Hydrogen is the most common chemical element found in the universe and has the potential as a clean energy source. Due to its reactivity, it does not exist in its pure form on earth. Hydrogen forms chemical compounds with other atoms in materials such as water, biomass, fossil fuels, or other minerals. The potential of hydrogen as a future energy source stems its energy reserve which contains more than twice as much energy as natural gas. It only requires oxygen as input for combustion and produces water as an output. Therefore, hydrogen produces zero greenhouse gas (GHG) emissions as a fuel source
If hydrogen produces only water as a by-product from combustion, it should be straightforward to utilize this form of energy to replace fossil fuels. However, many researchers face challenges to utilize hydrogen as an alternative for clean energy. One of the challenges is that hydrogen can only be used as a fuel source when it exists in its pure form. Therefore, hydrogen must be extracted from the materials such as coals, ammonia, methane, etc. The extraction process uses a huge amount of energy which may be more than the conventional fossil fuels for power generation. Eventually, this leads to higher emissions of GHG even when hydrogen is used as a fuel source.
Hydrogen can be color-coded based on the amount of emission it generates during production; green, blue, grey or brown hydrogen. The lighter color 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.
The hydrogen production process, whether via water electrolysis, gasification of solid fuels or methane steam reforming, needs a massive energy input to run the operation. Therefore, the energy required for these processes must also come from renewable sources such as solar, wind or hydroelectric power to achieve 100% zero-emission. Hydrogen can only be regarded as a clean energy source if its production processes do not generate GHG emissions or generate a much lower emission than the conventional fuel.
We have achieved significant breakthroughs in transitioning into a renewable future. It is now more likely that hydrogen systems will gain popularity in the future and enter commercialisation. However, there is still a challenge due to the issue in safe handling, transporting and storing of hydrogen. This is because Hydrogen is a very reactive element and can cause hydrogen embrittlement in any material. 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 the end-to-end supply chain. In storage tanks, hydrogen must be stored in pressurized tanks kept at a 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 losses to the operators and the customers.
Oil-filled piezoresistive pressure transmitters can be used for almost all pressure measurement applications due to their accuracy, robustness and reliability. Bringing in our sensor and measurement expertise, we propose the modification of gold-plated sensing diaphragm for hydrogen pressure measurement. This modification is necessary to address the issue of hydrogen poisoning and prevent the hydrogen gases to permeate through the diaphragm into the oil-filled cavity which will produce erroneous measurements. It is also necessary to prevent damaging the sensors from hydrogen-cracking mechanisms.
The gold-plated diaphragm pressure transmitters are suitable for hydrogen applications as hydrogen diffusivity through gold is far lower than 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 prevent contamination. The system can also be designed to be intrinsically safe with IECEx certification to suit hydrogen applications.
