12.2kw solar barn

[peakbagger]

A general comment is to expect a visit from the utility once or twice and possibly a meter swap out. Most utilities have antifraud software that flags changes in usage that doesn't seem to recognize solar. Thus your sudden decrease in power usage and net generation looks like you flipped the meter and thus fraud. It took the back office of my utility a couple of months to figure it out. I also got hand prepared power bills for several months as their software just didn't deal well with net metering. My bills also have a graph of average energy usage per day, that still isn't working.

 

[jebatty]

PV is like solar magic. Do nothing and it pays you money. Makes sunny days extra special.

 

[JP11]

A general comment is to expect a visit from the utility once or twice and possibly a meter swap out. Most utilities have antifraud software that flags changes in usage that doesn't seem to recognize solar. Thus your sudden decrease in power usage and net generation looks like you flipped the meter and thus fraud. It took the back office of my utility a couple of months to figure it out. I also got hand prepared power bills for several months as their software just didn't deal well with net metering. My bills also have a graph of average energy usage per day, that still isn't working.

I would be surprised if this happened. They came out a few days before my install and put in a second meter. I have two brand new meters.. both started at zero. One is a 'buy' meter and the other a 'sell back'.

The 'buy' meter will run backwards (well, it's not the old style with a dial, but a digital representation of one).. the meter will show running backwards, but it does not count down. The 'sell back' meter will show the digital dial spinning and only count in the up direction as well.

Takes me a second looking at both to figure out what's going on. I'm surprised when not much is going on in the house how little sun it takes to break even.

JP

 

[jebatty]

My install got two digital meters also which operate like yours do, plus the installer put in a third mechanical production meter to verify PV production at the panel as opposed to the software reported production, and also to verify that the buy back the utility is giving me is accurate. The buy back/sell has been right on. Panel production is reading about 1% less than software reported production. That might be line loss over the 280' between my PV and the panel.

Determining actual house electric use is: buy meter + production meter - sell meter.

 

[JP11]

Took a look this morning. my sell meter is 500 ahead of my buy. not bad for being a week shy of a month.

 

[JP11]

5 weeks in to get over 2 Megs. Pretty cool. Sell back is over double what I've purchased. Had all the AC running, and wife was shooting pics (she's a pro photographer with LOTS of lights ) Meter was still running in the 'good' direction with full sun.

JP

 

[JP11]

Well, PV watts does (30 year AVERAGE weather) This year's snow and cold sure hasn't been average.

My one inverter has been sporadically making power for two months, but the other was not (4 foot snow drift)

Today, my guess (I'm away on a trip) is that the second 24 panels are exposed enough that the second inverter 'woke up'

It filled in all the past data. My low point.. Feb I was supposed to make 10370 watts. I made 618

I had massive, weeks long outages.

I got messing with my spreadsheet that I paste in outputs. If I cull out the partial months.. I'm at about 68% of PVwatts estimate for production. We'll see how it does when the rest of the snow is gone.

JP

 

[JP11]

Best day ever today (only had system online since Aug 22)

75kwh and still going.

Day's get longer for the next three months almost. I guess this is where I'm supposed to bank a bunch of power for next winter. I changed 4 circulators on my wood boiler to 'bumblebees' they save a ton of electricity. All future power bills should be under 10 bucks!

JP

 

[jebatty]

Congratulations again! PV stimulates the immune system to hunt out and kill every electric energy wasting device and to trim all others to the minimum that's needed while on the way to electric net zero.

March is headed towards a very strong finish for my 6.5kw system. Absent something unusual, I should end the month very close to 1MW and above the PVWatts average for March. Two days to go.

 

[JP11]

My next benchmark.. the day I make 100kwh. I'm pretty sure I can do it closer to June.

JP

 

[JP11]

Easter started out snowy.. but I'm going to get 72 kWh for the day. Can't complain about that. April production has already surpassed Jan and Feb combined. Few more days, I'll have March's total beat too.

 

[begreen]

Very nice. Looks like you're clipping at 10KW. Is this the limit of the inverter?

 

[JP11]

Yes.. two 5k inverters. They seem to run about 5060w as a max.

Panels aren't even a year old yet. I suspect that I'm clipping by a couple hundred watts during the peak of the day. So I'm losing a bit, but I bet the panels 'wear' into the inverters and it works about right.

