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.

All this conversation is missing one important point;

If the Solar Panels are NOT perpendicular to the Sun, you are loosing up to 60% of the Energy you could be Generating per year !

To Generate 60% more energy per Year, you simply install a Dual Axis-solar Radiation Tracker (DART), that follows the Sun from as earl as 5:30AM to 8:00PM, depending on your Latitude.
Where the Further South or North of the Equator, a DART unit Generates Energy for a longer time.
NB: Radiation Tracking is Superior than either GPS or Time Tracking, as in Cloudy periods, they point the solar panels to Dark Clouds covering the Sun, whilst Radiation Tracking will rotate the solar panels to the Brightest area of the Sky.

Yes, DART units have a Higher upfront Cost, however, the Additional Energy is Generated using approx. Half the Solar panels for the next 30+ years.
DART units are commonly mounted on a Pole, buried in the Ground, and have a wind sensor to lay the Racking Horizontal in Hi-winds.


If purchasing Bi-facial solar panels, make sure they are Double Glazed, as they are not only Stronger, they also dissipate Heat better.
And for those wanting to Generate as much Energy as Possible from the Rear of the solar panels, you can cover the ground with White Stones or anything that is a White or Silver material, as that in a perfect situation will Generate up to 30% more Energy from the reflections.

Dennis Mono wrote:All this conversation is missing one important point;

If the Solar Panels are NOT perpendicular to the Sun, you are loosing up to 60% of the Energy you could be Generating per year !

To Generate 60% more energy per Year, you simply install a Dual Axis-solar Radiation Tracker (DART), that follows the Sun from as earl as 5:30AM to 8:00PM, depending on your Latitude.
Where the Further South or North of the Equator, a DART unit Generates Energy for a longer time.
NB: Radiation Tracking is Superior that either GPS or Time Tracking, as in Cloudy periods, points the solar panels to Dark Clouds covering the Sun, whilst Radiation Tracking will rotate the solar panels to the Brightest area of the Sky.

Yes, DART units have a Higher upfront Cost, however, the Additional Energy is Generated using approx. Half the Solar panels for the next 30+ years.
DART units are commonly mounted on a Pole, buried in the Ground, and have a wind sensor to lay the Racking Horizontal in Hi-winds.


If purchasing Bi-facial solar panels, make sure they are Double Glazed, as they are not only Stronger, they also dissipate Heat better.
And for those wanting to Generate as much Energy as Possible from the Rear of the solar panels, you can cover the ground with White Stones or anything that is a White or Silver material, as that in a perfect situation will Generate up to 30% more Energy from the reflections.

All the research I have seen claims a 30 percent increase for dual axle trackers. They have lost favour here due to their high maintenance requirements. I do live at 45 degrees so that is a huge ark in summer and challenging temperatures swings in the winter so it pushes the mechanisms hard. If you are the type of person who can change a control board, a dead sensor and an actuator you stand to gain some production. If you have to call in a technician every time a component acts up then no.  For my thinking  A good portion can be made up with a manual seasonally adjusted array angle. For the rest add panels which are cheap and do not require any maintenance. Installed once and maintenance free (or virtually) operation for its life span. Its a case by case thing though.
Cheers,  David B.

Dennis Mono wrote:...To Generate 60% more energy per Year, you simply install a Dual Axis-solar Radiation Tracker (DART), that follows the Sun from as earl as 5:30AM to 8:00PM, depending on your Latitude.

I can see something like this if space is really limited. What I see in my area, is that now that panels are relatively cheap, they just put them on different angled/direction roof surfaces, so that they cover more times of the day and year.

As David B said: "Installed once and maintenance free (or virtually) operation for its life span." In our wet and occasionally windy environment, I can't imagine a tracker like that not running into maintenance issues.

David Baillie wrote:
All the research I have seen claims a 30 percent increase for dual axle trackers. They have lost favour here due to their high maintenance requirements.
I do live at 45 degrees so that is a huge ark in summer and challenging temperatures swings in the winter so it pushes the mechanisms hard. If you are the type of person who can change a control board, a dead sensor and an actuator you stand to gain some production. If you have to call in a technician every time a component acts up then no.  For my thinking  A good portion can be made up with a manual seasonally adjusted array angle. For the rest add panels which are cheap and do not require any maintenance. Installed once and maintenance free (or virtually) operation for its life span. Its a case by case thing though.
Cheers,  David B.

