## ROI/COE Skystream 3.7 vs Selsam Supertwin 2kW vs TU Delft Kite 20kW

Expand Messages
• It s easy to stay away from quantative comparisons for ROI & COE, so lets try it ... A quick comparison of regular wind turbines, and a kite wind turbine.
Message 1 of 29 , Oct 17, 2012
It's easy to stay away from quantative comparisons for ROI & COE, so lets try it ...

A quick comparison of regular wind turbines, and a kite wind turbine.

Assume no maintenance etc costs - to keep things in the ideal world.
That means costs will be higher than shown here.

In the UK, a very good site has an average wind speed of 6 m/s - use this.

Equation (1) : in kWh/year

Energy = output power @avg wind speed * wind factor constant * num hours in yr
= output power @6 m/s * 1.9 * 8766

Assume that the manufacturers 'rated' power output data is the real output we see.

Equation (2): in W

output power for wind speed x =
( cube(x) / cube(rated wind speed) ) * rated output power

So substituting (2) into (1), all we need is the 2 rated values from the manufacturers datasheet, and we have the predicted kWh for the year at our site's average wind speed.

Grid Electricity cost = \$0.20/kWh (retail) (3)

Assume lifetime of a turbine is 10 years.

unit cost \$/kWh = \$initial cost / kwh generated in 10 years (4)

Standard Wind Turbines
----------------------

Benchmark skystream 3.7 Turbine

price = \$12k ready to use
rated wind speed = 13m/s
rated output power = 2400W
(2) = 236W
(1) = 3930 kWh/year
save = \$786/year (3)
Payback = 15.3 years (3)
unit cost = \$0.31/kWh (4)

Benchmark Selsam SuperTwin 2kW Turbine

price = turbine \$3000 + tower \$1000 + alternator \$1000 + inverter/etc \$1000 = \$6k ready to use (guess)
rated wind speed = 14.5m/s (30->35mph)
rated output power = 2000W
(2) = 142W
(1) = 2365 kWh/year
save = \$473/year (3)
Payback = 12.7 years (3)
unit cost = \$0.25/kWh (4)

Kite Wind Turbines
------------------

Of course, not much data here, but looking at TU Delft latest demo, they used 20kw model.

Assume yo-yo gives 50% duty (energy used in retraction) -> really 10kW model = rated output power

They quote 20m/s wind at kite = rated wind speed (they used smaller 14m2 kite because of high wind speed)

There may have to be an altitude benefit added to the power curve (x in equ 2). Haven't seen their power curve.

Obviously - assume the system can reliably and continuously operate for the period.

Benchmark TU Delft 20kW Turbine

price = \$10k ready to use (pure guess at a retail price)
rated wind speed = 20m/s
rated output power = 10kW
(2) = 270W
(1) = 4497 kWh/year
save = \$899/year (3)
Payback = 11.1 years (3)
unit cost = \$0.22/kWh (4)

Feel free to add value (quantative if possible).
• Hey that s a pretty good analysis. Let s put up a SuperTwin(TM), and any other turbine, and a Delfts kite turbine, in the same windfarm-class site. The thing
Message 2 of 29 , Oct 17, 2012
Hey that's a pretty good analysis.
Let's put up a SuperTwin(TM), and any other turbine, and a Delfts kite turbine, in the same windfarm-class site.

The thing to grasp now is, the SuperTwin hes only three moving parts: yaw bearing, which doubles as the furl bearing for overspeed protection, the swinging tail that keeps it all aimed into the wind (or not as windspeeds require), and of course the rotors, driveshafts, and generator, which, together, comprise a "single moving part".

One main key to survival has been shown to be simplicity - less stuff to go wrong, and if it is simple, you have a reasonable chace to get everything right, since the number of failur modes is more limited.

I'd predict, based on experience, that most turbines will fail within the first few weeks, (the first time a truly strong wind comes thru). Most small turbine are unlilkely to survive a year in a good site. The Delfts turbine would operate until the wind dies down and then need human intervention?

--- In AirborneWindEnergy@yahoogroups.com, "dcsoftstuff" <dcsoftstuff@...> wrote:
>
>
> It's easy to stay away from quantative comparisons for ROI & COE, so lets try it ...
>
> A quick comparison of regular wind turbines, and a kite wind turbine.
>
> Assume no maintenance etc costs - to keep things in the ideal world.
> That means costs will be higher than shown here.
>
> In the UK, a very good site has an average wind speed of 6 m/s - use this.
>
> Equation (1) : in kWh/year
>
> Energy = output power @avg wind speed * wind factor constant * num hours in yr
> = output power @6 m/s * 1.9 * 8766
>
>
> Assume that the manufacturers 'rated' power output data is the real output we see.
>
> Equation (2): in W
>
> output power for wind speed x =
> ( cube(x) / cube(rated wind speed) ) * rated output power
>
> So substituting (2) into (1), all we need is the 2 rated values from the manufacturers datasheet, and we have the predicted kWh for the year at our site's average wind speed.
>
>
>
> Grid Electricity cost = \$0.20/kWh (retail) (3)
>
>
> Assume lifetime of a turbine is 10 years.
>
> unit cost \$/kWh = \$initial cost / kwh generated in 10 years (4)
>
>
>
> Standard Wind Turbines
> ----------------------
>
> Benchmark skystream 3.7 Turbine
>
> price = \$12k ready to use
> rated wind speed = 13m/s
> rated output power = 2400W
> (2) = 236W
> (1) = 3930 kWh/year
> save = \$786/year (3)
> Payback = 15.3 years (3)
> unit cost = \$0.31/kWh (4)
>
>
> Benchmark Selsam SuperTwin 2kW Turbine
>
> price = turbine \$3000 + tower \$1000 + alternator \$1000 + inverter/etc \$1000 = \$6k ready to use (guess)
> rated wind speed = 14.5m/s (30->35mph)
> rated output power = 2000W
> (2) = 142W
> (1) = 2365 kWh/year
> save = \$473/year (3)
> Payback = 12.7 years (3)
> unit cost = \$0.25/kWh (4)
>
>
>
> Kite Wind Turbines
> ------------------
>
> Of course, not much data here, but looking at TU Delft latest demo, they used 20kw model.
>
> Assume yo-yo gives 50% duty (energy used in retraction) -> really 10kW model = rated output power
>
> They quote 20m/s wind at kite = rated wind speed (they used smaller 14m2 kite because of high wind speed)
>
> There may have to be an altitude benefit added to the power curve (x in equ 2). Haven't seen their power curve.
>
> Obviously - assume the system can reliably and continuously operate for the period.
>
>
> Benchmark TU Delft 20kW Turbine
>
> price = \$10k ready to use (pure guess at a retail price)
> rated wind speed = 20m/s
> rated output power = 10kW
> (2) = 270W
> (1) = 4497 kWh/year
> save = \$899/year (3)
> Payback = 11.1 years (3)
> unit cost = \$0.22/kWh (4)
>
>
> Feel free to add value (quantative if possible).
>
• Nice first try. The grave flaw is this sort calculation is to begin from a premise that a small AWE research platform, or small HAWT, are proper economic
Message 3 of 29 , Oct 17, 2012
Nice first try.

