East+West roof may now be "better" than southern exposure ?

[specialgreen]

My east-facing array appears that it will have a break-even of 12 years. That includes the cost of borrowed money (using my Credit Union's home equity rate), and 66% of the cost of the new roof I put-on prior to solar installation. If a similar west-facing array had a payback of 15 years, would these east/west arrays "be a waste" because they pay for themselves slower than a smaller south-facing roof would? Or would they be viable because, regardless, they still do pay for themselves? Would you rather invest $20,000 which grows at 10% or invest $34,000 which grows at 8% ? You only get to pick one. I think "it depends": on whether you have the extra $14k; on whether your motivation is purely financial.

I think you're spot-on that "things will change," and compensation by the utility will go down. Simple net-metering pays as if the time of production didn't matter. At some point, PV generation will be high enough that time _does_ matter. I think we will see efforts to force "curtailment" on residential PV producers "to promote grid stability". Or production caps like Germany. Or widespread Time of Production metering ("ToP"?). That would encourage a shift to east/west arrays.

[J.P.M.]

My original post said: I'm now glad my roof is E-W, because I want to maximize generation on my house (not maximize ROI), and E-W gives twice as much surface area (and about 60% more total generation) versus a south-only roof.

My only other way to generate as many kw-hrs as I consume would be by subscribing to a Community Solar Garden. Perhaps in some states, Solar Gardens are as good an investment as rooftop, but not in mine.

I think there could also be other future reasons for people with E-W roofs to consider installing solar. For example, Germany is limiting rooftop solar feed-in to 70% of nameplate production capacity. They see enough value in having a flatter solar generation curve, that they are "curtailing" solar production at the peak. If that value is passed-on to consumers (such as in ToU production rates), then it would encourage consumers with E-W roofs to consider installing solar.

Another example is that solar modules are a declining portion of the total cost of installing solar. The cost to get the crew and materials on-site, and the cost of permitting and interconnection are more constant. It is possible that a 40-module East/West array could cost 60% more than a 20-module South-facing array, but also produce 60% more kw-hrs. In that case, the years-to-breakeven of the two systems would be identical (even before any ToU production bonus).

I think that in the past, many people looked at an East-West rooftop and said "bummer. That's not good for solar." As module prices drop, and as utilities start to value a flatter production curve, maybe people will look at a house with an E-W roof and say "cool, great roof for solar!"

I read what you wrote and believe I understand it.

I read your post from above and believe I understand that as well.

I also believe I understand something of solar process economics. You may or may not understand or see things as I do. So be it and hail the difference. Not my money/life/business.

However, and only FWIW, my limited experience in such things suggests to me that the main reason why folks choose to install residential PV is with the hope it will reduce the long term cost of meeting a residential electric load. There are other reasons, but if the perceived economic benefit is not there, and that's usually a non starter. My limited experience also has given me the opinion that most folks are victims of their own ignorance and because of that ignorance wind up with residential PV systems that wouldn't stand muster if subjected to accepted methods of economic analysis - and that's usually with residential arrays that have pretty good orientations , not less than optimal for whatever reason(s). That is, for many, if not most residential applications, there is usually a higher than acceptable probability of paying more to provide electricity to a residence in the long run with a PV system than if the owners had taken other measures besides PV first and/or skipped the PV altogether. and most are unaware of it.

Put another way, if more folks knew what I think I may know, there would be a lot fewer arrays on residential property and those arrays would be a lot smaller. In your case, because economics seem to have a lower priority, you might still do what did, but you'd perhaps have a more realistic and perhaps more sobering way of looking at the economics of your decisions.

As for the future you write of, the economics will, in all probability, change as they always do. But if the recent past is any indication, the future may not be as rosy as you think. Example: Because POCOs are finding ways around NEM to lessen it's impact, some (many ?) areas such as mine have seen the value of the offset to electric bills decrease. In my area, because of the way(s) T.O.U. tariffs and mandates have changed, existing systems now offset about 20% or so less of a bill than before the rate restructuring.

Take what you want of the above. Scrap the rest.

[specialgreen]

It's also a waste of money... an E-W split will result in a more costly system than a more southerly orientation and a longer ROI.

