Advanced solutions to improve the water management in electrochemical hydrogen compressors

Electrochemical hydrogen compressors (EHCs) have several advantages over mechanical compressors: they are vibration and noise free and can be very cost effective. Although suitable for applications in which low and moderate pressures are required, EHCs have one major drawback: the water management. To achieve good performance, the polymeric membrane must be optimally humidified. Without adequate humidification, the operating conditions can damage the membrane, affecting overall performance and efficiency
In this work, we present an EHC system in which the water management is controlled by a passive countercurrent membrane water exchanger. This device allows drying the produced hydrogen flow while simultaneously humidifying the low-pressure hydrogen fed to the compressor. This highly flexible drying system can achieve a dew point temperature of less than −30 °C. A dryer structured in this way avoids conventional drying methods such as TSA or PSA cycles, which are very demanding in terms of power and heat rejection. At the same time, it also avoids the use of conventional hydrogen humidification methods, which require expensive auxiliary equipment.
Several membrane electrode assemblies (MEAs) have been used in this study and the effect of their properties on the compression performance has been investigated. Current densities up to 4 A cm^-2 were achieved at low voltage and low temperature (up to 0.4 V and 35 °C), with pumped flows greater than 0.8 mg s^-1 [1]. The highest efficiencies (> 60) were achieved in a range of low voltages and current densities, but the efficiency of the EHC decreased dramatically as the voltage was increased. However, this condition is essential to achieve high current densities, which are converted into high compressed hydrogen flows. An optimum must therefore be found between performance and cost.
Nevertheless, the flexibility of this compressor, with its wide range of flow rates and total absence of vibration, should be highlighted. Indeed, such a system is suitable for aerospace applications (e.g., to produce cold energy in a Joule-Thomson cryocooler), but also for terrestrial hydrogen applications, such as injection into gas pipelines or storage in underground salt caverns.