wow this device is sounding promising. The title says residential though, i assume meaning very small scale turbines. Is there any research at the moment into whether this design performs at the full scale level? If it does than these turbines would solve all the problems plaguing wind power today.

70% efficiency? I think not. Since the maximum theoretical efficiency limit is 59%, this machine cannot work. It also looks like a jet engine photoshopped onto a stick. At best, this project is from a very naive designer, at worst it's a scam.

I'm not expert enough to know whether Scruss is right, but it's good to see designers taking a crack at the whip and trying to find solutions. Quieter wind turbines will help with greater adoption. Hey if they're quiet, they're probably more efficient?!

scruss:

Have any science to back your claim?

I'm pretty sure that this IS a jet engine photoshopped onto a stick. The website indicates that the principal (and apparently the only person) in this project has a degree in computer graphics and an interest in aviation propulsion. There is nothing substantive to be gleaned from or even seen at the website, but I hope there is some truth to the promise nonetheless, however unlikely it is that this random dude has somehow managed to overcome every obstacle that wind power engineers have faced for decades.

I think this wind turbine is closer to reality:

http://www.windside.com/

Idea is really simple and I also have seen some of these installed here in Finland.

Maximum theoritical efficiency is 59% do not apply to everything. If this "theory" is the maximum, fighter jet will not reached MACH speed and carry the high payload ( bombs) . The efficiency is increased by the housing. On a regular wind turbine a good percentage of the wind gets blown out to the side after hitting the leading plate of the turbine. In this project, it will hit the leading plate and only goes one way...to the rear. Imagine of you have two stages or more (meaning more rows of blades coupled with stator vanes) This will produce better efficiency as the wind travel only from the front to the rear. The good reason why a jet engine has the most power to weight ratio.
A quiet wind turbine also an indicative that all wind force pushing the blades are absorb and not waste on vibration (which creates the noise ).

The Betz limit (59%) isn't an absolute: for instance it may not apply to Vertical-Axis turbines. So you never know...BUT...

I recognise the background picture on the website (I use it as my wallpaper!!) and the original (flipped here) is copyright to Scottish Power. Were I professionaly presenting a new product, I would not use someone else's material like that. Just a thought.

Apollo,

Your "analogy" to a jet engine does not apply. A lot of jet engines are not very efficient at all. To go fast, they just burn fuel by the ton. More fuel = more speed.

If you want to know more, look up "thrust specific fuel consumption". NASA has a good page explaining this "theory".

FWIW - I agree with scruss.

Also, Alex, have you priced a small turbine these days? How will a product that requires incredible precision to manufacture become affordable to the average "residential" homeowner?

sorry.

I'm a mechanical engineering student at the University of Connecticut and have some math to back up Scruss' claim.

The 59% maximum efficiency number comes from a proof by physicist Albert Betz in his book "Wind Energie" published in 1926, and is known as Betz' Law. In his book, he first proves that the average wind speed through the rotor is the average of the undisturbed wind speed before the turbine (v1) and the wind speed after it passes through the rotor(v2), and that v2 is less than v1 (the wind can't speed up passing through the rotor). The remainder of the proof is as follows:

The mass flow rate of air passing through the rotor is:

m=(p)(A)(v1+v2)/2

where p is the density of the air, A is the swept rotor area, and (v1+v2)/2 is the average wind speed through the rotor.

The power extracted by the rotor can be represented using Newton's second law, F=ma, where F is the force on an object, m is the mass of the object, and a is the acceleration the object experiences. I will not derive this expression, but the end result is the equation for the change in kinetic energy:

P=(1/2)m(v1^2-v2^2)

The equation for the mass flowrate can then be substituted into the above equation, resulting in the following expression:

P=(p/4)(v1^2-v2^2)(v1+v2)A

In order to find the maximum efficiency of a wind turbine we compare the above expression for extracted power to the total power contained in a wind stream without a rotor obstructing the wind, another expression I'll give without deriving because it's secondary to this argument:

Po=A(p/2)v1^3

In the above expression, A is the area of the wind stream, p is the density of the air, v1 is the velocity of the stream, and Po is the total power available in the wind stream.

