Author Topic: 10kw blades (Read 3828 times)

cawest · « **on:** November 14, 2007, 07:51:42 PM »

Wind turbine project specs: 15hp 3ph 4 pole induction motor/gen. 17:1 helical gear reducer, microprecessor rpm controller. According to one formula, I could harvest almost 10kw at 22mph with a 28ft diameter rotor. Using a TSR of 5, and three blades, the cord width at the tip will be about 1ft. I need the rotor to turn about 105 rpm to spin the generator to 1818 rpm (1% slip). I live in the panhandle of Texas, wind class 3-4. I plan on using the DanB method of blade carving, using laminated cedar 2x4's. Am I on the right track with my three blade design? Or should I use a lower TSR with more blades to ease start up?

wdyasq · « **Reply #1 on:** November 14, 2007, 05:19:59 PM »

The handy calculator on the IRC forum gives:

33331.4 watts possible from 28.0 ft dia prop (615.5 sq ft) in 22 mph wind (density of 1.225000), 5333.0 watts output assuming generator is 80% efficient and Cp of 0.20.

-------

I suggest several things, the first is to start small and learn a bit. After that, you may be ready to listen to something else.

Ron

DanB · « **Reply #2 on:** November 14, 2007, 06:45:57 PM »

I have to agree. I don't always take the most high-tech approach - I like simple things and hope for reliability. I've been messing this (a few days/week) for years and the thought of a reliable 10kw machine (10 kW in reasonable winds) seems daunting.

HomegrownPower · « **Reply #3 on:** November 14, 2007, 06:46:21 PM »

Cawest

Wish I had a few corses under my belt I'd just flip you out the answers lol . Dan B made a 20 footer (I think) says he's still scared of it lol or it scares him or something like that .

Dan and others should be able to give you some good advise concerning blades you can use

Lonnie

cawest · « **Reply #4 on:** November 15, 2007, 11:30:23 AM »

I can understand your thought about starting small. The reason for the 10kw turbine stems from several reasons. A 10kw generator should produce enough energy annually to offset the energy used in my house (any typical house consuming 2000kwh per month). Anything bigger would be overkill for the typical home, and anything smaller would not meet the typical demands. The cost of the infrastructure (pole, gin pole, anchors, guy wire, gear reducer, wire, etc,etc,)would be the same for a 1kw turbine as it would be for a 10kw turbine. My initial thought was to use a 30hp generator, but after putting pencil to paper, it just seemed too big for the task at hand. The formula I used to predict power output was P=Cpxrho/2xPi/4xD^2xV^3.

Where Cp=.15 rho= 1.22 D=8.54(28ft) V=9.8(22mph)(from windstuffnow.com)

I know different formulas will give different answers to the same question. I tried using the calculator page on Alton's web page, but the numbers generated were quite different from the numbers I got using formulas from other web sites. I know I am asking for a simple answer to a complicated problem. I want the rotor to run up to 105 rpm as quickly as possible in as light as wind as possible. Using the formula for TSR=rpm x PixD/60/V where RPM=110 D= 8.54(28ft) and V=10(22mph) then the TSR will be 4.96, but if I change the V to 4.46(10mph) the TSR changes to 11. Does this mean that if I want the rotor to reach 110 rpm in a 10mph wind the TSR will have to be 11?

TomW · « **Reply #5 on:** November 15, 2007, 11:37:54 AM »

cawest;

The reason for the 10kw turbine stems from several reasons. A 10kw generator should produce enough energy annually to offset the energy used in my house (any typical house consuming 2000kwh per month). 2,000 KWH / Month is obscene.

Damn, man. First thing you MUST do is conserve. We have an all electric house and only use about 300 KWH a month.

Start at the beginning, man.

Much easier to conserve a KWH than to make one.

Might want to back up the train a bit here, do some research, do some energy conservation and get a clue how to pull it all together.

Just one view and likely held by anyone who knows this stuff.

Cheers.

TomW

DamonHD · « **Reply #6 on:** November 15, 2007, 12:01:54 PM »

We cut down a few months ago from ~1000kWh/month for my home and office to ~200kWh/month.

As Tom says, the best and first thing you need to do is cut waste and conserve. It's cheap and simple and safe and very effective, even if dull.

