KEY POINTS:
Despite some recent assertions, the battery-electric car will not make a dent in our carbon emissions. Even in New Zealand, with our large share of hydro electricity, the marginal unit of electricity always comes from a fossil fuel power station.
Counting the losses of the power station into
the equation, an electric car, despite its own efficiency, does nothing to mitigate carbon emissions. It merely shifts the carbon output from the tailpipe to the smoke stack.
Generating the electricity from renewable sources, such as photovoltaic cells, is still forbiddingly expensive. Even if it was cheaper, it would be more sensible to feed the electricity directly into the grid, rather than into the battery of an electric car.
The electric car is no more than a tax avoidance scheme because its owner avoids paying the fuel tax.
Are hybrid cars, then, the answer? A conventional car with a combustion engine is wasting fuel in two major ways: when coasting or idling, and when turning kinetic (motion) energy into heat at the brake pads.
A hybrid, that is a combination of combustion engine and electric motor, minimises these losses.
While idling or coasting, the storage battery is being charged (or the car is running temporarily on electricity alone, which means there is no idling at all).
The car is braked by switching the electric motor to generation mode, thus saving the energy for a new acceleration process.
From that, it is immediately clear that a hybrid car is most effective in city traffic. On long highway stretches, a hybrid is pretty much a wasted effort.
Hybrids come in many variations, each having different characteristics.
On one side is the full (or in-line) hybrid. In its extreme form, the combustion engine is a very simple turbocharged diesel.
It is directly linked to a generator which doubles as a starter. The diesel runs at a set speed, therefore avoiding costly engine management systems such as variable valve and injection timing.
Four electric drive motors are integrated into the wheel rims. When braking, the drive motors switch to generation mode. The recovered brake energy is stored in a battery which also stores any surplus electricity generated by the diesel.
Once the battery is charged, the diesel engine stops until required to recharge the battery. Motor management, flywheel, clutch, gearbox, drive train, differential, stub axles - all gone.
This car is simplicity itself. Since the engine is such a compact unit it can be very well sound insulated and can be taken out in minutes for service or replacement.
The unit can be placed anywhere in the car, allowing a space saving layout. Such design is ideal for city traffic.
The mild hybrid is totally different. The main propulsion is still the combustion engine. The major difference to an ordinary car is the modified flywheel.
This is a combined generator and electric motor which generates electricity when braking the car, and then helps to accelerate the car after a stop. A relatively small battery stores the electricity short-term.
The combined generator and starter also allows incorporating a stop-start system, in which the engine automatically switches off at stops and is restarted in a fraction of a second by pushing the accelerator.
This combined flywheel/starter/generator is hardly experimental. It was used 60 years ago by the German car maker DKW (now Audi).
Between these two extremes we find the present hybrids. They probably combine the drawbacks of both extremes without delivering on their respective advantages.
Why? These cars are very complex, and expensive to build. If it takes the average motorist five years to recover the extra cost for a hybrid through fuel savings, one can guess that the extra energy used in the production process of the hybrid components takes a similar length of time to recover.
Fuel cell cars, the holy grail of automotive engineers, basically are electric cars. The electricity is generated by fusing hydrogen and oxygen.
Unfortunately, hydrogen is not readily available. It has to be separated out of water, which in itself uses energy, and lots of it. Until we find ways to produce cheap hydrogen, the so-called hydrogen economy is a pipe dream.
Bio-fuels are fine, provided they are produced from organic waste, not specially grown crops. The latter would replace food crops: one SUV tank of ethanol requires crops that would feed a person for a whole year.
Also, its production is so energy intensive that it uses up more fuel than it delivers.
Is there a silver bullet? Perhaps a friendly, genetically modified bacteria or algae can be made to supply hydrogen from organic waste; or a breakthrough in photo-voltaic panels will allow us to make solar electricity at reasonable cost.
In the meantime, there are many improvements possible to the car as it is.
Many of these measures have not been cost-efficient in the past. But now, with fuel prices remaining high, these incremental improvements will pay for themselves.
Here are a few examples of how fuel consumption and carbon emissions can be reduced:
* Using diesel engines. They are more efficient than petrol engines because they work with a higher combustion pressure.
* Using compressed natural gas as fuel.
* Lowering the weight of a car. Admittedly, aluminium components need more production energy than steel but this is recovered through fuel savings in the first three years. When aluminium is recycled, its energy uptake is less than recycled steel.
* A cold engine uses about twice as much fuel, due to incomplete combustion. There is a case for pre-heating the cooling water before driving off, or for in-built heat retention which keeps most of the cooling water warm for 24 hours.
Volkswagen designed such a device five years ago but at the time it was not cost-efficient.
* BMW has just announced it is working on a system to recover waste heat from the exhaust and cooling water to drive an auxiliary steam engine.
* Using low rolling-resistance tyres and bearings.
* Extremely streamlined car bodies: side mirrors replaced by cameras, wheel wells covered, door handles flush, no large gaps between body panels, smooth underbody.
No spoilers - front or rear - because at legal speeds they simply create drag without improving the road-holding one iota. (They may make the car look fast but they also make the driver look intellectually challenged.)
* Most important of all, cars should shed excessive horsepower and engine size. There is no need to have cars which can go at two-and-a-half times the legal limit; and there is no need to accelerate 2 tonnes of steel from zero to a 100 clicks in six seconds. Except to serve our egos, yours truly's included.
* Peter Kammler is a member of Power for Our Future, and the Sustainable Energy Forum. His background is in engineering, including at Mercedes Benz in Stuttgart.
