Monday, March 02, 2009

All-electric or plug-in hybrid electric vehicles?

Illustration - Powertrain of a plug-in hybrid electric vehicle with 4 wheel-motors, as conceived by Pierre Couture at the Hydro-Quebec Research Institute and announced in 1994. (drawing: Pierre Langlois)

We are currently at a turning point in the history of the automobile, where we will have to invest considerable sums to reduce our dependence on oil. The rapid depletion of oil, the geopolitical conditions that are attached, the problems of air pollution and global warming are strong incentives to drive more and more with electricity. In this regard, it is important to identify the best technologies to implement by 2030 to avoid investments that lead nowhere, like hydrogen cars. Should we invest in all-electric vehicles or plug-in hybrid electric vehicles (PHEV)?

The company Project Better Place is campaigning for all-electric cars, by offering to install expensive infrastructure of recharging points and battery exchange stations to «fill up» with electricity in less than 5 minutes. With PHEV, no need to install new infrastructure since you can go to fuel stations across the existing infrastucture, while passing through 80% of our mileage in electric mode, and recharging a smaller battery each day, at home or at work. In addition, PHEV enjoy full range (electric and fuel) of more than 700 km, in contrast to 150 km to 200 km for all-electric cars.

Some defenders of Project Better Place concept say that it is cheaper to install recharging and exchange of batteries infrastructure than installing two engines (one electric and thermal) in PHEV, on a large scale. But to reach such a conclusion, they must certainly exclude the cost of batteries. Because the cost of performing and long life lithium batteries is about $ 20,000 to give a range of 100 km (60 miles) to a midsize car. Assuming that the price decreases by half with a mass production, we will still have to pay for the battery about $ 20,000 for a fully electric car with a range of 200 km (120 miles).

But you must know that 2 in 3 drivers drive less than 50 km (30 miles) per day United-States, and less daily mileage in Europe, on average. However, a battery capable of a range of 50 km (30 miles) would cost $ 5000 to equip a PHEV instead of $ 20,000 for a fully electric car that can travel 200 km (120 miles). For the PHEV, just add about $ 3,000 to include a gas motor-generator to recharge the battery while driving during long journeys. Therefore, the high cost of batteries means that PHEV cost $ 12,000 less than fully electric cars of same size and performances.

Also, why one would install a battery offering 200 km (120 miles) of range when a battery allowing 50 km (30 miles) of range would be sufficient for daily needs? This is a real waste of resources. Let us not forget that the global lithium reserves are estimated at 11 million tonnes, according to the U.S. Geological Survey, and that one expects that over 1 billion vehicles will be on the roads in 2030.

Now it must be said, a range of 200 km (120 miles) for a fully electric car is not sufficient to meet all the needs of a driver, especially that this 200 km (120 miles) falls rapidly to less than 150 km when using the heating or air conditioning. Increasing the battery range is too expensive and makes the car too heavy, since it takes about 200 kg per 100 km of range for high performance lithium-ion batteries. Thus, for a range of 400 km one would require a battery of 800 kg, which increases the energy consumption of the car and decreases its performances inevitably.

Finally, fully electric cars are facing the another problem of an increased vulnerability to a major power outage. Quebecers who have experienced the ice storm of 1998 and were without power for 3 weeks in winter know something about it. All electric cars could not move in such a situation, whereas PHEV could have powered houses from their on board gas generator. The energy redundancy offered with liquid fuels is thus very important. How to escape from a big hurricane with an all-electric car when power is down?

It is possible that in 25 or 30 years all-electric cars take over. But before this could happen, it would be necessary to have batteries that are capable of storing 5 times more electricity for the same weight as the Li-ion batteries today, that their price be ten times less, and that our electricity networks are decentralized to reduce their vulnerability. Until then, all-electric cars could may be reach 20% of the market, as a second family car for comuting. But for that we do not need an infrastructure to exchange batteries or removable batteries. It is sufficient to add gradually recharge points at strategic locations, accessible to all electric cars, not only those of Project Better Place. In fact, most people will simply recharge their urban electric car home at night, when rates are lower.

Our analysis shows that the vast majority of cars of the next quarter century should be PHEV able to travel up to 100 km in electric mode. By 2010, PHEV could consume 10 times less fuel than conventional cars, since 80% of their mileage could be done in electric mode and that these cars use about half the fuel used by conventional cars, when operating mode fuel. In 15 years from now, advanced PHEV will be able to consume 20 times less fuel than petrol cars of today. It will then be possible to drive without oil and use only second-generation biofuels (made from waste and non-food plants).

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