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Working horizontal-axis wind turbine (HAWT)
This working horizontal-axis wind turbine (HAWT) generates 0.85 W of DC electrical power from the 8 m/s wind of a large floor fan.
About this creation
Please feel free to look over the images and skip the verbiage.

This working horizontal-axis wind turbine (HAWT) is loosely based on the onshore version of the iconic Vestas V90 (product brochure with images available here).

By "working", I mean that it generates useful electrical power from the wind power supplied by a large floor fan -- not wind power from battery power, as most of the "working" LEGOŽ wind turbines I've seen do.





On this page:Warning! Always wear eye protection when working or playing with high-speed LEGOŽ rotating machinery and keep valuables and bystanders (including pets) a safe distance away -- especially when testing new designs. Really.




Overview

This model HAWT comes with 2 very different 3-blade rotors, here mounted on the same shaft for comparison. The smaller, better-performing "go" rotor, with blades at 2, 6, and 10 o'clock, looks less like the real thing but produces ~70% more power for reasons explained here.



The blades of the larger "show" rotor are at 12, 4, and 8 o'clock. Both rotors drive the same generator through the same single-stage 3:1 rotor:generator reduction gear.

The next 5 photos show the entire HAWT -- the first 3 with the "go" rotor mounted, and the last 2 with the "show" rotor.











The respective scalings of the "show" and "go" rotors WRT the V90 and the images above tell pretty much the same story: The diameter of the "show" rotor is a better fit with the tower and nacelle, and its long, slender blades look a lot more like those of a real megawatt-class wind turbine.

Problem is, you just can't have good looks and high torque in the same rotor at the low tip-speed ratios (2.0 at best) attainable with LEGOŽ rotor blades.



V90 vs. model rotors

In a steady 15 m/s design wind, a full-scale Vestas V90 at sea level generates 3 MW of 50 Hz AC power from a swept area of 6,352 m2. Under these conditions, the 90 meter, 3.8 x 107 kg, 3-blade rotor turns at ~16 RPM. (Today's offshore HAWT rotors can exceed 150 m in diameter!) The rotor hub sits 105 m off the ground. Overall efficiency is ~23%.

The model's 0.276 m, 0.022 kg "go" rotor below is identical to the pusher prop on my third-generation motorized prop-cart. It has a swept area of 0.054 m2 and spins at 1,150 RPM in the 8.2 m/s design wind prevailing at a distance of 0.30 m in front of the floor fan rotor hub.



Despite a 25% loss of wind power per unit swept area due to the lower air density at my elevation (1,793 m), the "go" rotor manages to generate 0.85W of DC power with an overall efficiency of 6% (from wind power in to electrical power out.)

The 0.106 m2 swept area of the larger, heavier 0.368 m, 0.038 kg "show" rotor doubles that of the "go" rotor, but its blades generate less lift and more drag and hence exert less net torque on the rotor shaft.



Accordingly, the "show" rotor spins at a much slower 827 RPM in the same 8.2 m/s inflow. Nevertheless, it generates 0.5 W of DC power with an overall efficiency of 2%.



Scaling with respect to the V90

With the more efficient "go" rotor, the model scales WRT the V90 as follows: 1:326 in rotor diameter, 1:251 in hub height above the ground, 77:1 in rotor speed, 1:1.2 x 105 in swept area, 1:3.5 x 106 in electrical power output, and 1:3.9 in overall efficiency. I'm rather proud of that last figure.

With the larger "show" rotor, geometric similarity with the V90 improves: 1:245 in rotor diameter, 1:225 in hub height above ground, 56:1 in rotor speed, 1:6.0 x 104 in swept area, 1:6.0 x 106 in electrical power output, and 1:13 in overall efficiency.

Clearly, the "go" rotor puts the "show" rotor to shame WRT power output and efficiency, but the "show" rotor is a much better visual fit.




