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

https://techcrunch.com/2019/07/05/toyota-testing-improved-solar-roof-for-electric-cars-that-can-charge-while-driving/

by JaakkoP • 7 years ago

158 157 7 years ago

If you run the math on this, even assuming 100% efficient conversion to electricity, it doesn't seem very useful.

bochoh3• 7 years ago

>The new system will provide up to 44.5 km (27.7 miles) of additional range per day while parked and soaking up sun, and can add up to 56.3 km (35 miles) of power to both the driving system and the auxiliary power battery on board, which runs the AC, navigation and more.

As someone with nearly 100 miles of round trip commute (and who parks in a usually very sunny parking lot) I would certainly appreciate 27+ miles of "free" range. Certainly enough to be useful for me. In the case of a Tesla I'm sure it's more than enough to negate the continuous usage of sentry mode as well.

SketchySeaBeast3• 7 years ago

I wonder if it'll provide enough power so that you can park and wait with AC or the stereo (admittedly two very different loads) running without worrying about it cutting into your range.

hn_throwaway_99• 7 years ago

The new system will provide up to 44.5 km (27.7 miles) of additional range per day while parked and soaking up sun

That seems like a big deal. Most drivers actually drive in the 30-50 mile range per day (IIRC Chevy said that over 80% of commuters would be able to only be on electric with their 53-electric-mile-range Volt). So for most drivers this amount of power could reduce their external electricity needs by somewhere between 50-100%.

lettergram• 7 years ago

They are claiming up to 27.7mi per day left in the sun. If true, my 5mi commute each way would be possible without ever charging the vehicle in the summer...

That being s said, curious how this holds up to weather (hail, snow, etc) and whether those numbers are accurate.

agumonkey5• 7 years ago

I think it will make a lot of sense for light vans. A lot more surface.

penagwin2• 7 years ago

Given the small surface area of the roofs, the efficiency of existing solar panels, and how much car companies exaggerate when it comes to miles (do they mean 27.7mi with all the seats removed, etc.) I would expect it to be a practical no-go for anything except sunshine.

I'm from michigan, so in the winter assuming you park your car in the open for your job, you can easily expect it to be covered in snow - whenever it snows - which is all winter.

So it'd only be beneficial here during the summer, except when it's raining which is currently 3/7 days of the week.

I mean it'd be a nice bonus I guess, but at least for my situation it wouldn't make a ton of sense to spend extra on.

adrianmonk• 7 years ago

It would be very climate dependent.

Here in Texas, typically I'd have 0 to 5 days per year with snow on my car. And nobody drives on those days anyway.

And there are 228 sunny days in an average year.

I would be worried about hail, though. I know a lot of people whose cars have been damaged or even totalled by hail.

Johnny5556• 7 years ago

If true, my 5mi commute each way would be possible without ever charging the vehicle in the summer

If you're interested in reducing environmental impact, a bicycle would also let you do that commute without charging and with much less environmental impact than an EV covered in solar cells... though it may be less pleasant in hail and/or snow.

If you're just interested in saving money for electricity, then I'd be surprised if the extra cost in adding all of those solar cells is cheaper than paying for the electricity.

chris11• 7 years ago

The one exception is parking. This isn't as useful if you use covered parking. And with a new car I'd rather use covered parking.

jillesvangurp• 7 years ago

It's probably going to fluctuate quite a bit. But for a lot of people on average they'd find their car charged of nearly charged when it's been sitting out there for hours/days. The exception would be longer trips, which most people don't do every day.

driverdan• 7 years ago

This is like any other concept car. It's a cool concept but won't make it to production.

The commercial viability of this is far off. 34% solar is prohibitively expensive. You won't see these on cars until costs come down significantly.

realityman3• 7 years ago

Covering an entire Prius with exotic semiconductors is not the road to brisk sales.

Theodores• 7 years ago

I thought the same about defect free LCD panels. Now they are cheap enough to make a house out of them and they have replaced billboards that used to be made from paper.

One thing that has changed is the structural value of the roof of a car. In the olden days the roof was a vital part of the safety cell. Now it is not quite the same. The A-pillar has been toughened up and the engineering for the roof is different, hence the all-glass affair on the Tesla Model 3 and other marques.

Elon Musk said there was no point in having solar panels on the car and that those would be best kept roadside for generating power that goes into the grid.

He was right.

But you are not going to persuade your supermarket to cover their entire parking lot with solar cells so your car can park in the cool shade underneath them whilst getting free power.

