Solar PV monitoring

[rusty]

My solar panels have never performed as well as expected after being fitted nearly 4 years ago. I have had the following proposal. What do forum members think?

The Client has one 49.5KWp rooftop solar array which has not been regularly tested/inspected and the system is known to be underperforming to the extent that revenues of circa £54,000 would be lost over the remaining lifetime of the PV array unless action is taken. RT’s Onsite HealthCheck is will identify the cause of such underperformance. Similarly, a lost summer month of generation would cost circa £814 in any event. In order to mitigate the risk of underperformance, the Client wishes to outsource the monitoring to a specialist third party. RT’s service uses weather satellites and algorithms to automatically calculate the solar irradiation received by the system and compare it with the electricity production measured by its onsite equipment. RT identifies deviations in array performances and notifies its Client’s where these point to an economically-significant issue. RT’s monitoring solution will also reduce the recommended frequency of solar test & inspection visits. The Client wishes to make more efficient use of the engineer that will be carrying out the Onsite HealthCheck by having RT’s monitoring equipment installed during the same site visit. Services 1. Electrical test & inspection to BS7671 18th Edition Wiring Regulations by an electrical engineer qualified to Test and Inspection of Electrical Systems 2391 and Solar Installation Certificate 2399 2. Corresponding test & inspection report and recommendations 3. Five years remote monitoring and reporting of relative solar PV performance of two arrays Note: Array performance data to be analysed on working days only, but with reference to 365-day performance data Fees Electrical test and inspection: £599+VAT Annual PV performance monitoring (based on five-year contract): £549+VAT Note 1: Stated fees are based on a bundled price of all services above Note 2: Monitoring service subject to RPI and invoiced annually in advance

 

[upnortheast]

As regards monitoring, just read the meter once a week. Cost - nowt
Arrange for solar producers on TFF ( Someone like @Exfarmer knows a lot of stuff )to put up regular data for comparison Cost - nowt
Then decide the scale of your problem & seek advice from TFF members - cost - nowt
then decide if you need to pay a specialist solar sparky to take a look

 

[rusty]

I read all the meters once a month and record the results. One of the problems is that the panels get very dirty so I am going to get them cleaned twice a year now that I have found someone to do it at a sensible rate. I also noted that they monitor only two arrays and their are actually 3 to my knowledge, there are 3 inverters anyway.

 

[Exfarmer]

Thanks for the compliment!
Rusty, why are you sure it is underperforming?
firstly do you know the angle of the roof to south?
The pitch of the roof, I am assuming it is on a roof.
Is there any shading? assessing this can be difficult
Have you any dust issues, can be serious on a stock, feed, grain store.
Can you post your output figure, monthly would be good, but annual will give a good idea.
It may be you do have a string, strings out, but I would look at other factors first.
I would not give to much credence to claims that satellite monitoring will be of much benefit, the output on individual sites vary quite markedly day to day due to cloud but over the months they tend to follow each other fairly closely

 

[rusty]

Thanks for the compliment!
Rusty, why are you sure it is underperforming?
firstly do you know the angle of the roof to south?
The pitch of the roof, I am assuming it is on a roof.
Is there any shading? assessing this can be difficult
Have you any dust issues, can be serious on a stock, feed, grain store.
Can you post your output figure, monthly would be good, but annual will give a good idea.
It may be you do have a string, strings out, but I would look at other factors first.
I would not give to much credence to claims that satellite monitoring will be of much benefit, the output on individual sites vary quite markedly day to day due to cloud but over the months they tend to follow each other fairly closely

Will try and post some figures this evening

 

[upnortheast]

My 1st impresion of the OP post was these people were going to charge £3000 over 5 years for something you could easily work out yourself, with a little help from the good folk on TFF

 

[rollestonpark]

Our array has a Solar Log fitted to it, the device emails me every night to tell the percentage of target for the day it's done and the percentage of target for the month and year, so far.
The target percentage varies through the year , to account for the sun's height and day length etc.