My original post said: I'm now glad my roof is E-W, because I want to maximize generation on my house (not maximize ROI), and E-W gives twice as much surface area (and about 60% more total generation) versus a south-only roof.

My only other way to generate as many kw-hrs as I consume would be by subscribing to a Community Solar Garden. Perhaps in some states, Solar Gardens are as good an investment as rooftop, but not in mine.

I think there could also be other future reasons for people with E-W roofs to consider installing solar. For example, Germany is limiting rooftop solar feed-in to 70% of nameplate production capacity. They see enough value in having a flatter solar generation curve, that they are "curtailing" solar production at the peak. If that value is passed-on to consumers (such as in ToU production rates), then it would encourage consumers with E-W roofs to consider installing solar.

Another example is that solar modules are a declining portion of the total cost of installing solar. The cost to get the crew and materials on-site, and the cost of permitting and interconnection are more constant. It is possible that a 40-module East/West array could cost 60% more than a 20-module South-facing array, but also produce 60% more kw-hrs. In that case, the years-to-breakeven of the two systems would be identical (even before any ToU production bonus).

I think that in the past, many people looked at an East-West rooftop and said "bummer. That's not good for solar." As module prices drop, and as utilities start to value a flatter production curve, maybe people will look at a house with an E-W roof and say "cool, great roof for solar!"

[Robinhood-46]

Thanyou Bruce, very informative.my panels are much closer to vertical,i should think that this is due to the different distances from the equator. They are also SE and SW not east and west.My exposure is not optimal because of trees at sun rise and set. From what i gather i should be able to increase considerably the number of panels by turning more to the east and west. I think i'll add another 200 watts and play around with the angles for this winter and see how everything goes during the other seasons before adding any more. I have a lot more money than sense,so maybe next winter i'll add a few more on and leave them set for winter all year round so as to be able to mount them more effectively and not have to worry about them.
What I found suprising is the speed at which the production falls with the angle changes. My worry was having so many panels with direct sunlight on them,even though at different angles,would be way over the max for controller. It isn't the case.
My objective is a minimum of 30 amps into battery pack for 4/5 hours on a clear winter day. I think that it is possible, If all goes well i'll be well over 30 for a couple of hours and a little under for the rest. 2 to 2.5 kwh on a winters day is plenty enough for my needs. If my calculations are correct this would be pretty close to the performance of 500watts on a tracker and as you already know a tracker when the sun isn't shining is as usefull as an ashtray on a motorbike. Once again,thankyou muchly.James

[bcroe]

I see living without electric or fossil fuels as basically struggling to stay alive every day. When
you tired out or were incapacitated, you died. Life expectancy was short, but I suppose it
tended to improve the gene pool back then. Bruce Roe

[Robinhood-46]

How ever did people survive much less live off grid before PV ?
Most history books can answer that question,or you can tap cavemen in a research engine.
Independance for some people is very important and less so for others.
I'm a greedy person because I want as much independance as I can and I want as much confort as I can get.
Living in a cave will effectively give me lots of independance,but on the comfort side?
PV has made living in a cave a lot more attractive for many people,myself included.
I built a wooden chalet 5 years ago on a 9'000 m2 piece of woodland that I had bought about 15 years ago.
My intention was to have a place to go to get away from city life for my own personnal reasons.
It took 6 months for me to understand that this way of life is far more beneficiel for my own personnal wellbeing.
I now live here on a permanent basis and have no intentions of returning to the civil world.
During the last four years I have spent approximately 2'300 euros to have my present solar setup.
There are many things that I have learnt,I have made mistakes and some of them have been a waste of money and others a waste of time.
The experience has been very interesting and enlightening.
There are two main reasons that I became a member of this forum,firstly, after many hours of searching the net to find information to improve my installation it was clear that many people are exactly where I was 4 years ago. so by sharing my experience it would be helpfull to avoid others making the same mistakes that I had made.
Secondly, there are people who four years ago were exactly where I am today,therefore they can help me.
I think the most important thing is to respect each others differences and help other people do what they want and not what we think is best for them.

[J.P.M.]

