by Markus Schuster |
Hydrogen is a beacon of hope. Entire industries want to become climate-neutral with its help in the long term. Accordingly, demand is growing for the substance, which can be obtained by splitting water using electrical energy. Systems for cell voltage monitoring are also used in electrolysis. The process, electrolysis, is well known and proven. Alkaline water electrolysis has been used in the chemical industry for over 80 years. Monitoring the voltages in the individual cells of an electrolyser has not been an issue in all that time. With the increasing use of PEM electrolysis, this is changing and CVM systems are becoming an important part of the plants.
Hydrogen only contributes to achieving the climate goals if it is produced CO2-free. This means that electrical energy from renewable sources must be used. However, due to the weather, this energy is often available in a highly fluctuating manner, just think of wind power. The technology used for hydrogen synthesis must therefore be designed for dynamic operation. The tried-and-tested alkaline electrolysers are not, they react much too sluggishly and become more inefficient in partial-load operation. With PEM electrolysers it is different: they can be started up at short notice and also operated at partial load, so they can be adapted very flexibly to the fluctuating power profiles of renewable energies.
To ensure that the PEM electrolyser can be operated safely at all times, the voltages of the individual electrolysis cells must be kept in view. Each individual cell voltage must remain within a certain permissible voltage range. This is where our Cell Voltage Monitoring Systems come into play. Originally developed for use in PEM fuel cells in vehicles, they are also used in the electrolyser to extend the service life of the stack and to control the electrolysis process. Too high cell voltages mean too much corrosion and thus degradation of the materials. Currently, the voltages are around 2 volts, and research is working on reducing them further while simultaneously increasing pressure and current density. This would also increase the efficiency of a PEM electrolyser.
Actually, a PEM electrolyser is nothing more than a PEM fuel cell in which the process has been reversed. Instead of hydrogen becoming electricity and water, water and electricity become hydrogen. Accordingly, the construction is quite similar to that of a fuel cell. However, electrolysers can become much larger. With a typical cell voltage of 2 volts today, the insulation voltage limit is quickly reached. The CVM systems from SMART TESTSOLUTIONS have a tested insulation voltage of 1400 volts. Electrolysers with 600 cells are therefore no problem. For larger plants, several of our CVM systems are used.
Another big advantage of our CVM solutions is their compact design. This enables us to install the monitoring system in an ATEX-certified housing and thus address the issue of explosion protection. This is important because, after all, hydrogen and oxygen can form an explosive mixture if they mix unintentionally. ATEX is a certificate for equipment and machines that permits their use in a potentially explosive environment.
Are you planning an electrolyser and looking for ways to monitor the single-cell voltages? Then contact us. My colleague Wajih Wertateni is looking forward to your mail (firstname.lastname@example.org).