Measuring The Impact Of Solar Panel Tilt Angle
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- เผยแพร่เมื่อ 12 ก.ย. 2023
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So how much impact does the mounting angle actually make on the power output from your solar panels? Online you will find a few percentage ranges but I wanted to compare a flat roof to my pitched roof angle to make a smart decision on a future project I have at my house. You might be surprised by the results.
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Here in Southern Australia seems best angle is to maximise sun when its low in the sky and days are short. Around summer when the sun is high and days are longer, the panels are saturated and also get extremely hot, so the tilt makes no difference, and may actually keep the panels slightly cooler by reflecting some sun..
Very interesting approach. Makes perfect sense, since the low light hours are usually wasted, and you are correct, the excessive heat is detrimental to longevity and output.👍
there should be additional heat loss on the flat panels from this testing setup. I would have tested those flat panels elevated about an inch or two off the concrete to allow for normal airflow under the panel, that way this test shows only the losses attributed to angle and not angle plus the extra heat being held under the flats. a lot of roof mounting hardware has panels elevated an inch or two even when flat
Fair point, thanks for the feedback.
I was thinking the same thing. That concrete has to be getting some heat even in September.
Those angles, in the link, are what I was searching for. Thanks!
You bet!
Thank you so much... the website enabled me to know how much I will need to tilt my panels in Norway, Senja island. I am building my tilting PV rooftop of 1000W for my Camper van... I will need to tilt up to 57°...
Best of luck on your project!
It’s fairly simple in concept. The efficiency of the panels is proportional to the cosine of the angle between the direction of the Sun and a perpendicular from the face of the panel. So, for example, 30 degree difference (cos(30) = 0.87) will give about a 13 percent reduction in power compared to a 0 degree angle. The angle between the panel and Sun will be very high in the morning and evening and smallest at midday provided your panels orient south or north depending which hemisphere you are in. Since you might want to maximise power in winter you could argue that pointing the panel directly at the Sun for its midday middle of winter direction would minimise the seasonal power generation but not necessarily get overall maximum annual power generation. (If you live too far north/south that might not be a good strategy!)
I am sure there are web based power estimators which will graph power for specified panel orientations.
Great video & angle tips!
Thanks!
In MA 25 degrees is standard for the large commercial solar sites you see. They are figured for 7 months of good exposure. The other 5 months are bonus.
Great video and test. I always wonder how the angle of the panels would effect efficiency. I have 2 sections of my roof that are at different pitch. In my home solar install, my installer never mentioned the pitch of my roofs. I just wonder if they took the pitch in determining how much my energy my system would produce.
The calculator website, are the angle numbers facing south? What if I want to face west, should I use the same angle? Can you please make a video on how to actually find the horizontal or vertical and what device do you recommend to use. Thank you for all your videos.
You need to consider both angle and tilt. In general in the US you want panels facing true south not magnetic south and for a fixed mount most systems are angled to get the most sunshine in winter when the sun is lower and you get shorter sunlight hours. You can use that footprint website to determine both based on your geographic location.
For a roof mount system you generally have little choice unless your house was designed specifically for solar and you are stuck with whatever angle and tilt your home roof was built at unless you want to pay for expensive adjustable roof racks.
That is why I recommend ground mount with an adjustable angle so you can maximize your solar angle for both summer and winter use. You can use a much smaller system that way and maintenance is also much safer and easier on a ground mount.
By having the proper angle and tilt and ability to adjust for seasons you can use a ground mount system about half the size of most roof mounted systems.
Added: You also do not want panels mounted flat on any surface as they require air flow to remove heat behind the panels and heat is what reduces output and causes cells to fail early.
Yeah, if I had the room and no HOA I would 💯 go ground mount. My first mistake was being in an HOA 😂. We will be doing some small ground mount on the EG4 mounts in the coming months.
I have panels on a pergola
They are flat so they are not visible by anyone snooping.
In arizona the sun is pretty directly overhead in the summer. So it works.
If i could i would have them on a adjustable mount to tilt from dusk until dawn.
But that dont work for my low profile setup.
THANKS SCOTT 🤗💚💚💚
You bet 🙌
Good apples to apples test. I did a similar thing we an RV, the panels were not the same manufacturer nor power rating. Over a period of weeks, it measured out to be 20-30%. I even rotated the angled panels 3 times a day to see how much it mattered. The improvement of rotating did not have a large impact. Setting for peak hours and forget is much easier.
Thanks so much for the feedback!
Is there a calculator that takes into account the seasonal changes in cloud cover? Depending upon the weather over the year, there may be more optimal times to maximize the output. There's also a difference bewteen grid-tied / net metering and off grid. If you're on net metering, you'll want to maximize total output over the year. If you're off-grid, you may want to maximize output when you need it most.
If you plug both groups together would the flat mounted panels affect the out put drastically or just a little bit
Wont the flat panels perform better in the mornings and evenings?
What is then the total loss during a summer day?
I'm in NW WI and the referenced site give very different angles that other sites. Every site provides different results.