The grave flaw is this sort calculation is to begin from a premise that a small AWE research platform, or small HAWT, are proper economic models to compare with utility rate electricity. In the AWE case, its like comparing the Wright Flyer with train travel on an economic basis. You can impress Doug, but cannot succeed in predicting modern air travel's dominance over train travel. Its a GIGO set-up.

Try to carefully predict what AWES economy-of-scale will ultimately develop, and them redo this calculation. Another realistic variation would be to calculate from the COE of an experimental small HAWT of the 70's, adjusted for inflation, and then compare with the TUDelft demonstrator. High O&M costs must be part of the calculation, with conventional wind favored.

In more realistic estimates, AWE looks a far better, with average industry-predicted paybacks* of around 2 years. Makani needs about 5 years, and low-complexity "rag and string" concepts as little as a few months, but with the cheap sails recycled often. Kite hybrid legacy plants may beat all other AWE economic models, since a legacy plant is often already paid-off.

Early ROI is critically dependent on energy market pricing and wind resource convergence, with specific places like Hawaii favored.

* These are mostly in-house AWE COE calculations circulating, which vary greatly in quality, and none are really rigorous, even without a prototype-scale cost basis assumption.

• Doug - not much chance of a side by side test off between the 3 at present. The TU Delft kite turbine has only been run for a few hours so far, but eventually
Message 4 of 29 , Oct 17, 2012
Doug - not much chance of a side by side test off between the 3 at present. The TU Delft kite turbine has only been run for a few hours so far, but eventually it will happen as products come to market (with an automated launch and park).
Do you have any user data from your systems ?
It will be interesting to see the relative performance of tower vs kite wind turbines.

Dave - perhaps you didn't understand the analysis, it's based on real data of real systems that are in use today.
The figures are a good approximation of their performance.
Happy to see any real data that you have, especially the measured power curves of the systems you are talking about.

There's no chance of a 2 year payback on any system - don't believe all the sales blurb they give you.
That's just what they say so you'll buy the product.
If the product doesn't exist yet, they can say anything they want ...
• DC wrote perhaps you didn t understand the analysis, it s based on real data of real systems that are in use today. That s the part i really got, that its a
Message 5 of 29 , Oct 17, 2012

DC wrote "perhaps you didn't understand the analysis, it's based on real data of real systems that are in use today."

That's the part i really got, that its a classic GIGO set-up arbitrarily fixated on "real [AWE] systems that are in use today". So you are blithely using a lab mouse (TUDelft AWES) to compare with a sled dog(small turbines) and a draft horse (utility-rates), and hoping the result is somehow revelatory.

DC goes on- "don't believe all the sales blurb they give you. That's just what they say so you'll buy the product."

The many public estimates are not my beliefs, nor do i even "buy" your analytic work product. I hope to know what to believe when it finally happens.

DC "There's no chance of a 2 year payback on any system"

Zero Probability seems impossible to prove, so don't frame or believe such loose statements, but you do make a testable hypothesis against a <2yr payback. All it will take to falsify it is some extended instance of a system that displaces existing auditable portaged diesel or battery costs in a remote setting, like elite science exploration or third-world rural health projects (esp. vaccine refrigeration). A small group of us have an Antarctica AWES pet concept project that seems to "pencil out". So lets wait a few years and see.

DC "Happy to see any real data that you have, especially the measured power curves of the systems you are talking about."

Sorry, but there is no "real data" about megascale AWES systems of the future, and how much economy-of-scale you need to factor in for a valid result. You must be brilliantly creative in your cost-study design to hope to hit the bulls-eye. Persisting in a doomed GIGO process is not desirable. There is a lot of early AWES data out there for you, but you mostly have to DIY mine it. Many of us can help a little. JoeF's archives are the motherlode. Let us know how it goes.

• Dave Couldn t see any data in your reply to support your position. Do you have any ? The thing about giga scale systems is that they are developed from mega
Message 6 of 29 , Oct 18, 2012
Dave

Do you have any ?

The thing about giga scale systems is that they are developed from mega scale systems, which are developed from kilo scale systems, which are developed from ideas.

During the development process, data is collected to access the performance, so that improvements can be made at each stage.

Do you have any data from your development process ?

Derek
• SuperTwin(TM) Data: Paul Gipe s test used 8-foot diameter blades to generate his scatter plot. Now we use longer blades for more swept area and more power. My
Message 7 of 29 , Oct 18, 2012
SuperTwin(TM) Data:
Paul Gipe's test used 8-foot diameter blades to generate his scatter plot. Now we use longer blades for more swept area and more power.
My biggest concern for a few years was to get them to stop burning out generators in 60 mph sustained winds. I had noticed that most serious small wind products involved a lot of returns: Like that Honeywell turbine, they work OK as long as they are not in a wind strong enough to generate any power, so there you have a large contingent of customers dissatisfied because they aren't seeing any return, then the rest who HAVE wind end up returning their turbines for repair a couple times, whereupon the manufacturer (SouthWest Windpower being the example I'm thinking of) takes so long to do the repair and return the turbine, that the customer gives up after two failures.
Now I'm trying out a new inverter that can also protect itself (which is unusual - most inverters "for wind" were designed for solar and are quickly ruined by a wind turbine).
I heard of an entire warehouse, in Arizona, full of burnt-out inverters, ruined by wind turbines. People outside the industry have no idea.
So now I'm out looking at the power output data on the new inverter seeing it exceed 1300 Watts so far in medium winds. We've had calm lately and I'm waiting to get into our windy season here.
Basically I think for the SuperTwin(TM), you're looking at a typical power curve shape, applied from a cut-in at about 6 or 7 MPH, up to around 1500 Watts at 27 mph. Could be higher - we shall see. Everyone agrees after a while that they'd rather have a working turbine, at any power level, then a broken turbine that promised more.
:)

--- In AirborneWindEnergy@yahoogroups.com, "dcsoftstuff" <dcsoftstuff@...> wrote:
>
>
>
>
> Doug - ....
> Do you have any user data from your systems ?
> It will be interesting to see the relative performance of tower vs kite wind turbines.
>
>
> Dave - perhaps you didn't understand the analysis, it's based on real data of real systems that are in use today.
> The figures are a good approximation of their performance.
> Happy to see any real data that you have, especially the measured power curves of the systems you are talking about.
>
> There's no chance of a 2 year payback on any system - don't believe all the sales blurb they give you.
> That's just what they say so you'll buy the product.
> If the product doesn't exist yet, they can say anything they want ...
>
• The 20m/s figure for the TU Delft kite is probably not a rated wind speed, it is the speed the kite travels at when in far slower winds. Even if I am wrong
Message 8 of 29 , Oct 18, 2012
The 20m/s figure for the TU Delft kite is probably not a rated wind
speed, it is the speed the kite travels at when in far slower winds.
Even if I am wrong about the source of that figure, it is a small cost
to use a larger kite. The thing could probably be built to peak at 20kW
in 6m/s winds within the generous budget you have allowed. I therefore
suggested.