If solar cells can be as good as printed and be an integral plart of a car in the place of steel, paint, glass or carbon-fibre then they don't have to make commercial sense in the rational way that Elon Musk outlines. When I get my EV campervan in 2025 I hope the roof is festooned with solar panels that are not some bolt on but integrated into the design. If I am parked up somewhere and they give me enough power to make myself a cup of tea and power my laptop then I would be happy with that. If they were a $5K option then they would also be a $3K add-on to the resale value of the campervan. If I kept the van for ten years then $200 a year for that month of use I get out of the van might be more expensive than supercharging the EV for pennies but I would still just like having such a space age feature.

Nothing really makes sense with autos. There isn't such a thing as a stripped down utilitarian auto. It is all a matter of degree. Some people pay for carbon-fibre cup holders. Or fake carbon fibre hood scoops. Or extra titanium bits for the exhaust. Or, perhaps more relevant, a cabriolet top that retracts at the touch of a button at speeds up to 25 mph. If that makes sense to people - and it does - then solar cells on the bonnet and roof can easily be foisted onto the marketplace.

hourislate• 7 years ago

I wonder if there is a market for a car cover that acts like a flexible solar blanket. Here in Texas it could offer your vehicle some protection from the Sun while charging it at the same time.

cagenut• 7 years ago

it'd be a great way to donate solar panels to local teens

temporaryvector6• 7 years ago

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 fans on to vent the hot air out.

Parking in the sun while doing errands, which often involve multiple short trips where the car's AC doesn't get enough time to cool it down, seems to be a very common cause of heat-stroke among white-collar workers here. I've had to go to the ER twice about it this summer alone.

agumonkey5• 7 years ago

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

temporaryvector6• 7 years ago

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.

SigmundA3• 7 years ago

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.

redwall_hp• 7 years ago

Wikipedia says 3kW https://en.wikipedia.org/wiki/Automobile_air_conditioning#Po...

It also says that the most efficient photovoltaics yield 175W per square meter. (Though I've seen figures as high as 200W.) https://en.wikipedia.org/wiki/Solar_panel#Efficiencies

cj• 7 years ago

This probably isn't the most reliable source, but the infotainment screen on my VW estimates the hourly gas consumption for the climate system.

Running on Max A/C, the screen reads just under 1/8 gal/hr. With the A/C on and with the fans at 50%, consumption is a little less but still around 1/8 gal/hr. Consumption drops too low to get a reading when A/C is off with fans 50%.

hwillis6• 7 years ago

Window units range from 700 W to 2+ kW. The Model 3 has a pretty powerful one, at least 1 kW. That's peak draw, and it'll turn on and off intermittently[1]. Average draw should work out to 200-300 watts for medium.

[1]: Like a fridge. Refrigeration systems are most efficient at full power. IIRC it's due to the restrictor plate separating the hot and cold radiators- it's designed to work at a certain rate of flow, so you'll get gas and liquid mixing at lower power.

devoply2• 7 years ago

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

icebraining• 7 years ago

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

DonHopkins• 7 years ago

Wouldn't darkening just absorb more heat? How about turning white, or a reflective coating? (Maybe not something liquid crystals could do, but a car with mirror shades would look cool.)

hwillis6• 7 years ago

I've wanted this for a while, in combo with a head-tracking cabin camera. That way the windscreen would tint in specific areas over the sun, oncoming headlights, and glare.

You can't use LCs, as they don't have a real "clear" mode- they always block a very significant amount of light. You'd have to use electrochromatic paint or similar, as some trains and airplanes do. It's expensive and a chipped windscreen would be awful. You also can't get great resolution. I still wish somebody would do it.

ummonk3• 7 years ago

Yeah I'd want that in a normal ICE car.

helloguillecl2• 7 years ago

Why would you want this feature knowing that is burning gas that you paid for while idle? Would you be happy about the car releasing toxic gases like CO and NOX while parked?

zwily• 7 years ago

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

ilyaeck• 7 years ago

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.

dreamcompiler• 7 years ago

It would help but the glass windows (greenhouse effect) are probably a bigger factor.

robotresearcher2• 7 years ago

How does that compare the the fraction reflected by a white paint scheme?

hwillis6• 7 years ago

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.

temporaryvector6• 7 years ago

I'm not sure how true that would be in extremely hot weather, but it is probably the only reason I'm considering a Tesla if it ever comes to my city, my commute is really short so even if it cut 200 miles off the range it'd be worth it for me.

Having a car with remote start alleviates the problem a little bit, but I'd rather not run an ICE engine while I'm not in the car for obvious reasons.

p1mrx2• 7 years ago

It looks like the Hyundai Kona EV has a Utility Mode that works similarly (the headlights are off, the vehicle is locked in park, and you can run the AC indefinitely.)

