Seeking rail system for a roof mount system that allows angle adjustment

[Testshoot]

Why are you wanting to tilt them? You cant adjust the spacing so you will have to go with max spacing. Also most modern pv modules have a much wider angle of incidence so tilting is of less difference for productioon but great difference for loading

I don't claim to be an expert on the subject, I am just a newbie, but having spent a LOT of time researching this large purchase, I found multiple sites suggesting tilting to get optimum performance. The site referred to most is: http://www.solarpaneltilt.com/optsolar.html

% of optimum

71.1%

75.2%

75.7%

Yes, only a difference of 4%...this first figure is fixed position, second is 2 positions, third is 4 positions. Hardly any difference between two and four position, but is it worth 4% more performance to go on the roof twice a rear and change the angle, maybe not. However, keep in mind, that to even get the 71% optimum, for me, that is an angle of 29 degrees and the roof is 18 so I am already 11 degrees off of optimum.

optsolargraph.jpg

I too found the info on the Unitrac site, but it seems their solution is more about setting the initial angle. If you use the legs to get a high angle for winter, you can't lower the legs for summer as they don't collapse much, i.e. less than half their height. So you would either need to remove the legs and drop the panels down or do without.

Their solution is in this PDF: https://unirac.com/wp-content/upload..._Final_221.pdf

I found this comparison chart for various racking options:

https://www.civicsolar.com/support/installer/articles/solar-pv-racking-options-comparison-chart

They mention the Unitrac option and they mention an IronRidge option, but I am guessing they are for initial installs to get the best optimum single position angles.

For my latitude, I am supposed to go from 12 degrees summer to 50 degrees winter. To get to 12 degrees, I would have to raise the bottom mounts to get from 18 to 12, and then be able to go up from there to 50.

The adjustable leg mounts allow you to move the vertical legs back and forth to truly be able to adjust them. The ones I was referred to were all made for light weight, small size panels.

Seems the same mechanism that are used for the tracking systems could be used on the roof, even if I wasn't tracking, only tilting.

I am luck to have a lot of open roof at an azimuth of 189 so I am pretty close to the ideal south facing setting.

Thanks..

[Mike90250]

I just wrote a detailed explanation siting my sources with graphics and the post disappeared....either their is a grinch or the links and jpg killed it...dunno, but I have learned what I need to so thanks to those who offered constructive help.

it was too many links, approved now.

for 4%, I'd not bother with adjustments.

[Testshoot]

it was too many links, approved now.

for 4%, I'd not bother with adjustments.

Thanks for your feedback....Keep in mind that to get to get to the optimum year around setting I have to change it 11 degrees, unless I want to leave it flatter which would make the summer angle better which probably isn't bad as that is highest usage.

Thanks

[Mike90250]

For 11 deg, I'd still not bother with changing it. bolt it on, and forget about it. Just hose off the droppings in the early morning while the dew is still wet and the panels cold.

[J.P.M.]

I don't claim to be an expert on the subject, I am just a newbie, but having spent a LOT of time researching this large purchase, I found multiple sites suggesting tilting to get optimum performance. The site referred to most is: http://www.solarpaneltilt.com/optsolar.html

% of optimum

71.1%

75.2%

75.7%

Yes, only a difference of 4%...this first figure is fixed position, second is 2 positions, third is 4 positions. Hardly any difference between two and four position, but is it worth 4% more performance to go on the roof twice a rear and change the angle, maybe not. However, keep in mind, that to even get the 71% optimum, for me, that is an angle of 29 degrees and the roof is 18 so I am already 11 degrees off of optimum.

optsolargraph.jpg

I too found the info on the Unitrac site, but it seems their solution is more about setting the initial angle. If you use the legs to get a high angle for winter, you can't lower the legs for summer as they don't collapse much, i.e. less than half their height. So you would either need to remove the legs and drop the panels down or do without.

Their solution is in this PDF: https://unirac.com/wp-content/upload..._Final_221.pdf

I found this comparison chart for various racking options:

https://www.civicsolar.com/support/installer/articles/solar-pv-racking-options-comparison-chart

They mention the Unitrac option and they mention an IronRidge option, but I am guessing they are for initial installs to get the best optimum single position angles.

For my latitude, I am supposed to go from 12 degrees summer to 50 degrees winter. To get to 12 degrees, I would have to raise the bottom mounts to get from 18 to 12, and then be able to go up from there to 50.

The adjustable leg mounts allow you to move the vertical legs back and forth to truly be able to adjust them. The ones I was referred to were all made for light weight, small size panels.