You also need to take into account that kites get to higher altitudes
where the winds are stronger.

It has been said by those who should know that a new product needs to be
10 times better than the products already on the market to stand a
chance. Your figures suggest AWE needs to reach \$0.03/kWh to be viable.
You then enter the market at about \$0.2 and use the \$0.17 profit to
cover trouble shooting, returns, legal battles and further development.

Robert.

On Wed, 2012-10-17 at 09:14 +0000, dcsoftstuff wrote:
>
>
> It's easy to stay away from quantative comparisons for ROI & COE, so
> lets try it ...
>
> A quick comparison of regular wind turbines, and a kite wind turbine.
>
> Assume no maintenance etc costs - to keep things in the ideal world.
> That means costs will be higher than shown here.
>
> In the UK, a very good site has an average wind speed of 6 m/s - use
> this.
>
> Equation (1) : in kWh/year
>
> Energy = output power @avg wind speed * wind factor constant * num
> hours in yr
> = output power @6 m/s * 1.9 * 8766
>
> Assume that the manufacturers 'rated' power output data is the real
> output we see.
>
> Equation (2): in W
>
> output power for wind speed x =
> ( cube(x) / cube(rated wind speed) ) * rated output power
>
> So substituting (2) into (1), all we need is the 2 rated values from
> the manufacturers datasheet, and we have the predicted kWh for the
> year at our site's average wind speed.
>
> Grid Electricity cost = \$0.20/kWh (retail) (3)
>
> Assume lifetime of a turbine is 10 years.
>
> unit cost \$/kWh = \$initial cost / kwh generated in 10 years (4)
>
> Standard Wind Turbines
> ----------------------
>
> Benchmark skystream 3.7 Turbine
>
> price = \$12k ready to use
> rated wind speed = 13m/s
> rated output power = 2400W
> (2) = 236W
> (1) = 3930 kWh/year
> save = \$786/year (3)
> Payback = 15.3 years (3)
> unit cost = \$0.31/kWh (4)
>
> Benchmark Selsam SuperTwin 2kW Turbine
>
> price = turbine \$3000 + tower \$1000 + alternator \$1000 + inverter/etc
> \$1000 = \$6k ready to use (guess)
> rated wind speed = 14.5m/s (30->35mph)
> rated output power = 2000W
> (2) = 142W
> (1) = 2365 kWh/year
> save = \$473/year (3)
> Payback = 12.7 years (3)
> unit cost = \$0.25/kWh (4)
>
> Kite Wind Turbines
> ------------------
>
> Of course, not much data here, but looking at TU Delft latest demo,
> they used 20kw model.
>
> Assume yo-yo gives 50% duty (energy used in retraction) -> really 10kW
> model = rated output power
>
> They quote 20m/s wind at kite = rated wind speed (they used smaller
> 14m2 kite because of high wind speed)
>
> There may have to be an altitude benefit added to the power curve (x
> in equ 2). Haven't seen their power curve.
>
> Obviously - assume the system can reliably and continuously operate
> for the period.
>
> Benchmark TU Delft 20kW Turbine
>
> price = \$10k ready to use (pure guess at a retail price)
> rated wind speed = 20m/s
> rated output power = 10kW
> (2) = 270W
> (1) = 4497 kWh/year
> save = \$899/year (3)
> Payback = 11.1 years (3)
> unit cost = \$0.22/kWh (4)
>
> Feel free to add value (quantative if possible).
>
>
• Doug Yes, I used the power curve from Paul Gipe testing at Wulf field to check the data. 1500W @27mph thats a big improvement from approx 1100W before. Just
Message 9 of 29 , Oct 18, 2012
Doug

Yes, I used the power curve from Paul Gipe testing at Wulf field to check the data.

1500W @27mph thats a big improvement from approx 1100W before.

Just out of interest have you ever seen a power curve for a kite based system ?

Derek
• Robert 1) You re probably right about the 20m/s figure, but it s the only figure I get hold of from the limited information in their video on youtube. They
Message 10 of 29 , Oct 18, 2012
Robert

1) You're probably right about the 20m/s figure, but it's the only figure I get hold of from the limited information in their video on youtube. They said the test was in high winds - hence the smaller kite size, so I was also surprised at how small the speed was.

2) Yes, I mentioned that an adjustment would be required for altitude.

3) It would be a lot easier, if they published a power curve. One would imagine that if the curve was so much better than a comparable 20kW tower wind turbine, it is in everyone's interest to see it. Let's see it anyway.

4) 10 times better seems a bit optimistic. I think \$0.03/kWh is about that of the big utility generators.

P.S. Looking forward to another update of how your system is progressing ...

Derek
• Derek,Â  You asked: Couldn t see any data in your reply to support your position.Â Do you have any ? My two key positions are about GIGO calculations and
Message 11 of 29 , Oct 18, 2012
Derek,

Regarding how you could get a specific  more-sound prediction about utility-scale AWE economics, the best "current real [AWES] data" is SkySails ship kites. There are power-curves somewhere, but a single imprecise data-point one finds in SkySails technical claims more or less represents the amount of high-sulphur bunker diesel displaced by throttling back the ship engines in favorable wind, and is about 2MW worth. Savings vary according to ship throttling for cruise. Contact Stephan Brabeck, the CTO, if you need full power curves or more precision about optimal peak power. Most-probable-wind and wind-quarter also count, so pick your assumptions carefully.

Of course solid data about future larger systems is mostly non-existent, so GIGO is an easy trap. You need to apply engineering scaling-laws as best you can. "Econony-of-scale" has its own scale laws to factor in, since your goal is a convincing economic prediction.

Hoping the critique and pointers helps you get a great result. Such calculations are not easy. What data did you rely on to baldly conclude that no AWES will ever achieve a ~two-year payback?

daveS

### Garbage in, garbage out - Wikipedia, the free encyclopedia

en.wikipedia.org/wiki/Garbage_in,_garbage_out
Garbage in, garbage out (abbreviated to GIGO, possibly intended to parallel the phrase first-in, first-out) is a phrase in the field of computer science or ...

