Fronius inverter 8.2

[diogenes]

I have only had my system for a couple of months, but I am starting to worry, I have a Fronius Primo 8.2 1 inverter, It is clipping at 8.2 Kw, using a 10 kw Canadian Solar panel setup. I realize this is normal, but the clipping is for almost an hour on a good day, Is my invertere "underpowered" for my system?

[sensij]

You are probably fine. Cold, clear days when the sun is at a good angle to the array is when you are most likely to clip... February into April for many designs. The amount of energy lost during that clipping period isn't really much, if you compare ideal output to what you are actually producing. Have you figured out how to upload your data to PVOutput.org yet? I'm pretty sure you can do it automatically with that inverter, and with more access to the data, a better idea of how much you are losing can be provided.

[diogenes]

yes
pvoutput link

http://pvoutput.org/list.jsp?userid=43410

the dip yesterday was caused by my reseting the inverter due to a problem with the loss of connection to my local lan

this actually shows output for the day better
https://www.solarweb.com/Account/Gue...a-5d7e52bde016


archive feb 10 2016 shows the clipping very well

[diogenes]

clipping

and I am at 35 deg W latitude with a panel tilt of 28 degree

[J.P.M.]

If you run PVWatts w/~ 10% system losses and use the hourly output, or SAM, you'll see that max. hourly output this time of year at Chattanooga is about 8,500 Watts +/- some. So, there will likely be clipping as you are finding out. But, and as Sensij writes, I doubt if it'll be much on an annual basis. Depending on price, availability and system parameters, I might have opted for the next largest size, depending on what the NPV of estimated lost production might be. But you got what you got, and it probably won't lead to economic chaos.

As a note to potential PV users and not kicking you when your down, but this is the type of stuff that happens w/out knowing what can happen. Know what you're getting into, how it works, what can happen and the consequences. Another example where knowledge is again power.

In this case, it may not be a costly situation, depending on weather, future system degradation and other things.

As usual, take what you want of the above. Leave the rest.

[sunnyguy]

yes
pvoutput link

http://pvoutput.org/list.jsp?userid=43410

If not too much trouble could you update your system profile with accurate equipment and tilt/azimuth data? A lot of people on pvoutput search by equipment to try and get a relevant performance comparison. Thanks!

P.s. - you know fronius can push live data to pvoutput every 5 min, right?

P.p.s - if your connecivity problems continue you may want to try and remove and reseat the data card.

[DanS26]

Check your time zone settings before going to 5 min updates to pvoutput.org

[diogenes]

thanks, guys, good info, thanks JPM you are right, it is what it is. and according to pvwatts it will get better.

[DanS26]

Take a look at today's clipping. Cold and sunny with cloud effect refraction. See that flat line at 15 kW...that's clipping



My 17.28 DC kw system clipped at 15 AC kW when conditions are right. Yes some loss but not to the extent that you have to over size the inverters.

I think most designers would be OK with a 15% over sizing DC to AC. You are at 22%, so maybe a little undersized on the AC side, but not significant.

ps: For you old timers...see the red line from 10am to around 12:30 pm... that is my ETS (electric thermal storage) system collecting excess solar energy to then release that energy as heat early next morning.

[diogenes]

yep clipping is fun, this was a great day, but still clipped, my eyeball says maybe 1% loss from clipping

[FFE]

Sometimes your electrical service panel is the limiting factor on the size of your inverter. I can only come up with one scenario and It would be very rare for this to be your situation. So, I doubt this is the reason. Unfortunately some installers design systems this way and don't inform the buyer or give them the option to install fewer PV panels. Clipping sucks but like other have said in reality the lost energy is a vey rarely more than a very small portion of your anual production.

[J.P.M.]

thanks, guys, good info, thanks JPM you are right, it is what it is. and according to pvwatts it will get better.

You're welcome. FWIW, to reiterate, I don't think it's a disaster or even that much of a big deal. On PVWatts, that's only a model to estimate long term performance. Using it as I've done here is a bit of a bastardization to model possible clear day output by using the hourly option to pick out estimated output on clear days around some date for which actual clear day performance is/has been measured. It is in no way rigorous. It can be however, also be one way to estimate a value of the system loss parameter in PVWatts: That is, make the PVWatts hourly output for a measured and monitored clear day match the actual system output by adjusting the system loss parameter. BIG CAUTION: Keep in mind that the PVWatts TMY weather parameters of wind and ambient temp. will be different fron the actual weather on site and will skew results. That's one reason why the method is still an SWAG/estimate. Clear days where both model and actual wind and temps. are similar may have a better chance of being closer.

[diogenes]

You're welcome. FWIW, to reiterate, I don't think it's a disaster or even that much of a big deal. On PVWatts, that's only a model to estimate long term performance. Using it as I've done here is a bit of a bastardization to model possible clear day output by using the hourly option to pick out estimated output on clear days around some date for which actual clear day performance is/has been measured. It is in no way rigorous. It can be however, also be one way to estimate a value of the system loss parameter in PVWatts: That is, make the PVWatts hourly output for a measured and monitored clear day match the actual system output by adjusting the system loss parameter. BIG CAUTION: Keep in mind that the PVWatts TMY weather parameters of wind and ambient temp. will be different fron the actual weather on site and will skew results. That's one reason why the method is still an SWAG/estimate. Clear days where both model and actual wind and temps. are similar may have a better chance of being closer.

yeah, I take all TMY data with a grain of salt, I live in the wilds of southern TN, and the closest TMY position is 29 miles due south. plus we are 500 ft higher than them and in a different climate zone.

[sensij]

For many places without a nearby TMY site, there is within NREL's tools an option to choose "Solar Anywhere" data, based on processing satellite data to determine irradiance.

The cost to go from an 8.2 to a 10 kW inverter looks like around $600. Also, the OP would be required to carry higher liability insurance on the array once the 10 kW threshold was met. I think the 8.2 was definitely the more cost effective choice in this case, even with some seasonal clipping.

[J.P.M.]

For many places without a nearby TMY site, there is within NREL's tools an option to choose "Solar Anywhere" data, based on processing satellite data to determine irradiance.

The cost to go from an 8.2 to a 10 kW inverter looks like around $600. Also, the OP would be required to carry higher liability insurance on the array once the 10 kW threshold was met. I think the 8.2 was definitely the more cost effective choice in this case, even with some seasonal clipping.

Can't hurt. I've found it about the same as most nearby TMY data. Given that most all of it is either somewhat estimated - the Solar Anywhere data, or synthetic - most of the TMY irradiance, it's good to remember it's all an estimate with very little of it from actual ground measurements.