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If the electricity to charge electric vehicles comes from dirty sources, how are they cutting emissions?

Electric cars even when powered from coal base power plants are "mostly" cleaner then combustion cars with lots of room to improve when electrical generation infrastructure improves: https://greentransportation.in...

The word "mostlly" is because there are third-world coal power plants so polluting, that even electric engine efficiency cannot come clean when powered from them, however as the provided link shows it's rarity and with time less and less of an issue.

Don't spread misinformation, studies showed that electric cars even when powered by fossil fuels generated electricity are cleaner then gasoline - and this is the starting point, which can only get better with more renewable energy, not to mention direct health benefits for all the urban dwellers and commuters.

https://greentransportation.in... From the article: "... Repeatedly studies have shown even if the electricity comes from coal, electric cars are cleaner than gasoline ..."

Relevant is: how much energy does an EV comsume while [traveling]

I will now attempt some back-of-the-envelope calculations. Corrections cheerfully accepted if I screw anything up.

Desired: a highway that can use solar power to drive all its traffic. We assume all traffic is electric cars of comparable efficiency to a Tesla Model S. (Note: the article specifically said that the road was to have no heavy trucks on it.)

Rule of thumb: one kilowatt-hour is good for about three miles of driving. (It's actually a touch higher than that but reasonably close to 3, and 3 makes the math easier.) So assume we need something like 330 watt-hours per mile. Converting to metres, we need about 0.205 watt-hours per metre.

But we can't wait an hour to get it... at 60 miles per hour it takes one minute to drive a mile, and one second to drive 1/60 of a mile. Converting to metres we get 26.8 metres per second. Therefore in a second of driving we will need 26.8 * 0.205 == 5.5 watt-hours. There are 60 minutes in an hour, 60 seconds in a minute, so 3600 seconds per hour. To deliver 5.5 watt-hours in one second we need 5.5 * 3600 watts, or 19800 watts.

If Solandri did the math correctly, we get about 0.336 Watts/m^2 from the road. A standard highway lane in America is about 3.5 metres. Therefore for each metre of lane we can hope to gain 0.336 * 3.5 == 1.17 watts.

To get 19800 watts from such a highway we would therefore need 19800 / 1.17 == 16900 metres of lane per car.

Except that we are talking about driving the cars in real-time with an inductive charger. We need to account for the efficiency of the inductive charger. Let's assume an inductive charger can be 75% efficient (which I think is very generous... it's at the high end of numbers from this paper), then we would need about 22500 metres of lane per car. That's one car per 22.5 km (or one car per 14 miles).

Let's work it the other way. I was taught that for safety I should not be closer than 3 seconds of driving time to the car in front of me. If everyone uses that rule, how many metres of road will one car take up at 60 mph/96 kph? 96000 metres / 3600 seconds per hour * 3 seconds == 80 metres

(Note: let's assume that 80 metres is always enough. When cars drive more slowly they pack closer together, with the worst case being bumper-to-bumper traffic where the road is tiled with cars. But electric cars get more efficient when they drive more slowly, so let's just assume it all works out. I feel I've done enough math already.)

So we need 19800 watts from 80 metres of road at 3.5 metres width... we need 19800 / (80 * 3.5) == 70.7 watts/m^2 (about 210 times more efficient than what Solandri calculated).

Or, factoring in a 75% efficient inductive system we would need 94.3 watts/m^2 (about 280 times more efficient than what Solandri calculated).

So we need a solar panel setup that nets 9.4% efficiency in converting solar power: 750 watts/m^2 solar power in, 70.7 watts/m^2 out, 70.5/750 == about 9.4%

Or, factoring in a 75% efficient inductive system we would need a net 12.6% efficient solar panel setup.

Again assuming 0.16 efficient solar cells, we need a capacity factor of about 0.588 to make it work, or 0.786 assuming the inductive system.

If we put solar panels on roofs over highways, it looks to me like we can come surprisingly close to break-even (being able to power the cars on the road purely from the solar panels). If you assume the panels are a bit more than 16% efficient maybe break-even is possible.

