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Toyota testing improved solar roof for EVs that can charge while driving

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Re: Toyota testing improved solar roof for EVs that can charge while driving

#21

Post by bochoh »

SketchySeaBeast wrote: post #8
bochoh wrote: post #7

Earlier quoted context omitted.

I think that would wholely depend on the setup for the AC compressor. If it's entirely electric and sized appropriately it can be a fairly efficient mechanism. A friend of mine uses the AC in their tesla to keep pastries cold from lunch to evening commute for < 10-20 miles of range depending on ambient temperatures. Meanwhile my gas SUV idles at .3 - .5 gallons per hour depending on engine load. (4 cylinder 2.0 liter…

They use their Tesla like a fridge for only 10-20 miles reduction????? That's amazing both in it's apparent wastefulness and efficiency. If that's the same scale, solar charging could easily keep your AC and stereo on while you wait.

I believe they just set the cooling to around 64F to keep pastries from melting etc. First world problems for sure.

Re: Toyota testing improved solar roof for EVs that can charge while driving

#22

Post by zwily »

temporaryvector wrote: post #12

I live in a pretty hot city (My car's outside thermometer showed 48°C yesterday at midday). The extended range is nice and all, but if somebody makes a car that can run the AC without running/draining the battery while it's parked, even if it's just a little to keep the car interior at 35°C or so, I would, without exaggeration, buy it the day it's released here. Hell, I'd consider it even if it would just keep the fa…

I keep the AC on in my Tesla a lot during the summer. Costs a couple miles per hour of range. Totally worth it.

Re: Toyota testing improved solar roof for EVs that can charge while driving

#23

Post by kevin_b_er »

They covered the car, including the back window, in triple-junction solar cells. Last I heard, those were made of expensive stuff like indium gallium arsenide junctions. They were popular on satellites because they do really really well outside of atmosphere and much worse in shaded and indirect light conditions than silicon.

I'd like to know how much those cells really cost and how much power is left when you can see out the back window again. 860W sounds like a high number. Fancy 30+% triple junction solar cells cost something like $200-$300 per _watt_ years ago. As a result, those solar panels might be worth more than the car itself! Even if they've got the fancy ones down to $50/watt, that's still $43000 in solar cells. Sure they've got grandiose claims about how little they'll cost in the future, but I'd like to know about today.

This is same bunk as hearing they've made a new crazy high efficiency solar cell, but it can't be manufactured outside a lab with a mountain of grad students doing the work. Sounds cool, but it won't come to market any time soon.

Re: Toyota testing improved solar roof for EVs that can charge while driving

#24

Post by icebraining »

devoply wrote: post #16
temporaryvector wrote: post #12

I live in a pretty hot city (My car's outside thermometer showed 48°C yesterday at midday). The extended range is nice and all, but if somebody makes a car that can run the AC without running/draining the battery while it's parked, even if it's just a little to keep the car interior at 35°C or so, I would, without exaggeration, buy it the day it's released here. Hell, I'd consider it even if it would just keep the fa…

It would also be cool, pun intended, to add windows with liquid crystals that can darken when parked to keep additional heat out.

Smart film/tint/glass on a car window: https://www.youtube.com/watch?v=c7xEcI1oSVs

Re: Toyota testing improved solar roof for EVs that can charge while driving

#25

Post by ilyaeck »

temporaryvector wrote: post #12

I live in a pretty hot city (My car's outside thermometer showed 48°C yesterday at midday). The extended range is nice and all, but if somebody makes a car that can run the AC without running/draining the battery while it's parked, even if it's just a little to keep the car interior at 35°C or so, I would, without exaggeration, buy it the day it's released here. Hell, I'd consider it even if it would just keep the fa…

In theory, the solar roof should absorb ~30% of the rays a cars is exposed to, so it won't heat up as much. Not sure if the effect would be significant, though.

