Noninvasive Ultrasonic Level Measurement in High-Pressure Alkaline Electrolyzers

The cost-effective production of green hydrogen by water electrolysis is a key issue for the green energy transition. Although current commercial electrolyzers are mainly based on Polymer Electrolyte Membranes (PEM), Anion Exchange Membranes (AEMs) as an ongoing research topic offer the possibility of reducing the initial cost of the system by using nonprecious materials. Subsequently, high-pressure AEM electrolysis decreases the need for mechanical compression. This offers further reduction of initial and operational costs. Subsequently, high-pressure AEM electrolysis offers further reduced initial and operational costs by decreasing the need for mechanical compression. Here, hydrogen is produced at up to $\mathbf{1 0 ~ M P a}$ while the oxygen electrode with the aqueous electrolyte remains at ambient pressure. However, the removal of water vapor and small droplets from the produced hydrogen gas at this high gas pressure is challenging because sensors for level control introduce complexity in regard to tightness and integrity of the system. Therefore, a noninvasive measurement technique to capture the electrolyte level in a liquid separator has been investigated, that can be implemented downstream of a high-pressure electrolyzer. Using an ultrasonic transmitter on the outside of a stainless steel pressure cylinder and a receiver on the opposite side allows level detection. This assembly does not influence the integrity of the pressure cylinder up to $\mathbf{1 0 ~ M P a}$ and enables low-cost level detection by implementation of excitation and analysis on a microcontroller.