But burying the solar panels in the road under translucent concrete means you don't get 100% transmission of light to panels, and you can't angle the panels to improve capacity factor. Also your capacity factor takes a hit as cars put panels into shadow. (If you ever permi

Lets do at least a bit of math here. My starting assumptions are:
1) the statement about Poland's emissions -- at 650gCO2/kWh -- is correct
2) a typical electric car needs around 20kWh/100km (that's a number I remember from some real life tests in recent years). See https://greentransportation.info/energy-transportation/kwh-evcars-gizmos.html for example.

Then the 650gCO2/kWh translate to 130gCO2/km in terms of CO2 emission. Which is about the same a fairly economical IC car produces. Other countries than Poland may be much better if they use a lot of regenerative energies.

That means they are only a battery capacity factor of 2-4 away from range parity.

If you only care about range, then my 6-cylinder 2007 RAV4 has an estimated 300 miles average range, and the beefiest Tesla Model X has a 289 mile average range, so we're already roughly at parity as far as I'm concerned.

BTW, the efficiency numbers for gasoline engines get even worse when you factor in the supply chain. For every gallon of gasoline refined, it takes about 6 kWh of power to refine, plus a lot of fossil fuel power to extract and transport. That same amount of energy input would get an electric car almost half as far as the gallon of gasoline would, even before you factor in the energy in the gasoline. So your overall efficiency is likely to be more on the order of 20%.

Of course, you're moving around more weight with the EV, because they don't get lighter as they discharge, and their specific power (energy per unit weight) is only about 1/50th that of gasoline. When full, that 14-gallon tank of gasoline weighs ~87 pounds plus whatever the plastic tank weighs (15-20 pounds, typically). So assuming you get it near empty every time, it weighs on average about 44 pounds plus 15-ish. Let's call that 60 pounds.

The Tesla pack weighs 1200 pounds. And the rest of the Model X weighs about 500 pounds more than the RAV4 in question, for a total difference of a whopping 1700 pounds. If the ICE-based car weighs only 68% as much as the electric, then instead of being ~5x as efficient, the EVs are only ~3.4x as efficient. Of course, this discounts the efficiency/inefficiency of producing electricity, but that's hard to quantify.

The sources were quoting what the refineries reported they use to refine a gallon of gas, somewhere between four and six kilowatts in addition to any eating of their own dog food. If they weren't making gasoline, that fuel would be available for electric generation, and the difference is even greater. Here's a nerdier link. There are even worse examples, such as getting oil from Alberta's Oil sands, which apparently requires 300 KWh to heat enough material to produce a barrel of crude oil, or about 7 Kwh per gallon of crude, which gets you less than half that after refining. so then we are talking about 14 Kwh to get the oil sand into crude, then another 7 Kwh to refine it, and then add in the transportation.

This wouldn't help all energy markets, but oil refinery takes a large amount of electricity. The more EVs that are out there, the less oil is refined and therefore less electricity is used. Some estimates put the amount of electricity at 6kWh of electricity for every gallon of gas.

This amount of electricity translates to roughly 15 miles of driving in an EV. Whereas with a gas powered vehicle, you may get more or less distance on that gallon of gas depending on your mileage.

So, replace a high mileage car with an EV and electricity use will go up, but not as much as you would think. Replace a low mileage car with an EV and electricity usage stays the same or even improves.

Meanwhile the price of electricity is likely to go up, as the massive vehicle energy consumption shifts to the grid.

Except as gas demand goes down, less gas refinery will happen. As it turns out, gas refinery takes a lot of electricity. If you stop doing this, you actually would make up most, if not all of the electricity needed to power the EVs that would replace the entire gas fleet.

https://greentransportation.info/energy-transportation/gasoline-costs-6kwh.html

http://greentransportation.inf...
"Shows a picture from Nissan's tour of the Nissan LEAF where Nissan claims it takes 7 kilowatt-hours to refine a gallon of gasoline. Nissan says that same 7.5 KWH can drive the LEAF 30 miles."

Natural gas is also used in some refining of gasoline from oil..

So basically, the oil pumped from the ground in Middle East and transported via huge oil tanker ships is essentially in effect just used as a carrier of the electricity which was used to refine gasoline for internal combustion engines... So much US defense expenses (100s billion US$ annually), so much pollution, so many lost lives -- all essentially to use oil as a crappy battery for cars? Glad things are getting better.

The figure came from articles like this. The issue is that the 6KWhr/gallon is energy loss and not energy use. Some of that loss is in heat and other waste. If you look at just electricity consumption it is closer to 89Whrs/gallon.