Works well, and it's easy to see when something bad has happened (inverter broken) because the output is 0 and your told every night.

could be an option for you.

 

[Exfarmer]

One other point, are you at a remote place? If so could you be having over voltage issues, with the line not being able to take enough power from you.
We have this at one site, which is still an ongoing issue. One phase is getting so high voltage at peak periods the inverters, quite correctly shut down. We believe the reason is because a neighbouring farmer , who is the end of the line has got 30KW solar install on single phase. We have no idea how he got DNO permission for it!
Our own inverters have registered 305 volts on one of the phases ( we obviously have no idea which one he is plugged into but can guess )
It is possible that your inverters are cutting out at times of peak production. Most inverters will allow you to quiz them quite simply and they will reveal max voltage, I think the max voltage should be in the order of 254.
In lay mans terms, put simply, the inverters will have to push the voltage above the grid level to push your power into system

 

[f0ster]

253vac is the max that any inverter should not exceed due to its internal settings for the UK, as soon as it reaches this upper limit it will shut down and do a restart, it it still sees this upper limit exceeded it will keep restarting, it is very common to have voltage up at this level the further out in the country you get. we had a customers system causing this fault so the dno put a data logger on the line, he would no do anything because the253vac upper limit was only exceeded occassionally he stated. the 4kw system was detecting this upper limit was being breached continually so his solar system was of no use to him. there was a solar farm down the road so this might have been the main cause. if you have this issue the cure is easy if you think outside the box. inverters do not usually produce a fault code for high voltage.

 

[Exfarmer]

253vac is the max that any inverter should not exceed due to its internal settings for the UK, as soon as it reaches this upper limit it will shut down and do a restart, it it still sees this upper limit exceeded it will keep restarting, it is very common to have voltage up at this level the further out in the country you get. we had a customers system causing this fault so the dno put a data logger on the line, he would no do anything because the253vac upper limit was only exceeded occassionally he stated. the 4kw system was detecting this upper limit was being breached continually so his solar system was of no use to him. there was a solar farm down the road so this might have been the main cause. if you have this issue the cure is easy if you think outside the box. inverters do not usually produce a fault code for high voltage.

We had a max of 305 volts on one phase. The DNO did not believe me till they put a logger on the line, they said it was one of the highest they had ever seen. We saw over 500 volts on the 3 phase. The logger is still there 18 months later.
We know a guy the next farm down had a brand new computer burst into flames, whether it was linked I am not sure, but would not be surprised.
They are due very soon to replace everything and the site will be upgraded from 100 Kw to 350kw, if only the FITs were still going!
I do think the plethora of solar farms cannot be helping

 

[curlietailz]

My solar panels have never performed as well as expected after being fitted nearly 4 years ago. I have had the following proposal. What do forum members think?

The Client has one 49.5KWp rooftop solar array which has not been regularly tested/inspected and the system is known to be underperforming to the extent that revenues of circa £54,000 would be lost over the remaining lifetime of the PV array unless action is taken. RT’s Onsite HealthCheck is will identify the cause of such underperformance. Similarly, a lost summer month of generation would cost circa £814 in any event. In order to mitigate the risk of underperformance, the Client wishes to outsource the monitoring to a specialist third party. RT’s service uses weather satellites and algorithms to automatically calculate the solar irradiation received by the system and compare it with the electricity production measured by its onsite equipment. RT identifies deviations in array performances and notifies its Client’s where these point to an economically-significant issue. RT’s monitoring solution will also reduce the recommended frequency of solar test & inspection visits. The Client wishes to make more efficient use of the engineer that will be carrying out the Onsite HealthCheck by having RT’s monitoring equipment installed during the same site visit. Services 1. Electrical test & inspection to BS7671 18th Edition Wiring Regulations by an electrical engineer qualified to Test and Inspection of Electrical Systems 2391 and Solar Installation Certificate 2399 2. Corresponding test & inspection report and recommendations 3. Five years remote monitoring and reporting of relative solar PV performance of two arrays Note: Array performance data to be analysed on working days only, but with reference to 365-day performance data Fees Electrical test and inspection: £599+VAT Annual PV performance monitoring (based on five-year contract): £549+VAT Note 1: Stated fees are based on a bundled price of all services above Note 2: Monitoring service subject to RPI and invoiced annually in advance

