21- www. energy- future. com 2.1- Transportation frastructure - ships, lorries, pipelines and filling stations - on which it relies. Although being accustomed to one way of doing things is, in itself, a weak argument against explor-ing alternatives, it would certainly be difficult and costly to move to a completely new sys-tem - and it would take a long time. The problems with petroleum But petroleum has its drawbacks too: stricter laws governing the output of CO2 and other greenhouse gases are today's cars' biggest problem. As the cost of emit-ting carbon rises, alternatives to the internal combustion engine will become increasingly attractive economically - unless, perhaps, energy companies discover a cheap way of producing very large volumes of renew-able biofuels that can be used harmlessly in the engines in use today. Companies be-hind the nascent algae revolution think that might happen one day, but it's an uncertain prospect ( see p78). Then there's the repair system to think about, says Julius Pretterebner, a car- indus-try analyst at IHS Cera, a consultancy. With all of its many and intricate moving parts, the internal combustion engine needs a large maintenance network. That's one area in which the electric car wins hands down, he adds: apart from the driveline, it doesn't have much in the way of moving parts. That means considerably less wear and tear, less maintenance and no need for a complex support industry. Fuel standards in liquid fuels - for oil products and biofuels - create problems for car manufacturers too. Because they vary from region to region and, often, from country to country, it's impossible to produce a one- size- fits- all engine. That puts costs up. Adapting an electric vehicle to a differ-ent market is simple: all you need is a plug adaptor and, possibly, a transformer. There's also the question of efficiency. The internal combustion engine is typically For decades, it will be difficult for anything - batteries, hydrogen fuel cells or biofuels - to replace gasoline and diesel at scale in the transport sector

22- www. world- petroleum. org 2.1- Transportation only about 20- 30% efficient. Lower perhaps: according to fueleconomy. gov, only about 15% of the energy from the fuel in the tank is used to move the car or run useful accesso-ries, such as air conditioning. The rest of the energy is lost to engine and driveline ineffi-ciencies, and idling. And drivers rarely get the best out of their cars: an internal com-bustion engine optimised to 200 horsepower won't work at its best crawling through heavy traffic, so, in the city, efficiency slumps - it's the inverse of trying to heat a room with a hairdryer. Emissions performance also de-teriorates at lower work rates. But poor efficiency ratings at least mean there's room for improvement. What can be done to make existing cars more efficient? Various technology devel-opments will help cut down on fuel use. Cylinder deactivation, for example, shuts down some cylinders when less power is required. Modern engines can also be de-signed to alter valve timing - varying the quantities of air and fuel entering the cylin-ders and enabling fuel savings when power needs are low. Hybrid cars - bi- fuelled vehicles that can switch at different speeds between a gasoline- burning internal- combustion en-gine and an electric motor powered by a re-chargeable battery - can achieve signifi-cant efficiency improvements over cars with standard engines. The electric motor - re-charged with kinetic energy that is normally lost to braking, with a system called regener-ative braking - means the gasoline engine isn't needed when the car has stopped or when it's travelling at low speeds. The gaso-line engine, meanwhile, is there for higher speeds and to overcome the limited driving range of an all- electric vehicle. Doing the obvious stuff There are plenty of straightforward ef-ficiency measures too, such as reducing the size and weight of vehicles. Today's VW Golf, for example, is almost twice as heavy as the first Golfs, built in the 1970s. That's partly because of the addition, over the years, of safety features, such as the protective metal bars in the doors of mod-ern cars. It's also partly down to a perceived need for more room: the smallest cars in BMW's range today - the 1 Series - are similar in size to the BMW 2002; but in the 1970s, the 2002 was considered a roomy, desirable family vehicle. The weight increase is also the result of the proliferation of electronic gadgets and modern conveniences. In some areas that trend will continue: there won't be any com-promise on safety, for instance. Indeed, car-makers are continuing to add safety fea-tures; electronic stability control, a compu-terised technology that improves a vehi-cle's handling by detecting and preventing skids, is among the latest innovations. But what about the non- vital stuff? Air condition-ing systems, for example, are heavy: could people do without them? Have you seen how low my carbon emissions are?