Our solar production

[JasonA]

And to answer, ours is a split system as seen on my thread.. so my highest efficiency comes close to mid-day/slight afternoon. After that, the back garage side is handling the bulk and the front array is plummeting down fast.. I have alot of trees on the back side of the garage that I'm always having to trim to keep clear and I haven't done it in the last 6 months.

We are going doing a bulk order with some other Leafers/locals on here and getting a large order of panels. we're planning on an additional 3kwh within the next month. just have to order the m215's, racking, etc

As for the public site, I had it up for awhile.. then took it down because Enphase, RGS and SolarWorld were sending TONS of people out to the house or referring them to our system.. and then it's not hard to see on the location where we are located and people were stopping by asking, etc. So I took it off

 

[dgpcolorado]

In the "be careful what you wish for" category, two days ago the ground here was bare. This morning it was not:

Needless to say, my solar output has been quite poor the last two days. I spent five and a half hours shoveling today and still have a couple more hours to go to get my long driveway clear (I'm taking a break).

 

[NeilBlanchard]

You need a roof rake and slide! I have a MinnSnowta, that would make relatively quick work of that snow.

 

[RegGuheert]

The microinverters in our PV array recorded the coldest temperatures since they were installed this morning: -20C (-4F). This is about 5F colder than any previous temperature they have seen (since January 2011). It's not surprising since we have shattered the lowest recorded cold temperature for February 24 today by over 15F.

(In case anyone recalls that I reported some -4F temperatures from my inverters last winter, I have since decided that the M190s are not accurate for measuring temperatures that cold. The M215s which I installed in 2014 (and the new-style M190) seem to track other temperature measurements much better. By way of comparison, the old M190s reported -23C (-9.4F) this morning, which is about 5F lower than any previous report.)

 

[dgpcolorado]

You need a roof rake and slide! I have a MinnSnowta, that would make relatively quick work of that snow.

I use (and highly recommend) a Phillps Snow Cutter for the roof. But for my panels I use a window squeegee on a long painter's pole. Works well and doesn't damage the glass.

When my panels are at a fall/winter pitch of 55º or 45º (the current angle) the snow comes off easily. But at a pitch of 35º or 25º it is more of a nuisance because the bottom edges are so high and gravity doesn't help as much. I am fortunate that we don't get much snow when the panels are at the summer solstice pitch of 15º, although it does happen on occasion here in the mountains.

 

[RegGuheert]

You need a roof rake and slide! I have a MinnSnowta, that would make relatively quick work of that snow.

I use (and highly recommend) a Phillps Snow Cutter for the roof.

That's very cool! At the time I purchased our Roof Rake, which was during Snowmageddon, I could have used something like that. But since that time, we have never had multiple feet of snow on our roof.

But for my panels I use a window squeegee on a long painter's pole. Works well and doesn't damage the glass.

Yes, one concern I have about the roof rake is that the corners are aluminum and have the potential to damage the glass, particularly when I am using several extensions.

When my panels are at a fall/winter pitch of 55º or 45º (the current angle) the snow comes off easily.

With the 60º pitch we use in the wintertime, I never have to clear the snow. We typically get a day warm enough to make the snow shed. Your temperatures are certainly more consistently cold. (And your skiing conditions are also far superior!)

But at a pitch of 35º or 25º it is more of a nuisance because the bottom edges are so high and gravity doesn't help as much.

Our roof has a 30º pitch and it only sheds under certain circumstances. The roof rake helps, but you do need long, heavy extensions with such a low elevation angle. I can clear the garage roof successfully, but I have much more limited success with the roof over the house. I don't think a roof rake of any sort would work with the two-story portion of our house; I think I would need to climb up there if I ever needed to clear it. Frankly, I don't like to do that even when it is warm and dry.

I am fortunate that we don't get much snow when the panels are at the summer solstice pitch of 15º, although it does happen on occasion here in the mountains.

I use the same angle in the field array during the summertime. No snow so far at that angle!

