Burst-proof metallic storage unit and method for additive manufacturing of such a storage unit

Abstract

The invention relates to a storage unit for storing gaseous media, comprising a storage body enclosing a storage volume configured to receive a gaseous medium, and at least one connection designed and configured to establish fluid communication between the storage volume and an exterior of the storage body. The storage body comprises an outer wall defining an outer dimension of the storage body, an inner wall formed within the outer wall of the storage body and configured to limit the storage volume externally, and a reinforcement structure formed between the inner wall of the storage body and the outer wall of the storage body.

Description

[0001] The present invention relates to a burst-proof metallic storage unit for gaseous media, comprising a storage body and a storage volume, wherein the storage body is formed from an outer wall, an inner wall, and a reinforcing structure. The present invention further relates to a method for the additive manufacturing of such a storage unit, in particular by means of laser-based powder bed fusion of metals.

[0002] Storing gaseous media presents a key challenge for the further development of hydrogen-based energy systems, particularly in mobility applications. Conventional storage units, such as Type 1 pressure vessels made entirely of metal (typically steel or aluminum), store hydrogen at a pressure of 200 to 300 bar. However, these traditional approaches have numerous drawbacks, especially regarding weight and efficiency, which limit their applicability.

[0003] To overcome these limitations, advanced storage units have been developed, including Type 2, Type 3, and Type 4 pressure vessels that utilize composite materials such as carbon fibers or plastics. These materials enable a significant reduction in weight and an increase in storage capacity by storing hydrogen at higher pressures of up to 700 bar. Despite these advances, the challenge remains that these storage units operate under extremely high pressure, making them more susceptible to material fatigue and potential rupture.

[0004] The rupture of a storage unit of this type, and the resulting sudden release of its gas contents, poses a significant safety risk, as a massive amount of energy is released in a very short time, comparable to an explosion. This release can cause serious damage, thus increasing the urgency to develop storage units that are both safer and more efficient.

[0005] In this regard, DE 10 2020 117 916 A1 discloses a storage unit for storing fluids, comprising a storage body with an outer wall and an inner wall, wherein the storage body further has a reinforcing structure arranged between the outer wall and the inner wall. Reference is also made to US 2018 / 0 229 863 A1.

[0006] The object of the present invention is to provide a constructive solution for this purpose which enables burst safety, whereby a storage unit according to the invention can withstand very high pressures, preferably 1500 bar or more.

[0007] According to the invention, this problem is solved by a burst-proof metallic storage unit comprising a storage body enclosing a storage volume configured to receive a gaseous medium, and at least one connection designed and configured to establish fluid communication between the storage volume and an exterior of the storage body, the storage body comprising an outer wall defining an outer dimension of the storage body, an inner wall formed within the outer wall of the storage body and configured to delimit the storage volume to the outside, and a reinforcement structure formed between the inner wall of the storage body and the outer wall of the storage body.

[0008] In contrast to conventional storage units, the bursting behavior of the storage unit according to the invention is controlled by the targeted use of a reinforcement structure within the storage body. This ensures that the storage unit according to the invention does not burst even under unexpected conditions, but rather releases the stored gas in a controlled manner and without an explosive release. In the event of bursting, for example, an external leak or crack may occur in a storage unit according to the invention, allowing the gaseous medium to escape in a controlled and non-explosive manner.

[0009] In addition, the innovative design allows for an increase in storage capacity while maintaining the same volume and the same or lower weight.

[0010] The storage body, which comprises the outer wall, inner wall, and reinforcement structure, can also be integrally manufactured as a single piece. By manufacturing the storage body as an integral single piece, potential weak points are eliminated, as there are no welds or joints. This increases structural integrity and minimizes the risk of material failure under pressure. Furthermore, eliminating additional components and connections simplifies the manufacturing process, and the storage unit requires less maintenance, since potential weak points of connections are eliminated.

[0011] Furthermore, the reinforcement structure of the storage unit can comprise a plurality of reinforcement walls, which are connected at a first end section, which is closer to the storage volume, to the inner wall of the reinforcement layer and at a second end section, which is closer to the outer wall of the storage body, to the outer wall of the storage body.

