Electric cars: the emissions dilemma

Part 2: The next auto revolution

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 100 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.