Is generating electricity from subway draft efficient?

  • Context: Undergrad 
  • Thread starter Thread starter Newbie2
  • Start date Start date
  • Tags Tags
    Draft Electricity
Click For Summary

Discussion Overview

The discussion centers around the efficiency of generating electricity from the draft created by subway systems, specifically in the context of a proposal to install wind generators outside subway vents in Seoul. Participants explore the feasibility and implications of this idea, considering both theoretical and practical aspects of power generation in subway environments.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • Some participants question the efficiency of generating power from subway draft, suggesting that it may add resistance to train movement, ultimately requiring more electricity for the motors.
  • Concerns are raised about the potential reduction in ventilation if wind generators are installed, which could necessitate larger vents or additional fans.
  • One participant points out the challenge of harnessing power generated in bursts when trains pass, suggesting that it may be more practical for local equipment like air pollution monitors.
  • Another participant proposes that using the heated air in the subway system could theoretically enhance efficiency through natural convection, although they express skepticism about this idea.
  • There is a suggestion that recovering energy during braking by turning motors into generators is a more viable approach, as this method is already employed by many DC-powered subway trains.
  • One participant proposes that creating larger airways could reduce pressure and allow for more efficient energy generation without compromising train momentum.
  • Concerns are raised about the potential back pressure created by using subway air to drive wind turbines, which could complicate airflow in tunnel conditions.

Areas of Agreement / Disagreement

Participants express a range of views, with no consensus reached on the efficiency or practicality of generating electricity from subway draft. Some participants agree on the challenges and limitations of the proposal, while others suggest alternative methods for energy recovery.

Contextual Notes

Limitations include assumptions about airflow dynamics, the efficiency of energy recovery methods, and the specific design and operational constraints of subway systems.

Newbie2
Messages
1
Reaction score
0
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?
 
Physics news on Phys.org
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.
 
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...
 
Naty1 said:
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.
 
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...
 
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.
 

Similar threads

  • · Replies 74 ·
3
Replies
74
Views
10K
Replies
1
Views
3K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 45 ·
2
Replies
45
Views
14K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 2 ·
Replies
2
Views
8K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 4 ·
Replies
4
Views
3K