Mechanism in need of a more efficient form

IT would be a brave engineer, or car company chief, who would predict the downfall of the internal combustion engine. That has been done many times during the 120-year history of the car, always with embarrassing results for the pundit. But no great clairvoyance is required to see the age of cruising the boulevards in two tonnes of symbolically decorated metal, plastic and rubber is drawing to a close for most of us. The distinctive burble of the V8 engine is starting to sound like an American elegy for the era of cheap gasoline.
Smaller, arguably more sensible versions of the internal combustion engine will be more resilient. A quiet revolution over the past 30 years has changed the typical car engine from a self-regulating mechanical device into a computer-controlled system. The resulting improvements in fuel consumption have been masked by the trend for cars to get heavier due to luxury and safety features, but if some future cars are lighter, making more use of aluminium, plastic and carbon composites, buyers will cash in on the computer dividend.
The internal combustion engine does not just mean the petrol engine. After a century of duty below stairs, the diesel engine made its debut in polite European automotive society in the 1990s as the computer revolution liberated its inherent efficiency. This year has seen diesel taking a small but rapidly growing share of the Australian car market. And there's more to come: it's an open secret that Holden is working on a diesel-powered version of the Commodore.
Nor do internal combustion engines have to run on fossil fuels: such fuels just happen to have been the cheapest and most plentiful option for the past century. With a little tweaking, petrol engines can run on ethanol, methanol, natural gas or liquid petroleum gas, and diesels can run on biodiesel, which can be made from oilseed crops.
For Australia, LPG is an appealing option despite it being the favourite fuel of the beaten-up taxis that drone around our cities. Unglamorous associations aside, LPG is easily stored, unlike natural gas or hydrogen.
LPG burns with fewer pollutants than petrol or diesel and can easily be used by existing engines.
Electric cars are the wild card. Their disadvantages of speed and range remain similar to what they were a century ago. But with most urban car journeys stretching no more than 10km, these drawbacks are more psychological than physical. The electric car has never been able to match the emotional promise of the combustion engine: power and freedom. But in an urbanised world where a car becomes just another durable good, its time may come.
Vehicles with internal combustion engines will increasingly also have electric motors for assistance in acceleration. The great advantage of these hybrid designs is that they can recover the energy normally lost in braking. Energy that makes the brakes hot in a normal car is sent, by virtue of an electric generator used as a brake, into batteries that drive the electric motor when the car accelerates again.
Hybrid propulsion is already with us in the petrol-electric Toyota Prius. But it, too, is set to become a broad church with hybrids using petrol, diesel and gas engines and providing auxiliary propulsion with electric motors, high-pressure hydraulics or even steam heated by the fuel-burning engine's exhaust. Hybrid design is not a fuel system in itself but a way of making fuel go further.
Beyond the hybrid comes the fuel cell. Leaving out the complex chemistry of how they do it, fuel cells convert hydrogen and oxygen into water and electricity. The electricity drives electric motors and the water vapour goes out the exhaust pipe. Neat as this sounds, it is quite wrong to think of hydrogen as a natural fuel for the fuel cell. Hydrogen has to be made, usually in an energy-intensive process such as electrolysis using water, so it's more a means of carrying energy around than a naturally occurring fuel. However, if oil runs out we'll have little choice but to convert other energy sources into hydrogen.
German car maker BMW has already declared its intention to build internal combustion engines that run on hydrogen. It's a family tradition: the four-stroke engine found in all modern petrol cars was invented by Nicolaus Otto, whose son August Otto founded BMW. In 20 years hydrogen-fuelled BMWs may even be running homogeneous charge compression ignition engines, the ultimate version of internal combustion.
A HCCI engine is a hybrid between a petrol and diesel engine, drawing a fuel-air mix into the cylinder like a petrol engine and igniting it with pressure like a diesel engine. The results are diesel efficiency and petrol pollution levels.
The drawback is the amount of computer power and precise fuel supply needed to keep these engines running. At this stage they're benchtop curiosities, as Otto's engine was in 1867, but HCCI could give his world-changing invention a second century of life.