Tuesday, November 9, 2010

The Trouble with Electric Cars - Part 2

A few more thoughts on electric cars.

A number of motor manufacturers have invested heavily in electric vehicle (EV) technology, so you can bet your last cycle clip that they'll be leaning heavily on government ministers to incentivize consumers to embrace this new technology. While I'm prepared to believe that EVs are a good alternative to internal combustion engined (ICE) vehicles, I'm also suspicious that the books are being cooked to make EVs look better than they actually are. Anyone remember when nuclear power was touted as too cheap to meter? Or when bio-fuels were going to save the planet?

When charged with fossil-generated electricity, EVs are likely only marginally better in carbon-emission terms than ICE vehicles, but a lot depends on how you do the sums and what assumptions you make. Delivered electricity (that is to say, taking account of efficiency losses at the power station and in the grid) is only about 40% efficient, which a bit better than an ICE engine, although you need to factor in charging efficiency also. So if you burn a gallon of oil in a petrol car, you'll probably get a bit less energy out of it than if you burned a gallon of oil at a power station and charged an electric car with it. Electric motors are unquestionably more efficient than ICEs, but to get anywhere near the range of an ICE vehicle, you need a battery pack that makes the vehicle heavier than the equivalent ICE, so some of the efficiency savings are lost. (For example, the Nissan Leaf weighs 1524kg compared to the equivalent ICE-powered Nissan Versa at 1130-1270kg.)

If you charge an EV with renewable electricity, it will be much better than an ICE in carbon-emission terms, but we have some years to go before there is an excess of supply of renewable electricity. Until that point, charging EVs will suffer from the 'last megawatt problem', meaning that as soon as the load on the grid exceeds the renewable generating capacity, any load that is added (charging an electric car for example) will require more fossil generation.

That said, if the renewable capacity is wind-based, it will be useful to have a variable load (such as EV battery charging) that can be switched on (via a smart grid) to absorb excess capacity at times of excess renewable suppl (i.e. on a windy day). However, that does make a few assumptions. First, a significant problem is that EV batteries are very expensive, so for the moment EVs have a quite limited range. As a consequence, EV users may not wish to allow their batteries to run down significantly, so that the amount of battery capacity that is actually available 'on demand' to the grid may not be very significant. Second, the proposal to connect up the European grids may smooth out supply so that peaks are less pronounced.

In any case, building new renewable capacity is immensely expensive, so it makes a lot more sense to remove unnecessary energy use than to simply replace consumption of fossil with electric. The fact is that there are a lot of car journeys that are not necessary.

We could argue the relative merits of EV versus ICE till we're blue in the face, but we'd be focusing on the wrong problem. The right problem is that a typical car journey involves moving a vehicle that is 10-20 times the weight of the payload at high speed. To address this we need to:

  • Reduce the number of motor journeys;
  • Increase the proportion of journeys made by benign modes (cycling, walking and public transport).
For 'necessary' motor journeys,  we can promote eco-driving. Most drivers don't understand how to drive economically. Improving driving techniques can increase fuel economy by 10% or more. The Government should encourage employers to invest in eco-driving training for professional drivers.

Progress toward the above objectives can be made immediately without needing to change transport technology.

Longer term goals:
  • Reduce average vehicle weight. Given the fashion for SUVs this requires no technological change: even very minor alterations to existing vehicle designs such as replacing spare wheels with puncture repair kits, lightening seats and interior panels, and replacing non-structural body panels with composites could give worthwhile savings. Longer term, cars can be designed from the ground up with light weight as an objective.
  • Replace ICE vehicles with EVs.
Reducing weight will require significant cultural change. Consumers value the passive safety of a heavy car, and cars in each class have been getting bigger and heavier with each generation. It's difficult to see consumer aspirations changing without some kind of intervention, such as increasing taxes on heavier vehicles or forcing manufacturers to address the issue.

Replacing ICE vehicles with EVs is a long-term project. Charging Infrastructure needs to be built out and the supply needs to be renewable. Consumer resistance to EVs needs to be overcome. EV range is a blocking issue for many would-be buyers, and the cost of an EV even with tax-breaks and purchase price subsidy looks expensive. Then, significant numbers of people need to actually take the plunge and buy an EV.
It's quite possible that an oil price spike will unfreeze the public's attitudes to EVs, but if we still have an economy that is dependent on cheap energy when energy becomes expensive, the price signal will come too late.

To summarize, EVs alone will not solve our problem of a cheap-oil-dependent transport system, because they are a long-term proposition. They deliver too little benefit if electricity generation is still primarily fossil-fuelled (which will remain the case for some years), and there are massive problems in terms of infrastructure and consumer resistance to be overcome.
Reducing transport mileage and switching to more benign modes is easier and cheaper, and gives immediate CO2 savings, and improving the efficiency of ICE vehicles can also give significant benefits.

1 comment:

  1. An issue you have only briefly touched on in this otherwise excellent post, is that you need to plug in your electric car ("Charging Infrastructure needs to be built"). Because of the range issue, electric cars are viable (for now anyway) only in cities, where the vast majority of people live in apartments with on-street or private parking. There is no facility available to plug in your car, except in a very few places in central London, and the City has cancelled its "free parking" operation 2 years ago (http://bit.ly/dC1CMm).

    Building this infrastructure will be expensive and disruptive. Since there is little hope of our energy being green in the next 20 years, the EV isn't a viable, green and economic alternative. The bicycle is, maybe electric-assisted (you can take the battery out) if you really must use electrons.