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

~~~
hwillis
> 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.

~~~
temporaryvector
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.

~~~
hwillis
Even on constant full blast with the smallest battery Tesla sells, it's only
gonna use ~2-3% per hour. Over 8 hours that would be 44 miles off the 220 mile
range.

> but it is probably the only reason I'm considering a Tesla if it ever comes
> to my city

Hmm, Telsa _should_ be pretty reachable. Perth and El Paso look like some of
the only neglected hot cities.

~~~
temporaryvector
I don't live in the US, as far as I'm aware there's only one Tesla store in my
country and it's nowhere near me.

~~~
hwillis
I figured- Perth is in Australia. If you're in Mexico you're pretty screwed,
as is... South America, Africa, and most of Asia. You can check the map if you
like!

[https://www.tesla.com/findus?v=2&bounds=67.51085725091038%2C...](https://www.tesla.com/findus?v=2&bounds=67.51085725091038%2C-33.63623082835784%2C-15.19361167862115%2C-144.99365270335784&zoom=4&filters=store)

~~~
temporaryvector
Mexico. I'm actually surprised there's one charging point in my city. I'd
expect there to be none.

I'm pretty hopeful that we'll either get Tesla in a couple of years or other
manufacturers will come out with something.

------
realityman
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.

~~~
gameswithgo
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.

~~~
Finnucane
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.

~~~
gameswithgo
It manages more than you can drive in ideal conditions. Sunny day, parked in
the sun during the day, for probably a ton of extra cost (they are using very
fancy solar cells). That might work for people who have a backup plan in
arizona with unshaded parking spots available. Hopefully charging stations at
apartments and city centers will continue to proliferate to make electric cars
viable for more people.

~~~
Finnucane
My normal driving is 100 miles a month, mainly on weekends. Plus, I assume
they’ll improve capacity over time. Even if it meant having to go to a public
charger once in a while, it would still be a convenience.

------
lettergram
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.

~~~
penagwin
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
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.

~~~
Marsymars
Insurance companies here have worked out that they save money by cloud seeding
outside of the cities to minimize hail damage in more populated areas.

------
driverdan
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.

~~~
Theodores
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.

------
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.

~~~
walrus01
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.

------
myroon5
See also: [https://lightyear.one/](https://lightyear.one/)

[https://en.wikipedia.org/wiki/List_of_cities_by_sunshine_dur...](https://en.wikipedia.org/wiki/List_of_cities_by_sunshine_duration)

Using those I found Lightyear quotes "271 days of carefree range" for Marsa
Alam, Egypt. Interested if anyone finds a city with a higher quote

------
cellular
We used to fight for the shady parking spots.

Imagine the future when you fight for the sunny ones.

------
CalChris
This is interesting because the solar strip on the Nissan Leaf SL was just a
do hickey, 9 watts max. It was capable of trickle charging the 12V starter
which meant less draw for charging the 12V coming from the traction battery.
Not nothing but really not much. I don't think it even rounded up to a mile of
range.

I'm not sure what's up with the visibility out the rear window of the Honda as
pictured.

~~~
usrusr
> It was capable of trickle charging the 12V starter

Enough to increase the utility of a rarely driven ICE car tenfold.

------
newnewpdro
I once used an 85W portable solar panel to charge my battery while driving
after the alternator failed.

It was surprisingly effective at keeping the car operable, at least until the
sun went down. I didn't have any accessories running, so it was just the
ECU/fuel pump/injectors/ignition it had to keep up with.

The experience left me wondering what MPG improvement it would be to embed
solar cells in the trunk lid and hood for charging the battery in the daytime,
offloading the alternator.

------
SigmundA
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?

~~~
walrus01
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.

------
scotty79
Meanwhile I just discharged 12V battery of my hybrid toyota by sitting inside
with phone plugged in and fans running.

There was no warning and now I have to fiddle with cables and second car to
get my car to start. All while there's still charge in hybrid batteries that I
assume could trickle charge my 12V to help me start the car. But it won't.

------
fri_sch
There's also Sono Motors, a start-up from Munich, Germany. They aim at
delivering something they call a SEV (Solar Electric Vehicle) in 2020. They
have an interesting concept and more than 10k reservations.
[https://sonomotors.com/?lang=en](https://sonomotors.com/?lang=en)

~~~
masonkay
Thanks for sharing the Sono Motors link. The Sion model is to be available in
2021 (or at least that is what I read on their website.) I like this practical
little car with energy interface considerations at its core. Solar body panels
can add up to 34km range per day, this seems to be a major incremental
improvement to the EV model, I think.

Sticker price of 25.5k Euro (16k for base and est. 9.5k for battery) and they
let you buy the battery separately or you can lease one. It seems it will be
manufactured in Sweden (Trollhättan). I want to learn more about their
(export) US market strategy. Needless to say I do like this SEV concept.

~~~
fri_sch
> The Sion model is to be available in 2021 (or at least that is what I read
> on their website.)

2021 will probably be more realistic for delivery. Though they say in their
FAQ that they will start production in the second half of 2020.

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

------
mixmastamyk
Always wanted this, makes a lot of sense in the desert. Is Toyota still
turning on the headlights in the daytime? Seems like it would negate this
advancement.

~~~
Johnny555
You mean DRL's? They lead to a significant reduction in crash rate - and since
much of a car's carbon impact is tied up in the manufacturing of the car, that
is likely a far greater impact than running the DRL's all day.

Plus, with LED DRL's becoming more common, the power drain is much less
significant than the old incandescent lights. My old car ran the 55W
headlights at around 40W each for DRL's. My new car has a DRL LED module that
uses around 3W.

~~~
mixmastamyk
No, the headlights were unable to be turned off on a friend’s old carolla. Was
a while ago though.

~~~
Johnny555
That sounds like DRLs... In some cars they use the headlights at reduced power
as DRLs.

------
pcurve
Without clicking, I was going to post a sarcastic comment about also putting
battery on hood and trunk lid. Then I saw the picture. lol

------
ngcc_hk
The solar one of worked meant I do not have to charge the car for most of the
trips I did!!! Shocking.

------
mikeash
There’s no way it’ll charge while driving. It might discharge more slowly
while driving and charge while parked.

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

~~~
bochoh
>>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.

~~~
SketchySeaBeast
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.

~~~
bochoh
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, non-turbo).

~~~
SketchySeaBeast
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.

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

~~~
SketchySeaBeast
At least they aren't burning liquid dinosaur.

~~~
zamfi
Ultimately depends on how they're charging their Tesla. Could be gasified or
petrified dinosaur!

------
benj111
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???

~~~
et2o
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](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.

~~~
sokoloff
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).

~~~
et2o
[https://en.m.wikipedia.org/wiki/Thin-
film_solar_cell](https://en.m.wikipedia.org/wiki/Thin-film_solar_cell)

This does seem to be the case. It's embedded in a laminate.

