Messages in AirborneWindEnergy group.                          AWES 24322 to 24373 Page 378 of 440.
Group: AirborneWindEnergy Message: 24322 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24323 From: benhaiemp Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24324 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24325 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24326 From: benhaiemp Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24327 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24328 From: benhaiemp Date: 12/9/2018
Subject: Re: Available power in the wind

Group: AirborneWindEnergy Message: 24329 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24330 From: benhaiemp Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24331 From: dougselsam Date: 12/10/2018
Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v

Group: AirborneWindEnergy Message: 24332 From: dougselsam Date: 12/10/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24333 From: dougselsam Date: 12/10/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24334 From: dougselsam Date: 12/10/2018
Subject: KPS results from Glasgow?

Group: AirborneWindEnergy Message: 24335 From: Peter Sharp Date: 12/10/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24338 From: benhaiemp Date: 12/11/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24339 From: Peter Sharp Date: 12/11/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24340 From: benhaiemp Date: 12/11/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24341 From: dougselsam Date: 12/12/2018
Subject: "Other demos" at HAWP 2009?

Group: AirborneWindEnergy Message: 24342 From: dave santos Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24343 From: dave santos Date: 12/12/2018
Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v

Group: AirborneWindEnergy Message: 24344 From: benhaiemp Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24345 From: dave santos Date: 12/12/2018
Subject: Minesto raises another round of funding

Group: AirborneWindEnergy Message: 24346 From: dave santos Date: 12/12/2018
Subject: Re: KPS results from Glasgow?

Group: AirborneWindEnergy Message: 24347 From: dave santos Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24348 From: joe_f_90032 Date: 12/12/2018
Subject: Re: Minesto raises another round of funding

Group: AirborneWindEnergy Message: 24349 From: benhaiemp Date: 12/12/2018
Subject: Fort Felker's presentation in AWEC2017

Group: AirborneWindEnergy Message: 24350 From: benhaiemp Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24351 From: Santos Date: 12/12/2018
Subject: Re: Fort Felker's presentation in AWEC2017

Group: AirborneWindEnergy Message: 24352 From: Santos Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24353 From: benhaiemp Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24354 From: dougselsam Date: 12/12/2018
Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v

Group: AirborneWindEnergy Message: 24355 From: Santos Date: 12/12/2018
Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v

Group: AirborneWindEnergy Message: 24356 From: dougselsam Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24357 From: dougselsam Date: 12/12/2018
Subject: Re: KPS results from Glasgow?

Group: AirborneWindEnergy Message: 24358 From: Santos Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24359 From: dougselsam Date: 12/12/2018
Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v

Group: AirborneWindEnergy Message: 24360 From: dougselsam Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24361 From: Santos Date: 12/12/2018
Subject: Re: KPS results from Glasgow?

Group: AirborneWindEnergy Message: 24362 From: Santos Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24363 From: Santos Date: 12/12/2018
Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v

Group: AirborneWindEnergy Message: 24364 From: dougselsam Date: 12/12/2018
Subject: Re: KPS results from Glasgow?

Group: AirborneWindEnergy Message: 24365 From: Peter Sharp Date: 12/12/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24366 From: Santos Date: 12/12/2018
Subject: Re: KPS results from Glasgow?

Group: AirborneWindEnergy Message: 24367 From: benhaiemp Date: 12/13/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24368 From: benhaiemp Date: 12/13/2018
Subject: Re: Available power in the wind

Group: AirborneWindEnergy Message: 24369 From: Santos Date: 12/13/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24370 From: dougselsam Date: 12/13/2018
Subject: Re: KPS results from Glasgow?

Group: AirborneWindEnergy Message: 24371 From: dougselsam Date: 12/13/2018
Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v

Group: AirborneWindEnergy Message: 24372 From: joe_f_90032 Date: 12/13/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Group: AirborneWindEnergy Message: 24373 From: Santos Date: 12/13/2018
Subject: Re: KPS results from Glasgow?



Group: AirborneWindEnergy Message: 24322 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
Lets check Jameson's claims carefully before deciding he must be correct. His AWE content elsewhere suggests he is as prone to misconceptions as most of us. Here he seems to be arguing based on "thrust", in an odd way (see Wikipedia Thrust link below), conceding that the secondary rotor is not perfectly efficient. I think the lost power is found in greater wake micro-turbulence-

"The secondary rotor concept (Figure 6.16) also has potential for very large wind turbine systems where the conventional drive train solutions will be extremely heavy and expensive on account of low shaft speed and high rated torque. This concept involves rotors which are carried by the wind turbine blades of the main rotor. The secondary rotors thereby experience a much higher apparent wind speed than the ambient wind speed and can be of comparatively small diameter, high speed, low torque and low weight. The idea is quite old, possibly preceding patent applications of the 1980s and 1990s (Watson [19], St-Germain [20] and Jack [21]). It has sparked a few misconceptions. One is that the Betz limit will apply twice to the overall power conversion but, more curiously, another recent one is that the secondary rotor can achieve a power coefficient of unity [22]. Discounting any ground related effect, the power produced by a rotor must be exactly the same whether a wind turbine system is stationary in an ambient wind field of velocity, V, or is mounted on a vehicle (such as a moving wind turbine blade) and transported at velocity, V, through still air. In either case the relative axial fluid velocity local to the rotor disc is not V but V (1−a) where a is the axial induction factor at the rotor plane. A brief analysis of the secondary rotor concept follows. It is clearly the thrust (and not power) of the secondary rotor that provides reaction torque to extract power from the primary rotor. It appears that extraction of power from the primary rotor is most efficient when the axial induction of the secondary rotor is small. An interesting trade-off then arises between having larger and therefore more expensive, lightly loaded secondary rotors to improve efficiency and hence reduce cost of the major primary rotor system. Notation: Air density ρ Primary rotor radius R Primary rotor angular speed ω Primary rotor blade number N Secondary rotor radius r Secondary rotor power coefficient Cp Secondary rotor power coefficient Ct Secondary rotor axial induction a
Drive Train Design 129
The primary rotor produces power P which is as usual subject to the Betz limit. In terms of the thrust reaction T of each of the N secondary rotors and assuming for present convenience that they are mounted at the tip of each blade, P =NTRω T =0.5ρ (ωR)2 πr2Ct neglecting ambient wind speed compared to tip speed P = N0.5ρ (ωR)2 πr2CtRω P = N0.5ρω3R3πr2Ct The power extracted by the secondary rotors is Pe =0.5ρN (ωR)3 πr2Cp Thus Pe P = Cp Ct Considering the ideal Betz model: If
Cp Ct =
4a (1−a)2 4a (1−a) = (1−a). If the secondary rotor is optimised in its own right, then the usual choice of a =1/3 applies and the overall limit is 16 271− 1 3=0.395. This exceeds Betz squared by a little as 16 27 2 =0.351. However it is much better to trade reduced specific loading, Ct, on the secondary rotors at the cost of making them a little bigger. In a specific design study a =0.2 was about optimum. Hence the ratio Pe/P is (1−0.2) =0.8 and the overall limit is 16 27×0.8=0 .474. The power coefficient of the secondary rotors is reduced to a theoretical limit of 4×0 .2(1−0.2)2 =0.512 and the secondary rotors are somewhat larger and more expensive but this can be a very worthwhile trade off.

References- [19] Watson, W.K. (inventor) (1988) Space frame wind turbine. US Patent 4,735,552, Published 5 April 1988. [20] St-Germain, J. (inventor) (1992) Wind machine with electric generators and secondary rotors located on rotating vertical blades. US Patent 5,151,610, September 1992. [21] Jack, C. (inventor) (1992) Free rotor. World Patent WO/1992/020917, Published 26 November 1992. [22] Madsen, H.A. and Rasmussen, F. (inventors) (2008) Wind turbine having secondary rotors. European Patent Specification EP 1390615 B1. Published 30 April 2008."



 

 

Peter Sharp is right. Please see on http://ejurnal.bppt.go.id/digilib/sampul/9781119975441.pdf : "innovation in wind turbine design" (Peter Jamieson), page 128: "It has sparked a few misconceptions. One is that the Betz limit will apply twice to the overall power conversion..." and page 129 about secondary rotors.

 

 

 

 

 

 

 

 

 

 

 

 

 
Group: AirborneWindEnergy Message: 24323 From: benhaiemp Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

Both Peter are right: Peter Sharp and Peter Jamieson.


Albert lives.
Group: AirborneWindEnergy Message: 24324 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
The resolution may be that the primary turbine is not the WECS PTO, and in any case could never near max Betz, due to the induced drag of the secondary turbines, which still could approach Betz. In this sense, a double Betz penalty does not apply, but there is still a lot of parasitic efficiency-loss, so it still seems like a problematic AWES basis. 

