Sun hours

[J.P.M.]

In addition since I'm running the system at its maximum with hours of clipping on very hot days I am very concerned with temps in the inverters and all electrical connections. I am particularly concerned about the molded case breakers since they can run very hot for extended periods. This advice from Schneider Electric provides guidance from the UL489 standard........

https://www.se.com/us/en/faqs/FA173839/

I monitor the heat at appropriate places throughout my system. I've replaced a few breakers that ran hot just as a prophylactic. A little prevention goes a long way especially if you're running on the high end. I also use silver conductive grease on all connections and terminations where appropriate and always used a torque screwdriver or wrench as appropriate. Never had a failure....knock on wood.

For heat in the inverters, if not so equipped forcing ventilation via fans can knock out ~ 1/3 of the temp. diff amb. to heat sink temps.

for connections, etc. running a heat balance may help identify way to keep things cooler. One common way to get rid of excess heat, especially in confined spaces is with increased ventilation or rearrangement of equipment locations.

[J.P.M.]

Furthermore I built my Shoulder array "East-West orientation" based on information from this Fronius white paper.........

https://www.energymatters.com.au/ima...olar-paper.pdf

I have been very happy with the results.

I'm not really impressed with that paper. Seems there's nothing new in it and it also seems a bit slippery with statements. An example from the abstract: An unsubstantiated statement : " from the perspective of grid operators, east-west oriented grid systems are preferable to south oriented ones, as the energy is fed in more evenly throughout the day." That greater temporal distribution may be somewhat of an advantage, but it almost always comes at the price of decreased day long total output (The area under the south facing curve will be greater than the split array curve for the same total installed STC wattage). That statement, to me anyway, is written to help readers infer that greater temporal distribution is the only consideration, and I kind of doubt that's the case.
Moreover, that statement seems to be at some odds with the second sentence of the abstract which states: "Although south oriented systems are better, east-west oriented systems can also generate substantial savings.

To the first point of flatter temporal distribution, I'd suggest that the statement may apply more to large non residential power plants and less to residential roof top PV systems with access to NEM agreements.
And, if in reference to residential systems, if residential T.O.U. is in force with rates favoring off south orientations, for most common T.O.U. rates/times, there is usually one single orientation that maximizes annual array production or annual array revenue. They may be the same orientation but will probably be different if T.O.U. rates are applicable. In either case, it's one orientation.
With respect to the amorphous panels' orientation of the paper's tested arrays, besides being somewhat confusing in the way it's presented, the array slopes are rather low with the crystalline modules were tilted at 15 deg. If the alleged point of the paper is to show that off south orientations aren't too bad after all, a low slope east or west azimuth orientation is a good way to B.S. the point.
Reason: A vertical orientation will show the greatest variation in output as f(azimuth) of any tilt. A horizontal (zero deg.) slope will show the least (that is, none.) The less the slope, the less the azimuthal variation. Result: A 15 deg. east or west slope will show relatively little variation to a south facing slope due to its low tilt. Result: It looks like aa east or west azimuth array can be almost as good as a south facing array. The results at a higher slope will be less favorable.

There's lots more about that paper that seems less than academically honest to me , but this is a limited venue. IMO only, the paper looks like it comes from an inverter manufacturer and it's a masqueraded pitch to sell more and larger inverters.

[bcroe]

Thank you for your response.

I wholeheartedly and very strongly agree with your 1st opinion with respect to modeling. Before my last post I was wishing I had the particulars about your arrays/system so I could do some modeling comparisons.

To that end, before I go any further into discussing the rest of your above post, if you post all the relevant input PVWatts requires including inverter AC size pertinent to your arrays, I'll run the PVWatts analysis and compare it to a run of a south facing array at 42 deg. tilt and sized so that PVWatts produces the same output with the same inverters and total inverter size for both systems. Please include the azimuths and also seasonal tilt angles and the approx. dates of tilt changes. I'll keep the single orientation array that's compared to yours at 42 deg. tilt.

I'll even go you one better. Give me module maker, model/size and approx. date when they entered service, and inverter model(s) for SAM. I'll use the same data for both systems for the SAM input.

To the extent we agree to trust models' output, we all might learn something.

If you want actual equipment here, it is a lot of numbers. Or maybe just putting down a more idealized
version would work. My installer was none too careful about what was South, the west end of the S lot
line is 36 feet farther south than the east end. It was 2 years before the trash was cleaned up, I found
the stakes, and marked out the area in 100 foot squares. So only the 2018 construct is precise, but the
other facing and elevation angles can be measured out. All my E-W facing panels are mounted on a
10% grade, one end being nearly 7 feet higher than the other. I believe that is irrelevant, long as the
elevation angle is measured on a true vertical angle.

