Comment by 3eb7988a1663
8 hours ago
That's not quite what this is about. It is the Primary Energy Fallacy, that if you are to replace eg coal, you need to replicate its original energy content.
If 1kg of coal represents 1000 Wh, your generator loses 1/2 to waste heat, you only generate 500 Wh of usable electricity. Some analyses will state that renewable power has to replace the 1000 Wh of embedded energy within the coal, when it only needs to output 500 Wh.
If you use solar panels and generate 500 Wh directly, you have cut your energy use in half, even though the output has remained the same. An EV has a battery of ~80 kWh, equal to 2-3 gallons of gas, yet it can go a few hundred miles, a 3-4x ratio of efficiency, compared to an ICE.
Electric motors have gotten ridiculously efficient. In the right power curve you can hit 95%, which is why we have now moved onto power per unit weight and unit volume. You make the drivetrain lighter you reduce the power needed for 0-60 times, which gets you a few more percent of efficiency.
Same thing with battery power density - it’s the rocket equation. Heavy batteries don’t go far. To go farther you add battery, then more battery to carry enough power to carry the larger battery. Increase the specific energy rather than the mass, and all the extra power goes into going faster or farther.
I think your EV example is a better example than your coal one.
I’ve never seen anyone measure coal power by the amount of chemical energy stored inside, unless they are specifically referring to using it as a heating source. For electricity generated by coal it’s always measured as output.
The battery loses 10% just by charging it.
I figured an EV is worth about 60mpg with a fair comparison to a gas car.
A good visualisation for this I think are linked. Petrol/diesel use about 20% of the available energy and electric vehicles use about 80-90% for moving the vehicle.
https://yaleclimateconnections.org/2024/01/electric-vehicles...
A litter of petrol is about 34MJ or about 9.5kWh
It propels a car about 10 miles. About 1 mile per kWh
Charging my electric car via AC at 7kW to replace the power used to drive 90 miles in autumn takes 26kWh according to the meter, so 3.5 miles per kWh.
Oil also loses quite a bit during refining and transport.
And more every year as the highest quality oil gets used up and we have to work harder to catalyze the rest.
> An EV has a battery of ~80 kWh, equal to 2-3 gallons of gas, yet it can go a few hundred miles, a 3-4x ratio of efficiency, compared to an ICE.
Now compare size and weight of the battery with 3 gallons of gas. I can carry hundreds of miles of travel on my person if it's gas, I can't carry much battery though.
> I can carry hundreds of miles of travel on my person if it's gas, I can't carry much battery though.
Particularly handy if heading off in a straight line, I to the wilderness.
Most of us are running errands around town.
That's true, we should clearly be powering our cars with uranium, or perhaps plutonium.
Have to wait for Mr Fusion l
How about antimatter?