Solar power roof

[MOE J]

Teslas have black glass roofs, why can’t they implement solar panels to charge the battery while the car sits in the sun all day ?. Even 5 % would be possible ?. Seems like a no brainer.

 

[Sophias_dad]

I don't know what the point is being made from the example of Lightyear Zero when there's a realistic example on the market today, which is the solar roof on the Prius Prime.

It costs $610 for a 185W panel, which is ~$3.30/W and roughly the same pricing as residential rooftop PV in the US. Yes that price is more expensive than utility solar, but the economics are clearly proven here. Nobody is forcing you to put solar panels on your car (yet), but trying to kill the idea by saying it's unrealistic and never be worth it are just as far off base.

I think the main disconnect here is the camp that says "solar panels on a car roof will make it so the car never needs to plug in" and the camp that says "solar panels can help slightly"

I like math, as those who have read this thread can attest. So lets do some math on that 185W panel, and put it in Arizona where the owner parks in the sun all the time. That's 185*7 hours of full sun or 1295 wh/day. Now lets see how much that would cost if you bought it at AZ electricity rates... 0.14/kwh times 1.295 is $0.182595. $610 divided by $0.182595 is 3340 days. That's nine years for payback in the sunniest place I can think of. Yes, payback isn't everything, and I myself would buy the solar panel roof just for the novelty, because that's basically what it is IMHO

Redoing that math for Massachusetts with five hours(optimistic) of full sun per day on average, I get 2355 days, or 6.45 years for payback. This result surprised me, but its because Massachusetts electricity prices are DOUBLE those of Arizona, ironically because of renewable energy. Do the math in North Dakota and you'll get more like 19 years of payback, which is most likely longer than the life of the car.

From an investing standpoint, that $610 is indeed better on the roof of the Prius than in a high yield savings account. OTOH, your $610 in the HYSA doesn't cost $1000 or more to replace when it breaks, doesn't cost anything to insure, and doesn't require you to find the sunniest spot in the parking lot, and you don't have to drag the extra weight around where ever you go.

I didn't do the math myself, but apparently an average 5kw array in AZ costs around $8k installed, after credits, or $1.6/w. The $610 185W panel on the Prius roof is $3.3/w. That's not 'nearly the same' in my book, that's DOUBLE. It can also be properly inclined toward the sun, be placed somewhere there are no trees, and so on.

 

[MOE J]

Did you not see that the absolute maximum energy available in sunlight is around 1120 watts per square meter? One handy laptop is about 1 square foot, or 1/10th of a square meter(closer to 1/11th, but I'll be optimistic. This means that if you have absolutely perfect solar panels that absorb every bit of light(including infrared) for that laptop sized square, you will get 112w continuous. Lets put that at the equator, in full sun for 12 hours a day because 'night' is a thing even at the equator. That's 112x12h, or 1.344kwh PER DAY. Keep in mind, there is no 'miracle' that might happen in the future that will make that laptop sized panel put out more power. That's the physics of it, full stop. Your laptop sized panel, if its PERFECT, will provide enough power to run the computers ASLEEP in a model 3 for the day, PLUS two miles of range. Sure, you could say 'but the lightyear 0' yadda yadda.... okay, lets ignore the power to keep the computer running, and its 169wh/mile for the LY0 and never use ANY HVAC for the sunniest place on the planet... That'll get you EIGHT whole miles per day, with a completely unrealistic scenario.

I agree it'd be great if solar panels were able to put out more power than is landing on them, but its not possible now and never will be.

Nope new cutting edge tech coming will be a game changer in solar and everyone will want one.

 

[ucmndd]

Nope new cutting edge tech coming will be a game changer in solar and everyone will want one.

How fun it must be to live in your world where the laws of physics don’t matter.

 

[Rocky_H]

Nope new cutting edge tech coming will be a game changer in solar and everyone will want one.

I think you missed the part where this was already assuming all future cutting edge tech had already been invented and deployed by showing the math for a perfect 100% yield panel. It can't improve from there.

 

[ucmndd]

Now lets see how much that would cost if you bought it at AZ electricity rates... 0.14/kwh times 1.295 is $0.182595. $610 divided by $0.182595 is 3340 days. That's nine years for payback in the sunniest place I can think of.

Let’s also consider that you’ll blow through a significant fraction of that fancy new energy you collected just to cool the car off from baking in the sun for 10 hours vs the shade

 

[DuncanM]

I think you missed the part where this was already assuming all future cutting edge tech had already been invented and deployed by showing the math for a perfect 100% yield panel. It can't improve from there.

See post 78.

 

[ucmndd]

See post 78.

What does post 78 have to do with the claim that "cutting edge tech" is going to create energy from nothing?

 

[DuncanM]

What does post 78 have to do with the claim that "cutting edge tech" is going to create energy from nothing?

Post 78 shows that non-cutting edge tech creates lots of energy from car mounted PV panels.

