- First Name
- A. J.
- Dec 8, 2019
- Reaction score
- Tesla X LR+, Lexus SUV, Toyota SR5, Toyota Landcruiser
- EE (Retired)
Lot's of people think AJ is nuts because his numbers don't come out to 15 miles for just toneau panels. Elon didn't say you would get 15 mi per day. He said you could get as much as 15 miles per day. Let's think about that for a minute. Suppose you live in the desert at 20N latitude. At the spring equinox here's what the sun does:I think ajdelange calculated about 2.5 miles per hour in optimum conditions. so 8 hours In direct sun for about 20 miles minus "phantom drain" so maybe 15?
seems wierdly low as elon said 15 for JUST the vault panel.
The blue curve shows the elevation of the sun and the red one the relative intensity of the collected radiation assuming that you keep moving the truck so that the panels are pointed directly at the sun. Whenever the sun is above about 65 ° you get close to it's full intensity (1.00) but when it is below that you start to lose some because of atmospheric absorption. The integral under the red curve gives the equivalent hours of full sun which, for this picture is 10.325 hours. Let's assume the CT is going to consume 350 Wh/mi. For 15 miles of driving that would mean 5250 watt hours consumed. If we have 10.325 equivalent hours of full sun we would need panels that produce 5250/10.325 = 508 watts when in full sun, That's the production of 2 of the panels going onto roof tops today. Thus if you live in a sunny desert 15 miles a day doesn't seem unreasonable.
Now let's go to where I live at 39N. Here's what the sun does on a January day:
The sun does not rise as high in the sky and isn't up as long so the received insolation is less both from less time shining and greater extinction losses. Plus, as it isn't practical to go out and reposition the truck to "track" the sun this picture assumes the truck is parked for the whole time the sun is up with the panels oriented south and inclined at 60 °. The result is that the effective time of full sunshine are only 4.11 hours. Assuming the same 508 W panels that would give me 508*4.11 = 2087.88 Wh good for 6 miles per day. Not so impressive as 15 miles, especially when you take out the 10 or so miles worth of phantom drain. But, unfortunately, we aren't finished yet. The sun doesn't always shine here in the winter. Last Jan 17th I actually got 3.05 hours of equivalent full sun and the average per day for the month of January was 1.86 with this last number corresponding to about 2.7 miles per day.
So 500 W of solar cells are pretty useless in January if you live in a temperate zone. But we don't go camping in the winter (though we do go hunting). We go camping in the summer months. At my location on a sunny day near the solstice I should get 7.12 hours equivalent full sun. In June of last year I got an average if 4.96 (the sun doesn't always shine here even in June and it gets hazy too). Five hours per day would give me 7.2 miles for an average day of charging in June around here or as much as 10.3 mi on an optimum Jun day.
Someone will probably chime in and argue that the panels that will go on the truck will be twice as efficient as what is available today. If you want to believe that just scale all the mileages by 2. Some will argue that the CT's will have consumptions less than the current Tesla models. If you want to believe that then scale all the numbers by whatever consumption you want. If someone argues that he can move the sun, put that guy on "ignore".