I think that J.P.M is absolutely right when being connected to the grid. It's only when offgrid that there is an advantage. By increasing the length of the day for the charger you are decreasing the length of the night. The battery is being correctly charged earlier and later as with an expensive tracker. The increased number of panels is a considerable advantage when cloudy as shown by bruce. All of the advantages are only valid for bad weather conditions. Everybody with an offgrid system is only interested in the crappy weather conditions. In the middle of the summer the majority of sites are on float mode well before solar noon ( if it's not the case you have little hope of making it through the winter). For grid connections the bottom end of production is negligable when you consider annuel production, for off grid the bottom end of production is what decides how many years your battery pack will last.and for many people if they can play on the computer or not. I would very much like to hear other peoples thoughts and experiences with east west setups when offgrid. James

How ever did people survive much less live off grid before PV ?

[bcroe]

I think that J.P.M is absolutely right when being connected to the grid. It's only when offgrid that there is an advantage. By increasing the length of the day for the charger you are decreasing the length of the night. The battery is being correctly charged earlier and later as with an expensive tracker. The increased number of panels is a considerable advantage when cloudy as shown by bruce. James

Its more complicated than that, and each situation needs individual evaluation. In my case a 600 foot
loop of 4 gauge AC wire was already buried out to the inverters, and I didn't want to re bury a lot heavier.
That wire causes me a just tolerable 3% loss even at my high line voltage, and some 9V of rise at the
inverters, close to tripping out. Besides the physical plant, my contract limits me to 15 KW. So to get
any more energy a higher peak is not doable, it must be spread over the day. And of course so much
energy is being used to heat the house, something not generally recommended here. It all is needed.
Bruce Roe

[bcroe]

Bruce,
Your first graph is very representative of my set up. the other two clearly show the huge differences in our
set ups. I should image that the principal stays the same regardless of the scale. I do have two questions
that maybe you can clarify.
I think that the angles that you have stipulated 61 / 30 / 61 are the vertical inclination,could you give me an
idea of the rough angle of east and west? As in how much they are turned from south torwards the east
and west. Do you need to move them in the course of the year or have you found an optimal setup for all
year round. I cheated there, that was actually two questions.
My second question, what you call "mid day clipping" if I understand correctly is when my panels are
producing more electricity than my controller will allow into the battery therefore 40amps at 12 to 14.8 V
depending on batterie charge status. Is mid day clipping something that should be avoided to reduce
premature wear of controller or should I not worry at all about it all the time I stay well within the 1.5 x
rated charge current /power? James

I am doing net metering, so some things will not directly compare to an off grid.

Here is the arrangement of 3 panels used for measurements a couple years ago. Each single
panel was oriented directly east, south, or west, with means to read power output.


Test3dir.jpg

The angle listed is tilt up from flat on the ground. The facing direction is straight east, south,
or west. That brings up the question if the E/W should somewhat favor the rising/setting
sun, south in the winter, or north in the summer. After looking at my Solar Pathfinder chart,
I decided to leave them straight. For off grid you might want to favor sun in the south, to
get the most at poor winter time. For net metering, I might favor north, for when the most
summer energy may be collected. However, If the panels put me into clipping,
I would go more south. That is where I am, centered.

Several tilt angles were tried, and from June through Dec. The objective was to create the
flattest day long output, then bring up panel count to put the inverters at maximum. A couple
other tilt curves here.

PVm16Jn16.jpg

PV23Aug.jpg
PVm13Jn16.jpg



I expect your equipment indicates a maximum input level, mine does. However I regard
that as the level of the composite peak, not the actual equipage which can never all
approach rating at the same time. Not much written on this, be careful. Bruce Roe

[Robinhood-46]

I think that J.P.M is absolutely right when being connected to the grid. It's only when offgrid that there is an advantage. By increasing the length of the day for the charger you are decreasing the length of the night. The battery is being correctly charged earlier and later as with an expensive tracker. The increased number of panels is a considerable advantage when cloudy as shown by bruce. All of the advantages are only valid for bad weather conditions. Everybody with an offgrid system is only interested in the crappy weather conditions. In the middle of the summer the majority of sites are on float mode well before solar noon ( if it's not the case you have little hope of making it through the winter). For grid connections the bottom end of production is negligable when you consider annuel production, for off grid the bottom end of production is what decides how many years your battery pack will last.and for many people if they can play on the computer or not. I would very much like to hear other peoples thoughts and experiences with east west setups when offgrid. James

[foo1bar]

It's also a waste of money if it's unnecessary. In any event, for most every application, an E-W split will result in a more costly system than a more southerly orientation and a longer ROI. Smaller inverters do not save as much as smaller, more southerly arrays will save in initial costs.

