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Why isn't a electric road or a overhead third rail a viable alternative to batteries? Batteries - become depleted, are expensive, heavy. With a grid - unlimited

Why isn't a electric road or a overhead third rail a viable alternative to batteries? Batteries - become depleted, are expensive, heavy. With a grid - unlimited range, that can be supplemented by smaller batteries. Are there technical limitations more than cost.

paulsutter 9y ago
The Boring Company has you covered, power supplied by the track: https://www.geek.com/tech/musk-shares-first-image-of-boring-companys-sub-la-tunnel-1721086/ https://www.geek.com/tech/musk-shares-first-image-of-boring-... People are really underestimating the impact of lower cost tunneling.
lcr 9y ago
There is no technical reason why it can't be done[1], it isn't without its challenges though; How would you deal with the fact that roads are used by vehicles with wildly different heights? What about underpasses, is there enough space to fit the overhead wires? You would also need to make sure that vehicles in one place can connect to the grid on other places. It seems like overhead wires will probably be the best solution, but will only be implemented on highways for use on freight vehicles, not on cities or for personal vehicles. Ground level power supply systems also exist[2], but would require you to tear up the entire road network in order to implement them, are expensive, and apparently prone to water clogging (which could perhaps be mitigated) without mentioning the fact that they would probably require either an autonomous or guided vehicle in order to reliably maintain contact with the rail. So, not really, the limitations are mostly about cost and political capital. [1]https://www.siemens.com/global/en/home/products/mobility/road-solutions/electromobility/ehighway.html https://www.siemens.com/global/en/home/products/mobility/roa... [2]http://www.alstom.com/products-services/product-catalogue/rail-systems/Infrastructures/products/aps-ground-level-power-supply/ http://www.alstom.com/products-services/product-catalogue/ra...
- Johnny555 9y ago
  Your first point is already dealt with by electric railroads that run different height trains -- the wires are set at a level that the tallest train can fit under, and shorter trains have a higher pantograph to reach the wires. And since the pantograph is flexible, it can deal with varying wire heights. Gaps in the wire for intersections and underpasses could be handled by having small battery packs in the cars. This also helps with the last-mile -- only large arterial roads need to be electrified and cars could drive the short distance on city streets on battery power. One solution for in-road charging would be wireless inductive chargers like: https://www.cnet.com/roadshow/news/qualcomms-inductive-charging-road-could-change-the-way-we-build-evs/ https://www.cnet.com/roadshow/news/qualcomms-inductive-charg... Though as you say, the real problems are price and politics. In the SF Bay Area, Caltrain has taken decades to get funding for electrification and has faced a lot of resistance from some communities for the construction and visual blight of overhead electrification. And that's just for one set of tracks, electrifying all of the freeways would be much worse.
  - lcr 9y ago
    Well, that was not really my point about height, I was just drawing attention at how ridiculous it would be to see, for example, a sedan (about 1.4 meters tall) connected to an overhead wire that is any where from 2.5 to 3 meters (about the height you would need to be able to pass a swap body) in the air. Like I said, it is technologically possible, but for most intents and purposes seems like a wonky solution, at least for personal vehicles, mass transportation and freight are completely different scenarios. As for the other points, you are right, there are fairly straight forward solutions. Inductive charging is definitely a good option, which has already been explored by transport companies[1]. It again seems to be that politics and money are the main barrier for implementation. [1]http://primove.bombardier.com/products/charging.html http://primove.bombardier.com/products/charging.html
m4x 9y ago
I don't think there are significant technical limitations, it's really just cost and practicality. Trams and busses and trains have been running off overhead lines for a long time, so it clearly works. The main issues are that it doesn't obviously scale up (i.e. it works fine for a few trams, but not necessarily for thousands of cars filled with 1-2 occupants each) and it would be very expensive to roll out widely. Especially for last mile transport, where it basically becomes infeasible. There's just too much road. Essentially, it is a viable alternative, but only where public transport is the major form of transportation. If people are still driving thousands of cars rather than taking the bus then it's impractical.
Kadin 9y ago
It's not impossible, but: 1. It's expensive, and that cost doesn't work out when you have petroleum available as a fuel and can just carry your own energy supply around easily in a small tank under the passenger compartment. It probably still doesn't work out when you have coal, or coal-derived diesel, or vegetable-derived diesel, or "good enough" batteries, available, because those systems are simpler and don't have the funding problems (most of the cost is shifted to the user of the vehicle, which prevents the politically crippling cost of a public system). 2. When you finally designed a system, and standardized the vehicle heights and worked out all the other issues, I suspect you'd have reinvented electric trains. (Or some sort of essentially train-like system, or a system that's not advantageous enough over trains to warrant building it.) Basically it's an idea that's pinched between existing technologies that are good enough in their current forms, and has an extremely high implementation cost. The risk-factored ROI just doesn't appear to be there.