Design goals

My interest in wind turbines in general and HAWTs in particular grew out of a fascination with propellers of all kinds sparked by an ongoing powerboat building spree. It took very little digging to discover that these simple-looking HAWTs are anything but when you start maximizing electrical output while keeping them in one piece and running smoothly in a stiff wind.

As I read more, it soon became clear that real wind turbine designers face some very interesting and thoroughly coupled aerodynamic, mechanical, and electrical trade-offs. Tasty nasty stuff indeed.

I undertook this project to gain first-hand experience with some of those trade-offs. It worked too well. Sooner or later, every major design issue surrounding HAWTs popped up in this MOC, and none of them were easily resolved in the LEGOŽ realm.

The result: One of the hardest design challenges I've ever encountered. The testing was particularly time-consuming and more than once called for test rigs that turned out to be design and building challenges in their own right. Far-flung parts from the many rotors that turned to shrapnel along the way still turn up around the house.



Metering and electrical load

My HAWT uses the Energy Meter (bb491) from the LEGOŽ Education Renewable Energy Add-on Set (9688) in 2 different ways: (i) The built-in digital multimeter functionality allows me to monitor output voltage, current, and power in real time in a way that doesn't interfere with turbine operation. (ii) The built-in charger for the dedicated Energy Meter battery serves as a convenient electrical load on the generator.



My HAWT has a few things in common with the working HAWT built from 9688 instructions:
  • Both use the Energy Meter for the same things, but I'm not data-logging the readings with an NXT or EV3 at this point.
  • The "go" rotor also uses the set's "wind turbine blades" (WTBs), though not in the same way.
  • For practical reasons, both HAWTs use a large Technic turntable to control rotor yaw (the angle between the rotor shaft and the wind direction) from the base of the tower rather than from the base of the nacelle.
However, it's not just a mod of the 9688 wind turbine. The functional and visual differences are substantial:
  • The 3-blade WTB-based "go" rotor is much lighter than the set's 6-blade rotor.
  • The "go" rotor hub design is lighter and stiffer and results in a greater rotor diameter.
  • The non-WTB "show" rotor bears no resemblance to the one in the instructions.
  • It takes a lot more torque to turn my M-motor generator than it does the set's E-motor generator, but I get a lot more electrical power out in return.
  • My tower, nacelle, and "show" rotor look a lot more like those of a real megawatt-class HAWT.
  • I drive my yaw control system differently.


Go rotor

The strong, stiff "go" rotor easily withstands speeds of over 2,000 RPM. The blades don't look much like those of a real megawatt-class rotor, but there's a good aerodynamic reason for that.



Of all the factors that go into wind turbine blades design, the most important by far is the operating tip-speed ratio (TSR, the ratio of undisturbed upstream wind speed to rotor tip linear speed). At the "high" TSRs (4-7) typical of real megawatt-class HAWTs, efficiency strongly favors long, slender blades tapering toward their tips. At the "low" TSRs (≤2.0) attainable by LEGOŽ HAWTs, however, fan-like blades tapering toward their roots are most efficient.

The "go" rotor's TSR-appropriate blade geometry goes a long way toward explaining why it's over 3 times more efficient than the "show" rotor, but lower drag and axial moment of inertia also contribute.









This close-up shows how the blades mount on the hub. The 3:1 rotor:generator reduction gear is clearly seen.



Show rotor

The rather heavy "show" rotor has 3 long, slender blades, each consisting of a #5 and #6 Technic long smooth fairing joined base-to-base. Its construction evolved from that developed for the original 2-blade pusher prop on my second-generation motorized prop-cart (more details there).





Remarkably, the "show" rotor stays in one piece without glue up to ~1,000 RPM but disintegrates without warning at higher speeds. Eye protection is an absolute must when working with rotors and props like this.





The "show" rotor feels a bit rickety in hand. It stiffens up nicely under centrifugal force but vibrates more than the "go" prop -- especially above its design speed of 827 RPM. This vibration saps power that could otherwise have gone to the generator.





