Well this idea depends on where you live, is there high enough wind speeds in your area?? the biggest factor of output power is the wind speed, so w/o this it is very hard to feasibly build a wind turbine. what diameter is the turbine also?
And what sort of power output are you trying to reach??
[quote]rock27 wrote:
Well this idea depends on where you live, is there high enough wind speeds in your area?? the biggest factor of output power is the wind speed, so w/o this it is very hard to feasibly build a wind turbine. what diameter is the turbine also?
And what sort of power output are you trying to reach??[/quote]
I’m probably going to be dealing with relatively low windspeeds, in the 10-15 mph range. Also I won’t be able to build a high tower for it, it’s gotta be a roof mounted one, But I may be able to eventually do many on my roof.
To be honest, the first couple I will build will just be testing use ones. I want to start out small and just go with it. I don’t want to just use someone else’s design either, that just takes the fun out of it.
I mean it’s a relatively simple concept, you got a windmill to provide rotational energy, and a couple magnets and wires to turn that rotational energy into electrical energy. I just want to play with it to see for myself how what I do impacts the electrical output. Then after a lot of tinkering I may have something I can tap into my home or a battery bank to make the energy useable. Then once I have that I can add additional units, hopefully at a low cost to really up the power generation capabilities of the system.
In reality, I think hooking the system up to the house electrical system is the best way to go. Many power companies will let you run the electric meter in reverse, this way, you are always going to have power even if there is no wind, and any extra you produce in high wind/low energy consumption situations turns your meter backwards thus not wasting any of the energy. Also this eleiminates the need for expensive batteries which have to be replaced every so often when thier life runs out.
V
[quote]Vegita wrote:
Bill Roberts wrote:
I can’t agree: f=ma in either case.
It’s just that one is lousy aerodynamics – like an airplane with a flat plank for a wing – and the other is better aerodynamics.
One is lousy aerodynamics on purpouse. Think of the flat rotor blades like a sail, they want to catch the wind and effectively Tack into it. You are not trying to create pressure differences on one side of the blade from the other, as you are in an airfoil design. You are simply trying to catch the wind energy against a surface, and send the wind one way, and the surface goes the other way.
V[/quote]
I can’t agree with this either: the lousiness of the aerodynamics is not a plus in the case of a ship sailing into the wind either.
(The spinnaker situation would apply to the paddlewheel type design, and indeed there lift is not a factor.)
What you call simply trying “send the wind one way, and the surface goes the other way” is EXACTLY what an airfoil is designed to do, and do more efficiently than a flat surface.
And when you say that a sail, in the case of sailing into the wind (which one might say a windmill is doing) is not “trying to create pressure differences on one side of the blade from the other, as you are in an airfoil design” that is not correct. That pressure difference is what drives the rotation.
As I posted before, f=ma in either case, the aircraft or the windmill. F is also the product of the pressure difference per unit area and the area, in either case.
Same thing, it’s just that the flat or sail surfaces are the more primitive and less efficient shapes accomplishing the exact same purpose by the exact same mechanics.
Oh, and as to why I was making a point of f=ma:
The force generated by the wing is equal to the product of the mass of air accelerated (or as you put it, deflected) by the wing and the acceleration imparted on that mass of air. (Or an integration of individual masses times their individual accelerations.)
And so actually the wing produces lift in the same manner. Ultimately, it is from pushing air away from it with a push equal to the lifting force. Regardless of whether one calls the mechanism the Bernoulli effect or not.
And in either case the pressure is less on the top of the wing, or flat board, or sail, than on the bottom. (Where we define top as being the surface on the side of greater alpha, or angle of incidence.)
So, not a different mechanism, but a question of applying the same mechanism more or less efficiently.
[quote]Bill Roberts wrote:
Vegita wrote:
Bill Roberts wrote:
I can’t agree: f=ma in either case.
It’s just that one is lousy aerodynamics – like an airplane with a flat plank for a wing – and the other is better aerodynamics.
One is lousy aerodynamics on purpouse. Think of the flat rotor blades like a sail, they want to catch the wind and effectively Tack into it. You are not trying to create pressure differences on one side of the blade from the other, as you are in an airfoil design. You are simply trying to catch the wind energy against a surface, and send the wind one way, and the surface goes the other way.
V
I can’t agree with this either: the lousiness of the aerodynamics is not a plus in the case of a ship sailing into the wind either.
