Been fiddling around and learning more with the panels.
I bought 5KW of 250W panels the other week and have tested them and set them up as an array. I have 2 arrays set up now, one with 2.5Kw of panels tilted on the scaffold in the right orientation and degree and the other with a total of 3250W lying flat on the lawn.
This has been interesting in itself.
On sunny days the tilted panels will tend to make more than the flat panels. On cloudy days the flat panels do a fair bit better. The 2.5Kw aray is on a 2Kw inverter and the other setup is on a 3Kw inverter. best I have seen so far is 1980W out of the 2.5 array. The other tends to sit around 1.8 quite consistently in full sunlight for several hours of the day. Biggest shading problem has been the cat siting on a panel on the cooler days for the warmth. On the hotter days he sits under them getting the shade but the radiated heat at the same time.
I have been battling the phase going high once the power levels go up. tried a few things with that but nothing worked. once I added the second array I could only run one at a time through the middle hours otherwise the inverters would trip out. I thought I'd just let them do that but it killed output. they would take about 3 min to reset then run for 5 sec then default and go into test mode to rest again. Sometimes one would trip and the other would hold but often they would both trip and the power losses during the down time really knocked the daily KWH figures.
I am running long extension leads and always was concerned about that. I was reading things and learned what should have been obvious, Voltage drop works both ways. You loose when you are trying to pull through but you get a bottle neck when you are trying to push. the resistance of the wire rather than dropping the voltage at the outlet end was causing the inverters to see a higher voltage at their end. I had seen this with testing the circuit at another point and at the inverter end but thought that may have been because of local loads taking the edge off at the connection side.
Thinking of the resistance, I got out a 1.5mm extention lead to replace the standard 1mm cabled conductors and I re wired the plug from the inverter in 2,5MM cable.
On the other inverter i did the same to the plug and also made a 25M extension cable from 2.5mm. It certainly helped but didn't cure the problem. I figured the feed in points were just too close together and the circuit didn't have enough load and that was all I could do in this testing setup. Each array was working well and delivering good output for it's limitations and I'd have to wait to get them on the roof and wired properly to see them really working hard.
I have been turning one set of panels off during the middle of the day and back on about 3PM. this works well as something else I have concluded along the lines of over paneling the inveters is it's not the peak output that makes the difference to the days total generation, it's the mornings and afternoons.
Having the 2 arrays running in the ramp up and down would allow the same output as the middle of the day for much longer and because the total was the same, the line voltage wouldn't go high and trip one inverter out. having a peak output for 2-3 hours a day longer made a big difference to the much faster fall off of either arrays singularly. Although a bit difficult to test as the light changes faster than one would normally realise, the output total of both inverters seemed to be greater than the sum of the outputs individually.
Not sure how that works, maybe the higher line voltage made for greater efficiency in converting the high volt, lower amp output of the panels.? About the only thing I can think of to explain it? Seemed a case of 2+2 = 4.5
Today while wanting to add in some more power outlets to the house , I was studying the circuit breakers and saw that there were 2 circuits sharing the phase I am back feeding. I ran a lead from one of the inverters to the other circuit and although on the same phase, resulted in a MUCH lower combined voltage. I measured the phase at a 3rd point and it was much lower as was the voltage the inverters were reading. It was well past peak sun but the 2 arrays were producing the max output I can get before either inverter trips out which is about 2KW. I had over 4 Kw of panels on the 3 Kw inverter at one stage but as soon as it went over the 2kw output, the line voltage went high and it tripped out. I had to remove some panels to keep the output down so the thing wouldn't reset constantly even though it was under the inverter and the circuits rating by a long shot.
I'm hoping tomorrow that I will be able to run both arrays flat out all day. If I can get around 3.5 Kw max, maybe 4, it will certainly make a big difference over the 1.8 Kw peak I have been seeing as an average out of either inverter. I still have some panels spare doing nothing so I may be able to splice them back in and run nearer the inverter max and get even more output.
What I can see would be useful is a device that would allow one to severely over clock the inverter and dump control output.
the controller would monitor the array output and being oversize would allow a lot closer to full output morning and afternoon. In the middle of the day when the array got to the inverters max, instead of the inverter just clipping and wasting the power, it fed it to the dump load. once the output dropped back town to full inverter level, it would send the power back to the main circuit. Sounds like something else I have read about and probably could be adapted from some other controller.
Tomorrow is forecast to be mostly clear but I'll be happy to get a clear hour around midday so I can see if both arrays can sustain full power output without the line voltage going too high. I have around 23V rise to play with and was well short of that this afternoon at normal max power so see how I go.
If I get the interfering tree " Pruned" ( about 12 ft lower) this weekend I'll have the shed roof clear and I'll start on building my framework to hold the 5 Kw of panels I want to put up there next week.
Mucking around with this really has been a fun and profitable learning experience. Just hope I can remember most of what I have learned once I have it in place and aren't fiddling with it and watching what happens every day.