Hydrogen Transitions in a Greenhouse Gas Constrained World Alison Bailie, 1 Bill Dougherty, 2 Sivan Kartha, 2 Michael Lazarus, 2 Chella Rajan, 3 and Benjamin Runkle 4 Abstract In order to realize the promise of a hydrogen economy in this United States, it is essential to couple it with a simultaneous commitment to improve energy efficiency and increase the use of renewable energy. In this study, using detailed scenario analyses for the country as a whole and for urban areas, we found that a large-scale switch to hydrogen produced by a clean energy system would lead to twice the environmental benefits compared to would be achieved in a hydrogen transition under a business-as-usual energy mentality. By 2050, when a “clean” transition to hydrogen would be nearly complete, greenhouse gas emissions would be roughly half of what they are today, compared to about a billion tons more, even with hydrogen produced from coal and natural gas. We found that introducing energy efficiency and renewable programs around the country early on will be important to pave the way for a hydrogen transition by freeing up some of the nation’s electricity, natural gas and coal infrastructure. Having broader energy goals, such as those established by greenhouse gas emission constraints that involve energy efficiency and the increased use of renewables, will actually make the hydrogen transition easier. 1 Introduction Hydrogen has captured the imagination of researchers, private investors, policy makers, and the general public. In an attempt to deal, once and for all, with the problems of energy insecurity, air pollution, and climate change - all of which are linked intimately to our oil economy - a wholesale recreation of the national energy system is now creeping into the energy agenda (Ogden, 1999; Rifken, 2002; Sperling and Cannon, 2004). Hydrogen, an energy carrier that can be produced from domestic zero-carbon sources and can be consumed in nearly zero-pollution devices, can potentially solve these problems. Energy security could be enhanced if hydrogen is produced from secure, abundant, domestic sources of energy such as wind, solar, biomass, and coal. Air pollution arising from our vehicles, buildings, and industries could be virtually eliminated as hydrogen is consumed in zero-pollution end-use devices. And climate change, the driving concern that motivated this study, could be affected as hydrogen made from close to zero-carbon sources for use in transportation and cogeneration could eliminate carbon emissions that come from using fossil fuels in vehicles, buildings, and industry. As an energy carrier, like electricity, hydrogen has applications in virtually any sector where it can be utilized by end-use devices to provide services. Much of current research and development interest is directed towards the conversion of hydrogen to electricity using fuel cells to provide motive power to run motor vehicles, although considerable attention is also paid to combined heat and power applications for residential, commercial and industrial sectors. As many have argued, however, the benefits of hydrogen are contingent on how, and from what sources, it is produced (Bossel et al, 2003; Romm, 2004; Demirdoven and Deutsch, 2004). 1 Pembina Institute, Calgary, Canada 2 Stockholm Environment Institute – US Center, Boston Massachusetts 3 Tellus Institute Boston Massachusetts 4 University of California, Berkeley 1