WindyNation's Complete Wind Turbine

Ben,

Please understand I appreciate all of the hard work you do to provide this forum, and at the end of the day it is YOUR forum and you need to do what you think is best; no arguments from me on that. It just seemed to me like Windy Nation was getting an unusual reception for what looked to me like pretty good test videos. I do understand being leery of people with commercial interests and spammers in general, but this hobby really does need some people who can provide kits and bits to those who want to play but do not have a full shop at their disposal. Sorting out the scammers from the honest ones is a difficult task, and I have no first hand knowledge of Windy Nation either way. I simply thought the act of sharing some of his prototype testing was refreshing, particularly for someone with commercial interests.

Windy Nation,

7.7ft diameter. If your output is ~500W @ 27mph this implies an overall cp of ~0.113. This is perhaps the most "honest" cp I have ever seen associated with a commercial interest small scale wind turbine. If the cp is constant (which it NEVER is) this implies 85W @ 15mph and 13W @ 8mph. On the list of tests you might consider is plotting your overall cp at numerous wind speeds from cut-in to furl and work on maximizing the cp in the 12mph-18mph range. If you could get the overall cp up to ~0.25 @ 15mph you should see ~189W from 7.7ft diam blades. Even if your cp drops linearly from 0.25 @15mph to 0.05 @ 27mph you would be gaining a great deal of actual Wh in areas that simply do not have sustained 27mph winds (most of the world). Improving the overall cp is a tricky thing, as I am certain you are aware, but sacrificing high-wind performance for a higher output at more reasonable wind speeds is really worth spending some time on.

Following is a table of RPM for various TSRs / Wind Speeds:

  Code:

     Radius   8    12    15    20    30    50    80
TSR   Feet   MPH   MPH   MPH   MPH   MPH   MPH   MPH
8     7.7    116   175   218   291   436   727   1164
7     7.7    102   153   191   255   382   636   1018
6     7.7     87   131   164   218   327   545   873
5     7.7     73   109   136   182   273   455   727
4     7.7     58    87   109   145   218   364   582
3     7.7     44    65    82   109   164   273   436
2     7.7     29    44    55    73   109   182   291
1     7.7     15    22    27    36    55    91   145


Obviously real-world TSRs are NOT constant across variable wind speeds, and are ultimately greatly affected by loading, but a bit of blade testing should give you some clues to the TSR range at a given wind speed. In order to get "peak" output at a certain wind speed, you need to determine the most efficient TSR loading at that wind speed, then design your alternator to reach its peak efficiency @ that RPM. For a hobbyist this "recursive approach" to a final design is typically too much work, but for someone with commercial interests, this methodical approach will yield a far superior product. You might even consider offering two or more alternator configurations for any given set of blades. Obviously you might need to offer different furling options as well.

Most commercially available turbine bits/kits tout their specs @ 10m/s-15m/s (22mph-33mph) wind speeds while most people live in areas with typical wind speeds in the 5m/s-9m/s (12mph to 20mph) range with only occasional 25mph to 35mph winds. While 500W to 5kW claims are rampant in marketing literature, there are very few places windy enough to ever see these outputs. Getting 200W from a more typical 15mph wind with furling occurring in 25mph to 30mph range would serve people much better. Designing an alternator to reach peak performance in the 100rpm to 300rpm range is a bit more challenging than designing an alternator to reach peak performance @ 600rpm to 1200rpm, but the investment in time will greatly improve the total realized power from the turbine. Of the two methods to maximize alternator performance in the 100rpm to 300rpm range (gearing, increased magnet count), increasing the magnet count is the more efficient (IMHO), but you should consider both methods.

Anyway, I look forward to reading more about your tests, and hope that others here will help you on your way to turning prototype into product.

Fish

WindyNation
Though shipping costs to UK (and the fact that I enjoy DIY messing about too much!) will probably mean there's little chance of me buying one of your finished products, I also wish you well and look forward to hearing more.

PS - I agree with Fish, sacrificing the capability to extract more out of occasional high winds in order to regularly get more out of normal low winds would be a very good move. Careful marketing though to make the point against the "2KW from a 7ft prop" brigade!.

Agree with others comments, what is import is kWH not max kW rated output.

I would certainly look toward improving the lower wind performance - although this may be difficult if using an off the shelf generator. Enjoyed the videos, thanks for taking the time to post them. Hope that you have had some useful ideas for improvements, I look forward to your next video.

I have taken some time and looked over Windy Nation's website in more detail. The alternator he is offering for $275 looks like a high quality unit optimized for wind turbine performance. He shows a graph of power vs wind speed that I assume gives some insights into it's performance with his 35inch blade system, and it appears he has done a fair amount of homework, though there is no indication if the graph represents the three blade configuration or the five blade configuration. Extrapolating his system's (blades/PMA) performance from the graph indicates the following:

  Code:

Wind                   Implied
Speed      Power      CP
10mph     120W       .48
15mph     270W       .34
20mph     415W       .22
25mph     490W       .13



It would be better in judging his PMA if he had simply given a graph of RPM vs Amps @ 24V, but I have no doubt he has that information and would share it. It does state that the PMA achieves 12V/90RPM, suggesting a "cut in" speed of 180RPM for a 24V system, and also suggesting a TSR of 14 @ ~7mph (unloaded "cut-in"). From the extrapolated data it is obvious he has taken a great deal of care to optimize the blades/PMA for low wind speed performance, and if I had to guess this test data is with the five blade system. Achieving 120W from a 46.56sqft swept area @ 10mph is VERY impressive. Likewise, achieving over 80% of name plate output @ 20mph is also VERY impressive. If we assume a 24V load will hold the RPM of his blades to ~180RPM (not actually a valid assumption, but a good first order approximation) his TSR curve should look something like the following:

  Code:

Wind
Speed   RPM    TSR
7mph    181    14.2
12mph  181      8.3
15mph  183      6.7
20mph  183      5.0
25mph  182      4.0
27mph  182      3.7


It is the 14.2 TSR @ 7mph that makes me believe this power curve is achieved with the 5 blade system.


The rather obvious investment in tooling to make his blades and PMA suggests a long-term commitment to quality construction that I just have not seen much of in the hobby sized commercial offerings.

I have not had any dealings with Windy Nation, nor have I had any contact with him other than in the thread in this forum, but I must say from the information garnered from his web site, it appears he is working very hard to make a high quality, affordable hobby sized system. It also does not appear he is making exaggerated claims of performance based on 35+mph winds. His system appears optimized for exactly the conditions most people are likely to experience. His five blade system with hub, alternator and blades is under $500. This is only slightly over $1/potential Watt, a pretty reasonable price. (Obviously the rest of the system (Tower/Tail/Furling/Controller/Rectifier/Etc) will raise the price considerably, but that is true with any system.) If he ever decides to scale his turbines up to the 6m/4kW or 9m/9kW size, I would seriously consider it. Assuming his design could scale performance with swept area, a 6m diameter should produce ~0.766kW @ 10mph, ~1.8kW @ 15mph and ~2.8kW @ 20mph; and a 9m diameter should produce ~1.7kW @ 10mph, 4.1kW @ 15mph and 6.3kW @ 20mph. The alternator would have to have twice the poles to achieve the same 24V at 90 RPM in a 9m system, and there would be many other problems with simple scaling, but it sure sounds fun :-)

If someone has a need for 100W to 400W in an area with 10mph to 20mph winds, I would suggest looking carefully at this system. It appears to me this person has invested a great deal of time and effort with his products, and the prices seem quite reasonable.

Fish