North facing Panels

[x3uay9]

my boss has had an install with SunPower 327 watt panels on a space limited roof, Ok they are more expensive but 13 panels as you suggest would get you over 4kw using them and would perform much better than a north facing system.

Most manufacturers also do panels in the 250-290 watt range so might be worth getting a few quotes for different size schemes and go from there.

[Kingram]

https://www.solarpowerworldonline.co...solar-modules/
I noticed a house here in Arizona which is about a mile from me that has 30 panels total and they are all on the North side of the roof, it is such a strange roof design and that was their only option. Now that is wanting solar really bad but according to the article above North facing panels may not be as bad as we once thought. I'm now wondering what the average roof pitch is in the southwest .

[DanKegel]

I believe the meaning of what I wrote is reasonably clear

Perhaps. I was just trying to help.

I should also have mentioned that as of 2008, about 68% of Californians lived near the coast, according to

http://www.census.gov/prod/2010pubs/p25-1139.pdf

So it's possible, or maybe even likely, that the majority of Southern Californians experience June Gloom.

[J.P.M.]

Or, more briefly, "I think that mostly affects *coastal* Southern California, isn't it?"

https://en.wikipedia.org/wiki/June_Gloom

Still at your rude communication methods, huh Dan ?

I believe the meaning of what I wrote is reasonably clear. If it makes you happier to redefine what I wrote without asking me what I meant, feel free, but do so in your own mind and don't do my writing for me. I consider such methods, of which your post is a good example, rude and presumptuous.

If you truly want to know something - which in this case I doubt - ask, but don't ask leading questions, at least not of me.

[DanKegel]

BTW, I believe there's a lot of desert in SO. CA that doesn't see a lot of morning/coastal fog or May/June cloudiness. To say or imply all of SO. CA climate is described by what happens relatively near the coast may not be entirely accurate. My location is ~ 1,400 ft. above sea level and while I get some morning fog, it almost always burns off by 0800 or so. I watch the fog retreat to the coast as I do my morning rants. Just sayin.

Or, more briefly, "I think that mostly affects *coastal* Southern California, isn't it?"

https://en.wikipedia.org/wiki/June_Gloom

[J.P.M.]

The weather is what it is, and it's not climate. Climate's what you expect. Weather is what you get. Solar models use what's probably best described as climate modeling.

As Sensij notes, and as PVWatts info screens discuss, that, or any other model cannot estimate any short period's solar production any more accurately than a weather forecast. I would suggest however that while PVWatts states that monthly results from the model can vary by up to +/- 30 % vs. for an actual month, yearly values can also vary by as much as +/- 10%.

I've got a clear sky climate model that estimates my array will produce about 11,140 kWh/yr. using Miramar TMY3 temp. & wind data and the HDKR model for clear sky irradiance. The same model, using TMY3 Miramar data including irradiance comes up with 9506 kWh/yr., or 85.4% of a clear sky.

My array has been live since solar noon, 10/17/2013. zip 92026, about 20 airline miles from the coast. I keep a running total on the 365 days of prior array production since 10/18/2014. The lowest prior 365 day running total is 9,033 kWh/365 days. The highest prior 365 day running total is 9,644 kWh/365 days. Average, 9,298 kWh/prior 365 days. Std. dev. for prior 365 day running total is 187.3.

So far the array has produced 24,628 kWh. the theoretical clear sky production might be about 30,170 kWh. 24628/30170 = 81.6%, or about 3.8% shy of model est. I've not got the #'s handy for actual clearness index at my location vs. the clearness index for the TMY3 data, as it's not been a priority, but I'm working on it.

BTW, I believe there's a lot of desert in SO. CA that doesn't see a lot of morning/coastal fog or May/June cloudiness. To say or imply all of SO. CA climate is described by what happens relatively near the coast may not be entirely accurate. My location is ~ 1,400 ft. above sea level and while I get some morning fog, it almost always burns off by 0800 or so. I watch the fog retreat to the coast as I do my morning rants. Just sayin.

[sensij]

Damn weather is going to make a lot of the estimations from pvwatts wrong. Hope it clears up for you guys.

The TMY files that PVWatts uses are reasonably aware of the seasonal patterns. NREL's data suggests that the modeled output for any particular month may vary by 30% from actual output, but those variances tend to cancel out over the year. I'm at about 80% of my June 2015 production with another week to go, so this year doesn't seem too different than last.

