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>The Tesla Model 3 a fairly small car and even that’s 4.7 m X 2.09m. Uh huh. Do you want to put some numbers behind your assumptions. How much do you actually

>The Tesla Model 3 a fairly small car and even that’s 4.7 m X 2.09m. Uh huh. Do you want to put some numbers behind your assumptions. How much do you actually think you can generate that would make a difference to a Tesla 60kWh-100kWh battery? How much extra range do you think solar panels would provide? And finally, what aren't EV manufacturers seeing that you are seeing? It's not like solar panels on an EV are such a novel idea. In fact, it's the very first (naive) idea that everyone has as a potential solution to EV range and charging.

Retric 4y ago
Currently there are 200W systems on real world cars that don’t cover that much of the car, but Toyota just made a Prius demo without changing the underlying design or using panels on the sides or dashboard which they say adds 25miles of range per day. https://global.toyota/en/newsroom/corporate/28787347.html https://global.toyota/en/newsroom/corporate/28787347.html So, assuming 4miles per kWh that Prius was expected to hit over 6kWh per day. That might not look like much vs a 100kWh battery pack but it’s 9,000 miles per year when the majority of Americans are only driving 13,000 or less. Their design doesn’t look practical, but 5kW/day in sunny areas seem to be a reasonable real world goal.
- mikem170 4y ago
  > So, assuming 4miles per kWh that Prius was expected to hit over 6kWh per day. That might not look like much vs a 100kWh battery pack but it’s 9,000 miles per year when the majority of Americans are only driving 13,000 or less. I checked your link after reading your math, above. Coming from the RV solar world I found these numbers surprising. I think your comment about the 100 kWh battery pack is what threw me off. The normal battery in a Prius is 8.8 kWh with a 25 mile all-electric range [0]. Toyota is saying that the panels they used generate approximately 860 watts of power. The normal rule of thumb in the RV world (which I am familiar with) is to multiply panel wattage by 5 for watt-hours per day in good sun, so I would assume 5 kWh total per day for 860 watts of panels, in real life. So their numbers look optimistic to me, but aren't crazy - I would have said 15 miles under ideal conditions (5 kWh of their 8.8 kWh 25 mile battery), they said 44.5 km. They used 34% efficient panels to get that many watts from the limited space available on a car, something normally only available to the likes of NASA at this time (normal panels are around 20%). Only people in places like Arizona and Texas would get most of that power output, others not so much. I don't think people realize how much impact clouds, shade and optimal panel angle towards the sun have on solar power output. Even partial shade, like form a sign post, greatly diminishes power generation, unless you want to wire the panels differently and loose early/late/cloudy power capacity. For example, in 2021 Germany had 58728 MW of solar panels generating 49011 GW of power per year [1], which is 134.2 GW per day, which is only 2.3 times their panel capacity, and this is due to clouds. Based on this math that solar prius car in Germany may only get 5.6 miles per day of extra solar powered range with 860 watts of panels (860 watts times 2.3 is 2 kWh, or 22.5% of a 8.8 kWh 25 mile battery), or about 2050 miles per year, and perhaps a good bit less because the car panels are not oriented towards the sun like fixed panel installations usually are, and people park in shade under trees, or partial shade near telephone poles, or next to buildings sometimes, or winter when it's below freezing and cloudy the battery needs to warm itself to safely be charged, etc. The only other thing I would add to this discussion is that panels fixed to the surface of a car may have problems with heat. Normal rigid solar panels are in frames and elevated, allowing air to flow under the panels and cool them. Panels loose efficiency with heat. Flexible solar panels, which don't need a frame and can be attached to curved surfaces, typically fail in a year or three, they are nowhere near as reliable as rigid panels. There's a lot of discussion about this in the RV and boating communities. If the numbers work out on this idea, then that's great. Reliability would be my biggest concern, these panels need to last to pay for themselves. [0] https://getjerry.com/car-repair/toyota-prius-plug-in-hybrid-battery-size https://getjerry.com/car-repair/toyota-prius-plug-in-hybrid-... [1] https://en.wikipedia.org/wiki/Solar_power_in_Germany#Generation https://en.wikipedia.org/wiki/Solar_power_in_Germany#Generat...
- macspoofing 4y ago
  >but Toyota just made a Prius demo You mean in 2019. >or dashboard which they say adds 25miles of range per day. They made a prototype. They didn't say how much extra cost it would add to the car (and how it affects reliability, maintenance and safety). The cost of those panels has to be balanced by the fact that 25 miles is 30-60 min charge from your mains vs a day of charging from solar? They also made a point to state this wasn't for range extension - i.e. when you're driving, that solar panel isn't contributing meaningfully to your range. >Their design doesn’t look practical, but 5kW/day in sunny areas seem to be a reasonable real world goal. You and I have different definition of 'reasonable'. Like I said, there's a cost to putting these panels on the car and the benefit is so effin small (even sunny areas have cloudy days and/or your car is frequently parked in the shade or indoors) that it's much more reasonable just to plug the darn thing into your mains and charge that way.