Seems the same mechanism that are used for the tracking systems could be used on the roof, even if I wasn't tracking, only tilting.

I am luck to have a lot of open roof at an azimuth of 189 so I am pretty close to the ideal south facing setting.

Thanks..

Why don't you just run PVWatts and stop screwing around with all this approximate/amateur stuff that doesn't get you anywhere other than more confused to no good end. Take the next step, get out of the sandbox and spend 20 minutes reading the PVWatts help screens. After that, use the model to make a few runs that will get you a lot closer to a likely reality and a more reliable way to estimate the benefits of various scenarios. If you do that, use a 10 % system loss parameter rather than the 14 % default value. You will quickly zero in on one likely max. output orientation and also easily compare outputs for other orientations.

BTW, as long as your worried about small increases in output, know that a 180 deg. azimuth is usually slightly less than ideal for most, but not all residential applications. FWIW, 189 deg. is often closer to ideal.

Also know, as others have pointed out, that the extra costs associated with non roof parallel systems have a cost adder over "standard" roof mounting systems that, in all likelihood, may be greater than the NPV of any additional generation. An extra panel or two added to a standard design is often a much more cost effective way to increase system output.

[bcroe]

I don't see anything above remotely practical for changing tilt. UNIRAC shows a bottom pivot at ground level
with multiple braces. That bottom pivot must be higher to clear anything at all, so it will need bracing to keep
things in place. To avoid obstructions it should be elevated some feet. You would need something to suspend
a portion of the array, then take most of the braces off, then change the angle with your suspension system,
then bolt in a new set of braces, remove suspension system. Move to next panel group and repeat. Big crew,
big operation. Put in actuators, can be done, a lot engineering to keep it all in sync and properly supported at
all times.

Commercial systems use mechaical scanners, but they move E-W. In the process they lay the tilt FLAT so
you need to add a ton more panels to compensate for the zero tilt.

The few percent you are looking for will be washed out by clouds and snow conditions, better to concentrate
on these as I did. Here is a 6KW array I built allowing very easy tilt change by 1 person and no heavy equipment
in under an hour. That makes 2 changes a year practical. It was't particularly cheap, but it essentially solves my
snow problem, I can make up for other losses with more panels.
Bruce Roe
18ArrayF.JPG18ArrayR.JPG

[peakbagger]

I like my home made pole mount with adjustable tilt. I move it four times a year. I was due to move it in few weeks but an early winter weather forecast meant I needed to do it yesterday. It takes me about 15 minutes solo to change the tilt. My small wall mount array also has a tilt feature. It requires a hydraulic jack and lifting post. Its takes about 20 minutes. My roof array is fixed and the definitely flatter than it should be. It tends to get covered with snow in the winter and I will lose days of production until we have a warm up.

I also have a set of hot water panels that are at steeper angle on the same roof on a home made mounting system. It exhibits a significant issue that many folks do not plan for in winter. Snow builds up and slides down the panel and then builds up in a lump at the base of the panel. Unless that lump is removed its tends to build up covers the base of the lowest row of panels. Its far more an issue with the angle SHW panels than the PV panels that are on standard roof mount. The SHW panels still work but the output is decidedly lower.

I have also seen this on large PV farms where the designer didnt plan for significant snow, the snow slides down between the panel rows and eventually build up high enough to cover the lower row of panels. I have seen a few attempts where folks try to clean out between the rows but its backbreaking work as they have to haul the snow to the end of the rows and find somewhere to dump it.

[solarix]

I have known a few DIYrs that installed their own adjustable tilt mechanisms. After a year or so, they always quit messing with them as being too much effort especially to do it solo.

[J.P.M.]

I have known a few DIYrs that installed their own adjustable tilt mechanisms. After a year or so, they always quit messing with them as being too much effort especially to do it solo.

Pretty much my experience as well. Except for Bruce's efforts, most of the DIY stuff I've seen looks more like redneck engineering than something with any real engineering behind it. If it's not messed with after a year a good part of the reason is that it didn't last that long.

[peakbagger]

I guess I am the outlier, my original wall mount array is 16 years old and I adjust it 4 times a year. My pole mount is about 10 years old and it too gets adjusted 4 times a year. They were designed to be adjusted easily. The pole mount requires 2 sockets and a wrench. I use nylock stainless steel fasteners. The wall mount does require a hydraulic jack and wooden pole with two wrenches.

I generate a yearly surplus that I use to heat my house so I probably shouldn't have that much motivation to get the extra power. I built both arrays so maybe that's the motivation.

[J.P.M.]

