Why I like Electric Cars

And why you may have to avoid buying one, if you really care about the planet.

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None of the reasons why I like electric cars has to do with them being "green", but for one that is really more  - "I like to breath without assistance" - which, for me, is a supremely egoistic one.

I like electric cars because the battery plus +electric-motor-on-board-electronics assemblies exemplified by the Tesla allow some innovative design, with a very low centre of gravity and consequently good handling.

In this, the Tesla shows a direction, although their design is still pretty tame, confronted with what could be done (in fact, I remember a GM concept some  years before the Teslas, that used the battery in the bottom and small motors much more audaciously... it never made to production, as entering an essentially "void" car was slightly upsetting).

I like electric cars because the electric , asynchronous motor they use is one of the simplest machines known to man - all the sophistication of the drive-train is in the power control circuitry and that, mostly, can be derived by the power control studies that move most industrial machines.

I like electrics because they allow AWD design with negligible loss of efficiency - maybe, even with a gain! -  when compared with the 2WD version, and completely arbitrary power-on demand distribution on each wheel.

This because, in an electrics, a small motor can be used to drive a single wheel, and having 4 motors working in parallel - each with the same efficiency - makes not much difference, whereas in an I.C. vehicle the kinematic chain must be lengthened, adding stages in which losses have to be added.

More exactly, efficiency in a parallel process is given by the weighted mean of the sub-process efficiency, in a cascade chain - like in a classic AWD -  it is given by the product of each successive stage, and ass efficiency are necessarily always < 1....

So, with the right design, the 1motor-1drive wheel can have even better efficiency than 1 motor-differential -2 wheels, because the differential is just one added kinematic stage... of course, the cost is a bit more for the independent motors solution.


I like electric cars because they can be ridiculously overpowered, with respect to normal use, without this incurring the excessive augments of the running costs that is typical for overpowered I.C.E.

In E.V.s the main limits in terms of maximum power and efficiency are given by the battery and, the highest the capacity of the battery the highest the autonomy, the better the maximum continuous power and the efficiency of the discharge in normal use (but, the bigger battery, the bigger the weight and cost of it, so a compromise must be found - that's called engineering).

Again,  the Tesla S and X show both these possibilities, having motor assemblies back and front as well as an absurd combined motor maximum power, but still fall short from ideal in keeping a differential in the mid  each axle, instead of using an independent motor for every wheel (which would allow instantaneous torque vectoring at a marginal cost).

The mechanical simplicity of electric vehicle (even in a 1 motor per wheel design) may allow for substantial  reductions in terms of maintenance needs.

After all, chances are that you are reading this on a computer whose cooling fans have run 8 hours a day, every day, for the last one to eight years, without an itch... that's what the computer I write this on did, in effect - it is about 18000 hours (I had to change the CCFL of the monitor a while ago, so it is about right, as those last more or less that) or 400.000 km.

Electric cars drive-trains are, really, only oversized versions of those fan's brushless motors.

Done well, we should expect E.V. that require a change of the reduction gear oil, and other fluids, every five years, and of tires and brake pads only depending on the owner's craziness (I had a friend who trashed both in some three thousand km - 2 k miles, to be generous).

Now, many argue that E.V. are illusory un that they "move" the pollution from the tailpipe to the power plant. It is fundamentally right.

But, I have lived most of my youth in an area that managed to be among the most polluted of Europe and, maybe, the world. A place where older cars are allowed to circulate only during the weekend, and at each new "Euro" rules enforced the "old car" limit was moved forward, and electricity os often imported from nuclear plants in Switzerland and France..

In such an area, having an electric car may help avoid your neighbour - or you - some respiratory disease.

Finally, while nobody would like the idea of a gasoline car that fills her tank by herself when one parks it in the garage, mostly because we do not fancy  the idea of hundred of litres of gas at children's arms length, I can imagine an electric car do the same, with a sufficiently "smart" plug that wouldn't OK the charger to switch on unless it was plugged all well in.

