Dominion to charge fee to heavy users of solar power

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Hv&Lv

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For PV, there is a unit for the purpose. SMA's Sunny Island is one of them.

http://www.sma-america.com/en_US/products/off-grid-inverters/sunny-island-5048-5048-us.html

They can also combine and control power from other sources besides PV.
That is what is there now. Not that brand, but that device. The problem is that there are 12 three phase units and 18 single phase, for a total of 500kW, all exporting to secondary lugs on the XF. The units end up monitoring each other rather than the utility.
 
That is what is there now. Not that brand, but that device. The problem is that there are 12 three phase units and 18 single phase, for a total of 500kW, all exporting to secondary lugs on the XF. The units end up monitoring each other rather than the utility.
This came up in class and the solution we were offered was, in my opinion, rather crude.

The solution was to have the generators (of any sort, PV included) set at a voltage lower than the utility. Then, set the monitoring device to only monitor above the generation voltage. When the utility drops out, monitoring is stopped. According to the teacher, it only took a difference of a volt to pull this off.

I said it was crude. I also don't know if it would work out in the wild, but it did work on paper in class.
 

Hv&Lv

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This came up in class and the solution we were offered was, in my opinion, rather crude.

The solution was to have the generators (of any sort, PV included) set at a voltage lower than the utility. Then, set the monitoring device to only monitor above the generation voltage. When the utility drops out, monitoring is stopped. According to the teacher, it only took a difference of a volt to pull this off.

I said it was crude. I also don't know if it would work out in the wild, but it did work on paper in class.
The problem with that is in order for the solar generators to export, the voltage must be higher than the utility voltage. Keep in mind the water analogy. If the utility pressure is lower than the solar pressure, then the sloar will feed the utility.
It goes without saying that the solar producers want to push the envelope as far as voltage goes. The higher voltage they push, the more power they sell. Asking them to stay within one volt is like slapping their mother in the face :lol:
 

jaggedben

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Solar and Energy Storage Installer
That was exactly the point of those you are debating. When the solar is not outputting any power, the utility must be able to provide the generation, and have the system capacity from the generators all the way to the solar customers. They must be able to do this (as it always has been) while making less money because the utility has sold less power to the solar cutomers during the day.
A power demand (kW) based charge is a terribly bad way to rectify the situation, because there is no definable relationship between the customers power demand and the fact that he or she has installed solar. The customer's night time power demand probably does not change, and their daytime power demand, if it changes, goes down. The kW based standby charge will cost some solar system owners a lot of money, and some only a little money, even if their solar production is the same. It appears that they will be charged this standby fee even if their solar system never exports power to the grid. It's a completely irrational way to deal with the problem you describe (even if it is a significant problem, which is debatable).
 

jaggedben

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Northern California
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Solar and Energy Storage Installer
The problem addressed by this thread was that some members took issue with the fee that Dominion was going to charge. They felt like there was no way a fee like that could be justified but that idea is completely wrong.
My main argument has been that a power demand based fee is inappropriate. In fact, I think it makes a mockery of everything you've been saying about how charges should be allocated according to where the associated costs come from. The demand charges that Dominion is now going to charge the solar customer are arbitrary: they have no particular relationship to the size or energy production of the solar system, and will not be fairly distributed among multiple solar system owners, to say nothing of those that don't own solar. (Basically, if I am a residential customer who is not charged for kW, I can run my demand way up and pay nothing extra. But if I happen to own a solar system, I could pay a fortune for the same behavior.)

Now, there are other reasons why I think, generally speaking, that extra fees that discourage solar are a bad idea. Reasons having to do with global climate catastrophe and resource depletion. But I think those issues are, and should remain, outside the scope of discussion in this forum. So I have refrained from pushing those arguments in this thread. I realize that it all costs money and not everybody is convinced it is worth paying for. But Ggunn was absolutely correct a few posts back when he said "What it really boils down to, IMO, is what the utility is trying to accomplish." And I am still convinced that what Dominion is trying to accomplish isn't merely to be fairly compensated, but rather to quash the adoption of solar per se. And I am not convinced they have a good reason for that, nor has anything that has been said in this thread changed my mind.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I realize this is off from the original topic, but I would like to pick your brain...
How do you keep parallel installations feeding into the same transformer from islanding? Each seperate generator seems to be monitoring each other. When I remove one phase the generators aren't shutting down. Until they shut down automatically I won't allow them to remain connected to our lines.
I have asked that the bandwidth be tightened up(default is 105-255) and the upper limit be set a little lower(221V). The generators are synching to a 120/208 500 kVa XF. I posted this earlier and didn't get much response to the problem. Wouldn't all the generators have to feed to a central monitoring point to keep from reading each seperate generators voltage? here is the link to the original thread: http://forums.mikeholt.com/showthread.php?t=141546&p=1355139&highlight=#post1355139
My understanding is that unless the generation and the load are perfectly matched, the voltage will go out of range (up or down), and the inverters will shut down. I'm not sure why you think tightening the voltage window is necessary, although I would be happy to peruse any math you have to share on the subject, if I can understand it. It seems to me that the issue would be the probability of the load matching the power for any period of time. I would think it's a very low probability. The window is based on IEEE standards, I'm pretty sure.

Also, there is frequency. I'm really not sure that the inverters would maintain 60Hz without help from the utility. But you could probably tell me more about that.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Thank you for keeping your sense of humor. I realize that we do not exactly see eye to eye on some of this stuff, and neither of us is likely to substantially change the other's position. That said, I have gained some insight into the "other side" that I had not had before.

Peace,
Gordon in Austin
 
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