Antoher Wind Turbine Question

[richanton]

I've searched through the posts here, but haven't found an exact answer. I am installing a small 600 watt output wind turbine that will go through an iverter. I don't want to tie into the grid as there is just too much paperwork for that. I'd like to take the 120VAC output of the inverter to a small transfer switch that has the wind turbine as the normal supply and house 120VAC power as the alternate. That output would go to the input of a small UPS(maybe 750va- 1kva). The load I am attempting to drive is a couple of small servers, maybe 300 watts total.

My confusion is what happens when the wind turbine wants to generate more than I need.

 

[juleselec]

Presumably you'll have a permanent magnet wind generator connected to a DC rectifier stage.

Because there is no governor control, the AC voltage at the output of the wind generator is also uncontrolled and fluctuates proportionally to the speed of the rotor (and by extension, the wind speed). When a load is connected, a back emf is induced that acts counter to the rotor and slows down the turbine. So at full load, you need a certain wind speed to keep the thing going.

Now when there is no load, the wind turbine will be spinning faster at the same wind speed as before. Because the output AC voltage is proportional to turbine speed, the voltage will also rise as the turbine speeds up.

This isn't a problem as long as your rectifier and inverter are operating within their specified tolerances (check with the manufacturer). Also, the turbine should be mechanically capable of some level of overspeed and the stator windings for some level of overvoltage.

In large wind turbines, there is typically some kind of pitch control / assisted stall control / etc which can prevent the turbine from mechanical damage due to high wind speeds. But a 600W turbine will just have to put up with any large gusts... or fall apart or have the windings burnt out.

 

[7anoter4]

Since juleselec explain so detailed the phenomenon I only want to suggest a simple solution:
If you could provide an over-voltage switch you would introduce a 2-5 kw resistor in circuit and overcome the hurricane[If the generator could produce 5 kw for a while!].
see for instance:

http://www.eeweb.com/blog/circuit_projects/relay-operated-switch-for-over-voltage-and-under-voltage

 

[LionelHutz]

You need to charge batteries with a direct connection off the turbine. You also need a dump load and controller to keep these batteries from being over-charged. Letting a wind turbine free wheel is not a good idea, except some may have such small and poor blades it won't matter. I suggest you do more basic research.

 

[TheBlacksmith]

I'm thinking some batteries too. There will probably be periods when the output is much less then the required 300 watt loading; batteries would clip the peaks and fill in the valleys. I'm buying a house in the country and contemplating either a small wind turbine or photovoltaic panels and would use a small battery bank as decribed above.

 

[itsmoked]

Add me to the batteries and a charger/load controller are the way to go crowd.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[MAGTiger]

Keep us informed of your progress, I'd be intrested to know when it's all done how much it costs to set up a 600w wind supply.

Neil

 

[richanton]

Thanks for all the info. I'll post after we figure it all out and get it installed.

 

[LionelHutz]

I'd be more curious how much of the time the 600W wind turbine actually produces 600W. It seems to me that the little "toy" turbines have such small blades that you'd be lucky to get 50-100W average in most typical installations.

 

[richanton]

FYI, this is the unit we are buying.

http://www.youtube.com/watch?v=eO3inlC2ZOQ

 

[MAGTiger]

my understanding is that large wind turbines are expected to develop about 33% of nameplate power on a continuous basis converted to KWH. If that assumption holds true you may be able to deliver 200 watts on average.

Neil

 

[itsmoked]

They stuck one of those on our municipal wharf.

Interesting that if you blink looking at that movie the unit appears to turn backwards or forwards to the eye.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

The specs look OK. What is your average wind speed and what power are you expecting to produce a year?

If I recall correctly, a good rule of thumb is to place the turbine 30' higher than any obstacles within a 300' radius.

My two bad thoughts looking at the UGE web-site were that I'm not a fan of roof mounts and the main UGE web site makes you jump through hoops to get to any product details. Overall, the web-site makes me think "green chic" where they're more about selling an idea then a good product. Similar to the shady companies selling "power saving" devices or the next "revolutionary" internal combustion engine.