(The spinnaker situation would apply to the paddlewheel type design, and indeed there lift is not a factor.)
What you call simply trying “send the wind one way, and the surface goes the other way” is EXACTLY what an airfoil is designed to do, and do more efficiently than a flat surface.
And when you say that a sail, in the case of sailing into the wind (which one might say a windmill is doing) is not “trying to create pressure differences on one side of the blade from the other, as you are in an airfoil design” that is not correct. That pressure difference is what drives the rotation.
As I posted before, f=ma in either case, the aircraft or the windmill. F is also the product of the pressure difference per unit area and the area, in either case.
Same thing, it’s just that the flat or sail surfaces are the more primitive and less efficient shapes accomplishing the exact same purpose by the exact same mechanics.
[/quote]
It’s not the same thing, If you take a flat peice of wood and angle it to the wind, you do not have an airfoil. You have wind hitting a surface at an angle, if the surface was head on, the board would move with the wind, If you andgle it, it will move corresponding to the angle. If you angle it 45 degrees, half of the wind energy will be pusing the board with the wind, the other half of the energy will be pushing it perpendicular to the direction of the wind. The net result would be the board moving in the direction of the angle. If you fix that board to a device which eliminates the ability for the board to move with the wind (a rotor) the board will only move in the perpendicular palne. This is not an airfoil.
An airfoil is a shape. The shape uses aerodynamic properties to produce lift. When a flow of wind passes over an airfoil, due to the shape, the air traveling on one side must travel faster than the air traveling on the other, this creates a difference in pressure on the two sides of the shape. The side where the air has to move farther and thus faster, has a lower pressure than the side which the air moves shorter/slower. Just like a weathersystem, Gasses and liquids move from areas of high pressure to areas of low pressure. The resulting movement of air around the object, provides lift or movement of the whole object from the area of hihg pressure to the area of low pressure. Now since the object is the reason the pressure difference was made in the first place, the airfoil moving moves the difference in pressure along with it, thus the airfoil will keep accelerating in the direction of the low pressure until the total aerodynamic drag of the object equals the force of the pressure diferrences. If you increase the wind speed across the airfoil, you create a bigger difference in pressure and thus the object can move faster against it’s total drag.
So in the first case, you have a force physically pushing the blade, you could turn this type of unit by spraying your hose at it. The other uses aerodynamics to create sideways lift on the blades. You would not be able to spray your hose at the blades and get it to turn.
The first method will catch almost any wind regardless of duration or direction, and spin the device. The second type takes a while of sustained winds to accelerate the blade to a functional speed. If I lived on a hilltop, this would be the best design to use, long periods of sustained wind and one of these could get moving at very good speeds and at those high speeds, you could have a good amount of torque to spin a electric generator.
V
[quote]Vegita wrote:
rock27 wrote:
Well this idea depends on where you live, is there high enough wind speeds in your area?? the biggest factor of output power is the wind speed, so w/o this it is very hard to feasibly build a wind turbine. what diameter is the turbine also?
And what sort of power output are you trying to reach??
I’m probably going to be dealing with relatively low windspeeds, in the 10-15 mph range. Also I won’t be able to build a high tower for it, it’s gotta be a roof mounted one, But I may be able to eventually do many on my roof.
To be honest, the first couple I will build will just be testing use ones. I want to start out small and just go with it. I don’t want to just use someone else’s design either, that just takes the fun out of it.
I mean it’s a relatively simple concept, you got a windmill to provide rotational energy, and a couple magnets and wires to turn that rotational energy into electrical energy. I just want to play with it to see for myself how what I do impacts the electrical output. Then after a lot of tinkering I may have something I can tap into my home or a battery bank to make the energy useable. Then once I have that I can add additional units, hopefully at a low cost to really up the power generation capabilities of the system.
In reality, I think hooking the system up to the house electrical system is the best way to go. Many power companies will let you run the electric meter in reverse, this way, you are always going to have power even if there is no wind, and any extra you produce in high wind/low energy consumption situations turns your meter backwards thus not wasting any of the energy. Also this eleiminates the need for expensive batteries which have to be replaced every so often when thier life runs out.
V[/quote]
Ok, well there are three main factors which must be taken into account, only one of which you can directly influence.
These are wind velocity, cross-sectional area, and the density of the air. There is nothing really you can do for air density so you can treat that as a constant. Wind velocity is a given as you cannot control that. The main problem with wind power generation is the inconsistency in comparison to other methods, i.e. 1 day it could be 2mph, the next it could be 15mph, etc.
