Best KWH production today on my new 20KW System!

[bcroe]

Collected 124 KWH on March 15 when for once the clouds disappeared. Friday they predict
pure sun, maybe that is what you just had. Bruce Roe

The sun delivered full power almost all day; that only happens once or twice a month. Did 134 KWH, which shows
how much the days have lengthened since 15 March. The best ever, June, was 149 KWH. With clipping almost
always under good sun, output does not fall off in summer. Bruce Roe

[Truenorth]

JPM- So do you just hose your panels down to clean them?

Dan - I thought I read that you have a geothermal heat pump, I have one as well and my consumption is running the same as yours 70 to 100kwh daily average. Should drop off significantly this summer as we don't use AC often. Doesn't look like the clipping affects you much!

Bruce- 149 kWh peak..nice! wish I could add some more panels but am pretty well maxed out with my inverters. I'm limited to 20 kw with my utility anyway.

[DanS26]

.............Dan - I thought I read that you have a geothermal heat pump, I have one as well and my consumption is running the same as yours 70 to 100kwh daily average. Should drop off significantly this summer as we don't use AC often. Doesn't look like the clipping affects you much!.........

No, I do not have a geothermal heat pump, but I did attach a Nyle heat pump to my LP gas water heater. I have it on a timer so that it only operates from late spring to late fall and then only during daylight hours. In effect it only runs on solar PV energy. I call it my "too good to be true project"......heats my water, dehumidifies my basement, cools my house (rated as 1 ton AC) and runs on solar PV......just doesn't get any better than that.

What you may be referring to is my investment in ETS (electric thermal storage) systems. Storing PV energy as heat in ceramic bricks is a controversial subject on this site but it works for me since I use the systems to heat specific smaller spaces as opposed to heating large spaces such as unused upstairs bedrooms. The heaters are also timed so that they are only charged during daylight hours. Since my kWh production costs are low and since I am on a net billing rather than net metering system it is an effective heating strategy for me.

[Truenorth]

Dan, sounds like a great system! Looks like there are many alternative energy solutions yet for me to explore

[J.P.M.]

JPM- So do you just hose your panels down to clean them?

Short answer to a very long(winded) story: Yes.

Slightly longer answer: After measuring input, output and a bunch of other intermediate stuff for the last 3 years, I've formed the following opinions:
1.) If it does not rain, my array's performance deteriorates due to dirt (dust/guano/dew turning dust to mud/etc.) at the rate of about 1%/week with a lot of variability on that rate depending on atmos. conditions and weather variability such as dust/wind/dew point, etc.
2.) As a 1st approx., rain will, depending on duration and intensity, restore, again - very approx. - about 2/3 to 3/4 of the lost performance due to dirt.
3.) Once thoroughly cleaned with dish soap and a soft brush, and rinsed, any subsequent cleanings will restore about 3/4+ or so of the lost performance due to dirt by simply hosing the array with plain water at the rate of approx. 4l/m^2 of array surface (or about 1.5 gal./panel) and simply allowing the array to air dry. I rinse mostly from top to bottom.
4.) I've done what I believe are reasonably helpful (to me anyway), repeated and hopefully informative experiments that are probably a bit too involved and boring to be described here (details on request) that also lead me to believe that special rinses, squeegeeing, cloth drying, windexing, etc. to get the array squeaky clean and spot free do not produce a measurable and thus significant improvement in restoring performance than the simple hosing and air drying I've described. Seems to me, given the probably small increment of such improvement for all the extra work involved, and considering that most, if not all that extra improvement from the special treatment would probably disappear after a few days of non rain weather anyway, it ain't worth it. Maybe a decent and workable cleaning schedule: Soap/brush/rise 1X/year and hose ~ 1X/month.

Quick bottom line on cleaning methods: Hose rinsing and air dry left some spots, but I couldn't measure a difference in performance between that method and daily cleanings that involved soap, cloth scrubbing, rise, windexing and then polishing. I've confirmed, at least in my own mind what I suspected, and what I've read: That is, up to a point, the human eye is not necessarily a good indicator or estimator of how much a dirt performance penalty might be with respect to how dirty a surface looks.

I also believe that panel cleaning services are oversold and accompanied by a lot of hype and B.S. A few min. with a hose ~ 1X/month isn't worth the price of a commercial clean, at least not to me.

[bcroe]

Dan - I thought I read that you have a geothermal heat pump, I have one as well and my consumption is running the same as yours 70 to 100kwh daily average. Should drop off significantly this summer as we don't use AC often. Doesn't look like the clipping affects you much!

