3 ms·

Has no one done the math on this? Isn't it clearly a horrible idea, based on how much energy is available from the sun over a few square meters if car, versus t

Has no one done the math on this? Isn't it clearly a horrible idea, based on how much energy is available from the sun over a few square meters if car, versus the amount of energy cars use? I guess if you live in the desert, and every week you park your car for 6 days and drive 1 day.

cool_dude85 4y ago
It's for sure a Nikola Motors situation.
- darknavi 4y ago
  As long as you're going down hill the range is infinite!
- bigtex 4y ago
  They currently have shipped more semi trucks than Tesla.
  - cool_dude85 4y ago
    I guess the recipients must have been downhill of the factory.
acomjean 4y ago
We have a roof top solar array that does peak 3500 Watts. Its not unsubstantial. But with the electric car (say about 4 miles/kwh) , we estimated about 12 miles of charge per day.
margalabargala 4y ago
Depending on the specific use case, it may not be terrible. I drive a Nissan Leaf. It gets 5.5 mi per kWh in the summer, 4.8 in the winter. My commute is about 7 miles 1-way. So less than 3kWh used daily assuming I just commute. They have a 1kW solar panel on their car. If I had a car with the efficiency of my Leaf that charged from a 1kW panel every day, it's conceivable that for my specific use case I would rarely ever charge. That said I don't think my case is typical and I am not a large enough market segment to cater to. Nor would I ever trade my dirt-cheap Leaf for whatever exorbitant price these things will cost.
- aplummer 4y ago
  Wouldn’t it add weight though? It seems like if the car is parked next to a solar panel and drives away without it then it’s a lot more efficient.
  - zackmorris 4y ago
    Yes but with regenerative breaking, the additional wind resistance is probably a bigger problem above 35 mph. One trick is to swap out the old 12V lead-acid battery they insist on sticking in electric cars with modern LiFePO4 ones to immediately save 20-25 pounds. Aluminum or alloy wheels might save another 50+ pounds if the car doesn't already have them. So it's conceivable to carry one or two 50 pound solar panels for free. An inverter and additional batteries to buffer the charge will add some weight though, since most electric cars have the artificial limitation that they can't charge while driving.
  - dzhiurgis 4y ago
    1kwp of solar cells weighs in the order of 10kgs, double for whole assembly, triple for the inverter.
    - margalabargala 4y ago
      An electric car doesn't need an inverter, it can charge directly off the produced DC. Nor does it particularly need a "whole assembly" for mounting etc, as it would be built directly into the roof of the car. It may well be that using a solar panel to replace the metal skin of the car will turn out to be equal or less weight than it otherwise would be, though of course much more expensive.
  - margalabargala 4y ago
    Not necessarily. I'm not particularly familiar with the weight of the metal skins of cars, but it doesn't seem obvious that a solar panel is heavier than the metal it would be replacing. A typical 1kW panel weighs about 40lbs, of which about 9lbs is the actual silicon producing the energy, and the rest is the protective glass, silicon backing, and structural material around the edges. It seems to me that if the panel is specially made to fit into a car roof as-manufacturered in place of a metal roof, a lot of that wouldn't be needed as it would be built into the roof anyway, and the added panel weight would be pretty negligible. The DC produced by the panel can also be directly used to charge the battery, no need for inverters.
PaulDavisThe1st 4y ago
> I guess if you live in the desert, and every week you park your car for 6 days and drive 1 day. I live in the high (semi) desert in northern New Mexico, and for myself and a lot of my neighbors, that's precisely the situation we're in. Doesn't mean we would drop $255k on a car, however. For that kind of money, I could have a ground mount array plus batteries that could provide enough juice to recharge a conventional EV in a couple of hours.

cool_dude85 4y ago

It's for sure a Nikola Motors situation.

darknavi 4y ago
As long as you're going down hill the range is infinite!
bigtex 4y ago
They currently have shipped more semi trucks than Tesla.
- cool_dude85 4y ago
  I guess the recipients must have been downhill of the factory.

acomjean 4y ago

We have a roof top solar array that does peak 3500 Watts. Its not unsubstantial. But with the electric car (say about 4 miles/kwh) , we estimated about 12 miles of charge per day.

margalabargala 4y ago

Depending on the specific use case, it may not be terrible. I drive a Nissan Leaf. It gets 5.5 mi per kWh in the summer, 4.8 in the winter. My commute is about 7 miles 1-way. So less than 3kWh used daily assuming I just commute. They have a 1kW solar panel on their car. If I had a car with the efficiency of my Leaf that charged from a 1kW panel every day, it's conceivable that for my specific use case I would rarely ever charge. That said I don't think my case is typical and I am not a large enough market segment to cater to. Nor would I ever trade my dirt-cheap Leaf for whatever exorbitant price these things will cost.

aplummer 4y ago
Wouldn’t it add weight though? It seems like if the car is parked next to a solar panel and drives away without it then it’s a lot more efficient.
- zackmorris 4y ago
  Yes but with regenerative breaking, the additional wind resistance is probably a bigger problem above 35 mph. One trick is to swap out the old 12V lead-acid battery they insist on sticking in electric cars with modern LiFePO4 ones to immediately save 20-25 pounds. Aluminum or alloy wheels might save another 50+ pounds if the car doesn't already have them. So it's conceivable to carry one or two 50 pound solar panels for free. An inverter and additional batteries to buffer the charge will add some weight though, since most electric cars have the artificial limitation that they can't charge while driving.
- dzhiurgis 4y ago
  1kwp of solar cells weighs in the order of 10kgs, double for whole assembly, triple for the inverter.
  - margalabargala 4y ago
    An electric car doesn't need an inverter, it can charge directly off the produced DC. Nor does it particularly need a "whole assembly" for mounting etc, as it would be built directly into the roof of the car. It may well be that using a solar panel to replace the metal skin of the car will turn out to be equal or less weight than it otherwise would be, though of course much more expensive.
- margalabargala 4y ago
  Not necessarily. I'm not particularly familiar with the weight of the metal skins of cars, but it doesn't seem obvious that a solar panel is heavier than the metal it would be replacing. A typical 1kW panel weighs about 40lbs, of which about 9lbs is the actual silicon producing the energy, and the rest is the protective glass, silicon backing, and structural material around the edges. It seems to me that if the panel is specially made to fit into a car roof as-manufacturered in place of a metal roof, a lot of that wouldn't be needed as it would be built into the roof anyway, and the added panel weight would be pretty negligible. The DC produced by the panel can also be directly used to charge the battery, no need for inverters.

PaulDavisThe1st 4y ago

> I guess if you live in the desert, and every week you park your car for 6 days and drive 1 day. I live in the high (semi) desert in northern New Mexico, and for myself and a lot of my neighbors, that's precisely the situation we're in. Doesn't mean we would drop $255k on a car, however. For that kind of money, I could have a ground mount array plus batteries that could provide enough juice to recharge a conventional EV in a couple of hours.