The sandwich-style hub and 1x7 thin liftarms serving as blade struts are quite strong. The tandem 1x2 cross-blocks at the outer ends of the struts grip the 8L stopped axles threaded through the blade assembly surprisingly well. (The axle stop is at the blade end.)




Nacelle and reduction gear

The single-stage 3:1 rotor:generator reduction gear matches the torque-speed characteristic of the rotor to that of the generator. Higher and lower gear ratios reduced power output significantly.







I designed the nacelle's internal structure (i) to provide adequate support and reinforcement for the rotor and generator shafts, and (ii) to reduce power losses due to unwanted motions of the M motor generator. The latter would have been a lot easier with the mounting options of an L motor.



Megawatt-class wind turbines are required to have aviation warning lights atop their nacelles. A trans-clear light-saber blade inside the stacked white pin connectors conducts light up to the red lens on top of this one. The PF LED illuminating it is hidden in this the shot.





Tower and yaw mechanism

The tower is easily the most stressed structure within the HAWT. Next in line are the cross-blocks holding the blade axles and the turntable at the base of the tower. The tower had to be stiffened quite a bit to withstand the thrust generated by the rotors at speed.



The tower and nacelle together act like an inverted pendulum with a natural frequency of sway determined by their relative masses and tower stiffness.

Every time a blade passes the tower, the latter receives a pressure pulse. Because the rotors have 3 blades, the frequency of the tower excitations due to blade-crossings is just 3 times the rotor's rotational frequency.

Failure to keep the tower excitation frequency well above or well below the natural frequency of the tower-nacelle system is a good recipe for structural damage due to uncontrolled growth in sway amplitude. Harmonics of the excitation frequency can also excite excessive tower motions under the right (or wrong) conditions.

Fiddling with tower stiffness and nacelle mass to alter the tower-nacelle system's natural frequency resulted in an HAWT that swayed very little when fitted with the "go" rotor.

However, I could never quite put enough "distance" between the tower-nacelle natural frequency and the 29% lower excitation frequency of the "show" rotor. The resulting rotor-to-tower power transfer contributes to the "show" rotor's reduced efficiency.





The connector block at right center is the electrical hub of the HAWT. It delivers power from the generator in the nacelle to the Energy Meter's charging circuit and provides power to the aviation light from the Energy Meter's battery.



The PF switch at right center serves several purposes. First, it allows me to run the Energy Meter's battery back down to an energy reading of 0 Joules prior to its next charging by the HAWT by using the battery to run the generator as a motor.

The rotors have enough moment of inertia that the battery drops from 100 Joules to 0 Joules in well under 30 seconds. (This frustratingly wimpy NiCd battery is gone in a flash under almost any load but takes hours to charge with a PF AA battery box -- the fastest and most reliable of its approved charging options. Definitely not one of TLG's better electrical efforts.)

The switch also allows me to disconnect the generator from its electrical load (the Energy Meter battery charger) at will. Removing the load reduces the torque needed to turn the generator. The "show" rotor then becomes self-starting. Otherwise, it needs a nudged to get going. The higher-torque "go" rotor self-starts either way.



The turbine's output is very sensitive to yaw angle -- i.e., the angle between its rotor shaft and the direction of air inflow. Even a few degress of yaw causes a noticeable fall-off in the power reading on the Energy Meter.

The remote control yawing system provides a way to fine-tune turbine and fan rotor alignment prior to fan start-up and keep them aligned during turbine operation without having to get body parts near the spinning turbine blades. An NXT-based automatic yaw control system is on my to-do list.



The M yawing motor (largely hidden in the photos above) powers the 72:1 worm drive on the right side of the LBG tower base. The worm drive, in turn, drives the turntable supporting the white tower at a further 7:1 reduction. The 1,512:1 total reduction results in a 2° s-1 yawing rate -- a workable compromise between operator impatience and the need for fine control.



