h a l f b a k e r yNot so much a thought experiment as a single neuron misfire.
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This would be a large folding solar array that fits in the trunk of your electric car, used to charge the batteries of the same. It would be built with the latest technology, and it wouldn't be cheap, after all, you just spent $109,000 on that Tesla Roadster, you can't skimp now.
If you're stranded
and can't get to an outlet, you can at least get back on the road in 5 hours or so. Also on extended stays you won't have to waste your breath attempting to convince the hotel manager that charging your car won't significantly impact their electric bill. If you don't drive much you can also save on your own electric bill.
OK, the data is old, but the Sun hasn't got any stronger
http://www.ecotopia...pollo2/pvepbtoz.htm
Do the sums: 1926kWh/m^2/annum, at 100% efficiency gives 96 hours of motoring per annum at 20kW, per metre squared of PV panel. Assume 240 days of commute at one hour each way, you'd need 5 sq metres even at 100% efficiency (current record ~41%). That's a big panel - and what's worse, we all have to move to Australia [AbsintheWithoutLeave, Nov 12 2008]
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Why not build them into the panels of the car so the batteries charge while you're driving and whenever you park? |
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[MB], I don't know, there's a lot of variation between cars. As for the Roadster, Tesla motors is a little secretive on its charger specs, they use relative terms rather than exact specs. |
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[Jim], the array would have to be much smaller, wouldn't work good enough, and would cause a lot of engineering issues. |
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Ok lets do the math. An electric car needs something like 20KW on the motorway. A solar panel will get you about 100W per square meter. So a 10m*10m array would give you 10KW and would charge your car about half as fast as you'd get through it. Not too bad. |
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Of course there is the issue of whether people will let you use up that much real estate just to charge your car. But you could do it out of town. On a sunny day. |
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The Tesla also has regen braking. Of course this is all moot if your parking lot or parking garage has plugs for electric cars. Very few do. |
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I was thinking more about semi-rural areas (and your driveway) where there would be much more chance of ending up stranded, and more open space for your array, just pull over somewhere. |
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Of course there exist places in the city with mostly empty space, graveyards for instance. |
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//The Tesla also has regen braking//
Not much use on a motorway.
//cost of the array will be substantial, however. //
Also the weight. |
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I'm working on a Solar race car at uni. The best have triple junction GaAs cells, which give around 35% efficiency. Given 1kW per m2 on a sunny day (preferably in Australia or similarly well radiated country), these cells over a 6m2 area are capable of powering solar race cars to cruise at about 40mph for about 8 hours (also charging every last drop in the morning and evenings by propping up the bodyshell to point at the sun). |
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Solar race cars are electric cars withuout a plugin that will literally just about carry one person, shaped to be as aerodynamically efficient as possible, while weighing around 200kg running on specially designed low friction tyres and fancy bearings. |
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I would be highly surprised if the Tesla was capable of cruising using twice the energy of these cars, let alone faster. The solar cells are about £30 each for something around 10cm x 10cm, so a cost of around £3000 for each m2 (or 350W/0.35kW at midday) would be a fair bit, or a £30,000 option from the dealer! |
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You'd also have to have a lot of time on your hands, seeing as you'd not be able to move while your fragile foldout charger was running. Call a rescue wagon! |
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To install on your house roof, maybe it would pay for itself in a decade or two, charge while parked fair enough (although you're going to struggle to charge overnight while you're parked at the hotel), but you've got to be real patient and real dumb to get stuck enough times to make use of it as a rescue device! |
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As for weight - that shouldn't be a problem, yes, silicon is a bit like glass, but the cells are very thin and pretty light if they're not mounted on ginormous racks designed for roofs of buildings. |
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Hope this clears things up:
-EXPENSIVE
-Slow
-Light
-Useful if parked in a sunny spot all day if the charging meter is expensive and you're not driving far to get home |
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I wonder how well this would work for an electric motorcycle. Of course you wouldn't be able to take it with you, but it'd make a pretty damn cool carport... |
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Oh and Fraunhofer has now created solar panels with over 40% efficiency. |
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