### Introduction to Scaling Laws

www.av8n.com/physics/scaling.htm
There are many different scaling laws. At one extreme, there are simple scaling laws that are easy to learn, easy to use, and very useful in everyday life. Scaling ...
• A ten-foot rotor has about 50% more swept area than an eight-foot rotor, and we got a few more years of experience under our belt, so I think an output of 1500
Message 12 of 29 , Oct 18, 2012
A ten-foot rotor has about 50% more swept area than an eight-foot rotor, and we got a few more years of experience under our belt, so I think an output of 1500 Watts at 27 MPH is likely.

Here I sit, broken-hearted, waiting for wind, but it won't get started.

By the way, has anyone ever suspected that Van Halen wrote that song "Broken Hearted" while sitting in the loo? (British for potty)

Certainly we've seen spikes of 2 kW, and the generator itself could easily put out 5 kW or more in short bursts, since we had a truck-mounted SuperTurbine(R) demo for NREL at Windpower 2007 that hit 5000 Watts in front of the Staples Center at around 40-something MPH into a light headwind with four (4) 5-foot 1x4's from Home Depot carved into rotors, and a stack of laminations for the stator only 2/3rds as thick as the stack we are currently using. (thinner generator).

The only power curves I've seen for kites are Makani-style and kite-puller data showing big spikes as the kite goes through its motions. I think... I don't remember exactly what data I've seen from the kites really, just that I've seen a lot more impressive data elsewhere - just sayin'...
:)

--- In AirborneWindEnergy@yahoogroups.com, "dcsoftstuff" <dcsoftstuff@...> wrote:
>
>
> Doug
>
> Yes, I used the power curve from Paul Gipe testing at Wulf field to check the data.
>
> 1500W @27mph thats a big improvement from approx 1100W before.
>
> Just out of interest have you ever seen a power curve for a kite based system ?
>
> Derek
>
• Dear Professor Potty The purpose of this forum is working out how to concentrate the vast energy resource overhead into wires. so when you say... *A ten-foot
Message 13 of 29 , Oct 18, 2012
Dear Professor Potty

The purpose of this forum is working out how to concentrate the vast energy resource overhead into wires.
so when you say...
A ten-foot rotor has about 50% more swept area than an eight-foot rotor, and we got a few more years of experience under our belt, so I think an output of 1500 Watts at 27 MPH is likely.
what's a thousand foot (no sorry even we ditched the imperial measures) 1000 meter collector going to do?

The lavatory (English for cludgie or bog) is a phenomenal resource for mind power, As is sticking your tounge out to the side when you concentrate.
If you have an old style wild west outhouse, take the tin roof off one night, sit, stick your tongue out, look up and imagine.

I'm real worried now that you liked my test.
Terrified.

On 18 October 2012 19:17, Doug <doug@...> wrote:
Â

A ten-foot rotor has about 50% more swept area than an eight-foot rotor, and we got a few more years of experience under our belt, so I think an output of 1500 Watts at 27 MPH is likely.

Here I sit, broken-hearted, waiting for wind, but it won't get started.

By the way, has anyone ever suspected that Van Halen wrote that song "Broken Hearted" while sitting in the loo? (British for potty)

Certainly we've seen spikes of 2 kW, and the generator itself could easily put out 5 kW or more in short bursts, since we had a truck-mounted SuperTurbine(R) demo for NREL at Windpower 2007 that hit 5000 Watts in front of the Staples Center at around 40-something MPH into a light headwind with four (4) 5-foot 1x4's from Home Depot carved into rotors, and a stack of laminations for the stator only 2/3rds as thick as the stack we are currently using. (thinner generator).

The only power curves I've seen for kites are Makani-style and kite-puller data showing big spikes as the kite goes through its motions. I think... I don't remember exactly what data I've seen from the kites really, just that I've seen a lot more impressive data elsewhere - just sayin'...

:)

--- In AirborneWindEnergy@yahoogroups.com, "dcsoftstuff" <dcsoftstuff@...> wrote:
>
>
> Doug
>
> Yes, I used the power curve from Paul Gipe testing at Wulf field to check the data.
>
> 1500W @27mph thats a big improvement from approx 1100W before.
>
> Just out of interest have you ever seen a power curve for a kite based system ?
>
> Derek
>

• See Windlift testing - 12 sq. m. wing where kite is 12 mÂ² and wind is 10 m/s,power being something like 5 kW during power stroke. PierreB ... See Windlift
Message 14 of 29 , Oct 18, 2012

See Windlift testing - 12 sq. m. wing where kite is 12 m² and wind is 10 m/s,power being something like 5 kW during power stroke.

PierreB

> Message du 18/10/12 19:20
> De : "dcsoftstuff"
> A : AirborneWindEnergy@yahoogroups.com
> Copie à :
> Objet : Re: [AWES] ROI/COE Skystream 3.7 vs Selsam Supertwin 2kW vs TU Delft Kite 20kW
>
>

>
> Robert
>
> 1) You're probably right about the 20m/s figure, but it's the only figure I get hold of from the limited information in their video on youtube. They said the test was in high winds - hence the smaller kite size, so I was also surprised at how small the speed was.
>
> 2) Yes, I mentioned that an adjustment would be required for altitude.
>
> 3) It would be a lot easier, if they published a power curve. One would imagine that if the curve was so much better than a comparable 20kW tower wind turbine, it is in everyone's interest to see it. Let's see it anyway.
>
> 4) 10 times better seems a bit optimistic. I think \$0.03/kWh is about that of the big utility generators.
>
> P.S. Looking forward to another update of how your system is progressing ...
>
> Derek
>
>

• I d estimate 12 sq m of blade would be a 100-foot diameter rotor that would yield 200 kW steady-state
Message 15 of 29 , Oct 19, 2012
I'd estimate 12 sq m of blade would be a 100-foot diameter rotor that would yield 200 kW steady-state

