Missed It...........By That Much!

[MrDodge]

Greetings Everyone,

I installed a small ground mount array in Feb. 2018, after patiently waiting 10 months for the winter solstice I was shocked how I barely squeaked by the long shadows of winter. The three pics below are approx. 70 mins. before: solar noon: and 80 mins. after. The pictured roof line is 80 feet from the array.

Funny how as a DIY'er all the accomplishments you've made over the years are overshadowed by the small mistakes you make along the way. Today I barely averted one!

70mins..jpg

Solar Noon.jpg
84mins..jpg

[NCmountainsOffgrid]

I think I 'see' what you mean...... but, don't you want shading so that the panels stay cooler and work 'more' for you? HA!

[SunEagle]

Nice job. Lets hope your home does not increase in size or the array sinks a little. Then you may get some shading.

[J.P.M.]

Given the space/land avail. behind the array, I might have moved it back (north) a few feet, but a miss is almost as good as a mile. Technically, at the current location, you'll lose a smidgen of circumsolar diffuse irradiance on/around the winter solstice at/around solar noon, but as a practical matter, that loss is so small l doubt if anyone would be able to measure it.

Has the array met your output expectations so far ? Anything you'd do different on a redo ? Problems ?

Add: How's your alternate energy knowledge quest/odyssey coming along ?

Happy holidays.

J.P.M.

[MrDodge]

Good Evening J.P.M.,

Unfortunately due to record rainfall this calendar yr. I'm probably gonna end about 500 kwh's short of my projected PV Watts estimate. Annual avg. is 45" per yr., we're at 70" today with more rain in the forecast. On a positive note I haven't cleaned my panels since they were installed.

.You're correct, given another chance I would have moved to the North a few more feet. After install i learned keeping cabling runs as short as possible really only applied to DC runs. Also I would have opted for M210's instead of M190's (used are basically the same price). The reason being around 60 days after install I got this shocker of a day via the Envoy reporting (see pic below). I was thinking Lawd..... Lawd..... Lawd what have I done!

Record Day.jpg

I was fortunate enough to run the numbers in PV Watts before install which assured me at a 1.4 to 1 Dc/Ac ratio only amounted to a $5 annual loss vs. 1.1 to 1.
I was very happy to see the clipping moderate to virtually nonexistent as the daily temperature rose. I don't regret going with used equipment thus far. Electricity rates are so low here (.09 kwh) it just wasn't practical to use new even with the tax credit.

The only problems so far have been CLOUDS......Everywhere!

I'm 2 yrs. from retirement and thinking of my next solar project now. Its gonna be hot water or a panel with a tracker.

Merry Christmas and have a Happy New Year Everyone!

[J.P.M.]

Good Evening J.P.M.,

Unfortunately due to record rainfall this calendar yr. I'm probably gonna end about 500 kwh's short of my projected PV Watts estimate. Annual avg. is 45" per yr., we're at 70" today with more rain in the forecast. On a positive note I haven't cleaned my panels since they were installed.

.You're correct, given another chance I would have moved to the North a few more feet. After install i learned keeping cabling runs as short as possible really only applied to DC runs. Also I would have opted for M210's instead of M190's (used are basically the same price). The reason being around 60 days after install I got this shocker of a day via the Envoy reporting (see pic below). I was thinking Lawd..... Lawd..... Lawd what have I done!



I was fortunate enough to run the numbers in PV Watts before install which assured me at a 1.4 to 1 Dc/Ac ratio only amounted
to a $5 annual loss vs. 1.1 to 1.
I was very happy to see the clipping moderate to virtually nonexistent as the daily temperature rose. I don't regret going with used equipment thus far. Electricity rates are so low here (.09 kwh) it just wasn't practical to use new even with the tax credit.

The only problems so far have been CLOUDS......Everywhere!

I'm 2 yrs. from retirement and thinking of my next solar project now. Its gonna be hot water or a panel with a tracker.

Merry Christmas and have a Happy New Year!

Thank you for the info. Solar thermal is fun but maybe PV and a heat pump water heater is about as efficient and maybe less maint. My solar thermal water heater is about like the love affair I have with steam locomotives - lots of fun and playtime but probably impractical if I needed to replace it. If you do go solar thermal, get a copy of Duffie & Beckman before you do anything.