BTW, what angle do you use in the spring and fall? I am starting to realize that I am leaving a bit on the table by only moving the field array twice a year. Simply put, that array seems to harvest roughly the same amount of energy as the fixed, 30º array on the roof even though it gets moved.

 

[dgpcolorado]

...BTW, what angle do you use in the spring and fall? I am starting to realize that I am leaving a bit on the table by only moving the field array twice a year. Simply put, that array seems to harvest roughly the same amount of energy as the fixed, 30º array on the roof even though it gets moved.

I wrote a spreadsheet that calculated and plotted the angle of the sun at solar noon for each day of the year, based on latitude. I then chose pitch angles that I hoped would catch the heart of the day. I used to use 65º at winter solstice (makes pulling snow off really easy) but decided 55º would capture more sun at my latitude of about 38º. After occasional tweaking over the years I've settled on:

Panel angle for 38.19º North latitude

15º 26 April to 18 August
25º 19 August to 17 September
35º 18 September to 10 October
45º 11 October to 9 November
55º 10 November to 3 February
45º 4 February to 3 March
35º 4 March to 27 March
25º 28 March to 25 April

As you know, the sun angle changes rapidly around the equinoxes and slowly around the solstices.

 

[GRA]

...BTW, what angle do you use in the spring and fall? I am starting to realize that I am leaving a bit on the table by only moving the field array twice a year. Simply put, that array seems to harvest roughly the same amount of energy as the fixed, 30º array on the roof even though it gets moved.

I wrote a spreadsheet that calculated and plotted the angle of the sun at solar noon for each day of the year, based on latitude. I then chose pitch angles that I hoped would catch the heart of the day. I used to use 65º at winter solstice (makes pulling snow off really easy) but decided 55º would capture more sun at my latitude of about 38º. After occasional tweaking over the years I've settled on:

Panel angle for 38.19º North latitude

15º 26 April to 18 August
25º 19 August to 17 September
35º 18 September to 10 October
45º 11 October to 9 November
55º 10 November to 3 February
45º 4 February to 3 March
35º 4 March to 27 March
25º 28 March to 25 April

As you know, the sun angle changes rapidly around the equinoxes and slowly around the solstices.

Does your rack not let you set your panels at even numbered tilts (i.e. 20 or 60 degrees?). A winter tilt of 60 deg. would probably be the ideal for you - what you'd lose in February due to angle you'd probably gain back due to reflection from snow cover. I designed an off-grid winter-spring only system at 8500 feet with 60 degree fixed tilt (Lat. 37.63 deg. 90-lat = 52.37 deg. - 23.44 deg. on the solstice = 28.93 deg. solar noon elevation angle @ solstice), as the critical design case was for the winter solstice through February, and spring sun provided excess output at any tilt.

For RegGuheert, adjusting tilt four times a year is enough for most people, although if you're trying to collect every Wh you can and changing the angle isn't a big deal, you can adjust 6 times or more like dgpcolorado does. The loss is so small for most people that it probably isn't worth it for roof arrays, although my off-grid customers generally tried to minimize their costs by going small on the array and batteries and not letting any sun slip by. But, like dgpcolorado, they normally used ground or pole mounts that didn't require rooftop acrobatics to adjust.

 

[RegGuheert]

For RegGuheert, adjusting tilt four times a year is enough for most people, although if you're trying to collect every Wh you can and changing the angle isn't a big deal, you can adjust 6 times or more like dgpcolorado does. The loss is so small for most people that it probably isn't worth it for roof arrays, although my off-grid customers generally tried to minimize their costs by going small on the array and batteries and not letting any sun slip by. But, like dgpcolorado, they normally used ground or pole mounts that didn't require rooftop acrobatics to adjust.

The field array is a ground mount. It was made adjustable because it was originally used off-grid and wintertime production was the most important characteristic. But with it now on-grid, I am finding that while two adjustments per year gives better performance around the winter and summer solstices, the year-round production is not improved.

