Hydrogen energy and vehicle systems Preface Purpose and Audience Hydrogen shows great promise both as an energy carrier and as a fuel for transportation portable and stationary sources; however the expanded use of hydrogen as a renewable energy source raises a number of concerns and challenges that complicate planning efforts. Organizations are researching developing and validating hydrogen pathways to establish a business case for market implementation. However significant research and educational challenges still must be addressed. The use of hydrogen technologies addresses critical societal issues related to energy security stability and sustainability. First hydrogen may be produced from local resources thus eliminating the need for complex energy fuel supply lines. Second hydrogen used in conjunction with renewable energy sources provides a stable method of energy fuel production. Third hydrogen produced from renewable sources provides clean emission free energy fuel. Hydrogen technology constitutes a highly interdisciplinary field that extends from the fundamentals of materials electrochemical processes and fuel processing storage systems to complex design concepts for hybrid vehicles and renewable power fuel systems. Infrastructure analysis market transformation public policy safety and environment also play key roles. Additionally sustainable energy systems is an emerging field that aims to develop new and improved energy technologies systems and services while understanding the impact of energy on the economy and society. Hydrogen technology research encompasses traditional engineering disciplines (biological chemical electrical environmental geological material science mechanical systems) sciences (biology chemistry mathematics physics)