Bruce- 149 kWh peak..nice! wish I could add some more panels but am pretty well maxed out with my inverters.
I'm limited to 20 kw with my utility anyway.

My heat pump typically runs in that range as well. Come a sunny June day you will no doubt beat my best. If you
had a string system, it wouldn't be hard to add more strings; the inverters will limit peak power to the same as before.
The reason to add would be because there are frequently times when output is low; clouds, rain. No reason to orient
extra strings the same as the others, they would just be lost in clipping in good noonday sun. Instead point them at
the rising and setting sun when power is down; they will still work under cloudy dispersed light. That is what happens
here. Bruce Roe

[Truenorth]

JPM - Youve got me thinking about doing some cleaning on my panels as well.....thanks for the sharing research!

Bruce - Thanks for the ideas....I'm going to keep them in mind as I monitor the results of my system.

[J.P.M.]

JPM - Youve got me thinking about doing some cleaning on my panels as well.....thanks for the sharing research!

You're welcome, but I'm not sure my curious pursuits qualify as research. While my findings may be common, other arrays in other locations may and probably will have different fouling patterns and be more/less difficult to clean based on weather, topography, soil and other conditions.

[Eleceng1979]

On a 12.96kw system my records are being broken on a daily basis. My best since June 16th 2016 installation is... 86.4 kwh. Not too bad for central ohio in spring.

https://pvoutput.org/intraday.jsp?id...&gs=0&da=1&m=0

[Truenorth]

With the longer days and more sunshine I hit a new record with 129 kWh a few days ago! Generation is starting before 7AM and continuing almost to 9PM. We have been having some cooler days with a lot of sun providing optimum conditions.

[J.P.M.]

With the longer days and more sunshine I hit a new record with 129 kWh a few days ago! Generation is starting before 7AM and continuing almost to 9PM. We have been having some cooler days with a lot of sun providing optimum conditions.

So what does PVWatts say for a clear day's output this time of year ? Get that # and you can also use it to SWAG the PVWatts system loss parameter provided the temp. profiles for the comparison day(s) are somewhat similar. Still not super accurate, but probably better than the 14 % default vales the model uses.

[Truenorth]

So what does PVWatts say for a clear day's output this time of year ? Get that # and you can also use it to SWAG the PVWatts system loss parameter provided the temp. profiles for the comparison day(s) are somewhat similar. Still not super accurate, but probably better than the 14 % default vales the model uses.

I used an 8% loss factor for my system and come up with 104kwh per day for May (3208kwh monthly). Not sure I have selected all of the correct parameters. I'm assuming Solarworld 285w panel would be 'standard'.

[J.P.M.]

I used an 8% loss factor for my system and come up with 104kwh per day for May (3208kwh monthly). Not sure I have selected all of the correct parameters. I'm assuming Solarworld 285w panel would be 'standard'.

Read the PVWatts help/info screens, particularly the parts that talk about how to use/interpret the results. It's a model that estimates long term performance. Similar to a long term weather forecast, it guarantees nothing. Using daily output, as I suggest, is no more than a dart throw. But doing so and understanding the limits of doing so, can be useful for a "gut" feeling of what a clear day's output might be. Most of solar energy technology is not rocket science and not particularly precise, or, beyond the absolute dictates of safety, needs to be. A lot of approximations along the way, a good part of which is due to the variability of the weather, are part of the way the game is run.

[Truenorth]

Read the PVWatts help/info screens, particularly the parts that talk about how to use/interpret the results. It's a model that estimates long term performance. Similar to a long term weather forecast, it guarantees nothing. Using daily output, as I suggest, is no more than a dart throw. But doing so and understanding the limits of doing so, can be useful for a "gut" feeling of what a clear day's output might be. Most of solar energy technology is not rocket science and not particularly precise, or, beyond the absolute dictates of safety, needs to be. A lot of approximations along the way, a good part of which is due to the variability of the weather, are part of the way the game is run.

So if I check PVWatts at the hourly level for the matching date, it shows 123.7kwh which is close to the 129kwh I received. Nice check thanks!

[J.P.M.]

So if I check PVWatts at the hourly level for the matching date, it shows 123.7kwh which is close to the 129kwh I received. Nice check thanks!

You're welcome. Slightly better than a dart throw, but not too much. Still needs daylong correction for irradiance, ambient temp. and wind. Do it about a dozen times or so on corresponding days, and use the results to SWAG maybe a better guess at the system loss parameter the model uses. No more than another piece of information really, and, I suppose, technically a misuse of the model.