire in the rack 100. This is done by pumping fluid into the channels provided by the one or more structural frame elements. Furthermore, in addition to cooling the battery modules, the circulation of fluid, e.g. a coolant, in the channels provided by the structural frame elements may also help to maintain the structural integrity of the rack and consequently also the energy storage system during a fire. The fluid may be a coolant, such as a mixture of water and glycol, water, and / or air, or a fire suppressant, such as water, compressed air, carbon dioxide, and / or a clean agent such as a halocarbon and / or an inert gas. Halocarbons include e.g. hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), perfluorocarbons (PFCs or FCs), fluoroiodocarbons (FICs), and fluoroketones (FKs). Inert gases include e.g. helium, neon, argon, or nitrogen. Some fluids, such as water, inert gases, (compressed) air, and mixtures of one or more coolants and one or more fire suppressants (e.g. liquid water and a gaseous agent, such as nitrogen) act as both coolants and fire suppressants. The fluid may be in the form of a gas, a liquid, and / or a foam, such as an aqueous film-forming foam, a protein foam, and / or a fluorine-free foam. Water is provided as a liquid, and compressed air, nitrogen, carbon dioxide, and argon are provided in the form of a gas.

[0053] Liquids are effective coolants as they bind thermal energy upon vaporization (heat of vaporization). Preferably, liquids that are electrically non-conductive are used to prevent short circuits within the rack.

[0054] Foams reduce contamination outside the rack as they have a reduced likelihood of escaping the rack. Instead, they fill the rack to extinguish or prevent a fire by displacing oxygen and preventing further oxygen from entering the space occupied by the foam. Carbon dioxide gas has both cooling and fire suppressing benefits as it does not release oxygen. It is also non-toxic. Carbon dioxide is suitable especially for “dry pipe” systems that are described in more detail in relation to the first continuous fluid channel 122.

[0055] Fire suppressants may be used to extinguish and / or control a fire, or entirely prevent a fire or an explosion from occurring. Fire and / or explosion potential reducing properties of fire suppressants are employed to reduce the likelihood of these events. Inert gases are very useful for reducing the explosion potential of the rack, energy storage unit, and / or energy storage system. An explosive atmosphere is prevented as the inert gas(es) displaces oxygen in the rack, energy storage unit, and / or energy storage system.

[0056] The first fluid outlets 120, 121 provide the fluid to the interstitial space between energy storage modules 110 and 111 , and 113 and 114. When the fluid is a liquid or foam, it is provided by outlet 120 to the exterior of energy storage module 111 , and by outlet 121 to the exterior of energy storage module 114. The liquid or foam can eventually drip to down to the exterior of further energy storage modules, such as module 112. When the fluid is a foam, it may also pile up on top of the energy storage modules 111 , 114 and eventually also drip down to the bottom exterior surfaces of energy storage modules 110, 113. When the fluid is a gas or a liquid aerosol, it is dispersed into the space not occupied by the energy storage modules 110-114 or the structural frame elements 102-104, and eventually spreads to reach the exteriors of some or all of the energy storage modules.

[0057] In the case of the first continuous fluid channel 122, pumping the fluid into the first continuous fluid channel 122 causes the fluid to exit via the first fluid outlets 120, 121. After exiting the first outlets 120, 121 , the fluid comes into contact with the energy storage modules as described above. As the first continuous fluid channel can be in a “dry” state, i.e. void of the fluid that is to be pumped into the channel, the first continuous fluid channel may be considered a “dry pipe”, especially when the fluid pumped into the channel is a liquid.

[0058] The rack 100 further comprises a container 124 configured as a liquid collection system. The container 124 is positioned at the bottom of the rack, and it collects liquids and condensed gases that have been output via the first fluid outlets 120, 121.

[0059] The second continuous fluid channel 130 forms part of a cooling system for cooling the rack 100. Cooling fluid or coolant is pumped into the second fluid inlet 132 and extracted from the second fluid outlet 134. The cooling fluid is cycled or circulated in the second continuous fluid channel to cool the structural frame elements 102, 104-106 without the cooling fluid coming into contact with the energy storage modules 110-114. Despite the lack of direct contact, the energy storage modules are also cooled by heat transfer via the structural frame elements. When the cooling fluid is continuously present in the second continuous fluid channel, the second continuous fluid channel may be considered a “wet pipe”, especially when the fluid pumped into the channel is a liquid. The second continuous fluid channel is airtight (to prevent escape of gases) and watertight (to prevent escape of liquids).

