Hydrogen for energy storage
The variable nature of renewable energy is considered one of the greatest challenges in implementing the energy transition: Solar and wind sources cannot be regulated according to the needs of electricity customers at any given time. The development of workable and economic power storage technologies is therefore a decisive factor for success of the energy transition. Labom is at home both in the equipping of wind turbines in close cooperation with leading manufacturers and in the energy storage segment in terms of metrology.
Hydrogen plays a key role in the storage of surplus energy. Surplus energy from renewable energy sources can be used to produce hydrogen via electrolysis in order to store the energy. Hydrogen is also the initial medium for Power2X processes. Nevertheless, handling the smallest molecule in existence also presents a challenge: Hydrogen dissolves in numerous metals and is so small that it penetrates stainless steels and causes some types of steel to become brittle.
When hydrogen atoms migrate through metals, they disrupt the crystal lattice, causing the material of commonly used alloys to become brittle. Choosing the right material is therefore crucial. However, hydrogen-resistant stainless steels are precisely those that are less springy and therefore only have limited application in technology for pressure measurement. One solution can be an upstream diaphragm seal.
Hydrogen permeation through stainless steel
The hydrogen molecule decomposes into hydrogen atoms on the surface of metals and these can diffuse through metals: First the hydrogen molecules decompose into atoms, then the atoms migrate through the tetrahedral and octahedral gaps of the metal lattice and reunite as molecules on the other side. The whole process is called permeation (see illustration).
The rate of permeation depends on the temperature, pressure and material.
Relevance for pressure metrology
Diaphragm seals have a thin metal diaphragm on the process side. The pressure is transmitted to the sensor via the diaphragm and a filling liquid, usually oil. If hydrogen penetrates the membrane, it dissolves in the oil. Once saturation is reached, the hydrogen forms beads as the pressure is relieved and this leads to measurement errors such as shifting the zero point.
Depending on the process conditions, a diaphragm seal with a membrane made of hydrogen-resistant stainless steel, or a gold-plated membrane can be used. Labom has developed a tool to calculate the hydrogen permeation and the dissolution of hydrogen in the oil of the diaphragm seal. This is used to determine the service life and a custom robust system is recommended for each process. This makes it possible to use tried and tested Labom devices and benefit from their advantages such as easy operability as well as EX and SIL qualifications. → Labom Hydrogen Calculation Tool