Have a look at my dull page about this dull subject for example (there are lots of others like it on the Web): http://www.earth.org.uk/saving-electricity.html

Rgds

Damon

Devo · « **Reply #7 on:** November 15, 2007, 02:58:49 PM »

Tom W , how many people are in your home to get down to 300? Just Curious as We Have 5 & I have put all 11 watt flourescent lights in ,new "energy efficient" washer/dryer/fridge & am still no where near 300...

On the flip side I have a well pump , outside 160 watt barn light,electric hot water heater,an old freezer in the basement & have to use elect to keep the well house & my sink drains from freezing in the winter.

I still have many big things to conquer yet , mines coming down slowly but I have a long ways to go-lol

On the 10 KW thing I hope people here do get that big & I think it will come. I don't think sustained but 2 20 footers would peak that often I would think as Hughs first 16 footer hit 4000 watts I believe

Devo

TomW · « **Reply #8 on:** November 15, 2007, 03:20:26 PM »

Devo;

Just the 2 of us and both very energy conscious. Low pressure showers, motion sensor only lights outside floros in the house. I did not include the RE sources in that so its a tad misleading but with only 300 watts solar and one 2 meter turbine thats not a lot of kwh. Just to be fair it may total 400 kwh since I don't really have a record of the RE just the "grid" meter.

Electric stove and water heater are the killers. We use a convection "toaster oven" for anything that will fit since it uses lots less power to get the same result. Switched power strips on the watt wasters. My wireless internet and router run off DC so no wall wart losses.

Wood heat. Our own 300 foot deep well.

We really think about how and why we use power so it really helps when you get into it looking for more ways to reduce or not use. Its not for everyone and visitors typically double or triple our usage with lights left on long showers excess water use in general.

It takes vigilance, however.

Cheers.

TomW

HomegrownPower · « **Reply #9 on:** November 16, 2007, 01:01:52 AM »

Cawest

Their is alot of merrit to conserving juice . I'm not sure the KWH we used we had already eliminated anything we could from it and still our bill was about 100 bucks a month . I took one day and about 50 bucks and cut our electric bill down 25 to 30 bucks every month .

Our old hot water heater was set to hot and it kicked on to much . I put it on a timer cheap and easy to install that kicks it on 30 minutes before we get up to take a shower . Actually it's set to come on twice a day for one hour .

Doing that and craming the little closet it's in full of insulation made that much difference in our bill . I did set it down where the water wasn't getting as hot also . So I'm sure theirs many ways to conserve we don't even think of .

I'm not saying to conserve and give up on the 10kw idea . I just like the sounds of both lol

Best of luck may we all make free juice !! Lonnie

Flux · « **Reply #10 on:** November 16, 2007, 11:18:40 AM »

Don't forget that a 10kW rated wind machine could mean anything. The 10kW will be rated output at some arbitrary wind speed. Your calculations need to be based on average power out in your wind area.

In most wind areas I suspect a 10kW rated machine may struggle to average 2kW, in this part of the world it would need to reach its rated 10kW below 20 mph to average 2kW. That becomes a monster.

I am sure few people really realise the significance of the normal wind turbine rating.

Flux

cawest · « **Reply #11 on:** November 16, 2007, 12:30:37 PM »

I appreciate your comments on conserving versing producing. I did not know that 2000kwh per month was that high, around here my electricity bill is low compared to others. I have a new house (that I built myself) that is 2800sqft. It is a log home with a porch all around to protect the house walls and windows from the summer sun. I use the low voltage lights throughout the house. I installed a geothermal heat pump to save on heating and cooling bills. All my appliances are energy rated. I do have well water, so I do have to pay to pump my own water. I do have a shop and I do run power tools. I do try to conserve energy, but a family of four does still need to eat, take showers, and wash their clothes. For those of you who are not from north Texas, let me advise you on our seasons. Its is really hot, then it is really cold, there is not much in between. All that being said, it is still not helping me with the blade design for my wind turbine.

TomW · « **Reply #12 on:** November 16, 2007, 05:47:58 PM »

Darn it Flux, you always seem to be a hop, skip and a jump ahead of me.

Cheers.

TomW

wdyasq · « **Reply #13 on:** November 17, 2007, 11:47:39 AM »

"Help"

Alton-Moore.net has a blade calculator. UIUC has "PROPID" which will calculate for you also.