Retric 4y ago

Currently there are 200W systems on real world cars that don’t cover that much of the car, but Toyota just made a Prius demo without changing the underlying design or using panels on the sides or dashboard which they say adds 25miles of range per day. https://global.toyota/en/newsroom/corporate/28787347.html https://global.toyota/en/newsroom/corporate/28787347.html So, assuming 4miles per kWh that Prius was expected to hit over 6kWh per day. That might not look like much vs a 100kWh battery pack but it’s 9,000 miles per year when the majority of Americans are only driving 13,000 or less. Their design doesn’t look practical, but 5kW/day in sunny areas seem to be a reasonable real world goal.

mikem170 4y ago
> So, assuming 4miles per kWh that Prius was expected to hit over 6kWh per day. That might not look like much vs a 100kWh battery pack but it’s 9,000 miles per year when the majority of Americans are only driving 13,000 or less. I checked your link after reading your math, above. Coming from the RV solar world I found these numbers surprising. I think your comment about the 100 kWh battery pack is what threw me off. The normal battery in a Prius is 8.8 kWh with a 25 mile all-electric range [0]. Toyota is saying that the panels they used generate approximately 860 watts of power. The normal rule of thumb in the RV world (which I am familiar with) is to multiply panel wattage by 5 for watt-hours per day in good sun, so I would assume 5 kWh total per day for 860 watts of panels, in real life. So their numbers look optimistic to me, but aren't crazy - I would have said 15 miles under ideal conditions (5 kWh of their 8.8 kWh 25 mile battery), they said 44.5 km. They used 34% efficient panels to get that many watts from the limited space available on a car, something normally only available to the likes of NASA at this time (normal panels are around 20%). Only people in places like Arizona and Texas would get most of that power output, others not so much. I don't think people realize how much impact clouds, shade and optimal panel angle towards the sun have on solar power output. Even partial shade, like form a sign post, greatly diminishes power generation, unless you want to wire the panels differently and loose early/late/cloudy power capacity. For example, in 2021 Germany had 58728 MW of solar panels generating 49011 GW of power per year [1], which is 134.2 GW per day, which is only 2.3 times their panel capacity, and this is due to clouds. Based on this math that solar prius car in Germany may only get 5.6 miles per day of extra solar powered range with 860 watts of panels (860 watts times 2.3 is 2 kWh, or 22.5% of a 8.8 kWh 25 mile battery), or about 2050 miles per year, and perhaps a good bit less because the car panels are not oriented towards the sun like fixed panel installations usually are, and people park in shade under trees, or partial shade near telephone poles, or next to buildings sometimes, or winter when it's below freezing and cloudy the battery needs to warm itself to safely be charged, etc. The only other thing I would add to this discussion is that panels fixed to the surface of a car may have problems with heat. Normal rigid solar panels are in frames and elevated, allowing air to flow under the panels and cool them. Panels loose efficiency with heat. Flexible solar panels, which don't need a frame and can be attached to curved surfaces, typically fail in a year or three, they are nowhere near as reliable as rigid panels. There's a lot of discussion about this in the RV and boating communities. If the numbers work out on this idea, then that's great. Reliability would be my biggest concern, these panels need to last to pay for themselves. [0] https://getjerry.com/car-repair/toyota-prius-plug-in-hybrid-battery-size https://getjerry.com/car-repair/toyota-prius-plug-in-hybrid-... [1] https://en.wikipedia.org/wiki/Solar_power_in_Germany#Generation https://en.wikipedia.org/wiki/Solar_power_in_Germany#Generat...
macspoofing 4y ago
>but Toyota just made a Prius demo You mean in 2019. >or dashboard which they say adds 25miles of range per day. They made a prototype. They didn't say how much extra cost it would add to the car (and how it affects reliability, maintenance and safety). The cost of those panels has to be balanced by the fact that 25 miles is 30-60 min charge from your mains vs a day of charging from solar? They also made a point to state this wasn't for range extension - i.e. when you're driving, that solar panel isn't contributing meaningfully to your range. >Their design doesn’t look practical, but 5kW/day in sunny areas seem to be a reasonable real world goal. You and I have different definition of 'reasonable'. Like I said, there's a cost to putting these panels on the car and the benefit is so effin small (even sunny areas have cloudy days and/or your car is frequently parked in the shade or indoors) that it's much more reasonable just to plug the darn thing into your mains and charge that way.