Direct Electrochemical Compression of Hydrogen and Oxygen Via PEM Water Electrolysis 

Thursday, 5 October 2017: 11:20
National Harbor 15 (Gaylord National Resort and Convention Center)
K. E. Ayers, L. Dalton, and M. Parker (Proton OnSite)
One of the biggest challenges in applying hydrogen to energy storage and vehicle fueling applications is to efficiently store the hydrogen in a small volume with high reliability equipment. High pressure hydrogen applications that are used at a high duty cycle, including vehicle fueling demonstrations, repeatedly show that mechanical compression is one of the highest maintenance devices in the system. Electrochemical compression requires no moving parts within the cell, resulting in less maintenance due to wear, and also is highly efficient, with very low voltage penalty. The primary efficiency loss in electrochemical compression of hydrogen at high pressure is due to back diffusion of the compressed gas to the other cell chamber. Still, the overall efficiency still competes very well with mechanical compression to thousands of psi, as will be shown in this talk.

Proton exchange membrane (PEM)-based electrolysis enables combining the generation of hydrogen through water-splitting with the direct electrochemical compression of the gas. These membrane-based systems also have the advantage that they are capable of differential pressure operation. While there are applications for both pressurized oxygen and hydrogen, the differential pressure capability is especially attractive for generating high pressure hydrogen while maintaining the water-oxygen loop at ambient pressure, due to the inherent safety risks of high pressure oxygen.

Proton OnSite, the market leader in PEM electrolysis, has been increasing the proven output pressure of PEM electrolyzer devices, with demonstration of 350-bar (5,000 psi) hydrogen generation and 250-bar (3600 psi) oxygen generation, both in full differential pressure mode (see Figure). The hydrogen cell stack has been scaled to a capacity of 4.5 kg/day and is certified to meet the relevant codes and standards. This talk will address the challenges and successes for both hydrogen and oxygen compression at Proton, and potential best fits for these technologies.