OK, Tesla maths, based on their stated charging efficiency of 92%... - motor/controller efficiency isn stated, but Ill assume a city average of 80% - grid efficiency is a trickier one but is usually better than 90%, Ill say 95% - power station generator efficiencies are typically around 90 to 95% while - the energy source can be between 70% for fossil fuels and 90% for hydro and wind - Ill average efficiency, based on 80% coal, 20% renewable at (4 x 0.7 + 0.9) / 5 = 0.74 or 74% So, being generous, thats 0.92 x 0.8 x 0.95 x 0.95 x 0.74 = 0.49 or 49% efficiency in terms of the energy applied at the tyres as a percentage of the energy in the coal burned. A modern, electronically fuel injected car can manage city cycle efficiencies of 35 to 40% of the energy in the petrol or diesel, but produce about 2/3 of the particulates and CO2 coal produces for its heat output. So, until all coal-fired power stations are removed from the earths surface and are replaced with wind and hydro* (or nuclear, nuclear energy is cleaner than any source currently produced, and thorium pebble bed reactors CAN NOT GO CRITICAL), the Tesla is no more a zero emission vehicle than an internal combustion car of the same size and weight, and I havent even addressed the issue of battery life and the carbon production in mining and manufacturing the lithium and its difficulty and energy consumption (and further CO2) to recycle. Its a cool bus, but its not zero emission yet. Thats up to governments and energy suppliers.
Posted on: Sun, 28 Sep 2014 01:54:10 +0000
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