--- In AirborneWindEnergy@yahoogroups.com, Pierre BENHAIEM <pierre.benhaiem@...> wrote:
> See Windlift testing - 12 sq. m. wing where kite is 12 mÃ‚Â² and wind is 10 m/s,power being something like 5 kW during power stroke. PierreB
>
>
>
> > Message du 18/10/12 19:20
> > De : "dcsoftstuff"
> > A : AirborneWindEnergy@yahoogroups.com
> > Copie ÃƒÂ  :
> > Objet : Re: [AWES] ROI/COE Skystream 3.7 vs Selsam Supertwin 2kW vs TU Delft Kite 20kW
> >
> > >
> > Robert
> >
> > 1) You're probably right about the 20m/s figure, but it's the only figure I get hold of from the limited information in their video on youtube. They said the test was in high winds - hence the smaller kite size, so I was also surprised at how small the speed was.
> >
> > 2) Yes, I mentioned that an adjustment would be required for altitude.
> >
> > 3) It would be a lot easier, if they published a power curve. One would imagine that if the curve was so much better than a comparable 20kW tower wind turbine, it is in everyone's interest to see it. Let's see it anyway.
> >
> > 4) 10 times better seems a bit optimistic. I think \$0.03/kWh is about that of the big utility generators.
> >
> > P.S. Looking forward to another update of how your system is progressing ...
> >
> > Derek
> >
> >
>
• 1) EVERY conventional wind turbine has a power curve - wind industry standard metric. It is a plot of power (W) vs wind speed (m/s), showing the rated wind
Message 16 of 29 , Oct 19, 2012
1) EVERY conventional wind turbine has a 'power curve' - wind industry standard metric.
It is a plot of power (W) vs wind speed (m/s), showing the 'rated' wind speed and 'rated' power.

2) When a customer walks into a shop, and says "hey, I like the look of that wind turbine ..."
What's the first question ? -> how much is it.
What's the second question ? -> how much power will it produce for me.
The salesperson looks at the power curve, and asks what the avg wind speed is at the site, and reads off the power.

3) All of the information required to estimate ROI and COE is now at hand using the above equations.

avg wind speed @ customer site
'rated' power @ 'rated' wind speed
system cost

4) The customer suddenly notices a kite based system in the shop, "hey, what's that, how does it compare with the other one ..."
The salesperson says ...

Feel free to change customer to government agency etc

---------------------------------------------------

DaveS - don't worry, you're not alone, lack of data collection is the norm.

---------------------------------------------------

Rod - this forum seems to consist of theorists and developers (sometimes a bit of both). Grand schemes start small.

---------------------------------------------------

Pierre - nice link to windlift video - saw the website and there's a system called model 8
12kW (net) @10m/s with 40m2 kite, approx 100->150m altitude

Benchmark WindLift Model 8

price = \$50k (guess)
rated wind speed = 10m/s
rated output power = 12kW
(2) = 2592W
(1) = 43.2 MWh/year
save = \$8640/year (3)
Payback = 5.8 years (3)
unit cost = \$0.12/kWh (4)

for comparison @ 10kW

Benchmark Bergey Excel 10 horizontal axis wind turbine

price = \$50k
rated wind speed = 11m/s
rated output power = 8.9kW
(2) = 1444W
(1) = 24.1 MWh/year
save = \$4820/year (3)
Payback = 10.4 years (3)
unit cost = \$0.21/kWh (4)

Derek
• Derek, http://www.kitegen.com/en/kiteblog-2/ are forecasting 20 â‚¬/MWh. For significant investments the process is rather more involved than your 3 steps
Message 17 of 29 , Oct 19, 2012
Derek,

http://www.kitegen.com/en/kiteblog-2/
are forecasting 20 â‚¬/MWh.

For significant investments the process is rather more involved than
your 3 steps below suggest. My web page
http://copcutt.me.uk/WindDistribution.html
links to a spreadsheet that goes to the next level of accuracy.

Many turbines do not reach predicted generation levels because of
turbulence. To get the optimum power out of any WECS (wind energy
conversion system) the generator has to be turning at the optimum speed.
If the wind speed or direction is changing faster than the system can
adapt a lot of energy is lost.

Robert.

On Fri, 2012-10-19 at 21:52 +0000, dcsoftstuff wrote:
>
>
> 1) EVERY conventional wind turbine has a 'power curve' - wind industry
> standard metric.
> It is a plot of power (W) vs wind speed (m/s), showing the 'rated'
> wind speed and 'rated' power.
>
> 2) When a customer walks into a shop, and says "hey, I like the look
> of that wind turbine ..."
> What's the first question ? -> how much is it.
> What's the second question ? -> how much power will it produce for me.
> The salesperson looks at the power curve, and asks what the avg wind
> speed is at the site, and reads off the power.
>
> 3) All of the information required to estimate ROI and COE is now at
> hand using the above equations.
>
> avg wind speed @ customer site
> 'rated' power @ 'rated' wind speed
> system cost
>
• Derek, When you state- lack of data collection is the norm , you are not talking about the top AWE players.Â This is not a normal social community; it really
Message 18 of 29 , Oct 19, 2012
Derek,

When you state- "lack of data collection is the norm", you are not talking about the top AWE players. This is not a normal social community; it really is highly science and data-driven. A more accurate statement is-"Obsessive data collection is the norm." "Test, test, test" is our mantra. Foundational data-collection and data-based progress has been quite swift, in my opinion.

These days theorists have many new data-sets available to settle (or pose) many interesting questions. You also have a world of scaling-law data (both engineering and economic) to inform your calculation design. Sorry if it now takes a while to locate the best specialized AWES data for your intended purpose.

That said, some of the data needed for your results to be highly predictive are uncollectable (like data about future energy market pricing). Perhaps you really meant "lack of data (in key narrow areas) is the norm". This admitted lack is not so much a motivation for "worry" as it is the ongoing call to continue collecting data to fill specific remaining gaps in our knowledge,

daveS

PS AWES operations research is a key area of current and pending data collection.
• Robert 1) It is that simple. The power curve is a plot of power vs avg wind speed. see http://www.wind-power-program.com/mean_power_calculation.htm System
Message 19 of 29 , Oct 20, 2012
Robert

1) It is that simple. The 'power curve' is a plot of power vs avg wind speed.
see http://www.wind-power-program.com/mean_power_calculation.htm
System development has to baseline the data collected. this is done using the anemometer.
The real power generated by a system is measured each second, as is the wind speed.
Over a period of time, many readings are taken (raw data), and these are averaged into wind speed bins.
A standard 'power curve' is created using this data.
The distribution calcs have already been done, when you look at the power curve.
The type of analysis (Weibull etc) is normally specified on the power curve.
The salesperson just reads the power value from the power curve - nothing else required.

2) Kitegen - yes they are possibly the furthest forward with current AWE technology. A major 'player' one might say.

Lets look at the data :
The site says 200 off stems (3MW each) producing a total of 600MW.
predicted unit cost = 20euro/MWh = \$0.026/kWh = 2.6c/kWh
\$1.7billion investment.

For reference, Windlift says that their system generates 35kW and produces 12kW (net) power,
taking the whole cycle into account.
So lets use this real data -> we only get 34% of the rated power from a yo-yo system.