I guess I am the outlier, my original wall mount array is 16 years old and I adjust it 4 times a year. My pole mount is about 10 years old and it too gets adjusted 4 times a year. They were designed to be adjusted easily. The pole mount requires 2 sockets and a wrench. I use nylock stainless steel fasteners. The wall mount does require a hydraulic jack and wooden pole with two wrenches.

I generate a yearly surplus that I use to heat my house so I probably shouldn't have that much motivation to get the extra power. I built both arrays so maybe that's the motivation.

Not a knock, or a trick question, but how much differential energy do you estimate that you generate with seasonal adjustment over (or under) what you estimate would be an optimal stationary orientation ?

[peakbagger]

I looked at PV watts long ago and think it was in the theoretical 10 to 15% range. Back when I paid $6 a watt for my panels I wanted to optimize the output. Seems to make more difference in the summer as it gives me longer production days (sun rises north of east and sets north of west so the flatter angle helps). I mostly adjust them to winter angle to reduce snow build up on the panels. My wall mounts are below a roof array and when the big dump off the shallow roof panels happens when the roof warms up if I have the wall mount array down at winter angle the snow dump off the edge of the roof just misses them. My wall mount array also make a big difference in cooling season, at summer angle they provide an awning over a set of angle bay windows and cut down on sun coming in the house. I get the same shading at winter angle but the panels block a lot of the view out the windows.

I think the fancy dual axis trackers they make in Vt claim 30% higher yearly output assuming no shading.

I expect it would be hard to justify dealing with adjustable angles when panels are fifty cents a watt.

I work from home and someday like a quick to do project during lunch. Adjusting the panels is a quick easy thing to do and keep me in touch with the seasons.

[J.P.M.]

I looked at PV watts long ago and think it was in the theoretical 10 to 15% range. Back when I paid $6 a watt for my panels I wanted to optimize the output. Seems to make more difference in the summer as it gives me longer production days (sun rises north of east and sets north of west so the flatter angle helps). I mostly adjust them to winter angle to reduce snow build up on the panels. My wall mounts are below a roof array and when the big dump off the shallow roof panels happens when the roof warms up if I have the wall mount array down at winter angle the snow dump off the edge of the roof just misses them. My wall mount array also make a big difference in cooling season, at summer angle they provide an awning over a set of angle bay windows and cut down on sun coming in the house. I get the same shading at winter angle but the panels block a lot of the view out the windows.

I think the fancy dual axis trackers they make in Vt claim 30% higher yearly output assuming no shading.

I expect it would be hard to justify dealing with adjustable angles when panels are fifty cents a watt.

I work from home and someday like a quick to do project during lunch. Adjusting the panels is a quick easy thing to do and keep me in touch with the seasons.

Thank you. Understood. You'll get no argument from me about choices, but @ $6.00/W back in the day, I'd remark that's a pretty steep price/W for the annual surplus you write of.

The #'s I have from the NREL Solar Radiation Data Manual for Flat-Plate and Concentrating collectors for Burlington, VT show an ~ 30% increase in annual POA irradiance for dual axis tracking vs. fixed at latitude. For PV, that probably results in close to 30% more annual output, maybe a bit less.

Do you feel that the cost savings from the smaller but more complicated support/tracking system is worth the (supposed) increased maint. PITA & cost required vs. a fixed orientation array ?

Just curious.

[jflorey2]

Yes, only a difference of 4%...this first figure is fixed position, second is 2 positions, third is 4 positions. Hardly any difference between two and four position, but is it worth 4% more performance to go on the roof twice a rear and change the angle, maybe not. However, keep in mind, that to even get the 71% optimum, for me, that is an angle of 29 degrees and the roof is 18 so I am already 11 degrees off of optimum.

OK. So let's say you are losing 4% of your production to a non optimum angle. I don't know what size your array is - let's say it's 10kW. That means it's producing about 8kW at best. So 4% of that is 320 watts, which is one $160-$200 panel.

So you can 'solve your tilt problem' by adding a single panel. Overall I think that would be a much better (cheaper/simpler/easier to retrofit/lighter etc) solution.

[J.P.M.]

OK. So let's say you are losing 4% of your production to a non optimum angle. I don't know what size your array is - let's say it's 10kW. That means it's producing about 8kW at best. So 4% of that is 320 watts, which is one $160-$200 panel.

So you can 'solve your tilt problem' by adding a single panel. Overall I think that would be a much better (cheaper/simpler/easier to retrofit/lighter etc) solution.

That's kind of what I and I bet lots of others were thinking. Kind of an informed no brainer. The OP needs more education/experience.