Base and Energy Meter

The Energy Meter, the 4 large wheels and tires, the black boat weights on the right, and the AA battery box hidden beneath the LBG base all serve as ballast, among other things, to keep the rotor's thrust from pushing the HAWT over backwards. The tires also damp vibrations and keep the HAWT from dancing around on hard surfaces when the "show" rotor is running.












Horizontal-axis wind turbines (HAWTs)

A wind turbine is to large extent the antithesis of a fan: It converts a fraction of the wind power passing through its rotor disk into electrical power rather than the other way around.

Permanent-magnet DC electric motors, a category that includes all 9V LEGOŽ motors, also work well as generators when driven by an external source of rotary shaft power. Hence, one can get electrical power out of a Power Functions M motor driven by a wind-powered rotor, as I've done here.



Available wind power

An HAWT's sole power supply is its swept power (Pswept) -- i.e., the mechanical power carried by an air stream of density ρ and undisturbed upstream speed U0 passing through the area Aswept swept out by the active (lift-generating) portions of its blades. Mathematically,

Pswept = ρ Aswept U0 3 / 2

The direct dependence on air density causes Pswept to fall off with increasing air temperature and elevation. Here in Denver (elevation 1,793 m), the air density is on average ~80% of the mean sea level value of 1.204 kg m-3 at 20°C.

The swept power's dependence on the cube of U0 means that a 50% drop in upstream wind speed cuts Pswept by a factor of 8. Finally, the dependence on Aswept means that halving rotor diameter cuts Pswept by a factor of ~4.

If we define the "hub" to include all aerodynamically inactive components at the center of the rotor, then

Aswept = π (D 2 - Dhub2) / 4

where D is the rotor diameter (taken as twice the tip radius R) and Dhub is the hub diameter. Putting it all together,

Pswept = π ρ (D 2 - Dhub2) U03 / 8

Clearly, low air density (as at my house), small rotor diameter, large hub diameter, and low upstream wind speed all reduce the wind power available to an HAWT. Of these factors, U0 and D are by far the most important, in that order.

At my HAWT's 8.2 m/s design wind speed, the "go" and "show" rotors have Pswept values of ~14W and ~28W, respectively. This wind speed occurs at a hub-to-hub distance of 0.30 m from the fan, as shown below.



Like all HAWTs, this one had to be optimized for a fairly narrow range of wind speeds around its design speed, as it's just not possible to make any HAWT equally efficient at every wind speed that might come its way. One must have detailed data on the diurnal and seasonal wind patterns at a particular site before ordering an HAWT to plant there.



Efficiency

Efficiency, one of the most important measures of performance in any wind turbine, can be broken down in several ways. One sufficient for our purposes follows.

Overall efficiency (ηoverall) is the ratio of input wind power (Pswept) to output electrical power (Pelec). Mathematically,

ηoverallPelec / Pswept.

Like any true efficiency, ηoverall is a number between 0 and 1. Overall efficiency can be factored into rotor efficiency (ηrotor), gearbox efficiency (ηgear), and generator efficiency (ηgen) like so:

ηoverall = ηrotor ηgear ηgen

Rotor efficiency (aka power coefficient, cP) is just the fraction of Pswept converted to mechanical shaft power at the rotor (Protor). Similarly, gearbox efficiency is the shaft power ratio across the gearbox. Finally, the generator efficiency is the fraction of input mechanical power Protor ηgear converted into Pelec.

For HAWTs, considerations grounded solidly in the conservation of mass, energy, and momentum set a firm upper limit of 59.3% on ηrotor. This ceiling is known as the Betz limit. No real turbine can reach the Betz limit, but rotor efficiency can approach 50% in modern megawatt-class HAWTs like the V90. If the reduction gears used in large ships are any guide, HAWT gearbox efficiencies are likely to exceed 90%. Explicit generator efficiencies are hard to come by for such turbines, but overall efficiencies of 20-30% are often quoted for megawatt-class HAWTs. If representative, the generator efficiencies must be around 60-70%.