Kitegen max energy produced per year = 200 stems * 3MW * 34% * 8766 hours in a year
= 1.79TWh/year
income for year = 1.79G * \$0.026 = \$46.5 million
Payback = \$1.7 billion / \$46.5 million
= 36.6 years

This assumes no downtime, or failures and operating at rated power all of the time for all 200 stems.
Bear in mind that there is currently one prototype system @3MW,
and there is no data for the kWh it produced last year,
but we can say with complete certainty that it was below year 1 of the 36 year payback time.

Derek
• DaveS It s the responsibility of each player to publish data (real and predicted) - including assumptions. The data must conform to a standard, this already
Message 20 of 29 , Oct 20, 2012
DaveS

It's the responsibility of each 'player' to publish data (real and predicted) - including assumptions.
The data must conform to a standard, this already exists for conventional wind turbines.
Comparisons can then be made, there will be winners and losers, just like in the current market.

If a 'player' has a product that is so much better than the conventional competition, wouldn't they publish the real data.

Yet, we can not find this data - are they shy ?

Do you think there could be a link between the lack of investment in AWE, and the lack of proof of concept, because there's no published data to prove it ?

If an investor sees a good thing - they invest.

Start publishing, and the investment comes ...

Derek
• Derek, Kitegen max energy produced per year = 200 stems * 3MW * 34% * 8766 hours in a year. By taking account of capacity factor (for example 40 to 50 % for
Message 21 of 29 , Oct 20, 2012

Derek,

>Kitegen max energy produced per year = 200 stems * 3MW * 34% * 8766 hours in a year.

By taking account of capacity factor (for example 40 to 50 % for AWE,but only 20% to 30% for conventional wind energy) the estimation yet drops,the wind not being always 10 or 15 m/s.

Crosswind Kite Power - Home pages of ESAT gives elements for calculation.The simplified formula is (1/2) (2/27)(kite area in m²)(cubic wind speed)(air density,generally 1.2)(coef of Lift)(Lift/Drag² [kite speed regarding wind speed]) without taking account of losses (time and energy of generator as motor) during recovering phase,without taking account of losses in efficiency due to the irregularity of power within the window of flight (according to my trials and after reading of curves from Makani,Windlift,and others,losses in efficiency are at least 50%).Windlift's videos are excellent because you can hear the variations of sound during both power and partial recovering phases.In some of my videos the variations of power are shown with lighting:see on

http://youtu.be/RE3GEEDd0AI .  Kites are very good collectors (ratio swept area/weight being very high) but weak converters compared with a rotor.

You must also add replacement of kites due to wear and UV,and also the area of land/sea use,by far higher than for wind towers due to the length of tether for all wind directions,and generally reliability requirements.

So AWE is a field with huge possibilities but also much work to make.If kites are chosen for massive production,kites must be both efficient (L/D more than 6),light and UV-resistant.If flygens are chosen,electric tether must be...By soon maybe some commercial niches will be possible,but for massive production it is another story.

A great advantage of AWE is its possible implementation even farshore due to the low moment from loads in tether.For conventional wind energy steps towards great unities for less sea/land use are also a problem,and dismantling after use is expensive.

So my idea is when ROI from AWE will be higher than ROI from existing wind energy,at least for some applications,the market of AWE can open.Another idea is the combination of AWE with ground/sea support.

PierreB

http://flygenkite.com

http://wheelwind.com

> Message du 20/10/12 12:47
> De : "dcsoftstuff"
> A : AirborneWindEnergy@yahoogroups.com
> Copie à :
> Objet : [AWES] Re: ROI/COE Skystream 3.7 vs Selsam Supertwin 2kW vs TU Delft Kite 20kW
>
>

>
>
> Robert
>
> 1) It is that simple. The 'power curve' is a plot of power vs avg wind speed.
> see http://www.wind-power-program.com/mean_power_calculation.htm
> System development has to baseline the data collected. this is done using the anemometer.
> The real power generated by a system is measured each second, as is the wind speed.
> Over a period of time, many readings are taken (raw data), and these are averaged into wind speed bins.
> A standard 'power curve' is created using this data.
> The distribution calcs have already been done, when you look at the power curve.
> The type of analysis (Weibull etc) is normally specified on the power curve.
> The salesperson just reads the power value from the power curve - nothing else required.
>
> 2) Kitegen - yes they are possibly the furthest forward with current AWE technology. A major 'player' one might say.
>
> Lets look at the data :
> The site says 200 off stems (3MW each) producing a total of 600MW.
> predicted unit cost = 20euro/MWh = \$0.026/kWh = 2.6c/kWh
> \$1.7billion investment.
>
> For reference, Windlift says that their system generates 35kW and produces 12kW (net) power,
> taking the whole cycle into account.
> So lets use this real data -> we only get 34% of the rated power from a yo-yo system.
>
> Kitegen max energy produced per year = 200 stems * 3MW * 34% * 8766 hours in a year
> = 1.79TWh/year
> income for year = 1.79G * \$0.026 = \$46.5 million
> Payback = \$1.7 billion / \$46.5 million
> = 36.6 years
>
> This assumes no downtime, or failures and operating at rated power all of the time for all 200 stems.
> Bear in mind that there is currently one prototype system @3MW,
> and there is no data for the kWh it produced last year,
> but we can say with complete certainty that it was below year 1 of the 36 year payback time.
>
> Derek
>
>

• Another Buzzword from the far-away world of wind energy! WECS! I love it!
Message 22 of 29 , Oct 20, 2012
Another Buzzword from the far-away world of wind energy! WECS! I love it!

--- In AirborneWindEnergy@yahoogroups.com, Robert Copcutt <r@...> wrote:
>
> Derek,
>
> http://www.kitegen.com/en/kiteblog-2/
> are forecasting 20 Ã¢Â‚Â¬/MWh.
>
> For significant investments the process is rather more involved than
> your 3 steps below suggest. My web page
> http://copcutt.me.uk/WindDistribution.html
> links to a spreadsheet that goes to the next level of accuracy.
>
> Many turbines do not reach predicted generation levels because of
> turbulence. To get the optimum power out of any WECS (wind energy
> conversion system) the generator has to be turning at the optimum speed.
> If the wind speed or direction is changing faster than the system can
> adapt a lot of energy is lost.
>
> Robert.
>
>
>
>
> On Fri, 2012-10-19 at 21:52 +0000, dcsoftstuff wrote:
> >
> >
> > 1) EVERY conventional wind turbine has a 'power curve' - wind industry
> > standard metric.
> > It is a plot of power (W) vs wind speed (m/s), showing the 'rated'
> > wind speed and 'rated' power.
> >
> > 2) When a customer walks into a shop, and says "hey, I like the look
> > of that wind turbine ..."
> > What's the first question ? -> how much is it.
> > What's the second question ? -> how much power will it produce for me.
> > The salesperson looks at the power curve, and asks what the avg wind
> > speed is at the site, and reads off the power.
> >
> > 3) All of the information required to estimate ROI and COE is now at
> > hand using the above equations.
> >
> > avg wind speed @ customer site
> > 'rated' power @ 'rated' wind speed
> > system cost
> >
>
• I know this probably sounds like a bunch of complete gibberish to the newbies, but there s a big difference between an average wind speed taken over 1-minute
Message 23 of 29 , Oct 20, 2012
I know this probably sounds like a bunch of complete gibberish to the newbies, but there's a big difference between an average wind speed taken over 1-minute intervals, and an average wind speed for a site taken over a whole season or many seasons.

