What is the potential of a solar panel on a Model S?

What is the potential of a solar panel on a Model S?

The idea of never going back to the gas station again thrills me. By simply plugging in we will have a fully charged battery just a few hours later; this is great!

However the solar energy driven EV:s develop every year in the races through the sun dryed australian landscape. They look a bit funny, but they move fast.

As I see it, the potential of solar panels on EV:s is great. In the future, maybe you don't even need to plug in to fill your battery with fresh power. That must be the ultimate car! No emissions, no fuelcost and very limited maintenance.

I have read somewhere that the Model S will have a solar panel optional. Is this for running the AC only or can it be used for charging as well? I suppose that the panel will be intergrated somehow in the roof but, wouldn't it be possible to ad another one on the front and rear hood too?

Mr Musk is also involved in SolarCity, whith provides solar panels in California, so I guess that the thougt must have crossed his mind.

Thank U for great cars and website!

Timo | December 4, 2010

Solar power is weak. What you see in those "solar racers" is actually unsafe lightweight aerodynamically shaped solar panels in bicycle wheels that move on flat hard surface. They are not cars in any real way. Real car can't move with solar power.

It takes somewhere around 15-20kW to move real passenger car at 60+mph. You get something like 100-150W/m^2 electricity from Sun with solar panels in a car in good day. That's just too little.

They are expensive and fragile and need to be kept clean in order to work at all. It is much better to use that extra money in batteries, you get a lot more range by that. If you want you can charge your car with solar panels that are in your garage roof. That's much more efficient use of solar panels. Of course that solar roof could be used to charge the car, but you get only about half a mile from it in a hour. Maybe bit over one mile in good day and if it covers the whole roof.

Mike_ModelS_P457 | December 6, 2010

A solar powered car is best accomplished through a residential or commercial photovoltaic (PV) installation charging an EV or PHEV.

I am a huge solar advocate. I added 42 solar panels to my house and produce almost 90% of my own power (two distinct arrays - one south and one west facing on my roof). Still, the efficiency is way to poor given to run a car. I have two very large surfaces covered to get this much power. A car is just too small and won't be ideally oriented to maximize PV production.

On the maintenance point, I disagree that solar needs a lot of care or cleaning. I've had my system almost three years and basically I wash them down once a year and am fine.

Timo | December 6, 2010

Cars get dirty much faster than house roofs. All it takes is one badly selected parking spot in a rain and your car roof is dirty.

Obviously you would also clean your car more often, so maybe it wouldn't be that big an issue, but while your car roof is dirty you wouldn't get much anything from those panels. So in order for them to work you would need to keep them clean.

Brian H | December 8, 2010

Yep, and gold-plate the wheel rims, and use polished platinum for the mirrors, and ....

There are lots better ways to waste money than solar panels on your car. But they're not bad!

Vawlkus | December 8, 2010

You could always take a page out of Fisker's book and have the solar panels run the extra stuff, like heaters, A/C, radio, etc. Catch is it's gonna add to the price, and the Model S isn't cheap to start with.

Mark2131@CA-US | December 18, 2010

Here's an iPhone app to help you figure out how many solar panels it will take to power your Tesla.

When I told my son I bought a Tesla (Model S), it inspired him to create this app. Enjoy.


Dark_Elf | January 7, 2011

And on top of it... you need an inverter build in... witch again takes up weight - more power to drive etc.

Solarpanels alone doesnt do any good... you need something to converter it to something usable.

Solarpanels gives a huge voltage but not that much current = makes it hazardious to get near the car unless its grounded = earthed = anything els than a car.

well at least thats how i look at this correct me if i'm wrong please :)

Roblab | January 9, 2011

Depends on the panel, but most panels put out 12 volts (probably won't kill you) and around 200 watts. I string mine together for 60 volts, and you definitely feel it, but I'm still here. Also, that's a lot of square feet of panel at around 10 square feet each.
You wouldn't get more than one or two panels' worth on a car. And the ones on my roof are aimed south for more insolation. And, you're right, BIG inverters.
That's the main problem: Even with lots of panel on a car, there's not enough gain to make it worth it.

Discoducky | January 11, 2011

Honestly, all things considered, the chance is near zero, since it's a heavy and frankly, non-elegent solution, to a problem that this car will not face. While it would be totally cool to have on-the-go charging, the tech required to make this feasible in a luxury EV are 10 to 20 years out.