My HAWT efficiencies aren't quite that good. With the "go" rotor, it manages an ηoverall of ~6%. Laughable, I know, but even that took a lot of doing considering the rotor and generator options I had to work with. A very conservative estimate of ηoverall for my 1-stage reduction gearbox is 97%. The efficiency of the M motor working as a motor closely approximates its efficiency as a generator within the same RPM range. That puts ηgen at around 22% and the "go" rotor efficiency at ~28%, or just under half of the Betz limit.

Rotors driven by aerodynamic lift (e.g., the V90 and my HAWT) are vastly more efficient and powerful than those driven by differential drag. The 3-cup anemometer below is a classic differential-drag rotor. Its maximum possible efficiency is a mere 8%.



Due to inherent limitations WRT the amount of aerodynamic lift and hence torque that can be generated by the blades of a vertical-axis wind turbine (VAWT), the large turbines used in commercial utility installations are invariably HAWTs.

Hence, the only places you're likely to see a VAWT "wind farm" of drag-driven Savonius rotors like the one below is in a kinetic art installation or a lecture on how to lose your shirt in the wind energy biz.





Blade geometry, lift, and tip-speed ratio

[coming soon]




HAWT specifications

General
Overall dimensions with rotor:0.60 x 0.28 x 0.26 m (HxWxL) including rotor disk and energy meter
Overall dimensions without rotor:0.51 x 0.18 x 0.26 m (HxWxL) including aviation light
Overall weight:1.095 kg (2.41 lb)
Hub height:0.460 m
Hub height above base:0.320 m
Tower height:0.334 m excluding base and aviation light
Nacelle dimensions:0.040 x 0.054 x 0.140 m (HxWxL) excluding aviation light
Construction:Studless
Basis:Vestas V90 onshore wind turbine (3 megawatts, 90 m rotor, 105 m hub height)
Scale relative to basis:1:247 in rotor diameter; 1:244 in hub height above base
Elevation:1,793 m
Air density:0.97 kg m-3
Wind source:240W floor fan, speed setting 1/3
Design wind speed:~8.2 m/s (~18 mph) at 0.30 m hub-to-hub
Overall efficiency:6% with "go" rotor
Yaw control:Manual via IR remote control
Yaw actuator:Large Technic turntable at base of tower with worm drive
Yawing motor:M
Yaw rate:~2 °/s with rotor at rest
Electrical power for yawing motor:7.2V AA battery box with externally charged NiMH cells
IR receivers:Single V1 for yaw control
IR receiver connections:1 for yaw control motor
Lighting:PF LEDs in aviation light atop nacelle and reading light above Energy Meter
Electrical power for lighting:Dedicated Energy Meter battery (charged by turbine generator)
Modified LEGOŽ parts:None
Non-LEGOŽ parts:None
Credits:Entirely original MOC


Gearbox and generator
Gearbox:Single-stage 3:1 reduction (rotor:generator)
Gearbox efficiency:95% (conservative estimate)
Generator:M motor driven by rotor
Monitor:Energy Meter
Electrical load:Energy Meter charging circuit
Generator efficiency:22% (est)


"Go" rotor
Source of torque:Aerodynamic lift
Mass:0.022 kg
Blade construction:Wind turbine blades (89509, LEGOŽ Education Renewable Energy Add-on Set, 9688)
Blade number:3
Tip diameter:276 mm
Hub diameter:8.8 mm
Disk area:0.060 m2
Swept area:0.054 m2 (excludes hub)
Swept wind power:~20 W
Blade camber:~5 mm
Blade area:~0.0033 m2
Total blade area:~0.0098 m2 excluding struts
Solidity:~16%
Rotational frequency:1,150 RPM
Angular speed:120.4 s-1
Tip speed:16.6
Tip speed ratio:2.0
Efficiency, rotor:28%
Efficiency, overall:6%
Generator shaft speed:282 RPM
Output voltage:4.5 V
Output current:0.19 A
Output power:~0.85W


