Comparative Performance of Electrolysis Cell Stacks at the HSU Hydrogen Fueling Station

Since July 2008, the Schatz Energy Research Center (SERC) has operated a hydrogen fueling station on the campus of Humboldt State University.  The station was designed and built by SERC engineers and consists of a Proton Energy Systems HOGEN® S40 electrolyzer, a PDC single stage diaphragm compressor, two 6000 psig hydrogen storage tanks (with a 12 kg capacity) in a cascade configuration, and an FTI dispenser.  At present, the station is used to fuel an ICE Toyota Prius, retrofitted for hydrogen fuel by Quantum Technologies.  A second vehicle, a fuel cell powered Toyota Highlander, is expected to be added to our hydrogen fleet soon.

In an effort to accurately chronicle performance, we equipped the station with a data collection system that monitors a variety of operating parameters including the energy use of the compressor and electrolyzer, and the hydrogen output of the electrolyzer.  These measurements allow us to calculate efficiencies and to quantify operating costs during routine use at the station.  After nearly a year of data collection, we presented a paper¹ at the 2009 NHA conference describing the station’s performance, including our initial measurements of compressor and electrolyzer efficiencies.  The HOGEN® electrolyzer energy consumption we reported was 78 kWh/kg of hydrogen produced, in line with the average electrolyzer energy consumption of 73 kWh/kg, as reported by NREL for the DOE Technology Validation Project².

At the NHA conference, we discussed the electrolyzer efficiency with Proton Energy Systems, the unit’s manufacturer.  Proton offered to replace the current electrolyzer cell stack with a newer developmental model, designed for higher efficiency and lower cost.  This cell stack utilizes a bipolar plate architecture that reduces interfacial resistances while enabling a 70% part count reduction.  Additionally, Proton recommended installing a valve to partially bypass the heat exchanger, allowing the electrolyzer to run at a higher temperature.  We have installed the heat exchanger bypass and monitored the efficiency of the original electrolyzer cell stack at normal and elevated temperatures, as a benchmark of performance.  We will install the new cell stack, and collect similar data at both temperatures.  We will present these data on the original and new cell stacks’ performance and quantify the improvement produced with the new cell stack.  Additionally, we will discuss the effect of increased efficiency on overall station performance and quantify the energy and cost implications of these changes on hydrogen fueling stations in general.

¹ Allen, A., Lehman, P., Chapman, G. and C. Chamberlin. (2009) “Costs and Operational Data for the Humboldt State University Hydrogen Fueling Station,” presented at the National Hydrogen Association conference, Columbia, South Carolina, April 2, 2009.

² K. Wipke, National Renewable Energy Laboratory, "On-Site Hydrogen Production Efficiencies," DOE Hydrogen Technology Validation Program, personal communication, April 6, 2009.