page_title: Hydrogen economy
section_title: Rationale
hierarchical_section_title: Hydrogen economy / Rationale
context_page_description: The hydrogen economy is the use of hydrogen as a low carbon fuel, particularly for heat; but also for hydrogen vehicles, seasonal energy storage and long distance transport of energy. In order to phase out fossil fuels and limit global warming, hydrogen is starting to be used as it can be created from water, and its combustion only releases water and no CO
  2 to the atmosphere. Hydrogen is a powerful fuel - indeed a frequent component in rocket fuel - but there exist numerous technical challenges preventing the creation of a working large-scale hydrogen economy. Among these include the difficulty of developing long-term storage, pipelines and engine equipment due to hydrogen embrittlement, a relative lack of off-the-shelf engine technology that can currently run safely on hydrogen, safety concerns due to the high explosiveness/reactivity of hydrogen fuel with environmental oxygen in the air, and a lack of efficient photochemical water splitting technology to provide sufficient fuel.
  The hydrogen economy is nevertheless slowly developing as a small part of the low-carbon economy.
context_section_description: In the current hydrocarbon economy, heating is fueled primarily by natural gas and transportation by petroleum. Burning of hydrocarbon fuels emits carbon dioxide and other pollutants. The demand for energy is increasing, particularly in China, India, and other developing countries. Hydrogen can be an environmentally cleaner source of energy to end-users, without release of pollutants such as particulates or carbon dioxide.
  Hydrogen has a high energy density by weight but has a low energy density by volume.  Even when highly compressed, stored in solids, 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. Hydrogen can help to decarbonize long-haul transport, chemicals, and iron and steel and has the potential to transport renewable energy long distance and store it long term, for example  from wind power or solar electricity.
caption: Elements of the hydrogen economy
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