This is a more nuanced view of turbine-on-a-turbine inefficiency, compared to all our initial assumptions.



 

Lets check Jameson's claims carefully before deciding he must be correct. His AWE content elsewhere suggests he is as prone to misconceptions as most of us. Here he seems to be arguing based on "thrust", in an odd way (see Wikipedia Thrust link below), conceding that the secondary rotor is not perfectly efficient. I think the lost power is found in greater wake micro-turbulence-

"The secondary rotor concept (Figure 6.16) also has potential for very large wind turbine systems where the conventional drive train solutions will be extremely heavy and expensive on account of low shaft speed and high rated torque. This concept involves rotors which are carried by the wind turbine blades of the main rotor. The secondary rotors thereby experience a much higher apparent wind speed than the ambient wind speed and can be of comparatively small diameter, high speed, low torque and low weight. The idea is quite old, possibly preceding patent applications of the 1980s and 1990s (Watson [19], St-Germain [20] and Jack [21]). It has sparked a few misconceptions. One is that the Betz limit will apply twice to the overall power conversion but, more curiously, another recent one is that the secondary rotor can achieve a power coefficient of unity [22]. Discounting any ground related effect, the power produced by a rotor must be exactly the same whether a wind turbine system is stationary in an ambient wind field of velocity, V, or is mounted on a vehicle (such as a moving wind turbine blade) and transported at velocity, V, through still air. In either case the relative axial fluid velocity local to the rotor disc is not V but V (1−a) where a is the axial induction factor at the rotor plane. A brief analysis of the secondary rotor concept follows. It is clearly the thrust (and not power) of the secondary rotor that provides reaction torque to extract power from the primary rotor. It appears that extraction of power from the primary rotor is most efficient when the axial induction of the secondary rotor is small. An interesting trade-off then arises between having larger and therefore more expensive, lightly loaded secondary rotors to improve efficiency and hence reduce cost of the major primary rotor system. Notation: Air density ρ Primary rotor radius R Primary rotor angular speed ω Primary rotor blade number N Secondary rotor radius r Secondary rotor power coefficient Cp Secondary rotor power coefficient Ct Secondary rotor axial induction a
Drive Train Design 129
The primary rotor produces power P which is as usual subject to the Betz limit. In terms of the thrust reaction T of each of the N secondary rotors and assuming for present convenience that they are mounted at the tip of each blade, P =NTRω T =0.5ρ (ωR)2 πr2Ct neglecting ambient wind speed compared to tip speed P = N0.5ρ (ωR)2 πr2CtRω P = N0.5ρω3R3πr2Ct The power extracted by the secondary rotors is Pe =0.5ρN (ωR)3 πr2Cp Thus Pe P = Cp Ct Considering the ideal Betz model: If
Cp Ct =
4a (1−a)2 4a (1−a) = (1−a). If the secondary rotor is optimised in its own right, then the usual choice of a =1/3 applies and the overall limit is 16 271− 1 3=0.395. This exceeds Betz squared by a little as 16 27 2 =0.351. However it is much better to trade reduced specific loading, Ct, on the secondary rotors at the cost of making them a little bigger. In a specific design study a =0.2 was about optimum. Hence the ratio Pe/P is (1−0.2) =0.8 and the overall limit is 16 27×0.8=0 .474. The power coefficient of the secondary rotors is reduced to a theoretical limit of 4×0 .2(1−0.2)2 =0.512 and the secondary rotors are somewhat larger and more expensive but this can be a very worthwhile trade off.

References- [19] Watson, W.K. (inventor) (1988) Space frame wind turbine. US Patent 4,735,552, Published 5 April 1988. [20] St-Germain, J. (inventor) (1992) Wind machine with electric generators and secondary rotors located on rotating vertical blades. US Patent 5,151,610, September 1992. [21] Jack, C. (inventor) (1992) Free rotor. World Patent WO/1992/020917, Published 26 November 1992. [22] Madsen, H.A. and Rasmussen, F. (inventors) (2008) Wind turbine having secondary rotors. European Patent Specification EP 1390615 B1. Published 30 April 2008."

On ‎Sunday‎, ‎December‎ ‎9‎, ‎2018‎ ‎12‎:‎29‎:‎57‎ ‎PM‎ ‎PST, Pierre BENHAIEM pierre-benhaiem@orange.fr [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com


 

 

Peter Sharp is right. Please see on http://ejurnal.bppt.go.id/digilib/sampul/9781119975441.pdf : "innovation in wind turbine design" (Peter Jamieson), page 128: "It has sparked a few misconceptions. One is that the Betz limit will apply twice to the overall power conversion..." and page 129 about secondary rotors.

 

 

 

 

 

 

 

 

 

 

 

 

 
Group: AirborneWindEnergy Message: 24325 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
Correcting my prior conjecture; the primary rotor is in fact loaded by the secondary rotors, and Betz applies. Betz seemingly also applies to secondary rotors analyzed in their apparent Taylor approximation wind field. 

Its looks like an open question still, whether Peter & Peter or DS & DS is more correct.



 

The resolution may be that the primary turbine is not the WECS PTO, and in any case could never near max Betz, due to the induced drag of the secondary turbines, which still could approach Betz. In this sense, a double Betz penalty does not apply, but there is still a lot of parasitic efficiency-loss, so it still seems like a problematic AWES basis. 

This is a more nuanced view of turbine-on-a-turbine inefficiency, compared to all our initial assumptions.

On ‎Sunday‎, ‎December‎ ‎9‎, ‎2018‎ ‎12‎:‎58‎:‎54‎ ‎PM‎ ‎PST, dave santos santos137@yahoo.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com


 

Lets check Jameson's claims carefully before deciding he must be correct.. His AWE content elsewhere suggests he is as prone to misconceptions as most of us. Here he seems to be arguing based on "thrust", in an odd way (see Wikipedia Thrust link below), conceding that the secondary rotor is not perfectly efficient. I think the lost power is found in greater wake micro-turbulence-

"The secondary rotor concept (Figure 6.16) also has potential for very large wind turbine systems where the conventional drive train solutions will be extremely heavy and expensive on account of low shaft speed and high rated torque. This concept involves rotors which are carried by the wind turbine blades of the main rotor. The secondary rotors thereby experience a much higher apparent wind speed than the ambient wind speed and can be of comparatively small diameter, high speed, low torque and low weight. The idea is quite old, possibly preceding patent applications of the 1980s and 1990s (Watson [19], St-Germain [20] and Jack [21]). It has sparked a few misconceptions. One is that the Betz limit will apply twice to the overall power conversion but, more curiously, another recent one is that the secondary rotor can achieve a power coefficient of unity [22].. Discounting any ground related effect, the power produced by a rotor must be exactly the same whether a wind turbine system is stationary in an ambient wind field of velocity, V, or is mounted on a vehicle (such as a moving wind turbine blade) and transported at velocity, V, through still air. In either case the relative axial fluid velocity local to the rotor disc is not V but V (1−a) where a is the axial induction factor at the rotor plane. A brief analysis of the secondary rotor concept follows. It is clearly the thrust (and not power) of the secondary rotor that provides reaction torque to extract power from the primary rotor. It appears that extraction of power from the primary rotor is most efficient when the axial induction of the secondary rotor is small. An interesting trade-off then arises between having larger and therefore more expensive, lightly loaded secondary rotors to improve efficiency and hence reduce cost of the major primary rotor system. Notation: Air density ρ Primary rotor radius R Primary rotor angular speed ω Primary rotor blade number N Secondary rotor radius r Secondary rotor power coefficient Cp Secondary rotor power coefficient Ct Secondary rotor axial induction a
Drive Train Design 129
The primary rotor produces power P which is as usual subject to the Betz limit. In terms of the thrust reaction T of each of the N secondary rotors and assuming for present convenience that they are mounted at the tip of each blade, P =NTRω T =0.5ρ (ωR)2 πr2Ct neglecting ambient wind speed compared to tip speed P = N0.5ρ (ωR)2 πr2CtRω P = N0..5ρω3R3πr2Ct The power extracted by the secondary rotors is Pe =0.5ρN (ωR)3 πr2Cp Thus Pe P = Cp Ct Considering the ideal Betz model: If
Cp Ct =
4a (1−a)2 4a (1−a) = (1−a). If the secondary rotor is optimised in its own right, then the usual choice of a =1/3 applies and the overall limit is 16 271− 1 3=0.395. This exceeds Betz squared by a little as 16 27 2 =0.351. However it is much better to trade reduced specific loading, Ct, on the secondary rotors at the cost of making them a little bigger. In a specific design study a =0.2 was about optimum. Hence the ratio Pe/P is (1−0.2) =0.8 and the overall limit is 16 27×0.8=0 .474. The power coefficient of the secondary rotors is reduced to a theoretical limit of 4×0 .2(1−0.2)2 =0.512 and the secondary rotors are somewhat larger and more expensive but this can be a very worthwhile trade off.

