Electric vehicles are eco-friendly and zero emission! NO. The lack of noise pollution and tailpipe emissions make electric vehicles appear to be eco-friendly but then there is the question of what is powering the electric vehicle Electricity and how this electricity is being generated.

As a mechanical engineer, if I simplify the logic and elaborate the topic almost 69% of electricity in India is generated by thermal power plant (burning coal, oil and natural gases), 17% by hydro power plant, 12% by renewable energy sources and 2 % by nuclear. Solar energy is still in development phase, especially to make it cheaper and more efficient to run high voltage accessories e.g. TV, fridge and Air-conditioning etc. Wind, tide and geothermal energy sources have less scope in India. Nuclear has minor security concerns and is still a nonrenewable source. So thermal will be the prime source of electricity generation in India for at least next 30 years.

By the second law of thermodynamics, no engine/turbine/energy-work cycle has 100% efficiency, which means-

-          The heat engine at the power plant which produces the mechanical energy is a Carnot cycle engine, limited by the inherent inefficiencies of the Carnot cycle.

-          The generator that produces the electricity from the mechanical energy is not 100% efficient.

-          The transformers which step up the voltage to the transmission lines are not 100% efficient.

-          The transmission lines themselves are not 100% efficient.

-          The transformers which step down the voltage from the transmission lines are not 100% efficient.

-          The local distribution lines are not 100% efficient.

-          The transformer on the pole outside the houses which steps down the voltage from the local distribution line is not 100% efficient.

-          The charging process for the batteries in the Electric Vehicle (EV) is not 100% efficient.

-          The discharging process for the batteries in the EV is not 100% efficient.

-          The electronics which regulate the power going to the drive motor(s) in the EV are not 100% efficient.

-          The drive motors in the Eclectic Vehicle are not 100% efficient.

In general, the efficiency of thermal power plant varies between 30- 45 % and it also produces tons of ash, harmful gases, waste water and other solid waste. So the electricity driven vehicles are also the reason of increased waste and green house gases. By the time we add up all the inefficiencies in the complete system driving the Electric Vehicle, the internal combustion engine hooked directly to the wheels (as in a car) is more efficient. It's that simple.

For easy comparison, we calculate the data of grams of equivalent carbon dioxide per vehicle kilometer (g CO2e/km) for a full electric vehicle, similar to a Nissan Leaf, in 40 countries. Each estimate includes emissions from vehicle manufacturing, power station combustion, fuel production and grid losses. For each country vehicle manufacturing emissions are assumed to be 70g CO2e/km, based on a number of studies.

Of the 40 countries covered, emissions vary from 70g CO2e/km in hydroelectricity loving Paraguay, up to a 370g CO2e/km in heavy coal based electricity generation country India.  The US average is 202g CO2e/km, in China it is 258g and in Canada 115g.

In Paraguay virtually all the emissions are from vehicle manufacturing, as the power is incredibly low carbon.  Whereas in India the breakdown is 70g for vehicle manufacturing, 200g from power plants, 30g for fuel production and a whopping 70g for grid losses. So even after same vehicle manufacturing emission, the carbon intensity of driving an electric car varies 5 fold based on the type of major electricity generation process and quantity of CO2 emission during this process.

The vehicle manufacturing of a gasoline car is just 40g CO2e/km compared to 70g CO2e/km for the electric vehicle. In comparison with the United States’ average of electric vehicle emission of 202g CO2e/km, the average American gasoline vehicle is up at about 300g CO2e/km, while a new hybrid might manage 180g CO2e/km after including vehicle manufacturing, fuel combustion and fuel production.

So in coal heavy India, China, Australia and South Africa electric cars using grid power are just like typical gasoline vehicles.  In the UK, Germany, Japan and Italy they are as good as the best petrol hybrids vehicles. But only in low carbon supply places like France, Brazil, Switzerland and Norway, electric vehicles are able to advance the petrol cars and prove themselves as an eco-friendly vehicle. So still we need better electric generation resources for the world, before using it to drive the electric vehicles.