help please reduced output on hot days

[billybee]

thanks for the help, and sorry if you think i was arguing with the facts, i fully agree that i'm looseing that against the system at least 2% due to heat factors and my panels being a bit naff lol. and also some more looses due to 2 strings. i already had relized that an over sized inverter could cost me some performance and am made to fell worse now knowing i'm comparing against a system with an oversized inverter (700w) so i do realise the only way of improving is changing to 1 string (dont no how much diffrence) and blowing my panels up and getting better ones lol. so i have taken all your advice and am contacting my installer now to discuse the options. and trying to add more panels at a later date is also a no go going of the advice. so thanks you have all beeen very helpful and informative.

 

[Simpsod1]

Hi Billybee

I have a fairly similar system to you - Powerone PVI3000out and 13 250w suntech panels in 2 strings

Have you noted the temp reading on the inverter when the power drops??

I have noted that as soon as the inverter temp reaches circa 54c the output power drops from 3300w to 2450w - the inverter display will also change from Tinv to TBoost.

Hope this Helps

Dave

thanks for the help, and sorry if you think i was arguing with the facts, i fully agree that i'm looseing that against the system at least 2% due to heat factors and my panels being a bit naff lol. and also some more looses due to 2 strings. i already had relized that an over sized inverter could cost me some performance and am made to fell worse now knowing i'm comparing against a system with an oversized inverter (700w) so i do realise the only way of improving is changing to 1 string (dont no how much diffrence) and blowing my panels up and getting better ones lol. so i have taken all your advice and am contacting my installer now to discuse the options. and trying to add more panels at a later date is also a no go going of the advice. so thanks you have all beeen very helpful and informative.

 

[billybee]

massive massive help so is the 54c on the inverter the temp of the panels. is that what its telling you.

ive also relooked at the systems ive compaired with and on closer looking everyone one here was spot on with the heat situation as all the 4 system ar droping down to 85% of the max panel output on hot days weather the inverter is over or undersized. mines a bit worse at about 82%.

Hi Billybee

I have a fairly similar system to you - Powerone PVI3000out and 13 250w suntech panels in 2 strings

Have you noted the temp reading on the inverter when the power drops??

I have noted that as soon as the inverter temp reaches circa 54c the output power drops from 3300w to 2450w - the inverter display will also change from Tinv to TBoost.

Hope this Helps

Dave

 

[FB.]

Are you able to post-up the voltage (and ampage and wattage) of each string of panels?
If you have a dud panel, or a dud section of a panel, it ought to show up in the voltage.

For example, I have two arrays and the data a few minutes ago (cloudy) was:


Array 1:
8 panels, 232 Volts (8 x 29.0V per panel)
2.5 Amps

Array 2:
7 panels, 201 Volts (7 x 28.7V per panel)
2.5 Amps

If array 2 had a dud panel, it'd be running at 170-175 Volts (6panels x 29V) and obvious that there was a problem.

 

[billybee]

6 panels 165.1 (27.5)

6 panels 162.6 (77)

raing heavy, but its heat no heat and poor panels in heat. i will be keeping the inverter i have and looking at the string situation i think.

 

[Simpsod1]

P-out : Measured instant output power
The second line of the display shows the higher of two temperatures:T-inv: inverter heatsink temperature​

T-boost: heatsink temperature

massive massive help so is the 54c on the inverter the temp of the panels. is that what its telling you.

ive also relooked at the systems ive compaired with and on closer looking everyone one here was spot on with the heat situation as all the 4 system ar droping down to 85% of the max panel output on hot days weather the inverter is over or undersized. mines a bit worse at about 82%.

 

[billybee]

what is this t-vin and t-boost and what does it mean, could it be the inverter telling you panels are to hot or is it the iverter telling us its to hot. obvisally we both experance the same problem on hot days and its when t-boost kicks in.

 

[FB.]

6 panels 165.1 (27.5)

6 panels 162.6 (77)

raing heavy, but its heat no heat and poor panels in heat. i will be keeping the inverter i have and looking at the string situation i think.

