
Hyundai launches car with a roof-based solar charging system - prostoalex
https://www.cnbc.com/2019/08/05/hyundai-launches-car-with-a-roof-based-solar-charging-system.html
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mikestew
I see a lot of folks in this thread doing the math of how this works out,
which is great, hard numbers == good. But as one who went to a considerable
amount of effort and research to put solar on the roof of our RV camper (which
has a _lot_ more roof than a Hyundai), and as one who owns a Nissan Leaf and
knows how much an EV draws, I needed no napkin to know it was a gimmick before
I even clicked the link.

Cramming a panel on every bit of usable space, using the best panels my money
could buy me, got us 410W (26' RV, kinda small). That'll _almost_ run half a
microwave under perfect conditions at noon on the summer solstice. It is a
long enough way from running a car that I'll use the napkin to wipe burrito
sauce away.

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vladojsem
I get your point. So is roof-based solar pure marketing?

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mikestew
I mean, they're not _lying_. I just don't think it's worth the opportunity
cost for the measly added mileage you get. If they can put solar up there,
then I'd rather have a full-glass roof.

EDIT: And now that you make me think about it more, it's just dumb; or maybe
an interim solution at best. Because solar panels on the roof of my house is
much more scalable, efficient, and for the same power output, less expensive
(no one does crash-tests on my house roof). The "interim" part comes from
admitting that residential roof solar is quite uncommon, but hopefully not
forever.

Let me edit some more with an extreme example: my electric scooter that I ride
work every day. I _could_ squeeze some panel on there somewhere, and add a
teensy bit of extra mileage. But I won't, because remember that RV solar I
talked about? Most of the time it's just sitting there doing nothing, so I ran
an extension cord from the inverter to the scooter and electric bicycles. Now
our Personal Electric Vehicles are solar-powered, and all I did was run an
extension cord. (Tiny though it might be, the RV solar can easily handle a
scooter and some bikes.)

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erik_seaberg
Rooftop solar requires landlord permission and wiring a reserved parking
space, which works if you own a house and garage but it's a pretty big
impediment to wider apartment coverage.

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mikestew
I completely get where you're coming from. Buuuut, in this case it's as if you
don't have availability at your apartment for a Level 2 charger, so Hyundai
gives you one of those little hand-cranked generators.

~~~
erik_seaberg
Yeah, it would take a lot of squirrels on exercise wheels to add up to what
this unit can do.

But none of these are really going to move the car much more than pushing it.

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GhostVII
It would be a lot more useful to just put up solar panels wherever the car is
being charged - it's not like the car is going to be able to gain any
reasonable amount of range from the roof-based solar between charges anyways,
so there isn't much benefit from having the solar panels on the car itself.
Why put them on something that moves when you don't have to, for the cost of
the solar panels on the car you could probably build much bigger solar panels
over your parking spot or garage. Interesting gimmick, but I don't see how it
is useful unless you don't have anywhere else to put solar, and even then it
isn't saving you much.

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odonnellryan
Plenty of people put there car outdoors but in places where solar on the
ground is not feasible. I do. I leave my car for 3-4 days without using it.
That is 18 hours of charge, that's a lot of energy.

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GhostVII
Sure, so I suppose it can noticeably extend your time between charges if you
rarely use your car, leave it outside in the sun for long periods of time, and
don't have access to charging anywhere you regularly park your car. Seems like
if that is the case though, an electric car isn't a great fit - regular access
to charging is pretty critical unless you want to wait around at a charging
station for an hour every time you need to fill up.

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gumby
I don't see how the math could ever work out. GNI in the mohave is on the
order of 1 kW/m2 for the daylight period. A car roof, perhaps 1 m2 if you are
generous, won't be oriented well much if any of the day.

So is there any more than PR value to this?

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Retric
This thing is very much a marketing gimmick, but the idea is not horrible.

A Toyota Camry is 4.9 meters long and 1.8 meters wide. That’s almost 9m2, if
they can cover ~2/3 of that with panels you’re talking around 6m2. You don’t
get to tilt the panels, but you can put them on the sides which makes up for
it.

Space is limited so using 30+% efficient panels is reasonable. That’s 1.8+ kw
in full sun which is about 5.4 miles of range per hour. These numbers are
appropriate, but when you start talking 40+ miles extra range per day that’s
not worthless.

Use fewer lower efficiency panels and 20 miles per day should be cheap. This
is well below that.

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gumby
it's not like people haven't thought about this a lot over the years. I've
worked in both industries (solar power and on the electrical engineering side
of automotive) and have seen these calculations over and over.

On space: the car may be that size but the roof is smaller. The car tends to
get dirty, be in absurd orientations, etc. Plus don't you want to park in the
shade if possible? Ever driven in a city?

You're suggesting multi-junction cells which cost an order of magnitude more
than mass production polysilicon cells. For a vehicle where they are trying to
trim the BOM by pennies (e.g. resorting to 8-bit CPUs in the ECU).

I mean, great, more power (ahem) to them, but I can't make the math work.

It's like the BIPV roof that musk keeps promising for delivery by 2016 or
sooner: people have been making them for years and year and yet somehow they
don't get deployed. Why? Well physics and economic factors like labor to
start, as well as safety (which is the killer issue for me) and, quite
significantly, aesthetics, which a lot of people seem to care about (I don't).
Having the idea, and even making them, is the easiest part of getting them
deployed.

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clairity
BIPV = building-integrated photovoltaics (for those, like me, who haven't run
into the acronym before)

as for my 2¢, regardless of the technical merits, i'm all for more solar. it's
earth's ultimate energy source. let's cut out the intermediaries, particularly
the unrenewable ones.

regarding economics, it may not make a lot of sense on a cost basis, but as
others have noted, it may make sense from a value basis (i.e., higher profit
margins).

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Evidlo
Maybe a more useful application would be to use the panels to run air
conditioning and keep the car cool in a hot parking lot.

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rory096
Prius has had that for a decade: [https://blog.toyota.co.uk/solar-powered-
ventilation-prius](https://blog.toyota.co.uk/solar-powered-ventilation-prius)

~~~
asdkhadsj
It is _hugely helpful_. My car is still very hot on hot days, but I'm no
longer being burned quite as easily by my steering wheel, belt buckle, seat,
etc.