[0012] The multiple reinforcement walls of the reinforcement structure ensure an optimized distribution of forces within the material, allowing for higher pressures in the storage unit without increasing the amount of material used. High local stability of the storage unit can only be achieved through the complex structures of these multiple reinforcement walls, which both reduce weight and ensure burst resistance.

[0013] The storage body further comprises at least one intermediate wall, which is formed between the inner wall and the outer wall and is connected to the reinforcing structure in such a way that the majority of reinforcing walls between the connection with the outer wall of the storage body and the connection with the inner wall of the storage body are also connected to the at least one intermediate wall of the storage body. By forming the storage body with one or more intermediate walls, the stability and thus the burst resistance of the storage unit can be further increased.

[0014] Advantageously, the storage body can be made of a metallic material, preferably a titanium alloy. A metallic design of the storage body allows for excellent gas tightness, high strength and durability, as well as temperature resistance, with a titanium alloy construction further improving strength compared to steel containers while reducing weight.

[0015] Furthermore, the storage unit can be designed for a maximum pressure of more than 200 bar, preferably more than 400 bar. Storing gaseous media, especially hydrogen, requires high pressure resistance of the storage units. Pressure resistance is understood as the ability of a material or structure to permanently withstand the pressure exerted by a gaseous medium without failing or suffering mechanical damage. Reference is made to Tables 1 and 2, which present burst pressure test results for storage units without the inventive reinforcement structure (Table 1) and storage units with the inventive reinforcement structure (Table 2). Table 1: Burst pressure test of storage units with only one outer wall Nr.: Designation / Serial No.: vpa[bar / s] pB[bar] pmax[bar] remark 1 T0a - =pmax 466,4 Examinee bursts 2 T1a - =pmax 485,7 Examinee bursts 3 T2a - =pmax 460,3 Examinee bursts 4 T3a - =pmax 239,5 Examinee bursts 5 T4a - =pmax 45,2 Examinee leaks Legend: vpa = pressure build-up rate pB = Burst pressure pmax = Maximum pressure Table 2: Burst pressure test of storage units with reinforcement structure according to the invention Nr.: Designation / Serial No.: vpa[bar / s] pB[bar] pmax[bar] remark 1 T1a - =pmax 572,5 2 T2a - =pmax 627,8 3 T3a - =pmax 531,4 4 T4a - =pmax 513,5 Legend: vpa = pressure build-up rate pB = Burst pressure pmax = Maximum pressure

[0016] To create Table 1, 5 test specimens with only one outer wall were subjected to a burst pressure test, whereby 1 test specimen was found to be leaking, therefore only 4 are to be considered for an evaluation of the maximum pressure.

[0017] To create Table 2, 4 test specimens with a reinforcement structure according to the invention were subjected to a burst pressure test.

[0018] Accordingly, storage units with the reinforcement structure according to the invention show a higher pressure resistance, in which a maximum pressure of 513.5 bar to 627.8 bar was determined, than storage units without the reinforcement structure according to the invention, in which a maximum pressure of 239.5 bar to 485.7 bar was determined (without taking into account the failed test specimen “T4a” of the test series from Table 1).

[0019] The tests further revealed that in the case of a storage unit of this type with only one outer wall, as shown in Table 1, a bursting event would result in the release of energy within a very short time, comparable to an explosion. This energy release can cause massive damage to the storage unit, such as entire sections of the outer wall breaking away, potentially leading to property damage or personal injury.

[0020] In contrast, a storage unit according to the invention, as shown in Table 2, provides burst protection. In the event of pressures far exceeding a permissible pressure, material weaknesses in the storage body, or damage to the storage unit due to external influences, a controlled failure occurs. This means that in the event of a burst, there is no explosive discharge of the storage unit, but rather an external leak develops, for example in the form of a crack, through which the gaseous medium can escape in a controlled and non-explosive manner.

[0021] In a further development of the invention, the storage unit can also include an additional reinforcement structure, which is formed within the storage volume and is connected to the inner wall of the storage body at least at one point. By forming the storage unit with an additional reinforcement structure within the storage volume, the stability and burst resistance of the storage unit can be further increased.

[0022] Furthermore, the storage body can include a cover layer applied to the outer and / or inner circumferential surface of the storage body's outer wall. This cover layer is preferably made of a fiber-reinforced composite material. The use of fiber-reinforced composites on the outer and / or inner circumferential surface of the storage body's outer wall optimizes the pressure resistance of the storage unit. Combining titanium alloys with composite materials also achieves optimal strength at minimal weight.

