# How much power from a solar panel on every vehicle? **URL:** \ **Category:** Factual Questions\ **Created:** [June 1, 2011, 2:52am UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924 "2011-06-01T02:52:56Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [June 1, 2011, 2:39pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/21 "2011-06-01T14:39:52Z")
How much extra energy would it take to transport these solar cells while they are collecting the energy? According to the rough calc above it would take around a month to produce the equivalent of 1 gallon of gas. Meanwhile you have been dragging several pounds (?) of extra material in your car for a month, not to mention any aerodynamic effects. ---
**Author:** ![ecoaster](https://avatars.discourse-cdn.com/v4/letter/e/85e7bf/32.png) [@ecoaster](https://boards.straightdope.com/u/ecoaster)\ **Post date:** [June 1, 2011, 3:59pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/22 "2011-06-01T15:59:00Z")
I’ve always wondered why the newest sailboats don’t have solar panels built into their decks…it seems that solar energy captured at sea could be used extremely effectively especially because power outputs are substantially smaller than on land (aside from the primary engine). ---
**Author:** ![Procrustus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/procrustus/32/2994_2.png) [@Procrustus](https://boards.straightdope.com/u/Procrustus)\ **Post date:** [June 1, 2011, 4:17pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/23 "2011-06-01T16:17:33Z")
My Prius has a solar panel on the roof. It operates the A/C on hot days. That’s all it does. I don’t think it generates enough power that they would even bother hooking it up to the batteries to boost the charge. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [June 1, 2011, 4:20pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/24 "2011-06-01T16:20:37Z")
> [@ecoaster](#): > > I’ve always wondered why the newest sailboats don’t have solar panels built into their decks…it seems that solar energy captured at sea could be used extremely effectively especially because power outputs are substantially smaller than on land (aside from the primary engine). What kind of solar panels can withstand salt water and wind and being stomped by sailors? ---
**Author:** ![ecoaster](https://avatars.discourse-cdn.com/v4/letter/e/85e7bf/32.png) [@ecoaster](https://boards.straightdope.com/u/ecoaster)\ **Post date:** [June 1, 2011, 5:01pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/25 "2011-06-01T17:01:26Z")
> [@Sunspace](#): > > What kind of solar panels can withstand salt water and wind and being stomped by sailors? Why can’t solar panels be embedded behind plexiglass? Or they can be added to non-deck areas, see here: [http://c470.jerodisys.com/470pix/47004.htm](http://c470.jerodisys.com/470pix/47004.htm) My guess is this will be standard on many boats at some point ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 1, 2011, 5:35pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/26 "2011-06-01T17:35:09Z")
> [@ecoaster](#): > > I’ve always wondered why the newest sailboats don’t have solar panels built into their decks… **it seems that solar energy captured at sea could be used extremely effectively especially because power outputs are substantially smaller than on land** (aside from the primary engine). [bolding added] I don’t understand what the bolded statement means, but there are several reasons why sailboats are not constructed with solar panels constructed in the deck. For one, decks are working surfaces that the crew is constantly walking over during maneuvering or trimming of the sails, which would require having a transparent polycarbonate cover that will eventually get scratched up and opaque through polymer breakdown. Second, fiberglass decks experience a lot of flexure which would require the mounting of the panels to allow for shear. Third, decks are frequently covered with spray which significantly detracts from theoretical efficiency. Also, when trimmed for a beam reach or higher, much of the deck is in shadow of the sails. Depending on the azimuth of the Sun and the orientation of the boat, the deck may or may not be at an angle of incidence to even effectively generate power. At any given deck angle the deck can only obtain effective angle of incidence for about thirty percent of the solar day. All of this adds up to low efficiencies for deck-mounted solar panels which also add both purchase and maintenance cost to the craft. Now, many cruising yachts–those intended for extended blue water sailing–are outfitted with a solar panel that is generally suspended off and above the transom, which is generally less shaded, and some even have systems that will adjust the angle of the mount to maximize solar incidence (though, as with any complex or sensitive electromechanical device in a marine environment, it will corrode and eventually fail, usually at the most inconvenient time). These are generally used for recharging batteries or powering auxiliary devices without having to use the generator or alternator, and provide only a modest amount of energy. As for the question of the o.p., the issues with it have been adequately addressed. I worked on the Solar Challenge/Sunrayce team at my engineering school for a couple of semesters. The vehicle was essentially a recumbent tricycle frame with a large fairing covered with solar cells. The entire thing could be picked up by two or three students. As a demonstration of engineering ingenuity it was clever, but it was not a remotely practical vehicle. SAAB and GM were at one time working on projects for roof-mounted solar panels to power a cooling fan while the vehicle was parked (similar to the concept mentioned above) but as it has clearly not advanced to being a production option I can only conclude that it was determined to be not appealing or fiscally worthwhile. In general, PV solar power is only practical in large installations, for remote facilities for which connection to a power grid is not practical and energy demands are limited, or as a supplement to existing power supplies. Even then, the ROI is pretty marginal, especially compared to energy efficiency enhancements such as thermal mass storage, high efficiency appliances, and natural convection for cooling. The footprint required to generate enough solar power to be useful Stranger ---
