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> over 12 hours (i.e, multiple days of charging) to charge a Tesla's 85 kWh battery. The tone is somewhat pessimistic. Full charge every two-to-three days for
by NullPrefix 7y ago
> over 12 hours (i.e, multiple days of charging) to charge a Tesla's 85 kWh battery.
The tone is somewhat pessimistic.
Full charge every two-to-three days for a range of ... what is it? 265 miles? Effectively untethered car if you only need 50 miles daily.
- duskwuff 7y agoAgain, keep in mind my numbers are assuming a large, perfectly efficient solar panel under ideal conditions. Realistic numbers will be much worse. For example, most commercially available solar panels are 20-25% efficient.
- NullPrefix 7y ago1.3kW/m^2 * 20% efficiency = 260w/m^2 260w/m^2 * 5m^2 = 1.3kW 1.3kW * 4 hours daily sun = 5.2kW/day 265 miles range / 85kW full charge capacity = 3.1 miles/kW 5.2kW/day * 3.1 miles/kW = 16.12 miles / day Still sounds too good, what did I miss?
- thfuran 7y agoThat initial 1.3kW is ignoring atmospheric absorption. You lose some 300 W even at zenith without clouds. More if you're really far from the equator and/or it isn't currently solar noon. If you're in a city, you may be in shade a lot and certainly don't have the sun at its zenith for 4 hours regardless.
- Mvhsz 7y ago5m^2 is too big for a car, and the panels are heavy and expensive. Toyota used to have a prius with a solar panel roof - it produced enough energy to run the fans (not the AC) while the car was parked on a hot day. Not even in the ballpark of the energy needed to move the car (and it was an expensive option).
- txcwpalpha 7y ago16.12 miles a day is not going to cut it. In your previous comment you suggested 50 miles a day. In various studies, Americans drive >30 miles a day. 16 miles would hardly even cover most American's one-way commute, let alone any other errands or trips.
- NullPrefix 7y ago>you suggested 50 miles a day /s/suggested/calculated using data provided by parent comment/
- txcwpalpha 7y agoNobody in the entire comment chain brought up distance except for you, which you kicked off by suggesting 50 miles daily usage. Regardless, even your drastically lower 16 miles a day isn't going to satisfy the needs of the average driver.
- adrianN 7y agoAffordable solar panels don't get 260W/m^2 peak. The solar panels on a car don't track the sun, so average power output is way below peak. You don't get 1.3kW per square meter for 4 hours a day. 42,339 MW of PV installations produced 39,401 GWh of energy in 2017 in Germany[1], so on average you get peak power for just two hours a day with panels that are angled appropriately. [1] https://en.wikipedia.org/wiki/Solar_power_in_Germany#Statistics https://en.wikipedia.org/wiki/Solar_power_in_Germany#Statist...
- Finnucane 7y agoThen you get not all of you charge from the solar panel, but a quarter to a half. So what? That's still good. If the car basically had 20 free miles a day, that would mean much less reliance on plugging in.
- Retra 7y agoYou are probably going to spend more energy than that just lugging around solar panels.
- vinw 7y agoSeems not pessimistic enough to me. Realistically most people would capture on average, while the sun is up, about 100 watts if they covered their car in solar panels. A car needs at least 10 KW to cruise at 60 mph. This means you need to charge for 100 hours for 1 hour of driving. Actually 200 hours because you can't charge at night-time.
- odonnellryan 7y agoI have experience with solar and boats and it is generally the same problem. No, you won't ever be able to power a boat or a car only on solar for long distances, unfortunately. Maybe if you are driving a few miles.