Green cars of the future

THE HYDROGEN FUEL-CELL CARHow does it work?Remember chemistry lessons spent studying electrolysis? Well, fuel-cell cars work in more or less the oppos

THE HYDROGEN FUEL-CELL CAR

How does it work?

Remember chemistry lessons spent studying electrolysis? Well, fuel-cell cars work in more or less the opposite way. You combine hydrogen with oxygen in a fuel-cell stack to produce electricity – leaving nothing more toxic than distilled water evaporating from your exhaust pipe. It sounds good, but fuel cells are not much closer to being a workable power source for cars now than they were a decade ago.

How is it developing?

Not very rapidly. Fuel cells are still very expensive to make because they contain so many semi-precious metals, such as platinum. The Honda FCX Clarity is a step in the right direction, but it needs to stay within range of special hydrogen filling stations – one reason you can’t get it in the UK yet. No one has yet figured out how to make, distribute and store hydrogen cheaply enough to power the cars of the future, because it’s ten times less energy-dense than petrol, even when liquified or compressed as a gas.

How green is it?

In theory, very green, but much less so when you factor in the energy used to process and transport the hydrogen.

Will it take over?

Maybe during our grandchildren’s lifetimes, but ?not our own.

Chance of success 40 percent

How does it work?

The term “biofuel” covers a number of fuel types derived from various plants. Typically this is either ethanol created by fermenting crops such as sugar beet and corn, or more directly from oily plants to create biodiesel. Petrol engines can be adapted fairly easily to run on “E85” bioethanol (a mix of 15 per cent petrol and 85 per cent ethanol), while diesel cars can be persuaded to drink biodiesel without too much of a fight. In theory, by running your car on biofuel, you’re offsetting the CO2 emissions it creates with the carbon dioxide absorbed from the atmosphere during the growing cycle of the crop you’re making your biofuel from.

How is it developing?

Producers are working on making biofuels from waste materials, rather than from anything grown at the expense of rainforest or food crops. That way, fuel can be made from algae, orange peel or sawdust. So it seems Doc Brown’s junk-guzzling Delorean in Back to the Future II wasn’t that far fetched.

How green is it?

There are major concerns about the environmental impact on  areas used to grow biofuel crops, but if we get to the point where enough fuel can be sourced from recycled waste, it could ?be the greenest option of all.

Will it take over?

If there’s as much rubbish in the world as we’re lead to believe, it has a fighting chance.

Chance of success 60 percent

 

How does it work?

A full hybrid is a car with both an internal combustion engine and an electric motor. In a parallel hybrid, both power sources are connected to the wheels; in a series hybrid, the petrol engine drives the wheels and the electric motor just helps out, adding power when it’s required, and also capturing the energy that regular cars waste during braking. There are mild hybrids too, which offer the brake energy recovery part of the equation. These also have a great big elastic band attached to the engine to automatically start it and stop it in traffic, but they’re not quite the full portion.

How is it developing?

Thanks to advances in laptop battery technology, lithium-ion cells are now becoming cheap enough to use in hybrid cars, boosting efficiency and range. Also, car makers are figuring out how to reverse the relationship between the two engines in ?series hybrids to turn them ?into electric cars with small combustion engines that act ?as back-up power generators.

How green is it?

That mostly depends on what’s used to fuel the combustion engine. If it’s petrol, only mildly green, but diesel is a little bit greener. However, if it uses a second-gen biofuel such as E85 bioethanol, the resulting car can be very green indeed.

Will it take over?

We wouldn’t bet against the global favourite winning.

Chance of success 95 percent

How does it work?

Replace a car’s engine and gearbox with a smaller electric motor and a couple of hundred kilos of batteries, and you’ve cracked it. That’s the theory anyway. In the real world, batteries are heavy, expensive and tricky to keep cool, and the circuitry needed to keep them safe in a car is complicated and troublesome. But when they work, electric cars can be brilliant. They’re emissions-free, quiet, generally have no gears ?to worry about and can be especially fun to drive because electric motors produce maximum power the second ?you floor the accelerator.

How is it developing?

Recent improvements in battery technology mean that electric cars no longer have to be the size of a shoe and run out of puff after 25 miles. Various companies are developing new electric motors small enough to sit inside the hubs of car wheels, promising further performance enhancements. Meanwhile, greater availability of three-phase charging points will allow you to juice your car in an hour, rather than overnight from a normal 240-volt three-pin plug.

How green is it?

Assuming your power comes from a renewable source, they’re as green as cars get.

Will it take over?

Recharge times and the current lack of charging points are issues, but if batteries can be made cheaply enough, it’ll work.

Chance of success 80 percent

 

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