Electric cars have been around since the very beginning of the automobile. Much like the uncertainty today, in the early days of the car there was a lot of debate between the ideal method of motivation; whether it would be gasoline, diesel, steam or electricity. Mainstream electric cars faded off pretty quickly due to the weaknesses inherent in the contemporary battery technology, but they continued in the small scale since. In the early 90s General Motors released the EV-1 which was the first real attempt to produce a modern mainstream electric car. It was popular among its owners, and could have been successful, but low gas prices, the still relatively archaic battery technology, and the high cost of development spelled its end. Check out Who Killed the Electric Car for a full explanation.
There is now a new boom of electric cars. With new companies like Tesla starting up, and established companies like Nissan and BMW stepping into the game, there is becoming a public awareness of these cars. With cars like Nissan's Leaf, they are getting to be affordable and are now plausible replacements for at least one of the cars in your garage. I could even see myself owning one of these in the next few years (to offset one of my poor mileage sports cars).
There are problems with the current concepts of electric cars though. They require large amounts of batteries. The Tesla's batteries weigh 992 lbs., which is over 1/3 of the car's total weight. Weight is the principle hindrance to economy, and because they built it off of the featherweight Lotus Elise chassis, they have minimized all other weight. Once this system is implemented in a larger chassis, they will necessarily have to add more batteries (and weight) to get comparable distance performance. The batteries also have the problem of being taxing on the environment on both ends of the life cycle. Batteries, especially the lithium ion type found in most modern electric cars, use a lot of rare earth metals, and are not just driving up the prices of them, they are actually causing global shortages of them. Disposal of batteries is something that will likely cause issues for generations, recycling can take care of some of the waste, but certainly not all.
Range is a large problem of electric vehicles (or maybe a small problem). Most electric vehicles struggle to cover 100 miles between chargings, well shy of the 250-400 mile ranges of a comparably sized internal combustion powered car. And while it takes just a minute or two to refill an empty gas tank, it can take hours to charge an electric car with US standard 110V power. 220V or more power stations lessen this time, but it is still a substantially longer time than a quick pit stop at the gas station.
This is where the Range Extender concept comes in. Also known as a series hybrid (told you I would come back to this), this type of car powers its wheels with electric power at all times, but has an ICE powered generator to recharge on the go. This is in my estimation the single best short term solution. The much touted Chevrolet Volt works on this concept, as do several other concept cars not currently slated for production. Like an electric car, you plug the cars in at night, and let the batteries recharge. In the morning you drive off silently operating on an all electric mode, if you run long enough to push toward the end of the range, it will automatically start up the engine and recharge while you drive.
There are many positives to this set up. ICEs are most efficient running at a constant speed, not the up and down they are usually subjected to in a car, so they can run the generator at an RPM for which it is designed to run optimally. They can use big laggy turbochargers, direct injection, and all sort of other technology that may be less than ideal for a car engine, but can optimize a small engine to be as fuel efficient as possible. It also means you can use all sorts of different engines without major retooling, assuming they are built with modular designs. The Volt uses a gasoline engine, whereas its Opel sibling for Europe is diesel powered; other concepts use a single rotor Wankel engine. It is possible to use all sorts of engines and fuels (like biofuel, which isn't inherently bad, just some of it), and a small gas turbine engine isn't unreasonable in this application. They also require fewer batteries which can only be a good thing.
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