[0060] The energy storage modules 110-114 are arranged in two vertical stacks, i.e. a first stack formed by modules 110-112 and a second stack formed by modules 113 and 114. The first stack is supported by structural frame elements 102 and 103, and the second stack is supported by structural frame elements 103 and 104. The structural frame element 103 extends between the two stacks, and is able to provide fluid to both stacks with its first continuous fluid channel 122 and outlets 120, 121.

[0061] In the embodiment of FIG. 1 , the first fluid outlets 120, 121 are openings on the structural frame element 103. One or both of the first fluid outlets 120, 121 may be replaced by nozzles to control, preferably increase, the spray of liquids provided through the outlets. For gases, nozzles have the effect of targeting the spray of gas in a preferred direction, e.g. upwards, downwards, and / or towards the energy storage module(s), to improve the precision of cooling and / or fire suppression. However, an opening without a nozzle has a simpler construction than a nozzle, and may be preferred when gas is provided through the opening.

[0062] Various types of nozzles may be used to achieve a desirable spray of liquid and / or gas from the outlets, which in turn affects the spread of the liquid / gas within the rack. A spray jet nozzle may be used to provide a (nearly) continuous stream of liquid or gas, a droplet spray nozzle may be used to provide a spray of liquid (e.g. water) droplets, and an atomizing or misting nozzle may be used to provide a spray of liquid aerosols. Aerosols provide an increased cooling effect when compared to the same amount of liquid in the form of liquid droplets or a continuous stream. This is due to their larger surface area, which leads to increased evaporation. A similar effect can also be observed in the fire quenching ability of aerosols. In general, a droplet size of 0.25 mm in diameter is suitable for cooling and fire suppression.

[0063] In addition to nozzle type, fluid pressure at the outlet affects the type of spray provided by the nozzle. Generally, the pressure of the fluid in the fluid channel ranges from 20 to 150 PSI. Droplet size generally decreases with increased pressure. A spray of aerosols may therefore be achieved even with a spray jet nozzle or a droplet spray nozzle by increasing the pressure in the continuous fluid channel to e.g. 7 PSI - 200 PSI, or 48 kPa - 1379 kPa.

[0064] The rack further comprises a gas sensor 140 configured to sense the composition of ambient gas adjacent to, and / or within the rack, i.e. within the space defined by the outermost structural frame elements of the rack. The gas sensor is configured to sample the ambient gas and to measure its composition. In addition, one or both of the first fluid outlets 120,121 may operate as gas sampling inlets for sampling the ambient gas around and / or within the rack. The first fluid outlets 120,121 are in fluid communication with the gas sensor 140 via the first fluid channel 122 and thus configured to provide the ambient gas to the gas sensor 140. Other gas sampling inlets that do not operate as fluid outlets can also be provided in the rack 100 in addition to, or as an alternative to the first fluid outlets 120,

[0065] 121.

[0066] The gas sensor 140 is configured to generate a signal based on the composition of the ambient gas. The signal includes alarms detected for certain conditions, such as overheating in one or more of the energy storage modules 110-114, or a fire in one or more energy storage modules 110-114 and / or the rack 100. A control system is connected to the gas sensor 140 of FIG. 1 ; the control system is configured to control pumping fluid into the first and second continuous fluid channels 122, 130 based on the signal generated by the gas sensor 140. If the gas sensor detects that the composition of the ambient air indicates overheating of the energy storage modules 110-114, the control system starts pumping coolant into the second fluid inlet 132 to cool down the energy storage modules without directly exposing the energy storage modules to the coolant. In an alternative implementation, the coolant is also provided to the first fluid inlet 118. If the gas sensor detects that the composition of the ambient air indicates a fire within or near the rack, the control system will start pumping a fire suppressant into the first fluid inlet 118. The fire suppressant travels through the first continuous fluid channel 122 and is released through the first fluid outlets 120, 121 to suppress the fire within the rack.

[0067] As an alternative (or in addition) to controlling pumping the fluid into the first fluid channel

[0068] 122, the control system controls the first fluid outlets 120, 121. This can be implemented with e.g. valves that are controlled by the control system. If the gas sensor detects overheating or a fire as described above, the control system opens the first fluid outlets 120, 121 such that the fluid that was in the first continuous fluid channel, or that is pumped into the first continuous fluid channel, exits the outlets and comes into contact with the energy storage modules. As a further alternative that does not require the presence of the gas sensor or the control system, the first fluid outlets 120, 121 comprise plugs that close the fluid outlets. The plugs comprise material, such as a wax or a plastic, that melts upon overheating or fire within the rack. This way, the plugs are configured to vacate the fluid outlets when overheating or a fire is present within the rack.