[0023] Furthermore, the storage unit can be a mobile storage unit designed for use in a means of transport. General areas of application include, for example, space travel, aerospace, automotive (electromobility), general energy supply, in combination with fuel cells, hydrogen storage, etc., whereby such a mobile storage unit can find application particularly in the field of mobility, preferably in passenger cars, aircraft, buses, motorcycles, bicycles, and the like.

[0024] According to a second aspect, the invention relates to a method for the additive manufacturing of a storage unit according to an embodiment of the first aspect of the invention. The method may include a step of laser-based powder bed fusion of metals. The laser-based powder bed fusion of metals enables the production of the storage body of a storage unit with an outer wall, an inner wall, and one or more intermediate walls, as well as a corresponding reinforcement structure between the outer and inner walls of the storage body.

[0025] According to a third aspect, the invention relates to a fuel cell comprising a storage unit according to an embodiment of the first aspect of the invention. A fuel cell comprising a storage unit according to the invention is particularly suitable for use in vehicles, aircraft, space applications, drones, cars, bicycles, and the like.

[0026] It should be added that the complete geometry of the storage unit can be calculated entirely using specialized software, preferably without the use of CAD. All relevant parameters, such as the desired volume (diameter * height), the number of walls of the storage body, the thickness of the outer wall of the storage body, and the shape of the reinforcement structure between the walls of the storage body, must be defined in a parameter list before the calculation.

[0027] Furthermore, it should be mentioned that the pressure within the reinforcement structure, i.e., between the outer wall and the inner wall, may be equal to or different from the pressure of the storage volume.

[0028] The invention will be explained in more detail below with reference to exemplary embodiments and the accompanying drawings. It illustrates: Fig.1 a perspective view of a longitudinal section of a first embodiment of the storage unit according to the invention, Fig. 2 a perspective view of a cross-section along a diameter of a first embodiment of the storage unit according to the invention, Fig. 3 a cross-section along a diameter of a first embodiment of the storage unit according to the invention, Fig. 4 an external view of a first embodiment of the storage unit according to the invention, and Fig. 5a and Fig. 5b a perspective view of a longitudinal section and a detailed view of the longitudinal section of a second embodiment of the storage unit according to the invention.

[0029] In Fig.Figure 1 shows a perspective view of a longitudinal section of a first embodiment of the storage unit, which is generally designated as 100. The storage unit 100 comprises a storage volume 114, which has a substantially cylindrical shape and is designed and configured to receive a gaseous medium, and a storage body 112, which encloses the storage volume 114.

[0030] Furthermore, the storage unit 100 comprises a first connection 126 and a second connection 128, which are arranged at opposite ends of the storage body 112 with respect to a longitudinal axis A of the storage body 112 and are configured to enable the filling and emptying of the storage volume with a gaseous medium. The first connection 126 and the second connection 128 are circular openings, each forming a passage to the storage volume, with the longitudinal axis A representing an axis of symmetry of the circular openings and the corresponding passages to the storage volume. By designing the storage unit 100 with a first connection 126 and a second connection 128, the storage unit 100 is, for example, able to perform the processes of filling and emptying the gaseous medium simultaneously.Furthermore, multiple ports can be used as spares or for alternative operating modes. Similarly, a port can serve, for example, as a safety port equipped with a pressure relief valve that automatically releases excess pressure in case of danger, thus ensuring safety without affecting any other port.

[0031] The storage body 112 in Fig.The storage body 112 comprises an outer wall 116, an inner wall 118, an intermediate wall 124, and a reinforcing structure 120. The outer wall 116 of the storage body 112 represents the outer dimension of the storage unit 100, while the inner wall 118 of the storage body 112, which is formed within the outer wall 116 of the storage body 112, forms an outer boundary of the storage volume 114. The intermediate wall 124 of the storage body 112 and the reinforcing structure 120 of the storage body 112 are formed between the outer wall 116 of the storage body 112 and the inner wall 118 of the storage body 112.

