Solar Panel Tilting Consideration?

[ftrv8]

Hello,

I am considering getting more juice out of my system by maybe tilting the left bank of my panels on the west side of my home. Any thoughts, advice or has anyone done this?

In the picture you can see the current tilt of the panels. The house is two story and very rectangular (damn zero lot homes). Due to vents and all the code I’ve fit as many panels as possible. From the diagram picture you can see the south panels are worth their weight in gold on production, hence my itch to tilt.

TIA and please let me know any other info I should provide. Location is Central Valley, CA.

 

[jrweiss98020]

I would check with an installer. A DIY rig would likely violate some code or another, and possibly be torn up by wind.

 

[ftrv8]

I would check with an installer. A DIY rig would likely violate some code or another, and possibly be torn up by wind.

You are right. Forgot about the wind factor. Gets extremely windy where I live.

 

[Vines]

Tilting will be unlikely to generate much more power. Certainly not enough to be worth it.

Fire codes have changed over the last 2 years, see if more will fit.

What does your roof look like from satellite pics?

 

[wwhitney]

The time and money spent on implementing tilting could be more rewardingly spent moving the roof vents around as required to add more panels.

Cheers, Wayne

 

[jboy210]

You are right. Forgot about the wind factor. Gets extremely windy where I live.

Room for a backyard windmill? After all, you are right below all those windmills up on the Altamont pass. Home of the first large-scale commercial windfarms in the US.

We had a property in Mountain House and I was always surprised how windy it gets east of the Altamont.

 

[DrSmile]

I have a very flat roof pitch (20 degrees, one section even less) and my production is indeed very low in December / January, but by the middle of February I make enough peak power to clip the inverter, so I don't really think tilting the panels makes sense unless you live really far North (like Canada). I'm near NYC so further North than even Northern California. I was amazed how little overall difference orientation and azimuth actually makes in yearly production on the prediction calculators.

 

[wwhitney]

I was amazed how little overall difference orientation and azimuth actually makes in yearly production on the prediction calculators.

If you are comfortable with vectors, then one way to think about the geometry only (Ignoring atmospheric effects like weather and low angle effects like terrain), one way to think about it is like this:

The path of the sun on any given day describes an arc through the above grade hemisphere. The optimal fixed direction to point your solar panels that day would be at the center of mass of that arc, which will be towards the equator at some elevation angle. If your panels are pointed at a different angle, your production for the day will be reduced by a factor equal to the cosine of the angle between the actual panel normal and the center of mass of the sun arc (assuming you're not so far off that the sun is sometimes behind your panel).

Then on days closer to the summer solstice, the sun will be higher in the sky much of the day, and the optimal elevation angle will be higher. If you average all those elevation angles over the year, weighting each one by the length of the day, you'd get the optimal elevation angle to maximize production for the year (if that's your goal, vs say maximizing the minimum daily production for off-grid use, or maximizing your production during peak TOU hours, etc).

And again, if your actual panel normal is pointed in a different direction, you just take the cosine of the angle between due south at the optimal elevation, and your actual panel normal. For small angles cosine is still near 1, e.g. if you were off 30 degrees (your panels normal is 70 degrees above the horizon (20 degree roof slope) instead of, say, an optimal 40 degrees), cos(30 deg) = 0.866, and you lose about 14% off your annual production.

Cheers, Wayne

 

[ftrv8]

Tilting will be unlikely to generate much more power. Certainly not enough to be worth it.

Fire codes have changed over the last 2 years, see if more will fit.

What does your roof look like from satellite pics?

 

[jboy210]

Looks like you have a lot of planes on the roof. I am not sure if there are still enforcing it, but were/are offsets from where planes meet.

 

[wwhitney]

I am not sure if there are still enforcing it, but were/are offsets from where planes meet.

FYI, the current CA rules on roof top layout for detached single family homes is here:

https://up.codes/viewer/california/irc-2018/chapter/3/building-planning#R324.6

Cheers, Wayne

 

[Vines]

The current codes do not require setbacks where every roof planes meet, and in most cases you can be just 18" down from the ridge.

Local AHJ sometimes try to home rule this but most follow the code.

Your roof is very broken up and the northwest face is the largest unbroken area, though it's not an amazing azimuth especially in winter there may be very little production on those panels. If the roof slope is 4:12 or 3:12 it's not terrible especially if you are on a TOU type rate structure. Sometimes those 2-3 hours of afternoon summer sun at peak TOU rates can make up several hours of midday production since they are credited back at 2-3 times normal rates.

 

[GWord]

How much more production are you looking for? Relocation of the vents to add another few panels might be something to consider versus alternatives.

 

[Sylvia Else]

Hello,

I am considering getting more juice out of my system by maybe tilting the left bank of my panels on the west side of my home. Any thoughts, advice or has anyone done this?

In the picture you can see the current tilt of the panels. The house is two story and very rectangular (damn zero lot homes). Due to vents and all the code I’ve fit as many panels as possible. From the diagram picture you can see the south panels are worth their weight in gold on production, hence my itch to tilt.

TIA and please let me know any other info I should provide. Location is Central Valley, CA.

I don't know that this is at all practical. At your lattitude, even in mid summer and at midday the sun is not overhead. So you have to consider the problem of one panel shading the next one. The situation gets worse the nearer the season is to winter, in either direction.