Efficiency As An Automotive Fuel
Hydrogen has been called one of the least efficient and most expensive possible replacements for gasoline (petrol) in terms of reducing greenhouse gases; other technologies may be less expensive and more quickly implemented. A comprehensive study of hydrogen in transportation applications has found that "there are major hurdles on the path to achieving the vision of the hydrogen economy; the path will not be simple or straightforward". Although Ford Motor Company and French Renault-Nissan cancelled their hydrogen car R&D efforts in 2008 and 2009, respectively, they signed a 2009 letter of intent with the other manufacturers and Now GMBH in September 2009 supporting the commercial introduction of FCVs by 2015.
An accounting of the energy utilized during a thermodynamic process, known as an energy balance, can be applied to automotive fuels. With today's technology, the manufacture of hydrogen via steam reforming can be accomplished with a thermal efficiency of 75 to 80 percent. Additional energy will be required to liquefy or compress the hydrogen, and to transport it to the filling station via truck or pipeline. The energy that must be utilized per kilogram to produce, transport and deliver hydrogen (i.e., its well-to-tank energy use) is approximately 50 megajoules using technology available in 2004. Subtracting this energy from the enthalpy of one kilogram of hydrogen, which is 141 megajoules, and dividing by the enthalpy, yields a thermal energy efficiency of roughly 60%. Gasoline, by comparison, requires less energy input, per gallon, at the refinery, and comparatively little energy is required to transport it and store it owing to its high energy density per gallon at ambient temperatures. Well-to-tank, the supply chain for gasoline is roughly 80% efficient (Wang, 2002). The most efficient distribution however is electrical, which is typically 95% efficient. Electric vehicles are typically 3 to 4 times as efficient as hydrogen powered vehicles.
A study of the well-to-wheels efficiency of hydrogen vehicles compared to other vehicles in the Norwegian energy system indicates that hydrogen fuel-cell vehicles tend to be about a third as efficient as EVs when electrolysis is used, with hydrogen Internal Combustion Engines (ICE) being barely a sixth as efficient. Even in the case where hydrogen fuel cells get their hydrogen from natural gas reformation rather than electrolysis, and EVs get their power from a natural gas power plant, the EVs still come out ahead 35% to 25% (and only 13% for a H2 ICE). This compares to 14% for a gasoline ICE, 27% for a gasoline ICE hybrid, and 17% for a diesel ICE, also on a well-to-wheels basis.
Read more about this topic: Hydrogen Economy
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