diy solar

diy solar

KiteX Wind Catcher - portable wind turbine

snoobler

snoobler

Solar Honey Badger
Joined
Jul 10, 2020
Messages
8,387
Location
HBR, AZ
Not an endorsement, but this looks very interesting. Of note is the claimed 200W production at 12mph. This is achieved by having a 4.0m diameter rotor with blades only half-span to tip.

kitex.tech

KiteX

Portable wind turbines used off-grid and outdoors. Used with Portable Power Stations and battery generators
kitex.tech

Video of setup on the main page. Claim 15 minutes.

I doubt the durability is fantastic, and there are quite a few typos on the page...
 
So i have always been fascinated by wind energy at smaller levels - (not those dumbass ones out here in West Texas that have never turned a profit and are terrible for the environment) ... seems that really all they have done though is change the blades and made them much longer ... i looked at the stuff available and it just seems gimmicky -- and very expensive ... seriously -- a 200W from China complete runs about $120 ... not sure how simply putting on longer radial blades really does anything ....
 
ghostwriter66 said:
So i have always been fascinated by wind energy at smaller levels - (not those dumbass ones out here in West Texas that have never turned a profit and are terrible for the environment)... seems that really all they have done though is change the blades and made them much longer ... i looked at the stuff available and it just seems gimmicky -- and very expensive ... seriously -- a 200W from China complete runs about $120 ... not sure how simply putting on longer radial blades really does anything ....
Click to expand...

I will let this slide since you're an RF engineer. :p

How does area vary?

By the SQUARE of the diameter?

Yes.

Picture a cylinder of air moving side ways at 10mph. That big slug of air has a kinetic energy (1/2 * m * v^2). That's the absolute maximum amount of energy you could extract from it. It's mass is directly proportional to its area.

6' diameter: pi() * d^2/4 = 28.27sq-ft
13' diameter: pi() * d^2/4 = 132.7sq-ft

That's 4.7X the area, i.e., 4.7X the kinetic energy passing through the projected area of the turbine.

Now, let's not use the inner 6' and just use 6-13': 132.7-28.27 = 104.5 sq-ft - 3.7X

So, the 13' diameter turbine that doesn't use the inner 6' has a swept area that is 3.7X as large as the 6' diameter turbine.

That's 3.7X more energy harvesting potential.

That teeny weeny 200W unit from China is RATED for 200W. It likely won't get anywhere close to that until 20+mph winds depending on rotor diameter.

There's a reason why the big 10+ megawatt wind turbines have blades the length of a football field. They're reaching farther out for more kinetic energy.
 
Last edited by a moderator:
ghostwriter66 said:
... not sure how simply putting on longer radial blades really does anything ....
Click to expand...
To expand on the post above, from Wikipedia: the maximum theoretical power from wind using a turbine blade is: P = π/2 r² v³ * ρ. Where P is power, r the radius, v the wind speed, and ρ the air density. Actual efficiency is usually around 40% of the max. The radius is a squared term, so has a big effect.

ghostwriter66 said:
... i looked at the stuff available and it just seems gimmicky...
Click to expand...
It is, and as we know countries without consumer protection laws are shameless about lying in their datasheets. Then there are the buyers.... even a good turbine is up against buyers with more wishful thinking about the amount of wind they have or maintenance required and become disappointed with reality.

I don't have or use wind, but I'd say it's safe to ignore any wind turbine where the datasheet that shows any power under 8 mph winds or more than 100 watts/m^2 under 15 mph wind speeds. (Unless they've something to backup those claims that seems plausible, e.g., wing tips, and even then I'd wait).
 
Last edited:
snoobler said:
I will let this slide since you're an RF engineer. :p

How does area vary?

By the SQUARE of the diameter?

Yes.

Picture a cylinder of air moving side ways at 10mph. That big slug of air has a kinetic energy (1/2 * m * v^2). That's the absolute maximum amount of energy you could extract from it. It's mass is directly proportional to its area.

6' diameter: pi() * d^2/4 = 28.27sq-ft
13' diameter: pi() * d^2/4 = 132.7sq-ft

That's 4.7X the area, i.e., 4.7X the kinetic energy passing through the projected area of the turbine.

Now, let's not use the inner 6' and just use 6-13': 132.7-28.27 = 104.5 sq-ft - 3.7X

So, the 13' diameter turbine that doesn't use the inner 6' has a swept area that is 3.7X as large as the 6' diameter turbine.