References- [19] Watson, W.K. (inventor) (1988) Space frame wind turbine. US Patent 4,735,552, Published 5 April 1988. [20] St-Germain, J. (inventor) (1992) Wind machine with electric generators and secondary rotors located on rotating vertical blades. US Patent 5,151,610, September 1992. [21] Jack, C. (inventor) (1992) Free rotor. World Patent WO/1992/020917, Published 26 November 1992. [22] Madsen, H.A. and Rasmussen, F. (inventors) (2008) Wind turbine having secondary rotors. European Patent Specification EP 1390615 B1. Published 30 April 2008."

On ‎Sunday‎, ‎December‎ ‎9‎, ‎2018‎ ‎12‎:‎29‎:‎57‎ ‎PM‎ ‎PST, Pierre BENHAIEM pierre-benhaiem@orange.fr [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com


 

 

Peter Sharp is right. Please see on http://ejurnal.bppt.go.id/digilib/sampul/9781119975441.pdf : "innovation in wind turbine design" (Peter Jamieson), page 128: "It has sparked a few misconceptions. One is that the Betz limit will apply twice to the overall power conversion..." and page 129 about secondary rotors.

 

 

 

 

 

 

 

 

 

 

 

 

 
Group: AirborneWindEnergy Message: 24326 From: benhaiemp Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

See also Dave Lang's message https://groups.yahoo.com/neo/groups/AirborneWindEnergy/conversations/messages/3304:

"

Theo,

I would take your Betz limit admonition one step further.

Since our raw source of fuel for AWE is free, considerations as they pertain to "efficiency" can be more or less simply quantified as to whether "Return on Investment" (ROI) and "Cost of Power" (COP) are good enough to warrant competitive energy offerings to the market place, and attract investment. One could conceivably design a system that is only 5% efficient in a "Betz sort of way", and still be successful.

That said, I would further comment that on this forum, there is a huge amount of BS being thrown about regarding the meaning and calculation of so called "Betz limits" (a term that has become used in this forum as virtually a generalized concept applying to everything). I would say that anyone who would contend to understand and speak knowledgeably about such limits on these complex designs should first go through the math and understand how the Betz limit was derived for the simple windmill type system......then before blithely applying it to everything and declaring such things as "double and triple Betz penalties" , should try to derive what a "Betz limit" might look like for the system in question. This will quickly give you a knew appreciation for that of which you speak!

DaveL

"
Group: AirborneWindEnergy Message: 24327 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
I agree with DaveL, Theo, and [Costello et al, 2015], that discussion of Betz in an AWE context is not very predictive (often "BS") however, when someone like Pierre wants to bring the subject back into discussion, its worth reviewing.



 

See also Dave Lang's message https://groups.yahoo.com/neo/groups/AirborneWindEnergy/conversations/messages/3304:

"

Theo,

I would take your Betz limit admonition one step further.

Since our raw source of fuel for AWE is free, considerations as they pertain to "efficiency" can be more or less simply quantified as to whether "Return on Investment" (ROI) and "Cost of Power" (COP) are good enough to warrant competitive energy offerings to the market place, and attract investment. One could conceivably design a system that is only 5% efficient in a "Betz sort of way", and still be successful.

That said, I would further comment that on this forum, there is a huge amount of BS being thrown about regarding the meaning and calculation of so called "Betz limits" (a term that has become used in this forum as virtually a generalized concept applying to everything). I would say that anyone who would contend to understand and speak knowledgeably about such limits on these complex designs should first go through the math and understand how the Betz limit was derived for the simple windmill type system......then before blithely applying it to everything and declaring such things as "double and triple Betz penalties" , should try to derive what a "Betz limit" might look like for the system in question. This will quickly give you a knew appreciation for that of which you speak!

DaveL

"
Group: AirborneWindEnergy Message: 24328 From: benhaiemp Date: 12/9/2018
Subject: Re: Available power in the wind

Dave Lang mentioned 4/27 for a "pure drag device" on https://groups.yahoo.com/neo/groups/AirborneWindEnergy/conversations/messages/6790 in Aug, 15, 2012:

I derived this in the same style used to derive the classical Betz limit...

So (at least by my derivation) for a device like a "parachute" or a "Ship on a down-wind run under sail",

1. The Max power extraction fraction = "(4/27)* Cd"
2. Peak power extraction occurs at a "downwind device speed" of "(1/3) Vwind".

He precised:
OF course the devil is in the details concerning the value of Cd, since it is itself a quantified measurement of a device's propensity to catch air. For instance, a flat plate has a Cd frequently quoted as about 1.1, Thus, a flat plate operating as a drag device to capture wind power, will exhibit the ability to extract only  about 15% of the incident power (compared to the classical turbine limit of 59%).

That confirms my example on https://forum.awesystems.info/t/betz-limit-and-power-available-in-the-wind/88 I put also on the current topic, putting it again:
100 m² HAWT vs a 100 m² full surface. Wind speed = 10 m/s, air density = 1.2.

  • HAWT: the power at Betz limit is 1/2 x 100 x 1.2 x 1000 x 16/27 = 35555 W.
  • Now the full surface of 100 m²: the traction (force) is 1/2 x 100 x 1.2 x 100 = 6000 N. Let us reel-out this surface in the optimal speed of 1/3 wind speed, considering the wind speed on the surface is now only 2/3 wind speed, leading to the result: 20000 x 4/9 = 8888 W, so exactly 1/4 of 35555 W. Some explains: 20000 = 6000 N X 3.33 m/s reel-out speed, and 4/9 is 2/3² as the wind force is squared.

4/27 is also the max power mentioned by "The Betz limit applied to Airborne Wind Energy" for a lift (yoyo) power system for a crosswing kite going downwind. But for what I know this was not explicitly indicated before. So Tallak please can you give the reference (chapter, book)? 


IMHO the 4/27 of a flat plane is also the 4/27 of a same area swept by a lift (yoyo) crosswind kite as both go downwind.
Group: AirborneWindEnergy Message: 24329 From: dave santos Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
Betz's Law is The GGS model predicts that peak efficiency is achieved when the flow through the turbine is approximately 61% of the total flow which is very similar to the Betz result of 2/3 for a flow resulting in peak efficiency, but the GGS predicted that the peak efficiency itself is much smaller: 30.1%"


Best tested values run between Betz and GGS, no flat turbine ever actually reaches Betz. DaveL rightly notes the natural tendency of layfolk to confuse complex drag factors with ideal Betz assumptions. Betz is an obsolete substitute for state-of-the-art turbine efficiency analysis, a historical curiosity more than a useful tool.


 

I agree with DaveL, Theo, and [Costello et al, 2015], that discussion of Betz in an AWE context is not very predictive (often "BS") however, when someone like Pierre wants to bring the subject back into discussion, its worth reviewing.

On ‎Sunday‎, ‎December‎ ‎9‎, ‎2018‎ ‎02‎:‎10‎:‎00‎ ‎PM‎ ‎PST, pierre-benhaiem@orange.fr [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com


 

See also Dave Lang's message https://groups.yahoo.com/neo/groups/AirborneWindEnergy/conversations/messages/3304:

"

Theo,

I would take your Betz limit admonition one step further.

Since our raw source of fuel for AWE is free, considerations as they pertain to "efficiency" can be more or less simply quantified as to whether "Return on Investment" (ROI) and "Cost of Power" (COP) are good enough to warrant competitive energy offerings to the market place, and attract investment. One could conceivably design a system that is only 5% efficient in a "Betz sort of way", and still be successful.

That said, I would further comment that on this forum, there is a huge amount of BS being thrown about regarding the meaning and calculation of so called "Betz limits" (a term that has become used in this forum as virtually a generalized concept applying to everything). I would say that anyone who would contend to understand and speak knowledgeably about such limits on these complex designs should first go through the math and understand how the Betz limit was derived for the simple windmill type system......then before blithely applying it to everything and declaring such things as "double and triple Betz penalties" , should try to derive what a "Betz limit" might look like for the system in question. This will quickly give you a knew appreciation for that of which you speak!

DaveL

"
Group: AirborneWindEnergy Message: 24330 From: benhaiemp Date: 12/9/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

DaveS indicates "We also have noted that a turbine-on-a-looping-wing is a turbine-on-a-turbine, which compounds Betz Limit loss*."


It looks like a double Betz penalty, what Jamieson’s work denies as a misconception I already mentioned on this topic. Even DaveL noted "...declaring such things as "double and triple Betz penalties...".

So DaveS probably doesn't understand as he agrees.

