Hydrogen Overview – Hydrogen is the lightest and most abundant element in the universe.In its pure form (H2), it is a colorless and odorless gas. However, since it combines easily with other elements, hydrogen is rarely found by itself in nature and is usually found as a part of other compounds, including fossil fuels, plant material, and water. Hydrogen is an energy carrier, not an energy source, meaning that it stores and delivers energy in a usable form. Like electricity, the most familiar energy carrier, it can be generated from a wide range of sources.
Hydrogen Production – Hydrogen can be produced using a variety of domestic energy resources -fossil fuels, such as coal and natural gas, with carbon capture and sequestration; renewables, such as biomass; electricity from renewable energy technologies, including solar, wind, geothermal, and hydropower; and thermal energy or electric power from nuclear.
Hydrogen Delivery – Since it can be produced from several sources and using various methods, hydrogen can be produced at large production plants and transported to users. It can also be produced locally, using small generators, possibly at refueling stations, eliminating the need for long-distance transport. Hydrogen is currently transported by road via cylinders, tube trailers, cryogenic tankers, and in pipelines. However, hydrogen pipelines currently only exist in a few regions of the United States. The delivery infrastructure for hydrogen will require high-pressure compressors for gaseous hydrogen and liquefaction for cryogenic hydrogen. Both currently have significant capital and operating costs, and energy inefficiencies.
Hydrogen Storage – Finding a cost-effective method of storing hydrogen on a vehicle is a challenge. While hydrogen contains more energy per weight than any other energy carrier, it contains much less energy by volume. Hydrogen may be stored as a liquid, a high pressure gas, or by chemical methods; all are under intense development.
Weight and Volume: The weight and volume of hydrogen storage systems are presently too high, resulting in inadequate vehicle range. Materials and components are needed that allow compact, lightweight, hydrogen storage systems while enabling greater than 300-mile range in all light-duty vehicle platforms.
Efficiency: Energy efficiency is a challenge for all hydrogen storage approaches. The energy required to get hydrogen in and out is an issue for reversible solid-state materials. Life-cycle energy efficiency is a challenge for chemical hydride storage in which the by-product is regenerated off-board. In addition, the energy associated with compression and liquefaction must be considered for compressed and liquid hydrogen technologies.
Cost: The cost of on-board hydrogen storage systems is high, particularly in comparison with conventional storage systems for petroleum fuels. Low-cost materials and components for hydrogen storage systems are needed, as well as low-cost ,high-volume manufacturing methods.
Codes & Standards: Applicable codes and standards for hydrogen storage systems and interface technologies, which will facilitate implementation/commercialization and assure safety and public acceptance, are being established. Standardized hardware, operating procedures, and applicable codes and standards, are required.
Source: U.S. Dept of Energy