The ratio between P and Po (the power extracted from the wind and power "available" in the wind, respectively) is the efficiency of the turbine, and can be written as:

(P/Po)=(1/2)(1-(v2/v1)^2)(1+(v2/v1))

To find where this function has a maximum, you can either take its derivative or plot it, but either way you'll see that the function reaches its maximum value when v2/v1=1/3, which, when substituted back into the above expression, gives you the maximum efficiency of 0.59.

This, of course, means that an efficiency of 70% is both ridiculous and impossible, however desireable.
==== author's response follows ===
Thanks for the proof Jim.

The only context I can see the 70% claim as having some validity would be if the design implemented a series of rotors in sequence on a single axis. To handle pressure drop over "Y" axis length, there would be some accomodation in suface area and/or a downward taper in cross sectional area. Adding the accumulated efficiencies moves the net upward no?

The short answer is no. Here's the long answer:
If you look at the equation used to determine the maximum efficiency of the turbine, you can see that there is no reference to the number of blades or rotors, in series or otherwise. The efficiency is a function of the initial and final velocities only, and does not depend on what happens in between the initial and final states. If the velocity of the air leaving the turbine is less than 1/3 the entrance velocity (which would occur if you removed more energy through a series of turbines), the efficiency will decrease.

In addition, the air stream is not only slower, but more turbulent after passing through a wind turbine, and is therefore of "lower quality" for power generation (making it less than ideal for another turbine in series). This is why wind turbines are spaced as they are in wind farms.

I was really hoping this would be a breakthrough, though I suppose it was naive to think suddenly a turbine would just be built out of the blue suffering none of the existing problems. There's more science in the comments here than there is on the turbine's website.

And is it just me or are the shadows on the support and the turbine on opposite sides in the above image?

(crappy diagram exaggerating what I think I'm seeing follows)

C)
I I
I I

A vertical axis wind turbine

http://www.quietrevolution.co.uk/index.htm

I agree w/ those who believe the "photo" is a photoshop creation. Good observation on the shadows, a5y. I hadn't noticed that. I was just too excited about the possible reality of the thing that I didn't look that carefully. Probably what the "designer" is counting on.

Even after this, though, I am hoping that there really is some truth to the claims and that this may indeed become a reality. I guess we'll just have to wait and see.

I'm also somewhat disappointed that Treehugger would post this w/o first doing more research. I know everyone is busy, but, I feel very let-down. Ultimately, though, we are all responsible for doing our own research and watching our own backs. I do appreciate the comments from all of you who are so much more knowledgible than I on this subject. Thanks for helping me to watch my back!

d

Has anyone tried to contact the developer, Mr. J.? His website has some display problems, a bit suspicious for someone with a computer graphics degree. As for the comment on scalability, there are more than engineering problems with more/bigger thinking. I live in a rural area being destroyed by the current generation of 400 foot tall monsters with seven acre footprints that produce a trickle of undependable, grid-destabilizing, tax grabbing power that produces huge profits for venture capitalists. In the final equation, they may produce NO GREENHOUSE GAS BENEFIT!

Whereas, small residential turbines, combined with lifestyle changes, are efficient and DO get people 'off grid' resulting in a real reduction in energy consumption and carbon, sulfur, and nitrogen pollution.

Anonymous gave interesting site on vertical axis wind turbine technology. Very cool looking but very expensive also. This looks more promising than blade turbines - seems it would catch wind from all directions. . . But how much power can it ultimately produce - larger diameter means more output?

It seems to me that all the nit pickers and nae sayers always turn out to be share holders and or employees of petro companys, or other suppliers of un-green energy.

Same thing happens when you walk between 2 buildings on a windy day.....the velocity increases.

http://www.mas.dti.gov.uk/content/resources/categories/newsevents/Stormblade_turbine.html

This is an investment scam. Notice there is no
yaw mechanism at the base of the hub. It is neither a downwind or an up-wind turbine. The website does not identify the nameplate capacity, or anticipated output of the machine. Silly.

I'm the same jim who posted all that math, and I know that this subject is mostly dead, but I'd like to respond to bob:

You're absolutely right that when you say that the wind speed generally increases as you walk between two buildings. A1*V1=A2*V2. Given an initial area and velocity, if the area then decreases, the velocity increases. What's VERY important to realize is that even though the velocity has increased, the total energy in the wind has NOT INCREASED.

