20' Diameter Windmill - Grid Connected

[ghurd]

Because you were typing while I was typing.

G-

[TomW]

Bob;

First, I want to make note and commend you for responding to most of the comments. That is often not the case.

I found the pool boiler heat sink quite interesting and innovative in this application. I think they use something very similar on the Alaskan pipeline to keep the warm oil from thawing the permafrost around the piers that support it.

I can see where it would be very useful on higher KW machines.

That may be an interesting little cottage industry product for the DIYers.

I think you may have simply astounded many with this project and the full scope has not sunk in yet.

Wish I had the skill to do even some of what you have done.

I fully agree on hobbies turning into work when it becomes a business.

By sharing you return much of what you may have taken from the forum. Thats what makes it work. The sharing.

Thanks again!

Tom

[hvirtane]

Really beautiful workmanship.

Thank you a lot for sharing this project.

Which kind of plywood did you use as the core of the blade?

Do you have more pictures about making the blades?

- hv

[SparWeb]

Thank you Bob for the extra info.  Very much.  Obviously a lot of thought and work has gone into this one.  You also bring a lot of skill of your own, which makes this unique.

It sure sounds like you're gearing up for mass production.  Steel molds means that interchangeability and repeatability is solved and you just need to hire a summer student to start pumping them out!  I wish you worked in my company's shop.

Your tail's angles are noticeably different from the angles typically used by Dan B kits.  This will be interesting to see compared to other windmills.  Off hand, the increased angles seem to make furling occur late, but the tail is very big and light, which encourages furling at a low wind speed.  Let's see if plugging numbers into my table is able to make a prediction of the wind speed at which your windmill does furl.

Wait... don't tell me... I'm gonna guess...

[jmk]

 Nice turbine, great work, and thankyou for posting!

[Jacktown Willie]

Wow! Your work is truly impressive. Would love to see more pictures and descriptions of the coil fabrication and blade construction. Thanks for sharing your ideas and construction details.

JTW

[Jon Miller]

I am!

Its nice to see a home made one.

I have used smaller computer phase change heat sinks before, bobs one is on a different level though.

cant be that much heat to lose via the heat sink?

Regards

 

[bobshau]

Jonathan,

You asked: "Do you think the addition of marble dust to fiberglass resin would help compared to not adding any solid agent at all?"

Yes. The marble dust has a higher thermal conductivity than the resin and will improve the overall thermal conductivity of the composite  mix. The amount of improvement will be a function of the quanity of dust that is added. I add 33% of the volume of Part A for the high temperature epoxy.

Hugh uses talc power in his fiberglass resin mix. This also will improve heat transfer properties.

Blessings and peace,

Bob S

[bobshau]

Thanks to everyone for their kind remarks.

At the request of some, I plan to submit seperate postings describing the procedures for making the coils and the blades. Please give me a couple of weeks or so to get them together. Spring is almost here, time to get the garden ready for planting onions, etc. I plan to start seeds in the greenhouse in a week or two.

Blessings and peace,

Bob S

[Dave B]

 Great work, you have built what you wanted for your application and that's what counts. I see the advantage to your stator design if you have trouble with heat or physical damage needing to replace coils.

 I would think that with your possibly lighter tail arrangement you could avoid overheating by starting first with early furling then possibly adding weight as you go still keeping things safe but to dial it in for a bit more power.

 If your stator is rigid enough and with a reasonable gap you should have little trouble with scraping the rotors. If you do have problems you have designed a bit more service friendly and possibly cost effective way for repairs.

 Great to see inovation and thank you for posting your project.  Dave B.

[SparWeb]

Hi again Bob,

Hope you get to see this question (threads tend to disappear off the main page after a while and unless you go looking for it, you can loose track of threads, even ones you post yourself).

As I was analyzing your data, I see that you have excellent performance:

  ... 3600 watts out of inverter in a 20 mph wind. (6100 watts generated)....

Is this worded as 3600W electrical output, meaning that 6100 W would be the mechanical power input?  That's a nice 59% electrical efficiency, following from a 48% aerodynamic power coefficient.  These are simply excellent numbers, so I can't believe that you haven't built a few windmills before.  I can see your anemometer in the background of your picture, close to tower height, so I accept the wind speed figures, too.

Can you tell me your altitude above sea level?  I want to account for air density because my windmill suffers from 90% the air density available at sea level.  The Dans put windmills up at 5000 feet altitudes and get good performance, so imagine how those would do at sea level.

The reason this came up is that the proportions of your mill don't match the trend I found by comparing other windmills.  I will post more info when I have it in a "presentable" form.  I also want to double-check because I could have made a mistake.  Frankly I am intrigued, so I hope it doesn't impose too much if I ask more questions in the future.  

Thanks again

[SparWeb]

Here's an update to the comparison table:

http://www.sparweb.ca/Wind_Turbine_Comparison.htm

Bob let me know if any of the figures are wrong.

[Dave B]

Steven,

  There has been and I think always will be the debate on offset side VS. direction of blade rotation. (Hugh has recently changed his) and I think it would be interesting to see these stats also. Also, you briefly mention the load with respect to furling. I have experienced both of these variables to be extremely important to the overall furling performance.

  Certain figures seem to get you in the ballpark of repeated design and application but mess with the recipe just a bit and you have created a different machine. No longer an apples to apples comparison which confirms your compilation of rough data.

  Interesting for sure and I think it's great you have taken the time to put this information together. Thanks for that,  Dave B.

[SparWeb]

You're right - I never got around to noting the directions.  All of the information was available, and now I've it together.  I'll upload the update to the same link shortly.

Right now there's getting to be too much information to make sense to the casual reader.  I will still add more info as it becomes available, but eventually the table must be simplified down to the most esssential data, or else it's no help.

