I need help designing 17' multiblade.

[Timeless Turbines]

   I Love this site, been reading it for a year or more, I have read the home brew book twice. I have a michigan master electrican lic. and I am the Group Leader Electrican at Eastern Michigan University, Our College Of Technology students will be helping me build my 17 footer.  I bought an old 45' four post windmill tower, had it delivered to my back yard. Ten neighbors helped unload it from a trailer. A week later my home owners association sent me a letter stating that I needed to ask for approval and met Township and County codes. I was denied by the Township because they we uneducated on the matter. 9 mo. later they were ready to take applications. They will only allow me to have max height of 55'. I have a friend who has a business restoring old windmills, has assures me that the tower I have will support what I am going to build and that the old windmills had gear boxes that weighted 500lbs and had large diamiter multiblade setups.

   My tower is 40' to the top, I had to cut 5' off the top so that I could weld up a 16" square top. I made it with 3" square x 1 / 4" double weld, it has a 10" hole throuh the center to allow a mast to stick out the top and support the turbine. Right know I have an Air Brease 24v 4' diamiter turbine on it.

 I Thinking that if I had six 8.5' blades it will be exposed to twice as much energy and may would reach peak safe output at a lower wind speed than the three blade model. I know that it would be turning slower because it has 6 blades. I think I would have to build a larger generator to make up for the slower rpm. I dont know how big to build the generator.

   I could still have the multiblade look with five blades, I think the closer I stay to your plan the better but I dont mind shelling out an extra $1000.00 for the generator if it could produce more KWHs per year.

   My goal is to make an Obscene amount of electricity, but I am limited on cash and height. I am ready to spend six thousand on the turbine. I have 30 100 lb lead acid deep cycle batterys and two, two inch pvc conduits to the tower. The tower is two hundred feet from my electric closit. I am planing on keeping the batties in the basement next to my electric room. I plan to buy a grid tie inverter.

   Has anyone been successfull with a multiblade.

[ghurd]

Sounds interesting!

"if I had six 8.5' blades it will be exposed to twice as much energy and may would reach peak safe output at a lower wind speed than the three blade model"

Nope!

Design the blades to match the quantity of blades.

More is slower, making the PMA more expensive, but the potential power is basically the same.

TSR is something you should read up on.

If you go with a lot of blades, there is something about harmonics that I can't recall, but a prime number of blades is best.  5 or 7 is better than 6.

Might find something interesting here,

http://www.windmission.dk/turbines/turbines.html

Might find something interesting in dlenox's posts too.

The concept of grid tie can get a bit overwhelming.

MPPT without batteries, MPPT with battery back up, battery voltage based that sends the 'extra' to the grid, etc.

Probably want to study that a bit more before completely designing the PMA.

Funny it takes them the same length of time to get ready to take applications as it takes to make a brand new human being from scratch.

G-

[Timeless Turbines]

   Love the comparison to Making a human being. Its been a while sence I have read the Home Brew book but they stated in the book, the same relation ship does exist, more blades more power but more expensive generator. Iam planning on that and five blades is great it will still look like a multibade. I have alot to learn yet but a gridtie inverter seams rather straight forward, feed it DC set some voltage levels. What do the letters MPPT stand for.

  Thanks so much.

Larry

[ghurd]

Maximum Power Point Tracking.  

Probably a bit of an overstretched misnomer at this time, depending on who you ask, and the sales brochures you choose to believe.

The whole TSR and cost for the PMA thing gets dang complicated, real fast.

Fast blades is a cheaper PMA, roughly speaking.

"feed it DC set some voltage levels"

Yup.

Could go with 12V or 200V or almost anywhere in between.

So what voltage do you intend to feed it?

Not than I can be much help with that, but it is something to consider from here on out.

You have entered the twilight zone?

Everything is a trade off.

Can get more volts with less amps.  And vice versa.  And all the undefined gray areas is were this stuff operates.

I do not intend to be a party-pooper.

You have the bucks, skills, and background to get it done.

Be ready to re-learn a few things pertaining to electric in this context.  Very little about wind is an absolute fixed value.

G-

[Timeless Turbines]

  When I talked to one of the teckies at Windyboy they recomended winding it for 240 volt DC, I think it makes good sence to me, lower amps saves money for wire, Iam useto working with 250v and 480v systems at work we like to stay away from VD. I am a little shy to venture away from the proven 48v systems that are shown here. I do tend to like Dan Lenoxs setup, looks like he built tough.

 Thanks so much for Time.

  Larry

[Perry1]

I would recommend against building a 5 bladed setup. You state your desire in doing this is because it would look cool. Yes it would but but you will be sacrificing performance and end up paying more. You have to resist design traits that look cool but diminish performance. You also state that your intent is to make motherloads of power. I think the 5 bladed setup will take you away from that.

I'm not sure if you've built a turbine before but a 17 footer with a custom design is a pretty ambitious project. You might want to build the 10 footer straight out of the book first. You can use it as a test turbine as you flesh out the rest of the system. That's what I did and it worked very well. Then move up to your 17 or whatever you decide you want. A good running 10 footer can perform better than a mismatched 17.

Sounds like you have a good tower, I'm jealous.

Perry

[Timeless Turbines]

   Thanks for your input.

Iam not shure what the trade off is right now. I am ok with a 33% increase in cost for the five blade set up, it might also be insurance against burnout due to overheated stator. If the generator is larger and still getting same output as 18" rotor ther would be more winding to displace the heat ?. I do tend to jump right in to things. I have not built a turbine yet. The mulitblade turning slower could be quieter, I live in a small subdivision out in the country. It is a Michigan Land Conservancey, we 24 homes own 150 acres, we each get one acre each to build on and the rest is deeded farm land, we lease the land to a local farmer. So I have 23 other home owners that can say its an anoiance, . Appearance is very important. A multiblade will be much more accepted.

   Thanks for your thoughts.

Larry

[erne]

If you look in my photos you will see my 24 foot multi-blade turbine. these mills were designed to produce in lower wind conditions and at much lower rpm's. If you have low winds the multi-blade will out perform a 3 blade. You increase the torque. You will need gearing tho. You can air switch multiple smaller alternators and increase your output  as the wind increases. The multiple blades increase your solidity which govern the rpm's. In low wind only one alternator produces. As wind increases others start kicking in. there is a hp chart there also for multi blade Aero-motors. Good luck.

[Timeless Turbines]

   Thanks Erne

I will be looking into your stuff soon.