The difference is quite noticeable. Especially on days/mornings/etc where it's
relatively cool but the sun is hot. The air circulation really does wonders.

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pwinnski
Their claims are somewhat surprising, and I guess they reflect advances in
solar cells. My 2014 Prius has a rooftop solar panel, smaller than depicted,
and uses it solely to power a fan while the car is off.

Then again, the battery pack in the Prius (not Prime) is so small, perhaps it
wasn't worth trying to connect the two.

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jerf
"With six hours of charge per day, the vehicle could increase travel distances
by 1,300 kilometers per year." (or 800 miles per year)

One of the things I do to keep myself accountable for all the subscriptions in
modern life is to annualize them, so it's not "just $10/month!" but "$120".
But in this case, I think we want to flip it around; at 6 hours of charging
you're going to get... approximately two miles _per day_. Three if you're
inclined to round up through the pile of lossy conversions I'm pushing that
number through. And that's only going to be in play when the battery is not
already full, and it probably won't work while you're charging, either,
because the charger will be saturating the battery's incoming charge rate.

I don't find anything particularly unbelievable about that, but it's a
marketing stunt, not a good engineering idea, as evidenced by trying to
present this in terms of "km per year". That's worthless, swamped in the noise
of how your driving style will affect your mileage on an electric car (or any
car).

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dmix
The idea of your vehicle sitting there and gathering "clean" energy has a
feel-good thing to it, so it's definitely useful as a marketing gimmick to the
green people.

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jerf
More productively, if you are worried about this sort of thing, you can
recover this amount of energy most likely today if you Google the term
"hypermiling", read up, think, and then don't do anything stupid but tweak
your driving style with what you read. Bonus, you can do this with any type of
car, including whatever it is you are driving now.

This will cut your energy usage by wildly more than anything this solar panel
can do.

However, please let me re-iterate, don't do anything stupid. That term will
lead you to some stupid things to save trivial amounts of energy.

~~~
dmix
As long as it doesn't involve going 5km/hr down an offramp hill because you
don't _have_ to use gas but there's a massive gap in front of you and a
hundred cars behind you forced to go your speed (which is far more challenging
at low speeds, especially with a standard vehicle like mine). It's a really
selfish and inefficent move IMO and I see it all the time in the city from a
small group of people.

If you want to save gas go into neutral and go as fast as everyone else or
don't do it unless you're alone.

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newnewpdro
It's obviously marketing and gimmicky, but I just wanted to note that I've
used a portable 85W solar panel to keep my little 4-banger econobox running
when my alternator failed on a road trip.

Saved me the cost of a tow and expensive repair wherever the tow truck took me
to. Instead I was able to drive back to civilization proper and have the
alternator rebuilt locally for $75.

So I think having solar panels for assisting the alternator on an otherwise
conventional econobox could at least be useful in terms of redundancy. It
would improve the MPG slightly in the daytime as well, offloading the
alternator.

In a hybrid that can operate entirely off batteries, a rooftop solar system
could get you out of an out of gas in the middle of nowhere bind if you've got
plenty of time, food, and water on your hands.

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Gys
> With six hours of charge per day, the vehicle could increase travel
> distances by 1,300 kilometers per year.

So a six hours charge adds 3.56 km. This does not seem very useful to me if
one uses the car to commute and charges every night anyway.

~~~
gregmac
Using 4.43 KM per kWh (based on the plug-in hybrid model [1]), that means the
six hour charge is 0.8kWh.

At 12 cents per kWh, that means if you get six hours of solar every day (365
days), you'll save about $44 per year in electricity costs.

The average person has a car for 6.6 years [2], so that adds up to a whopping
$289 in savings (assuming constant electricity prices, anyway). I wonder how
much extra the solar panel costs?

[1]
[https://www.greencarcongress.com/2018/02/20180209-hyundai.ht...](https://www.greencarcongress.com/2018/02/20180209-hyundai.html)

[2] [https://www.cnbc.com/2017/05/28/car-owners-are-holding-
their...](https://www.cnbc.com/2017/05/28/car-owners-are-holding-their-
vehicles-for-longer-which-is-both-good-and-bad.html)

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daenz
We should stop and consider that Hyundai engineers know the energy math behind
this design, and they know it's ridiculous, but management chose to pursue
this line regardless. This says a lot about their perceived market.

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izzydata
How much does this add to the cost of the vehicle and how long would it take
for it to pay for itself? Would it take longer than the average lifespan of
the vehicle?

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williamDafoe
2 miles a day is about how much our Tesla m3 loses by self discharge and
parasitic loads.

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YeahSureWhyNot
why not double the area by installing panels on hood and top of the trunk too?
are panels very heavy? at least on hood since its not opened often.

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YeahSureWhyNot
they should have tried this on a crossover type of a vehicle that has twice
the roof surface compared to a sedan

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moonbug
A gimmick for the innumerate.

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rasz
Stop with the math guys, that solar panel simply _feels_ right. Feels sell
very well.

/Yes, its a tax on stupid.

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bdamm
The real question is, how strong does the ramp that I'm going to drive two
wheels up on to tip the roof to the sun need to be? Can I build it out of 2x4s
and 3/4" plywood and how far apart do the offsets need to be? Is it OK to
leave a car parked for long periods at a 30 degree angle?

