At just flattened at! Posted November 21, 2012 Share Posted November 21, 2012 As I understand it when low pressure is at one end of a tunnel and high pressure at the other, air is blown down it. Is that right? If it is, then why isen't there wind turbines that operate in a tunnel, say starting at sea level and running up the side of a hill or mountain to create the pressure difference at either end? Surely then there would be a constant breeze to blow them and they would be more productive, unlike the ones I always see doing naff all. Link to comment Share on other sites More sharing options...
CaptainPanic Posted November 21, 2012 Share Posted November 21, 2012 As I understand it when low pressure is at one end of a tunnel and high pressure at the other, air is blown down it. Is that right? The air at the high pressure end will go to the low pressure end until the pressure is equal. So, yes, you're right. If it is, then why isen't there wind turbines that operate in a tunnel, say starting at sea level and running up the side of a hill or mountain to create the pressure difference at either end? For the same reason wind does not go vertical. At 10 km above where you are right now, the pressure is very low. The statement you made first is true only for a horizontal situation. The gas itself has a weight, which exerts a pressure downwards because of gravity. This is why there is higher pressure at low altitudes. Surely then there would be a constant breeze to blow them and they would be more productive, unlike the ones I always see doing naff all. You need a chimney effect to achieve this. This does exist, and it is called a solar chimney, or a solar updraft tower. It looks a little different than what you describe, but I hope it is still useful for you. 2 Link to comment Share on other sites More sharing options...
At just flattened at! Posted November 21, 2012 Author Share Posted November 21, 2012 Ah I see, I didn't know such a tower exsisted (even though they've been around since 1900 odd) I'd never thought of gravity pulling on gas either and thats why there was higher pressure at lower levels, learnt something there. I wonder then could an old mine shaft, because of the heat generated down there and the depth, replace the need for the solar panels and be used to power the wind turbine? Ah I see, I didn't know such a tower exsisted (even though they've been around since 1900 odd) I'd never thought of gravity pulling on gas either and thats why there was higher pressure at lower levels, learnt something there. I wonder then could an old mine shaft, because of the heat generated down there and the depth, replace the need for the solar panels and be used to power the wind turbine? Link to comment Share on other sites More sharing options...
InigoMontoya Posted November 21, 2012 Share Posted November 21, 2012 The problem with that idea is "conservation of mass". To pull air out of a mine shaft you have to put some other air *into* the mine shaft. How are you going to do that? It's not a trivial problem. Link to comment Share on other sites More sharing options...
Myuncle Posted November 22, 2012 Share Posted November 22, 2012 Why not building solar chimneys on top of a magma chamber of an active volcano (shutting the chimney from the base during the eruptions of course...)? Link to comment Share on other sites More sharing options...
alpha2cen Posted November 22, 2012 Share Posted November 22, 2012 (edited) As I understand it when low pressure is at one end of a tunnel and high pressure at the other, air is blown down it. Is that right? If it is, then why isen't there wind turbines that operate in a tunnel, say starting at sea level and running up the side of a hill or mountain to create the pressure difference at either end? Surely then there would be a constant breeze to blow them and they would be more productive, unlike the ones I always see doing naff all. This is an answer of your question. It is impossible. The reason is explained in this picture. From Bernoulli equation [latex]\frac{P_{1}}{\varrho_{1} }+gz_{1}+\frac{\delta _{1}0^{2}}{2}=\frac{P_{2}}{\varrho_{2} }+g(z_{1}+h)+\frac{\delta _{2}\Delta v^{2}}{2}+friction factor[/latex] [latex]\varrho _{1}\cong \varrho _{2}=\varrho[/latex] [latex]friction factor=0[/latex] [latex]P_{2}=P_{1}-\varrho gh[/latex] [latex]{ \frac{P_{1}}{\varrho }}+{ gz_{1}}={ \frac{P_{1}}{\varrho }}-{ gh}+{ gz_{1}}+{ gh}+\frac{\delta _{2}\Delta v^{2}}{2}[/latex] [latex]\frac{\delta _{2}\Delta v^{2}}{2}=0[/latex] [latex]\Delta v=0[/latex] No fluid moving happen Edited November 22, 2012 by alpha2cen Link to comment Share on other sites More sharing options...
Enthalpy Posted November 22, 2012 Share Posted November 22, 2012 Somewhat similar but does work, wind turbines have been enclosed in Venturi tunnels again and again. This does provide more power at equal rotor diameter, and a faster rotation speed that benefits the generator. They have no success because - Material cost does matter, not wind area. Longer mast and blades are less expensive than a solid Venturi - thoughalready expensive enough. - Non-solid blades push less in a gale, where they can be stalled or feathered, than a solid Venturi. Link to comment Share on other sites More sharing options...
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