You'll note that utility-scale wind turbines are rated to have a capacity factor of say 30% at an "annual average wind speed" of say 12 MPH. People see that sort of data, and can't wait to see how much power their new turbine makes at a low-wind or no-wind site.

"Well the turbine makes a great output at 12 mph so it should do OK in my neighborhood at 8 MPH, right?" Wrong! The average annual windspeed of 12 mph implies many productive afternoons of 27 MPH, averaged in with 4:00 AM times of complete calm. Little useful power is actually made at 12 mph, and much lower than that, and you're lucky to not be losing power.
:O
Doug S.

--- In AirborneWindEnergy@yahoogroups.com, "dcsoftstuff" <dcsoftstuff@...> wrote:
>
>
>
>
>
> Robert
>
> 1) It is that simple. The 'power curve' is a plot of power vs avg wind speed.
> see http://www.wind-power-program.com/mean_power_calculation.htm
> System development has to baseline the data collected. this is done using the anemometer.
> The real power generated by a system is measured each second, as is the wind speed.
> Over a period of time, many readings are taken (raw data), and these are averaged into wind speed bins.
> A standard 'power curve' is created using this data.
> The distribution calcs have already been done, when you look at the power curve.
> The type of analysis (Weibull etc) is normally specified on the power curve.
> The salesperson just reads the power value from the power curve - nothing else required.
>
>
> 2) Kitegen - yes they are possibly the furthest forward with current AWE technology. A major 'player' one might say.
>
> Lets look at the data :
> The site says 200 off stems (3MW each) producing a total of 600MW.
> predicted unit cost = 20euro/MWh = \$0.026/kWh = 2.6c/kWh
> \$1.7billion investment.
>
> For reference, Windlift says that their system generates 35kW and produces 12kW (net) power,
> taking the whole cycle into account.
> So lets use this real data -> we only get 34% of the rated power from a yo-yo system.
>
> Kitegen max energy produced per year = 200 stems * 3MW * 34% * 8766 hours in a year
> = 1.79TWh/year
> income for year = 1.79G * \$0.026 = \$46.5 million
> Payback = \$1.7 billion / \$46.5 million
> = 36.6 years
>
> This assumes no downtime, or failures and operating at rated power all of the time for all 200 stems.
> Bear in mind that there is currently one prototype system @3MW,
> and there is no data for the kWh it produced last year,
> but we can say with complete certainty that it was below year 1 of the 36 year payback time.
>
>
> Derek
>
• That s four buzzwords from the world of real wind energy now: 1) Betz 2) MPPT 3) WECS 4) Power Curve wait there s more: 5) Weibull Distribution 6) Yoyo? (OK I
Message 24 of 29 , Oct 20, 2012
That's four buzzwords from the world of real wind energy now:
1) Betz
2) MPPT
3) WECS
4) Power Curve
wait there's more:
5) Weibull Distribution
6) Yoyo?
(OK I was joking with that last one)
Yoyo - a term with many meanings...

--- In AirborneWindEnergy@yahoogroups.com, "dcsoftstuff" <dcsoftstuff@...> wrote:
>
>
>
>
>
> Robert
>
> 1) It is that simple. The 'power curve' is a plot of power vs avg wind speed.
> see http://www.wind-power-program.com/mean_power_calculation.htm
> System development has to baseline the data collected. this is done using the anemometer.
> The real power generated by a system is measured each second, as is the wind speed.
> Over a period of time, many readings are taken (raw data), and these are averaged into wind speed bins.
> A standard 'power curve' is created using this data.
> The distribution calcs have already been done, when you look at the power curve.
> The type of analysis (Weibull etc) is normally specified on the power curve.
> The salesperson just reads the power value from the power curve - nothing else required.
>
>
> 2) Kitegen - yes they are possibly the furthest forward with current AWE technology. A major 'player' one might say.
>
> Lets look at the data :
> The site says 200 off stems (3MW each) producing a total of 600MW.
> predicted unit cost = 20euro/MWh = \$0.026/kWh = 2.6c/kWh
> \$1.7billion investment.
>
> For reference, Windlift says that their system generates 35kW and produces 12kW (net) power,
> taking the whole cycle into account.
> So lets use this real data -> we only get 34% of the rated power from a yo-yo system.
>
> Kitegen max energy produced per year = 200 stems * 3MW * 34% * 8766 hours in a year
> = 1.79TWh/year
> income for year = 1.79G * \$0.026 = \$46.5 million
> Payback = \$1.7 billion / \$46.5 million
> = 36.6 years
>
> This assumes no downtime, or failures and operating at rated power all of the time for all 200 stems.
> Bear in mind that there is currently one prototype system @3MW,
> and there is no data for the kWh it produced last year,
> but we can say with complete certainty that it was below year 1 of the 36 year payback time.
>
>
> Derek
>
• Derek, Unlike a seasoned aerospace pro (like David Everett), who is cautious to do the domain homework before making a raft of stark assertions, you prefer to
Message 25 of 29 , Oct 20, 2012
Derek,

Unlike a seasoned aerospace pro (like David Everett), who is cautious to do the domain homework before making a raft of stark assertions, you prefer to jump right in. Thats OK, just don't expect to look as smart.

You wrote-"It's the responsibility of each 'player' to publish data (real and predicted) - including assumptions.
The data must conform to a standard, this already exists for conventional wind turbines."

Then publish your real data, or you are not a player. Just kidding. Its probably too early for you to meet this standard, as it is so many others. The Wright brothers did not start with a DC-3 spec sheet.

When you do test your first prototype-
Will it be optimal? Not at all.
Will it have economies of scale? No.
Will you get every windspeed at your first test sessions for a full power curve? Not likely.
Is wind tunnel data OK? It tends to exaggerate predicted performance in real operation.
Will your prototype O&M costs be realistic? No.

You go on- "Yet, we can not find this data - are they shy ?"

Try just looking harder at the archives or do search for it, or pay a researcher to do it for you. If you are in a hurry, it just makes your GIGO tendencies worse. Note that the AWE academics tend to be open-information, but some "top" VC players are closed, but it would be wrong to presume "shy" VCs only have failure to cover. The investors often impose NDAs.

