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gruff
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sally_in_wales
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Bernie66
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sally_in_wales
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Milo
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2steps
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Treacodactyl
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dougal
Joined: 15 Jan 2005
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Location: South Kent
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 Posted: Sat Dec 17, 05 4:17 pm Post subject: |
 
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I wondered how long it would be before anyone spotted that!
Its pretty silly from an energy point of view, in almost all locations.
Its pretty expensive for a speed bump.
And the cost doesn't allow for the need to keep trafficlights working when there is little traffic - like at 3am on Sunday morning. Batteries and their controllers are extra. And need looking after.
The company's website refers to it using "waste kinetic energy" from the traffic.
The energy is only being 'wasted' if a vehicle is under braking when it crosses the 'ramp'. Otherwise useful energy is being stolen, and will be replaced by burning more petrol/diesel. And economically its inefficient because the road fuel petrol/diesel is taxed massively more than power station fuel.
The ramp needs to be in a zone where the traffic is slowing - but should never stop, (which would block the ramp). Generally, IMHO, traffic lights don't work like that.
However most motorway exit slip roads *do* work like that. But I'm not keen on the idea of high speed (50/70 mph?) traffic hitting such an obstruction.
I rather think that there might be a considerable road safety issue. Especially when the road surface is slippery.
And the *amount* of energy being generated is *tiny*.
They talk glibly about generating at 5 to 50kW. Firstly that is a rate. And I think that it can only apply during the fraction of a second that a wheel is squeezing the ramp. (A small car engine, like a VW Polo, generates 50kw flat out - imagine a sudden momentary slow down like having 10% of maximum power being applied as reverse thrust - not pleasant or comfortable.)
However, how much of the time is the ramp going to have a wheel crossing it? IMHO much, much less than 1% of 24/7. So instead of generating 5 or 50kw, its *overall* average performance might be 50 watts or so - not enough for 1 light bulb.
If people treat it like a speed bump, slowing down beforehand, crossing gently and then accelerating away - the energy stolen by the ramp will only be a tiny fraction of the energy wasted in slowing down and reaccelerating.
This idea, once examined in detail, seems so daft that it should have been killed before it even got onto the drawing board.
If the energy used to operate traffic lights were significant - which I strongly doubt - then lets have laptop-technology low wattage controllers and LED 'bulbs', and buy in renewably sourced electricity to run them. Much cheaper, much simpler and much better for the environment. |
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Mat S
Joined: 07 Nov 2004
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Location: Leicester
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sally_in_wales
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Rob R
Joined: 28 Oct 2004
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Milo
Joined: 16 May 2005
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Location: Oop North-ish.
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Treacodactyl
Downsizer Moderator
Joined: 28 Oct 2004
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Location: Jumping on the bandwagon of opportunism
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Milo
Joined: 16 May 2005
Posts: 342
Location: Oop North-ish.
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Treacodactyl
Downsizer Moderator
Joined: 28 Oct 2004
Posts: 25795
Location: Jumping on the bandwagon of opportunism
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| Posted: Sun Dec 18, 05 3:42 pm Post subject: |
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| Milo wrote: |
| Well, sokay by me. Driving is a dangerous activity, so traffic calming measures are good, aren't they. |
I'm not that keen on many of them but that's a whole new topic. Having had a speed bump cause a potentially very dangerous failure on my cars suspension, while driving over one at less than 10mph, they are another scheme that penalises everyone rather than the bad drivers IMHO.
| Quote: |
| The energy generated comes from the fuel in the vehicles. Ideas that harness the breaking energy |
| Milo wrote: |
| Or braking? As in slowing down? It's got to be done, hasn't it. Just a question of where really. Perhaps it's quite possible to drive over sensibly located ramps at 30mph in a high gear and accelerate away at the end of a succession of ramps as one would quite normally from a speed hump. |
Where are these humps to be mounted? Near traffic lights where cars will have stopped already and then accelerate over them to drive off? Even if they are sited so that cars hit them at speed most good drivers would slow down before they got to the 'bump' in the road and then drive, i.e. accelerate, over them. That's good driving.
| Quote: |
| and store this to power an electric motor to start the vehicle off again are great ideas provided their extra weight doesn't outweigh their gains. |
| Milo wrote: |
| What extra weight, Treo? (This is getting heavy, dude!). |
To store the extra electricity you would need a larger or additional battery, nip into a garage one day and try and lift one. You would also need a method of converting the energy from kinetic (motion) to electrical so a generator would be required. There are various designs out there if you wish to google. |
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I thought it was a great idea- but I was assuming it would work fairly well as the report said it had been tested and all that. Oh well. I still like the idea of being able to 'claw back' some energy from moving traffic, but do accept the whole laws of physics thing
The energy generated comes from the fuel in the vehicles. Ideas that harness the breaking energy and store this to power an electric motor to start the vehicle off again are great ideas provided their extra weight doesn't outweigh their gains.
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