BTW, this is a bit of a surprise, since PVWATTS indicated there would be a bit of an improvement. But what I am finding is that the while the older PV modules produce the same peak power as the newer modules, they do not produce as much electricity in the diffuse light that results from cloudy weather. For example, while the field inverters produced about 10% more electricity during sunny January, they produced only about 2.5% more during cloudy December.

I probably should fabricate the props needed for a ~30º elevation and use that for spring and fall. I'm just not sure I want to change it that often. While it is not "a big deal," it is also not a small deal and takes 30-45 minutes to complete.

 

[dgpcolorado]

Does your rack not let you set your panels at even numbered tilts (i.e. 20 or 60 degrees?)...

My racks are limited to 15º, 25º, 35º, 45º, 55º, 65º. I find that having the winter pitch at 55º helps because I get the bottom of the panels up a bit and they get less shading in the mornings and afternoons. As you know, once a string array gets partly shaded production crashes.

Changing the pitch of the small array is easy but the big array is pretty heavy to move and hold by myself, especially when I am lifting it to higher angles. I also wish I had that one installed in "portrait" orientation versus "landscape", like the small array, because it would make it easier to pull the snow off.

Overall, changing the pitch is pretty easy and it takes me about ten minutes with a step ladder for both.

 

[GRA]

Does your rack not let you set your panels at even numbered tilts (i.e. 20 or 60 degrees?)...

My racks are limited to 15º, 25º, 35º, 45º, 55º, 65º. I find that having the winter pitch at 55º helps because I get the bottom of the panels up a bit and they get less shading in the mornings and afternoons. As you know, once a string array gets partly shaded production crashes.

Figured that might be the case, as I knew of pole mounts that were restricted to those angles.

Changing the pitch of the small array is easy but the big array is pretty heavy to move and hold by myself, especially when I am lifting it to higher angles. I also wish I had that one installed in "portrait" orientation versus "landscape", like the small array, because it would make it easier to pull the snow off.

Overall, changing the pitch is pretty easy and it takes me about ten minutes with a step ladder for both.

Yeah, portrait is definitely the way to go in snow country if you've got more than one row of modules. A single row works okay, though. Here's one sort of in your neck of the woods:

http://www.jasonoutdoors.com/bettybear2001/bigimage/P9220194BettyBear.jpg" onclick="window.open(this.href);return false;

http://www.denverdavis.com/photos/2010/2010.03.13_BettyBearHut/lowres/BettyBear-040.jpg" onclick="window.open(this.href);return false;

[Note: I helped install this system, but didn't design it - it was part of a hands-on seminar on issues that crop up in way off-grid installations. As I had done a preliminary design for a system for a backcountry hut in California, I wanted to check out some of my ideas and see what other people were doing before going ahead. All in all, I felt many of the design decisions made here were poorly suited for the situation I was designing for, and the detail execution left a lot to be desired, but negative info is often even more valuable than positive info. I got a lot of info on what not to do.]

 

[GRA]

For RegGuheert, adjusting tilt four times a year is enough for most people, although if you're trying to collect every Wh you can and changing the angle isn't a big deal, you can adjust 6 times or more like dgpcolorado does. The loss is so small for most people that it probably isn't worth it for roof arrays, although my off-grid customers generally tried to minimize their costs by going small on the array and batteries and not letting any sun slip by. But, like dgpcolorado, they normally used ground or pole mounts that didn't require rooftop acrobatics to adjust.

The field array is a ground mount. It was made adjustable because it was originally used off-grid and wintertime production was the most important characteristic. But with it now on-grid, I am finding that while two adjustments per year gives better performance around the winter and summer solstices, the year-round production is not improved.

BTW, this is a bit of a surprise, since PVWATTS indicated there would be a bit of an improvement. But what I am finding is that the while the older PV modules produce the same peak power as the newer modules, they do not produce as much electricity in the diffuse light that results from cloudy weather. For example, while the field inverters produced about 10% more electricity during sunny January, they produced only about 2.5% more during cloudy December.