There are at least 4 different brands of panels, either 250W 60 cell or 275W 72 cell. All that could be
tracked down, along with time in service. Inverters are a pair of Fronius IG Plus 7.5KW running since
May 2013, increased loading in Nov 2013 and again in Mar 2018. Much of the current setup is slated
to be upgraded, if the foundation gets dug.

With good weather for a couple days, I will probably be working all out on the 225 foot trench, maybe
can pick up the missing numbers in unfavorable weather. If you stop by, I have extra shovels. The
trencher is working, but tough going here with all the rocks. Bruce Roe

[J.P.M.]

If you want actual equipment here, it is a lot of numbers. Or maybe just putting down a more idealized
version would work. My installer was none too careful about what was South, the west end of the S lot
line is 36 feet farther south than the east end. It was 2 years before the trash was cleaned up, I found
the stakes, and marked out the area in 100 foot squares. So only the 2018 construct is precise, but the
other facing and elevation angles can be measured out. All my E-W facing panels are mounted on a
10% grade, one end being nearly 7 feet higher than the other. I believe that is irrelevant, long as the
elevation angle is measured on a true vertical angle.

There are at least 4 different brands of panels, either 250W 60 cell or 275W 72 cell. All that could be
tracked down, along with time in service. Inverters are a pair of Fronius IG Plus 7.5KW running since
May 2013, increased loading in Nov 2013 and again in Mar 2018. Much of the current setup is slated
to be upgraded, if the foundation gets dug.

With good weather for a couple days, I will probably be working all out on the 225 foot trench, maybe
can pick up the missing numbers in unfavorable weather. If you stop by, I have extra shovels. The
trencher is working, but tough going here with all the rocks. Bruce Roe

Bruce:

To your statement: "To compare two designs, they both should be simulated the same way, such as by PVWatts. Comparing a theoretical system simulation to an actual systems performance is not apples to apples.", I'd like to compare apple to apples in terms of inputs to the greatest extent possible. Any help you could graciously provide would be appreciated.

When modeling an existing system to a given set of inputs (a process that's very similar to something called "rating" an existing boiler or other heat exchanger for different service in the power generation business I came from), using inputs that reflect reality with respect to the existing equipment as much as possible improves the probability that the model will reflect what an existing system will do.

For residential PV systems, simulated weather and irradiance conditions for the site will be the same for any modeled system.

Modeling is not an exact science and probably doesn't need to be. However, the more and better information on the existing system I have, the higher the probability will be that the model will produce numbers that reflect reality.

As for array azimuths, a google shot of the property is probably close enough. I suppose I could find one by rooting around in your zip code but you could save me the trouble.
for the rest of it, PVWatts will only need array sizes and the inverter sizes an array feeds, and array tilts. I'll also need approx. times of the year when you change tilts. The rest of the particulars I listed would be used for the SAM input.

Because you use 15 kW of inverters, I intend to use the same 15 kW in any modeling of a south facing array. I expect that will under-invert any south facing array that is modeled and sized to produce your stated annual output.

As for shading, I believe you once provided a graph that showed approx. times of shade. Any further information you might provide on shading with respect to dime of day/time of year would be helpful.

As for stopping by, without a baseball season, I don't plan on being in the Midwest anytime soon for my 1X/yr. pilgrimage to the friendly confines of Wrigley Field. But if I was, my offer was semi-serious. Having mostly Irish genes, and what's not Irish is Scot, kind of analogous to what male dogs usually do to fire hydrants, I'm sort of genetically predisposed to digging holes if there's dirt and a shovel nearby.

[bcroe]

Hey design reviews are good and educational. I had a career of them with reviewers a lot tougher
than you guys. He whose design is being reviewed needs to see it as an oportunity to improve, it
certainly helped me.

Here is a Goog.. Ear.. today of the array, on the left 6KW pretty much facing E elevation about 82
degrees, operational Mar 2018. At the top 18KW sort of south maybe you can get the orientation,
May 2013, need to check elevation. In the middle 5.5KW facing sort of E, also 5.5KW facing sort
of W, elevation of 74 deg from flat Nov 2013.

There is a plan to revise everything to the newest design, hopefully before the treated wood 2
faced rots. Bruce Roe.


GearthJun20.jpg

[Ampster]

Thanks for demonstrating that outside the box solutions can work and accomplish the owners goals.

[bcroe]

Thanks for demonstrating that outside the box solutions can work and accomplish the owners goals.

Sure, you now have enough info to identify a lot of my earlier mistakes. Bruce Roe

[J.P.M.]

