Burned or used in fuel cells, hydrogen is an appealing option for powering future automobiles. This nontoxic gas could serve as a pollution-free energy carrier for machines of many kinds. When it burns, it releases no carbon .dioxide, a potent greenhouse gas. And if hydrogen is fed into a fuel cell stack a battery like device that generates electricity from hydrogen and oxygen it can propel an electric car or truck with only heat and water as by products. Fuel-cell powered vehicles could offer more than twice the efficiency of today's automobiles. Hydrogen could, therefore, help ease environmental problems, including air pollution and its hazards.
Weight for weight, hydrogen contains three times the energy of gasoline (petrol) but it is impossible to store hydrogen gas as compactly as the conventional liquid fuel. One of the most challenging technical issues is how to efficiently and safely store enough hydrogen onboard to provide the driving range and performance the motorists demand. Feasible storage devices hold sufficient hydrogen to support today's minimum acceptable travel (driving range--almost 500 kms)--on a fuel tank that does not compromise on luggage room. These tanks have to be filled or recharged in a few minutes. Lot many researchers in the U8 Internal Energy Agency are expending considerable effort to overcome these limitations. Infact, 17 governments are committed to advancing hydrogen and fuel-cell technologies. In 2005 the US Department of Energy provide4 $ 30 million to fund the 80 research projects.
A 500 km. minimum driving range is one of the principal operational aims of the auto industry. Engineers believe that a~allon of gasoline is equal,on an energy basis, to a kilogram of hydrogen.(One US gallon is almost 3.8 litres) Whereas today's automobile needs about 20 gallons of gasoline to travel 500 km.,the typical fuel-cell vehicle would need only 8 kilograms of hydrogen. Several automakers have tested about 60 hydrogen -fuelled prototypes and demonstrated driving ranges of 200 to 300 kms.
By 2010 some auto companies expect the first production of fuelcell cars to hit-the road. A hydrogen storage system must carry enough fuel for at least a 500 km trip and also be light enough to haul around a car. For a system weighing 600 kilograms (a reasonable~ size of a vehicle) ,six kgs. would be stored hydrogen. Liquified stored hydrogen can improve it's stored energy density and could be used in cars, it drawbacks notwithstanding. Neverthe less, One world-renowned carmakerBMW is pushing this technology onto the road. The vehicle called HYDROGEN-7 will incorporate an ,internal combustion engine capable of running on either gasoline for 500 Kms.or on liquid hydrogen for 250 kms.
Chemical compaction: to raise energy density scientists have been able to take advantage of the chemistry of hydrogen itself. In it~ liquid phase, hydrogen molecules contain two bound atoms each. But when hydrogen molecules are chemically bound to certain other elements, they can be packed even closer together than in liquid hydrogen.
Some researchers are focusing on a class of substances called reversible metal hydrides, which were discovered by accident in 1969 at the Philips Laboratories in the Netherlands. Investigators found that a Samarium-Cobalt alloy when exposed to pressurized hydrogen gas it would absorb hydrogen, somewhat like a sponge soaks up water. When the pressure was then removed ,the hydrogen within the alloy reemerged in other words, the process was reversible, In the US, scientists like Jame Reilly and Gary Sandrock,pioneered the development of hydride alloys. This work formed the basis for today's widely used Nickel-Metal hydride batteries.The density of hydrogen in these alloys is 150 % more than liquid hydrogen! Such properties of metal hydrides are well suited to automobiles. Although the current metal hydrides have limitations, many automakers see them as the most viable low-pressure approaching the near future. Toyota and Honda automotive engineers, are planning a so-called hybrid approach in a system that combines a solid metal hydride with moderate pressure (lower than 10,000 psi) ,which they predict could achieve a driving range of more than 500 kms.
Designeer Materials: recent developments in nanoscale engineering have yielded a host of new high-surface-area materials, some with ~ more than 5,000 sq.mt. of surface area per gram of material. Carbon -based materials are mostly light weight and low cost. Over the centuries ,the basic promise -and challenge-of using hydrogen for transportatiQ1has remained fundamentally unchanged. Nevertheless finding a suitable container to store hydrogen in automobiles will soon permit people tp travel across the globe in the next decade without fouling or polluting the sky above us.
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