So the big factor you have to consider is area. So, ya what you said placing a number of them on your roof is the best option.
Now if this is purely a money saving scheme I would go with a tried and tested simple 3 blade design.
If this is more of a personal experiment start off with a basic design, and add refinements as you see fit…
Best of luck with it.
Another idea would be to use the generator as some sort of large battery charger. The details of this would be more complex, but would be very interesting.
[quote]rock27 wrote:
Vegita wrote:
rock27 wrote:
Well this idea depends on where you live, is there high enough wind speeds in your area?? the biggest factor of output power is the wind speed, so w/o this it is very hard to feasibly build a wind turbine. what diameter is the turbine also?
And what sort of power output are you trying to reach??
I’m probably going to be dealing with relatively low windspeeds, in the 10-15 mph range. Also I won’t be able to build a high tower for it, it’s gotta be a roof mounted one, But I may be able to eventually do many on my roof.
To be honest, the first couple I will build will just be testing use ones. I want to start out small and just go with it. I don’t want to just use someone else’s design either, that just takes the fun out of it.
I mean it’s a relatively simple concept, you got a windmill to provide rotational energy, and a couple magnets and wires to turn that rotational energy into electrical energy. I just want to play with it to see for myself how what I do impacts the electrical output. Then after a lot of tinkering I may have something I can tap into my home or a battery bank to make the energy useable. Then once I have that I can add additional units, hopefully at a low cost to really up the power generation capabilities of the system.
In reality, I think hooking the system up to the house electrical system is the best way to go. Many power companies will let you run the electric meter in reverse, this way, you are always going to have power even if there is no wind, and any extra you produce in high wind/low energy consumption situations turns your meter backwards thus not wasting any of the energy. Also this eleiminates the need for expensive batteries which have to be replaced every so often when thier life runs out.
V
Ok, well there are three main factors which must be taken into account, only one of which you can directly influence.
These are wind velocity, cross-sectional area, and the density of the air. There is nothing really you can do for air density so you can treat that as a constant. Wind velocity is a given as you cannot control that. The main problem with wind power generation is the inconsistency in comparison to other methods, i.e. 1 day it could be 2mph, the next it could be 15mph, etc.
So the big factor you have to consider is area. So, ya what you said placing a number of them on your roof is the best option.
Now if this is purely a money saving scheme I would go with a tried and tested simple 3 blade design.
If this is more of a personal experiment start off with a basic design, and add refinements as you see fit…
Best of luck with it.
Another idea would be to use the generator as some sort of large battery charger. The details of this would be more complex, but would be very interesting.[/quote]
Yea, just to re-hash, The reason i’m not going to go with a 3 blade airfoil design, is because the wind speeds will likley not be strong enough consistantly to provide maximum useage. I need to have a design that will work better at slower less predictable wind speeds. For sure if I lived on a hilltop, I’d put a few 3 blade airfoil types up on poles and let em rip.
V
[quote]Bill Roberts wrote:
Vegita wrote:
Bill Roberts wrote:
I can’t agree: f=ma in either case.
It’s just that one is lousy aerodynamics – like an airplane with a flat plank for a wing – and the other is better aerodynamics.
One is lousy aerodynamics on purpouse. Think of the flat rotor blades like a sail, they want to catch the wind and effectively Tack into it. You are not trying to create pressure differences on one side of the blade from the other, as you are in an airfoil design. You are simply trying to catch the wind energy against a surface, and send the wind one way, and the surface goes the other way.
V
I can’t agree with this either: the lousiness of the aerodynamics is not a plus in the case of a ship sailing into the wind either.
(The spinnaker situation would apply to the paddlewheel type design, and indeed there lift is not a factor.)
What you call simply trying “send the wind one way, and the surface goes the other way” is EXACTLY what an airfoil is designed to do, and do more efficiently than a flat surface.
And when you say that a sail, in the case of sailing into the wind (which one might say a windmill is doing) is not “trying to create pressure differences on one side of the blade from the other, as you are in an airfoil design” that is not correct. That pressure difference is what drives the rotation.
As I posted before, f=ma in either case, the aircraft or the windmill. F is also the product of the pressure difference per unit area and the area, in either case.
Same thing, it’s just that the flat or sail surfaces are the more primitive and less efficient shapes accomplishing the exact same purpose by the exact same mechanics.