Hey design reviews are good and educational. I had a career of them with reviewers a lot tougher
than you guys. He whose design is being reviewed needs to see it as an oportunity to improve, it
certainly helped me.

Here is a Goog.. Ear.. today of the array, on the left 6KW pretty much facing E elevation about 82
degrees, operational Mar 2018. At the top 18KW sort of south maybe you can get the orientation,
May 2013, need to check elevation. In the middle 5.5KW facing sort of E, also 5.5KW facing sort
of W, elevation of 74 deg from flat Nov 2013.

There is a plan to revise everything to the newest design, hopefully before the treated wood 2
faced rots. Bruce Roe.


GearthJun20.jpg

Bruce: Thank you for the response and consideration. I'll be chewing on that for awhile.
As the used to say on the idiot box, "Updates as they become available. Film with the 10 o'clock news."

Regards,

[J.P.M.]

Bruce: If/When you get the time, on average , +/-, about when do you adjust the tilts on the arrays ? Also, what are the tilt angles ?

Thank You.

[bcroe]

Bruce: If/When you get the time, on average , +/-, about when do you adjust the tilts on the arrays ? Also, what are the tilt angles ?

Thank You.

J. P. M., The only panels I can adjust tilt are the 2018 construct, seen about page 21 of this thread
late March 2018. Take out 6 ground level bolts (on a not windy day), crank the tilt (90 degree range),
put the 6 bolts back in. The plan is to convert all the earlier attempts to this design. Except if I had
known how well it would work, even this first construct would have been 2 sided (design in progress).
Also there follows cable trenching operations.

Tilt change time would be in anticipation of the first snow, and at conclusion of significant snow. This
would be more important for the S array (if it gets built), which have much more potential for improved
energy collection and snow rejection. Current angle (to be measured) is about right for summer,
terrible for winter. If this all follows through, it should be more efficient and need far less snow removal,
might even reduce in size a bit. Bruce Roe

[bcroe]

Bruce: If/When you get the time, on average , +/-, about when do you adjust the tilts on the arrays ? Also, what are the tilt angles ?

Thank You.

Update, from flat on the ground, the elevation angle of E-W facing array are both 74 deg, the
original S facing is 23.5 deg, and the newest facing E is 75 deg (variable). The ultimate hope
is with better angles set twice a year, and other tweaks (3% less wiring loss, etc), perhaps a
few less panels will still generate enough for my needs. Bruce Roe

[J.P.M.]

Update, from flat on the ground, the elevation angle of E-W facing array are both 74 deg, the
original S facing is 23.5 deg, and the newest facing E is 75 deg (variable). The ultimate hope
is with better angles set twice a year, and other tweaks (3% less wiring loss, etc), perhaps a
few less panels will still generate enough for my needs. Bruce Roe

Bruce: Thank you.
Life is in the way just now, but the modeling is on my do list.
I'm considering using 11/15 and 03/15 for 1st/last snow dates on the var. tilt array unless you advise otherwise.

Q: Why the 23.5 deg. tilt on the big array ?

J.P.M.

[bcroe]

Bruce: Thank you.
Life is in the way just now, but the modeling is on my do list.
I'm considering using 11/15 and 03/15 for 1st/last snow dates on the var. tilt array unless you advise otherwise.

Q: Why the 23.5 deg. tilt on the big array ?

J.P.M.

Those sound like pretty good dates. The original big S array I asked to have a tilt option, but could not
get a drawing in advance. When it went up it was set at the low extreme for convenient construction
(another long story of issues). It turned out it would take a multi person crew with equipment to elevate
over 400 lb 10 feet in the air at 12 positions, twice a year. This was not a practical thing and likely
would have involved damage, so it has stayed put. Given that the total has been able to keep in
clipping any sunny day, better angle would not gain much energy. But winter energy and snow do
rather poorly, so possibly the 2018 design and fewer panels would be advantageous. Bruce Roe

[J.P.M.]

Those sound like pretty good dates. The original big S array I asked to have a tilt option, but could not
get a drawing in advance. When it went up it was set at the low extreme for convenient construction
(another long story of issues). It turned out it would take a multi person crew with equipment to elevate
over 400 lb 10 feet in the air at 12 positions, twice a year. This was not a practical thing and likely
would have involved damage, so it has stayed put. Given that the total has been able to keep in
clipping any sunny day, better angle would not gain much energy. But winter energy and snow do
rather poorly, so possibly the 2018 design and fewer panels would be advantageous. Bruce Roe

Understood. I'll fart around some with those dates.
Sure not my call, but if I was doing a redesign, I might consider a tilt closer to latitude (or maybe a bit more for snow considerations). Just sayin'.

[bcroe]

I did not pick it, but could not change it. Bruce