Environmental Engineering Reference
In-Depth Information
sible to store liquid hydrogen or use metallic hydrates. Hydrogen-based fuel cells
are also under research and development. Even though proponents state that hydro-
gen is not more dangerous than gasoline if properly handled, hydrogen is a very
explosive gas and, therefore, safety problems have to be solved before it gains pub-
lic acceptance.
Concerning its compatibility with the existing infrastructure (production, stor-
age, and distribution), hydrogen would need very significant changes. At present,
the most likely hydrogen source is natural gas. Coal producers also have great in-
terest in the hydrogen economy, although, in the future, hydrogen could be pro-
duced from biomass, a renewable resource.
Electrical vehicles that use batteries are of great interest nowadays, especially for
urban environments. If the electricity moving them comes from a non-fossil source,
their use could result in a significant reduction in the emission of greenhouse gases.
The main hindrance to their wide implementation is the present state of chemic-
al batteries technology, resulting in high-cost, heavy vehicles with limited range.
Furthermore, whereas a gasoline automobile can be fueled in a few minutes, the
battery recharge for electric cars usually requires several hours. Large-scale intro-
duction of electric vehicles would require great changes in infrastructure, not only
in the power distribution system and in the automobiles but also in the power gen-
eration industry.
Hybrid vehicles run on a combination of batteries, which energize the propul-
sion system, and a small internal combustion engine fueled by gasoline, diesel oil,
or biofuels, which recharges the batteries. Regenerative breaking also helps in re-
charging the batteries. Lighter and long-lasting lithium-ion batteries for automo-
biles are being developed to replace traditional lead-acid batteries.
With hybrid vehicles, a fuel economy of up to 50% and a reduction in emissions
of about 70% can be achieved. The great advantage of this technology is that the
small gasoline-fueled engine works at a constant rotation and speed, saving fuel
and reducing pollution and noise levels. Hybrid vehicles can reach up to 40% effi-
ciency (30 km or 18.64 miles/liter).
Hybrid electric vehicles (HEVs) offer lower emissions and better fuel economy,
30-50% higher than in comparable conventional vehicles. Plug-in hybrid electric
vehicles (PHEVs) are the next step, potentially offering zero-emission transport-
ation, depending on the vehicle driving range. All-electric or battery electric