 

[MLXXXp]

So lets do some math on that 185W panel, and put it in Arizona where the owner parks in the sun all the time. That's 185*7 hours of full sun or 1295 wh/day.

Your math doesn't take into account that "full sun" means the panel is pointed directly at the Sun, which it won't be for most of the time during those 7 hours, for a parked car. Realistically, I'd reduce the amount of energy produced per day to 50% of what you've calculated, or less.

 

[MOE J]

The tech had not been released yet, billions to be made.

 

[ucmndd]

The tech had not been released yet, billions to be made.

You heard it here first y’all.

Just waiting on the tech that harvests more solar energy than the sun actually produces. First person who figures out how to make energy from nothing will make billions!

 

[yesimon]

I know you are joking but space-based solar power (SBSP) may actually become a viable business in the future. Just think about how Starlink exists when it's "so much inferior" and more expensive than fiber internet.

 

[Sophias_dad]

Your math doesn't take into account that "full sun" means the panel is pointed directly at the Sun, which it won't be for most of the time during those 7 hours, for a parked car. Realistically, I'd reduce the amount of energy produced per day to 50% of what you've calculated, or less.

I'd certainly agree. I was specifically going for best (ideal, unrealistic) case and the math still doesn't work well at all.

 

[Sophias_dad]

I know you are joking but space-based solar power (SBSP) may actually become a viable business in the future. Just think about how Starlink exists when it's "so much inferior" and more expensive than fiber internet.

I saw that on a youtube video a week ago, I think. SBSP does indeed have a better chance of being a 'thing' than a laptop sized solar panel powering a car.

Starlink is filling two or more very significant niches, where terrestrial fiber/cable just doesn't go and the mobile market(RV's, airplanes, ships). I'm no pro in that space, but I'd wager 90+ percent of Starlink's business is to areas where people have no other choice.

 

[MOE J]

Someone actually selling this today.

 

[MOE J]

Someone actually selling this today.

And that’s just today…..watch how the solar energy explodes 5 years from right now.

 

[MOE J]

You heard it here first y’all.

Just waiting on the tech that harvests more solar energy than the sun actually produces. First person who figures out how to make energy from nothing will make billions!

 

[MOE J]

Sold out -I’d place an order if I were u

 

[Sophias_dad]

Sold out -I’d place an order if I were u

I would, but I'm not a sucker. Even their own documents suggest they are stretching the truth. 1200W is essentially a 10A 120V circuit's worth of power. You can try it yourself with a UMC plugged into a wall outlet. If you get more than 3mi/hr reported, I'll be surprised. 3mi/hr times 7 hours is 21 miles/day, well short of 30mi/day. Even if the car is rounding down to report 3.4999 as 3 mi/hr, you get to almost 25 miles per hour.

That 1200W they are quoting is probably also a bit 'optimistic' at best. From https://gosun.co/pages/ev-solar-charger , we see the solar part of the panels is 43" wide, and the overall extended length is 245". Rounding the 245 down to say 235 for hinges and such, we get to 10,105 sq inches of actual cells. Divide that by 144 to get square feet and we are at 70. Multiply that by the 112W for a square foot of cells, and its 7840w. Full sun, properly inclined to catch it all. To get near 1200, they'll need to get more than 50% more output than that amount of solar cells can do. Sure, maybe they have 10% more effective cell coverage, and they are 10% more efficient, but there's no way whatsoever that that amount of cells is gonna put out 1200W continuous in full sun.

I wonder how much mileage is lost by having a roof rack storing all those cells in place all the time.

I mean its a fine idea for camping or other off-grid stuff but as a daily item, not so much.

 

[DuncanM]

I would, but I'm not a sucker. Even their own documents suggest they are stretching the truth. 1200W is essentially a 10A 120V circuit's worth of power. You can try it yourself with a UMC plugged into a wall outlet. If you get more than 3mi/hr reported, I'll be surprised. 3mi/hr times 7 hours is 21 miles/day, well short of 30mi/day. Even if the car is rounding down to report 3.4999 as 3 mi/hr, you get to almost 25 miles per hour.

That 1200W they are quoting is probably also a bit 'optimistic' at best. From https://gosun.co/pages/ev-solar-charger , we see the solar part of the panels is 43" wide, and the overall extended length is 245". Rounding the 245 down to say 235 for hinges and such, we get to 10,105 sq inches of actual cells. Divide that by 144 to get square feet and we are at 70. Multiply that by the 112W for a square foot of cells, and its 7840w. Full sun, properly inclined to catch it all. To get near 1200, they'll need to get more than 50% more output than that amount of solar cells can do. Sure, maybe they have 10% more effective cell coverage, and they are 10% more efficient, but there's no way whatsoever that that amount of cells is gonna put out 1200W continuous in full sun.

I wonder how much mileage is lost by having a roof rack storing all those cells in place all the time.

I mean its a fine idea for camping or other off-grid stuff but as a daily item, not so much.

I charge my car at 110v/10a and I get (according to the car, about 1.7% SOC/hr) or about 4mile/hr of range.