Hi
I have a domestic system 2 x 4kwh so may not be applicable to your original wuestion
But I got a Solar Edge system fitted... I can monitor individual panels real time , can see how one string compares to the other etc
It’s definitely worth looking at
Don’t know if it could be retro fitted though
BTW I don’t clean the panels

 

[tanker]

One of the problems is that the panels get very dirty so I am going to get them cleaned twice a year now that I have found someone to do it at a sensible rate.

Do you mind me asking what sort of price he's charging? Our 40kw is quite grubby all of a sudden and it's something I need to explore...

 

[rusty]

Output from my FIT statements

Year	Period	Generated	Exported					4Q total
2015​	Q3	3990​	0​					generated
	Q4	2296​	0​
2016​	Q1	11033​	6059​	Export meter finally connected
	Q2	11134​	6549​					28453​
	Q3	5146​	2293​
	Q4	645​	55​
2017​	Q1	4152​	2155​	Panels cleaned
	Q2	9120​	5284​					19063​
	Q3	3724​	2117​
	Q4	719​	36​
2018​	Q1	4307​	1133​
	Q2	4666​	1624​	Accidentilly turned off for 3.5 weeks	​			13416
	Q3	2911​	327​
2019​	Q1+2018Q4	4184​	1719​	Panels cleaned May 6th
	Q2	8409​	4895​					15504​

 

[rusty]

Do you mind me asking what sort of price he's charging? Our 40kw is quite grubby all of a sudden and it's something I need to explore...

I used this guy https://johncarrcleaning.com/

His charges were £1/panel (£4/kw) if he can link it in with other jobs. He does quite a bit in Cheshire. As mine were so dirty and it took a full long day I paid for hire of his cherry picker as well which about doubled the price this time.

predicted output of my system was 34,106Kw /year
Kk rating was 851 with a shading of 1 and AC output of 42174

 

[tanker]

Ok, thankyou for that,interesting stuff..

 

[rusty]

Thanks for the compliment!
Rusty, why are you sure it is underperforming?
firstly do you know the angle of the roof to south?
The pitch of the roof, I am assuming it is on a roof.
Is there any shading? assessing this can be difficult
Have you any dust issues, can be serious on a stock, feed, grain store.
Can you post your output figure, monthly would be good, but annual will give a good idea.
It may be you do have a string, strings out, but I would look at other factors first.
I would not give to much credence to claims that satellite monitoring will be of much benefit, the output on individual sites vary quite markedly day to day due to cloud but over the months they tend to follow each other fairly closely

This is the cubicle shed the panels are on. this side gets much dirtier than the other side. We bed with fine sawdust and have pretty open sides. The prevailing wind comes through the shed and exits on the side you can see. I think there must be some kind of vortex effect that dumps a lot of the sawdust back on the roof. Having said this there are no cows in for 6 months in the summer and although cleaning does show a benefit , output is still not where it was in the first year which was a bit below expectation.

 

[Exfarmer]

Why was the predicted output so low?
I would have been tempted to think they are on the north side, but you obviously hade the choice of side.
Normally panels easily out perform prediction as the figures used are standards which were set some time ago.
I wonder if all the strings are working?
The other point, have you looked at the inverter output figures. We had one set up where they had not balanced the output in a big way check the output phase figures

 

[matthew]

We have a similar system, on two roofs as yours. Pitch is 30 degrees on the y/stock building and 45 on the silage barn. Installed Dec, 2013.
Output to September 1st 2019 was 300, 010. So over 50,000 kw per year.
Panels not cleaned. Yet.

No problems except one inverter blew, but after a rattle at the CEO’s door, was replaced quickly and down time paid.