larger solar panel/solar roof on Leaf thread

My Nissan Leaf Forum

Help Support My Nissan Leaf Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

cwerdna

Well-known member
Joined
Jun 3, 2011
Messages
13,671
Location
SF Bay Area, CA
Let's discuss the solar panel/roof issues that were brought up in http://www.mynissanleaf.com/viewtopic.php?p=142154#p142154" onclick="window.open(this.href);return false; (Nissan LEAF Engineering Team Visit December 3rd) so that we can keep the other topic on track.

I wanted to bring up a few points. AFAIK, the solar roof panel on available on the 3rd gen Prius only can deliver about 60 watts max. See http://priuschat.com/forums/gen-iii-2010-prius-accessories-modifications/57681-hacking-solar-9.html#post917560" onclick="window.open(this.href);return false; and a few posts further down. You can probably find more posts by Googling for site:priuschat.com solar roof watts. It only runs the ventilation fan when the car is parked. 5 kw seems completely impossible. I don't know state of the art in solar, but even 1 kw sounds way off.

I hope people realize that 1 hp = ~746 watts.

Some people pointed out 200+ watts for minimal AC. 200 watts is REALLY minimal and doubt it'd do any good. I can tell you that when looking at Scangauge on my 2nd gen Prius that when idling, my car draws ~1.2 - 2 amps (@~220 volts). If I I turn on my (electrically driven) AC, the draw becomes 4.x to 9.x amps, sometimes even 10 amps (I've posted the numbers at http://priuschat.com/forums/gen-iii-2010-prius-fuel-economy/68603-same-prius-not-same-mpg-11.html#post1146128" onclick="window.open(this.href);return false; before).

On Priuschat, we were disappointed to learn that the solar roof couldn't charge the HV battery. Some explanations were given at http://priuschat.com/forums/gen-iii-2010-prius-main-forum/60635-scientific-american-article-2010-prius.html" onclick="window.open(this.href);return false; and http://priuschat.com/forums/gen-iii-2010-prius-main-forum/60635-scientific-american-article-2010-prius.html#post831221" onclick="window.open(this.href);return false;. I'm no EE so I can't comment on the accuracy of that. Others can chime in on that.
 
i agree Solar on the roof is not cost practical, but i am not against having it as an option. people will pay good money for the craziest things.

but i know a guy who has solar panels. they are 300 watts and it would have to be trimmed a bit to fit on the roof of my Leaf. also around here even in optimum Sun, its only max'd out at like 75% efficient (we too far north really) and that is only for a few hours a day. the rest of the day its like 40-50%

but solar is getting better and better all the time. dont discount the technology, but i think it would still be cheaper to simply install more charging stations in public. put in one for every 10 gas stations, there would be so little range anxiety left it we would simply laugh looking back at this thread.
 
Thanks for starting the thread! I've been working in Solar Energy for the last 5 years, with a variety of technologies. So, IMHO:
As ElectricVehicle said over in the Engineering Team Meeting thread, about the best we'll do today (or in the short term) is 200 Watts peak, which will need to be derated (we typically derate down to 78-82% of peak, depending on losses). That's not enough to generate a lot of motive power but would do well in running ventilation. I've noticed that, once the car is cooled off, the A/C runs at about 300-500 Watts. There are versions of thin film technology that talk about applications as "car paint" but durability and efficiency aren't there to support it anytime soon. 200 Watts could be pretty useful for stationary application as others have said.
 
I don't know about the efficiency of Solar PV but that's not the only way to harness the sun's energy.

How about an array of Fresnel lenses creating a solar concentrator and powering a Stirling engine to charge a battery. Could there be more output than PV or is it still infeasible. Of course this is all pie in the sky stuff, so humor me. ;)

[youtube]http://www.youtube.com/watch?v=A_AFnW1bZL8[/youtube]

At the end of the day, anything you add to the top of a car is going to add weight and bring down efficiency as a result.
 
Sunpower makes a 320 Watt panel that's essentially the same size as the Leaf roof (that's a 19% efficiency panel). San Diego gets 5.5 hours of usable sun a day. So that's 1.76 kwh a day, or just under a fuel bar.

That's not insignificant! Sure you can't recharge in a day, but that's 6.5 miles for me. Every day. For the life of the car (the solar panel will outlast the car). I could leave it out in the middle of a field with an empty battery and in a week it would be able to drive 45 miles.