[0069] The plugs may also co-exist and collaborate with the gas sensor and the control system. The first continuous fluid channel 122 can be maintained at lower pressure than the interstitial space in the rack. When the plugs melt due to fire or overheating, the gases in the interstitial space are sucked into the first continuous fluid channel due to the initial pressure difference. This introduces the gases to the gas sensor 140 and stabilizes the pressure inside the first continuous fluid channel to the same level as in the interstitial space. The gas sensor is able to detect the condition that caused the plugs to melt by sensing the change (increase) in pressure, by the change in the gas composition and / or by detecting predetermined combustion gases. However, the presence and melting of the plugs is not necessary for the ambient, interstitial gases to be sucked to the gas sensor 140.

[0070] After starting to pump the fluid into the first continuous fluid channel, the control system is further configured to increase the fluid pressure in the channel e.g. by increasing the pumping. This accounts for the scenario where one of the plugs fails to vacate the first fluid inlets 120, 121 , and the remaining plug is pushed out by the increased fluid pressure.

[0071] To further facilitate introduction of ambient gas to the gas sensor, a sucking system may be configured to suck the ambient gas to the gas sensor via e.g. the first fluid outlets 120, 121 . The control system may control the sucking system. The sucking system may include e.g. one or more pumps, or any other devices suitable for creating suction that are known to the skilled person. Additionally or alternatively the sucking system may be configured to suck combustion gases, fumes and / or smoke out of the rack, energy storage unit, and / or energy storage system in response to the gas sensor detecting overheating or a fire.

[0072] A second embodiment of a rack 200 according to the invention is shown in FIG. 2 (projection view) and FIG. 3 (front view). The rack 200 comprises structural frame elements 202, 204, 302 that form the continuous fluid channel. The continuous fluid channel includes an intersection of two fluid channels that extend in two structural frame elements 202, 204, improving the spread of the fluid throughout the rack. Energy storage modules, such as those shown in FIG. 1 , can be stored on the support structures 204 of the rack 200. FIG. 4 and FIG. 5 show two different views of an embodiment of an energy storage unit 400 according to the invention. The energy storage unit 400 comprises a rack according to the invention, and an outer enclosure covering the rack on one or more sides. A continuous fluid channel is formed within the structural frame elements 412-414, 504 of the rack of the energy storage unit 400. The continuous fluid channel includes an intersection of two fluid channels that extend in two structural frame elements 412, 413. Energy storage modules, such as those shown in FIG. 1 , can be stored on the support structures 416, 502 of the rack of the energy storage unit 400. The outer enclosure of the energy storage unit 400 includes roof panels 402, 403, wall panels 404, 406, 408, and a floor panel 500. Further panels may be included to cover all sides of the energy storage unit 400, including the top side that is partially covered by panels 402 and 403 in FIG. 2. The outer enclosure may be a (modified) shipping container. The outer enclosure provides electrical isolation in a system comprising a plurality of energy storage modules. The enclosure also offers protection from the elements when the energy storage unit 400 is placed outdoors.

Claims

Claims1 . A rack for holding a plurality of energy storage modules, the rack comprising: one or more structural frame elements for supporting the plurality of energy storage modules; at least one fluid inlet; and at least one fluid outlet; wherein the one or more structural frame elements form a continuous fluid channel from the at least one fluid inlet to the at least one fluid outlet.

2. The rack of claim 1 , wherein at least one structural frame element is hollow and where the hollow interior of the structural frame element forms the continuous fluid channel.

3. The rack of claim 2, wherein the hollow interior comprises a cavity extending along a longitudinal axis of the structural frame element.

4. The rack of claim 3, wherein the cross-section of the cavity has one of the following shapes: a circle, a square, a rectangle, or a triangle.

5. The rack of any preceding claim, wherein the at least one fluid outlet is an opening or nozzle located on the one or more structural frame elements.

6. The rack of any preceding claim, wherein the rack is configured to hold the plurality of energy storage modules in at least two vertical stacks, and at least one of the one or more structural frame elements extends between the at least two vertical stacks.

7. The rack of any preceding claim, wherein the at least one fluid outlet is configured to provide fluid to the exterior of one or more energy storage modules when loaded into the rack.

8. The rack of claim 7, wherein the at least one fluid outlet is configured to provide fluid into an interstitial space formed between two or more energy storage modules when loaded into the rack.