"Show" rotor

Source of torque:
Aerodynamic lift
Mass:0.038 kg
Blade number:3
Blade construction:Paired #5 and #6 Technic long, smooth fairings
Tip diameter:368 mm
Hub diameter:[24] mm
Disk area:0.106 m2
Swept area:0.105 m2 (excludes hub)
Swept wind power:~20 W
Blade camber:~3 mm
Blade area:~0.0030 m2
Total blade area:~0.0091 m2 excluding struts
Solidity:~9%
Rotational frequency:847 RPM
Angular speed:88.7 s-1
Tip speed:16.3 m/s
Tip speed ratio:2.0
Efficiency, rotor:8%
Efficiency, overall:2%
Generator shaft speed:282 RPM
Output voltage:3.0 V
Output current:0.17 A
Output power:~0.5 W





Selected references
All can be found online, in most cases, free of charge.
  • Bottasso, C.L., Campagnolo, F., and Petrovic, V., 2014, Wind tunnel testinng of scaled wind turbine models: Beyond aerodynamics, Journal of Wind Engineering and Industrial Aerodynamics, v.127, p.11-28.

  • Gasch, R., and Twele, J., eds., 2012, Wind Power Plants: Fundamentals, Design, Construction, and Operation, Springer-Verlag (highly recommended)

  • Libii, J.N., and Drahozal, D.M., 2012, The influence of the lengths of turbine blades on the power produced by miniature wind turbines that operate in non-uniform flow fields, World Transactions in Engineering and Technology Education, v.10, p.128-133.

  • Mohammed, M.A., Fagbenro, K., and Wood, D.H., 2012, Computational modeling of circular arc airfoils at low Reynolds number, CFD Society of Canada, 20th Annual Conference, Canmore, AB

  • Nelson, F.C., 2007, Rotor dynamics without equations, International Journal of COMADEM, v.10, p.2-10.

  • Schubel, P.J., and Crossley, R.J., 2012, Wind turbine blade design, energies, v.5, p.3425-3449.

  • Swanson, E., Powell, C.D., and Weissman, S., 2005, A practical review of rotating machinery critical speeds and modes, Sound and Vibration, v.[May], p.10-17.

  • van der Tempel, J., and Molenaar, D.-P., 2002, Wind turbine structural dynamics -- A review of the principles for modern power generation, onshore and offshore, Wind Engineering, v.26, p.211-220.

  • Wald, Q.R., 2006, The aerodynamics of propellers, Progress in Aerospace Sciences 42:85-128 -- an excellent treatment if you have access and don't mind the heavy math.

  • NASA's FoilSim III Student Version 1.5a interactive online airfoil simulator. Among the available airfoil profiles is a curved plate simulation that sheds some light on the aerodynamic behavior of the Technic #5 and #6 long smooth fairings when used as prop blades.

  • LEGO® 9V Technic Motors compared characteristics by Philippe "Philo" Hurbain, the undisputed guru of all things electrical in the LEGO® realm -- especially the motors.






