Is generating electricity from subway draft efficient?

[Newbie2]

I ran across this article from a Korean newspaper. (don't have any link to an English translation of the article)

The subway authorities in Seoul will be testing wind generators that will be placed right outside subway vents.
The idea appears to be that since the enormous draft created by subways end up going out the vents anyway, why not let the draft go through wind generators?

Does this make sense?

 

[mgb_phys]

As a power generation no - you are ultimately adding resistance to the movement of the trains which you will pay back in mor eelectricicty to the motors.
Also by reducing the flow through the vents you reduce the amount of ventilation so will have to either enlarge the ventws or add fans.

It's also difficult to use the power that is generated in bursts when a train goes past.
It might be worth it if you have local equipement (eg weather / air polution monitors) that you need to power but don't want the expense of running power lines to.

 

[Naty1]

does not make sense here...
I agree with mgb..trains move air to make way for their passage...sounds like an unlikely idea, but maybe somebody has a magic solution. Maybe they figure the air is heated in the subway system and therefore natural convection could add some efficiency...I don't believe that myself but it's the only thing I can think of...

It would make a LOT more sense for them to turn their motors into generators when breaking and see if they can recover some power while slowing...

 

[mgb_phys]

It would make a LOT more sense for them to turn their motors into generators when breaking and see if they can recover some power while slowing...

Almost all DC powered subway trains do this. It's not hugely efficent but it solves the bigger problem of what to do with all the energy otherwise. It's hard to cool brakes on a subway train in a tunnel with limited ventilation.

 

[Naty1]

Then it might make sense to make bigger airways and reduce pressure so pushing air would not rob momentum when trains come in for a stop...since that energy is being used to power generators...
sounds like a "cold fusion" idea to me...

 

[pallidin]

I agree. Get the air out of the way. Using that air to drive a wind turbine would create a back pressure in tunnel conditions; effectively causing a higher density air environment.