Why Don’t We Have All-Electric Cars?
Electric cars are attractive from a cost point of view. An electric motor is far cheaper to make than a gasoline engine. It has few moving parts and experiences very little wear. Electric motors are so long-lived they might be considered “immortal”. Advocates of electric vehicles point out that their operating cost is far lower than that of an internal combustion engine.
Batteries are the weak link in the electric vehicle. They are very large and heavy with respect to the amount of energy they can store compared to the energy in a hydrocarbon (gasoline or diesel) fuel. For example, a litre of gasoline contains ~70 times as much energy as a litre of lead-acid battery. A kilogram of gasoline contains ~300 times as much energy as a kilogram of lead-acid battery! Of course, there are better batteries.
A nickel metal hydride battery can store five times as much energy as a lead acid battery per litre and about twice as much per kilogram. That still leaves it far behind gasoline as a storage medium. The lightest battery is the lithium cell. Even this only contains six times the energy of a lead acid cell per litre and 5-6 times a lead acid cell per kilogram – still far behind the energy content of liquid fuel.
The bottom line is that, a modern gasoline-powered car easily travels 500km on a 50 litre tank. A similarly sized (lightweight) lithium battery might propel an electric car 100 kilometres, but it would also weigh 500kg! Heavy lead-acid batteries are used in cars is because they are reliable and far cheaper than other rechargeables! Also, the nickel and lithium based batteries we use in cell phones and lap-top computers are very costly.
Electric cars perform poorly in winter. Chemical batteries lose capacity when cold. Also, you need to heat your car in winter. An internal combustion engine wastes a lot of heat. This is used to defrost the windshield and your toes. An electric car must use its battery capacity – diminished by winter cold – to do this!
The real problem is that we have become accustomed to the huge energy storage capability of liquid hydrocarbon fuels. The best battery cannot even come close to this performance. In the end, we can have cars capable of a 100km trip on a single charge, but they will cost more than our gasoline vehicles. On the other hand, they are likely to be cheaper to operate, even if electricity is taxed (as it must be) to pay for our road infrastructure and other state supplied services to vehicle users (ambulance, police, snow plowing, etc).