"but the efficiency of conversion into traction is very poor in a combustion engine and gearbox when compared to a modern digital synchronous electric motor."
First of all I like EVs but (strange as it may seem) also enjoy historic motorsport and all forms of genuine eco technology. And NO I don't work for any oil companies, in fact I would like to see less dependency on fossil fuels and more renewable useage.
The claim that an EV is so much more efficient is, from an engineering standpoint, mostly bunk - it all depends of how that electricity was provided, overcoming the higher environmental impact of EV car production and dealing with weight disadvantages vrs conventional cars. Clearly BMW has gone some way to overcome some of the latter two with lighter car materials and lowered eco impact in Leipzig production, but very little of the i3 is locally sourced and 250kg is still a hefty "fuel tank" that looses capacity with time and recharge cycles.
It is one thing to compare a traditional Hybrid car with an ICE car but quite another to use a Plug In ICE or REX that claims huge MPG but ignores the energy used beyond the plug.
The key to efficiency is lightness and aerodynamics. This has been proven time an again in aerospace and in the Ansari X Prize to achieve over 100eMPG. This was won by Edison2 - with a very small ICE engine:
"neither the Leaf nor the Volt meet the performance, efficiency and emissions requirements of the X Prize"
The US EPA MPGe is plug (or for ICE pump) to wheels rather than power generation or oil drilling to wheels. This leads to poor comparisons in overall energy and pollution impacts.
A fairer comparison of energy transfer would be: electric motor vrs a wheel bearing or the final drive unit on an ICE gearbox. For a UK EV the power is produced at the power station which means mostly coal and then grid losses. Excluding the cost in energy terms of mining coal or shipping natural gas from Qatar, DEFRA stated the average UK generation CO2 to be 527g/kWh which has probably lowered very slightly with increased PV and wind-farm construction.
If you live in CA USA things are much better if you have your own Solar PV or use similar renewables like hydro or wind farms. Some states (like Hawaii) use petroleum to generate the electricity in the first place. The current UK and US fascination with Shale gas probably means we are not going for the most eco friendly options to create energy. And 10 years to build a nuclear power station uses a lot of energy before the plant is even operational.
What if China converted to 100% EVs?
"researchers from Tsinghua University (China) and Argonne National Laboratory (US) found that a large-scale conversion to EVs in China could actually increase carbon emissions, compared to internal combustion and hybrid drives. SO2 and NOx emissions also increase in China with increased use of electric vehicles, although the conversion would decrease the use of oil. Coal-based power dominates the Chinese electric grid, accounting for over 95% of electric generation in some regions and a large majority overall."
So technically EVs have several very long tailpipes - some much cleaner than others.
"A report by the UK Royal Academy of Engineering finds that in order for electric vehicles to have a big effect on climate change the grid in Britain needs to move away from coal towards non-carbon power sources, such as nuclear, wind and wave. As the report puts it, “EVs and PHEVs (plug-in hybrids) can only be as ‘green’ as the electricity used to charge their batteries.”
Some won't like this but it's worth a read:
http://m.wsj.com/articles/SB10001424127 ... 2?mobile=y