One of the biggest reasons for anyone to be reticent about switching to an Electric Vehicle is Range or rather lack of it.
“I’m not buying an EV until they can go 500+miles in a single journey like my current car can”
Rather than try and argue against that viewpoint, I wanted to spend some time looking at why Electric Vehicles have less range than their Internal Combustion Engined (ICE) counterparts.
Fundamentally, it’s about density. The fuel source in each is very different. Let us compare two similar vehicles. The Tesla Model 3 is comparable in size, cost and market segment to the BMW 3-series.
In a Long-Range Tesla Model 3, there is a 75kWh Battery. Rated at 348 Miles (WLTP)
In a BMW (G20) 330d There is a 59 litre Fuel Tank. Rated at 44.1-47.9 mpg (WLTP)
To compare the two like for like we need to convert the 59 litres of diesel to kWh. As 1ltre of Diesel = 10.7 kWh of energy, the BMW, therefore, carries up to 631kWh of energy.
The battery pack in the Model 3 is made up of 4,416 cells arranged in groups of 46 and weighs 480 kg. Which equates to 156Wh/kg (or 0.156kWh/kg)
The fuel tank in the BMW weighs around 10kg and 59 litres of Diesel (0.832 kg/L) weights 49kg so all in around 59kg. Which equates to 10.7kWh/kg
Wait! What?
Diesel is 68 TIMES the energy density of the Battery?????
Why then does the Diesel car ONLY go up to 622 miles on a full tank compared the Electric cars 348 Miles? That’s where we have to talk about efficiency.
According to Interesting Engineering A Petrol powered car only converts about 17%-21% of its stored energy to power at the wheels. Diesel is better, but no figures are quoted. However, an EV can convert between 85% and 90% of the electricity stored in the battery for the motor. Also, as energy density is such an issue, EV manufacturers go all-out to make their cars as drag efficient as possible. Retractable door handles, camera door mirrors, aero wheel designs and low rolling resistance tyres are all technologies that are being driven (no pun intended) by the EV designers. They also don’t need to have large frontal areas with radiators to disperse the heat generated by an ICE.
So, we may or may not care or have an opinion on the overall emissions of an EV, be they tail-pipe or full cycle. What we cannot argue with is that the EV is a much better converter of energy and the range factor is predominantly an issue of energy density.
Battery density is increasing at a significant rate. Some manufacturers quoting a doubling every 3 years, others, triple every 10. The energy density of Diesel is static.
So, while we won't see comparable density to fossil fuel, it will not be long before comparably sized vehicles will be capable of comparable range to their ICE equivalents.
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