So the voltage of each of the panels is very close between the two strings (27.5 v 27.1V).

The panels are operating close enough to their maximum power voltage (which varies with the weather conditions, but is in the high-20's).

I do note, though, that the Aurora 3000 string tool suggests that strings of 7 or 8 panels would be most optimal (probably due to string voltage).
Link here:
Power-One String Tool

Certainly the data sheets for the PVI-3600 which I have, says that it increasingly loses efficiency the further the string voltage is below 200V or above 530V. Generally speaking, below 200Volt, for the PVI-3600, a 10V drop equates to a 5% loss of inverter efficiency.
So you can see that my 7-string only just avoids dropping into the area where the voltage is a bit low and therefore less efficient.

It may be, therefore, that the modern trend for a few big panels is making problems with optimum voltage, or a greater effect on the whole string if one panel is shaded - for example 15x200W with one shaded panel is 6.7% loss of performance per shaded panel, but 12x250W is 8.3% loss of performance per shaded panel.
15x200W panels would run around 450Volts (or 210-240V if in two strings), whereas 12x250W panels would run around 360Volts as one string (or 180Volts if split into two strings and possibly failing to meet the optimum input voltage).

 

[FB.]

So basically you may be underperforming other systems because your panel strings are running below the optimum input voltage for your inverter, whereas other systems may be better matched.
In fairness, though, it isn't always possible to perfectly optimise due to each installation being unique and using the parts available at the time.

 

[billybee]

thanks for that its going into the hands of power one to look at.

thanks all

 

[ktech]

We had quite a few customers ask about the performance on higher temperature days and put an article together to explain: Solar and higher temperatures

 

[billybee]

very helpful info indeed, and well explaned. if i had known this info i would have probabley pushed me towards a diffrent panel. and there no dobt that heat on the panels are playing a big part in my reduced peaks on hot days. but as has been explaned also the two strings doesnt help and probably as someone said earlyer the t-boost thing that cuts the inverter down may be adding to the looses, but its in the hands of power one to look at this issue more. the info on here has been a big help and i hope future panel buyers can see your info so there more ready for this sinario as it was a bit of a shock.

 

[Gavin A]

what is this t-vin and t-boost and what does it mean, could it be the inverter telling you panels are to hot or is it the iverter telling us its to hot. obvisally we both experance the same problem on hot days and its when t-boost kicks in.

those are the temperatures at the heat sink on the inverter. I believe they need to be showing 70 degrees before derating occurs

automatic power limitation control based on internal temperature monitoring to avoid overheating (heat sink temperature ≤70°C [158°F]).

One point on this though is that if the efficiency is 3-4% lower than peak, then this means there is 3-4% more power being converted to heat, which means that at 3000W input, there's an extra 100W or so of heat being generated in the inverter, which does make it far more likely than usual that the inverter will overheat and derate because of it.

so running it in single string mode could also resolve this issue if it is an issue here.

 

[Gary K]

I believe the power 1 inverters use heatsinks and cooling fins rather than an internal fan so it would do no harm to get a large fan blowing on the inverter from early before it gets warm so to limit the heat build up. It may help. The inverter is not mounted in an enclosed space or warm loft is it?

 

[Gavin A]

I believe the power 1 inverters use heatsinks and cooling fins rather than an internal fan so it would do no harm to get a large fan blowing on the inverter from early before it gets warm so to limit the heat build up. It may help. The inverter is not mounted in an enclosed space or warm loft is it?

they have internal fans inside the sealed unit to blow the warm air onto the heat sink / away from the components, but not external fans to blow air over the heat fins.

An external fan in the wrong position could even make things worse by preventing the convection air circulation (the chimney effect) from working properly and drawing air across the heat fins if it was positioned badly.

If the internal temperature is 54, then I don't see that this is going to be causing it to derate, unless Power-One are giving out duff information, though it does seem warmer than would be ideal for the lifespan of the components.