(With appreciation to Charles Hugh
Smith for posting from the U.S. on my behalf; I'm in China and can't post due to
the PRC's blocking of Google. Nor can I tweet from here; Twitter is blocked
too. This is the downside to a nation where the trains run on time).
Last time, we looked at the coming
revolution in automotive technology--the switch from internal-combustion power
to hybrid power and, eventually, to straight electric vehicles. This time, we’ll
take a closer look at both the pros and cons of electrics, which hold such huge
promise for a cleaner, quieter, and more eco-friendly environment.
In order to appreciate how
profound this change will be, though, a bit of nuts-and-bolts background is in
order. One basic way of seeing how well a machine works is by looking at its
thermal efficiency, which is simply the percentage of input energy that’s turned
into useful work. The early steam locomotives of the 1840s--the first motive
power that didn’t depend on wind, water, or muscle--were about 3 percent
efficient. Over the next hundred years, technical improvements managed to nudge
that figure up to about 7 percent--a big relative improvement, but none too good
in absolute terms. Since a large steam locomotive of the 1940s typically burned
about 65,000 pounds of coal per hour, about 60,000 pounds of that coal was
effectively wasted.
In the postwar era,
diesel-electric locomotives with thermal efficiencies of around 21 percent
arrived on the scene, wiping the wasteful steam engine off the map for good. By
comparison, most modern internal-combustion cars are around 26 percent
efficient, although their friction-laden mechanical drive lines drag this
already modest figure down to about 18-20 percent. In other words, sixteen
gallons of your twenty-gallon gas tank goes toward generating heat and nothing
else.
The electric car constitutes a
quantum leap over this dismal performance. Electric motors are typically around
78 to 90 percent efficient to begin with, and the absence of a mechanical drive
line means most of this power actually gets to the wheels instead of being
burned up in friction. What’s more, electric cars can use regenerative braking
systems that use braking energy to charge their batteries instead of burning it
up in heat as today’s cars do. The electric drive system is also far simpler
and, eventually at least, will be much cheaper to build than today’s enormously
complex internal-combustion cars.
But the news isn’t all good. While
electric vehicles themselves don’t produce emissions, as things currently stand,
the electricity they use is far from emissions-free. In the U.S., about
two-thirds of our electricity is generated from burning fossil fuels, which
leaves a very nasty carbon footprint indeed. The thermal efficiency of a
typical coal-burning generating plant is itself less than 50 percent, and what’s
more, transmitting this electricity to the user induces another loss of
efficiency, typically around 7 percent. Under these circumstances, plugging in a
purportedly “zero-emissions” electric car simply transfers environmental
degradation from the vehicle to the generating plant--in effect, these new
electric cars are actually burning coal.
The solution is to develop an
infrastructure that can recharge vehicles using clean sources of electricity
that are locally generated, whether by wind, water, or photovoltaic panels. This
is the only way an electric car can truly meet its potential as a “zero emission
vehicle”. The challenges are great, but, if history is any indication, our
ingenuity is greater.
No comments:
Post a Comment