[/quote]
We’ll just have to disagree. One deflects air to the side; the other creates faster moving air on one side of the blade as opposed to the other. They both use wind and create a resultant lift, but do so on different principals with different design intent.
I don?t see one as an optimized version of the other because they work through different means and both have their benefits and uses. Most of the large airfoil turbines won?t even run below I think 9-10 MPH winds where more simplistic ?ramp? versions will because they produce more torque on slower wind speeds with lighter blades. So, at lower wind speeds is the ramp version a ?more optimized? version of a sophisticated air foil?
In addition, as you change blade scale you have to remember that the scale of flow boundary layers don?t change (things like relative roughness actually get much larger using smaller versions of the same material). Any one design can only be optimized for very narrow range of specifications.
I think that saying they are evolutions of the same design is like saying sterling engine solar power is an optimized version of solar cell energy. Both have the same driving force (the sun), and both produce electrical power. However, they operate on different principals and on different scales one design works better than the other. The sterling engine generator just doesn?t work on small scales.
Ever notice that birds have wings that are closer to the wings of a plane when insects don?t. Flat wings actually work better than ?teardrop? shaped ones on smaller scales, especially when you factor in things like weight in your design specs.
Which is a more optimized way of pumping liquid, centrifugal or positive displacement? It depends on the situation. One isn?t ?more optimized? than the other. Even though they both turn a rotational force into a driving pressure difference in a liquid.
Even if you throw all that out but you factor in initial cost, less efficient designs can actually be optimization for a given project.
http://www.whalepower.com/drupal/
Check out the applications section, it talks about wind turbines. Pretty neat stuff.
[quote]Vegita wrote:
rock27 wrote:
Well this idea depends on where you live, is there high enough wind speeds in your area?? the biggest factor of output power is the wind speed, so w/o this it is very hard to feasibly build a wind turbine. what diameter is the turbine also?
And what sort of power output are you trying to reach??
I’m probably going to be dealing with relatively low windspeeds, in the 10-15 mph range. Also I won’t be able to build a high tower for it, it’s gotta be a roof mounted one, But I may be able to eventually do many on my roof.
To be honest, the first couple I will build will just be testing use ones. I want to start out small and just go with it. I don’t want to just use someone else’s design either, that just takes the fun out of it.
I mean it’s a relatively simple concept, you got a windmill to provide rotational energy, and a couple magnets and wires to turn that rotational energy into electrical energy. I just want to play with it to see for myself how what I do impacts the electrical output. Then after a lot of tinkering I may have something I can tap into my home or a battery bank to make the energy useable. Then once I have that I can add additional units, hopefully at a low cost to really up the power generation capabilities of the system.
In reality, I think hooking the system up to the house electrical system is the best way to go. Many power companies will let you run the electric meter in reverse, this way, you are always going to have power even if there is no wind, and any extra you produce in high wind/low energy consumption situations turns your meter backwards thus not wasting any of the energy. Also this eleiminates the need for expensive batteries which have to be replaced every so often when thier life runs out.
V[/quote]
Couple of thoughts
Roughly the max power you will get for a circular windmill is
.75r^3v^2
r = radius of blades (in meters)
v = speed of wind (in meters/sec)
This gives you the power in Watts. The larger the blades, the higher the output so bigger is better. But bigger out of wood means it’s heavier so more energy is lost turning the blades. This formula is the max theoretical power again, and if you can get 25% of that you are doing well.
Wind is better higher in the air, so putting it all on a tall tower is a good idea.
Also, the power will be intermittent, viz., only when the wind blows, so you will need some way to store that for later use. Batteries are expensive (you’ll need deep cycle marine ones or you’ll just ruin them) and other options are more expensive, such as flywheels. You’ll also need voltage regulators, oh and the power will probably be DC so you’ll need an inverter to boot or have to buy all DC gadgets. Any gadget more complex than a light bulb or hotplate will probably get fried at some point (gust of wind will do that).
(The power coming out of your wall really is a marvel of stability and availability, btw. Truly an impressive engineering feat… Look at your last power bill and figure out how much energy you are using. It will be pretty sobering I suspect.)
Not saying this isn’t an interesting project or fun, but you will probably find out what everyone else has: Harnessing wind power is pricey compared to what you get. Very pricey. It only makes sense if you are a long way from the grid (so running a line would cost a read fortune) and are willing to be aggravated quite frequently.