I don't think that's true.
Assuming you're targeting a specific amount of kwh, I think an EW array can sometimes be more cost effective than a straight south array that produces the same kwh.
I would agree if you said south is *usually* more cost effective - especially if you have to pay labor for installation of modules.

A 5kW S pointing system gives 8,316 kwH/year for my location (Northern CA, 4/12 roof, 10% system losses)
An EW system would need to be 14% more DC watts to give equivalent kwh.
The EW system *might* save you $200 by being able to use smaller inverter. But it'd require 14% more in modules - assuming ~$0.54/W for modules, that's $2700 vs. $3038.
So still ~$138 more for an EW system producing same kwh.


So....
after doing the calculations on what I thought would be a counterexample, I have changed my mind and have to agree with you.
The exception would be where there's a bigger cost for a larger inverter (like having to upgrade the panel because of the larger inverter)

[Robinhood-46]

Bruce,
Your first graph is very representative of my set up. the other two clearly show the huge differences in our set ups. I should image that the principal stays the same regardless of the scale. I do have two questions that maybe you can clarify.
I think that the angles that you have stipulated 61 / 30 / 61 are the vertical inclination,could you give me an idea of the rough angle of east and west? As in how much they are turned from south torwards the east and west. Do you need to move them in the course of the year or have you found an optimal setup for all year round.
I cheated there, that was actually two questions.
My second question, what you call "mid day clipping" if I understand correctly is when my panels are producing more electricity than my controller will allow into the battery therefore 40amps at 12 to 14.8 V depending on batterie charge status. Is mid day clipping something that should be avoided to reduce premature wear of controller or should I not worry at all about it all the time I stay well within the 1.5 x rated charge current /power?
James

[bcroe]

There are a few reasons that an array might be set up as east-west. As James says it can lengthen
hours available to charge batteries. It can eliminate the problems of a tracker, by matching its output
under best sun, and out performing it under clouds. It could be the lack of a south facing mounting.
It could be about squeezing more energy through a limited AC facility.

Here, it is about clouds. Very poor output under clouds can be boosted by adding a lot of panels. At
this moment we are overcast, no clear shadows. Despite that, my reserve meter shows enough
energy is being collected to just balance the energy being consumed by heating the house in 30
degree F weather. Then the issue becomes what should be done with panel orientation when the
sun is good. Spreading the peak power over much of the day gathers more energy while minimizing
mid day clipping. Here are some curves from Sun Danzer and my yard. Bruce Roe

SunDazer10Oct17.png

NScurJn17.jpgPVm17Jn16.jpg

[Robinhood-46]

I have recently modified my panels from south facing to east west and I am at present very pleased with the results.
I started with a very small setup 4 years ago and progressively increased. After buying an MPPT charge controller of 40amps ( biggest i could find with limited budget) and increasing panel wattage to 600 I had no problems to keep 1,000 amps batterie bank fully charged all summer and well into the fall. Winter is obviously a different matter. By increasing my panels to 1,000 watts with 300 east 400 south and 300 west I have considerably increased the length of time that I have maximum power for the charge controller. It took a while to find optimum angles to keep production just under the 40amps. For my set up I find that 400 watts of panels is cheaper and more effective than buying and running a tracker. The ambient light of 1,000 is more than the ambient light of 600 when there is no or limited sun which is the only time that I worry for the health of my batterys.
Early days yet, and I'm sure I will be playing with number of panels and angles through the different seasons before I can find the correct set up for all year round or two angle changes a year.
If I'm not happy with end result I'll just upgrade controller I'll allready have the panels. Only time will tell but at present I find it very promoising.
James

[J.P.M.]

E/W let's you cram more daily kwh production into a smaller inverter too, keeping it running near peak longer. Less of a curve and more of a wide plateau. It's a valid strategy when the needs call for it.

It's also a waste of money if it's unnecessary. In any event, for most every application, an E-W split will result in a more costly system than a more southerly orientation and a longer ROI. Smaller inverters do not save as much as smaller, more southerly arrays will save in initial costs.