Hydrogen economy

The hydrogen economy is the use of hydrogen as a low carbon fuel, particularly for heating, hydrogen vehicles, seasonal energy storage and long distance transport of energy. The hydrogen economy is the use of hydrogen as a low carbon fuel, particularly for heating, hydrogen vehicles, seasonal energy storage and long distance transport of energy. The hydrogen economy is proposed as part of the future low-carbon economy. In order to phase out fossil fuels and limit global warming, hydrogen is being considered as its combustion only releases clean water, and no CO2 to the atmosphere. As of 2019, however, hydrogen is mainly used as an industrial feedstock, primarily for the production of ammonia, methanol and petroleum refining. Hydrogen gas does not occur naturally in convenient reservoirs. As of 2019 almost all the world's hydrogen is produced by steam methane reforming (SMR). The remainder is produced as a byproduct from electrolysis processes such as chlor-alkali. Small amounts of hydrogen are produced by the dedicated production of hydrogen from water. The production of hydrogen from both the natural gas steam reforming process and the dedicated water electrolysis process are hampered by unavoidable efficiency issues. As of 2019 there is not enough cheap clean electricity (renewable and nuclear) for hydrogen to become a significant part of the low-carbon economy, and carbon dioxide is a by-product of the SMR process. A hydrogen economy was proposed by the University of Michigan to solve some of the negative effects of using hydrocarbon fuels where the carbon is released to the atmosphere (as carbon dioxide, carbon monoxide, unburnt hydrocarbons, etc.). Modern interest in the hydrogen economy can generally be traced to a 1970 technical report by Lawrence W. Jones of the University of Michigan. In the current hydrocarbon economy, transportation is fueled primarily by petroleum and heating by natural gas. Burning of hydrocarbon fuels emits carbon dioxide and other pollutants. The demand for energy is increasing, particularly in China, India, and other developing countries. Proponents of a world-scale hydrogen economy argue that hydrogen can be an environmentally cleaner source of energy to end-users, without release of pollutants such as particulates or carbon dioxide. A 2004 analysis asserted that 'most of the hydrogen supply chain pathways would release significantly less carbon dioxide into the atmosphere than would gasoline used in hybrid electric vehicles' and that significant reductions in carbon dioxide emissions would be possible if carbon capture or carbon sequestration methods were utilized at the site of energy or hydrogen production. Hydrogen has a high energy density by weight but has a low energy density by volume. Even when highly compressed or liquified, the energy density by volume is only 1/4 that of gasoline, although the energy density by weight is approximately three times that of gasoline or natural gas. An Otto-cycle internal-combustion engine running on hydrogen is said to have a maximum efficiency of about 38%, 8% higher than a gasoline internal-combustion engine. The combination of the fuel cell and electric motor is 2-3 times more efficient than an internal-combustion engine. Capital costs of fuel cells have reduced significantly over recent years, with a modeled cost of $50/kW cited by the Department of Energy. Previous technical obstacles have included hydrogen storage issues and the purity requirement of hydrogen used in fuel cells, as with current technology, an operating fuel cell requires the purity of hydrogen to be as high as 99.999%. Hydrogen engine conversion technology could be considered more economical than fuel cells.