The most Common problems we have encountered with Old designed Dual Axis Tracking (DAT) systems in Australia are;

1) Cheap Linear Actuators fail at around 10 years, these were mostly 12V Actuators, that did not have an External Motor &/or used Plastic Gears !
Solution: Use 24V Double Slew Drives, as these will commonly outlast your lifespan, as they move slowly, and will Not wear out the internal metal Gears.

2) The other Common Failure is the DAT Controller that use Relays may/will Fail at around 4 years, Relays can burnout & either Not work, or get locked on & damage the Racking or wiring.
Solution: Use a Controller that uses Automotive Mosfets, these are superior to cheaper Relays.

3) Many old DAT units did Not use an Anemometer (Wind Sensor) , that automatically Lays the Racking Horizontal (Flat), to avoid Damage to the Racking & solar panels !
Solution: Fit either a Digital or Analogue Wind sensor.

4) Analogue Stop Sensors can Fail like Relays, especially if Not Water proof !
Solution: Fit Magnetic Stop Sensors, and Silicon over the connectors, to better weatherproof the switches.

5) GPS or Time Tracking is Inferior to Radiation (Light) Tracking !
Solution: Purchase a 4 Direction Light sensor that uses 4 miniature solar Cells, NOT the LED light sensors, as they are inferior when it comes to Accuracy.

That pretty well cover what to avoid when purchasing a DAT unit.

We have only found One Hi-Quality DART Controller, it is a Polish Made REI DART Controller.
https://www.micropowergrids.com.au/_Wiring_and_Equipment/DART_Controllers/_Light_Sensor_DART_Controller_Module_type-1.html

Dennis Mono wrote:

David Baillie wrote:
All the research I have seen claims a 30 percent increase for dual axle trackers. They have lost favour here due to their high maintenance requirements.
I do live at 45 degrees so that is a huge ark in summer and challenging temperatures swings in the winter so it pushes the mechanisms hard. If you are the type of person who can change a control board, a dead sensor and an actuator you stand to gain some production. If you have to call in a technician every time a component acts up then no.  For my thinking  A good portion can be made up with a manual seasonally adjusted array angle. For the rest add panels which are cheap and do not require any maintenance. Installed once and maintenance free (or virtually) operation for its life span. Its a case by case thing though.
Cheers,  David B.

The most Common problems we have encountered with Old designed Dual Axis Tracking (DAT) systems in Australia are;

1) Cheap Linear Actuators fail at around 10 years, these were mostly 12V Actuators, that did not have an External Motor &/or used Plastic Gears !
Solution: Use 24V Double Slew Drives, as these will commonly outlast your lifespan, as they move slowly, and will Not wear out the internal metal Gears.

2) The other Common Failure is the DAT Controller that use Relays may/will Fail at around 4 years, Relays can burnout & either Not work, or get locked on & damage the Racking or wiring.
Solution: Use a Controller that uses Automotive Mosfets, these are superior to cheaper Relays.

3) Many old DAT units did Not use an Anemometer (Wind Sensor) , that automatically Lays the Racking Horizontal (Flat), to avoid Damage to the Racking & solar panels !
Solution: Fit either a Digital or Analogue Wind sensor.

4) Analogue Stop Sensors can Fail like Relays, especially if Not Water proof !
Solution: Fit Magnetic Stop Sensors, and Silicon over the connectors, to better weatherproof the switches.

5) GPS or Time Tracking is Inferior to Radiation (Light) Tracking !
Solution: Purchase a 4 Direction Light sensor that uses 4 miniature solar Cells, NOT the LED light sensors, as they are inferior when it comes to Accuracy.

That pretty well cover what to avoid when purchasing a DAT unit.

