Series Hybrids

Unlike today's "parallel hybrid" cars, where a normal gas engine and an electric motor are both mechanically connected to the wheels, the Volvo C-30 Recharge Concept "series hybrid" has four electric motors, one in each wheel well, and a diesel engine that isn't connected to the wheels - its only job is to act as a generator and recharge the batteries when they are low, or send electricity to the wheel motors if the batteries are empty. The car can travel 60 miles on batteries alone before the engine kicks in - and since you can recharge it by plugging it in at night, that means if you drive less than 60 miles a day, you'll never need to buy gas. And in a 93 mile drive starting with full batteries and a full tank, you would effectively get 124 miles per gallon. (Yes, that electricity from your wall probably doesn't come carbon-free, but even if 100% of it comes from coal-fired plants, your overall emissions will still be far less than a conventional gas engine.) Sadly, this car exists only in a test version, and may never reach production. However, GM is using the same basic design in their Volt hybrid car, with just slightly lower specs, which is entering production and should be available by 2010.