And why allude to the Betz limit when it would be obsolete?
Group: AirborneWindEnergy Message: 24331 From: dougselsam Date: 12/10/2018
Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v
daveS said "The aeronautical best-practice suggestion to Doug made at HAWPcon2009 was for a streamlined aerostat (microblimp) envelope with good gas retention, rather than the weather balloons repeatedly used, which leak away gas quickly."

DougS replies: Well anyone could observe that a blimp would have worked better than balloons.  To me it is a "suggestion" that hardly needs to be said, if the audience is aero people.  It's about as easy as telling someone they might consider tying their shoes.  Obviously, if I would have had a blimp handy, I would have used it, right?  The reason I did not use  blimp is I had a few days to get a demo up to Oroville, and knew where to get balloons and helium quickly and locally, with little lead time and at low expense.  Even small blimps are expensive and were not available at the drop of a hat.  If I would have insisted everything be "perfect" I probably wouldn't have had time to get the only working AWE demo to the conference.  I thought it was important for there to be one working demo, otherwise, what would all the fuss be about?  What would newspapers photograph?  Hundreds of people saying they could generate wind-powered electricity from the sky, without a single working example?

daveS then said: " If using helium is a moral fault, I have used my share"

DougS replies: It was inappropriate for you to complain I was "wasting helium", period.  Basically it was just one more opportunity for you to make a personal attack.  Obviously the world had the helium available at low cost, or I would not have been able to buy two tanks full, at a retail store down the street.  The fact that daveS now admits to having also wasted helium in the past is just what you'd expect.  Suddenly, after flagging it as some sort of "helium sin", he doesn't want to be left out of the "wasting-helium club", whereas previously it was stated as a reason against the lone AWE demo I brought to HAWP 2009.

daveS then said: "Doug could also have used a pilot-lifter kite to lift his WECS, like many do."

DougS replies: You seem to have an incredible grasp of the obvious in some ways, combined with no comprehension of not only the obvious, but of my previous explanation, which, again, reflects a well-known and very obvious known factor in wind energy:  A wind energy system needs wind to work.  One would think a kite person would know a lifter kite also needs wind to work.  The amount of wind at the Oroville event was too little for a pilot kite to lift the Sky Serpent apparatus.  Period.  End of story.  The whole thing would have been lying on the ground the whole time, or the kite might have flown some of the time without being able to lift the rest of the machine.  You continued complaints and lack of reasoning ring hollow.

Here's what I'd like you to answer:
You keep saying there were other demos at the first conference.
Could you please explain to the rest of the class what these supposed demos were, their principle of operation, their rated power, maybe some photos, and fill in what further development has taken place for these supposed demonstration-level AWE systems in the ensuing 9 years?


---In AirborneWindEnergy@yahoogroups.com, <santos137@...  

I agree that helium has its problems.
But for demonstrating the ST at that conference with so little wind, it was the only way I had available.
Even with its limitations, nobody can categorically rule out helium, hydrogen, etc. as potentially useful.
Group: AirborneWindEnergy Message: 24332 From: dougselsam Date: 12/10/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
Betz has in general been verified by large turbines, some of which reportedly come very close to Betz under the right conditions, and not too far off in most conditions.
Group: AirborneWindEnergy Message: 24333 From: dougselsam Date: 12/10/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
dveS said:"We also have noted that a turbine-on-a-looping-wing is a turbine-on-a-turbine, which compounds Betz Limit loss*.

Keep these facts in mind when reviewing Betz claims in AWE.

====
* As agreed by DougS. 

Adding to previous post, Doug's SuperTurbine variants that align with the wind are 2nd "Betz-beater" example. Betz paradoxes resolve in a 3D field-theory model of wind turbine dynamics."

DougS replies:  I only said there is a double-Betz limit for a turbine on a wing due to the general lack of rigorous analysis in this venue. I wanted to see how easily it would be taken as a given.  Since Betz describes how much energy goes through the turbine versus how much goes around the turbine, the energy that goes around (avoids) the propeller-on-a-wing might still be available to the wing itself in the larger-scale wind flow.  It's all bout keeping things moving.  Obviously there are so many complicating factors that a complete analysis of any such given configuration more complicated than a single, 2-dimensional propeller would be difficult.  When real wind people joke about a SuperTurbine "beating Betz" we know it is tongue-in-cheek, since the Betz analysis refers to a theoretically-two-dimensional disc.  Betz did not consider multiple turbines in n endless chain in an open windflow.  It was never meant to take a long 3-D configuration in an open flow into account.  Obviously any configuration is going to throw away some energy, but to sit here after a decade, still wondering about the Loyd paper and Betz, when even Loyd himself apparently thought his paper was not that big of a deal, is like arguing how many angels can dance on the head of a pin, without the ability to produce a working pin anyway.  I think discussions like this are an attempt to substitute empty blather for working systems.  What difference does endless amateur-level "analysis" make if there's no AWE apparatus out there approaching Betz as a limiting factor anyway?  Same thing with the whole "quantum physics", Bose-Einstein, "phonons", "spidermill", and the whole kit-and-kabooble of endless talking points with no working system?  If Phonons are so great, where's a single module showing it?  If Spidermill is such a worship-worthy topic, in such urgent need, why does nobody build one?  Same with "laddermill" - said to be a breaakthrough, just not worth anyone's time to build one?  If daveS is the most effective airborne wind energy researcher, where is his resulting AWE demo?  What is its rated power? Can we see it in action?
Group: AirborneWindEnergy Message: 24334 From: dougselsam Date: 12/10/2018
Subject: KPS results from Glasgow?

Over the last several years we've heard a lot of claims of future success from KPS (Kite Power Systems).  For some, the KPS effort was to prove the efficacy of kite-reeling in general, and for others, the KPS configuration specifically.  During the last couple of years, we've been eagerly awaiting the results of their highly-publicized program to power X number of homes in Scotland, having been informed of activities involving their new test facility in Glasgow.  We were told a lot of details, such as a grid-connection, renting office space, arranging for the ability to test during summer months (to avoid certain birds in winter months) etc.  The KPS kite-reeling system was to have been in operation during this past season, powering homes from this strategic test facility.  Now that we've been through the entire allowed operational season, what are the results?  How much power did they make, and when?  How much accumulated energy was sent to the grid?  What details do we have of the operation?  Where does that place them now, and what's next?  Enquiring minds would like to know.
Group: AirborneWindEnergy Message: 24335 From: Peter Sharp Date: 12/10/2018
Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
Attachments :

    Hi DaveS and PierreB,

    I can’t do the math, but the analyses of tip rotors I’ve seen so far, including Jamieson, don’t seem to include the various vector angles of airflow that need to be considered. And that makes me skeptical about the accuracy of the existing analyses. Here are two variables that may need to be considered:

    1)    The tip rotor on a HAWT is following a curved path, and

    2)    The true wind is at a right angle to the path of the tip rotor.

    Both of these variables may influence the airflow through the tip rotor, so they need to be considered, even if only to show why they are irrelevant.

    For a conventional HAWT, the airflow that is slowed by passing through the rotor has to keep moving downwind while expanding. That is what determines the Betz limit. Energy is required to move that slowed air away from the back of the rotor. So enough energy has to remain in the airflow to keep that slowed air moving away from the back of the rotor.

    But in the case of a tip rotor, the true wind is at a right to the path of the tip rotor. That is not a situation to which the Betz limit applies. The true wind comes from the side of the tip rotor, you might say. There is a large angle between the apparent wind flowing through the tip rotor and the true wind. That is because the relative wind created by the movement of the tip rotor is roughly 6 times the true wind speed.

    So the situation is roughly analogous to putting a model HAWT in front of a blowing fan, and then placing another blowing fan to the side and slightly behind the model HAWT so as to blow the slowed air away from behind the model HAWT.

    In that case, the model HAWT should benefit from the energy from the side-fan. The side fan should enable more air from the front fan to flow through the model HAWT to increase its power.

    Assuming that this side-fan analogy is reasonable, the test could be performed using a model HAWT and two fans. If the side fan did increase the power of the model HAWT, that would suggest that the current analyses of tip rotors is incomplete. The implication would be that the tip rotor might be able to exceed the Betz limit due to the true wind sweeping away the air from behind the tip rotor..

    A further indication would be that a complete and accurate determination of the tip rotor’s Cp needs to include a vector analysis of the airflows acting on the tip rotor.

    DaveS: If you can show why the airflow vectors I mentioned are irrelevant, please do so. Or, if you can show that a side-fan would not increase the power of the model HAWT, then please do so. Or, if you can show that my analogy is incorrect, then please do so. Otherwise, I think that we should remain skeptical about the existing analyses until we have more data.