I probably should fabricate the props needed for a ~30º elevation and use that for spring and fall. I'm just not sure I want to change it that often. While it is not "a big deal," it is also not a small deal and takes 30-45 minutes to complete.

Reg, one possible reason for the difference: by any chance does the field array use monocrystalline cells, and your other array polycrystalline? IIRC, the latter are better in diffuse light and at high aspect angles, while the monocrystalline are better in strong, normal aspect sun. The difference is generally pretty small, and we didn't have the kind of individual module monitoring that is common now so it wouldn't be apparent to users in any case (assuming all the modules fed a single controller), but you might well notice it with your instrumentation.

 

[RegGuheert]

Reg, one possible reason for the difference: by any chance does the field array use monocrystalline cells, and your other array polycrystalline? IIRC, the latter are better in diffuse light and at high aspect angles, while the monocrystalline are better in strong, normal aspect sun. The difference is generally pretty small, and we didn't have the kind of individual module monitoring that is common now so it wouldn't be apparent to users in any case (assuming all the modules fed a single controller), but you might well notice it with your instrumentation.

Good thought! In fact it is the other way around. The field array is polycrystalline and the roof array is monocrystalline.

There are plenty of other differences, as well, but I still think the differences in production *should* be highest in December when the pointing benefit of the field array is the largest. But it seems consistent: When there is a string of cloudy weather, the roof array produces more electricity.

 

[GRA]

Reg, one possible reason for the difference: by any chance does the field array use monocrystalline cells, and your other array polycrystalline? IIRC, the latter are better in diffuse light and at high aspect angles, while the monocrystalline are better in strong, normal aspect sun. The difference is generally pretty small, and we didn't have the kind of individual module monitoring that is common now so it wouldn't be apparent to users in any case (assuming all the modules fed a single controller), but you might well notice it with your instrumentation.

Good thought! In fact it is the other way around. The field array is polycrystalline and the roof array is monocrystalline.

There are plenty of other differences, as well, but I still think the differences in production *should* be highest in December when the pointing benefit of the field array is the largest. But it seems consistent: When there is a string of cloudy weather, the roof array produces more electricity.

Ah, well, I was hoping it was something simple and obvious, and that's clearly not the case. Edit: Or maybe it's just my memory that's at fault, as this site http://energyinformative.org/best-solar-panel-monocrystalline-polycrystalline-thin-film/" onclick="window.open(this.href);return false; says that monocrystalline "Tend to perform better than similarly rated polycrystalline solar panels at low-light conditions." I remember it the other way around, at least for high-aspect angles. And then you get into issues such as the quality of the anti-reflective coatings used, scratching on the glass covering causing more reflections etc. etc.

 

[RegGuheert]

Ah, well, I was hoping it was something simple and obvious, and that's clearly not the case. Edit: Or maybe it's just my memory that's at fault, as this site http://energyinformative.org/best-solar-panel-monocrystalline-polycrystalline-thin-film/" onclick="window.open(this.href);return false; says that monocrystalline "Tend to perform better than similarly rated polycrystalline solar panels at low-light conditions." I remember it the other way around, at least for high-aspect angles. And then you get into issues such as the quality of the anti-reflective coatings used, scratching on the glass covering causing more reflections etc. etc.

That seems to fit what I am seeing. At the end of the day, it does seem that the pointing benefits that the field array *should* have over the course of the year are completely offset by their poor production in low light levels.

But I must say that I am pretty happy with the production of both of the arrays!

 

[DaveEV]

There are plenty of other differences, as well, but I still think the differences in production *should* be highest in December when the pointing benefit of the field array is the largest. But it seems consistent: When there is a string of cloudy weather, the roof array produces more electricity.

The field array is tilted at a steeper angle? I believe that flatter arrays (to a point) will generally outperform highly angled arrays in cloudy conditions. So you may want to drop the tilt angle of your field array when it's most likely to be cloudy if it's adjustable.

 

[RegGuheert]

The field array is tilted at a steeper angle?

