CSI EPBB Calculator Question

[silversaver]

1.) I understand how capitalism works and I don't consider it a dirty word.
2.) Vendors make money putting equipment on property, not necessarily optimizing size or orientation, or reducing an electric bill. That's just the way it works and I for one see no sense pretending otherwise. If I was still a salesperson, I bet I could talk most customers into a less than optimum orientation based on aesthetics or some other nontechnical reason and thus sell more product.
3.) I'm of the opinion that most consumers are clueless that panel orientation and site conditions can have a large effect on performance and thus cost effectiveness. One example: I spoke with one not too elderly neighbor a couple of years ago who had some southerly facing roof with a few stink vents that would have limited system size, and a northerly roof about the size of a Costco parking lot. Other roofs had sort of limited access, but were probably useable to some degree. I was not there, but the neighbor swears the salesperson told the neighbor that placement on the north roof would be OK because the panel efficiency would increase because they would run cooler - and, not being in direct sun and they would last longer as well. This is NOT an indictment of more than a few, if that many vendors as much as an example, perhaps a bit over the top, of how ignorant consumers can be. I think the neighbor may have embellished things a bit, but was still clueless.

4.) The optimum placement of any panels, including Slowpoke's, IMO, is a rather complicated function of a lot of variables, a few of which might be: Weather, irradiance patterns, shading, solar fraction desired, type of billing, energy use patterns, including hourly, monthly and seasonal, panel characteristics including efficiency as f(temp., low light performance, etc.), type of roof material, age and ease of access, and inverter type and placement for starters.
5.) I wouldn't hazard a guess on optimum orientation or size for that matter in any situation without a pretty firm prior grip on energy use and pattern via an energy audit, solar fraction desired and a site visit to at least look at shade patterns.
6.) All that said, and looking at the photos, and assuming it's reasonably clear to the east with pretty much time of day independent cloud patterns, I'd probably think about heading in the direction (after a serious attempt at getting as much of the aforementioned information as possible) of starting at the southeast corner of the roof and place panels on the south portion until I hit shade at ~~1400 hrs. solar time around the winter solstice. then, add 2 or 3 panels on the east facing portion for every 1 additional panel on the south until I hit a 12/21 shadow at ~~ 1530-1600 solar time on the south portion. Then I'd stop, run a simulation (SAM, etc.) and see what I had. I'd iterate the simulations back and forth until I got the combination of size and orientation that resulted in the lowest blended (average) cost per kWhr. paid for what I still had to buy from the POCO. At least that would be the order of battle I'd start with and which would probably change after the 1st iteration. Once I'm happy with my attempt at logical methods, I'd then let the customer choose. They can, and often do then let other forces hold sway as is their right and choice. I'd also keep in mind that sometimes you can't get everything you want and still maintain the cost effectiveness goals you started with. Also, goals change as the quest unfolds.

FWIW.

Thanks for the feedback. I agree with you. In reality, none of the sales rep will follow up that method. Why? Since I join the forum until now, I haven't seen single post about anyone asking for best installer without asking for price first. If your price isn’t good, you are not even on the list. I still remember the best proposal I received were from an installer offering me 24 X LG280 with Enphase M250 micro inverters. The presentation was nice and detail. When I look at the price, I just can't believe it. Yes, I read the number twice. $42,985 I did call the Sales Rep asking if he had made the mistake, the answer is No. I have forgotten which company was it, but I still remember the price.

[silversaver]

yes, but what is interesting also is the time of use data. we have pretty high usage in the afternoon and evenings when the kids are back from preschool and the lights in the kitchen/family room are pretty much on from about 4:30pm until the kids bedtime (usually around 830-9). so it would be nice if the combination of TOU rates and longer solar production in the afternoons from more of a west facing array offset the higher loads.

we won't know until we get there because our production drops dramatically at 4 and then disappears around 4:30 right now. we aren't on TOU yet but may sign up after we acquire an EV this summer. with the longer days coming up, and DST coming up, i think that our west array is going to churn out some really big numbers. so if we switch to TOU, we could really reap big benefits from having a west array that produces longer into the day than our south array. our kids are only 3 and 5 so our patterns of heavy afternoon use could be in play for many many years.

here is a chart of our typical daily use:

[ATTACH=CONFIG]3670[/ATTACH]

in any case, sorry to digress OP.

Your utilities company is very nice by offering each 15 min interval, unlike SCE's hourly. Too bad that Locus monitoring will not giving you each arrays' output but sum. You can still get each inverter's E-Day reading and find out which orientation offering you the best result at this season. The Locus power generated report is almost the same comparing with SMA inverter shown. For example, I'm getting 24.51kWh on SMA and 24.35kwh on Locus.

