Hydrogen is an attractive fuel for vehicles powered by fuel cells, but its transport and storage presents challenges.
The technical issues in using hydrogen as a fuel are that, although hydrogen can be transported by pipelines, hydrogen tends to leak and can embrittle some metals used for pipelines, valves etc. Liquid hydrogen is a safety issue because it is cold enough to freeze air, and ice is often formed on components causing corrosion. Whichever route is selected, care is needed on materials selection to ensure compatibility with hydrogen at affordable cost.
For effective on-vehicle storage of gaseous hydrogen, pressure vessels are needed to store the gas at high pressure, probably in excess of 750 bar. Typical construction of these pressure vessels would use materials such as composites, stainless steel and hybrid systems.
Storage of hydrogen may also use novel approaches such as hydrides to store hydrogen gas, similar to a large chemical sponge. Here too there are numerous issues to resolve, not least in materials selection and quantification of hydrogen permeation rates and possible embrittlement effects.
To assist industry with these issues, TWI has installed a 1000 bar gaseous test facility capable of carrying out mechanical testing, fatigue and fracture tests in hydrogen and other gases. Major programmes of work are already underway for clients in Europe and Japan.
Results available from such testing are a valuable input to the selection of materials and fabrication routes which will provide reliable service at an affordable cost. TWI's experience with hydrogen compatibility issues over many years has proved valuable in helping clients understand the implications of the results from test programmes.
Although data exists for the performance of many materials in high pressure hydrogen gas, it is rare that this data includes the effects of fabrication, such as welding and joining. It is this lack of data, plus the search for less expensive material options, that is behind the reason for clients seeking the assistance of TWI in this area.
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