So what about cost? That panel probably costs $1,500 (19% efficiency isn't cheap). House roof systems have considerable installation costs because every roof is different, but with a car once the design engineering is done they're just going to stamp them out by the hundreds of thousands at the factory. I imagine they could make the part for $2K (that's a total stab in the dark, I should be clear that I don't know jack about mass producing glass car roofs).

At that cost it probably won't pay for itself over the life of the vehicle, but I'd get it just because it would be awesome.

Of course solar panels get cheaper every day, there are solar panels now that cost near $1/watt and are 12% efficient. That would be 1.1 kwh a day for $200 plus whatever the mass produced glass roof would cost.

(these are best case numbers, but even after you regulate down 80% it's still significant amounts of power)
 
Dgaetano said:
Sunpower makes a 320 Watt panel that's essentially the same size as the Leaf roof (that's a 19% efficiency panel). San Diego gets 5.5 hours of usable sun a day. So that's 1.76 kwh a day, or just under a fuel bar.
I think you'll be lucky to get half of that, even if you park outside in unobstructed sunlight. The solar panels need to be pointed directly at the sun. The LEAF is not a flat surface pointed at the sun. And if you have a Solar Panel the size of the LEAF roof, your color options are limited - Solar panels don't come in Cayenne Red or Ocean Blue...

Of course, it could be nice because all the other cars would be parked in the parking space lines, while all the LEAFs will be crossing the lines for the best sun facing angle, all worshipping the sun!

If a lamp post shades the panels, a building or a tree casts a shadow, the cells are wired in a series or series / parallel arrangement so shading one cell can dramatically reduce the output.

The sun, under peak conditions is about 1000W/m**2. Solar panel efficiencies are in the 13 - 22% range. That's 130 to 220 watts/m**2, ideally.

SunPower® solar cells currently hold the world record in efficiency at 22.4 percent. http://us.sunpowercorp.com/about/the-worlds-standard-for-solar/" onclick="window.open(this.href);return false;

LEAF roof area for solar is around 60" x 42" or 1.5m x 1.1m = 1.65m**2

215 to 360 watts ideally for the roof.

Arbitrarily estimating various factors for not being perpendicular (facing) the sun throughout the day (declination for the latitude and time of year, not tracking the sun...) would derate around 70%, the sun not being at ideal output, panels not at ideal temperature, atmospheric dust or light smog blocking some light etc. - derate 80%. 70% x 80% = 56%.

56% * 215 to 360 watts ideally = 120 to 200 watts practically

Others on the forum can come up with better numbers, but I think it's pretty clear that for the roof alone, you won't get more than 250 watts. Other surfaces will have less ideal facing to the sun and even greater aesthetic impact, so limiting to the roof seems pretty reasonable.

100 - 200 watts won't run the AC or heat full force, it won't be enough to maintain temperature on hot days. If the AC is capable of utilizing low power, it would make the car much cooler or warmer than it would be with no fan and no AC. (if cars wre well insulated, this low power could come close to maintaining temperature, but they aren't and there is a lot of single pane window area in a car.)

http://www.nrel.gov/rredc/solar_resource.html" onclick="window.open(this.href);return false;

I see the Sunpower 315 is 19% efficient and meaures 61.39" x 41.18" with a max power of 320W. If all the derating factors came to 62%, this panel would produce 200 Watts. It weighs 41 lbs, though if the frame were removed and it was integrated into the LEAF body, it might add only 20 pounds to the weight of the car. This panel certainly sets the upper bound for power from the roof at 300 watts or less real world. According to SunPower there aren't any panels that are more efficient (power produced / unit area (well technically incident sunlight energy)).
http://us.sunpowercorp.com/cs/BlobServer?blobkey=id&blobwhere=1300258626967&blobheadername2=Content-Disposition&blobheadername1=Content-Type&blobheadervalue2=inline%3B+filename%3Dsp_e19320wh_ds_en_ltr_w_223%252C0.pdf&blobheadervalue1=application%2Fpdf&blobcol=urldata&blobtable=MungoBlobs" onclick="window.open(this.href);return false;

The solar panels must not affect the aerodynamics of the car or add more than a couple pounds to the weight or they will cause more losses while driving than the power they generate. So bolting a commercial solar module to the roof with a 1 inch module edge exposed in the airflow around the LEAF body would be a big net energy loser due to poor aerodynamics!
 
While a PV roof would be cool, it would not provide much practical benefit. IMHO the front lines of PV are in the efficiency/cost of panels. The front lines of EV's are battery capacity, charge times and pack weight.

