Friday, December 9, 2011

Comparison Hydrogen vehicles with other types of alternative fuel vehicle

Hydrogen vehicles are one of a number of proposed alternatives to the modern fossil fuel powered vehicle infrastructure.

[edit]Plug-in hybrids

Plug-in hybrid electric vehicles, or PHEVs, are hybrid vehicles that can be plugged into the electric grid and contain an electric motor and also an ICE or other engine. The Chevrolet Volt, the first commercially-manufactured PHEV, became commercially available in some U.S. states in 2010 and in more locations in 2011. The PHEV concept augments standard hybrid electric vehicles with the ability to recharge their batteries from an external source while parked, enabling increased use of the vehicle's electric motors while reducing their reliance on internal combustion engines. The infrastructure required to charge PHEVs is already in place,[81] and transmission of power from grid to car is about 93% efficient.[82] This, however, is not the only energy loss in transferring power from grid to wheels. AC/DC conversion must take place from the grids AC supply to the PHEV's DC. This is roughly 98% efficient.[83] The battery then must be charged. As of 2007, the Lithium iron phosphate battery was between 80-90% efficient in charging/discharging.[84] The battery needs to be cooled; the GM Volt's battery has 4 coolers and two radiators.[85] As of 2009, "the total well-to-wheels efficiency with which a hydrogen fuel cell vehicle might utilize renewable electricity is roughly 20% (although that number could rise to 25% or a little higher with the kind of multiple technology breakthroughs required to enable a hydrogen economy). The well-to-wheels efficiency of charging an onboard battery and then discharging it to run an electric motor in a PHEV or EV, however, is 80% (and could be higher in the future)—four times more efficient than current hydrogen fuel cell vehicle pathways."[49] A 2006 article in Scientific American argued that PHEVs, rather than hydrogen vehicles, would become standard in the automobile industry.[86][87] A December 2009 study at UC Davis found that, over their lifetimes, PHEVs will emit less carbon than current vehicles, while hydrogen cars will emit more carbon than gasoline vehicles.[76]

[edit]Natural gas

ICE-based CNG or LNG vehicles (Natural gas vehicles or NGVs) use Natural gas or Biogas as a fuel source. Natural gas has a higher energy density than hydrogen gas. Natural gas powered vehicles have a lower carbon dioxide footprint than ICE vehicles. When using Biogas, NGVs become carbon neutral vehicles that run on animal waste.[88] CNG vehicles have been available for several years, and there is sufficient infrastructure to provide both commercial and home refueling stations. In 2008, the ACEEE rated the Honda Civic GX, which uses compressed natural gas, as the greenest vehicle available.[89][90][91]

[edit]Battery electric vehicles

A 2008 Technology Review article stated, "Electric cars—and plug-in hybrid cars—have an enormous advantage over hydrogen fuel-cell vehicles in utilizing low-carbon electricity. That is because of the inherent inefficiency of the entire hydrogen fueling process, from generating the hydrogen with that electricity to transporting this diffuse gas long distances, getting the hydrogen in the car, and then running it through a fuel cell—all for the purpose of converting the hydrogen back into electricity to drive the same exact electric motor you'll find in an electric car."[92] Thermodynamically, each additional step in the conversion process decreases the overall efficiency of the process.[93][94] Many BEV designs offer limited driving range. For example, The Nissan Leaf, the first commercially-manufactured BEV, which became available in in some U.S. states beginning in 2010, has a maximum range of 100 miles. Mini Eusers have reported a range of between 100–120 miles (160–190 km).[95] However, most commutes are 30–40 miles (48–64 km) miles per day round trip. Ed Begley, Jr., an electric car advocate, noted wryly, "The detractors of electric vehicles are right. Given their limited range, they can only meet the needs of 90 percent of the population."[49] In addition, new Nickel-metal hydride and lithium batteries are non-toxic and can be recycled, and "the supposed 'lithium shortage' doesn't exist".[49]

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