megawatt range. The systems can therefore be adapted flexibly to meet the requirements. Enapter’s AEM Nexus can be used in conjunction with small photovoltaic systems for applications in the private and commercial sector, but can also cover capacities on an industrial scale. The AEM electrolysers can therefore be used to produce green hydrogen on site that is adapted to the specific generation capacities, from wind or solar parks for example.
Purity measurement in the test system
Enapter set up a hydrogen production test system to evaluate the process used in the AEM electroylsers. Quality assurance of the hydrogen produced is of central importance in this test system. This is because the purity of 99.999% hydrogen required in various applications must be measured as impurities can impair the quality and performance of the gas. Oxygen and residual moisture in particular can influence the chemical reactivity if hydrogen is used as a raw material or carrier gas. Impurities can cause adverse secondary reactions, inefficient processes, damage to systems and safety hazards. Verification of the gas quality ensures that the hydrogen produced complies with the required specifications and that the method used by Enapter works.
Determining residual moisture and trace oxygen
The required measurement accuracy poses a considerable challenge to the measuring technology used. The devices used for gas analysis must be able to reliably detect minimum
levels of impurity. Here, Enapter uses Endress+Hauser’s optical analysis measuring technology to determine hydrogen purity. Enapter opted for a solution to measure the purity since the instrumentation and automation supplier not only provides the measuring technology but also the relevant expertise to develop the solution. The core component of the quality measurement consists of a combined solution with the J22 TDLAS gas analyser and OXY5500 oxygen analyser, with a shared sample conditioning system to determine trace moisture and trace oxygen. For optimised process control, the quality measurement should be performed very quickly, if possible, in real time, which was taken into account during the planning and development phase. To implement the measurement with the required accuracy, the solution was developed in collaboration with the Endress+Hauser centre of competence for gas analysis in Lyon, France, and tailored to meet Enapter’s requirements.
Seamless interaction between all measuring points
A number of other measuring points for the pressure, conductivity, temperature and flow parameters are also installed in the test plant. Endress+Hauser devices were selected for these measuring points to ensure optimum interaction with the analytical measuring technology and automation technology used. The demands on the measuring technology are not only high for the hydrogen quality measurements – the other measuring points are also subject to the highest quality standards. A number of the measuring devices are in direct contact with the medium of hydrogen, placing very specific requirements on the design of the instruments and selection of materials. For example, the Cerabar pressure transmitter is fitted with a gold membrane to prevent hydrogen from diffusing through it and to protect the membrane from stress corrosion cracking. To accurately measure the flow rate, a single-tube Promass Coriolis flowmeter was selected to guarantee reliable and high-precision measurement of the lowest flow rates of hydrogen.
Driving the energy transition together
Figure 3. Panel solutions can determine trace moisture and oxygen in real time.
40
GlobalHydrogenReview.com
Summer 2024
In conclusion, it is very important to be able to rely on a partner who can provide support beyond gas analysis at all measuring points in order to ensure perfect interaction between all system components. The sensor technology discussed was developed and optimised in close cooperation and has proven results. Now that Enapter has had the opportunity to evaluate its test system and verify that the implemented process works, the megawatt-class AEM electrolyser, with a production capacity of up to 450 kg/d of green hydrogen, will be fitted with Endress+Hauser’s gas analysis solution to measure the hydrogen quality. Although the AEM electrolysis systems are still undergoing final tests, Enapter’s pre-series production is already underway. The single-core electrolysers are currently being built in Italy, while the multi-core systems are being assembled in Germany. With the completion of the production facility for AEM electrolysers in Saerbeck, Germany, the overall production capacity will then be significantly expanded.