[0032] Furthermore, a plurality of reinforcing walls 122 of the reinforcing structure 120 are formed between the outer wall 116 of the storage body 112 and the inner wall 118 of the storage body 112. The plurality of reinforcing walls 122 of the reinforcing structure 120 are connected at end sections that are close to the intermediate wall 124 of the storage body 112 and at other end sections that are close to the outer wall 116 of the storage body 112 or the inner wall 118 of the storage body 112, respectively, are connected accordingly to the outer wall 116 of the storage body 112 or the inner wall 118 of the storage body 112.

[0033] As in Fig.As shown in Figure 1, the majority of the reinforcement walls 122 of the reinforcement structure 120 run essentially meandering through free spaces formed by the boundaries of the outer wall 116, the inner wall 118 and the intermediate wall 124 of the storage body 112.

[0034] Furthermore, it can be seen that the majority of reinforcing walls 122 extend radially with respect to the longitudinal axis A at the end sections of the storage body, near the first connection 126 or the second connection 128, between the outer wall 116 and the intermediate wall 124 or between the intermediate wall 124 and the inner wall 118, respectively. Accordingly, the inner wall 118 and the intermediate wall 124 are open to the outside of the storage unit 100 at the end sections of the storage body 112 with respect to the longitudinal axis A.

[0035] The structure of the reinforcement structure 120 of the storage body 112, in particular the structure of the majority of reinforcement walls 122, is further described in the Fig. 2 and Fig.Figure 3 illustrates a perspective view of a cross-section and the cross-section of the first embodiment of the storage unit according to the invention, wherein the cross-section is taken along a diameter at a central section of the storage unit 100 with reference to the longitudinal axis A. It is disclosed how the majority of reinforcing walls 122 of the reinforcing structure 120 are formed essentially in a zigzag shape in the circumferential direction between the outer wall 116 of the storage body 112 and the intermediate wall 124 of the storage body 112, or between the intermediate wall 124 of the storage body 112 and the inner wall 118 of the storage body 112.It is disclosed that those of the plurality of reinforcing walls 122 of the reinforcing structure 120 which are formed between the outer wall 116 of the storage body 112 and the intermediate wall 124 are connected at one end section to the outer wall 116 of the storage body 112 and at their other end section to the intermediate wall 124 of the storage body 112, and those of the plurality of reinforcing walls 122 of the reinforcing structure 120 which are formed between the intermediate wall 124 of the storage body 112 and the inner wall 118 of the storage body 112 are connected at one end section to the intermediate wall 124 of the storage body 112 and at their other end section to the inner wall 118 of the storage body 112.

[0036] Additionally, in the Fig. 1, Fig. 2 and Fig.3. It can be seen that the outer wall 116 of the storage body 112 is thicker than the inner wall 118 of the storage body 112 and / or the majority of the reinforcing walls 122 of the reinforcing structure 120, wherein the outer wall 116 of the storage body 112 here includes a cover layer 130, which is formed on the outer wall 116 of the storage body 112. In general, the thicker the outer wall 116 of the storage body 112, the higher the pressure that can be uniformly achieved within the storage unit 100.

[0037] Fig. Figure 4 shows an external view of the first embodiment of the storage unit according to the invention, wherein the storage body 112 is provided at both ends with a thread 134 in relation to the longitudinal axis A of the storage unit 100, which surrounds the first connection 126 or the second connection 128 of the storage unit 100.

[0038] In Fig. 5a and Fig. Figure 5b shows a further embodiment of the storage unit. The second embodiment of the storage unit is designated by reference numerals that are increased by 100 compared to the first embodiment of the storage unit 100. The following section will focus primarily on the differences between the second embodiment of the storage unit 200 and the first embodiment of the storage unit 100. Furthermore, reference is made to the descriptions of the first embodiment of the storage unit 100, which may be applied analogously to the second embodiment of the storage unit 200, and vice versa.

[0039] The storage unit 200, which is located in the Fig. 5a and Fig. As shown in Figure 5b, it comprises a storage volume 214, a storage body 212 and a connection 226.

[0040] The storage body 212 here comprises only an outer wall 216 and an inner wall 218 as well as a reinforcement structure 220 and an additional reinforcement structure 232, wherein the additional reinforcement structure 232 is formed within the storage volume 214 and is connected at several points to the inner wall 218 of the storage body 212.

[0041] As in the Fig. 5a and Fig. As can be seen in Figure 5b, the additional reinforcement structure 232 also represents a complex form, which is formed in a twisted meandering manner in the storage volume 214.

