4 ms·

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.

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.