Half a croissant, on a plate, with a sign in front of it saying '50c'
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Electrified Highway

  (+5, -2)
(+5, -2)
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Two electric rails are embedded into the paving in the middle of the slowest highway lane. Suitably equipped trucks can lower a pair of collectors and switch to electric operation over the lenght of the highway.

The rails are rounded and prodrude from the surface of the road by about 5 cm. This allows safe crossing of the lane at about 80 km/h. The rails are insulated from the tarmac with a layer of rubber, which also acts as a shock absorber.

Trucks can easily be retrofitted with an electric motor on each wheel. Electric motors are cheap and have a much higher power/size ratio than a diesel engine, adding little weight to the vehicle. In off-highway diesel operation, the motors act as regenerative brakes.

This scheme would be especially suitable for Europe and Japan, where about 80-90% of land transport is handled by trucks, and where trucks make up a large proportion of traffic on highways. High population densities in these countries also means that highways are in proximity to residential areas, and emissions of NOx and soot from trucks are reduced.

Why not include automobiles in the scheme? a) Retrofitting cars with electric motors is impracticable, and expensive compared to the relatively low cost of a car. b) Embedded rails would be dangerous at speeds exceeding 80 km/h c) Emissions from modern cars are lower than trucks.

This would also somewhat decouple economic growth from oil prices.

But even if the electricity is generated from fossil fuels, it's still an efficient way of tranporting goods. Combined cycle turbines in power plants are 60% efficient (80% when used in co-generation). Tranmission losses are about 10% and the electric motor is about 95% efficient, so overall efficiency is about 50% (cf. typical diesel engine 30%).

kinemojo, Mar 29 2006

Electric Highway http://rpm2.8k.com/car.htm
[ldischler, Mar 29 2006]

Wireless Energy Transfer http://en.wikipedia...ess_energy_transfer
Wikipedia article on wireless energy transfer [talldave, Mar 16 2008]

Wireless Power a Reality http://www.scienced...06/070619183553.htm
Science daily article on an MIT group working on this for homes. [talldave, Mar 16 2008]

Trolleybus http://en.wikipedia.org/wiki/Trolleybus
this idea would work with overhead lines [afinehowdoyoudo, Mar 16 2008]


       First, the thermal to electrical efficiency of the plant isn’t that much better than an efficient gas engine, second, the high voltage that would be required would be terribly dangerous, and third, this isn’t a new idea. (see the link.)
ldischler, Mar 29 2006

       Third-rail railways use 750 V. I don't think that's high enough to bypass rubber tyres. It would only be dangerous to human beings walking across a multilane highway, but that's already terribly dangerous without the rails.
kinemojo, Mar 30 2006

       Cost could be an issue... someone has to pay for the electricity that the trucks are using.
S1, Mar 31 2006

       So, like the little toy racetracks? Cool.
DesertFox, Mar 31 2006

       >>someone has to pay for the electricity that the trucks are using<<   

       Trucks fitted with electric motors would simply pay a surcharge at the toll booth (or though a satellite truck-toll system as used in Germany) depending on a) distance travelled b) combined power of electric motors.
kinemojo, May 03 2006

       There are technologies that can wirelessly transmit power. They involve being within the induction zone of an antenna and being at resonance with the appropriate frequency. I suggest a scheme involving that idea.   

       Like many ideas, this idea would need to be done incrementally. Evolutionary changes where one idea builds on it's predecessor are much more likely to succeed then revolutionary ones, where a system is put in by fiat and no one knows if it will be successful.   

       Start with a charging driveway pad with a wifi connection to verify that you are you (and not someone trying to steal power from your pad).   

       Next, some gas stations could have power stations that could have pads that allow them to charge your credit card while they charge your batteries. You don't even have to get out of your car, just verify on your car's touch screen. (Which, of course, all cars will have by then for GPS and other uses.)   

       Next, some parking lots and parking garages could have special charging pads built into the pavement on select spots.   

       Next some roads could have special short lanes just for charging up while you drive.   

       Finally, if the technology is successful, having highways with full lanes just for charging cars could be the final implementation.
talldave, Mar 16 2008

       Imagine the fireworks if an accident flipped a car onto the rails. Big sparks, exploding gas tanks, wailing & gnashing of teeth all around. Also, 100's of km's of wet roads make a poor resistor.. esp. if de-icing materials like salt or magnesium chloride are present.
afinehowdoyoudo, Mar 16 2008

       According to the Wikipedia 'green vehicle' article, equivalent fuel economy excluding battery costs is 4 to 20 times higher than that including battery costs, so using the electricity directly as suggested here (rather than to charge batteries) might be better.
spidermother, Oct 08 2008

       rain makes this idea completely unworkable. I think a little more thought next time...
WcW, Oct 09 2008

       Why do the rails have to protrude? If they're flush with the surface you can cross them at any speed. If they're slightly recessed, there's less chance of them being shorted out by falling objects.   

       Recessed or protruding rails could also be used as a steering guide, which could be step one in an incremental process.   

       As for charging, trucks already have tachographs with reasonable tamper-proofing - recording the power used seems like an easy addition.   

Srimech, Oct 09 2008

       This could really be an effective technology, if it could be done with an inductive coupling - even one that required an antenna close to the road surface. First locations would be domestic garages, followed by uphill gradients and the exits from intersections - anyplace with frequent high-power demands. Electric range of plug-ins and hybrids would be extended, and consumers would be less inclined to buy a "reserve" of vehicle performance that typically compromises efficiency.
sstvp, Dec 21 2009

       just use overhead wires
sukiyaki, Dec 21 2009

       With overhead wires, you need a sort of device on top of the vehicle to connect to them, like electric trains have. It would be a sort of a yoke for cars. We could call it a car- yoke.
MaxwellBuchanan, Dec 21 2009


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