The contribution of a PV roof on an EV does have a great image and could help market the simplicity of powering a car directly from the sun. This does have a high educational/awareness value, but at a price.
 
TRONZ said:
The contribution of a PV roof on an EV does have a great image and could help market the simplicity of powering a car directly from the sun. This does have a high educational/awareness value, but at a price.

This is the part I don't get. What's the educational/awareness value of putting an irrelevant solar trinket on the roof? Who learned what? So far, it's only the uneducated/misinformed that assign any value to it.

"So you never have to plug it in, because of that solahr-lectric thing on the spoiler? Awesome."

"Uh, no. It's a useless greenwashing stylistic element that serves no useful purpose whatsoever. It's back there actively giving solar panels a bad name. It would take the whole roof of that gas station to power this car."
 
When derating the panel, don't forget the light transmission through the protective medium. I don't know that Nissan is going to put laminated, tempered glass up there on the roof of the LEAF, followed by another coating to keep the rocks that fall on it (from overloaded gravel trucks on I-880) from breaking the glass. So I'd take another chunk of change off that 200 Watts. Maybe more like 150 Watts useful.

Having said that, it would be cool to ventilate the LEAF while not plugged in and not using the battery.
 
shay said:
gascant said:
Having said that, it would be cool to ventilate the LEAF while not plugged in and not using the battery.
I have always had the same thought.
Thank you for setting up the thread, makes an interesting read. I was going to reference prior threads on the topic, but not all of them seem to be relevant. Perhaps this could be done later. If Nissan was considering this, and they did not want to come up with a solar roof option, they could simply use the space on the rear spoiler better. It appears that some prototype Leafs did just that: they had a solar panel twice of perhaps three times the size of the current one.

Screen%252520shot%2525202011-10-19%252520at%2525207.44.04%252520PM.png
 
shay said:
gascant said:
Having said that, it would be cool to ventilate the LEAF while not plugged in and not using the battery.
I have always had the same thought.
They'd likely need to go w/a larger panel than the one on the Leaf now, like the one on the Prius' optional solar roof.

BTW, page 13 https://techinfo.toyota.com/techInfoPortal/staticcontent/en/techinfo/html/prelogin/docs/3rdprius.pdf" onclick="window.open(this.href);return false; discusses the panel's output.
 
Guys, as an engineer, I can say that adding any amount of Solar panels to the body panels of the LEAF will not do hardly anything for range. Your best money and effort is to put these on your HOUSE where they can have the most benefit, and charge your LEAF from them, and the energy banked into the grid.

As someone pointed out, if you just added the extra weight of the panels in as more Lithium Ion, you'd do at least an order magnitude better for range!

The only practical use for a solar add on has already been pointed out, and demonstrated by Toyota: Ventilation. Toyota's rather expensive option only cools the car on a hot day, as that's all the current state of the art in solar can really do for a road going ton and a half vehicle.

For all the people that still think this is a good idea, PLEASE go take a high-school level physics class and come back with your reality.

Sorry to be a downer, but the Physics just don't work, even if we somehow double the efficiency of the existing photovoltaic materials available, or put the LEAF into Geosynchronous orbit at 22,000 miles up!

-Phil
 
I'll throw out another concept, the only way to actually claim the use of solar power for your driving is to use the solar panel output directly. Grid tie doesn't actually count since you can have grid tie solar with or without an EV, and the EV is just an extra draw on the grid. Will 100-200 watts of solar on the car itself make a real difference in your range? Probably not. But if you get 2-3 miles of range each day of your 20-30 mile commute from solar on the car then you've improved the emissions profile of your power use by 10%. I don't see an extra 40lbs or so as much of hit to your efficiency, does your range drop noticeably if you have your dog or kid in the car, or a bunch of groceries?
 
GroundLoop said:
This is the part I don't get. What's the educational/awareness value of putting an irrelevant solar trinket on the roof? Who learned what? So far, it's only the uneducated/misinformed that assign any value to it.
"So you never have to plug it in, because of that solahr-lectric thing on the spoiler? Awesome."
"Uh, no. It's a useless greenwashing stylistic element that serves no useful purpose whatsoever. It's back there actively giving solar panels a bad name. It would take the whole roof of that gas station to power this car."

It would be a welcomed teaching moment, you could go into detail on what it takes to power a city and the issues with solar, wind and PV.. mention dirty coal (you could bring a sample of coal dust in a jar.. like a boy scout, always be prepared) and then segue into the only real alternative.. advanced nuclear power and the damage that doom&gloomers are doing to our future.
 
