Environmental Engineering Reference
In-Depth Information
energy content, emissions are reduced. It is possible to
make engines that can run on either natural gas or liquid
fuels. To my knowledge, none are on the road.
Some companies are experimenting with CNG systems
for big trucks. In cars, the CNG tank takes up much of the
room in the car trunk. This is not a problem in a big
truck. You also see many buses that run on CNG. They
get refueled when they return to their home in the
evening so
finding a refueling station is not an issue.
Hydrogen is another potential source of fuel that has
received much publicity. There is a huge amount of it, but
hydrogen is so reactive that all of it is tied up in various
chemical compounds including water and natural gas.
There are no hydrogen wells. The
first problem for
hydrogen is the energy it takes to separate the hydrogen
from the other elements to which it is bound. The second
problem is how to use it. It is possible to burn hydrogen in
an ICE but that is no more ef
cient than burning gas-
oline; all the losses shown in
Figure
will happen and
in addition more energy is lost to producing the hydro-
gen. The thrust of the development program is to use
what is called a fuel cell to make electricity from hydrogen
to run an electric drive system. The two alternatives
receiving the most attention are generation of hydrogen
on board the vehicle from natural gas (or perhaps methyl
alcohol), or generating the hydrogen outside the vehicle
and storing the hydrogen itself on board. Most of the
effort to date has been on the systems with external
hydrogen generation.
The vision of the advocates of hydrogen fuel is that
wind- or solar-generated electricity is used to produce the
hydrogen; the hydrogen is moved to the fueling station
.