[SunEagle]

For May and June definitely. Usually it ends in July/August, but this has been a strange year.

Damn weather is going to make a lot of the estimations from pvwatts wrong. Hope it clears up for you guys.

[jflorey2]

Is that type of weather typical for southern CA?

For May and June definitely. Usually it ends in July/August, but this has been a strange year.

[SunEagle]

That's definitely been true a few days lately.

Is that type of weather typical for southern CA?

[DanKegel]

That's one factor. A second factor is that in Southern California, during the best solar months, we tend to get low clouds (June gloom) from morning until noon or so. Thus orienting them southwest rather than west maximizes production during peak months.

That's definitely been true a few days lately.

[jflorey2]

There must be a time of use billing. If time of use was not in the equation east and west would be 12% less than south. is that what you are saying?

That's one factor. A second factor is that in Southern California, during the best solar months, we tend to get low clouds (June gloom) from morning until noon or so. Thus orienting them southwest rather than west maximizes production during peak months.

[J.P.M.]

Just to close this off and give some prospective owners coming to this thread for some advice about West-facing panels vs North/South/East, I've done some calculations based on PVWatts data and SCE TOU rates and West-facing panels can be nearly as cost-effective as South-facing panels when you take TOU rates into consideration.

For example, an 2.5kW system where I live in SoCal can produce the following:

-- South-facing: 4250kWh and $780 in NEM credits
-- West-facing: 3725kWh and $770 in NEM credits
-- East-facing: 3576kWh and $610 in NEM credits

As you can see, while South-facing panels do indeed produce the most energy and NEM credits, West-facing panels are within 1.5% monetarily, despite the fact that they produce over 12% less energy. East-facing panels, while producing similar amounts of energy to West-facing panels, don't even come close to generating the same amount of NEM credits.

I didn't even bother doing North-facing when I did the calculations as annual production would be abysmal, in addition to receiving no "help" from TOU rate structures.

In my eyes, West-facing panels are just as good as South-facing panels from a financial standpoint. East-facing panels are not nearly as "lucrative," and North-facing panels should never even be considered (I'm obviously talking about the Northern hemisphere and not near the equator).

If you are the type to be concerned about your carbon footprint (due to offsetting the coal power plants during times of the day with of high energy demand), then West-facing panels are a no-brainer. This is a reason why certain municipalities are giving credits to home builders that provision for solar panels on West-facing roofs.

Location, location, location. Probably and generally a trend in So. CA, and I,m not disputing the particular findings, but not always necessarily as shown, depending on location and POCO T.O.U. tariffs at that locatiop. If west facing is the only choice, so be it. Around here West facing is probably close, but still the 2d best. Again, every situation will be different, as well as the idea that not every choice is exactly a 180 or 270 deg. azimuth. BTW, T.O.U. as well as all tariffs will change over time. Knowing that, and if given the choice, I'll take max. production facing south and take my chances.

[john phillips]

There must be a time of use billing. If time of use was not in the equation east and west would be 12% less than south. is that what you are saying?

[SolarFuture]

Just to close this off and give some prospective owners coming to this thread for some advice about West-facing panels vs North/South/East, I've done some calculations based on PVWatts data and SCE TOU rates and West-facing panels can be nearly as cost-effective as South-facing panels when you take TOU rates into consideration.

For example, an 2.5kW system where I live in SoCal can produce the following:

-- South-facing: 4250kWh and $780 in NEM credits
-- West-facing: 3725kWh and $770 in NEM credits
-- East-facing: 3576kWh and $610 in NEM credits

As you can see, while South-facing panels do indeed produce the most energy and NEM credits, West-facing panels are within 1.5% monetarily, despite the fact that they produce over 12% less energy. East-facing panels, while producing similar amounts of energy to West-facing panels, don't even come close to generating the same amount of NEM credits.

I didn't even bother doing North-facing when I did the calculations as annual production would be abysmal, in addition to receiving no "help" from TOU rate structures.

In my eyes, West-facing panels are just as good as South-facing panels from a financial standpoint. East-facing panels are not nearly as "lucrative," and North-facing panels should never even be considered (I'm obviously talking about the Northern hemisphere and not near the equator).

If you are the type to be concerned about your carbon footprint (due to offsetting the coal power plants during times of the day with of high energy demand), then West-facing panels are a no-brainer. This is a reason why certain municipalities are giving credits to home builders that provision for solar panels on West-facing roofs.