LADWP Frustration

[J.P.M.]

My tap water is as hard as a rock.................................... Washing with mild soap/soft cloth and rinsing with tap (hose) water/soft cloth and squeegeeing the excess water, OR, mild soap/soft cloth and D.I. rinse/squeegeing makes no difference one over the other in output improvement the I can measure................................. Nor can I measure a difference by measurement between washing and not squeegeeing - letting the water evap. w/ water spots, and washing and then carefully squeegeing to remove most/all water spots. The array looks cleaner w/ D.I. rinse and squeegeing, but I can't MEASURE a difference in output when comparing the difference in performance between improvement after tap water and regular water rinse.............................. Beauty is in the eye, but the eye may be a poor indicator of transmission of solar radiation through a surface that may be soiled to the eye but clean enough to not be able to measure a difference in performance....................................... For my array, dirt decreases output by VERY ROUGHLY something like about 1% /week if it doesn't rain, and depending on other things like how dry/dusty/foggy/dew /weather affects come into play. A moderate to decent rain washes off about 2/3 of the accumulated dirt since the last rain or last washing. Some day, once I get through measuring array fouling, if it doesn't rain, I'll hose off the array in the early A.M. every 3 - 4 weeks and accept a nominal 3% performance penalty due to array fouling,

[SunEagle]

My tap water is as hard as a rock.................................... Washing with mild soap/soft cloth and rinsing with tap (hose) water/soft cloth and squeegeeing the excess water, OR, mild soap/soft cloth and D.I. rinse/squeegeing makes no difference one over the other in output improvement the I can measure................................. Nor can I measure a difference by measurement between washing and not squeegeeing - letting the water evap. w/ water spots, and washing and then carefully squeegeing to remove most/all water spots. The array looks cleaner w/ D.I. rinse and squeegeing, but I can't MEASURE a difference in output when comparing the difference in performance between improvement after tap water and regular water rinse.............................. Beauty is in the eye, but the eye may be a poor indicator of transmission of solar radiation through a surface that may be soiled to the eye but clean enough to not be able to measure a difference in performance....................................... For my array, dirt decreases output by VERY ROUGHLY something like about 1% /week if it doesn't rain, and depending on other things like how dry/dusty/foggy/dew /weather affects come into play. A moderate to decent rain washes off about 2/3 of the accumulated dirt since the last rain or last washing. Some day, once I get through measuring array fouling, if it doesn't rain, I'll hose off the array in the early A.M. every 3 - 4 weeks and accept a nominal 3% performance penalty due to array fouling,

Hopefully none of those fires up North occur near you. The smoke in some areas is very thick which I presume cuts pv production a lot more than just some dirt.

[J.P.M.]

Hopefully none of those fires up North occur near you. The smoke in some areas is very thick which I presume cuts pv production a lot more than just some dirt.

Funny you should mention it. To your comment about smoke perhaps affecting production: So far no recent larger type fires last 1 -2 weeks around here except one at Camp Pendleton last week, 08/12 - 08/13 that we could smell for about 24 hrs. or so and caused some visible haze. The prior 4 array fouling measurement estimates I took from 08/09 to 08/12 with 1 cloudy day of no measurements showed fouling to be about 2+% or so. The readings for the 3 days following the smoke event showed the array fouling to be something of the order of 3% or so. Those fouling estimates themselves seem to fit reasonably well with the long term trend I seem to notice that my array performance seems to drop about 1%/week in the absence of rain, and bounces around a bit with fog/dew/dust/etc.................................. I think I can measure array fouling VERY roughly, and with a bit of luck, to no better than about +/- 0.75% or so. I try to be consistent in my data taking methods, and rely on consecutive measurements to MAYBE spot trends........................................... Attempting to take measurements on things like solar irradiance, amb. air temp., and primarily individual panel temp. while the wind vector which is constantly shifting and galloping around, and also while all that and more are also interacting with one another can make precision a challenge, even with what may be decent but still 2d level instruments.....................................Pe rhaps by luck, the immediate surrounding readings to the smoke/haze event seems to be somewhat consistent and showed something of a knee at the smoke event.......................................... Solar technology is not as exact an enterprise as some think, and measuring array fouling is even less exact, partly because of the # of variables involved coupled with the reality that they won't cooperate and stay still, but sometimes offering a peek at what's going on or maybe a bit more than a peek for those nutty enough to design an array that allows movement under it to measure temps., etc. Lots of fun.

[Mike90250]

Hopefully none of those fires up North occur near you. The smoke in some areas is very thick which I presume cuts pv production a lot more than just some dirt.

Right near me ! So many fires, even where I am, 100 miles from the closest ones, the smoke has covered the whole northern third of the state. I'm struggling to get to float every day, normally be full by noon, and get 300 minutes of float. We have about 1/2 mi visibility, and then the road fades out like a foggy morning. But in 2 days, we are supposed to get a wind shift and it will cool below 95°F and we may get ocean breeze to cool off.

[SunEagle]

Hopefully someone will get those fires out soon.