STORAGE TANK FOR GASEOUS HYDROGEN

Abstract

A storage tank for storing gaseous hydrogen comprises a boundary wall having a laminate composite structure which includes a resin-rich layer forming an internal surface of the boundary wall, a glass-fibre composite layer in contact with the resin-rich layer and a carbon fibre composite layer in contact with the glass-fibre composite layer on a side thereof remote from the resin-rich layer. The laminate structure provides a high level of hydrogen impermeability and resistance to micro-cracking as a result of pressure cycling, providing the tank with a gravimetric efficiency appropriate to aeronautical applications.

Claims

1. A storage tank for storing gaseous hydrogen, the gas storage tank comprising a boundary wall having a laminate composite structure which includes a resin-rich layer forming an internal surface of the boundary wall, a glass-fibre composite layer in contact with the resin-rich layer and a carbon fibre composite layer in contact with the glass-fibre composite layer on a side thereof remote from the resin-rich layer.

2. A storage tank according to claim 1, wherein the laminate composite structure comprises a first carbon fibre composite layer in contact in contact with the glass fibre composite layer and a second carbon fibre composite layer in contact with the first carbon fibre composite layer on a side thereof remote from the glass fibre composite layer, and wherein the ply thickness of the second carbon fibre composite layer is greater than the ply thickness of the first carbon fibre composite layer and the thickness of the second carbon fibre composite layer is greater than the thickness of the first carbon fibre composite layer.

3. A storage tank according to claim 2, further wherein the laminate composite structure comprises a protective layer in contact with the second carbon fibre composite layer on a side thereof remote from the first carbon fibre composite layer.

4. A storage tank according to claim 3, wherein the protective layer is either a layer of elastomeric material or a layer of a glass fibre composite material system.

5. A storage tank according to claim 1, further comprising a toughening material encapsulated within one or more layers of the laminate composite structure.

6. A storage tank according to claim 1, further comprising a membrane material within one or more layers of the laminate composite structure.

Description

DESCRIPTION OF THE DRAWINGS

[0011] Examples are described below with reference to the accompanying drawings in which:

[0012] FIG. 1 shows a longitudinal section of a storage tank for storing gaseous hydrogen.

[0013] FIG. 2 shows the structure of a portion of the boundary wall of the FIG. 1 tank.

DETAILED DESCRIPTION

[0014] FIG. 1 shows a tank 10 for storage of gaseous hydrogen at high pressure, for example 300 bar or more. The tank 10 comprises a cylindrical central section 12 and two hemispherical end portions 14, 16 formed by a boundary wall 11. A metal fitting 18 passing through the boundary wall 11 at hemispherical end portion 14 allows filling and emptying of the tank 10.

[0015] FIG. 2 shows the structure of a portion 100 of the boundary wall 11 of the tank 10 of FIG. 1, the structure of the boundary wall 11 being substantially the same at all positions around the wall 11. The boundary wall 11 has a laminate composite structure and has inner and outer surfaces 101, 103 respectively. The inner most layer 102 of the boundary wall is a resin-rich layer which provides a high-quality layer which remains substantially free of void and cracks under pressure and temperature cycling and which therefore provides a layer of low permeability for hydrogen stored within the tank 10. The resin-rich layer 102 provides the internal surface 101 of the boundary wall 11 and is supported on a glass-fibre composite layer 104. Glass fibres within layer 104 have a strain behaviour that is closer to the performance of the matrix surrounding the glass fibres than is the case for carbon fibres within carbon fibre composite material, so that incidence of fibre/matrix failure due to micro-cracking is lower for the layer 104 than would be the case for a carbon-fibre composite layer when the tank 10 is subjected to pressure cycling. Glass-fibre composite layer 104 therefore provides a higher degree of resistance to hydrogen leakage than would be the case for a carbon-fibre composite layer.

[0016] Layers 106, 108 are carbon-fibre composite layers of relatively lower and higher ply thickness respectively. Layer 106 is thinner than layer 108. A low ply thickness layer gives a superior structural performance compared to a layer of high ply thickness but is more time-consuming to lay down. Layer 108 provides support for layers 106, 104, 102 and provides the boundary wall 11 with suitable stiffness and resistance to pressure loading when the tank 10 is filled with gaseous hydrogen. Layer 108 has a relatively high ply thickness compared to layer 106 and can therefore be laid down at a faster rate and with lower cost compared to layer 106. Layers 106, 108 can therefore be optimised to provide a required performance in terms of cost, speed of manufacture and hydrogen permeability performance.

[0017] Layer 110, which provides the external surface 103 of the boundary wall, is an outer protective layer which may be a layer of elastomeric material or a layer of a glass-fibre composite material system.

[0018] Toughening materials, such as nano-clay, may optionally be encapsulated within one or more of the layers 102, 104, 106, 108, 110 to allow a reduction in the thickness of those layers and hence a reduction in the weight of tank 10.

[0019] Membrane materials may be dispersed through the layers of boundary wall 11 to reduce or prevent permeation of hydrogen gas from the inner surface 101 to the outer surface 103 of the boundary wall 11 of the tank 10.

[0020] The laminate boundary wall 11 provides micro-cracking resistance and hydrogen impermeability functionality towards the inner boundary 101 (layers 102,104, 106) and more structural, cheaper and faster deposition forms towards the outer boundary 103 (layers 108, 110). The tank 10 therefore has the required resistance to pressure cycling and hydrogen impermeability without having excessive weight and is therefore suitable for civil aviation applications.