You continue- "Do you think there could be a link between the lack of investment in AWE, and the lack of proof of concept, because there's no published data to prove it ?"

I think the 200+ millions invested so far is quite reasonable, and am grateful for my tiny share of it. None of us would have investment to do work work with scale prototypes if your "marketer" standards were a realistic model for high-risk experimental R&D.

You also asserted- "Comparisons can then be made, there will be winners and losers, just like in the current market."

Are you saying GIGO predicts winners and losers? These are not likely real "winners and losers, just like in the current market."

You conclude- "Start publishing and the investment comes"

OK, be your own test case. Let us know when your growing published results get you investment and what sound conclusions to draw from that data-point,

daveS

PS Don't get discouraged by the "brick-wall" difficulties in your initial approach to AWE. Try getting out and flying kites, maybe take some flying lessons, get your MBA, etc., while you gather power-curves from obscure web pages :)

• PierreB Good spot, I didn t quantify the capacity factor. Where does your 50% factor come from ? I m familiar with the 25- 35% for conventional wind turbines.
Message 26 of 29 , Oct 20, 2012
PierreB

Good spot, I didn't quantify the capacity factor.

Where does your 50% factor come from ? I'm familiar with the 25->35% for conventional wind turbines.
That's data you've measured yourself ?

Any chance you can do the other calculation (ESAT), and compare with this one.
Not sure whether there's sufficent information from kitegen for you to do that.

Trying to keep the calculations simple, I know they'll present a rather rosy picture (or maybe not - see below),
but factoring replacements. downtime, maintenance etc is complex,
and the main point is to benchmark different systems against each other for comparison.

Assuming 50% factor :

Kitegen max energy produced per year = 200 stems * 3MW * 34% * 50% * 8766 hours in a year
= 0.9TWh/year
income for year = 0.9G * \$0.026 = \$23.3 million
Payback = \$1.7 billion / \$23.3 million
= 73.0 years

That's not a good value (for Kitegen), need some more input.

You're right about the windlift videos - the sound adds a lot. Good presentation.

I've seen your videos also - good stuff. Might come and visit you one day for a chat ...
Have you considered security applications - like airborne CCTV.
Schools may be interested, and even big companies - surveillance stuff. Like drones.

Derek
• DaveS Obviously hit a raw nerve there. Sounds like you need some funding ... I suppose you can t change the habits of a lifetime. Don t be afraid of the truth,
Message 27 of 29 , Oct 20, 2012
DaveS

Obviously hit a raw nerve there. Sounds like you need some funding ...

I suppose you can't change the habits of a lifetime.

Don't be afraid of the truth, don't be afraid of making mistakes.

It's called progress.

Derek
• Derek, Where does your 50% factor come from ? High altitude winds are more constant for a given speed.See Cristina Archer s and Ken Caldeira s publications.
Message 28 of 29 , Oct 20, 2012

Derek,

>Where does your 50% factor come from ?

High altitude winds are more constant for a given speed.See Cristina Archer's and Ken Caldeira's publications.

You ask a good question about the possible link between the lack of reliable datas and investments _ although AWE is not enough mature to offer its own datas _ ,but evaluations are complex and can require months of work to taking account of the site,the costs of land or sea allowed,of system,of maintenance,the efficiency etc.,and should be made by an entity not depending of the company which products are tested.Why not yourself?AWE is an emergent field within wind energy but also within aviation.

Optimization of the AWECS of type flygen - Kite Energy Systems is a short study,but not a curve:features of generator (volt/ampere) are not identical between lighting (toy or demonstrator) application and between charging application.

PierreB

> Message du 20/10/12 20:55
> De : "dcsoftstuff"
> A : AirborneWindEnergy@yahoogroups.com
> Copie à :
> Objet : [AWES] Re: ROI/COE Skystream 3.7 vs Selsam Supertwin 2kW vs TU Delft Kite 20kW
>
>

>
>
> PierreB
>
> Good spot, I didn't quantify the capacity factor.
>
> Where does your 50% factor come from ? I'm familiar with the 25->35% for conventional wind turbines.
> That's data you've measured yourself ?
>
> Any chance you can do the other calculation (ESAT), and compare with this one.
> Not sure whether there's sufficent information from kitegen for you to do that.
>
> Trying to keep the calculations simple, I know they'll present a rather rosy picture (or maybe not - see below),
> but factoring replacements. downtime, maintenance etc is complex,
> and the main point is to benchmark different systems against each other for comparison.
>
> Assuming 50% factor :
>
> Kitegen max energy produced per year = 200 stems * 3MW * 34% * 50% * 8766 hours in a year
> = 0.9TWh/year
> income for year = 0.9G * \$0.026 = \$23.3 million
> Payback = \$1.7 billion / \$23.3 million
> = 73.0 years
>
> That's not a good value (for Kitegen), need some more input.
>
> You're right about the windlift videos - the sound adds a lot. Good presentation.
>
> I've seen your videos also - good stuff. Might come and visit you one day for a chat ...
> Have you considered security applications - like airborne CCTV.
> Schools may be interested, and even big companies - surveillance stuff. Like drones.
>
> Derek
>
>

• Derek, You write Obviously hit a raw nerve there. Sounds like you need some funding ... Luckily mistaken on both counts. Playing whack-a-mole with AWE GIGO
Message 29 of 29 , Oct 20, 2012
Derek,

You write "Obviously hit a raw nerve there. Sounds like you need some funding ..."

Luckily mistaken on both counts. Playing whack-a-mole with AWE GIGO conclusions on the Forum is play; anyway, somebody needs to do it. As for funding, lets agree with Corwin, who said the worst thing that ever happened to Makni was an early flood of millions. My "Mexican" training is in applying minimal funding early, just \$2000 for a 300m2 wing (Mothra1), in response to Fort Felker's 2010 challenge to reduce aviation platform costs for AWES from \$500 to \$5 a lb. There has been ample OPM to play with tarps as an AWE scale-model medium. We are having a ball, best "job" of our lives.

You wrongly "suppose [no one] can change the habits of a lifetime".

Even if unchangeable bad habits were a personal challenge for you, why try and change good habits of others? In the AWE case we mean applicable practical arts and engineering-science cultures.

You then advise "Don't be afraid of the truth, don't be afraid of making mistakes, It's called progress".

Truth makes us properly fearless; the idea to be afraid of truth is therefore absurd. Lets be worried about not making enough silly mistakes to learn enough truth. Your mistakes (and insights) help the general effort, if you can bear the catching and correcting of errors, for "progress" to occur. Lets steel our emotions. Whether or not one is afraid is not so essential to doing an engineering job-

daveS

Your message has been successfully submitted and would be delivered to recipients shortly.