    PeterS

     

     

    From: AirborneWindEnergy@yahoogroups.com [mailto:AirborneWindEnergy@yahoogroups.com]
    Sent: Sunday, December 09, 2018 11:04 AM
    To: AirborneWindEnergy@yahoogroups.com
    Subject: Re: [AWES] Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" case)

     

     

    A looping foil is a turbine (a wing with angular velocity), subject to Betz Limit. You oddly propose that turbines-on-a-looping foil escape Betz by some principle maybe only known by Makani (a Secret Sauce theory)

     

    Having been inside of the early Makani venture (via KiteShip) and having closely followed them ever since, I do not know who exactly would ever be able to find an aerodynamic principle unknown to the aerospace field (excepting Dave Culp's soft kite work). Never forget that no one in early Makani had an aerospace background (again, Culp closest, as a Marine Engineer) up to the architectural down-select based on Loyd, which Loyd himself did not think was the optimal architecture.

     

    Fortunately, the M600 is nearing its definitive fate, settling whether there was any "secret sauce" (there was not).

     

     

     

     

     

    On ‎Sunday‎, ‎December‎ ‎9‎, ‎2018‎ ‎10‎:‎29‎:‎40‎ ‎AM‎ ‎PST, 'Peter Sharp' sharpencil@sbcglobal.net [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com

    Group: AirborneWindEnergy Message: 24338 From: benhaiemp Date: 12/11/2018
    Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

    Hi PeterS and DaveS,


    The secondary discussion about the secondary rotors came from DaveS' quote: “We also have noted that a turbine-on-a-looping-wing is a turbine-on-a-turbine, which compounds Betz Limit loss*.", suggesting a second Betz limit for the secondary rotors.

    In addition to PeterS' previous message (quoting also "...the efficiency of the RAT could be over 80%."), it was the reason why I mentioned Dave Lang's message and also Peter Jamieson's work. Both also suggest the second Betz limit doesn't apply.

    That said I can agree that data and analyses are not still sufficient. Even Peter Jamieson notes it is a "brief, analysis". So "a vector analysis of the airflows acting on the tip rotor" (PeterS) is needed.


    Now there is also an experimental data by Makani since 2013, which is available on https://collegerama.tudelft.nl/Mediasite/Play/1065c6e340d84dc491c15da533ee1a671d, about 3' 10" after the start, on M. Diehl's presentation.

    I report: "10 kW for a 4 m² plane at 8 m/s". This value is high and would allow to estimate that the secondary turbines make few losses. Beside it there is a comparison with a yoyo system using a similar rigid wing: "3 kW for a 3 m² plane at 13 m/s", so ten times less.


    PeterS,

    I have to disagree with your "side-fan analogy", as the side-fan adds a power source while there is only one power source, not two. The secondary rotors produce torque with their respective thrust (not power). Peter Jamieson noted this point: " It is clearly the thrust (and not power) of the secondary rotor that provides reaction torque to extract power from the primary rotor."

    Concerning 1), it also depends of the radius of tip (secondary) rotors in regard to the radius of the primary rotor.


    A better experimental mean would be measuring a HAWT with then without secondary rotors.

    Group: AirborneWindEnergy Message: 24339 From: Peter Sharp Date: 12/11/2018
    Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
    Attachments :

      Hi Pierre,

      I’m suggesting that there is, in fact, a second power source that has not been considered. That second power source is the true wind which is quickly dissipating the air behind the tip rotor. That is what a vector analysis should reveal. And that is why the double-fan analogy should apply.

      Thanks for the Makani reference, but the website was unresponsive so I couldn’t get the information you referred to.

      PeterS

       

      From: AirborneWindEnergy@yahoogroups.com [mailto:AirborneWindEnergy@yahoogroups.com]
      Sent: Tuesday, December 11, 2018 1:16 AM
      To: AirborneWindEnergy@yahoogroups.com
      Subject: RE: [AWES] Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" case)

       

       

      Hi PeterS and DaveS,

       

      The secondary discussion about the secondary rotors came from DaveS' quote: “We also have noted that a turbine-on-a-looping-wing is a turbine-on-a-turbine, which compounds Betz Limit loss*.", suggesting a second Betz limit for the secondary rotors.

      In addition to PeterS' previous message (quoting also "...the efficiency of the RAT could be over 80%."), it was the reason why I mentioned Dave Lang's message and also Peter Jamieson's work. Both also suggest the second Betz limit doesn't apply.

      That said I can agree that data and analyses are not still sufficient. Even Peter Jamieson notes it is a "brief, analysis". So "a vector analysis of the airflows acting on the tip rotor" (PeterS) is needed.

       

      Now there is also an experimental data by Makani since 2013, which is available on https://collegerama.tudelft.nl, about 3' 10" after the start, on M. Diehl's presentation.

      I report: "10 kW for a 4 m² plane at 8 m/s". This value is high and would allow to estimate that the secondary turbines make few losses. Beside it there is a comparison with a yoyo system using a similar rigid wing: "3 kW for a 3 m² plane at 13 m/s", so ten times less.

       

      PeterS,

      I have to disagree with your "side-fan analogy", as the side-fan adds a power source while there is only one power source, not two. The secondary rotors produces torque with their respective thrust (not power). Peter Jamieson noted this point: " It is clearly the thrust (and not power) of the secondary rotor that provides reaction torque to extract power from the primary rotor."

      Concerning 1), it also depends of the radius of tip (secondary) rotors in regard to the radius of the primary rotor.

       

      A better experimental mean would be measuring a HAWT with then without secondary rotors.

       

       

       
      Group: AirborneWindEnergy Message: 24340 From: benhaiemp Date: 12/11/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

      Peter,


      My link did not work, so I sent my message with the working link I put again: https://collegerama.tudelft.nl/Mediasite/Play/1065c6e340d84dc491c15da533ee1a671d (about 3 minutes and 10 seconds from the beginning).

      You indicate: "That second power source is the true wind which is quickly dissipating the air behind the tip rotor.". IMHO there is only one power source which is the true wind. The "wind which is quickly dissipating the air behind the tip rotor" is derived from the true wind and is not a power source as such. However as you mention "a vector analysis should reveal" what happens. I don't think "the double-fan analogy should apply" because the side-fan would add an external power source. And practically testing it would be difficult due to turbulence caused by the two fans.
      Group: AirborneWindEnergy Message: 24341 From: dougselsam Date: 12/12/2018
      Subject: "Other demos" at HAWP 2009?
      daveS:  Can you please give details and any photos of the "other demos" you have said were at HAWP 2009 in Chico/Oroville?
      Group: AirborneWindEnergy Message: 24342 From: dave santos Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      Wikipedia's Betz article clearly documents that the "law" is just a very idealized approximation that omits significant factors. This is especially true for AWE, where the added demands of flight and the disc-assumption of Betz just don't fit well. Wind itself varies, such that high Betz performance is a rare condition. Pierre need not wonder that the toy world of Betz and the real world of aerospace R&D differ so much, much like Chess and actual War do. David Lang (and Loyd) represented AWE's earliest engineering development, where already Betz hardly predicted anything. The AWES Forum has been tolerant of the view that Betz somehow really matters. It doesn't. Its a troll.

      So here is a reformulation of the specific issue of turbine-on-a-turbine efficiency, without Betz-

      A real world turbine has various drag losses, and cannot possibly be 100% efficient. A real turbine-on-a-turbine involves similar losses for both turbines, and these losses add up for a lower overall efficiency, fully in accord with Newton and Thermodynamics.

      The misconception is to imagine a turbine-on-a-turbine somehow escapes compounded efficiency loss, while invoking Betz.
      Group: AirborneWindEnergy Message: 24343 From: dave santos Date: 12/12/2018
      Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v
      Doug concedes his ST was problematically heavy even at small-scale, but he could have used a large pilot kite to lift his ST WECS at HAWPcon09, by matching the kite size to lift his load in the wind available (~12mph). He flew with weather balloons on more than one occasion. A streamlined micro-blimp envelope may have been an obvious improvement to him, but he never bothered.

      My additional informal AWES conference demos where discussed on the AWES Forum years ago. In summary, I brought a carload of small prototypes, and JoeF reminded me that I had shown these in the parking lot, flying some short-lined, and holding others in the wind (like KiteMotor1, which flew in public multiple times). Some of the devices were HAWTS, others were flip-wings, and power-kites. I also flew different devices under a pilot kite next to Doug, but for short sessions. Doug knows these experimental devices rate from around ~1-500W. JoeF received a tested 10W flygen HAWT from me at the event. These were not scaled-up designs, just working scale-models, as rapid prototyping due diligence. Let Doug disparage toy AWES demos all he likes; history shows aviation grew from toys.

