TMS, now AeroVironment, was directly involved in the development of air pressurization systems (APS) for PEM fuel cells. It produced 17 two-stage, inter-cooled, turbo compressor systems for a 250 kW Ballard stationary fuel cell application. The control system developed for this complex APS was programmed to automatically sequence and start the combustor, turbomachinery and required subsystems. After starting, the output pressure and flow were automatically controlled as a function of operator input.

Fifteen of the fuel cells were subjected to extensive field trials in several countries, including Germany, Switzerland, the Netherlands and Belgium. The objective was to achieve at least one full year's trouble free operation with each fuel cell. The first cell to achieve the objective has been dismantled for examination and evaluation and the turbo compressors returned to AeroVironment for inspection and reconditioning, if required. There were virtually no signs of wear after approximately 10,000 hours of operation and apart from varnish removal and cleaning of the seals and bearings, both units can be returned to service. The turbocharger system provided a peak compressor pressure ratio of over five to one with compressor efficiencies of up to 80% and turbine efficiencies approaching 86%. A titanium compressor impeller and Inconel turbine rotor were used to insure many years of service life.   

AeroVironment maintains an in-house, technology improvement program to continually upgrade the performance and manufacturability of its turbomachinery. In the Ballard fuel cell application AeroVironment’s staff and consultants worked to improve the overall efficiency of the APS turbocompressor, taking inot account compressor, turbine as well as bearing efficiencies, from 62 to 67 percent by optimizing the match between the compressor, turbine and fuel cell operating requirements. Performance testing of these turbocompressors in the AeroVironment turbocharger test facility demonstrated that these high efficiencies can be maintained over a wide operating range. These turbochargers are significantly more efficient than other small turbochargers currently available. Besides the two stages of turbo compressor, the AeroVironment system also includes an intercooler, a combustor, air start and automatic control system.