And as always, I might just be full of shit…
– jj
[quote]jj-dude wrote:
Vegita wrote:
rock27 wrote:
Well this idea depends on where you live, is there high enough wind speeds in your area?? the biggest factor of output power is the wind speed, so w/o this it is very hard to feasibly build a wind turbine. what diameter is the turbine also?
And what sort of power output are you trying to reach??
I’m probably going to be dealing with relatively low windspeeds, in the 10-15 mph range. Also I won’t be able to build a high tower for it, it’s gotta be a roof mounted one, But I may be able to eventually do many on my roof.
To be honest, the first couple I will build will just be testing use ones. I want to start out small and just go with it. I don’t want to just use someone else’s design either, that just takes the fun out of it.
I mean it’s a relatively simple concept, you got a windmill to provide rotational energy, and a couple magnets and wires to turn that rotational energy into electrical energy. I just want to play with it to see for myself how what I do impacts the electrical output. Then after a lot of tinkering I may have something I can tap into my home or a battery bank to make the energy useable. Then once I have that I can add additional units, hopefully at a low cost to really up the power generation capabilities of the system.
In reality, I think hooking the system up to the house electrical system is the best way to go. Many power companies will let you run the electric meter in reverse, this way, you are always going to have power even if there is no wind, and any extra you produce in high wind/low energy consumption situations turns your meter backwards thus not wasting any of the energy. Also this eleiminates the need for expensive batteries which have to be replaced every so often when thier life runs out.
V
Couple of thoughts
Roughly the max power you will get for a circular windmill is
.75r^3v^2
r = radius of blades (in meters)
v = speed of wind (in meters/sec)
This gives you the power in Watts. The larger the blades, the higher the output so bigger is better. But bigger out of wood means it’s heavier so more energy is lost turning the blades. This formula is the max theoretical power again, and if you can get 25% of that you are doing well.
Wind is better higher in the air, so putting it all on a tall tower is a good idea.
Also, the power will be intermittent, viz., only when the wind blows, so you will need some way to store that for later use. Batteries are expensive (you’ll need deep cycle marine ones or you’ll just ruin them) and other options are more expensive, such as flywheels. You’ll also need voltage regulators, oh and the power will probably be DC so you’ll need an inverter to boot or have to buy all DC gadgets. Any gadget more complex than a light bulb or hotplate will probably get fried at some point (gust of wind will do that).
(The power coming out of your wall really is a marvel of stability and availability, btw. Truly an impressive engineering feat… Look at your last power bill and figure out how much energy you are using. It will be pretty sobering I suspect.)
Not saying this isn’t an interesting project or fun, but you will probably find out what everyone else has: Harnessing wind power is pricey compared to what you get. Very pricey. It only makes sense if you are a long way from the grid (so running a line would cost a read fortune) and are willing to be aggravated quite frequently.
And as always, I might just be full of shit…
– jj[/quote]
I don’t think you are full of shit at all, All of the things you listed are legitimate barriers to harnessing the wind for useable electrical energy. But with will, determination, creativity and enough smarts to understand complex electrical circuits, I think those problems can be engineered away, hopefully in a cost effective manner.
I really wished I had a stream or small river running through my property, I think a water turbine would be much more stable and provide more energy than a wind turbine. But you have to work with what ya got.
V
An easy way to ensure consistent wind speed is to plug in a big fan in front of the turbine to turn it when the wind dies down. May not be cost-effective, but it is effective.
DB
[quote]dollarbill44 wrote:
An easy way to ensure consistent wind speed is to plug in a big fan in front of the turbine to turn it when the wind dies down. May not be cost-effective, but it is effective.
DB[/quote]
That sounds like a government solution to inconstancy in wind power…
[quote]DoubleDuce wrote:
dollarbill44 wrote:
An easy way to ensure consistent wind speed is to plug in a big fan in front of the turbine to turn it when the wind dies down. May not be cost-effective, but it is effective.
DB
That sounds like a government solution to inconstancy in wind power…[/quote]
It’s more like what the wind developers use for their long-term wind studies that they provide to potential lenders.
DB
Vegita, perhaps someone here is a physicist and from that credential can manage to persuade you of what is happening.
[quote]m0dd3r wrote:
http://www.whalepower.com/drupal/
Check out the applications section, it talks about wind turbines. Pretty neat stuff.[/quote]
Interesting concept, Maybe with the addition of these, an airfoil type blade would work in low wind speeds after all! Hmmmmm, just one more thing to test it looks like.