Since its heading towards fall i have to angle my panels at around 1 pm i can get about 30 - 50 watts more at the right angle vs laying the flat which i do in the morning up until about 12 noon So angling makes a difference.
Good info!
Thanks for the feedback 👍
Panels are cheap. I’d rather not see the panels and buy a few extra than look at them
I noticed the angled panels were exposed to the sun and warming up prior to testing while the flat ones were not. This makes for an unreliable test
You forgot a few things. Aiming partly east and west increases the duration of the charge and this is very important when your batteries are a small part of your solar plant. Aluminum wire can be used outdoors, even if it's considered an indoor hazard. Aluminum wire can be very thick. Panels don't have to go directly on a roof. They can go on subframes or mini towers in different parts of your property.
Scott, if you live in the Snowbelt (I think you may) your pergola better not have solar panels on it in the winter, the snow load could be several thousand pounds.
Each day we get closer to trackers 😄
Being on a pergola, it should stay cooler, as it will have airflow underneath, which should increase your output
Important not to trap heat under panel. You should have raised the flat panels to get airflow under. Try that and get new readings
but heat makes loss & flat ones were not vented under? so loss can be pitch & heat buildup?
👍👌❤️🇨🇦, I get about 30% more if the panels are tilted compared to laying horizontal, but this also depends on the latitude I am at, and the season,
Thanks for the additional data point!
Although both panels, readers and storage units are made by the same manufacturer, assuming they are identical in performance could seriously skew your result. Performing the same experiment again, swapping the panels over and averaging the result would mitigate this.
Thanks for the feedback!
Good to buy smaller panels and do these tests before making a big investment. Can always use those panels for extra power during emergencies or for camping.
Where do you buy the rc power analyzers that come with mc4 connector?
Most of them don't come with the MC4 connectors standard so I just bought this inexpensive crimping kit amzn.to/3Fl1mzE
I would think that for lower vs higher angle for seasonal, if you are in a cold climate, I would air toward steeper angle, so that you use most of the power for heating, vs if you use more power for AC in the summer, then targeting the lower angle might be best.
I know in my case, 11kW is way oversized for summer (50kWh/day in peaks) but way under sized for winter (150kWh/day in peaks), so if I went solar, I would want to optimize for winter
how is your winter power so high? are you using resistance heating im in pa and summer is twice as much electricity in summer.
it's called living in a cold climate ;) PA is not cold climate@@ranger178
We can get as low as -40 here (these are the days where I can reach 150 kWh/day).
If you're panels are on the roof, you're going to be clearing them quite a few times during the winter, so be prepared.
As the cost of the panels themselves continues to fall, what we see is that the cost of the mounting system now actually starts to make up a significant proportion of the overall spend. As a result, cheap mounting often outways "optimum capture" mounting when you look at the payback! This is particularly the case when you look at panels mounted on high roofs that now drive a large installation labour costs.
outways?
Would their be an way to change the pitch angle though out the year to get the best angle though out the year?
This is most commonly accomplished with ground mount that has an easy adjustment built into the design. For those of us with roof mounted on standard racking the adjustment would be a no go.
Tilting is more critical in the colder months, when the sun is low. I have 11 panels mounted almost flat, they reached a peak of 1600 watts (today October), the other 9 panels titled perfectly at 35 degrees, reached a peak of 2200 Watts, so the difference is huge, and that translates to a %40 loss only during that specific peak hour. If my flat mounted panels were at the same angle, they should have reached a peak of 2700 Watts instead of 1600 Watts. My conclusion for you is to mount your panels at an angle, especially if you are off grid because you want to maximize production during Fall and winter, that is when you will need it the most, in the summer you have longer days and plenty of sun
In theory, I should have panels set to 30 degrees - better facing the average height of the Sun and dramatically better situation when there is snow.
However, I have them on my roof (I have a house with almost flat roof, anout 3-4 degrees) and I decided to fill the roof with panels lying flat.
Why?
Because, raised panels cast shadows - and I would have to move them away from each other. That would limit the number of panels by much more than I would gain from the tilt! And during the summer, the profit from steeper angle isn't that spectacular.
I have an issue in that I have a room extensions which impact the roof making it flat or just a few inches below the existing ridge. According to the local regs I cannot put anything on the roof that is above the ridge. I have had a survey done and the installer will not fit solar panels so DIY is my only option.
I was wondering that the two setup was placed to close to each other and at 6:50, I noticed the flat panel is partially shaded by the tilted panel
And wired in series, a little bit of shade really affect the whole string
in having panels flat on a surface the heat buildup trapped between the panel and the surface underneath cannot escape and will effect the performance as well
Yeah, good point. would have been nice to space them off the concrete to give some air movement/heat transfer. Thanks for the feedback.
I'm in Central Alabama and have the same panels. Can you think of some trouble shooting reasons for why I have never gotten over 75w per panel, even when less than a few weeks old?
