Measurement challenges in hydrogen energy pathway
Hydrogen is the most common chemical element found in the universe and has a great potential as a clean source of energy. On earth, it exists not in its pure form, but rather as part of other compounds such as water, biomass, fossil fuels or other types of minerals. As a potential energy source, hydrogen contains more than twice as much energy as natural gas, only requires oxygen as an input and produce water as an output. Therefore, hydrogen produces zero greenhouse gas (GHG) emissions as a fuel source.
The problem lies in utilisation of hydrogen as energy source as it can only be used for energy generation when it exists in its pure form. Therefore, hydrogen must be extracted from the materials and compounds listed above, using different extraction processes which may or may not produce GHG emission. If it does, hydrogen is not that clean as a fuel source.
Hydrogen can be colour-coded based on the amount of emission it generates during the extraction process; green, blue, grey or brown hydrogen. The lighter colour indicates the least amount of emission generated, and vice versa. Green hydrogen will play an increasingly significant role in the coming phases of the energy transition but it is an extremely costly process and cannot yet be scaled to commercial-size plants for widespread energy generation. Blue hydrogen pathway generates hydrogen from methane steam reforming process, generating GHGs which are then treated via capture and storage technologies.
Hydrogen extraction needs a massive energy input to run the operation. Therefore, the energy requirement must also come from renewable sources such as solar, wind or hydroelectric power to achieve 100% zero emission. Hydrogen can only be regarded as clean energy source if its production processes do not generate GHG emission.
If clean hydrogen production can be commercialised, transitioning to 100% hydrogen energy pathway is still a challenge due to the issue in safe handling, transporting and storing hydrogen. This is because hydrogen is a very reactive element and can cause hydrogen embrittlement in any materials. Therefore, materials used to construct equipment that come into contact with hydrogen must meet a strict control requirement.
Pressure transmitters are used at every measurement point during production and end-to-end supply chain. In storage tanks, hydrogen must be stored in pressurised tanks kept at certain pressure, either 350 bar or between 700 and 900 bar. The storing pressure will indicate where the hydrogen will be used. Therefore, it is crucial to ensure that the pressure is accurately monitored as measurement errors can cause significant loss to the operators and the customers.
Our oil-filled piezoresistive pressure transmitters can be used for almost all pressure measurement applications due to their accuracy, robustness and reliability. However, they have to be modified with gold-plated diaphragm for hydrogen pressure measurement applications to address the challenge with hydrogen poisoning. The high permeability of hydrogen gases allows it to seep through the stainless-steel diaphragm which will generate erroneous measurement and may damage the sensors beyond repair due to hydrogen-induced cracking mechanism.
The gold-plated diaphragm pressure transmitters are suitable for hydrogen applications as hydrogen diffusivity through gold is far lower compared to stainless steel. The inside of the pressure transmitters is also fully welded and metallically bonded to isolate parts of the transmitters that are in contact with hydrogen from the rest of the systems.
For cleaning and maintenance, oil and grease-free solutions can be used to prevent contamination. The system can also be designed to be intrinsically safe with IECEx certification to suit hydrogen applications.
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