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#193218 - 03/21/10 07:33 PM A New Twist to Solar and Wind Power  
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
The latest issue of the IAEI magazine has an (actually readable) article on a new twist to alternative energy: the micro-inverter.

Personally, I think this is an idea whos time has come. Where it matters to us is that it radically changes the way secondary power sources are tied into the system.

In the 'conventional' arrangement, all of your generating sections are tied together, and a single feed is brought to a single inverter that, through a transfer switch, feeds the panel.

With micro-inverters, eaqch solar panel has it's own tiny (figuratively tiny - the ones in the pictures didn't look very small!) inverter. Through some means I don't understand, these inverters are all in sync with each other, and thbeir AC outputs are combined to form a 15 amp circuit, which backfeeds an ordinary breaker in the panel. Again, how these inverters 'know' how to be in sync with the PoCo is something I don't understand.

This approach, IMO, will revolutionize the solar (and, to a lesser extent, wind) industries.

Why? First of all, because it's all self-contained. You can do it without disturbing the PoCo feed to your panel. You can easily add or remove units from the system.

On the downside, you have a much greater chance of encountering a 'live' panel even when you think everything is 'off.' While the inverters are UL listed, and are designed not to supply power unless the PoCo supply is also present, I am still "cautious."

After all, how do you 'turn off' a solar cell? Throw a tarp on it?

In a roundabout way, this brings me to one of my gripes about most breakersw: there's NO space provided on the face of the breaker for you to use to identify the breaker. Take the panel cover off, and the breakers all look alike. You have no ready means of identifying which breakers are being back-fed.

I'm also not sure if there are any 'tie downs' avaqilable for single pole or 'skinny' breakers. Until now, we have assumed a back-fed breaker would be a multi-pole breaker. That is no longer the case.

Lets consider another possible arrangement: micro-inverters supplying their own panel, with a feeder connecting this panel to the house panel. Now we have a feeder that, IMO, needs to be LOTO's at BOTH ends.

What are your thoughts?

Tools for Electricians:

#193229 - 03/22/10 12:25 PM Re: A New Twist to Solar and Wind Power [Re: renosteinke]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,099
I am about to know a bit more about this. I have a solar company coming over soon to sell me a grid tie system but I think I understand that these inverters only put out when the POCO power is present and they sync to the power they see.
I have really just been talking to a sales person up until now and she is not really the technical person I want to talk to before I plunge.

BTW with all the rebates they are approaching the "buck a watt" price I have been saying was the break even point for me.

As for the ID on the breaker I may paint it red or something. I agree you want a positive ID on this for a number of reasons.

Greg Fretwell

#193234 - 03/22/10 02:24 PM Re: A New Twist to Solar and Wind Power [Re: gfretwell]  
SteveFehr  Offline
Joined: Mar 2005
Posts: 1,208
Chesapeake, VA
I think you're missing the real problem here; it's not licensed electricians or enthusiastic DIYers- they're at least going to label it in some fasion.

The REAL problem is that there isn't anything preventing people from buying a package unit and sticking it into the nearest receptacle. This will be done with no thought or concern for safety or overloads or anything else.

#193236 - 03/22/10 08:18 PM Re: A New Twist to Solar and Wind Power [Re: SteveFehr]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,099
The way the rebate programs work make DIY cost prohibitive. It would cost me about $5-6 a watt to duplicate the system that I am getting for the $1-2 a watt price after the rebates. You can't get the rebate without having a state licensed/certified installer put it in. I assume other states are the same. I read the federal rebate program to work the same way. I know in the 70s you couldn't get any of that federal money without a licensed, certified installer signing the rebate application. Found that out the hard way. ;-(

In a world where Home Depot sells 200a load centers and meter bases, this solar thing is far from the most troubling thing they encourage Harry Homeowner to do.

Greg Fretwell

#193291 - 03/25/10 01:20 PM Re: A New Twist to Solar and Wind Power [Re: gfretwell]  
SteveFehr  Offline
Joined: Mar 2005
Posts: 1,208
Chesapeake, VA
Rebates? I think you overestimate the cognitive capacity of the average Harry Homeowner to think that far ahead. Somebody is going to start selling these things with all sorts of unrealistic claims and a plug attached, and people are going to go nuts over them.

...actually, this sounds like it could be a good business model! Remember, though, this is MY idea, not yours! Just need to make sure I put the right disclaimers and footnotes on which county in California I based the electric rates and solar flux on laugh

#193310 - 03/26/10 09:58 PM Re: A New Twist to Solar and Wind Power [Re: SteveFehr]  
ccdave  Offline
Joined: Jan 2003
Posts: 59
culver city,calif. usa
Am I hearing that if your POCO drops out during the day that the solar will not feed your panel?

#193316 - 03/27/10 11:51 AM Re: A New Twist to Solar and Wind Power [Re: ccdave]  
LarryC  Offline
Joined: Jul 2004
Posts: 783
Winchester, NH, US
Am I hearing that if your POCO drops out during the day that the solar will not feed your panel?

YES. Grid tie inverters will not put out if the POCO is not present. This is to prevent backfeeding the utility lines.

#193361 - 03/29/10 01:27 PM Re: A New Twist to Solar and Wind Power [Re: LarryC]  
SteveFehr  Offline
Joined: Mar 2005
Posts: 1,208
Chesapeake, VA
So, _in_theory_, it should also cut out if the breaker pops or is opened to isolate a circuit. Probably works on the same droop-adjusting principals as a parelleling generator or UPS unit.

#193418 - 03/31/10 07:40 PM Re: A New Twist to Solar and Wind Power [Re: SteveFehr]  
Todd_from_DE  Offline
New Member
Joined: Feb 2010
Posts: 2
Micro inverters are definately Not a 'cure all'.
They have their place.
They will not work with all manufacturer's modules.
Take an enphase, for example. It will Not work on a GE module. GE modules do not have enough cells.
Micro inverters come in handy where shading is an issue.

be careful. I own and operate a solar contracting business.
I went to school for PV in Florida, and my parents and alot of friends live in Florida. I have researched Florida's rebate program intensely.

Even with all of the rebates and incentives, I highly doubt you are going to see a 'buck a watt' type cost.
That is some very good salesmanship with some 'possibly' questionable math statistics.

My company gives Free installation on any system purchased through us. Even then, after rebates and incentives, our customers will not see a buck a watt cost, and our selling point is $2 - $2.50 a watt less than the average of our competitors.

If you would like me to show you more accurate cost break downs, message me.

I would like to know how the salesman told you to break down your incentives.

#193420 - 03/31/10 10:55 PM Re: A New Twist to Solar and Wind Power [Re: Todd_from_DE]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,099
This is Fafco Solar Cape Coral
They say
10 Canadian Solar 230-PV Panels
Aluminum mounting system
Inverter, installation,documentation and ancillary paperwork
2.3KW $17,250
Fl rebate $9,200
30% fed tax credit $5,175
total after rebates $2,875

That is a buck and a quarter a watt if they can actually do it for that price.

Greg Fretwell

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