9. The rack of claim 8, wherein the rack comprises a plurality of energy storage module support structures connected to at least one of the one or more structural frameelements, each energy storage module support structure being configured to support an energy storage module when loaded into the rack, and wherein a plurality of fluid outlets are positioned on the one or more structural frame elements such that the plurality of fluid outlets are configured to provide fluid into an interstitial space formed between two or more energy storage modules when the energy storage modules are loaded into the rack.

10. The rack of any preceding claim, wherein the rack is configured to hold generally rectangular cuboid shaped energy storage modules.

11. The rack of any preceding claim, wherein the fluid is a gas, liquid, or foam.

12. The rack of any preceding claim, wherein the fluid channel provided by the one or more structural frame elements is air-tight and / or water-tight.

13. The rack of any preceding claim, further comprising a fluid collection system configured to collect fluid that exits the at least one fluid outlet.

14. The rack of any preceding claim, wherein the at least one fluid outlet comprises a plug that closes the fluid outlet, and wherein the plug is configured to vacate the fluid outlet when overheating or a fire is present within the rack.

15. The rack of any preceding claim, wherein the rack further comprises a cooling system configured to circulate a cooling fluid within the fluid channel by pumping coolant into the fluid inlet and extracting coolant from the fluid outlet.

16. The rack of any preceding claim, wherein the one or more structural frame elements are made of extruded metal, optionally wherein the metal is aluminium or steel.

17. The rack of any preceding claim, wherein the rack further comprises one or more gas sensors configured to sense the composition of ambient gas sampled adjacent to the rack.

18. The rack of claim 17, wherein the gas sensors are configured to sense the composition of ambient gas through the at least one fluid outlet.

19. The rack of claim 17, wherein the one or more structural frame elements further comprises one or more gas sampling inlets configured to sample ambient gas surrounding the rack, and wherein the one or more gas sampling inlets are in fluid communication with the one or more gas sensors via the fluid channel formed by the one or more structural frame elements.

20. The rack of claim 18 or 19, wherein the rack is configured to suck ambient gas to the one or more gas sensors.

21. The rack of claim 20, wherein the rack further comprises a control system configured to pump coolant or fire suppressant into the fluid inlet in response to a signal generated by the one or more gas sensors indicative of overheating or a fire.

22. The rack of claim 21 , wherein the control system is configured to end suction of ambient gas in response to the signal indicative of overheating or a fire.

23. An energy storage unit comprising the rack of any preceding claim and an outer enclosure covering the rack on one or more sides.

24. The energy storage unit of claim 23, further comprising a plurality of energy storage modules.

25. An energy storage system comprising a plurality of energy storage units according to claim 23 or 24.

26. A method for cooling a plurality of energy storage modules stored in the rack of claim 1 or suppressing a fire in the rack of claim 1 , the method comprising: pumping fluid into the fluid channel provided by the one or more structural frame elements.

27. The method of claim 26, wherein the fluid is a coolant.

28. The method of claim 26, wherein the fluid is a fire suppressant.

29. The method of claim 26, wherein pumping fluid into the fluid channel causes fluid to exit the at least one fluid outlet and come into contact with the energy storage modules.

30. The method of claim 29, wherein the method further comprises, prior to pumping fluid into the fluid channel, detecting an alarm condition, the alarm condition comprising one or more of: overheating in one or more energy storage modules, and a fire in one or more energy storage modules and / or the rack.

31. The method of claim 30, wherein the type of fluid pumped into the fluid channel depends on the alarm condition.

32. The method of any of claims 26 to 31 , the method further comprising: opening at least one fluid outlet such that fluid exits the at least one fluid outlet and comes into contact with the energy storage modules.

33. The method of claim 32, wherein the method further comprises, prior to opening the at least one fluid outlet, detecting an alarm condition, the alarm condition comprising one or more of: overheating in one or more energy storage modules, and a fire in one or more energy storage modules and / or the rack.

34. The method of any of claims 26 to 33, wherein the method further comprises pumping fluid into the fluid channel and / or opening the fluid outlets in response to a signal from one or more gas sensors, the signal from the one or more gas sensors being indicative of overheating or a fire within the energy storage modules.

35. The method of claim 34, wherein the method further comprises sucking ambient gas to the one or more gas sensors.

36. The method of claim 35, wherein the method further comprises ending suction of ambient gas in response to the signal indicative of overheating or a fire.

37. The method of any of claims 26 to 36, wherein the method further comprises circulating or cycling cooling fluid within the fluid channel such that the cooling fluid cools the one or more structural frame elements without coming into direct contact with the energy storage modules.

38. The rack of any of claims 1 to 22, the energy storage unit of claim 23 or 24, or the energy storage system of claim 25, further comprising a control system configured to perform the method of any of claims 26 to 37.

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