We have only found One Hi-Quality DART Controller, it is a Polish Made REI DART Controller.
https://www.micropowergrids.com.au/_Wiring_and_Equipment/DART_Controllers/_Light_Sensor_DART_Controller_Module_type-1.html

Dennis, The link kind of reinforces what I said above. It makes sense to me and I can admire the tech (but distrust their 60% figure) while not being willing to commit to it. If the system was for me and I had a single smaller array due to lot size or solar availability I would consider it. For my clients? Nope.  As an installer I can tell you it rings all kinds of service technician alarm bells in my head. Cost per hour to have someone like me out to site is free for the first year , $75 per hour after that if I installed the system, $100 plus if someone else did. The clock starts when I leave home. Off grid arrays are generally in remote areas which means said technician will be traveling for hours. If you are lucky you bring all the parts with you and can diagnose and fix it in one shot. In reality nobody has all the right parts. So second trip with more travel time. You end up trying to present a $1000 bill for a $100 part replacement. So that in a nutshell is why the larger array that does not move is generally preferred.  There is a lack of qualified technicians out there for everything mechanical electrical electronic. I try to simplify and keep my systems as resilient as possible. Its a design philosophy at the end of the day.
Cheers,  David  

David Baillie wrote:
Dennis, The link kind of reinforces what I said above. It makes sense to me and I can admire the tech (but distrust their 60% figure) while not being willing to commit to it. If the system was for me and I had a single smaller array due to lot size or solar availability I would consider it. For my clients? Nope.  

As an installer I can tell you it rings all kinds of service technician alarm bells in my head. Cost per hour to have someone like me out to site is free for the first year , $75 per hour after that if I installed the system, $100 plus if someone else did. The clock starts when I leave home. Off grid arrays are generally in remote areas which means said technician will be traveling for hours. If you are lucky you bring all the parts with you and can diagnose and fix it in one shot. In reality nobody has all the right parts. So second trip with more travel time. You end up trying to present a $1000 bill for a $100 part replacement. So that in a nutshell is why the larger array that does not move is generally preferred.  There is a lack of qualified technicians out there for everything mechanical electrical electronic. I try to simplify and keep my systems as resilient as possible. Its a design philosophy at the end of the day.
Cheers,  David  

Hi David,
The 30% increase is based on Fixed Panels Generation, and comparing Generation using either GPS & Time Tracking, Both inferior to Radiation (Light) Tracking !
However, I should have said; Up to 60% increase in Energy Generation over 12 months !
The 60% figure would be in a perfect situation, and obviously a lot Further away from Equator the better the results.

As for Servicing, DAT or DART units, Yes Cheap Equipment is what causes the reluctance to install them, as well as the Installation of a Foundation needs a Hole dug in the Ground, and Trenching to where the Batteries & Inverter are installed...  Thus requiring an Excavator to save the Manual work.
The problems that can occur, is if the Wires coming from the Light sensor is Not protected for the first few cm, we have had two cases where Galahs or Cockatoos have Chewed the wires, but that only stops the Racking from Tracking, until repaired.

There are DART units that can be Installed without a Foundation, and can be fitted atop a Shipping Container, of bolted to a Concrete slab or Flat Roof.
https://www.micropowergrids.com.au/_SOLAR_GENERATION/1.DART_Commercial/03.DART-4/001.ROOF_DART-4.html

However, I do understand your concern, and DART's are Not for everyone, and largely a lot of Older people go for them, as they are a lot easier to Clean the solar panels, than climbing on the Roof.

There is so much BS about OFF-Grid & ON-Grid, as ALL Solar ...inc. Battery Systems are Installed Behind the Grid (Meter Box), so logically they are all OFF-Grid.
The only difference is that OFF-Grid inverters don't have Islanding Protection !
Making it Smarter to install an ON-Grid inverter that have Anti-Islanding relay protection, then the Customer has the option to use the Grid to Charge the System, or use a Generator !

Cheers Den.

Jay Angler wrote:

Dennis Mono wrote:...To Generate 60% more energy per Year, you simply install a Dual Axis-solar Radiation Tracker (DART), that follows the Sun from as earl as 5:30AM to 8:00PM, depending on your Latitude.

I can see something like this if space is really limited. What I see in my area, is that now that panels are relatively cheap, they just put them on different angled/direction roof surfaces, so that they cover more times of the day and year.

As David B said: "Installed once and maintenance free (or virtually) operation for its life span." In our wet and occasionally windy environment, I can't imagine a tracker like that not running into maintenance issues.

Hi Jay,
95% of Customers are Rural, and install there System themselves, as most Farmers have Equipment & are relatively Smart, DART unit is a large Meccano set, and only engage an Electrician to Wire up the Inverter & PV wiring.

There are a Lot of Shonky DAT Manufacturers out there, flogging Outdated Equipment, and that is what causes major issues & breakdowns, Using cheap DAT Controllers & Linear Actuators is the Cause of most problems.
You only get what you pay for.
Thanks for your input.
Cheers Den.