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Post Info TOPIC: Feeding the Grid
windgen


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Feeding the Grid
 

Correct me if I'm wrong, but I'm pretty sure that modern brushless DC motors are considerably more efficient that the older brush-type.

Your companys' decision to move to AC may have been motivated by many factors such as price of effecient DC motors vs. price of AC motors etc...



-- Edited by windgen on Wednesday 9th of May 2012 06:28:07 PM

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fluitic


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RE: Feeding the Grid
 

sjh7132 wrote:

Is over driving an induction motor preferred by the power company because it's efficient or because it's cheap and doesn't require magnets?  Even if it is efficient you also have to account for the efficiency of the DC drive motor.  Maybe they aren't bad. I don't know.  This is out of my area of expertise.  Does anyone know the efficiency of a 1/4 or 1/3 horse DC motor?

 

 Where I work we are in the process or changing out 96 1/4 horse DC motors for 1/4 HP AC motors.

The DC motors are brushed style permanent magnet motors that need brushes changed out every year. Between the drive and the motor they draw from 2 to 3 amps at  230volt. The replacement  3 phase AC motors with the drives are drawing between 0.9 and 1.1 amps at 230 volts. In each case I don't know how much of that load is coming from the drives.

The DC motors are running graphite brushes. We tried carbon brushes once for less voltage drop at the commutator and they would wear out within 6 months.



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Dan
sjh7132


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RE: Feeding the Grid
 

Lynx wrote:

Your MPPT sounds even better now if it can accomplish this dump from battery to GTI.  That would be so sweet for us Westerners trying to reduce our electric bills.

For a guy in the under-developed part of the world - not so much.

 The idea can be applied in other ways.   You could use your batteries between the 90% and 100% levels so you always have power for when you want to use it, and when you have extra, use it to pump water from a well.

 



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Steve
Lynx


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RE: Feeding the Grid
 

Your MPPT sounds even better now if it can accomplish this dump from battery to GTI.  That would be so sweet for us Westerners trying to reduce our electric bills.

For a guy in the under-developed part of the world - not so much.



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Marcus
windgen


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Feeding the Grid
 

The big boys design and build induction motors specifically for huge wind generators. Because they are on such high towers in designated areas, they have the luxury of a fairly consistent (non-turbulent) wind.

The DC motor is the weak-link in what I am proposing. It would be great if someone knowledgeable about DC motors chimed in.

A cursory Google search shows 90%+ effeciency for DC motors.



-- Edited by windgen on Wednesday 9th of May 2012 04:35:53 PM

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sjh7132


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RE: Feeding the Grid
 

Is over driving an induction motor preferred by the power company because it's efficient or because it's cheap and doesn't require magnets?  Even if it is efficient you also have to account for the efficiency of the DC drive motor.  Maybe they aren't bad. I don't know.  This is out of my area of expertise.  Does anyone know the efficiency of a 1/4 or 1/3 horse DC motor?

 



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Steve
windgen


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RE: Feeding the Grid
 

So if we are stuck with turbulent electron production (via VAWT) that has to be buffered if you want to grid-feed, the question becomes how to buffer, and then how to use this "bank" of stored energy effeciently.

I would think that if you had batteries that liked being depleted and re-charged, then feeding the grid with an over-driven induction motor in bursts would be the way to go. Over-driving an induction motor is the preferred technology of the major wind generation companies for a reason.



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sjh7132


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Feeding the Grid
 

Lynx wrote:

Switching off at the AC plug to wall is brilliant.  If a photo cell can switch off a 500 watt flood light, seems like the photo cell could be replaced with a battery voltage sensor.

 Here is a solid state relay that one of the aux outputs on my board could drive with no special circuitry.  (or a simple comparitor circuit) It's good for 5 amps of AC so about 560 watts from the inverter.   There are many others, this is just an example.

 

Windgen, you are correct, how to best treat the battery depends on the battery type.  I was assuming lead acid because they are relatively cheap.



-- Edited by sjh7132 on Wednesday 9th of May 2012 03:49:22 PM

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Steve
windgen


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RE: Feeding the Grid
 

Lynx wrote:

Switching off at the AC plug to wall is brilliant.  If a photo cell can switch off a 500 watt flood light, seems like the photo cell could be replaced with a battery voltage sensor.

 I would think that any type of rated relay would work; mercury relays in really high-amp situations.



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Lynx


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RE: Feeding the Grid
 

Switching off at the AC plug to wall is brilliant.  If a photo cell can switch off a 500 watt flood light, seems like the photo cell could be replaced with a battery voltage sensor.



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Marcus
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