paulsutter 9y ago

The Boring Company has you covered, power supplied by the track: https://www.geek.com/tech/musk-shares-first-image-of-boring-companys-sub-la-tunnel-1721086/ https://www.geek.com/tech/musk-shares-first-image-of-boring-... People are really underestimating the impact of lower cost tunneling.

lcr 9y ago

There is no technical reason why it can't be done[1], it isn't without its challenges though; How would you deal with the fact that roads are used by vehicles with wildly different heights? What about underpasses, is there enough space to fit the overhead wires? You would also need to make sure that vehicles in one place can connect to the grid on other places. It seems like overhead wires will probably be the best solution, but will only be implemented on highways for use on freight vehicles, not on cities or for personal vehicles. Ground level power supply systems also exist[2], but would require you to tear up the entire road network in order to implement them, are expensive, and apparently prone to water clogging (which could perhaps be mitigated) without mentioning the fact that they would probably require either an autonomous or guided vehicle in order to reliably maintain contact with the rail. So, not really, the limitations are mostly about cost and political capital. [1]https://www.siemens.com/global/en/home/products/mobility/road-solutions/electromobility/ehighway.html https://www.siemens.com/global/en/home/products/mobility/roa... [2]http://www.alstom.com/products-services/product-catalogue/rail-systems/Infrastructures/products/aps-ground-level-power-supply/ http://www.alstom.com/products-services/product-catalogue/ra...

Johnny555 9y ago
Your first point is already dealt with by electric railroads that run different height trains -- the wires are set at a level that the tallest train can fit under, and shorter trains have a higher pantograph to reach the wires. And since the pantograph is flexible, it can deal with varying wire heights. Gaps in the wire for intersections and underpasses could be handled by having small battery packs in the cars. This also helps with the last-mile -- only large arterial roads need to be electrified and cars could drive the short distance on city streets on battery power. One solution for in-road charging would be wireless inductive chargers like: https://www.cnet.com/roadshow/news/qualcomms-inductive-charging-road-could-change-the-way-we-build-evs/ https://www.cnet.com/roadshow/news/qualcomms-inductive-charg... Though as you say, the real problems are price and politics. In the SF Bay Area, Caltrain has taken decades to get funding for electrification and has faced a lot of resistance from some communities for the construction and visual blight of overhead electrification. And that's just for one set of tracks, electrifying all of the freeways would be much worse.
- lcr 9y ago
  Well, that was not really my point about height, I was just drawing attention at how ridiculous it would be to see, for example, a sedan (about 1.4 meters tall) connected to an overhead wire that is any where from 2.5 to 3 meters (about the height you would need to be able to pass a swap body) in the air. Like I said, it is technologically possible, but for most intents and purposes seems like a wonky solution, at least for personal vehicles, mass transportation and freight are completely different scenarios. As for the other points, you are right, there are fairly straight forward solutions. Inductive charging is definitely a good option, which has already been explored by transport companies[1]. It again seems to be that politics and money are the main barrier for implementation. [1]http://primove.bombardier.com/products/charging.html http://primove.bombardier.com/products/charging.html

m4x 9y ago

I don't think there are significant technical limitations, it's really just cost and practicality. Trams and busses and trains have been running off overhead lines for a long time, so it clearly works. The main issues are that it doesn't obviously scale up (i.e. it works fine for a few trams, but not necessarily for thousands of cars filled with 1-2 occupants each) and it would be very expensive to roll out widely. Especially for last mile transport, where it basically becomes infeasible. There's just too much road. Essentially, it is a viable alternative, but only where public transport is the major form of transportation. If people are still driving thousands of cars rather than taking the bus then it's impractical.

Kadin 9y ago

It's not impossible, but: 1. It's expensive, and that cost doesn't work out when you have petroleum available as a fuel and can just carry your own energy supply around easily in a small tank under the passenger compartment. It probably still doesn't work out when you have coal, or coal-derived diesel, or vegetable-derived diesel, or "good enough" batteries, available, because those systems are simpler and don't have the funding problems (most of the cost is shifted to the user of the vehicle, which prevents the politically crippling cost of a public system). 2. When you finally designed a system, and standardized the vehicle heights and worked out all the other issues, I suspect you'd have reinvented electric trains. (Or some sort of essentially train-like system, or a system that's not advantageous enough over trains to warrant building it.) Basically it's an idea that's pinched between existing technologies that are good enough in their current forms, and has an extremely high implementation cost. The risk-factored ROI just doesn't appear to be there.