Solar panel angle for grid tie vs. summer offgrid vs. yearround offgrid

Hi;
The standard recommendation for solar panel angle is your latitude;
ex. 45 latitude; 45 angle from horizontal
Panels work best when perpendicular to the suns rays, so 45 from horizontal is a
a compromise between summer (45 + 23 = 68) high angle sun with optimal panel angle of 22 from horizontal, vs.
winter (45-23 = 22) low angle sun with optimal panel angle of 68 from horizontal.

But I do not think the latitude angle works best for typical situations.
i) Grid tie:  This depends upon the utility deal.
My jurisdiction pays 1:1 for energy exchange, cand cancels any excess export above consumption  to 0 at the end of the year.
I should  maximize annual production up to consumption, at minimum capital cost.
In my climate that means a lower panel angle, towards summer optimum, because that maximizes annual production per panel & racking.
Coincidentally, bungalow roofs are less than 45, and so approximate a good summer angle for 1:1 grid tie.
From the utility point of view, they would prefer me to maximize winter production when demand is higher here; eventually regulations will likely push that way.

ii) Summer use off grid: similar to grid tie; optimize near the summer angle to minimize investment in panels & racking required.

iii) Year round off grid:  panels near winter angle will maximize scarce winter production, and shed snow better.
The cost of panels is now low,  so 'wasting' panels in summer is not a big detriment.
But panels need racks, and rack costs have not decreased, even if home built.

It doesn't matter too much as long as you're within 10-20 degrees of your latitude (for equator-facing panels). The biggest advantage I've found from a greater angle is that they stay cleaner. The close your panels are to horizontal, the more they tend to accumulate dust, pollen, bird poop, and other things that get washed off by rainfall (snow is not an issue here). My biggest problem is lichen and moss, and those don't seem to care much about the angle.

An interesting side note is that some people are using vertically-mounted bifacial panels facing E-W and using them in conjunction with a traditional equator-facing array. This adds big shoulders in the morning and afternoon to extend the midday peak period.

Douglas Campbell wrote:Hi;
The standard recommendation for solar panel angle is your latitude;
ex. 45 latitude; 45 angle from horizontal
Panels work best when perpendicular to the suns rays, so 45 from horizontal is a
a compromise between summer (45 + 23 = 68) high angle sun with optimal panel angle of 22 from horizontal, vs.
winter (45-23 = 22) low angle sun with optimal panel angle of 68 from horizontal.

But I do not think the latitude angle works best for typical situations.
i) Grid tie:  This depends upon the utility deal.
My jurisdiction pays 1:1 for energy exchange, cand cancels any excess export above consumption  to 0 at the end of the year.
I should  maximize annual production up to consumption, at minimum capital cost.
In my climate that means a lower panel angle, towards summer optimum, because that maximizes annual production per panel & racking.
Coincidentally, bungalow roofs are less than 45, and so approximate a good summer angle for 1:1 grid tie.
From the utility point of view, they would prefer me to maximize winter production when demand is higher here; eventually regulations will likely push that way.

ii) Summer use off grid: similar to grid tie; optimize near the summer angle to minimize investment in panels & racking required.

iii) Year round off grid:  panels near winter angle will maximize scarce winter production, and shed snow better.
The cost of panels is now low,  so 'wasting' panels in summer is not a big detriment.
But panels need racks, and rack costs have not decreased, even if home built.

most of my work is off grid or grid tied with batteries in rural areas. At 45 degree latitude I almost always go with a 45 degree fixed angle ground mount due to costs, regulation, snow and year round efficiency. If you were only net metering, a roof angle of 4-6/12 is ideal as it maximizes yearly returns but by the time you get engineering on the roof, municipal permits to modify the structure and you factor in increased insurance costs and loss to snow cover the production gain and cost savings of roof mount are gone here. Adjustable  racks are more expensive than fixed as well so with the price of panels you just add panels to a fixed angle to compensate. That is where my thinking is these days.
Cheers,  David Baillie

I suspect, the closer to the poles, the more this matters.  At 49-ish, so long as I use the low efficiency panels, changing the angles doesn't have a significant advantage in our experiments.  They work great year round.

If we were further north or used high efficiency panels, angle matters more.  But, those panels don't work here from the middle of October to the start of may, so there's no point changing the angle for winter. There is not enough sunlight for the panels no matter how perfectly they are angled.  The world is too overcast.

So type of panels is a big part answering the question if it's worth changing the angle.

Personally, I find there is so much solar power information that is useless to my situation, the best thing to do is experiment before investing in a full roof installment.


As a side note, it used to be suggested that the angle of the roof follow the latitude too.  This helps with rain, snow, and passive heating and cooling.  But we don't do that so often anymore.

What are you refering to by low efficiency panels?

r ransom wrote:

If we were further north or used high efficiency panels, angle matters more.  But, those panels don't work here from the middle of October to the start of may, so there's no point changing the angle for winter. There is not enough sunlight for the panels no matter how perfectly they are angled.  The world is too overcast.

So type of panels is a big part answering the question if it's worth changing the angle.

Personally, I find there is so much solar power information that is useless to my situation, the best thing to do is experiment before investing in a full roof installment.


As a side note, it used to be suggested that the angle of the roof follow the latitude too.  This helps with rain, snow, and passive heating and cooling.  But we don't do that so often anymore.

Something I've learned about solar power that I haven't seen documented or herd of anywhere. Is temperature soak in hot weather when the panels are perpendicular to the sun. I have found in my personal use that being 15ish degrees off is better than being dead on as the panels don't get as hot and actually "seem" to produce more power. to truly test this one would need two sets of identical panels set at differing angles with thermometers to know if this is fact or fiction.

