Is it worth changing the angle of the panels ?

[WoodsieLord]

I'm having discussions in my head regarding how many watts would I gain if I put my panels in the correct angle.
I have 6 panels on a 10th floor roof that has lots of wind. I went with the simplest and safest approach and made an horizontal structure. Panels are 100% horizontal.

They produce 1500W in summer and 800W at most in winter (usually less). I'm trying to guess what the benefit would be if I set the panels in the correct angle for winter.

I already know the ideal angles, what I would like to know is what kind of improvement would I get if I did it.
I'm having doubts. A given surface placed at 54º would cast the greatest shadow. Does that mean that "to catch the same amount of sunlight" with an horizontal surface I would need it to be as big as the shadow cast at 54º ?

That makes me jump into the conclusion:
2m horizontal panels produce 800W, if I were to shift them to 54º they would produce a whopping 174% ? It has to be wrong... right??

Thanks in advance!

 

[Maitake]

A steeper angle will cast a shadow on the panels behind. For max solar flat roof production per area, shallow angles and close spacing is best.
For max production per panel higher angle and much greater spacing is "best".
There are software solutions out there for this. Free SAM (system advisor module) might do it, I didn't mess with that portion of the program.
Pvwatts I think does it with a spacing coefficient, sorry I don't have details... hope this helps

 

[Bluedog225]

I agree this site is great. You can use defaults for most stuff to keep from getting bogged down.

Just change the angle and look at the totals.

Somewhere in there it outputs hourly production if you want that level of detail.

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

 

[ncsolarelectric]

In NC, the difference between a perfect tilt and 0-deg tilt is only 9%. The difference between an ideal 30-deg tilt and a 20-deg is 0.7%. Not really worth changing tilt, IMO. Less tilt is cheaper and easier to build if you have a windy backyard like me. I went with the 10-deg ballast mount. A 30-deg tilt ground mount would need to withstand hurricane-force winds 115 MPH around here and I have no wind blocks from the north.

 

[WoodsieLord]

Thanks for the replies !

I tried the PVWatts thingy. I used the actual position with an approximated array size. Then run the same test changing the tilt. Here are the results. The annual production is not important as the calculator is probably assuming I would stick with the angle the whole year.

Take into consideration that I'm in the southern hemisphere (you'll probably guess that by the numbers anyway)

Predictions:
May 32% increase.
June 45% increase.
July 40% increase.
August 20% increase.

Those are actually pretty good numbers. Although, spacing and shadows are probably not taken into consideration...
Thanks again

 

[Danke]

I wanted a steeper angle until NC showed how much shadowing would mean with spacing vs. more panels with less angle in total system production.

I have a flat roof, so limited on area. I’m at 45N and get snow. My compromise (I think) will be 15 tilt and about 18” spacing between rolls.

 

[WoodsieLord]

I only have 6 panels. Perhaps I could arrange 3 horizontals and 3 tilted. That way I could put the horizontal string "first" and no panels would get shaded by other panels. Not easy though

 

[Bluedog225]

Where are you?

 

[WoodsieLord]

Argentina, Buenos Aires

 

[Bluedog225]

Ah. That explains it.

 

[RCinFLA]

At -34.6 degs latitude, Buenos Aires is about the same as Little Rock, Arkansas, just directed north instead of south.

This data has some effects of local weather but should be close. Also need to flip months so December is June on chart

.

 

[Danke]

Optimum Tilt of Solar Panels