[bobshau]

Hi Steven,

It is difficult for me to measure wind velocity and power simultaneously, especially during the gusty conditions that prevail here. It seems that we rarely get a nice steady breeze where I can get some decent measurements. The windmill speed and power always lags windspeed because of blade and rotor inertia.

Non-the-less, I have taken measurements in the past when the tail was heavy enough not to furl at wind speeds under 20 mph +-.  The measurements consisted of windspeed and "sell RE power" out of the Outback plotted with a curve fit through the mean of the scatterd data. These plots were used to validate my steady state computer model which is based on first principals.

The 3600 watts is the rated output power of the inverter and occurs around windspeeds of 20mph. It is not uncommon to see transient power levels in the 4000 watt range as the windspeed moves through 20 up to 30 mph as the windmill furls.

I used the computer model to back out the 6100 watts generated. It accounts for all the losses between the Outback and the generator. So I guess this represents the mechanical power delivered to the generator shaft.

Here are some of the output of the calculation for a 20.5 mph wind:

R of 4 coils in series at winding T+wiring R's=    0.207    ohms   

         calculated winding temperature=    150    C

calculated generator speed =    235 rpm                   

Peak Voltage per coil=    12.76    volts   

RMS voltage per coil    9.0    volts

RMS Voltage per Phase=    36.1    volts       51.0    Peak

Voltage across phases  

      w/o winding loss    62.5    volts       88.4    Peak

Voltage across phases

     with winding loss    27.0    volts       38.2    Peak

RMS  Current per phase=    57.1    amps       

DC amps:bridge rectifier to Inverter=       75.3    amps       

Generated power =              6181    watts   

Power into inverter

  including 3 ph ac line R's    3916    watts   

AC current out of Inverter assuming 92% eff    27.7    amps(130vac)   

169    watts/coil

Power out of inverter            3602 watts

Pwind     8835    ft. lb./sec

    11984    watts


operating Coef of performance     0.516   

Operating Tip speed wind speed    8.19                           

Torque from all phases = 3*K2*pi*Ia=    185    ft. lb       

Steven, we are at about 400' above sea level.

Keep the questions comming.

Blessings and peace.

[SparWeb]

This is very helpful.  If you've taken a peek at my summary table, you can see that I've found roughly the same conclusions by back-calculating from the data you provided before.  Interesting differences, such as your estimate of the raw wind power (11,894W @ 20.5 mph) compared to what I came up with (13,779W @ 20 mph).  Aw, close enough!

...It is difficult for me to measure wind velocity and power simultaneously...

Don't we all know how difficult this is.  Either you go to a tremendous effort to mount the anemometer in a location so close to the windmill, to get the most immediate data, but it becomes subject to effects from the windmill itself, or you locate it out of the windmill's "shadow", but at the cost of the lag between the cause and effect.

I'm out of questions for the time being.  It's only fair that I put the answers given so far to use before asking for more!

Oh, well, maybe just one...

If that's an Outback 3648, isn't it maxed out by the windmill?  Is there any margin for those surges?

[bsafe]

I am in awe of the entire set up, good work!

Let me be the first to ask you about the acetone heat pipes. Did you build or buy them? Could you share construction ideas and thoughts for those wishing to use/ build them.

I am interested in using them for refrigeration in the winter (moving heat from the inside of the refrigerator to the colder exterior of my house).

Great job, Bsafe

 

[bobshau]

Thanks for your kind remarks.

I built the acetone heat pipe pool boilers.

You mentioned that you were going to transfer heat from a refrigerator to the outside during the winter. Note that acetone is not a good working fluid for this temperature (40F). It has too low a vapor pressure to transfer any significant heat.

Unfortunately, ammonia is about the only working fluid available for this temperature range.   Filling and venting is much more complicated because ammonia has a high vapor pressure at room temperature and is toxic.

If you want to pursue ammonia heat pipes, get a copy of Dunn and Rhea, "Heat Pipes" and be carefull. You will be working with pressure vessels. Also, find a partner that has experience with these processes. Note that finned copper tubing is not compatable with ammonia. You will need to find finned ss or 1100 aluminum.

Blessings and peace.

Bob

[SparWeb]

Here is an update to that table (the other link may be broken):

http://www.sparweb.ca/Forum/Wind_Turbine_Comparison.htm

[okwindpower]

Bob, I have been reading over and over your build, and I am very impressed with your fabrication skills.  You are obviously a notch above the average builder.  Some of the ideas that you have developed were in fact bouncing around in my head as well, but never got so far as tooling up.  I have on the design board, the beginning of the cad drawings for a 24 volt genny of similar size to the one that you built.  I am stuck on 24 because I alread own an Outback grid tie inverter like yours, only the 24 volt version.  Unfortunately, the lower voltages are going to cause me some greif in getting large enough wire in the coils to handle the current.

I absolutely love the seperat coil feature that you fabricated, and wonder if your molds would have a large enough cavity for me to get my 24 volt winding in them?

If there is an email addy that I can coespond with you, I woulld apprecite it, you can maile me windpower at pldi.net

Thanks for all that  you have done and shared with us all, and give yourself a pat on the back.

Mike

[Madscientist267]

No doubt!

Somehow (still can't figure this out), I missed this post when it was in it's prime!

Absolutely, this is a very impressive example of how far the DIY thing can go.. I particularly like the part about "" LOL Talk like that does something deep inside... hahaha... makes me want to scrutinize everything and give it a brother it doesn't know about, but unfortunately, I am in a more or less wind-defunct area; I'd start making plans if I wasn't!

Excellent job dude - Lots of good stuff in there, and a severely nasty output for a homemade rig... to me, anything over 2 or 3 KW in DIY is impressive, but 6?!?

and

"" - This sounds like a serious problem... Time to build another one!!!   >X~P

Steve