      The closest to a 100kW demo I have done is 300m2 Mothra lifting and dumping tonnage of wet sand in a gale. One can see the great mass lifted at a good velocity. That demo did not happen at HAWPcon09, but at WSIKF (kite fest), and the experience of raw power was awesome. Doug is welcome to measure the power of any of my 100+ prototypes to satisfy his curiosity. Its still unknown just what load Doug claims was connected to his demo in '09. Various of my demos had LEDs, batteries, or other loads in the circuits. Not that it matter much, an unloaded demo is welcome too.
      Group: AirborneWindEnergy Message: 24344 From: benhaiemp Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

      "The misconception is to imagine a turbine-on-a-turbine somehow escapes compounded efficiency loss, while invoking Betz." (DaveS).


      Some example:


      "We also have noted that a turbine-on-a-looping-wing is a turbine-on-a-turbine, which compounds Betz Limit loss*." (DaveS).
      Group: AirborneWindEnergy Message: 24345 From: dave santos Date: 12/12/2018
      Subject: Minesto raises another round of funding
      Not really news, that kite tech continues to advance and raise investment, underwater or above-

      https://www.energylivenews.com/2018/12/10/innoenergy-provides-new-wave-of-investment-for-tidal-developer-minesto/
      Group: AirborneWindEnergy Message: 24346 From: dave santos Date: 12/12/2018
      Subject: Re: KPS results from Glasgow?
      No real mystery about KPS. Its the accustomed distraction of marketing claims v kite reality. On the marketing side, KPS has hardly been the worst source of AWE hype. Venture hype is best disregarded in favor of specific analysis from available data. The kite reality is that KPS's twin-kite architecture is unlikely to be the dominant architecture, but it will be simple to drop the twin set-up.

      For judging the KPS case, power-kite data is widely available from many sources. KPS has measured the same powerful force peaks everyone else does. The biggest shadow over KPS is if they over-commit to a me-too rigid-wing detour. They should test a rigid wing version, leaving the door open to revert to the soft power-kite standard, if (when) the rigid wing disappoints.

      Its a long game whether KPS prevails as a technical leader. In following AWE, expert patience is justified.
      Group: AirborneWindEnergy Message: 24347 From: dave santos Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      Yes, Pierre, within misapplied ideal Betz assumptions, I can still claim a compounded Betz Limit makes sense, lacking true formal proof to the contrary. My key difference is with Peter & Peter's claims, to the effect that there is no compounded turbine-on-a-turbine loss in either the toy world of Betz, or the real world of AWE. By contrast, I claim there is compounded inefficiency in both the over-idealized toy case, and the real world.
      Group: AirborneWindEnergy Message: 24348 From: joe_f_90032 Date: 12/12/2018
      Subject: Re: Minesto raises another round of funding

      InnoEnergy

      is the mentioned investor. 
      Search on their site over "Minesto"  gives HERE
      some related articles. 
      Group: AirborneWindEnergy Message: 24349 From: benhaiemp Date: 12/12/2018
      Subject: Fort Felker's presentation in AWEC2017

      On this forum and elsewhere we always considered Makani as an AWE leader if no the AWE leader, making smart choices, making much progress from small wings to the current 600 kW plane.

      To see Felker's presentation click on http://www.awec2017.com/presentations-main.html then on Fort Felker.
      Group: AirborneWindEnergy Message: 24350 From: benhaiemp Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      A lot of claims, few supported statements...
      Group: AirborneWindEnergy Message: 24351 From: Santos Date: 12/12/2018
      Subject: Re: Fort Felker's presentation in AWEC2017
      We see Makani as the leader in high complexity AWE, the path of high cost and pain. Fort himself is not deeply informed in general AWE, based on my getting to know him at NREL, and first brief him, then years of keeping in touch  by email, and now his climaxic focus on Makani's Hawaii challenges. M600 power curve is not shared in this "old" video. Average performance is apparently weak, and catastrophic crashing is still likely. Thanks to Fort for doing the testing needed to decide any doubts.
      Group: AirborneWindEnergy Message: 24352 From: Santos Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      Claims are best tested by time. All claims welcomed. New claim- Betz is not a proper physical "law". It would best be classed a "crude approximation".
      Group: AirborneWindEnergy Message: 24353 From: benhaiemp Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

      "The misconception is to imagine a turbine-on-a-turbine somehow escapes compounded efficiency loss, while invoking Betz." (DaveS).


      Some example:


      "We also have noted that a turbine-on-a-looping-wing is a turbine-on-a-turbine, which compounds Betz Limit loss*." (DaveS).
      Group: AirborneWindEnergy Message: 24354 From: dougselsam Date: 12/12/2018
      Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v
      To daveS:
      Thanks for explaining what you meant by "other demos" at HAWP 2009.
      Your account seems somewhat embellished or exaggerated to me.
      I do not remember any other AWE system running at HAWP 2009.
      What I remember is a couple of incomplete, pitiful, homemade toys that made no power and showed a lack of AWE activity, and a lack of AWE knowledge, at an "AWE" conference.
      Got any photos? 

      daveS said: "Doug concedes his ST was problematically heavy even at small-scale, but he could have used a large pilot kite to lift his ST WECS at HAWPcon09, by matching the kite size to lift his load in the wind available (~12mph)."
      DougS replies:  I don't think so.  I never "conceded" the ST demo was "problematically heavy".  In fact it's pretty darn light, but not so light as to be able to fly in almost zero wind.  In my experience, there was not enough wind to keep a pilot-lifter kite aloft by itself.  Such a lifter kite would have flown, then not flown, flown, not flown.  It never would have lifted any extra weight.  You need a decent amount of wind just to lift the kite and rope.  We did not have a steady wind strong enough at HAWP 2009.

      daveS goes on: "He flew with weather balloons on more than one occasion. A streamlined micro-blimp envelope may have been an obvious improvement to him, but he never bothered."
      DougS replies: You keep saying the same thing over and over even though I've already answered you.  I could just as easily say YOU "never bothered" to bring a blimp to elevate your toys.  Where was your blimp if you think everyone should have brought a blimp?  At least I brought the only actual functioning AWE system generating electricity to the event.

      As for your last statement:
      "Its still unknown just what load Doug claims was connected to his demo in '09. Various of my demos had LEDs, batteries, or other loads in the circuits. Not that it matter much, an unloaded demo is welcome too."
      DougS replies:  Not sure why you keep saying there was no load connected, or use the word "claims" as though I'm lying about it.  I don't have a track record of making false statements like most of the rest of the field, especially you.  That Sky Serpent demo has always been the same, in all the old videos on Youtube, as the centerfold in Popular Science June 2008, at HAWP 2009, and in my more recent Youtube videos where I used a kite and also showed the power produced, on meters, for the camera.

      You can see a good view of the generator here:
      And you can see the generator at HAWP 2009 here:
      And you can see the same basic arrangement of four (4) automotive batteries to achieve a "48-Volt system" here:

      Since you attempt to include windblown tarps shedding sand while lifting off the beach as qualifying for a "100 kW airborne Wind Energy System", anyone can see that you consider any standards whatsoever as not applying to you.  I agree.  Let it be so:  No standards whatsoever shall be applied to daveS, from the field of Airborne Wind Energy.  I mean, why start now?  Have fun.



      ---In AirborneWindEnergy@yahoogroups.com, <santos137@...
      My additional informal AWES conference demos where discussed on the AWES Forum years ago. In summary, I brought a carload of small prototypes, and JoeF reminded me that I had shown these in the parking lot, flying some short-lined, and holding others in the wind (like KiteMotor1, which flew in public multiple times). Some of the devices were HAWTS, others were flip-wings, and power-kites. I also flew different devices under a pilot kite next to Doug, but for short sessions. Doug knows these experimental devices rate from around ~1-500W. JoeF received a tested 10W flygen HAWT from me at the event. These were not scaled-up designs, just working scale-models, as rapid prototyping due diligence. Let Doug disparage toy AWES demos all he likes; history shows aviation grew from toys.

      The closest to a 100kW demo I have done is 300m2 Mothra lifting and dumping tonnage of wet sand in a gale. One can see the great mass lifted at a good velocity. That demo did not happen at HAWPcon09, but at WSIKF (kite fest), and the experience of raw power was awesome. Doug is welcome to measure the power of any of my 100+ prototypes to satisfy his curiosity. Its still unknown just what load Doug claims was connected to his demo in '09. Various of my demos had LEDs, batteries, or other loads in the circuits. Not that it matter much, an unloaded demo is welcome too.
      Group: AirborneWindEnergy Message: 24355 From: Santos Date: 12/12/2018
      Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v
      Lifting mass up is an old basic standard of mechanical power, as you should know.