That's 3.7X more energy harvesting potential.

That teeny weeny 200W unit from China is RATED for 200W. It likely won't get anywhere close to that until 20+mph winds depending on rotor diameter.

There's a reason why the big 10+ megawatt wind turbines have blades the length of a football field. They're reaching farther out for more kinetic energy.
Click to expand...

BUT -- it all boils down to the same "engine" .. all they have done is changed the tires from 16" to 33" .. its still the same 200W "generator" you can get from China for $32 ... but this time instead of attaching (5) 1.5m blades they are attaching some long things and charging a ridiculous amount ...

If I am wrong let me know -- I am very curious about wind energy .. but it know that their data sheet -- seems to be on the verge of BEST CASE SCENARIO sprinkled with a little unicorn dust ...
 
  • Like
Reactions: Mia
svetz said:
To expand on the post above, from Wikipedia: the maximum theoretical power from wind using a turbine blade is: P = π/2 r² v³ * ρ. Where P is power, r the radius, v the wind speed, and ρ the air density. Actual efficiency is usually around 40% of the max. The radius is a squared term, so has a big effect.


It is, and as we know countries without consumer protection laws are shameless about lying in their datasheets. Then there are the buyers.... even a good turbine is up against buyers with more wishful thinking about the amount of wind they have or maintenance required and become disappointed with reality.

I don't have or use wind, but I'd say it's safe to ignore any wind turbine where the datasheet that shows any power under 8 mph winds or more than 100 watts/m^2 under 15 mph wind speeds. (Unless they've something to backup those claims that seems plausible, e.g., wing tips, and even then I'd wait).
Click to expand...

I'm with you ... I will wait until Thunderf00t gives it a TU .... https://www.youtube.com/channel/UCmb8hO2ilV9vRa8cilis88A ..
 
KiteX
KiteX claims 50 Watts at 9 mph, so that meets the "no power under 8 mph" test and looks possible (airX gets 25W @ 10 mph and it has 46" diameter). But, what about that 200 watts at 12 mph? Does their trick of increasing the outer blade diameter pay off?

MATH ALERT
We know P = π/2 r² v³ * ρ, so let's make life simple and say everything is constant except for the radius and say a "normal" turbine can get 50W at 12 mph with .58m rotor. Given the same efficiency, what should the KiteX get?

We know P = α π/2 r² v³ * ρ, where α is the real world efficiency.
But to simplify things let's say k = α π/2 v³ * ρ (for a given wind speed they should all be constant).
So that simplifies the math to just P= k r².

So, for the real world turbine, 50 = k (.58)² => k = 50 / .336 = 148.6

Power for the kiteX is the outer minus the inner, so Pnet = α π/2 r2² v³ * ρ - α π/2 r1² v³ * ρ = k r2² - k r1²

The kiteX rotors look to be 1m outer and .5 inner, so...

148.6 x (1² - .5²) = 111.5 watts -- so that's about half the claim on the quickie math; so I'm still dubious.
ghostwriter66 said:
...I'm with you ...
Click to expand...
;)
Well, I can only say I hope you're not wearing this T-shirt:
1617203296087.png​
 
Last edited:
ghostwriter66 said:
BUT -- it all boils down to the same "engine" .. all they have done is changed the tires from 16" to 33" .. its still the same 200W "generator" you can get from China for $32 ... but this time instead of attaching (5) 1.5m blades they are attaching some long things and charging a ridiculous amount ...

If I am wrong let me know -- I am very curious about wind energy .. but it know that their data sheet -- seems to be on the verge of BEST CASE SCENARIO sprinkled with a little unicorn dust ...
Click to expand...
A '200 W' generator will generate more than 200 Watts at very high RPM's - higher RPM -> higher rate at which the magnetic flux changes. The output voltage will increase linearly with RPM. I suspect the 600W version uses some sort of gearing to spin the rotor at very high RPM's. However, the generator may not last as long, due to the increased wear & tear. It may not matter for the market targeted by KiteX.
 
OOPS! The OP said:
snoobler said:
...Of note is the claimed 200W production at 12mph. This is achieved by having a 4.0m diameter rotor with blades only half-span to tip.
Click to expand...

So, that would be a 2m radius instead of 1m (I was using the datasheet, it says: 200W (Windcatcher Lite, 5.5m/s), and lists the rotor diameter as 2m). But... if that's a typo or I misread it and it were a 2m radius... then:

148.6 x (2² - 1²) = 445 watts

So, that does look possible.
 