You are better off using three blades. Your calculations are off for the power you desire.You will probably need to increase prop swept area x 2 to get your desired output.

AND, geared turbines can eat a lot of your power. There are few of the known geared turbines I know that actually work long time.

Some will argue you are reaching the limit for solid wood blades, I think the judicious use of laminates can extend the blade diameter to over 50' using laminate over solid wood.

Ron

Andy Mac · « **Reply #14 on:** November 17, 2007, 05:08:28 PM »

Good luck on your project, I hope you undertake the project, and succeed. Look foreward to reading any further postsd on your project. A lot of folks here have a lot of good info, but on this subject you will probably have to pry it from their cold dead hands. Good luck.....

wdyasq · « **Reply #15 on:** November 17, 2007, 06:08:54 PM »

Andy Mac,

It is not so much 'pry it from them' as it takes time to do calculations and one has to have a lot more information than given and each small change requires a recalculation. Trying to get 10kW from 28' with diameter blade-set and 22mph wind is wishful thinking, not reality.

The poster has also defined a gear ratio and type. He has specified a 4 pole motor. He desires to 'over drive' the motor. He has specified the 'tip speed ratio' of the blades. He plans on carving with a particular method from a particular wood.

When I was 22 I worked under an engineer who had designed a scaffold to be hung from a crane and carry a crew working on a bridge. He had calculated all the stresses for the ideal situation. I argued it would collapse if certain conditions were met. The scaffold was build to the engineer's plans. After building the scaffold it was loaded with sandbags and hoisted off the shop floor. The engineer beamed and proceeded to tell all about how stupid I was. It got real quiet after I walked up to the scaffold, grabbed the top rail, pulled on it and collapsed the scaffold. Fortunately it wasn't 10 men at 70 feet in the air. The design was changed.

Some here have done a lot of different things. Some have worked high risk jobs and some have seen men killed on jobs. They also know how dangerous this stuff can be, the voltage, the towers and the flying pieces when something fails. Some also know the guilt of, "If I had only ....", but they didn't.

You will see few with any education recommending things on turbines approaching 13m diameter. This is what it takes to achieve a solid 10kW output. With the litigious society we have today, a lawyer could make a case to an ignorant or stupid jury it was a 'professional's advice' and since the 'professional' had or should have had insurance ... he should pay.

Many here think this is a place to get free research done and, like you just did, bitch because someone won't spoon feed what they want to hear. I am reminded of fishing stories in heaven. Jonah shuts them up with, "You think you're fishermen, which one of Ye been bait?"

Rant over,

Ron

hvirtane · « **Reply #16 on:** November 29, 2007, 11:52:10 AM »

Hi,

I've seen some 10 kW wind machine projects using induction generators and I've been involved in one project like that, too.

In my opinion it is quite difficult to utilize induction generators, if you'll use them for battery charging; it is easier to use them for heating element systems, however. The gearbox you would need would also create some problems.

How I would do it, if I had to make such a machine.

(That kind of project isn't an easy or a small one. Problems of making a wind machine reliable and safe are getting fast much bigger, when increasing the size of the machine...)

1)

If the cost is not your main concern I would use experiences gained by 'Otherpower' DanB and others and just increase the size of the general design as used by many others. Magnets for the generator would cost quite a lot but you could make it.

2)

You might start your calculations with the wind rotor of 10 m diameter. There are several methods to make it, but using the same method as has been used for the 'Otherpower' 20 feet wind rotor you can probably make it durable and working.

3)

The generator I would build by 'stacking on the same axle two axial flux generators' of the same design as many other people posting here have made them. You would need three magnet disks; in the center a disk with magnets on the both sides of the steel disk. And you would need two stators.

The calculations for the generator you could start by calculating the power you could get by 'stacking' together two of the generators of 'Otherpower' 20 feet wind machine. The effectivity of the generator will go up, when the size increases. It doesn't matter, if you'll increase the number of the stator coils and magnets by adding more disks and stators or increasing the size of the magnet disks. So with two generators like that you can draw more current out than just multiplying the 20 feet wind machine generator's current by the number two...

The axle you'll need for a wind rotor of 10 m diameter should be in my opinion at least 10 cm diameter...

- Hannu

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