RedRock | September 26, 2011

Imagine towing a trailer that is a 'Solar Lotus', it unfolds to create an area of photovoltaic panels that will charge the Tesla, albeit over 8 hours but you are fully independent.
Alternately there are 'stick-on' photovotaic panels that could be packed into the bonnet trunk and unrolled/unfolded for deployment when required . . . assembled into a tent/garage?

Volker.Berlin | September 27, 2011

The Fisker Karma's solar roof produces 120W max (ideal california sunshine conditions). According to Fisker, that equals about 320 km (200 miles) per year. I have my doubts.

Just to throw in some numbers. Personally, I am still convinced that you can conveniently draw all the power you ever need from your battery. Any EV battery, and particularly those built into Teslas, is designed to propel a car and as such will be almost unaware of whether or not you draw a little extra power in the order of 120W (two light bulbs!). Assuming a 90kWh battery as has been rumored for Tesla's 300-mile Model S, you could draw that kind of power for 750 hours in a row (i.e., an entire month). If you need more than that, e.g., to actively cool the cabin while the car is parked, no solar roof on earth is going to help you with that (at today's technology). But I expect that with the Model S you will be able to sacrifice a little range in exchange for running the HVAC even in park mode, and you will not be constrained by silly 120W.

jkirkebo | September 27, 2011

Hehe, if you want to charge an empty 300-mile Model S in 8 hours you're gonna need at least 16.5kW of panels since you'll not get more than 80% out of them in normal use and the charging efficiency is typically only 85%.

Panels yield about 13 watts per square foot, so you'll end up with 1270 square feet of panels. That is some bad ass trailer needed to fit 67 245W panels in a fold-out configuration :)

Volker.Berlin | September 27, 2011

jkirkebo, and that's assuming that you have 8 hours sunshine straight... ;-)

Timo | September 27, 2011

Gah, using square foot gives me headache. It is very difficult unit for calculations because it isn't SI-unit. (using online conversion...) 1270 square feets is 118 square meters or about 11x11 meter area, 140W/m^2. Sounds a bit optimistic but is not far from right.

Redrock idea is not a new one, I have thought of that quite a few times. For example if you go hiking starting from middle of nowhere you could use such a "tent" to charge up your car while you are hiking. You would need a huge solar panel to do full charge in 8 hours, but if there is several days time then smaller panel becomes useful.

My idea was a car cover made from thin film solar panel. You could cover your car in any parking space in couple of seconds and get much more than from tiny roof solar panel, and in addition would protect your car from environment. Unfortunately such a cover would be quite theft-prone and probably attracts vandalism as well. Too bad that people cannot be trusted.

Nicu | September 27, 2011

Timo, you could make a huge Montgolfier covered in solar thin film that you can use while driving. If the wires are long enough, it doesn't even matter if it's cloudy. Just be careful not to go into any tunnels :D

mwu | September 28, 2011

how about a small trailer that telescopes out a lightning rod for storm charging :P Then all you need is 88Mph and a flux capacitor -- 1.21 Gigawatts! (clock tower not included)

MTriantafelow | September 29, 2011

"how about a small trailer that telescopes out a lightning rod for storm charging :P Then all you need is 88Mph and a flux capacitor -- 1.21 Gigawatts!"

I bet this is Elon's design for the electric plan he keeps mentioning. Just glean some lightening as you fly.

Brian H | September 30, 2011

That would be an electric plane, not plan, I wot!

The new superdupercapbattery membrane should make it all work:

About 2% the cost per kwh of LiIon, apparently. 500,000X the energy density of capacitors. Etc.

Timo | September 30, 2011

You got the cost compared to LiIon wrong though. 10-20% is more like it (10-20Wh/$ vs 2.5Wh/$). Also capacitor comparison was against normal capacitors, not against supercaps. So not quite that good, but still 1/5 the LiIon cost.

However I can't figure out the energy density or even cost of things vs energy content from that (farad is not unit of energy). Maybe whoever did write that did saw a bit more than is writing there.

Brian H | September 30, 2011

Got my numbers crossed; it's more like 12-25% the cost of LiIon. That's not quite so extreme. But still huge.

Brian H | September 30, 2011

hm. The comparison is 1 microfarad cm^2 for caps, vs 0.2 farads for the new material. Total charge transferred at one amp; suggests the voltage difference is proportional. Charge density has to follow, I think. And the cost figure is .72/7 or about 9.7% to "store energy".

Odd selection of numbers, for sure. Maybe it makes perfect Oriental sense in Singapore?? ;)