Wednesday, April 06, 2016
Although it is written by a fan of electric cars, I find this blog post
by Jacques Mattheij to be quite informative about the many practical
problems associated with them. Among other things, he notes that their
vaunted power efficiency isn't all it's cracked up to
Regular ICE's [internal combustion engines --ed] are terribly inefficient, as low as 18 to 20% on average. On paper, EVs do much better than this but in practice that advantage is somewhat diminished. There are for instance the charging losses to contend with, around 20% or so. Electric motors (the prime mover in an EV) are much better than ICEs in converting energy to motive power at 80% or better, so less energy would be required from the charger to the vehicle to achieve a similar distance traveled. But because it is the total system efficiency including generating losses at the power plant and transportation losses in the grid in the end that theoretical 80% ends up being much lower (if the power source at the generating plant is a gas turbine for instance the efficiency of the generator is in the very best case 60% but more realistic would be about 50% and further losses in the grid would be another 6.5% or thereabouts. Total system efficiency would then be .5 x .8 x .935 x .8 or roughly 29%. Still much better than the ICEs this all replaced but not quite as good as it looked initially. So 68% (20 (ICE) / 29 (EV)) of that original 28%, or 20% extra energy would have to be generated by the utilities and transported through the grid to the charging stations in order to accommodate all transportation to be electric. [minor edits]As to why the market hasn't adopted this more efficient technology en masse already, one need only consider the list of problems that follow this admission. I will list Mattheij's bullet points, but do note that he elaborates similarly on each:
- Transportation will load the grid and generating capacity in rather nasty ways.
- Rapid charging is actually not so rapid, highway re-charging stations will have to be much larger than current gas stations.
- Gas stations are not generally in the neighbourhood of electricity generation stations.
- Re-charging will not work nearly as well when vehicle utilization goes up due to sharing.
- We don't actually have all this infrastructure yet.
- Tax breaks.