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Batteries v. gas - so far, it's no contest

Della Rollins/della rollins The Globe and Mail

Richard Gilbert is a Toronto-based consultant who focuses on energy and transportation. His latest book is Transport Revolutions: Moving People and Freight without Oil , written with Anthony Perl.



My last post suggested that two types of transportation fuel could replace oil products. One kind - including natural gas and biofuels - could be used in versions of the internal combustion engines (ICEs) that today provide propulsion for almost all road vehicles. The other alternative fuel - electricity - would require a switch to electric motors (EMs) for propulsion. I concluded that electricity is the best alternative, especially where there is a surplus of electricity generation or it could be readily expanded.

The main problem with EMs is not the EMs themselves, which are superior to ICEs in almost every respect. EMs use energy much more efficiently, produce no pollution at the vehicle, are smaller and lighter for a given power output, and provide maximum torque at zero or low speeds, when it is most required. The main problem with EMs is that electricity cannot be stored inexpensively and in acceptable quantities on-board vehicles.

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A tank of gasoline contains more than 60 times as much usable energy as the equivalent weight of the best available electric vehicle battery. EMs can be five times as efficient as ICEs, but that reduces the weight of batteries required to achieve the same range to no less than 12 times the weight of a full gasoline tank, other things being equal. Batteries' performance could improve by a factor of three, which may be dreaming, and there would still be more than a fourfold difference in effective energy storage, and thus range, between vehicles with ICEs and vehicles of similar size and performance with EMs.

Adding energy storage capacity to an electric vehicle is expensive as well as being weighty and space-consuming. The battery for an automobile with a range of 150 kilometres costs about $20,000, likely more than half the cost of the vehicle. Electricity is usually much cheaper than gasoline per energy unit, but not enough to offset amortized battery costs.

Getting the electricity into the battery is another challenge. The minutes at the gas pump must be replaced by hours at the home or business charger, or tens of minutes at a high-powered charger that could be costly to use, wearing on the battery and challenging for the electricity supply system. (Battery exchange is another possible solution, but this may not fit well with car ownership as now practised.)

Unless there are dramatic improvements in the performance of batteries and reductions in their cost, road vehicles relying on batteries are unlikely to provide the range, flexibility of use, and convenience of today's automobiles and trucks. However, for many purposes, particularly short, start-and-stop journeys within urban and suburban areas, they may be entirely suitable for moving people or goods. The range of city run-abouts can be extended by making them smaller and lighter than vehicles produced today. Such electric vehicles will become more popular if oil prices rise at a higher rate than the prices of batteries and electricity.

One solution to limited range is to equip the electric vehicle with an ICE that, via a generator, recharges the battery or powers the EM, or even drives the wheels directly. Vehicles with both EMs and ICEs are known as hybrid vehicles. They will be discussed in my next post.

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