V
[quote]Bill Roberts wrote:
Vegita, perhaps someone here is a physicist and from that credential can manage to persuade you of what is happening regarding flat blades and airfoils and how they turn rotors or windmills.[/quote]
An airfoil can produce lift with a 0 deg. angle of attack, a flat blade cannot.
An airfoil works more by lowering pressure on the top side of the wing where a deflector works more by increasing pressure on the bottom side of it. Essentially one more pushes while the other basically pulls.
They are different concepts with different strengths and weaknesses. It however is not the same thing happening in each concept. (though both concepts will do a little of both assuming a non-zero angle of attack on a flat wing)
Edit: I admittedly have more experience in internal, non-compressable fluid flow.
That is not a different mechanism.
In either case it is pressure differential.
In either case pressure is below ambient above, and above ambient below.
As opposed to that being true for one but not the other.
In either case the force results from, as Vegita put it, “deflecting” (or accelerating) air away from the wing.
As opposed to being true for one but not the other.
With regard to angle of attack: This does not indicate different mechanism. It is also a product of definition. If for example you define alpha relative to the trailing tangent of the upper surface, rather than leading edge to trailing edge – and it’s arbitrary how one defines it, as it is an asymmetrical shape – then the curved surface also provides no positive lift at zero alpha.
But in any case that has nothing to do with differing mechanism, which in either case is generating force by accelerating air away from the wing, opposite to the direction of lift, concurrent with generating a pressure differential between upper and lower surfaces.
[quote]Bill Roberts wrote:
That is not a different mechanism.
In either case it is pressure differential.
In either case pressure is below ambient above, and above ambient below.
As opposed to that being true for one but not the other.
In either case the force results from, as Vegita put it, “deflecting” (or accelerating) air away from the wing.
As opposed to being true for one but not the other.
With regard to angle of attack: This does not indicate different mechanism. It is also a product of definition. If for example you define alpha relative to the trailing tangent of the upper surface, rather than leading edge to tip – and it’s arbitrary how one defines it – then the curved surface also provides no positive lift at zero alpha.
But in any case that has nothing to do with differing mechanism, which in either case is generating force by accelerating air away from the wing, opposite to the direction of lift, concurrent with generating a pressure differential between upper and lower surfaces.
[/quote]
I’m not sure why you are still arguing this, It’s semantics. One works better at higher wind speeds, the other works better at lower wind speeds. That was the main point I tried to make like 30 posts ago.
If you feel like aerodynamic lift is responsible for both blades moving your entitled to. But to say difference in pressure is causing the movement, well shit, difference in pressure causes all movement. When I jump, I exert pressure on the ground, when the pressure is sufficient to overcome the pull of gravity I leave the ground, Yet I am still not an airfoil.
An internal cumbustion engine fires gas and oxygen in a cylender and creates pressure from expanding gas that drives a piston, which drives a crankshaft, which eventually drives wheels. This is not aerodynamic lift, but pressure differences are still responsible for the motion.
V
[quote]Bill Roberts wrote:
That is not a different mechanism.
In either case it is pressure differential.
In either case pressure is below ambient above, and above ambient below.
As opposed to that being true for one but not the other.
In either case the force results from, as Vegita put it, “deflecting” (or accelerating) air away from the wing.
As opposed to being true for one but not the other.
With regard to angle of attack: This does not indicate different mechanism. It is also a product of definition. If for example you define alpha relative to the trailing tangent of the upper surface, rather than leading edge to tip – and it’s arbitrary how one defines it – then the curved surface also provides no positive lift at zero alpha.
But in any case that has nothing to do with differing mechanism, which in either case is generating force by accelerating air away from the wing, opposite to the direction of lift, concurrent with generating a pressure differential between upper and lower surfaces.
[/quote]
In an airfoil the lower side of the wing can be and sometimes is ambient and it still produces lift. With a flat blade the pressure on the top side can be and sometimes is ambient and it still produces lift.
They both deflect air resulting in lift, but one at least mostly pushes air with the lower side of the wing while the other “sucks” it down with the top side.
Further flat blade style windmill can produce torque with the blades stationary and the wind velocity on the top “side” of the “wing” at essentially 0.
The negative pressure on the top side of a flat plate is also a turbulent low pressure zone which is a little different that the laminar flow of a modern air foil.
A parachute is essentially a flat blade wing that produces lift with essentially 0 flow over either side of the wing.