Really, man I have really good luck with these thunderbolts. Facing south at a 30 degree angle on a sunny day I have seen as high as 105 Watts. Could you test each one individually? If you have one panel in a series string it might be bringing all of them down.
@everydaysolar-ps3xg I figured it out. I'm using one of those 4:1 connectors and the Ecoflow Delta 2 Max is limiting the input to 15 Amps. That's why I'm not able to get 100% of the input.
Each panel has a max Amp output of 5.56, and the connector is combining them in parallel.
I noticed shade (reflection) cast from your angled panels on the flat panels. Perhaps of you had them switched
It was close and that is what actually set the end of the test. The last part of the video you could see a shadow but that was after the readings were taken for the test. Thanks for the feedback.
Nice test, but it should be tested over 24 hours instead of two hours.
Yeah, a dawn to dusk would be interesting. I need better data collection equipment so I can over plot each power output curve. Thanks for the feedback.
I question how valid the tests are because at 6:47 you can see the inclined panels are casting a shadow on the flat panels
He comments elsewhere that he stopped the test before the shadow began to interfere. It's also not doing it yet at 5:26.
👍👌❤️🇨🇦, I use my latitude as a reference for fing the correct angle, but I tap the top off of a paint spray can, I place the plastic lid in the corner of the panel, with the panels facing solar south, not magnetic south, as you raise and lower the solar panel, look st the spray paint lid and notice the shadow ring around the base of the lid, when you have the best angle the shadow will be even around the lid, and the shadow will be very close to the bottom of the lid, I have used this method for 23 years on my 36 x 405 watt solar array, simple and fast, no need for an angle finder using my phone app
Nice little method for finding the exact angle where the panel is perpendicular to the sun. I like it 👍
Or in finding the correct, just try it on your tilted panels, it is fast and simple
I belive this video is about altitude (up/down). What about azimuth (left/right)?
Yeah, I want to do a North, South, East, and West comparison showing the difference in output but at this time I am short on a few components to run that all on the same day. Thanks for the feedback.
Why not just use PVwatts - works for anyplace in the world. It gives you month by month output for any tilt you want to put in. In my experience it is very accurate - developed by NREL.
Yeah, I should point people to pvwatts as it is a great tool. This video is a little more focused on introducing people to the importance of tilt angle in general through a simple test. Thanks for the feedback.
i would want to know for fence mount how bad is it
Are you planning on just installing the panels vertically on the fence?
Each solution has cons and pros and will vary depending on your location.
Where did you get the RC panel analyzers? 1:49
You can grab a few on Amazon amzn.to/46g8ecP
@@everydaysolar Thanks Scott, I'm a big fan of your channel.
You got shadow created on flat panel from the tilted panels.... That's your loss...!
Actually, that was one of the factors I was monitoring. I stopped the test at the 2-hour mark as we were right on the edge of the tilted panels casting a shadow on the flat panels. So, for this test that would not be associated to the loss.
They say some models, refractive structure, get the same power from low angles
Really 🤔
A good start, but really means nothing, you would need to run the test in an unshaded location for a year, so you get all sun elevations. I get the feeling if you just can it for a day you would get a better result.
Instead of confusing the viewers with the angle calculator. A simple soup can trick would work anywhere in the world. 😂
Your results were significantly skewed because the heat buildup from the flat panels laying directly on the also hot concrete. That increased heat will drastically lower performance. To make this a better comparison you probably should've elevated those flat panels 4"-6" like they would be for a typical roof mount. You can also save the testing effort and just model the difference in PV Watts... great tool and pretty damn accurate!
Thanks for the feedback 👍
👍
E~cos(angle), where 0 degree is panel directly facing Sun
You know what I've got the 250 what what's a leg standing on the ground from 11 to 4 p.m. charging my two lead carbon batteries 100 amp hours no charge controller connected directly to the batteries it pushes out between 8 and 9 amps facing the sun I follow the sun and the sun's angle and move the panels every 2 hours the batteries are 12 volt batteries the solar panel pushes out between 21 and 27 volts. Angle and facing the sun really matters a lot.
It is almost 24% from going Flat to (proper) Angle.
The panels at an angle will have great resistance in high winds ..it will basically act like a sail. I will take the power loss for some piece of mind when they are installed flat.
Results at 5:54
Well, the calculation shouldn't be based on the angle of the panel - but the angle of the sun vs the panel.
jump 6:02
4:52 Squirrel
😂
1) The RC gauges aren't all 100% the same and not reliable. Huge deviations between them.
2) This test is only for 2h not a whole day. The angled panel produces less @ dawn-dusk.
The angled panel shall collect less dirt and rain cleans them more easily but that wasn't the test.
Yes, tilt angel, if not, it's pointless
its not the angle in your case its the temperature
not trying to drop a turd in your punchbowl but at the end of your video it looks like the tilted panels shadowed the flat ones...
I'm sorry to tell you but your test is flawed.
Thanks for the feedback
Just talk too much. Didn't watch it all so missed the bit of whether it's beneficial or not