mjr wrote:kwackers wrote:Typical efficiency of EV's is 4 miles per kwh.
An hours cycling by a moderately fit cyclist is probable around 200w
So if a moderately fit cyclist does 12mph average, does that mean a cyclist does 16 2/3 W/mi and an EV does 250 W/mi?
So an ebike may be 20W/mi due to the extra weight but probably a higher average speed? I suspect an e-recumbent may be the optimal efficiency, with the motor overcoming the notorious disadvantage on hills.
Let's get the units correct, It really helps.
A watt (W) is a measure of power - energy per second. A watt hour (Wh) is a measure of energy (i.e. work done). Both often have the prefix k for kilo.
An ev does ~4m/kWh so 250Wh/mile
A cyclist at 200W doing 12mph would be doing 12m/200Wh or 17Wh/mile
In other words that cyclist uses 15 times less energy than that car (which makes some intuitive sense, the mass difference is about 15 times 100kg vs 1.5 ton). I would wager 200W will net you more than 12mph though...
BC article wrote:Wind tunnel testing has shown that a 70kg cyclist putting out 200 watts of power would be traveling at 32.4kph if riding upright on the brake hoods.
That suggests 18mph, so 50% more distance per watt hour - 11Wh/mile
In reality I expect the value to be between those two values, but the cycle is more efficient (again, intuitively makes sense, it is a much simpler vehicle).
What that really highlights is how inefficient an ICE is... 1 gallon is about 34kWh - so a car that does 50mpg at 50mph is doing 700Wh/mile (three times more energy than an ev).
Yes, I know I'm ignoring both refinery costs for the petrol (about 10% more energy), and the costs of extraction (5-20% depending on the source
*), as well as electricity production costs and transport/conversion losses.
My very hand wavy, based on an absolute minimum of research, excuse is that they are probably a wash, or even give the ICE a slight advantage in the comparison. That advantage will only grow as the proportion of electricity production in the world moves towards more sustainable production.
Anything below ~20mph (fairly old study) is generally particularly inefficient for an ICE as well - the energy required just to keep the engine running starts to become significant (most obvious at 0mph, where they are still using fuel).
Short journeys are also generally a killer for an ICE, but don't really affect an EV much (depending on ambient temperature and battery conditioning on an individual vehicle)