enphase s280 with LG315N1C-G4

[Willaby]

If the most cost effective, long term solution is one of the goals, one way to look at it is to size a system that produces the lowest LOCE for the parameters the person paying for the system and the resulting bill sets. Unfortunately that often take a bit of homework.

I'm thinking more about payback and ROI (I had to look up "LOCE"). Think about it this way, you could over pay for your system by $1/kw but under-sizing (or should I say "not right-sizing") without consideration for change (that is a given) could cost you much more over the system life.

Ah well, certainly worthy of it's own topic, maybe if I get around to it.

[J.P.M.]

I'm thinking more about payback and ROI (I had to look up "LOCE"). Think about it this way, you could over pay for your system by $1/kw but under-sizing (or should I say "not right-sizing") without consideration for change (that is a given) could cost you much more over the system life.

Ah well, certainly worthy of it's own topic, maybe if I get around to it.

LOCE is one way of many. My point was that folks may be looking for the most long term bang for the buck, and there are as many ways to do that as there are people to make the effort. One other way is to do some comparison of alternative type analysis. For example, and depending on one's view of the future and time horizon, it's certainly possible to compare 2 scenarios ( or any # for that matter) and see what may happen to a sum of money over the chosen time frame when invested in each alternative, with the possible goal of choosing the one alternative that, in the opinion of the asset holder the best combination of risk/benefit. Bury in the ground - zero return and suffer the ravages of inflation, but close to zero risk of loosing any capital. Stock index fund - depending on risk tolerance, better. Corporate bonds - some risk, probably a nominal to decent return and a fair chance of return of all capital at the bonds' maturities, as well as some access to the capital in an emergency. Solar - lower electric bills, and a bunch of tax credits, but a bit more uncertainty in the analysis, partly because of a lot more variables to consider.

Not all considerations are financial, but the financial ones are usually considered and usually top the list.

[randomuser]

I'm wondering if I had the S280 micro-inverter, would it show a max of 280W on each panel? That's pretty good panel production on my 320W panels. Screen Shot 2016-05-21 at 4.22.06 PM.png

[Engineer]

I'm wondering if I had the S280 micro-inverter, would it show a max of 280W on each panel? That's pretty good panel production on my 320W panels.

What are you using now?

[ButchDeal]

That is solarEdge

[jetsurgn]

Wow nice numbers randomuser.

[randomuser]

Thanks, Jetsurgn. That screenshot a few posts up was from yesterday. Just now, I went and looked at high points for today and it looks even better. I didn't know we're able to get 315W output from a 320W rated solar panel? Also, my 5.44kW system had a peak of 5.335kW? I'm guessing these reports aren't 100% accurate but things look good. This system was just installed a month ago, so I guess this is the time when the panels will perform the best and it's just downhill from here on out.

[Engineer]

OK yeah those would peak at 280 with the Enphase. do you have output data in tabular or graph format for one of those panels? If so do an integration for the time spent above 280 and let us know the integrated energy. San Diego is in the Red Zone, curious if a lower output micro would lead to appreciable losses.

[sensij]

On partially cloudy days, it isn't too hard to get reflections for the clouds that increase the local irradiance beyond what it would be on a clear day, for short periods of time. Yesterday, my irradiance meter was reporting over 1200 W/m2 of GHI, and on Thursday, at over 1100 W/m2, my 1 year old 3120 W array still managed to get my 3000 W inverter into clipping (for 5 minutes).

[J.P.M.]

On partially cloudy days, it isn't too hard to get reflections for the clouds that increase the local irradiance beyond what it would be on a clear day, for short periods of time. Yesterday, my irradiance meter was reporting over 1200 W/m2 of GHI, and on Thursday, at over 1100 W/m2, my 1 year old 3120 W array still managed to get my 3000 W inverter into clipping (for 5 minutes).

Yesterday and today had some unusual solar weather. As Sensij notes, his pyranometer went > 1,200 Watts/m^2 GHI. Mine was past 1,000 W/m^2 several times yesterday for 10-20 min. duration. Today had an unusual period from 1153 - 1221 hrs., P.D.T. of between 1,050 and 1,120 W/m^2, and again from 1248 - 1310 of between 1,035 and 1,1200 + W/m^2 GHI, with one 7 min. period past 1,200 W/m^2. The smoking gun on cloud reflections as being responsible for the high reading is that the data is very irregular with minute/minute changes of 10-50 W/m^2. (another tipoff was looking outside and seeing clouds - DUH ! - I was really on my game today.) Also, the ambient temp. was relatively low and I had a fair wind blowing, both of which helped keep the array temp. down. I had clipping as the 5 kW inverter output pegs out occasionally at 5,030-5,035 W, if the inverter screen is to be believed, and today it stayed there today from ~ 1150 -1220 P.D.T. and ~ 1250 - 1310 P.D.T. The best clear sky output I've ever had was ~ 4,850 Watts out of the inverter.

BTW, the P.O.A. irradiance is about 3 - 4% greater than the GHI this time of year around solar noon in this area for ~ 20 deg. tilt mostly south facing orientations, but that's under cloudless skies.

[jetsurgn]

I've seen the M250's peg out over 255, will the S280's get to 285?

