Hybrid, Hydrogen or Electric?

A decade ago, buying a hybrid was a lonely business. There were only two to choose from – the original Honda Insight and the gawkily styled 1997 Mark I Prius – and both attracted small numbers of buyers.

Honda was first to market, ith its eccentric two-seater Insight, but it was Toyota and Hollywood A-listers such as Leonardo DiCaprio and Julia Roberts who got hybrids established with the second-generation Prius.

But while a hybrid might emit significantly less CO2 than a car of comparable size, it’s a long way from emitting no carbon dioxide at all, which is why they are merely stepping stones towards the truly zero-emission car.

The propulsion systems that completely eliminate tailpipe emissions include hydrogen-powered fuel cells and the battery-powered electric motor, but both face significant hurdles before they can compete with conventional cars.

For fuel-cell models, the stumbling block is the ready availability of hydrogen. It might be the most common element in the universe, but it typically comes attached to oxygen molecules in the form of water, and the two require energy to separate them. Hydrogen is also an evaporation-prone gas – it’s difficult to transport and needs an expensive on-board storage system.

Several car makers have fuel-cell programmes, notably Honda and General Motors, and both have prototypes in daily use, but their widespread adoption is a good decade away.

More promising is the electric car. Like a fuel-cell vehicle it produces no tailpipe emissions and little noise, and the distribution network for its energy source largely exists – taking electricity the final few metres to a charging post is nothing compared to establishing a hydrogen infrastructure.

Instead, electric cars are limited, literally, by battery technology that today allows a modest city car a range of no more than 80 to 100 miles compared to the 300 miles-plus of a conventional car.

In fact, 80 to 100 miles is more than enough for most daily commutes, but a recharge time of several hours makes long journeys impractical. Which is why General Motors’ “range-extending” Vauxhall Ampera (aka the Chevrolet Volt) offers a promising compromise when it goes on sale in 2012.

For the first 40 miles it runs on electricity alone – more than enough for most commutes – but for longer journeys an on-board petrol engine recharges the battery to provide a range of more than 300 miles at 40g/km of CO2, or under half what the Prius produces.

Even if the electricity used to recharge it comes from coal-fired power stations, the Ampera is significantly cleaner than a conventional car.

The ease of recharging it, and pure electric cars, is likely to be improved by policies intended to encourage electric car ownership. The present Government talks of incentives of up to £5,000, while London mayor Boris Johnson aims to make the capital a lead city in the adoption of the electric car.

However, the shortcomings of fuel-cell and electric cars will ensure that the internal combustion engine, which in diesel form gives the hybrid a strong run for its money, will be around for many decades yet in ever more economical form.