Analysis of internal behavior of electrochemical hydrogen compressors at high pressures

Abstract

We examined the internal behavior of an electrochemical hydrogen compressor under high-pressure conditions. In doing so, we focused on the changes in compressor efficiency and power consumption in response to intensified hydrogen back-diffusion under high pressures and various values of other parameters. First, as the operating temperature increased, the power consumed to achieve the same pressure ratio increased. This increased in power consumption was attributed to the fact that as the temperature increased, hydrogen back-diffusion intensified, which necessitated a net forward flux and induced flow losses. Second, as the relative humidity increased, power consumption decreased, and compressor efficiency increased. Although higher relative humidity intensifies back-diffusion, leading to flow losses, the accompanying significant decrease in ohmic losses increases compressor efficiency. By adjusting factors such as temperature and relative humidity, compressor efficiency can potentially be increased by up to 1.78 times. At high pressure ratios, hydrogen back-diffusion was inherently strong, and it became stronger at higher temperatures and relative humidities. Therefore, the compressor was more efficient when it was operated at lower temperatures and higher relative humidities. At the optimal operating temperature of 50 °C and 100 % relative humidity, the compressor efficiency peaked at 97.507 % when the pressure ratio was 100.