Air? Steam? Are these really being looked as future fuels for cars? Indeed they are, along with a range of other innovative fuels. Let's take a look at the contenders.
The key factor here is that battery life needs to improve because at the moment journeys are limited to around 100 miles. You may need to recharge the battery for several hours before you can set off again. These batteries are also expensive. Despite this, more and more electric cars are coming on to the market, and the technology is improving constantly.
Biodiesel is made from animal fats and vegetable oils, which has dismayed vegans. However, bioethanol, which can replace petrol, is made from corn and sugarcane. The newest biofuels don't use food sources at all, so this mitigates the concern that biofuels will drive up food prices by hogging farmland. Thanks to advances in fuel blending technology, second-generation biofuels can be made from sustainable sources.
Every time you apply your car brakes, you are wasting energy. Kinetic systems capture that energy and convert it into electricity that can be used to help drive the car, which therefore uses less conventional fuel. These systems are in their infancy, and they're expected to develop to allow drivers to capture more of the movement energy of a car, feeding it back to help power the vehicle.
This may sound impossibly quaint, but in fact, cars powered by steam existed long before the internal combustion engine became universal. How about an external combustion engine? The fuel goes through combustion separately from the engine and this produces fewer emissions. Still, at the concept stage, high-powered steam engines for cars may well be something we see in the future.
Cars powered by hydrogen produce no emissions except for water. BMW already have hydrogen cars on the market, and these will soon be on sale in the UK. However, hydrogen doesn't have to be used directly. It can be used to power up a fuel cell, which in turn produces electricity. This eliminates the onboard battery and is also as zero-emission technology.
As with kinetic energy, heat is a by-product of the driving process. In fact, it's estimated that two-thirds of petrol- or diesel-generated energy gets wasted as heat. Several car makers are looking at how to convert heat into usable electricity via thermoelectric panels that will be able to make use of exhaust heat. This could reduce fuel consumption by up to 5%.
Using compressed air to fuel a car may sound fanciful, but in fact, the air, stored in tanks under 4500 PSI of pressure, could drive the pistons in a combustion engine, thereby producing power.
The vehicles of the future may well combine one or more of these systems or use a system with additives in an innovative new type of fuel blending.