Comments

 I made it 
  March 11, 2017
Quoting Family Vuurzoon Great working construction! Especially like your new rotor blade design.
Thank you!
 I like it 
  March 10, 2017
Great working construction! Especially like your new rotor blade design.
 I made it 
  August 21, 2016
Quoting Sven J. Absolutely fantastic work on this one in design and technology. Your rotor blade design is great! Maybe something what I try for my own stuff ;)
Too kind, Sven! Looking forward to seeing what you come up with.
 I like it 
  August 21, 2016
Absolutely fantastic work on this one in design and technology. Your rotor blade design is great! Maybe something what I try for my own stuff ;)
 I made it 
  January 9, 2016
Quoting Family Vuurzoon Fantastic Jeremy! Great design: looks AND technology. I'm pleased that I'm not the only maniac writing down physic equations on MOCpages ... We certainly share a passion for engineering. Regards,
Thanks, FV! Well, you know what they say: The only thing better than LEGO is LEGO with equations! ("They" being you and I and one other guy.)
 I like it 
  January 7, 2016
Fantastic Jeremy! Great design: looks AND technology. I'm pleased that I'm not the only maniac writing down physic equations on MOCpages ... We certainly share a passion for engineering. Regards,
 I made it 
  November 16, 2015
Quoting Jack Sparrow I had to check out more of your stuff. LEGO has come a long way, mixing Radio Shack-like learning elements in with the super fun LEGO we know. This is another good example of what we can learn from practical experimentation. I'm impressed that you can generate nearly a watt of DC power with your design. That's pretty efficient, considering it's LEGO pieces doing all the work. Great job!
Sorry I missed your generous comment, Jack. I'm definitely a hands-on learner. That 0.85 W from the "go" rotor was hard to come by. The "show" rotor became shrapnel many times in the course of trying to coax more power out it. Not a word to my wife about the nicks in the walls!
 I like it 
  August 14, 2015
I had to check out more of your stuff. LEGO has come a long way, mixing Radio Shack-like learning elements in with the super fun LEGO we know. This is another good example of what we can learn from practical experimentation. I'm impressed that you can generate nearly a watt of DC power with your design. That's pretty efficient, considering it's LEGO pieces doing all the work. Great job!
 I made it 
  July 25, 2015
Quoting Topsy Creatori The power of your enthusiasm, engineering design and analysis has swept me away! Just visited the Wa/Or border where I saw lots of turbines gracefully sailing! :)
Very kind words, Topsy. I'm just a sucker for gizmos that turn out to be way more complicated than they look. That's why I love LEGO powerboats as well.
 I like it 
  July 25, 2015
The power of your enthusiasm, engineering design and analysis has swept me away! Just visited the Wa/Or border where I saw lots of turbines gracefully sailing! :)
 I made it 
  March 11, 2015
Quoting Tom C That is a wonderful project. Are the blades (not the fairings, the Mindstorms Blades) still available? I have been doing some projects of my own and like to have multiple sources to test from. Thank you.
Thanks, Tom. Yes, LEGO Education still sells the one and only set the blades come in (LEGOŽ Education Renewable Energy Add-on Set, 9688) for $100. Anyone can buy from them. Among other things, set also includes an Energy Meter (good for measuring voltage, current, and power without disturbing the system) and an E-motor. Last I checked, the cost of 6 blades on BrickLink almost paid for the set.
  March 9, 2015
That is a wonderful project. Are the blades (not the fairings, the Mindstorms Blades) still available? I have been doing some projects of my own and like to have multiple sources to test from. Thank you.
 I like it 
  January 23, 2015
I'm impressed. If it produces more power than the fan supplying the wind uses then I'd be extremely impressed! Very nice work.
 I like it 
  January 16, 2015
Like a modern day Da Vinci. Well done.
 I made it 
  January 14, 2015
Quoting Nerds forprez Jeremy, Are you part of the eurobricks community? Your posts may gardner more attention there than MOCpages. This site is great, but typically not as many technic-minded folks compared to other genres. I think that some of your posts would be great for eurobricks.
Nerds, Thanks for that thoughtful advice. I'm a Eurobricks member but haven't been active there. I'll have to change that.
 I like it 
  January 13, 2015
Jeremy, Are you part of the eurobricks community? Your posts may gardner more attention there than MOCpages. This site is great, but typically not as many technic-minded folks compared to other genres. I think that some of your posts would be great for eurobricks.
 I made it 
  January 10, 2015
