Comments by "Winnetou17" (@Winnetou17) on "Thunderf00t"
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Well, Thunderf00t did mention a bit about that.
So, you need roughly 1 MWh of energy for a full load of the semi.
And in decently good conditions, you can about an average of 10 hours of peak time for solar panels.
So to get 1 MWh of energy in a day, you need 100 kW worth of solar panels, that in 10 hours (well, in more than that, but in average) will gather 1 MWh.
So, solar panels are usually 20 to 22.something percent effective. That is, they can gather about 20 something of the incoming solar energy which is around 1kW per square meter in a normal bright sunny day. It can go a bit more than that, though not by much. And when very bright, you usually have the problem of cooling the panels, otherwise their efficiency drops when overheated.
So, let's assume the panels are at 25% efficiency. That means than 1 square meter of that can generate 250 W, so in one hour it will get 250 Wh of energy.
Simply put, 4 square meters make 1 kW.
To get to our 100 kW worth needed, we simply need to multiple the above figure by 100. So a megacharger needs gasp 400 sq.meters of good solar panels, and to run in good conditions, which California does have, but the northern part of USA and most of Europe (or rest of the world, really) do not.
Now, usually a solar panel is bigger than a square meter, but less than 2. So the number of typical solar panels would be between 200 and 400, with a strong bias to be around 300, I'd say. Actually, if the conditions aren't that great or the efficiency is not the 25% I used... well, then having 400 might actually be the more realistic number.
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Nice, thanks for the info! Some others pointed that those barriers are actually heavier. I have no idea and I'm lazy to investigate myself, but it might be possible that the cargo is closer to 20 tons. On that idea, if the battery itself adds, at most, 6 tons extra than a diesel engine (7 tons battery, 1 ton less in engine+extras weight), why would it carry 10-14 tons less ? It doesn't make much sense. So I don't think that the drive and steer weigh 60000+lbs.
Also, please split your text a bit. It's a wall of text right now. Readable, but not confortably so, once you passed the 2nd row.
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@crocodile2006 Ok, ok, thanks for that.
Sooo, let me quote "Recover up to 70 percent of range in 30 minutes using Tesla’s Semi Chargers". UP TO :))
Also, what numbers do add up ? If the battery is 1000kWh, then 70% of that is ... 700kWh. Charging 30 minutes from a 1000 kW station will give you ... 500 kWh.
You might say, well, the battery is not actually 1000kWh, it's less because it needs less than 2kWh per mile. In the video they said 1.7 or 1.8 kWh per mile. Using 1.7 kWh (and we don't know the conditions for that, only that it was a full weight) per mile, in order to do 500 miles we'll need 1.7 * 500 = 850 kWh. 70% of that is 595 kWh. Which is 20% more than the 500kWh that 30 minutes at 1MW. These "numbers match" to you ???
Really, I think that the 70% figure is for the 300 mile variant. Or in a "best case" scenario, where you use much less than 2 or 1.7 kWh per mile, but it's not the average (or anything that you can rely upon)
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Holy crap, I really hate to do this, but the calculations at 9:00 are really off.
Let me put it in another way. Let's actually compute the energy needed for a 36 t vehicle going at 60 kmph for 901 km (560 miles for the cavemen out there).
Using the computing method as shown by Engineering Explained's video named "Why Teslas Are Bad At Towing (Today)" (search it here on YouTube) from 4th December 2019, and using the following assumptions: drag coeficient is 0.6 (what I found is typical for a truck, after a quick search), the same 3.7 sqm area as in the EE's video (40 sqft for the neanderthals out there that somehow know to read) which is almost 2 by 2 meters, and a rolling resistance coeficient of the same 0.015, which seems actually to be pretty conservative, I've found lower estimates after a quick search on the web. Also these 901 km are on completely flat land.
Formulas used: on short, the total force needed is Fa (force to overcome aero drag resistance) + Fr (force to overcome rolling resistance).
Fa = 1/2 * p (density of air, in kg/m^3) * v^2 (speed of the vehicle, in m/s then squared) * Cd (coefficient of drag resistance, unitless) * A (area displaced, in 1/m^2)
Fr = G (vehicle's weight, which is mass * g, in N) * Crr (coefficent of rolling resistance, depending on tires and the surface, like asphalt, unitless)
Then the force is multipled by the distance, to find out the energy in Joules and then I converted it to kWh, since that seems to be used more in these kind of discussions.
So, after doing the calculations, the energy needed is 94.94 kWh for the Aero drag resistance and 1325 kWh for the rolling resistance. For a total of 1420 kWh energy needed to move a 36 000 kg vehicle on flat asphalt for 901 km. And taking the current usually used estimate of 0.25 kWh per kg energy density of Li-ion batteries, we end up with a battery which has 5683 kg, so 5.7 tonnes.
I wouldn't say I used optimistic numbers. And even for this truly unneeded long range of 900 km, the battery is much lower than "8-16 tonnes" nonsense.
If the truck would go at 100 kmph then it would need 1589 kWh of energy, or 6358 kg of batteries.
If the truck would go at 60kmph but just for 400 km, then it would need a mere 630 kWh energy or 2523 kg of batteries.
As if it wasn't enough, there's one more thing that makes this even better, and can be seen in the Honda Accord vs Tesla Model 3: the car weight, without the batteries. The Tesla one vs Honda is 300 kg less. That's because the electrical engine is smaller and there's other stuff that's simply not needed. I expect this to be the same in a truck, and something like 1000 kg to be shed from a normal diesel truck when getting it to be electrical. So this means that the extra weight will be about 3-5 tonnes. And probably the range a bit smaller. But it's still up for 15 tonnes of payload or 25% less which might be less than the other economies of going electric. In other words, I can totally see this working.
Please Thunderf00t stop these cringe calculations and most importantly, stop giving musktards fuel for refuting you or your points and videos. You represent the science community and this 8-16 tonnes of batteries bullshit is just... sad.
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