(94f) P.E.M. Water Electrolyzers in Renewable Energy Capture to Hydrogen

Hydrogen by electrolysis from renewable energy (RE) sources such as PV and wind has great potential to be a cost competitive alternative to steam methane reformation or coal gasification production methods, while avoiding emissions of greenhouse gases. High pressure (HP) proton exchange membrane (PEM) electrolyte water electrolysis is especially conducive to distributed hydrogen generation options where the cost of transporting hydrogen can be prohibitive. PEM water electrolyzers scale from 1 to 500 kilograms per day capacity, and are environmentally benign, using only pure water as feedstock and working fluid, with no liquid electrolyte. Commercial hydrogen generators using PEM water electrolysis are well-proven and are currently serving industrial and energy applications worldwide in over 50 countries. Market and environmental requirements are converging to demand larger on-site hydrogen generators. Rising natural gas pricing, increasing trucking costs, developing economies with no liquid H2 infrastructure, utility load leveling, telecommunication power back-up, and forklift fuel cell fueling applications are all examples of market forces working to increase demand for on-site H2 generation. Intense international debate on global warming trends and the link to greenhouse gases from fossil fuels consistently cites energy from renewable sources as a ?must-do' pathway, yet the intermittent nature of solar and wind is often cited as a key drawback. PEM Water electrolysis is the best enabler to intermittent renewable sources such as PV and wind. It can be dispatched quickly to convert RE as it is available to gaseous hydrogen at pressure; this stored or pipeline-supplied hydrogen may then be converted at-will back to energy via fuel cell or engine when needed. There is a 17 TW (17,000,000,000,000 watts) carbon-free world energy gap projected by 2050. Distributed photovoltaic arrays and wind generators, enabled by distributed water electrolysis hydrogen generation and energy recovery fuel cells, all produced on a scale commensurate with today's automotive industry, may very well be the most compelling way to fill this gap. Vehicle fueling applications in the next 5-10 years may be well-satisfied with a 100 kg H2/day PEM hydrogen generator module; this platform is then the pathway towards the 500 kg H2/day module desired for hydrogen vehicle fueling stations, utility load-leveling, and renewables to hydrogen enablement. HP PEM units for reserve or backup power may be considerably smaller, as may individual vehicle fueling and home energy units. The latest and near-future commercially available distributed HP hydrogen generation using RE sources will be presented in this paper. Generation rate, efficiency, pressure, and power consumption of HP PEM electrolyzer systems will be discussed, with comparisons between high pressure electrolysis and mechanical compression of hydrogen to typical application and storage pressures made. Efforts already underway to scale-up a commercial 12 kg/day PEM hydrogen generator packaged product to a 100 kg/day product, then a 500 kg/day product, that meets commercial market cost targets, complies with new standards, and approaches transportation fueling cost targets, are discussed.