[russ]

yes, but what is interesting also is the time of use data. we have pretty high usage in the afternoon and evenings when the kids are back from preschool and the lights in the kitchen/family room are pretty much on from about 4:30pm until the kids bedtime (usually around 830-9). so it would be nice if the combination of TOU rates and longer solar production in the afternoons from more of a west facing array offset the higher loads.

we won't know until we get there because our production drops dramatically at 4 and then disappears around 4:30 right now. we aren't on TOU yet but may sign up after we acquire an EV this summer. with the longer days coming up, and DST coming up, i think that our west array is going to churn out some really big numbers. so if we switch to TOU, we could really reap big benefits from having a west array that produces longer into the day than our south array. our kids are only 3 and 5 so our patterns of heavy afternoon use could be in play for many many years.

here is a chart of our typical daily use:

[ATTACH=CONFIG]3670[/ATTACH]

in any case, sorry to digress OP.

That is what I call specific situation. In my case we usually use two T5 tube lamps, two laptops, a TV and not much else in the evening -cooking is mainly days.

Solar production is in the window of 0900 hours to 1600 hours - anything before or after is minimal - in the winter even shorter.

[J.P.M.]

No one is in the market for free service. It will be really interesting to find out what will be your suggestion of the "optimum" placement for these panels.

1.) I understand how capitalism works and I don't consider it a dirty word.
2.) Vendors make money putting equipment on property, not necessarily optimizing size or orientation, or reducing an electric bill. That's just the way it works and I for one see no sense pretending otherwise. If I was still a salesperson, I bet I could talk most customers into a less than optimum orientation based on aesthetics or some other nontechnical reason and thus sell more product.
3.) I'm of the opinion that most consumers are clueless that panel orientation and site conditions can have a large effect on performance and thus cost effectiveness. One example: I spoke with one not too elderly neighbor a couple of years ago who had some southerly facing roof with a few stink vents that would have limited system size, and a northerly roof about the size of a Costco parking lot. Other roofs had sort of limited access, but were probably useable to some degree. I was not there, but the neighbor swears the salesperson told the neighbor that placement on the north roof would be OK because the panel efficiency would increase because they would run cooler - and, not being in direct sun and they would last longer as well. This is NOT an indictment of more than a few, if that many vendors as much as an example, perhaps a bit over the top, of how ignorant consumers can be. I think the neighbor may have embellished things a bit, but was still clueless.

4.) The optimum placement of any panels, including Slowpoke's, IMO, is a rather complicated function of a lot of variables, a few of which might be: Weather, irradiance patterns, shading, solar fraction desired, type of billing, energy use patterns, including hourly, monthly and seasonal, panel characteristics including efficiency as f(temp., low light performance, etc.), type of roof material, age and ease of access, and inverter type and placement for starters.
5.) I wouldn't hazard a guess on optimum orientation or size for that matter in any situation without a pretty firm prior grip on energy use and pattern via an energy audit, solar fraction desired and a site visit to at least look at shade patterns.
6.) All that said, and looking at the photos, and assuming it's reasonably clear to the east with pretty much time of day independent cloud patterns, I'd probably think about heading in the direction (after a serious attempt at getting as much of the aforementioned information as possible) of starting at the southeast corner of the roof and place panels on the south portion until I hit shade at ~~1400 hrs. solar time around the winter solstice. then, add 2 or 3 panels on the east facing portion for every 1 additional panel on the south until I hit a 12/21 shadow at ~~ 1530-1600 solar time on the south portion. Then I'd stop, run a simulation (SAM, etc.) and see what I had. I'd iterate the simulations back and forth until I got the combination of size and orientation that resulted in the lowest blended (average) cost per kWhr. paid for what I still had to buy from the POCO. At least that would be the order of battle I'd start with and which would probably change after the 1st iteration. Once I'm happy with my attempt at logical methods, I'd then let the customer choose. They can, and often do then let other forces hold sway as is their right and choice. I'd also keep in mind that sometimes you can't get everything you want and still maintain the cost effectiveness goals you started with. Also, goals change as the quest unfolds.

FWIW.

[Volusiano]

I think we all saw this one several months ago with several posters, including me of the opinion it was pretty much B.S. for several reasons.

I wouldn't call it B.S. I thought that they explain well the reasoning why west facing panels in some cases is better than south, primarily due to TOU advantage. They didn't say that west panels are better than south panels "no matter what". If the reader's take away is that "west panels are better than south panels no matter what", then the reader has not read or fully understand the point of why it may be the case from the article.

[bando]

When you casually say East or West based on magnetic North or the way the local roads are named, you can give entirely the wrong impression about which direction the panels would be facing.
There is far too much North in your "East" facing roof for good performance.

