Just because sunspots align this week, does not mean they will align next week.
The point being that the OP was so happy about PV watts matching what he harvested, was a random stroke of luck. At any one day, PVwatts could be expected to be + - 10% or more, it's using a historical 20 year average. Cool day, haze, clear, all will affect the harvest, and if blind faith was used on a non-matching day, the OP was just as likely to head to the suppliers office with a ream of data in hand to make a fool of himself.
My New 7.56KW Ground Mount.. First Light, First Watts..
Collapse
X
-
If I'd written as you suggest, It would not have been my opinion, nor would it be a true representation of how I see the situation.
As usual, and as in the past, take what you want. Scrap the rest.Leave a comment:
-
A confrontational statement that lead to a half page of banter that wasn't required reading for anyone.
Could have simply said "Great! Output seems to match predictions". No newbs following this thread would have been lead astray by Murby's "99.97%" comment.
Leave a comment:
-
Leave a comment:
-
Usually, with most folks during normal conversation, when someone says "Believe what you want", it insinuates that they disagree with something you believe.. Since I never stated I believed anything, I found your comment confusing..
I find it an odd statement to make... so that's why I was confused.Leave a comment:
-
Usually, with most folks during normal conversation, when someone says "Believe what you want", it insinuates that they disagree with something you believe.. Since I never stated I believed anything, I found your comment confusing..
I find it an odd statement to make... so that's why I was confused.Leave a comment:
-
I'm confused.. What do you mean "Believe what I want" ??? Are you suggesting the output that my SMA Inverter is showing me is not accurate? Because that would be an issue for me..
If you're suggesting that PV Watts is not capable of accurately predicting my solar array production, that would make more sense... its not really possible for them to predict the weather so I would understand that...
I'm just saying their predictions are close to what I am experiencing, nothing more....
In the order you ask:
No. I'd bet once any initial startup glitches get identified and resolved, your inverter/monitoring will produce reasonable estimates of system performance in a fairly precise way.
As stated in the PVWatts help/ info screens, PVWatts will provide an estimate of long term average annual output. I've found it to do just that. However, it's not designed to give results of the type you seem to want to impart to it, that is, over a few weeks or months, with stated accuracy beyond 40% for individual months or 20% for individual years, and particularly with the level of accuracy you seem to want to ascribe to it - that 99.97% number.
I'm saying that using PVWatts for short term "predictions" is na
Add: 1540hrs., P.D.T.: Some of this post's output got clipped.
To continue: In short, What you are implying by using PVWatts over short periods and expecting it to verify your system's performance against expectations is, in spite of what ideas you may have to the contrary, simply not possible. What you get will be, if effect a comparison of system performance under two different weather conditions that may, or may not be similar.
What you do or think is NOMB. I only comment here so that others reading your posts about PVWatts and its misapplication and erroneous conclusions will not get the same erroneous notions about its capabilities and perhaps come to incorrect or at least non verifiable conclusions and then act on the bad information.
By way of possible analogy, climate is what you expect. Weather is what you get. PVWatts is probably decent at predicting the solar climate for a given location. It's not so good at predicting solar weather for short periods. To be able to do so would require accurate predictions of weather years in advance, and also have identical weather each calendar day of the year. Obviously, that's not possible and will not happen.
As I described in another, recent post, the ratio of the daily running 31 day PVWatts model output to the daily running 31 day variation in the running 31 day actual output of my system for 1,380 running data points of 31 consecutive days each was +/- about 65% to 13% or so 535 % or so. That is, over 1,380 running 31 day totals, the model's total solar output for any 31 day period could be +/- 35 of the system's actual output. That seems to agree reasonably well with the PVWatts estimates as published in the PVWatts help/info screens.Last edited by J.P.M.; 09-10-2017, 08:01 PM.Leave a comment:
-
Murby: Believe what you want, but as we several of us keep telling you, that's a coincidence.
When folks tell you what you might not want to hear, read or understand, it doesn't mean they are trying to hurt or lie to you.
Read the PVWatts help/info screens. I you've already done so, read them again because there's things you've missed.
If you're suggesting that PV Watts is not capable of accurately predicting my solar array production, that would make more sense... its not really possible for them to predict the weather so I would understand that...
I'm just saying their predictions are close to what I am experiencing, nothing more....
Leave a comment:
-
When folks tell you what you might not want to hear, read or understand, it doesn't mean they are trying to hurt or lie to you.
Read the PVWatts help/info screens. I you've already done so, read them again because there's things you've missed.Leave a comment:
-
UPDATE: First full power day was Aug 23rd. As of today (Sept 9th) , Per PV Watts spreadsheet, we are currently generating 99.97% of what they calculated we should be drawing. Wow.. Right on the money.Leave a comment:
-
sure, no problem. BTW- that radio is not a mystery and near high power AM station this could happen as the power of the station modulated by the sound transmitted.Leave a comment:
-
The blanket got wet from first 2 panel's condensation and static could no longer reach high enough potential? In case we consider static version of events. SMA inverters (others most likely too but it looks like you're using SMA) have ground fault detection circuit so it would quit producing power if it detected any leak so I'm fairly certain your install is OK.
I'm mostly worried about stray voltage idea SK suggested and Mike's induced AC one. Both can be checked by driving 2 metal rods in the ground (1' should be enough) where each of you were standing and measuring AC voltage (SK idea) or AC current (both) between those 2 rods however silly this might look. Just in case.
Its a mystery and probably going to remain a mystery.... Like one of those things were people claim they hear radio through their teeth filings..Leave a comment:
-
Definitely a fine looking installation. Add a few feet to the legs and it would work well in NHLeave a comment:
-
Nope.. If I go touch the panel there's nothing.. In fact, when we put the panel back onto the stack of unused panels we got nothing. The missing variable is that blanket we were wrapping them up in.. must have been something to do with it. Its just strange that it only did it with two panels... the last four didn't give us any shock at all.
Things that make you go Hmmmmmmm...
I'm mostly worried about stray voltage idea SK suggested and Mike's induced AC one. Both can be checked by driving 2 metal rods in the ground (1' should be enough) where each of you were standing and measuring AC voltage (SK idea) or AC current (both) between those 2 rods however silly this might look. Just in case.Leave a comment:
-
Nope.. If I go touch the panel there's nothing.. In fact, when we put the panel back onto the stack of unused panels we got nothing. The missing variable is that blanket we were wrapping them up in.. must have been something to do with it. Its just strange that it only did it with two panels... the last four didn't give us any shock at all.
Things that make you go Hmmmmmmm...
Leave a comment:
Leave a comment: