This Small Business Innovation Research Phase II project addresses current limitations in hydrogen compression and enables reduction in hydrogen requirements for several applications through recycling of exhaust hydrogen containing water and other benign impurities. In Phase 1, feasibility of operating a proton exchange membrane (PEM)-based device as a high efficiency electrochemical compressor/purifier was demonstrated at up to 3 A/cm2. In Phase 2, refinement of the microporous plate will be performed for optimal water distribution, which will enable more uniform fluid distribution and high current densities. Poison-tolerant catalysts will also be developed to enable a broader range of applications. The objectives of this phase also include additional test stand modifications to enable a broader range of test conditions, demonstration of gas purity through analysis to determine the separation efficiency, and development of system schematics and product requirements. The anticipated result will be an improved hydrogen recycler which will enable substantial reduction in hydrogen production cost and new market opportunities.
The broader impact/commercial potential of this project includes applications ranging from power plants to heat treating to backup power and fueling. For example, over 16,000 power plants worldwide use hydrogen as a cooling fluid in the turbine windings. Currently, increases in dew point cause significant decreases in cooling efficiency and increase windage losses by several percent, requiring purging of the hydrogen chamber and increased production to backfill. Thus, significant energy waste is generated. Current solutions for hydrogen compression are also noisy, bulky, and inefficient. In applications where hydrogen is being evaluated as an alternative fuel, high pressure storage is needed. Having a mechanical compressor that represents half of the size and material cost of a home fueling or backup power device is not commercially feasible. The device proposed has the opportunity to decrease the energy required to produce pure hydrogen by 75% over generating additional hydrogen from water, and to compress the hydrogen with as little as 200 mV of overpotential even at high current density. Advances in these areas would find immediate commercial interest, and address key strategic areas on the government agenda related to energy savings and green technology.
In Phase 1 of this project, Proton Energy Systems, Inc. d/b/a Proton OnSite ("Proton") demonstrated feasibility of recycling and compressing waste hydrogen for high purity applications via an electrochemical pump. Proton collaborated with industrial partners to compare operating characteristics between two different cell configurations of a proton exchange membrane (PEM) electrochemical pump. The industrial collaborators provided test materials for the humidification plate which were incorporated into Proton cell designs for test. Significant performance improvement was demonstrated over the baseline cell in both two-chamber (no humidification plate) and three-chamber (with humidification plate) cell configurations. Over the course of the 2-year Phase 2 program, significant progress was made in advancing electrochemical pump cell technology. The cell configuration was further refined and a final configuration selected to support testing. The selected configuration incorporated flow field components with significant cost reduction potential in commercial cell applications. Several challenges related to catalyst synthesis techniques were overcome to enable catalyst testing in product scale cells. A number of promising pathways that merit further exploration have been opened up related to both binary and ternary catalyst compositions. Furthermore, with the first attempts to incorporate CO-tolerant catalyst into scaled-up Proton cells completed, future work can address more detailed parameters regarding electrode structure as well as operating conditions for cells operating with mixtures containing CO. Durability testing with pure hydrogen and mixtures of hydrogen and inert gas exceeded 1000 hours of operation. The cell configuration was tested with a number of flow conditions from zero excess flow to 25% excess flow, and the humidification of the input stream was varied from condensing to sub-saturated with very consistent performance. In defining one key application for the electrochemical pump as a hydrogen recovery device to be integrated with electrolysis products using pressure swing adsorption (PSA) dryer, PSA dryer purge streams were characterized with modeling and experimentation. Experiments gathered data on contaminants within as well as the temperature and pressure profile of the purge stream during normal PSA dryer function. A detailed system design was completed to enable an integrated dryer recovery prototype system to be fabricated based on the design documentation produced during the project. An energy analysis based on measured compressor cell performance was favorable for the device to be integrated with electrolysis systems and lead to an increase in overall system efficiency. Therefore, the results of this project have significant impact in enabling hydrogen recovery from a number of industrial and energy systems where hydrogen waste is a significant factor. Hydrogen streams contaminated by processes with hydrocarbons and other impurities can be recovered and purified. Hydrogen streams that get reduced from high to low quality (through depressurization and increased water content) can be recovered and returned to high pressure to enable higher electrolysis product output or efficiency. As a result of this work, pump cell performance was fundamentally characterized and the feasibility of a real dryer purge recovery module with product implications was established.