Instead of looking at PV watts for 90 and 270 degrees, you need to off set both of those azimuths by (my guesstimate) 30 degrees or more in the direction that favors East and penalizes West.

yes i get that and i don't mean to be "casual" other than being lazy and not typing out my azimuths every time. mine are 159 and 249 and i guess that means the "east" is 69 which yes, has north in it as well.

i was trying to convey is that in this area (92130), the morning coastal weather can be very drastic with fog and marine layer such that i don't believe you would say east and west are equal, even if you were my next door neighbor and your roof is perfectly at 90 and 270. when your morning sun hours are compromised by those conditions, you lose a ton of valuable sunlight which may or may not affect people even 1-2 miles more inland from where we are. and with the potential upside of longer days benefitting the west in summer's peak load hours (based on that article), maybe there could be reasons that more western facing is preferred. like i said, we haven't gotten there yet so i can't really say. however when the time comes and we consider TOU, the math could indeed prove that to be the case. i won't know for sure until we decide to go down that path. right now it's just food for thought , nothing else

[J.P.M.]

also i recently read this article about south vs. west arrays and found it very interesting. may or may not be relevant in your case but interesting nonetheless

http://energyblog.nationalgeographic...ong-direction/

I think we all saw this one several months ago with several posters, including me of the opinion it was pretty much B.S. for several reasons.

[inetdog]

No wonder the installer choose SE than NW. You should put panels on the South and East other than West if necessary. Your East is better than West base on Sat image.

bando:
When you casually say East or West based on magnetic North or the way the local roads are named, you can give entirely the wrong impression about which direction the panels would be facing.
There is far too much North in your "East" facing roof for good performance.

Instead of looking at PV watts for 90 and 270 degrees, you need to off set both of those azimuths by (my guesstimate) 30 degrees or more in the direction that favors East and penalizes West.

[bando]

What they are saying is that orientation can be site specific and situation specific. Same old, same old.

yes, but what is interesting also is the time of use data. we have pretty high usage in the afternoon and evenings when the kids are back from preschool and the lights in the kitchen/family room are pretty much on from about 4:30pm until the kids bedtime (usually around 830-9). so it would be nice if the combination of TOU rates and longer solar production in the afternoons from more of a west facing array offset the higher loads.

we won't know until we get there because our production drops dramatically at 4 and then disappears around 4:30 right now. we aren't on TOU yet but may sign up after we acquire an EV this summer. with the longer days coming up, and DST coming up, i think that our west array is going to churn out some really big numbers. so if we switch to TOU, we could really reap big benefits from having a west array that produces longer into the day than our south array. our kids are only 3 and 5 so our patterns of heavy afternoon use could be in play for many many years.

here is a chart of our typical daily use:

Screen Shot 2014-01-29.jpg

in any case, sorry to digress OP.

[silversaver]

FWIW, they also know what will put the most $ in their pocket, and that may not be the optimum placement.

No one is in the market for free service. It will be really interesting to find out what will be your suggestion of the "optimum" placement for these panels.

[russ]

also i recently read this article about south vs. west arrays and found it very interesting. may or may not be relevant in your case but interesting nonetheless

http://energyblog.nationalgeographic...ong-direction/

What they are saying is that orientation can be site specific and situation specific. Same old, same old.

[bando]

also i recently read this article about south vs. west arrays and found it very interesting. may or may not be relevant in your case but interesting nonetheless

http://energyblog.nationalgeographic.com/2013/11/20/are-those-solar-panels-facing-the-wrong-direction/

[bando]

yes in So Cal you need to deal with "microclimates" and our area (zip 92130) is considered coastal north county. we get a lot of days with morning clouds and/or fog or marine layer for much of the year. so the full burn off of those conditions to full sun can take until 11am-12 on some days. and by that time, the sun is facing the south roof and the east is no longer getting a direct hit.

before i knew anything about solar, i would have wanted an array on the east roof because that is our rarely seen/used sideyard AND the main elec panel is right there. it's also a large roof section that i could easily get over 40 panels on. but that side just doesn't get a lot of direct sunlight (it gets some decent indirect sunlight). of course, every company that came to bid immediately nixed that idea. so instead we have the arrays very far away and had to run over 200 ft of conduit thru the attic space out to that side of the house.

every situation is different, and the orientation, roof characteristics and location all impact the placement of the panels. did the installer get up on the roof and take some readings?

[slopoke]

i see what you mean about hips and valleys! you have quite a lot of "sections" to work around

that redwood is pretty close and looks tall. is that neighbor slightly above you also

The neighbor to my left and right are level with me. My neighbors to the rear are above.

[J.P.M.]

It is depend on orientation of the roofs, chimney, shade...etc. Most of solar companies are pro, they know what will bring the max output for you

FWIW, they also know what will put the most $ in their pocket, and that may not be the optimum placement.