However, based on this thread, utility mode requires the key fob, so someone could just break a window and steal the car. I wish manufacturers other than Tesla would think about these use cases:

https://www.insideevsforum.com/community/index.php?threads/u...

cortesoft2• 7 years ago

You can also just turn on the AC from your phone 10 minutes before you leave. Or, have it learn your schedule so it prepares your car for you before you go.

todd8• 7 years ago

This definitely makes Teslas more attractive to me. About half the homes on my (short) street have Teslas. I didn't know how little hot weather affected the battery usage. I had mistakenly assumed that A/C would have a greater negative impact on range.

steelframe• 7 years ago

Tesla's dog mode does this.

Dog mode is the main thing keeping me from trading in my Tesla for something else.

adrianN• 7 years ago

It helps that a Tesla battery can basically power a house for several days.

m4632• 7 years ago

Tesla also has the milder "Cabin Overheat Protection" that can be turned on in settigns to keep the car interior from going over about 100 degrees fahrenheit.

matt-attack• 7 years ago

I would ... buy it the day it’s released

Sounds like this “dog mode” does exactly what you’re wanting. I see a new Tesla in your future :)

seltzered_• 7 years ago

2015 and later variants of the Prius already have this via the solar roof option: https://www.jpauleytoyota.com/blog/how-does-the-toyota-prius...

“If you want to activate the solar powered ventilation system before you get out of the vehicle it is a simple process. On the left side of the steering column, you will find a small square button with a car and fan on it. Press this button before you turn off your vehicle and you are all set. Next time you get in your Toyota Prius it will be nice and cool.”

Edit: apparently it’s limited to running the fan, there’s also a remote a/c option that’ll run for a few minutes off of battery before you get to the car.

temporaryvector6• 7 years ago

I did not know that, and neither did the salesman when I was choosing my current car. They really should put that feature front and center, at least locally. Maybe that option isn't available in this market.

tda• 7 years ago

The solar roof for running a fan has been around since the 2010 prius.

sundvor• 7 years ago

Even just running the fan on a 45c day should have a huge impact on the internal temperatures of the car.

You can easily hit ~85c (+/-) in very little time then; sadly lots of children / pets are killed all the time as people are just dumb, ignorant, or forgetful.

pbhjpbhj• 7 years ago

Seems like a specialised window AC unit could work, run it off solar panels on the dash board. Maybe not safe for insecure areas but a controlled work car-park .. but then you could probably just leave your windows open in 'safe' places.

dev_dull• 7 years ago

Great idea! Much of this cooling can probably be accomplished by better sun shading and airflow. I always thought this[1] type of privacy glass would be a great idea in a car. Put it in park and the windows automatically tint.

http://www.smartglassinternational.com/electric-switchable-g...

koreyb• 7 years ago

It hits these temps in Phoenix; huge market for Tesla's. They have cabin overheat protection plus you can start the AC from an app on your phone. Really nice!

dd36• 7 years ago

Tesla will keep your car at 105F or less while parked unless your battery is too low.

dghughes• 7 years ago

Electrically adjustable tint for windows would be a better option if it existed. Keep the heat out instead of dealing with it after it heats up the interior.

Just regular tint would be good too. I'm not sure if there are tints which block depending on the angle of the sun.

mixmastamyk3• 7 years ago

My old car had a sunroof that could also tilt up. That took the edge off and let excessive heat escape. Combined with a reflective windshield shade it worked reasonably well. Not chilly but more practical and env friendly than running AC for 8 hours a day.

mrb• 7 years ago

«somebody makes a car that can run the AC without running/draining the battery while it's parked»

Temperatures could be reduced significantly with a car modification that uses very little energy: a small fan to circulate and replace all inside air with outside air, and a one-piece reflective foil cover on top of the car, covering the entire windshield + roof + sides + rear windshield.

jacobmassey• 7 years ago

In the meantime, maybe roll your windows down when you get in the car?

ambicapter• 7 years ago

My car's outside thermometer showed 48°C

In case you wanted to feel like you were in a blast furnace instead of an oven?

unfoldedCravat• 7 years ago

A couple of the old Priuses used to have a solar powered fan. I can’t find any good info on it at the moment but IIRC it was basically a computer fan coupled to a small solar panel so don’t think it was too effective.

https://priuschat.com/threads/solar-powered-fan-is-it-workin...

Johnny5556• 7 years ago

Many modern Hybrids run the AC off battery so would it be sufficient to buy a hybrid with an app that can do "remote start" so you can turn on the car an hour before you leave work?

golover721• 7 years ago

Electric car or not, a very low tech but effective approach is to use a decent sunshade. Quick to set up, and have been shown to lower the internal temperature 20 degrees or so.

syntaxing• 7 years ago

Toyota Prius had (has?) something similar. They had this add on where they install a 100W panel on the roof to run the car fan to vent outside air in and inside air out. One of my coworkers had it and the car temperature was significantly lower during the summer days during lunch.

nikhizzle• 7 years ago

My gasoline Volvo has a feature where you can run the ac/heater remotely from a watch and phone app. It is limited to 15 minutes, but I find 5 minutes at full blast makes it very nice when I get in.