      So, still no disclosure of just what your output was connected to? I missed seeing any load. Sorry you missed my brief demos.
      Group: AirborneWindEnergy Message: 24356 From: dougselsam Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      The Betz coefficient limits power output per unit swept are for all wind energy systems.
      Thinking that any system is not limited by Betz is symptomatic of newbies who always turn out to be wrong.
      The laughable thing is such people are never close to extracting the max allowed by the Betz coefficient anyway, so why are they arguing about it in the first place?  It's like someone with a wheelbarrow arguing whether they'll be limited in speed by the sound barrier.

      The reason I floated the statement about a double-Betz coefficient was to see if daveS would start repeating it as fact, which he did.  I was just floating it out there as a contribution to get a discussion going. 

      The reason I question it though, (and I can't claim to have it entirely worked out), is that the propeller being forced through the air is, in itself, limited by the Betz coefficient, but the energy it doesn't harvest (wind that goes around it instead of through it, due to slowing the flow through it) may still remain as energy available in the main flow (true wind) for the larger wing to still extract.  So I can imagine the possibility that only a single application of Betz applies, even though there are two levels of blades, each limited by Betz, yet if the larger blade can steal the scraps wasted by the smaller blade back into the system, maybe Betz only applies once.  Maybe the real answer is somewhere in between?  As far as Betz just not applying, that's never true in wind energy.  You can just think of any wind energy system as a "black box" with a given frontal area, to which Betz always applies as a max limiting factor in power extraction.  Typical of AWE: the simple and obvious question has been looming for a decade, and yet nobody has it worked out. 

      But I agree that it hardly matters until it becomes a limiting factor for a working AWE system.  Sometimes theory results in working systems, but other times it's working systems that everyone agrees work, but nobody can figure out exactly how, that drive theory.  Take, for example, the theory of lift:  In use as the main non-animal industrial power in Europe for 900 years, now the basis for long-range transportation, and the main source of industrial power for the world (jet turbine blades), studied ad infinitum, and yet the experts still do not totally agree on any one explanation for the true cause of "lift"...

      Anyway, "common sense" points toward lots of extra losses from a wing driving another wing, instead of just driving a generator directly, like "adding another middleman", but it seems in aero design, what seems like common sense is not always true.  Example: For most people, a heavy jetliner ambling along at a low speed and altitude, looks "impossible", yet there it is, flying.
      Group: AirborneWindEnergy Message: 24357 From: dougselsam Date: 12/12/2018
      Subject: Re: KPS results from Glasgow?
      Hey daveS:  I'm not sure why you pretend to have answered my question.  You obviously don't know the answer.  Seems like you just can't sit still and wait for someone who knows the answer to give it, or find out what the answer is before "answering" with no answer.  Why waste your time saying nothing?

      How about this question:  Has the KPS system even flown at all lately?
      I believe if an entity publicizes every detail of a supposed program, getting everyone from me to daveS to Bill Gates, the general public, and of course their own fans and investors, all excited, they should finish telling what happened.  It's like telling a long joke, then leaving when its time for the punchline.  Like saying you're cooking a fantastic dinner so everyone sticks around getting more and more hungry, then there's no food.

      Of course I did tell everyone about what normally happens with wind energy "breakthroughs":  "They quietly go away"...
      Group: AirborneWindEnergy Message: 24358 From: Santos Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      A compounded Betz limit has long been discussed in wind tech for turbineonturbine case, like Jamison confirms. Let Doug first claim he understood the idea as correct, now maybe not. I find it holds even within Betz approximation. This was my opinion before Doug mentioned it, as the record will show.

      The real test is whether turbineonturbine wins over competing concepts, on merits, or loses by inherent flaws.
      Group: AirborneWindEnergy Message: 24359 From: dougselsam Date: 12/12/2018
      Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v
      How many times do I have to tell you it was connected to 4 car batteries?  Just like in my latest video.
      Not 3, not 5, 4.  A standard "48-Volt" system.  Do you have trouble with reading comprehension (Oh geez, let me guess...  Could you imagine being his elementary school teacher?) 
      Real wind energy systems need a predetermined voltage for a load, and the range is surprisingly tight.
      Group: AirborneWindEnergy Message: 24360 From: dougselsam Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      Betz was really smart.
      The Betz coefficient was derived mathematically, with the approximation of an incompressible flow.
      The derivation is not that complicated.  Betz did a good job of isolating what's really going on in a wind turbine.
      To properly answer the question of double-Betz as applied to a turbine-on-turbine configuration, you'd have to be smart, like Betz.
      But going from the black box analogy, you don't have to be that smart to know Betz definitely applies at least once.
      Group: AirborneWindEnergy Message: 24361 From: Santos Date: 12/12/2018
      Subject: Re: KPS results from Glasgow?
      The expert view is that KPS better be testing and learning and competitors should presume they are. 

      A lack of announcements can remind us of the silence of the Wright Brothers, which was wrongly construed as failure in France. Alarm over KPS failure is premature and overwrought.
      Group: AirborneWindEnergy Message: 24362 From: Santos Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      Betz was smart, but was not even the originator of the limit formula. Payne was smarter.
      Group: AirborneWindEnergy Message: 24363 From: Santos Date: 12/12/2018
      Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v
      Thanks, I overlooked any prior disclosure. Suggesting that the batteries would best have been deep discharge. What was the overcharge prevention?
      Group: AirborneWindEnergy Message: 24364 From: dougselsam Date: 12/12/2018
      Subject: Re: KPS results from Glasgow?
      daveS said "The expert view is that KPS better be testing and learning and competitors should presume they are."
      DougS replies: "expert view"  This is an amazingly haughty statement.  When you say "the expert view", you mean "your opinion", right?

      Still, you've sort-of pretended to answer my question without saying anything except confirming that your opinion is that you are the expert, while admitting you have no idea of the answer of any question pertaining to KPS activity in this recent, highly-publicized test period.  More than a year has gone by.  People actually interested in AWE care what happens in AWE.

      daveS said: "A lack of announcements can remind us of the silence of the Wright Brothers, which was wrongly construed as failure in France. Alarm over KPS failure is premature and overwrought.":
      DougS replies:  Seen this movie many times daveS.  So have you, but maybe you were asleep.  Nobody said anything about "alarm".  I simply asked if anyone has any information on the KPS testing program this past summer.
      You might remember:
      Ockels =
      Group: AirborneWindEnergy Message: 24365 From: Peter Sharp Date: 12/12/2018
      Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
      Attachments :

        Hi DougS,

        The Betz limit is intended to apply to single rotor HAWT facing the true wind. Other wind energy systems will have their own limits, obviously, but they may not be precisely the Betz limit. For example, studies of VAWT indicate that the Cp limit for an ideal VAWT should be between .61 and .63, depending upon the aerodynamic model that is used. But those studies are, in my opinion, seriously flawed because they do not consider that an extremely wide VAWT, where the wind can speed up before reaching the downwind blades, could produce a much higher Cp than the Betz limit for HAWT. That doesn’t mean that such a VAWT would be practical. It merely demonstrates that the Betz limit should be applied only to where it is intended to be applied. It is not applicable to all wind energy systems. However, the basic idea that there is a limit on the Cp -- because some of the energy in the wind must be used to move slowed air away from the behind a wind energy system -- does apply. But the limit may be different for different types of systems. Some may be higher, and some may be lower. The Betz limit is intended to apply to a special case. It is not a universal limit on all wind energy systems.

        A tip rotor will definitely have a limit on its Cp. But it is not likely to be the same as the Betz limit because the aerodynamic conditions are different.

        A tip rotor is almost certain to be less efficient than driving a generator directly. The advantage of tip rotors is that they are potentially much less expensive than a direct-drive generator. In some cases, a lower cost may be more important than the higher efficiency when it comes to determining the cost of the energy. That is the main reason for considering tip rotors. Another reason is that tip rotors may produce some useful energy in wind speeds that are too low for a direct-drive generator.

        PeterS

         

         

        From: AirborneWindEnergy@yahoogroups.com [mailto:AirborneWindEnergy@yahoogroups.com]
        Sent: Wednesday, December 12, 2018 2:04 PM
        To: AirborneWindEnergy@yahoogroups.com
        Subject: RE: [AWES] Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" case)

         

         

        The Betz coefficient limits power output per unit swept are for all wind energy systems.

        Thinking that any system is not limited by Betz is symptomatic of newbies who always turn out to be wrong.

        The laughable thing is such people are never close to extracting the max allowed by the Betz coefficient anyway, so why are they arguing about it in the first place?  It's like someone with a wheelbarrow arguing whether they'll be limited in speed by the sound barrier.

         

        The reason I floated the statement about a double-Betz coefficient was to see if daveS would start repeating it as fact, which he did.  I was just floating it out there as a contribution to get a discussion going. 