It is steeper during fall and winter and shallower during spring and summer. More specifically, the roof array is fixed at a 7/12 pitch, which is an elevation angle of about 30º. The field array is at about 60º elevation in fall and winter and at about 15º elevation angle in spring and summer.

I believe that flatter arrays (to a point) will generally outperform highly angled arrays in cloudy conditions. So you may want to drop the tilt angle of your field array when it's most likely to be cloudy if it's adjustable.

Interesting! I did not know that! I will have to see how things compare this summer during cloudy weather.

 

[dgpcolorado]

Yeah, portrait is definitely the way to go in snow country if you've got more than one row of modules. A single row works okay, though...

The other difference in snow removal for my arrays is that the small (older) one has a shiny glass surface and the big (newer) one has a frosted glass surface. The snow doesn't slide off the new one as well as the old one.

 

[RegGuheert]

After a lousy December and a so-so January, February 2015 turned out to be pretty good, breaking the all-time February production record from 2012 by over 25%.

February 2015 saw three new all-time record production days due to the additional generation in place and the record cold weather:

February 15: 81.912 kWh
February 20: 82.000 kWh
February 27: 82.400 kWh

This new one-day record breaks the old February record (set exactly one year before) of 62.945 kWh by 31%. That's impressive since the the DC generation capability has only increased by 29%. But in the very cold weather, the inverters limit for much of the day, so this time of year the increase is also affected by the increase in AC rating, which was over 32%.

There was some cloudiness on February 27 when this record was set, so I expect to eventually see around 85 kWh in a single day. (I can't touch QueenBee's 94.7 kWh record on May 30, 2014!) Traditionally, all-time one-day production records were set in late March and early April or late May. Since the new part of the array has its worst pointing angle around that time, I predict early-to-mid March or early June will be when records are set with the new overall array. Time will tell.

While record-cold weather may be good for PV production, it is NOT good for the overall electricity budget. Eking out a few more kWh is nothing compared with the extra MWhs required to heat the house with electricity when the temperatures are close to 0° F

Below are all our numbers for 2011, 2012, 2013, 2014 and 2015 along with the PVWatts predictions for the old array (PVW42: good through June 2014) and the new array (PVW54: good starting with July 2014):

Month    PVW42   2011   2012   2013   2014   2015  PVW54  Units
---------------------------------------------------------------
January    916    669    869    822    857   1006   1229   kWh
February   702    158   1085    866   1054    1361   915   kWh
March      965      0   1350   1152   1113          1240   kWh
April     1465      0   1465   1495   1338          1899   kWh
May       1583      0   1477   1491   1457          2074   kWh 
June      1268      0   1478   1368   1521          1666   kWh
July      1448    595   1395   1406   1880          1902   kWh
August    1442   1347   1447   1333   1794          1875   kWh
September 1209    910   1295   1414   1577          1555   kWh
October   1304    931    981   1034   1258          1713   kWh
November   864    949   1041   1018   1227          1154   kWh
December   820    803    612    669    812          1108   kWh
---------------------------------------------------------------
Totals   13986   6362  14495  14068  15888   2367  18330   kWh

Since installation, our system has produced 53.180 MWh as of the end of February 2015.

 

[SilverLeaf]

Production from my 33 230wDC SunPower Panels via Sunnyboy (SMA) 7000US Inverter (7.59kW DC)

2015 AC Production
Jan 863
Feb 1060

2014 AC Production
Jan 1048
Feb 977
Mar 1347
Apr 1438
May 1476
Jun 1413
Jul 1346
Aug 1368
Sep 1242
Oct 1193
Nov 1053
Dec 844

2013 AC Production
Jan 910
Feb 1105
Mar 1328
Apr 1444
May 1474
Jun 1447
Jul 1284
Aug 1230
Sep 1280
Oct 1050
Nov 955
Dec 1005

2012 AC Production
Mar 1228
Apr 1217
May 1416
Jun 1325
Jul 1189
Aug 1168
Sep 1118
Oct 603
Nov 970
Dec 851

Link to my Solar Production - http://pvpwrev.webs.com/" onclick="window.open(this.href);return false;