In an effort to break the West's dependency on oil, particularly that imported from the Middle East, electric vehicles might appear to offer a significant advantage. However, electricity (like hydrogen) is an energy carrier not a fuel, since it must be first manufactured using a primary fuel such as gas, oil, coal or uranium. There are various renewable resources - in the U.S. hydro power accounts for about 10%, far more than in the U.K. - but these are mostly untried technologies on the large scale, but which will inevitably become more important as oil and gas supplies begin to wane. The main problem with electricity is that it must be stored, most effectively using some form of battery technology, rather than mechanical devices e.g. flywheels. The traditional and conventional means is the "car battery", or some adaptation of it, based on the "lead accumulator" principle. This involves a reversible electrochemical reaction, which can produce electricity, but may be reversed by the absorption of electrons, and so like any other rechargeable battery it may be charged by plugging into the mains or using an on-board generator. Other (lighter weight) batteries based on lithium (lithium ion) are considered to be more suitable for electric vehicles on a number of counts. My immediate thought when an electric vehicle is mentioned is the "milk float" or "golf cart", but such locomotive devices have reached profound levels of sophistication, and to all intents and purposes easily match the speed and other qualities we expect from an internal combustion engine powered car. The half-way-house is the hybrid vehicle which uses a combination of an internal combustion engine run on gasoline and a parallel source of electric power, e.g the Prius. In his comment to my recent posting "Bioethanol - The Math" mcrab has included a link describing the virtues of the Plug in Hybrid Electric Vehicle (PHEV), which as he says can in principle cut back the transportation fuel demand by 80%, requiring a relatively modest increase in electricity production by 13%. I endorse this wholeheartedly, but note that the fundamental feature of this and all other electric vehicles is the central electron storage system. Lighter weight lead - sulphuric acid batteries than the conventional accumulator type are being developed and there is plenty of lead left in the world. For example, if we take the current number of cars at 500 million (I think the total number of road vehicles in the world is around 700 million - that's cars, lorries, buses, everything, but let's just stick to cars), we would need about 150 kg (per car) x 500 x 10*6 = .15 tonnes x 500 x 10*6 = 75 million tonnes of lead. I believe there is certainly 1.5 billion tonnes of lead in known deposits, so there is plenty to go round.
Lithium ion batteries (the current favourite) are costed in energy terms at 2 kg of lithium per kwh of battery (specific energy). The PHEV is rated at 9 kwh and so each car would need 18 kg of lithium. Hence, 500 million PHEV's would require:
18 kg x 500 x 10*6 = 9 x 10*9 kg = 9 million tonnes of lithium.
The entire world reserve of lithium ( accounted in the form of lithium oxide, Li2O) is 10.74 million tonnes, which contains (worked at an abundance of 92.5% lithium-7 and the rest lithium-6):
2 x [(7 x .925) + (6 x .075)] x 10.74 x 10*6/2 x [(7 x .925) + (6 x .075)] + 16 = 4.98 x 10*6 tonnes; call it 5 million tonnes of lithium.
Obviously there is not enough!
We could argue naively that there is sufficient to propel 278 million cars (i.e. around half the world's fleet) adapted into PHEV's, but this would conflict with the interests of nuclear fusion (if they ever get it off the ground) which could only run for about 300 years, and so it would be a question of lithium to make electricity or to store it inside cars to get any actual mileage from it! Since, as I have argued before, nuclear fusion will not come to our aid before oil and gas run out, we can forget about this point, but I make it to stress that the same (limited) resources are often impacted upon competitively by different kinds of technology and it is as well to be aware of the fact.
If we wanted fully electrically powered cars, with a power demand of 36 kwh (over the 9 kwh reckoned for a PHEV), then we would need to reduce that figure by a factor of four (36/9) leaving us with just under 70 million cars in the world. These figures are an absolute maximum, as of course, there are many other uses for lithium batteries, eg. heart pacemakers, pocket calculators, computers and cameras etc. etc.
Undoubtedly, advances in battery technology will improve the situation, and there is talk of "aluminium" batteries, but these are well at the research stage and may come to nothing in any practical sense. An alternative kind of battery is the nickel metal hydride (NiMH) type, which needs around 7 kg of nickel per kwh = 7 x 9 = 63 kg of nickel per 9 kwh PHEV. So, if we work the math again over 500 million cars, we get:
500 x 10*6 x 63 = 3.15 x 10*10 kg = 31.5 million tonnes of nickel. Since the world reserves of nickel are reckoned to be 62 million tonnes, that would be in principle O.K.
However, a bottleneck to implementing a new technology is the production rate of raw materials, and I note that 5 million tonnes of nickel is produced each year. If half that quantity were turned over to battery production for PHEV's, you could produce:
2.5 x 10*6 x 1000 kg/63 kg = 40 million vehicles per year, and thus the full fleet of 500 million PHEV adapted cars could be got up and running in 12.5 years! They are wonderful things, numbers and statistics, and behind them lie the practicalities of the matter at hand, which appear to point to a greatly reduced car fleet within the foreseeable future, whatever means we try to implement to keep them on the road... in some form or another, fuel powered, hybrid or fully electric, or some combination of different kinds of vehicle. If we were to reduce the number of cars by 90% (i.e to a world fleet of 50 million), as I have suggested previously, via living in localised communities "pods", we would have sufficient bioethanol and other renewable fuels, electrification and other means to survive the choppy slide down from peak oil production. It is the social paradigm that matters most, which must accommodate whatever technology becomes or remains accessible; our thinking must adapt because maintaining the status quo of energy use is impossible.