This math stuff really isn't part of some great oil company conspiracy (I don't own any oil stock!), it's just simple energy conservation. If you're interested, pick up an undergraduate thermodynamics book and check out control volume analyses. You'll see that you can't arbitrarily create energy simply by changing the shape of a wind turbine (or by doing anything else for that matter!).

It's unfortunate, but there is no easy solution to the energy problem. Hopefully we can sort it all out soon...

== author's response follows ==
transferable wind energy = mass * velocity of flow passing through a given cross sectional area.

If cross sectional area of the turbine is identical on a roof and between two buildings where the flow is faster, guess which location produces more power?

You forgot to include area.

I think there's a misunderstanding. Of course the energy available in a higher velocity wind is higher than the energy available in a lower velocity wind, GIVEN THE SAME AREA. But what happens when you take one flow at a certain velocity and decrease its area? That's what the machine supposedly does, and that's the situation I was referencing. The answer is that the velocity increases, but there is the same amount of energy in the flow.

As far as the buildings go, the wind has the same energy before it is forced between the two buildings as it does after it has been forced through. The area decreases, the wind speed increases, but the wind has the same energy overall. It may be easier to capture the energy when it is more concentrated, but the total amount of energy has not increased. btw, your "energy" equation is actually the momentum equation, and that is also conserved.

If it were possible to create energy by passing a fluid through a nozzle (look up nozzles for more info), we wouldn't have an energy problem.

Your turbine resembles an aviation turbine. I want to know the cut in speed in the inlet. This is another version of vortex wind turbine which has miserably failed in Newziland. I further want to know the efficiency of the machine and the overall efficiency of the turbine. However all the best .

What a unique looking wind turbine. One of the nice features is that you could walk right up to it without loosing a limb unlike traditional wind turbines that have swinging blades.

About 3 weeks ago i thought i had stubbled on to the next generation Wind Generator... then I found Stormblade - He has the right idea but the wrong design. Using Bernoulli's equation of Fluid dynamics this system will work... as the decreased low pressure inside the housing speeds up the air flow as much as 74% in key areas of the the design. This is a flying wing creating low pressure inside. The key is how to harness this power with out impeding the airflow... He has the right idea he just hasn't taken it far enough. As soon a I gain provisional protection I'll show how and why "Dragonfly" will become the next generation Wind Generator producing not only 4 times the energy off of one unit but also able to create energy in no wind at all - sound impossible? Sound like the next big Scam - think again. The science is there IF you know what to look for. So don't be surprised when "Dragonfly" launches and all you who laughed at this concept are pleasantly surprised the next time you power bill is lower because you purchased a home unit. Yes, Dragonfly is Scalable!

About 3 weeks ago i thought i had stubbled on to the next generation Wind Generator... then I found Stormblade - He has the right idea but the wrong design. Using Bernoulli's equation of Fluid dynamics this system will work... as the decreased low pressure inside the housing speeds up the air flow as much as 74% in key areas of the the design. This is a flying wing creating low pressure inside. The key is how to harness this power with out impeding the airflow... He has the right idea he just hasn't taken it far enough. As soon a I gain provisional protection I'll show how and why "Dragonfly" will become the next generation Wind Generator producing not only 4 times the energy off of one unit but also able to create energy in no wind at all - sound impossible? Sound like the next big Scam - think again. The science is there IF you know what to look for. So don't be surprised when "Dragonfly" launches and all you who laughed at this concept are pleasantly surprised the next time you power bill is lower because you purchased a home unit. Yes, Dragonfly is Scalable!

Nowhere is the cost of purchase mentioned. Who can make a deicision without knowing the cost?

alot of critics here - too bad. i might not have a degree in wind and all that high end stuff - more of a layman type. but one thing i do have is many years of being a laminator for sailboats and there isnt much i cant build out of fiberglass. over the past few years i have experimented with rotor turbines and vawt's with mixed results. i think i might give one of these a go and see what happens, whats the worst that can happen and i might just learn something. a few bucks worth of cloth and resin to add a tail assy and medium to high pitch blades might lend to less disturbed airflow. dynamic furling will be the only way to go.
we'll see what happens...