**Author:** ![Larry\_Mudd](https://avatars.discourse-cdn.com/v4/letter/l/f14d63/32.png) [@Larry\_Mudd](https://boards.straightdope.com/u/Larry_Mudd)\ **Post date:** [June 1, 2011, 6:53pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/27 "2011-06-01T18:53:38Z")
A marginally more practical idea would be to [“pave” the roads](http://www.govtech.com/technology/Energy-Ecosystem-of-the-Future.html) with solar panels. Seems kind of a thin margin, though. Intuitively, you’d think that costly, high-tech surfaces would be something you’d try to avoid driving on, and I’d hate to have to deal with road closures for maintenance on the panels. That said, plenty of human progress has been counter to intuition. 🙂 ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [June 1, 2011, 7:17pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/28 "2011-06-01T19:17:52Z")
> [@Try2B\_Comprehensive](#): > > … (how do you do those superscript numbers on here anyway?) … Like this: [noparse]X[sup]2[/sup] or Y[sub]3[/sub][/noparse] makes it look like this: X[sup]2[/sup] or Y[sub]3[/sub] Just think SUPerscript or SUBscript. * * * Solar panels are being developed that are quite flexible and can be shaped to irregular surfaces. Now if only they developed material that was REALLY flexible and could be made into sails… ---
**Author:** ![ecoaster](https://avatars.discourse-cdn.com/v4/letter/e/85e7bf/32.png) [@ecoaster](https://boards.straightdope.com/u/ecoaster)\ **Post date:** [June 1, 2011, 7:46pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/29 "2011-06-01T19:46:32Z")
[quote=“Stranger\_On\_A\_Train, post:26, topic:583924”] [bolding added] I don’t understand what the bolded statement means, but there are several reasons why sailboats are not constructed with solar panels constructed in the deck. I meant that shipboard appliances require less power then their counterparts on land (stove, lights, fridge, etc.) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 1, 2011, 7:58pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/30 "2011-06-01T19:58:37Z")
Quoth **kanicbird** : > [@](#): > > Though the martian rovers are powered by solar, so it’s not entirely out of the question. The Martian rovers are also a lot slower than most people realize. On flat, level ground, with optimum conditions, they can do about 2 inches per second. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [June 1, 2011, 11:40pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/31 "2011-06-01T23:40:07Z")
> [@Chronos](#): > > Quoth **kanicbird** :The Martian rovers are also a lot slower than most people realize. On flat, level ground, with optimum conditions, they can do about 2 inches per second. Not unlike the freeway at rush hour, so I guess that would work. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [June 2, 2011, 12:43am UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/32 "2011-06-02T00:43:18Z")
> [@Procrustus](#): > > My Prius has a solar panel on the roof. It operates the A/C on hot days. That’s all it does. I don’t think it generates enough power that they would even bother hooking it up to the batteries to boost the charge. What type of A/C does that solar panel actually power? I doubt you are talking about a car style of compressor, or even a peltler solid state cooling device, is the Prius A/C a real A/C or just a fan? And if it’s a real A/C how do they get it to work on that small solar panel? ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [June 2, 2011, 3:00am UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/33 "2011-06-02T03:00:21Z")
> [@Try2B\_Comprehensive](#): > > Well, since an ICE is only ~20% efficient and an electric motor is ~95% efficient, wouldn’t we expect electricity to provide about 5 times the transportation as liquid fuel, BTUs being equal? > > If that is the case, then it’s (only) 73.2 hours to the equivalent of a gallon of gas. If it is a lightweight car that gets, say, 73.2 mpg, solar power could provide a mile of transportation for every hour the thing sits out. > And… I thought one could get closer to 250 watts from a square meter of solar panel- in which case it is 29.28 hours/gallon. I guess I don’t know what’s standard. > > I’m trying to get a handle on mental tricks for converting solar power/electricity to gasoline and back. Here’s a solar panel for RV’s that [claims to deliver five amps at 12 volts.](http://www.mrsolar.com/pdf/bp/BP485J.pdf) And here’s a battery page that (if I’m reading it right) seems to indicate that a 1/4 hp trolling motor capable of a steady speed of 3 knots will pull [10 amps](http://www.electricboats.co.uk/batterysize.html) at 12 volts. It looks like it’s going to be a slow trip. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [June 2, 2011, 4:24am UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/34 "2011-06-02T04:24:44Z")