Claims

[1] Storage unit (100; 200) for storing fluids, in particular gaseous media, comprising a storage body (112; 212) which encloses a storage volume (114; 214) which is configured to receive a gaseous medium, and at least one connection (126, 128; 226) which is provided and configured to establish fluid communication between the storage volume (114; 214) and an exterior of the storage body (112; 212), wherein the storage body (112; 212) comprises: - an outer wall (116; 216) which defines an outer dimension of the storage body (112; 212), - an inner wall (118; 218) which is formed within the outer wall (116; 216) of the storage body (112; 212) and is designed to limit the storage volume (114; 214) to the outside, and - a reinforcing structure (120; 220) formed between the inner wall (118; 218) of the storage body (112; 212) and the outer wall (116; 216) of the storage body (112; 212), wherein the storage body (112) further comprises at least one intermediate wall (124) formed between the inner wall (118) of the storage body (112) and the outer wall (116) of the storage body (112) and connected to the reinforcing structure (120) of the storage body (112) such that the plurality of reinforcing walls (122) between the connection with the outer wall (116) of the storage body (112) and the connection with the inner wall (118) of the storage body (112) are further connected to the at least one intermediate wall (124) of the storage body (112). are. [2] Storage unit (100; 200) according to claim 1, wherein the storage body (112; 212) comprising the outer wall (116; 216), inner wall (118; 218) and reinforcement structure (120; 220) is integrally formed in one piece. [3] Storage unit (100; 200) according to one of the preceding claims, wherein the reinforcement structure (120; 220) comprises a plurality of reinforcement walls (122) which are connected at a first end section which is closer to the storage volume (114; 214) to the inner wall (118; 218) of the storage body (112; 212) and at a second end section which is closer to the outer wall (116; 216) of the storage body (112; 212). [4] Storage unit (100; 200) according to one of the preceding claims, wherein the storage body (112; 212) is made of a metallic material, preferably a titanium alloy. [5] Storage unit (100; 200) according to one of the preceding claims, wherein the storage unit (100; 200) is designed for a maximum pressure of more than 200 bar, preferably more than 400 bar, more preferably more than 800 bar, and more preferably more than 1200 bar. [6] Storage unit (200) according to one of the preceding claims, which further comprises an additional reinforcement structure (232) which is formed within the storage volume (214) of the storage unit (200) and is connected at least at one point to the inner wall (218) of the storage body (212). [7] Storage unit (200) according to the preceding claim, wherein the additional reinforcement structure (232) is designed as an integral one-piece structure. [8] Storage unit (100) according to one of the preceding claims, wherein the storage body (112) comprises a cover layer (130) which is formed on the outer and / or inner circumferential surface of the outer wall (116) of the storage body (112). [9] Storage unit (100; 200) according to the preceding claim, wherein the cover layer (130) of the storage body (112) is formed from a fiber composite material. [10] Storage unit (100; 200) according to the preceding claim, wherein the storage unit (100; 200) is a mobile storage unit designed for use in a means of transport. [11] Storage unit (100; 200) for storing fluids, in particular gaseous media, comprising a storage body (112; 212) which encloses a storage volume (114; 214) which is configured to receive a gaseous medium, and at least one connection (126, 128; 226) which is provided and configured to establish fluid communication between the storage volume (114; 214) and an exterior of the storage body (112; 212), wherein the storage body (112; 212) comprises: - an outer wall (116; 216) which defines an outer dimension of the storage body (112; 212), - an inner wall (118; 218) which is formed within the outer wall (116; 216) of the storage body (112; 212) and is designed to limit the storage volume (114; 214) to the outside, and - a reinforcement structure (120; 220) which is formed between the inner wall (118; 218) of the storage body (112; 212) and the outer wall (116; 216) of the storage body (112; 212), wherein the storage unit further comprises an additional reinforcement structure (232) which is formed within the storage volume (214) of the storage unit (200) and is connected at least at one point to the inner wall (218) of the storage body (212). [12] Method for additively manufacturing a storage unit (100; 200) according to any one of claims 1 to 11. [13] Method according to the preceding claim, wherein the method comprises a step of laser-based powder bed fusion of metals. [14] Fuel cell comprising a storage unit (100; 200) according to any one of claims 1 to 11.

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