Enphase will have a S290 followed by the S300 soon, although I'll admit a little late to the party.

[Willaby]

Yesterday and today had some unusual solar weather. As Sensij notes, his pyranometer went > 1,200 Watts/m^2 GHI. Mine was past 1,000 W/m^2 several times yesterday for 10-20 min. duration. Today had an unusual period from 1153 - 1221 hrs., P.D.T. of between 1,050 and 1,120 W/m^2, and again from 1248 - 1310 of between 1,035 and 1,1200 + W/m^2 GHI, with one 7 min. period past 1,200 W/m^2. The smoking gun on cloud reflections as being responsible for the high reading is that the data is very irregular with minute/minute changes of 10-50 W/m^2. (another tipoff was looking outside and seeing clouds - DUH ! - I was really on my game today.) Also, the ambient temp. was relatively low and I had a fair wind blowing, both of which helped keep the array temp. down. I had clipping as the 5 kW inverter output pegs out occasionally at 5,030-5,035 W, if the inverter screen is to be believed, and today it stayed there today from ~ 1150 -1220 P.D.T. and ~ 1250 - 1310 P.D.T. The best clear sky output I've ever had was ~ 4,850 Watts out of the inverter.

BTW, the P.O.A. irradiance is about 3 - 4% greater than the GHI this time of year around solar noon in this area for ~ 20 deg. tilt mostly south facing orientations, but that's under cloudless skies.

So, what do you think is most responsible for the spikes, since clouds and low temps go together? Back in mid-March I happened to be at my inverter at noon on a cool, scattered cloud day and saw output spikes over 105% of STC as the clouds rolled by. These were live readings. I'm inclined to think most is attributed to low temps since the panels cool under the clouds, then take a few minutes to warm up again. On that day, at .5% per 1 degree C, I think those panels could have been 30, maybe 40 degrees cooler than full sun, so maybe up to 20% more productive. Clouds would certainly be more variable to measure, but I'd guess it wouldn't exceed 10% or so by themselves?

[J.P.M.]

So, what do you think is most responsible for the spikes, since clouds and low temps go together? Back in mid-March I happened to be at my inverter at noon on a cool, scattered cloud day and saw output spikes over 105% of STC as the clouds rolled by. These were live readings. I'm inclined to think most is attributed to low temps since the panels cool under the clouds, then take a few minutes to warm up again. On that day, at .5% per 1 degree C, I think those panels could have been 30, maybe 40 degrees cooler than full sun, so maybe up to 20% more productive. Clouds would certainly be more variable to measure, but I'd guess it wouldn't exceed 10% or so by themselves?

Cloud reflection is responsible for most all of the spikes.
Clouds and low array temps. sometimes tend to go together, but I don't believe it's valid to make that as a blanket statement, particularly under the transient conditions of partly cloudy skies.
Panel or array temps. cannot change quickly enough to see the rate of increase per minute observable under partly cloudy conditions..
5% over STC around solar on a south facing array would probably mean something like an ~~ 15-20 % increase in P.O.A. irradiance, and as Sensij and I have observed and recorded, that's possible, but not an everyday occurrence.

A panel or array under partly cloudy skies will tend to have an average temp. that can be estimated by an energy balance on the panel or array using the time averaged P.O.A. irradiance.

Any fluctuations in output as a result of array temp. changes usually have a rather small time rate of change, as can be seen by watching the array voltage which are f(array temp.) which, on a partly cloudy day, change at a slower rate than array current which is f(P.O.A. irradiance), and can therefore change much more quickly.

Under clear skies and ~ 1,000 w/m^2 P.O.A. irradiance, my array runs ~ 28-30 deg. C above roof ambient air temp., maybe a bit less with a strong wind. Given my rough estimates for the thermal time constant for the array, I'd calc. that it takes my array about 1- 2 minutes or so to drop 1 deg. C. if/when the irradiance is cut from, say, 1,000 W/m^2 to, say, 200 W/m^2. It's close to impossible for me to measure/monitor the array temp. that closely, but my gut tells me that's probably a decent SWAG, particularly after watching the array voltages @ the inverter for the last 2 yrs.

An array's temp. simply does not change quickly enough to have output fluctuate as quickly as can be observed on partly cloudy days.

I doubt most any array will operate at a temp. differential 40 deg. C above ambient unless it's in a very wind sheltered area with a lot of intentional irradiance enhancement such as from booster mirrors or some other irradiance augmentation scheme, or if it had an insulated backside, or a second glazing on the front, both of which would be senseless.

If the array temps. are 30 C. above amb. and the amb. is 25 C., with a temp. coeff. of eff. of, say, - 0.5%/deg. C., the array will run ~ 15 % less efficient than when the array is at its STC temp. , and probably a good deal less than 15 % more efficient compared to most operating conditions.

Cooler array temps. produce better operating efficiencies. Cloud reflections produce more output, but always of a temporary nature. The first is a slower process than the second.

Take what you want of the above. Scrap the rest.

[randomuser]

Good to know I don't have any defective panels. I'm now wondering what's the max output I can get from a panel? I've got P320 optimizers on 320W panels. Is the power optimizer the limiting component or the panel?

[sensij]

I doubt the optimizers are limiting.