Quoting Henrik Jensen An incredible article on wind turbines, you are really pushed by your passion for engineering. I like it when the displayed creation comes with a little information about it , but a close study of your creation requires plenty of time.
Henrik, Thank you. Yes, way too much time for the passing visitor, I'm afraid, but perhaps valuable as a reference to aspiring wind turbine builders. I try to provide many different views for those who prefer photos to words.
 I like it 
  January 10, 2015
An incredible article on wind turbines, you are really pushed by your passion for engineering. I like it when the displayed creation comes with a little information about it , but a close study of your creation requires plenty of time.
Jeremy McCreary
 I like it 
Matt Bace
  January 9, 2015
Wow! One can certainly learn quite a bit by reading your write-ups. This is some great engineering work. Do you have any larger plans for these builds?
 I made it 
  January 9, 2015
Quoting Walter Lee Nice write up. In addition, the custom airfoils-blades is great design idea because the increase the length of the blade increases the efficiency of the power generated by the blade. Blade configuration of similar surface areas and attack angles output the same torque/power per revolution but airfoils blades that are longer are more energy efficient - which is why most aircraft use two or three blades props over four to six blade configurations. Helicopter airfoils also exhibit the same design trade off. By lengthening your airfoil - you have made the wind turbine much more energy efficient.
Thanks for the kind words and discussion. Totally agree with your observations, but there's a catch here. I also thought long, slender blades would always be better and really wanted the DIY blades to bear that out, but that turns out to be true only for rotors with tip-speed ratios (TSRs) above 2.5. My TSR is only 2, and in that low-TSR regime, fan-like blades like those on the "go" rotor are more powerful =and= more efficient. The extreme case is the classic ranch windmill of the American West -- many fan-like blades nearly filling the rotor disk, TSR = 1. Very efficient, too. In contrast, long, slender blades tapering toward the tip are way more powerful and efficient on a rotor like the V90's, which has a TSR of 4.7. Most big commercial HAWTs have TSRs at least that high nowadays, and airplane props have TSRs much higher still.
 I made it 
  January 9, 2015
Quoting Verticus Akkron Very nice! I am certainly a fan of Lego wind turbines, and this does not disappoint! Great attention to detail, and you certainly know technic. That's not something I specialize in, but you obviously do. Well done, sir!
Verticus, Thanks for the kind words. I added my support to your wind turbine on LEGO Ideas -- great choice of blades evoking the new and the old in HAWT technology.
 I made it 
  January 9, 2015
Quoting Matt Bace Wow! One can certainly learn quite a bit by reading your write-ups. This is some great engineering work. Do you have any larger plans for these builds?
Matt, thank you very much. No plans for another wind turbine, as I just ordered a Vestas V90 for the backyard. Can't wait to see the wife's face when the big cranes show up!
 I made it 
  January 9, 2015
Quoting Gabor Pauler Very educational MOC and description! It could be course material in basic science class...
Gabor, thanks a lot. I love complicated stuff like this, and I love torturing others with it, too. It's a character flaw.
 I made it 
  January 9, 2015
Quoting Yann (XY EZ) Fantastic creation! Well done!
Yann, thanks again for the encouragement.
 I like it 
  January 9, 2015
Nice write up. In addition, the custom airfoils-blades is great design idea because the increase the length of the blade increases the efficiency of the power generated by the blade. Blade configuration of similar surface areas and attack angles output the same torque/power per revolution but airfoils blades that are longer are more energy efficient - which is why most aircraft use two or three blades props over four to six blade configurations. Helicopter airfoils also exhibit the same design trade off. By lengthening your airfoil - you have made the wind turbine much more energy efficient.
 I like it 
  January 9, 2015
Very nice! I am certainly a fan of Lego wind turbines, and this does not disappoint! Great attention to detail, and you certainly know technic. That's not something I specialize in, but you obviously do. Well done, sir!
 I like it 
  January 9, 2015
Very educational MOC and description! It could be course material in basic science class...
 I like it 
  January 9, 2015
Fantastic creation! Well done!
 
By Jeremy McCreary
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Added January 9, 2015
 


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