(Years ago, I saw a project for self-driving city-cabs that used inductive pads as the "electric plug"... the little boxes only had to park themselves above a pad, no plugs or other moving parts involved; if it was workable, it would be a neat way to have self-charging EVs).

At that point, while the electric vehicle range may still be limited, who wouldn't like a daily drive that one never has to take time to refill?
  
Now, why should someone avoid buying an electric car, if he cares for the planet?

It boils down to where, and how, the electricity to fill the battery is produced, as well as the current efficiencies of batteries and such.

The electric motors and the electronics that drives them are fairly efficient  - typically, a least 90% and usually more, outside the two limits case of launch and over-rev where efficiency falls to 0 .

Then there is the battery charge-discharge cycle, the electronics in the charger station, and the electric power lines .

Li-Po battery charge-discharge efficiency can be as high as 99%, typically for slow charges. For somewhat faster charges, the efficiency drops.

The same can be said for the discharge - slowly done, coasting at speed limit on the highway, it probably hovers back in the high 95%. In a Tesla S, in Ludricous Acceleration mode, probably it is more an 80%.

The power grid delivery efficiency is not so high, around 70%, but it depends a little on the sophistication of its controls system and a lot on the distance from the production centre,

Now, you'll have seen a lot of "about" in this part.

Because, really,  there are a lot of details that influence each point, what Robert McNamara called "hard data" - independently measured,with a well defined methodology and verifiable -  are hard to come by and, as a result, more than calculus what they led to is... sophisticated confirmation bias.

So, going around the web, depending on what the writer of each article is aiming to, these data can be - and usually are -  "massaged" one way or the other.

As these are all efficiency in a chain process, they must be multiplied - remember? - and sliding some % point one way or the other ends making huge differences.

So, let's be optimistic, but not too much.

Drive Train	Motor	Inverter	Battery Charge	Battery Discharge		Charger Station	Grid Lines	Power Plant
95%	95%	95%	95%	95%		95%	70%	50%

One gets 24%, which compares favourably - but not so much - with petrol cars wheel-to-well efficiency, that most sources seems to agree being about 16%.

 Replacing all those 95 with 90, one gets 18%... Tossing in a couple of 80% - which, by the way, may be justified simply by a owner that has a heavy foot on the accelerator!!! if one thrashes ires, that is energy that disappear in rubber smoke, and battery heating up for the fast discharge... - one can easily come to the conclusion that the environmental friendly electric car gives a whopping 14% efficiency.

And, by the way, if you live at a distance from the power plant and this is a coal fired one, it is true... a small petrol car is the greenest choice you can make.

So, the electric cars will not save the Earth?


First of all, they would never have. It is our hide, as a species, that is in danger.

Long after we'd have produced the greatest mass extinction ever and wiped out ourselves and every mammalian plus some other cordata, the planet will still be here and have some inhabitants.

 One of those will spur the next "great species" - or not. The planet can't care less, one way or the other.

Second, as I said, the effective "greenness" of EVs depends on a host of factors - by far, the most important the type and location of the power plant, and any significant change can tip the situation.

For example, I live in one of the most underdeveloped areas of Europe, a place where hundred of Aeolian Generators spin under a near constant wind and the electric grid had - for years - problems in accommodating this kind of unreliable, exuberant power source.

Buying an electric car here would be a no-brainer, but for the fact that almost nobody feel it is needed to avoid pollution - underpopulated and under near constant wind from the Atlantic, the air is perfect as it is -  a bit because the under-population forces to move a lot to get things done, and mostly because there is not a single charging station in a couple hundred miles. 


In Chile, where they are slowly filling the Desert of Atacama - the driest, sunniest place on Earth - with solar cells, it is going to become a no-brainer in some years.

In California... outside the most polluted urban areas, it is not really such a great idea, as the current mix of electricity power plants is not so ideal...

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So, if you really feel "green", before you go and buy a Volt, get informations on where and how the electricity you want to feed to your horseless carriage is made, and then sit to make some calculations...

You may discover that one of those small turbocharged petrol beast, horrible little shiboxes that they make today is really the greenest option available were you live.

Waiting for the technology of - and infrastructure for - EVs to catch up.