Some_Guy
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« on: July 31, 2011, 09:23:38 PM » |
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You know those little windmills that kids run around with taht spin when they run: http://i00.i.aliimg.com/photo/v0/380358522/windmill_plastic_kids_toy_windmill_item_windmill.jpgMy idea is to stick dozens or hundred of mini windmills made of plastic or some other durable material in a subway tunnel. As the train passes through the wind generated by the train turns the windmills which generate enough electricity to power the street lights on the surface as well as other things. The point of this idea is to use an already existing infrastructure: newyork city subway tunnels to generate some renewable electricity. Why would this idea work or not work? Oh yeah... copyright or patent or whatever as of today. |
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Austin
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« Reply #1 on: August 01, 2011, 01:36:50 AM » |
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Could it generate electricity? Absolutely. A significant amount? Probably not.
See, these windmills spin so easily because there is virtually no resistance. To generate a significant amount of electricity, you need to add a decent amount of resistance to the blades; it is the act of pushing through that resistance that generates the electricity. If you were to mount pinwheels, for them to spin at all the resistance would have to be tiny, which means the electricity generated would also be tiny. It could conceivably generate enough electricity to power a few lights maybe, but the cost of installation and upkeep would most likely outweigh those gains significantly.
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Big_Daddy
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« Reply #2 on: August 01, 2011, 02:43:17 AM » |
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It would work in the sense that the air motion by the train is otherwise lost. This would allow some recovery of that motion.
But it wouldn't work profitably because the amount of energy you'd get would be pretty small. Since the air at any one point is rarely moving quickly (only when a train is nearby), you'd have to install a large number of these things just to get a small amount of energy. I suspect that if you built it all out, the ongoing maintenance of the rotors and the lines and the control equipment would cost more than the power that was produced.
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L_D
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« Reply #3 on: August 01, 2011, 02:53:04 AM » |
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Think of it properly.If the electric train has to generate electricity for the street you will need to provide the train with electricity to move PLUS a lot extra to export to the street.If the train gets a 100 kw of power and the street gets 200 kw of power so you need to supply 300kw PLUS a bit extra for power loss in transmission.If for some reason like theft of overhead copper power lines you have to do what you suggest you would need to beef up the power and mass of the train 4or 5 times over and probably increase the bore of the underground tunnels.
Good idea only if....
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Devin
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« Reply #4 on: August 01, 2011, 03:22:25 AM » |
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It wouldn't generate much power because the train only drives by every so often. The winds on the streets that are consistently forced between the tall buildings probably carry orders of magnitude more energy throughout a full day.
Small scale energy harvesting is a hot research topic. Most solutions try to use some type of solid state or MEMS solution because small moving parts will degrade quickly and it is not worth the labor costs to replace them. They also are generally used to power something like a mesh network of sensors, not to generate large scale power (not that this isn't possible if you can come up with a solution that is extremely cheap to manufacture, yet has an expected lifetime of many decades).
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hardy
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« Reply #5 on: August 01, 2011, 03:26:26 AM » |
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if it was very efficient you would slow down the trains !
nothing is for free . you would be taking energy from the trains.
you always have to consider the TOTAL system . Consider the energy going into the system ( in this case trains plus windmills ) and energy coming out . You can never get more out than goes in .( conservation of energy law).
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aam641
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« Reply #6 on: August 01, 2011, 03:36:09 AM » |
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This idea would not work.
You are trying to extract energy from air that is being moved by the train. These windmills will only increase the air resistance that the train must overcome, increasing its energy input. Since most trains run on electricity, you would be using electricity to generate wind and then use this wind to generate electricity.
In conclusion, you idea looks like a fancy perpetum mobile, which unfortunately cannot be patented.
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handsome
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« Reply #7 on: August 01, 2011, 03:51:27 AM » |
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In engineering everything is possible, I like the way you think which shows creativity, your idea is good however you need to study the application from economic point of view, also you may amend your idea by combining solar energy with this idea , think about and wish you good luck
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Ray_mond
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« Reply #8 on: August 01, 2011, 04:06:07 AM » |
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All good answers. 100 four inch = 10 centimeter wind turbines per kilometer of subway tunnel could light 100 LEDs at least dimly, each time a train passed plus a few seconds after it passed. They would not be noticeable from the train if there were usual tunnel light, but possibly better than no light at all. The total per kilometer would be perhaps 4 watts, so the train would not be slowed significantly. Subways and tunnels have air vents to the surface, so the LEDs near these may light almost continuously. Somewhat larger wind turbines would also work, but some passengers would be stressed by the reduced clearance. Neil
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