JRP3 said:
I'll throw out another concept, the only way to actually claim the use of solar power for your driving is to use the solar panel output directly. Grid tie doesn't actually count ...
Utter bovine excrement.
 
Ingineer said:
Guys, as an engineer, I can say that adding any amount of Solar panels to the body panels of the LEAF will not do hardly anything for range. Your best money and effort is to put these on your HOUSE where they can have the most benefit, and charge your LEAF from them, and the energy banked into the grid.

As someone pointed out, if you just added the extra weight of the panels in as more Lithium Ion, you'd do at least an order magnitude better for range!

The only practical use for a solar add on has already been pointed out, and demonstrated by Toyota: Ventilation. Toyota's rather expensive option only cools the car on a hot day, as that's all the current state of the art in solar can really do for a road going ton and a half vehicle.

For all the people that still think this is a good idea, PLEASE go take a high-school level physics class and come back with your reality.

Sorry to be a downer, but the Physics just don't work, even if we somehow double the efficiency of the existing photovoltaic materials available, or put the LEAF into Geosynchronous orbit at 22,000 miles up!

-Phil

Phil, I wonder how many folks who want to expand the solar panel on the Leaf actually think they would get much benefit from it in terms of range. I think the argument for the solar panel, affectionately known as the gimmick, is more in line with an early adapter's over all philosophy of supporting technology sometimes for it's own sake to help spur it along and for PR. One could argue that the $110K roadster wasn't exactly practical but it's hard to argue that it didn't help usher in the new age of EV's. Solar panels on cars could help spread awareness of PV in a similar way. The $70 LED lightbulb comes to mind, many early adapters bought them to support the technology and help it reach economy of scale, don't ask about the ROI, you could certainly do better in the stock market ... I was in that boat and I went for the gimmick on the Leaf for the same reason. I also see it as a seed concept, encouraging people to think about where and how that electricity that will be charging millions of cars in the near future is coming from. Without careful thought, electric cars may very well spur the next nuclear energy revolution if they become widely adopted, at least some will argue that, even though EV's stand to reduce baseload waste. Many people will assume that the only way to fully electrify the highways is to support expansion of traditional power plants. I think promoting renewable energy and EV's needs to go hand in hand, kind of a no brainer for most of us, but not so much for the mainstream that we hope will adopt this technology.

As a fashion statement, a flag for alternative energy, a mind opener, I have no problem with people wanting to expand the solar panel concept on the Leaf, no less justifiable than lowering the suspension or some other personal preference, but yes the latest in PV, applied to the car, is hardly going to add a drop in the energy bucket for these cars but it could help to expand consciousness and some will find that compelling. I do think there is an argument for having a full roof top and even hood option available, forget about practical, it would be cool!
 
GaslessInSeattle said:
... One could argue that the $110K roadster wasn't exactly practical but it's hard to argue that it didn't help usher in the new age of EV's. Solar panels on cars could help spread awareness of PV in a similar way. The $70 LED lightbulb comes to mind, many early adapters bought them to support the technology and help it reach economy of scale, don't ask about the ROI, you could certainly do better in the stock market ...
But the $110k roadster and the $70 LED flashlight actually worked as a usable car and a usable flashlight...something that mounting a solar panels on a LEAF's doesn't achieve.
 
davewill said:
GaslessInSeattle said:
... One could argue that the $110K roadster wasn't exactly practical but it's hard to argue that it didn't help usher in the new age of EV's. Solar panels on cars could help spread awareness of PV in a similar way. The $70 LED lightbulb comes to mind, many early adapters bought them to support the technology and help it reach economy of scale, don't ask about the ROI, you could certainly do better in the stock market ...
But the $110k roadster and the $70 LED flashlight actually worked as a usable car and a usable flashlight...something that mounting a solar panels on a LEAF's doesn't achieve.
I can see the point, but it could also backfire in representing to the common lay-person that you could drive the LEAF on solar power and not have to plug in. Not only would it really not change in any way how you operate the car, it would be somewhat deceptive.

Personally, if I lived in San Diego, Dallas, or somewhere else where there is a lot of sun, I would pay an extra $1k to get the Solar ventilation option. (Like Toyota offers on the Prius) Just keeping the car cool in when parked in the summer sun could offset the hit to the pack from running the A/C full bore upon returning to the car, and also drastically improve comfort.

But connecting said solar array to the pack wouldn't do much unless you park for weeks at a time in the sun and seldom drive.

As I said, put it on your house, then you get dual-benefits!

-Phil
 
Back
Top