Clouds are ubiquitous. Climate's what your expect. Weather is what you get. PVWatts modeling pretty much follows climate. If your modeling is fairly representative of what you have, PVWatts has a pretty high probability of getting close to reality over the long haul.

Back 'atcha for holiday greetings and best for the new year.

[MrDodge]

You're Quite Welcome Sir,

Thank you for the literature suggestion. One other tidbit of info, today was another record breaking day @ just under $.08 of production for the day.
Yes, 850 Wh. " Tarrable, just Tarrable" ( Famous Quote of Sir Charles Barkley)

[J.P.M.]

You're Quite Welcome Sir,

Thank you for the literature suggestion. One other tidbit of info, today was another record breaking day @ just under $.08 of production for the day.
Yes, 850 Wh. " Tarrable, just Tarrable" ( Famous Quote of Sir Charles Barkley)

On the paltry production: "Some days you eat the bear, some days the bear eats you". Attributed by some/many sources to Elwin Charles "Preacher" Roe, a major league baseball pitcher. Others place a similar sentiment to Emerson in/around 1870 or so discussing the unpredictability of the ursine diet and/or perhaps the ability/adaptability of the bear's constitution to eat most anything to survive.

Variations of the phrase are used a lot by various folks as analogies to the uncertainties of life.

"Climate is what on average we may expect, weather is what we actually get " - Andrew John Herbertson, Oxford university, circa 1901.



FWIW, Worst production day I've had was 1.11 kWh/day on 02/27/2017 a day of soaking rain. I make more use of my array's running 31 day average daily output. Over 5+ years, the 31 day running average daily output has been 24.97 kWh/day after deduction for ~ 3.5 % for late afternoon shade. Minimum ave. 31 day output for the period is 12.09 kWh/day. Maximum ave. 31 day output is 33.45 kWh/day. Population std. dev. is 4.98 kWh/day. Array size, 5.232 kW, azimuth 195.75 deg. Tilt, 19.75 deg. Roof mount. Zip: 92026.

[bcroe]

My worst was 4 KWH, during a 2 day blizzard. Can usually do 35 in the rain, heavy overcast maybe half that.
Bruce Roe

[littleharbor]

On the paltry production: "Some days you eat the bear, some days the bear eats you".

From lyrics of a song written by a friend.
"Some days, chicken, some days chicken s**t"

[MrDodge]

J.P.M.

Thanks so much for sharing you're performance/size data. If my math is correct our daily record low is eerily similar (within 7 watts)

Unfortunately I got smoked on monthly high. My single day record high match's the production you achieved for 31 days straight! (if my math is correct)

Array 3.975 kw, Azimuth around 176-77 deg. Tilt 30 deg. fixed G. Mount, 40330

[J.P.M.]

J.P.M.

Thanks so much for sharing you're performance/size data. If my math is correct our daily record low is eerily similar (within 7 watts)

Unfortunately I got smoked on monthly high. My single day record high match's the production you achieved for 31 days straight! (if my math is correct)

Array 3.975 kw, Azimuth around 176-77 deg. Tilt 30 deg. fixed G. Mount, 40330

My 31 day numbers may take a bit of explaining. Since startup, I've recorded daily output as well as a bunch of other stuff. Each day, I calc. and record the average of the prior 31 days. The highest number of all those 31 day periods was for the period centered around 06/14/2014. The total generation for those 31 days was 1,036.95 kWh --->>> 1,036.95/31 = 33.45 kWh/day. The min. gen. for any 31 day period was centered around 01/05/2017. The total generation for that period was 374.78 kWh --->>> 374.78/31 = 12.09 kWh/day average.

The mean of all those 31 day averages is 24.97 kWh/day (n = 1,863). the population std. dev. is 4.98.

The highest single day generation I've had since the 10/17/2013 array startup was 35.47kWh or 35.47 kWh/day per 5.232 STC kW = 6.78 kWh/day per STC kW.

FWIW, all that generation per STC kW is about the same as what I monitor from around my HOA's arrays corrected for orientation, and also pretty close to what PVOutput. org for the most part shows for arrays near me, again corrected for orientation, most of which are not Sunpower as my stuff is. I don't know how much more data I need to convince myself or any other objective person looking at the same data that Sunpower stuff is good, but no better than other stuff - just way overpriced for what you get.