I believe hybrid Volvos can do this while using the battery.

sxates• 7 years ago

I had this feature on my old 2007 Audi A6, which replaced the moon roof with a solar sun roof, which powered a fresh air fan when parked in the sun. I purchased it off-lease, and it was pretty much maxed out on features. I never saw another A6 with the solar option - I think it had to be special ordered from the factory. A shame, it was really handy in the Texas heat.

Now I have a tesla which can just run the AC at will, which is even better :)

bamboozled• 7 years ago

Actually, in Tokyo I noticed it's common for drivers to wait for their clients for hours, sleeping in the car with the air conditioner on with the engine running, hopefully this is one step closer towards solving that issue!

quaa55• 7 years ago

Someone mentioned dog mode in a Tesla, but that’s not the only feature that does this. Dog mode or Camping mode is for keeping the interior at something around 20c or whatever you set.

from reading your comment it sounds like you just don’t want the interior to ever get over 35c, which is exactly what the Cabin Overheat Protection mode is. Basically this is a set it and forget it setting that ensures the inside will never go over 100F. You can choose to use ac which kicks it on and off every so often using minimal range, or you can choose for it to only use outside ambient air, granted it if it’s 48c then you are only getting as cold as that.

check out this article and video https://insideevs.com/news/340230/how-much-does-cabin-overhe...

fred_is_fred• 7 years ago

Just an idea but maybe you shouldn't run errands at noon anymore? Twice to the ER from running errands seems extreme.

realityman3• 7 years ago

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't totally impossible. Typical average insolation at populous latitudes is around 200W/m^2.

SigmundA3• 7 years ago

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

walrus013• 7 years ago

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.

gameswithgo3• 7 years ago

And then you have to figure, if you took the $ and mass budget of the solar cells, could you just make the battery pack a little bigger/better instead for the same or more gain? Keep in mind the gain would be more reliable. You wouldn't have to depend on sunny days, and sunny parking spaces.

You also have to ask if the $ spent on these solar panels might be better spent on your house, where they will never be in an indoor garage, and maybe cheaper/simpler to install.

Finnucane2• 7 years ago

Not everyone has a garage, or can practically run a line out to the street. A self-charging car would be a good option for many. The charge this can manage is more than I drive, i’d Be very interested.

m4632• 7 years ago

I think 10kwh is too generous. I would think ~ 5kwh.

The Tesla model 3 is rated as 237 watt-hours/mile, but this article shows 218 wh/mi at 65mph

https://forum.abetterrouteplanner.com/blogs/entry/13-model-3...

Using that exact figure would require 6kwh, and driving slower would require less.

SigmundA3• 7 years ago

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?

singularity2001• 7 years ago

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)!

walrus013• 7 years ago

I've never seen triple junction GaAs raw cells sell for less than $6/watt stc rating.

For comparison I can buy pallet loads of 72 cell, 370W panels built from high efficiency mono Si cells for under $0.55/watt stc.

kevin_b_er• 7 years ago

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.

walrus013• 7 years ago

I will literally believe somebody has successfully commercialized triple junction GaAs cells, when I can pull out my Visa card and order a pallet of 20 assembled modules from a distributor. As I can do now for 54, 60 and 72 cell panels built from high quality 156mm monocrystalline Si cells.

Until then I think triple junction GaAs is going to see the most use in experimental UAVs funded by research money, and satellites.

cellular• 7 years ago

We used to fight for the shady parking spots.

Imagine the future when you fight for the sunny ones.

benj1114• 7 years ago

Who wrote this?

"This demo car’s prototype cells can convert solar energy at 34% and up"

34% what?

"Using a redesigned solar battery cell film that measures only 0.03 mm"

0.03mm wide? Long? And what's a solar battery cell film???

et2o4• 7 years ago

The efficiency percentage on a solar panel refers to the amount of radiated energy from sunlight that can be converted into electricity. https://en.m.wikipedia.org/wiki/Solar_cell_efficiency

Less sure about the 0.03mm but I'm guessing the relevant metric would be thickness or depth.

benj1114• 7 years ago

I know that, its sloppy writing not to state it though.

sokoloff• 7 years ago

A quarter to half the thickness of a strand of human hair? That seems like an insane innovation (and difficult to produce/keep reliable in the field).

myroon5• 7 years ago

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

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