JP

 

[jebatty]

Regarding clipping, clouds and shading: if you have a good morning production with a mostly smooth curve until clipping starts, and a similar afternoon not too far in time before or after the morning, you can overlay the two curves and "round out" the resulting curve. Then if you can get a kw data download for those periods, insert data points to fill the curve, you can determine quite closely the impact of clipping, clouds and shading vs a full sun day, and similarly you can determine what likely maximum production could be at the time of the year when you would do this.

I have micro-inverters rated at 250w, each panel is rated at 265w watts maximum, and for my 26 panels based on the inverters that comes to 6.5kw rated, based on the panels 6.89kw maximum. I have in fact observed maximum inverter output at 268w briefly, and if that continues more than a short time clipping occurs at about 265-266w output, and that's a quite uncommon event for me. The additional 20 panels I am having installed will use the same micro-inverters and have a panel rating of 270w maximum, and I suspect I will see a bit more clipping, but it still will not result in a significant loss of power which would make it worth buying higher rated inverters.

 

[JP11]

I have seen a few days that were near perfect. Maybe someday I'll print out the graph. It's a very smooth curve.. I could easily find out what I'm losing. I guess my question would be.. what then?

The installation company didn't even offer me 6k inverters. Maybe it's diminishing returns. As I said, I suspect the panels will come down a bit with age.

JP

 

[begreen]

We're currently starting to see clipping at 4.5KW. That is a bonus considering our inverter is rated at 4.2KW. This is why I put one array on a pole. I will be rotating it 45 deg to the southwest soon. Theoretically that will reduce the clipping period and extend solar gains later into the evening.

 

[JP11]

I have heard that you can 'over clock' them and run them higher. I just don't know enough about the inverter. I guess since it's under warranty... and it's LOTS of DC volts.. I won't be messing with it.

JP

 

[JP11]

New record today.. And the days are only getting longer. 81kwh

 

[jebatty]

For our equally sized systems, same maximum power output so far. I too had 80.94kwh on Aprill 11. Had an odd problem yesterday. There was a brief power outage and when power came back on one of my two micro-inverter data recorders stopped reporting to the website. After a lengthy, but very helpful, discussion with tech support, and several different approaches from rebooting to reprogramming, the solution ended up being removing and reinserting the small coin cell battery internal in the data recorder. The battery voltage tested fine, must just have been slight corrosion on the contact.

 

[JP11]

Every once in a while my data drops out. I've had it go as long as a couple days. It has always gone back and filled in the missing information. It even went back a month and a half after being snowed out. I'm surprised for something internet connected how slow it is to update. I happened to be in the barn with my dad yesterday, and saw I had made 40kw. When I went back inside.. the display was running over half an hour behind. It matches perfectly by days end.

 

[JP11]

Right on the money for what PVwatts said. Got my first minimum power bill. 10.65 I hope and expect it to stay like that forever now. Last month's bill was buy 505kw, and sell back 1100. It's nice to see after a rough winter. I was WAY under on production.

 

[maple1]

I keep thinking out a solar setup & where I might put one if I wanted - I really think small solar has a lot of merit - but keep coming back to the issue that, simply speaking, my annual returns would be limited to my annual consumption. Which is around $1000/yr. So I am still limiting myself to just thinking about it - but haven't completely ruled it out as you never know what the future might bring. Nice to see your success with it though.

 

[JP11]

Maple.. It's VERY dependent on what your local utility rules are. If they don't provide 'net metering' that's advantageous.. you just can't win. Essentially, the neighbors get my power, and the power company functions as my battery. If you aren't paid retail rate for your excess production, your time to pay back the system is VERY long.

I did it because I wanted to.. and I know it will EVENTUALLY pay a nice dividend in power for free. At the current moment.. my payback is at 13 years. I suspect those numbers to get closer to 10.5 or 11 years, I'm just working with assumptions for some of the year, and a VERY unique winter snow drift this winter.

JP

 

[tmarch]

I used $ from my retirement IRA to pay for my 6K system and it's ROI is a LOT more than the balance of the IRA. I was able to use the $ without paying taxes due to the 30% tax credit.
My utility pays me their wholesale rate for the excess I produce which isn't good, but at least they allow me to use them for a battery.
Lots of ways to fund a system, just takes some planning.

 

[JP11]

Ouch.. sell back at wholesale. That helps make the case for batteries. But there isn't a battery system out there that will let me use power in the winter, that I made in the summer. If my terms had been that way, I likely wouldn't have done the system. It's so very seasonal for me. The first 5 days in May have produced more power than all of Jan and Feb combined.

JP