         

        The reason I question it though, (and I can't claim to have it entirely worked out), is that the propeller being forced through the air is, in itself, limited by the Betz coefficient, but the energy it doesn't harvest (wind that goes around it instead of through it, due to slowing the flow through it) may still remain as energy available in the main flow (true wind) for the larger wing to still extract.  So I can imagine the possibility that only a single application of Betz applies, even though there are two levels of blades, each limited by Betz, yet if the larger blade can steal the scraps wasted by the smaller blade back into the system, maybe Betz only applies once.  Maybe the real answer is somewhere in between?  As far as Betz just not applying, that's never true in wind energy.  You can just think of any wind energy system as a "black box" with a given frontal area, to which Betz always applies as a max limiting factor in power extraction.  Typical of AWE: the simple and obvious question has been looming for a decade, and yet nobody has it worked out. 

         

        But I agree that it hardly matters until it becomes a limiting factor for a working AWE! system.  Sometimes theory results in working systems, but other times it's working systems that everyone agrees work, but nobody can figure out exactly how, that drive theory.  Take, for example, the theory of lift:  In use as the main non-animal industrial power in Europe for 900 years, now the basis for long-range transportation, and the main source of industrial power for the world (jet turbine blades), studied ad infinitum, and yet the experts still do not totally agree on any one explanation for the true cause of "lift"...

         

        Anyway, "common sense" points toward lots of extra losses from a wing driving another wing, instead of just driving a generator directly, like "adding another middleman", but it seems in aero design, what seems like common sense is not always true.  Example: For most people, a heavy jetliner ambling along at a low speed and altitude, looks "impossible", yet there it is, flying.
        Group: AirborneWindEnergy Message: 24366 From: Santos Date: 12/12/2018
        Subject: Re: KPS results from Glasgow?
        Let non-experts worry that KPS is not working hard.
        Group: AirborneWindEnergy Message: 24367 From: benhaiemp Date: 12/13/2018
        Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c

        In AWE knowledge about Betz limit is also a mean to partially evaluate the land/space use of an AWES.

        The 16/27 limit concerns crosswind AWES with a stationary swept area like drag systems (flygen like Makani), rotating AWES (Sky Windpower, Daisy, Rotating Reel...), rotors carried with kites (Kitewinder) or blimps (Altaeros and others).

        The 4/27 limit (in fact even far less due to the recovery phase) concerns AWES with a going downwind swept area like yoyos, that with crosswind or not crosswind kites.

        The potential of a lesser land use is better for the 16/27 limit AWES.  
        Group: AirborneWindEnergy Message: 24368 From: benhaiemp Date: 12/13/2018
        Subject: Re: Available power in the wind

        In AWE knowledge about Betz limit is also a mean to partially evaluate the land/space use of an AWES.

        The 16/27 limit concerns crosswind AWES with a stationary swept area like drag systems (flygen like Makani), rotating AWES (Sky Windpower, Daisy, Rotating Reel...), rotors carried with kites (Kitewinder) or blimps (Altaeros and others).

        The 4/27 limit (in fact even far less due to the recovery phase) concerns AWES with a going downwind swept area like yoyos, that with crosswind or not crosswind kites.

        The potential of a lesser land use is better for the 16/27 limit AWES.  
        Group: AirborneWindEnergy Message: 24369 From: Santos Date: 12/13/2018
        Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
        In AWE, we have defined better dimensionless numbers than Betz for kitepower land and airspace efficiency-

        2D land-to-power

        3D airspace-to-power

        Along with our power-to-weight number, all these are better than Betz to analyze AWES.
        Group: AirborneWindEnergy Message: 24370 From: dougselsam Date: 12/13/2018
        Subject: Re: KPS results from Glasgow?
        daveS said:  "Let non-experts worry that KPS is not working hard."

        DougS replies:
        1) Who's "worried"?  For me this repeated scenario gets close to comedy.  Like Lucy and the football every year.  Who sid nything about "working hard"?  Can you ever stick to a topic at all?

        2) If you were an "expert", (in either kites or AWE) you would know the answer to the question of what's happened in the past year in the most highly-publicized effort to develop kite-reeling.

        3) If you don't know anything, don't have anything to show, what exactly makes you an "expert"?

        4) Can you provide a single reference, any article, paper, website, patent, book, movie, video, document, apparatus, power data, anything confirming your status as an "expert" besides you, yourself claiming it?  Do you not realize, continually claiming you are "an expert" or often "the expert", amounts to circular reasoning?  I hate to break it to you, but normally, people wait for someone else to call them "expert".

        5) I'm guessing the only source you can find for anyone calling you an "expert" is you, on this forum, or in e-mails complaining to people who won't let you read their non-expert worthless opinions for free.  Seems like maybe that's the real purpose of this forum - a place where you can cook up an illusion of some contrived, fake, delusional "concensus" that you are "an expert"

        6) Most people would, at some point, conclude a person continually calling themselves an "expert" without any agreement from any other source, is exhibiting signs of mere conceit, and possibly "delusions of grandeur".

        7) There is no reason for you to appear to "answer" a question that you have no answer for.  There is not some need in the world to read an "answer" from someone who does not have an answer or know an answer.  Not every question requires your input, although to judge from the fact that you probably have more posts here than everyone else combined, you seem to think it does.


        ---In AirborneWindEnergy@yahoogroups.com, <santos137@...
        Group: AirborneWindEnergy Message: 24371 From: dougselsam Date: 12/13/2018
        Subject: Re: Reply to Doug's post// Re: [AWES] Re: W = m * g (NASA syntax) v
        daveS asked: "Thanks, I overlooked any prior disclosure. Suggesting that the batteries would best have been deep discharge. What was the overcharge prevention?"
        DougS replies:  If you watch my latest video carefully, you'll see the interior ceiling of the van is a burned, tattered mess of hanging cloth and brown stains.  I don't normally use even a charge controller for testing, to keep things s simple as possible.  You can use new deep-cycle batteries, new industrial batteries, or, going down the spectrum, even old car batteries which are often free.  Considering you just need a voltage to run the turbine into to take data from a test vehicle, and are not worried actually storing any energy while testing, you don't care if you use old, worthless batteries that present a voltage without really having much holding capacity left.  Sometimes they explode, hence the tattered ceiling.  To look at what's left of the ceiling, you can figure out that I've done a lot of valuable testing from that vehicle.  None of this has changed in the last decade.  It's always been the same.  I started out thinking "Yeah, I'll have to get a charge controller soon." but old batteries are cheap or free, and the worst that happens is more damage to the cloth ceiling of the test vehiccup.

        I've had other people gasp at the fact of no charge controller, trying to tell me "you HAVE to have one!"  Well, no, actually you don't, and here's why:  We're usually not just letting it run for days on end while truck-testing.  We're usually testing for short bursts going up and down a given straightaway, taking the average of data from both directions (like at the Bonneville salt flats) to make sure the data is not influenced by a headwind, or tailwind.  We can optionally connect a "load tester" to burn off any excess stored energy between runs, if the voltage starts staying persistently high.  I've also used headlights to burn off power.

        When we use this vehicle as a stationary tower for a SuperTwin, as it has been for the last 7 years, everything usually runs through an inverter.  Now I can tell you right now, the more information I provide to ignorant people who "just want to argue", especially people insisting they are some sort of "expert" (when nobody else calls them an expert), the more extraneous partial-facts they will pull out of their asses to try to argue further that somehow I don't know what I'm doing, while they do. 

        I'd just take all your previous statements of having examined my setup, combined with all the statements of not knowing anything about the setup, and realize there is no basis for any further discussion of it, so when you think of 10 more extraneous half-understood reasons to argue with me further, or to try and catch me in some "gotcha" moment, please consider that it is not worth anyone's time to hear more meaningless blather on the subject.  I'd concentrate on why you "never bothered" to bring a blimp to test your supposed "demos" at HAWP 2009.
        Group: AirborneWindEnergy Message: 24372 From: joe_f_90032 Date: 12/13/2018
        Subject: Re: Review: Turbine-on-a-wing Reanalysis (and second "Betz-beater" c
        A "single rotor" is actually a complex thing; it has shape, station configuration, station impact on the wind it sees.     One may make the station configuration as complicated as one wishes; the "single rotor" still  remains a single rotor. A single rotor might have a million tiny secondary rotors; yet the gross thing is still a single rotor. This matter supports DougS' mention of "black box" analysis.  We are limited in how much we may mine from involved wind; mine up to the limit as best possible; then after that point we just cannot mine any more.  
        Group: AirborneWindEnergy Message: 24373 From: Santos Date: 12/13/2018
        Subject: Re: KPS results from Glasgow?
        KPS just passed it's Sept 15 season end, as specified by it's range contract. Bird compatibility was a first issue. How they will spend 5 million plus, from Shell etc, in the next couple of years, is in planning.

        Doug seems to overreact to this picture. KPS will test as expected.