One thing I can state for a fact is that the only time I've seen my panels produce 100% or 100+% is in sub freezing weather. I have seen approximately 105% charging in sub freezing weather on super sunny winter days.

R Ransom pretty much covered the "year round weather effect", but I had also thought of another factor not mentioned:

Do you work from home, and do you have the ability to control your own hourly schedule?

If outdoor light wasn't such a limited thing for chunks of my year, I could set my hours for things like cooking meals, based on taking the best advantage of the solar panels. I need consistency in my eating schedule, but that doesn't mean it can't be consistently at 4 o'clock because I decided that was the most cost effective.

If you're tied to a worky job with defined hours, that's trickier.

David Baillie wrote:What are you refering to by low efficiency panels?

r ransom wrote:

If we were further north or used high efficiency panels, angle matters more.  But, those panels don't work here from the middle of October to the start of may, so there's no point changing the angle for winter. There is not enough sunlight for the panels no matter how perfectly they are angled.  The world is too overcast.

So type of panels is a big part answering the question if it's worth changing the angle.

Personally, I find there is so much solar power information that is useless to my situation, the best thing to do is experiment before investing in a full roof installment.


As a side note, it used to be suggested that the angle of the roof follow the latitude too.  This helps with rain, snow, and passive heating and cooling.  But we don't do that so often anymore.

monocrystalline
For California living, where many of the early  studies are done, poly was considered most effective as it gathered good energy during direcf sunlight hours.  So this is what they market to us as most efficient to us, even though they don't work well in our climate

r ransom wrote:....
monocrystalline
For California living, where many of the early  studies are done, poly was considered most effective as it gathered good energy during direcf sunlight hours.  So this is what they market to us as most efficient to us, even though they don't work well in our climate

Did you say the variety you meant?  Classic arguments for low light and indirect usually list amorphic instead of poly crystalline.  Under cloud cover they produce some power where the power is mostly blocked by the other 2 because they utilize different frequencies.  

Typical rule of thumb for solar is lattitude + 10 degrees but  it really depends on your weather, power needs by season and a host of other factors.  

Have half the sun in winter but twice the power need then you better optimize for that part of your solar.  

Need to run big air conditioners in summer months then you might want to optimize for that.  Since your day is potentially way longer in summer you may to spit you panel directions 3 ways with some pointing south east, some south and some south west for example so you always have good power to run those air conditioners.

Your need really depends on your use.

Another factor I have seen is to have a set of panels set for morning sun, and another for evening sun.        This helps to have the distribution of power very steady for the day.

Engineer 775   on youtube does this, and I see  a good deal of wisdom in doing this.

C. Letellier wrote:

r ransom wrote:....
monocrystalline
For California living, where many of the early  studies are done, poly was considered most effective as it gathered good energy during direcf sunlight hours.  So this is what they market to us as most efficient to us, even though they don't work well in our climate

Did you say the variety you meant?  Classic arguments for low light and indirect usually list amorphic instead of poly crystalline.  Under cloud cover they produce some power where the power is mostly blocked by the other 2 because they utilize different frequencies.  

I'm not in charge of the solar experiments on the farm, so I don't need to know the vocabulary.  That is the word that got the replacement for one of the experiments and the person was extremely satisfied.  It works well in our sun rich summer and overcast winters.

Solar power seems to be like gardening.  There are plenty of people who love to geek out and sell stuff with absolute confidence there is one best way.  But every garden is unique.  Soil, weather, human element, etc.   We found that the "best setup" is only a starting point for experiments to discover what actually works for our location and lifestyle.   We take the information we gain from the small experiments, adjust, make new, larger experiments, and gather more information while we save to get the roof redone and solar added in a few years.  All the time reducing our needs so we don't need such a large system for the main house.

One surprising result is that multiple smaller systems have a lot more resilience than larger ones.  We didn't expect that, so will take it into account when it comes time for the final design.

Mart Hale wrote:Another factor I have seen is to have a set of panels set for morning sun, and another for evening sun.        This helps to have the distribution of power very steady for the day.

Engineer 775   on youtube does this, and I see  a good deal of wisdom in doing this.

One of the new patterns is to use vertical bifacial oriented north-south.  Add reflectors on both side at the base so they run on reflected light too.  They can actually have 2x or 3x the light on the panel much of the time.  

C. Letellier wrote:

Mart Hale wrote:Another factor I have seen is to have a set of panels set for morning sun, and another for evening sun.        This helps to have the distribution of power very steady for the day.

Engineer 775   on youtube does this, and I see  a good deal of wisdom in doing this.

One of the new patterns is to use vertical bifacial oriented north-south.  Add reflectors on both side at the base so they run on reflected light too.  They can actually have 2x or 3x the light on the panel much of the time.  

There was lots of hype about that.      I do like the testing done on this video...

Mart Hale wrote:

C. Letellier wrote:

Mart Hale wrote:Another factor I have seen is to have a set of panels set for morning sun, and another for evening sun.        This helps to have the distribution of power very steady for the day.

Engineer 775   on youtube does this, and I see  a good deal of wisdom in doing this.

One of the new patterns is to use vertical bifacial oriented north-south.  Add reflectors on both side at the base so they run on reflected light too.  They can actually have 2x or 3x the light on the panel much of the time.  

There was lots of hype about that.      I do like the testing done on this video...

Interesting.  Will need to keep watching the data.

My one other problem with bifacials otherwise is I don't see how to convert them to PVT operation without major losses.