wind and solar energy

Status
Not open for further replies.
electricalperson said:
how do people with these kinds of systems sell power back to the power company?
Click to expand...
Normally with a second meter or a net meter.

PV_net_meter.JPG
 
electricalperson said:
how do people with these kinds of systems sell power back to the power company?
Click to expand...
It depend on how your state ulitility commission or the like sets the laws.
I hate percentages but a statement has be made here that your selling it back at whole sale not retail to the utility, A I R
 
electricalperson said:
but does it actually put electrical energy on the lines?
Click to expand...
Um. ... yeah. Why wouldn't it? :-? The PoCo wouldn't buy it if you weren't putting it there.

If you're going to use it all yourself, nobody really cares. If you have extra and want to sell it back (ie, put it on the grid), then you set up a net metering arrangement and get paid for it.
 
cadpoint said:
It depend on how your state ulitility commission or the like sets the laws.
I hate percentages but a statement has be made here that your selling it back at whole sale not retail to the utility, A I R
Click to expand...
I thought "net metering" meant it comes in and goes out at the same rate.
 
electricalperson said:
so it actually adds 120/240 volts back on the wires back to the transformer? how does it do it without blowing up?
Click to expand...

The current and voltage you are putting in the grid must be in phase with the utility supplied voltage and current.
 
peter d said:
The current and voltage you are putting in the grid must be in phase with the utility supplied voltage and current.
Click to expand...
im not too familar with any of these kinds of systems i never installed or seen any before. i was having a conversation with a friend about solar panels and wind generators on your house and she said you can sell the power back to the company. i knew they would pay you for that but i was not sure how you can add current on a line that already has current without it being in phase. i guess you add a device that makes the power from the generator being in phase with it
 
Theres been a few conversation on off grid and the applications that are involved, via this forum!

I believe your customer is making a short sided statement on "the sell back" based on no battery useage, and no understanding of transfer equipment, Etc.
 
Last edited:
electricalperson said:
i knew they would pay you for that but i was not sure how you can add current on a line that already has current without it being in phase.
Click to expand...
You can't. That's why you have a grid tie inverter to sell back power, rather than an ordinary inverter if you're just using it yourself.
 
electricalperson said:
im going to read more about this stuff just to educate myself on the basics on how the system works and whats needed to hook it up
Click to expand...

I am currently installing a "grid interactive" PV system.

From an electricians perspective it is quite simple. I connect the solar array to the inverter and then connect the inverter to the buildings service.

On this job we are using Satcom 50 KW inverter, it is quite a complicated piece of equipment and I will not pretend to know how it works. On the AC side it will be about 150-175 amps at 208 3 phase, on the DC side it will be about 440 volts, 150 amps. (very rough figures based on a maximum sunny day and my recollection)

But as the others have said the inverter matches the grids characteristics before becoming active. If the utility has a power outage the inverter sees that and stops producing power so that it will not potentially hurt the power company workers.

Take a look at Article 690 in the 2008 NEC, there are some nice diagrams of the different kinds of systems.

I am also looking at plans for a 500 KW system that will use 5 inverters in parallel, the DC will be coming in from 6 large arrays (total of about 2,600 panels) be combined and fed into the inverters, the inverter will change that 500 volts DC into 480 volt 3 phase AC.

In both these installations we will be using a 'net meter' and at times these systems will be making more power then the building they are on uses.

Ask questions, I will be glad to try to answer them, also check out this site http://www.nabcep.org/

And if you are really seroius about learning about PV systems of all types download this 2008 PV Study Guide
 
Last edited:
iwire said:
But as the others have said the inverter matches the grids characteristics before becoming active. If the utility has a power outage the inverter sees that and stops producing power so that it will not potentially hurt the power company workers.
Click to expand...
It's amazing how it's able to output power to the utility and sense when the utility power drops.
 
Iwire
are you or anyone in your company certified by NABCEP? I tried to take a class put on by them last spring but had some stuff come up so I couldn't. Going to try again this winter, was wondering if it was worth it?
 
cadpoint said:
It depend on how your state ulitility commission or the like sets the laws.
I hate percentages but a statement has be made here that your selling it back at whole sale not retail to the utility, A I R
Click to expand...

Some state commissions are requiring that utilities buy back the power at the retail rate and not wholesale. I think this will catch on eventually and be a rule in more and more states. But many utilities still are buying back on the cheap.:smile:
 
Status
Not open for further replies.
Top