> [@engineer\_comp\_geek](#): > > Sunlight breaks down the chemical bonds inside of the semiconductor material. Instead of re-forming, these bonds instead trap electrons, leaving fewer electrons available for electricity generation. As you end up with more and more “dangling bonds” the solar cell gets less and less efficient. > > Google “Staebler–Wronski effect” for more info. Thank you. ---
**Author:** ![Try2B\_Comprehensive](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/try2b_comprehensive/32/65_2.png) [@Try2B\_Comprehensive](https://boards.straightdope.com/u/Try2B_Comprehensive)\ **Post date:** [June 2, 2011, 5:05am UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/35 "2011-06-02T05:05:32Z")
> [@Ludovic](#): > > How much extra energy would it take to transport these solar cells while they are collecting the energy? According to the rough calc above it would take around a month to produce the equivalent of 1 gallon of gas. Meanwhile you have been dragging several pounds (?) of extra material in your car for a month, not to mention any aerodynamic effects. No, it’s solar film. Their drag effect is negligible. And it would be 1/5 month for a gallon of gas. I’m going for 1 mile per hour in the sun as a minimum of practicality. I bet you could squeeze at least 3 m[sup]2[/sup] onto a Cutlass Supreme… ---
**Author:** ![Try2B\_Comprehensive](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/try2b_comprehensive/32/65_2.png) [@Try2B\_Comprehensive](https://boards.straightdope.com/u/Try2B_Comprehensive)\ **Post date:** [June 2, 2011, 5:07am UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/36 "2011-06-02T05:07:40Z")
> [@kunilou](#): > > Here’s a solar panel for RV’s that [claims to deliver five amps at 12 volts.](http://www.mrsolar.com/pdf/bp/BP485J.pdf) > > And here’s a battery page that (if I’m reading it right) seems to indicate that a 1/4 hp trolling motor capable of a steady speed of 3 knots will pull [10 amps](http://www.electricboats.co.uk/batterysize.html) at 12 volts. > > It looks like it’s going to be a slow trip. The idea isn’t to have it fuel your trip, but rather be the second coming of regenerative braking or something. ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [June 2, 2011, 10:41am UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/37 "2011-06-02T10:41:25Z")
The panel would not have to power the car. A storage bettery might be topped off when the car was not in use, or the range per charge extended. ---
**Author:** ![Try2B\_Comprehensive](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/try2b_comprehensive/32/65_2.png) [@Try2B\_Comprehensive](https://boards.straightdope.com/u/Try2B_Comprehensive)\ **Post date:** [June 2, 2011, 2:19pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/38 "2011-06-02T14:19:53Z")
[This link](http://jalopnik.com/390085/sev-solar-roof-makes-prius-even-more-prius+y) claims the Prius solar roof can provide 20 miles worth of power: > [@](#): > > The entire roof-panel is replaced with these solar cells and can provide 20 miles of electric range as well as upward of 29-percent increased fuel efficiency. This module is capable of fitting 2004 through 2006 Prius models. Watch out, deaf kids! How much power are they talking about? Is this a reliable claim? And if every vehicle in the US had one, how many bbls of oil would be displaced? ---
**Author:** ![Procrustus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/procrustus/32/2994_2.png) [@Procrustus](https://boards.straightdope.com/u/Procrustus)\ **Post date:** [June 11, 2011, 11:32pm UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/39 "2011-06-11T23:32:36Z")
> [@kanicbird](#): > > What type of A/C does that solar panel actually power? I doubt you are talking about a car style of compressor, or even a peltler solid state cooling device, is the Prius A/C a real A/C or just a fan? And if it’s a real A/C how do they get it to work on that small solar panel? Not sure. I thought it was air conditioning, it certainly feels cool and makes a bit more of a noise than I thought a fan would make. Google, however, tells me it’s just “ventilation.” ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [June 12, 2011, 12:24am UTC](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924/40 "2011-06-12T00:24:26Z")
> [@Try2B\_Comprehensive](#): > > [This link](http://jalopnik.com/390085/sev-solar-roof-makes-prius-even-more-prius+y) claims the Prius solar roof can provide 20 miles worth of power: > How much power are they talking about? Is this a reliable claim? And if every vehicle in the US had one, how many bbls of oil would be displaced? You have already been given an answer to this question. This device is no different than the hypothetical one you proposed originally, except perhaps slightly larger. This particular product is an aftermarket device that provides 250 watts in full sun. It only powers the car for “20 miles” if you let it charge for the appropriate amount of time (hours upon hours, or more in anything less than full sun). My post above indicates that such a device, if equipped on all cars, would produce energy equivalent to 1/60th of US gasoline consumption (on average). There is no magic solution to this issue. The sun is just not bright enough to make solar power of the type you’re considering economical or worthwhile. [Previous page](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924.md?page=1) [Next page](https://boards.straightdope.com/t/how-much-power-from-a-solar-panel-on-every-vehicle/583924.md?page=3)