Sustainability aspects of hydrogen and fuel cell systems

The contributions to sustainability of hydrogen and fuel cell systems are described, with the intention of providing a good understanding of the role hydrogen is expected to play in sustainable energy systems. It is demonstrated how the benefits and sustainability attributes of hydrogen systems can be observed using thermodynamics, life cycle assessment and other methods, and that hydrogen fuel cell systems can play a significant role, particularly by facilitating the use of renewable energy and by increasing efficiency. The usefulness of exergy methods for enhancing the efficiency and sustainability of hydrogen energy systems is also described. The importance of hydrogen energy and fuel cell systems in mitigating environmental impacts, including climate change, is highlighted throughout. Two illustrations are presented, one covering an efficiency assessment of a PEM fuel cell, and the other a life cycle assessment of fuel cell vehicles. The largest energy consumption for an internal combustion engine vehicle is in the usage stage. Energy consumption for PEM fuel cell vehicles in use is several times smaller. On a life cycle basis, energy consumption and greenhouse gas emissions of the PEM fuel cell are less than half those for the internal combustion engine vehicle. These results can vary depending on the source of hydrogen. The results are expected to be useful to scientists, researchers and engineers as well as policy and decision makers. (C) 2011 International Energy Initiative. Published by Elsevier Inc. All rights reserved.