Re: Toyota testing improved solar roof for EVs that can charge while driving

#26

Post by temporaryvector »

agumonkey wrote: post #13
temporaryvector wrote: post #12

I live in a pretty hot city (My car's outside thermometer showed 48°C yesterday at midday). The extended range is nice and all, but if somebody makes a car that can run the AC without running/draining the battery while it's parked, even if it's just a little to keep the car interior at 35°C or so, I would, without exaggeration, buy it the day it's released here. Hell, I'd consider it even if it would just keep the fa…

how much power does an AC use (say on medium settings) ?

I'm actually not sure in terms of car AC. Local wisdom says that on hot days your AC will sap up to 10 HP from your engine. Not sure how accurate that is.

Looking around on Telsa forums and the like, I'm seeing numbers between 1 and 3 kW. My house's mini split AC unit draws around 9 amps (according to documentation, anyway), so around 2 kW. Actual numbers seem to be closer to 3 kW in the summer.

Re: Toyota testing improved solar roof for EVs that can charge while driving

#27

Post by SigmundA »

agumonkey wrote: post #13
temporaryvector wrote: post #12

I live in a pretty hot city (My car's outside thermometer showed 48°C yesterday at midday). The extended range is nice and all, but if somebody makes a car that can run the AC without running/draining the battery while it's parked, even if it's just a little to keep the car interior at 35°C or so, I would, without exaggeration, buy it the day it's released here. Hell, I'd consider it even if it would just keep the fa…

how much power does an AC use (say on medium settings) ?

Not sure on medium but I think ev A/C like Tesla's are 15,000 btu units. A 15k btu a/c should be between 1000-1600 watts depending on efficiency.

Re: Toyota testing improved solar roof for EVs that can charge while driving

#28

Post by walrus01 »

SigmundA wrote: post #19
realityman wrote: post #14

Does the math check out? You would need about 10kW-h to get the claimed distance, times three for the efficiency (by the way, there are NO mass-produced cells with 34% efficiency; they must be using GaAs or multijunction cells to achieve 34%) means solar input of 30kW-h per day. The projected horizontal area of a Prius is 8m^2 (including the windows) so we need about 4 hours of 1000W/m^2 insolation. Which I guess isn…

Yes looks like GaAs: https://global.toyota/en/newsroom/corporate/28787347.html

If they can bring the cost down on that, for other types of panel manufacturing for non automotive markets, that would be pretty amazing. 22% monocrystalline silicon 156mm cells are a commodity now (such as to build a 60 or 72 cells panel with and sell it under $0.60/watt), but 30 to 34% GaAs cells are incredibly expensive.

Until very recently GaAs triple junction cells have been so costly they are only used on satellites and other spacecraft.

Re: Toyota testing improved solar roof for EVs that can charge while driving

#29

Post by hwillis »

temporaryvector wrote: post #12

I live in a pretty hot city (My car's outside thermometer showed 48°C yesterday at midday). The extended range is nice and all, but if somebody makes a car that can run the AC without running/draining the battery while it's parked, even if it's just a little to keep the car interior at 35°C or so, I would, without exaggeration, buy it the day it's released here. Hell, I'd consider it even if it would just keep the fa…

> The extended range is nice and all, but if somebody makes a car that can run the AC without running/draining the battery while it's parked, even if it's just a little to keep the car interior at 35°C or so, I would, without exaggeration, buy it the day it's released here.

Tesla's dog mode does this. Draining the battery isn't really something to worry about; AC uses <300 watts over long periods (turns on and off at <1 kW). Leaving it on for 8+ hours you're talking about <5% capacity loss, at a cost of <50 cents. For short trips you could leave the AC on full blast without even noticing a drop.

Re: Toyota testing improved solar roof for EVs that can charge while driving

#30

Post by singularity2001 »

SigmundA wrote: post #17

Triple junction GaAs based panels for a whole 860 watts of power in full sun at the right angle, no mention of cost. Anybody know how much a panel like that goes for per watt now days?

Doesn't answer your question but I just saw that you can get ordinary 100W panels for 65€ on eBay now (in pack of 2)!
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