Gusts mean little - Average is everything

[Dave B]

We had gusty winds the other day of over 35 mph. Shown is a graph of my voltage output over 6 hours. My Davis meter indicated an average wind speed of less than 10 MPH for this period. Peak output was over 2500 watts but the average output for what seemed to be a very windy day was under 200 watts for 6 hours time. Great to be able to log and analize this data. I figured others might like to know that what you think you see is not always what you get. (you can right click and view image for better resolution) Dave B.

[DanB]

Hi Dave =- do you have a good way to just keep track of watt hours (or KWH)?  It's been pretty interesting for me since I put such a meter on it.  

[Dave B]

Hi Dan,

  I don't have a kwh meter on my system at least yet anyway. It has been an eye opener as far as real useful power and especially heating water as I am. It is amazing that even with 500 watts constant that will raise 50 gallons 50 degrees in about 12 hours. A good night of 15 mph wind will pre-heat 50 gallons of water to 100 degrees F or so depending on the start temp. in the pre-heat tank. Normally this would be around 60 degrees or so after using a fair amount of hot water from the main tank. I have learned more of the very exagerated claims of certain manufactures and their systems or at least more of their carefully worded claims. Do you have a source for or offer kwh meters ? I can figure it now with average wind speeds and output etc. but a meter sure would be nice. My system is working well, thank you for sharing your information as I would never be this far along without your help.  Dave B.

[windstuffnow]

  Dan has the "Doc Wattson" watt meter from http://www.rc-electronics-usa.com/ .  After reading his post about it I purchased one to play with.  They do have some limits, primarily voltage input but there are work arounds for that.   I did have a bit of an experience with their company though... When I connected mine to the small rooftop turbine, it came on and after a short time the screen went blank.  I spent several weeks with them trying to get it replaced, they did finally replace it but it was a real nightmare.  The meter works great, I can't say that about thier company.

[Nando]

Dave B:

You have the watt meter already in your system and you may do it by integrating the power you have.

One way is to do One second integration or even lower times, read the peak power like every 100 milliseconds and add the values then add the times which gives you the watts per added time which you can convert into watts-hours.

You are already getting the watts samples, integrate them.

Nando

[Dave B]

Thanks Ed,

  I looked at the site and I'm not sure how I could make this work unless I used a battery in the system  as it is a DC device. I'm running wild 3 phase AC direct to my load(s) and want to keep it that simple other than possibly a load controller. I know I could rectify to DC to a small battery that would basically remain charged and then I could dump the load to my elements above the battery voltage. This would also allow for unloaded start up besides. I really don't want to do this and as it is now I can figure averages from the data collected but I have to admit a kwh meter sure would be handy. Any other ideas or thoughts are appreciated.  Dave B.

[Flux]

Yes Dave, you are right that the peak is of little value. Your data clearly shows how many of these machines survive with peak power levels well above what the winding can stand. On gusty sited where the average is very low there will be little heat in the windings. On a site with decent clean wind the average power could be much closer to the peak.

I suspect that the wind power duty cycle is normally very low and the alternators are working nearer a duty cycle associated with small welders and other intermittently rated devices.

With your heating load you have the option to match the load far better to the alternator in higher winds so stator temperature will be much less of an issue.

Also as there is negligible heat in low winds it doesn't matter much if you are well off the best operating point in low winds. A high start up speed and running in stall at the lower wind speeds will cost you very little in terms of heat produced.

If you can keep control of the thing by furling in high winds then you may not need much in the way of ideal load matching. A single fixed load is possibly being very optimistic but you may manage with it.

The thing to avoid at all cost is the temptation to add excess load in high wind to keep speed down rather than furl. If you have to do that then do it drastically enough to stall the prop and reduce power into the alternator. Don't work at the point where the prop is not stalled and you are dissipating more in the windings than into the load.

I see you are looking at capacitor series circuits. Yes, fine in theory but at low voltage and low frequency I wouldn't consider it a viable solution unless you have a source of large quantities of near free capacitors. The cost in capacitors to do it satisfactorily will be ridiculous. Electrolytics I would consider a short term solution. the only saving thing is that electrolytics generally fail to short and would be safe for the machine. They also sometimes fail spectacularly to mechanically open circuit with a bang and lots of mess so keep them in a closed container if you do play with them.

Flux

[Dave B]

Flux,

  Thank you for your reply and very useful information. I am learning as I go and it is so helpful from those who share their successes and failures here that I hope I can contribute some the same. Patience is important so that not to make radical changes too quickly based on minimal observations. This has been up now for nearly 6 weeks and I have yet to see the constant winds that will be more frequent this Fall and Winter. If I were to make some changes now I am certain I would be changing things back later on. Right now things are safe and well behaved but like you say it is tempting to tweak things and I think that is where some get into trouble (burnt stators for example). I would rather accept a little less all the time and be safe when the winds really blow (and they will) than to risk having to build again just for short term gain. I sure appreciate everyone's help, more updates to follow.  Dave B.

[boB]

I would LOVE to see an accumulated Watt-Hours graph overlaid on top

of your graph.  Good or bad results, gotta do that !

I don't think I've seen a graph like yours with the W-hour info on

top.

boB

[Dave B]

Bob,

  The average wind speed for an exact 6 hour section of the graph shown was 10 MPH calculated by my Davis weather wizard. Once up to speed I measure 250-300 watts at 10 MPH. To be conservative would be to say that the average was 200 watts for 6 hours or 1200 watt hours. I have seen 1200 watt hours in half that time on days that seem no where near as windy but with constant wind. It is great to be able to log this data simultaneously and have the weather wizard  do most of the math. Another improvement on the output will be building a load controller for start up. I am losing some useful power in the low end when the winds are near 10 mph but won't quite bring it out of stall. Thanks for the comment, more updates to follow.  Dave B.