Last edited:
svetz said:
OOPS! The OP said:


So, that would be a 2m radius instead of 1m (I was using the datasheet, it says: 200W (Windcatcher Lite, 5.5m/s), and lists the rotor diameter as 2m). But... if that's a typo or I misread it and it were a 2m radius... then:

148.6 x (2² - 1²) = 445 watts

So, that does look possible.
Click to expand...

I expect the overall system has low efficiency. Lots of flexibility, and those airfoils do not look high tech.
 

Attachments

  • 1617205178994.png
    1617205178994.png
    141.5 KB · Views: 3
Like they say here at work "EVERYTHING works on a PowerPoint slide" ...

so the price for this looks to be - for the SMALL 200W version - $1167 plus free shipping ...

and $1800 for the 600W version c...

That just seems really high for what you are getting and for what you can get currently off Aliexpress....

They have a few videos showing some technical monitoring "stuff" on the laptop (not sure if its doctored or not -- but be nice if they went old school and showed a voltmeter and an amp meter hooked up directly to the turbine ....

Will be interesting to see where this is in 6 months ...
 
  • Like
Reactions: Mia
ghostwriter66 said:
Like they say here at work "EVERYTHING works on a PowerPoint slide" ...
Click to expand...

It's not like wind turbines are a new technology. The innovation here is lightweight and portable with an absurdly large turbine, which gives it inherent advantages.

ghostwriter66 said:
so the price for this looks to be - for the SMALL 200W version - $1167 plus free shipping ...

and $1800 for the 600W version c...
Click to expand...

I'm looking at spending substantially more for a smaller "typical" wind turbine installation. I wouldn't consider this as a replacement, because I'm certain it's not durable enough for 1) 365/24/7 operation or 2) my location (gusts would kill it during some parts of the year).

You're comparing a complete system that allegedly takes 15 minutes to setup and delivers 200W/12mph (which is huge in the microturbine world, and passes the sanity check) to a $120 option that requires a LOT of additional work and parts with any hope of producing comparable power.

ghostwriter66 said:
That just seems really high for what you are getting and for what you can get currently off Aliexpress....
Click to expand...

You're comparing a buggy with a 1 hp motor to a peddle car.

ghostwriter66 said:
They have a few videos showing some technical monitoring "stuff" on the laptop (not sure if its doctored or not -- but be nice if they went old school and showed a voltmeter and an amp meter hooked up directly to the turbine ....

Will be interesting to see where this is in 6 months ...
Click to expand...

Agreed!

I've encountered at least a handful of posts where RVers are interested in a portable wind turbine. IMHO, if this thing works 1/2 as good as they claim, it's 2X better than any comparably priced option.
 
@ghostwriter66

This may have been mentioned but I didn't see it.

The KiteX unit listed at 600w has a 48v output while most compariable 600w unit are 12v.

Aside from some minor loses, wouldn't that equate the KiteX has 4x the output?
 
bdmartin57 said:
@ghostwriter66

This may have been mentioned but I didn't see it.

The KiteX unit listed at 600w has a 48v output while most compariable 600w unit are 12v.

Aside from some minor loses, wouldn't that equate the KiteX has 4x the output?
Click to expand...

YES(ish) ... going to play with youtube for a bit and see if anyone has done any successful beta testing prior to the kickstarter kicking off ...
 
If you are interested in wind turbines, Paul Gipe's web page is another great resource:
Paul Gipe's Wind Articles

Here's an example of his commentary of one of many fantasy wind turbines:
Mag-Wind Summary and Articles

Info on on the number of blades and why it's important:
Betz: Everything you need to know about wind turbines was written in 1927

Paul links to this good summary on small wind turbines at Treehugger:
Let's Get Real About Cute Little Wind Turbines

Edit - forgot to mention the height of the turbine makes a big difference in wind speed, especially where there are trees or structures nearby (unlike west Texas ;-). Doubling the wind speed provides 8x the available wind power. The Kite X tower does not look very tall.
http://windpower.generatorguide.net/wind-speed-power.html
 
Last edited:
You must log in or register to reply here.

Similar threads

L
Appropriate generator characteristics for small wind turbine
Replies
1
Views
281
Hogheavenfarm
Hogheavenfarm
T
Portable wind turbine system for occasional use (1-3 days of 45-60mph+ high winds)
2
Replies
21
Views
1K
Don B. Cilly
Don B. Cilly
Back
Top