How should I point 48' of panels with 45' of roof space?
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Solar Expert Posts: 3,821 ✭✭✭✭
Have been deliberating the pros and cons for two weeks. Since the proper solution is so important, decided to ask some folks with decidedly more expertise than I.
Location:37 degrees N and 105 degrees W (southern Colorado)
Dry, sunny climate at 7800 feet elevation.
This sunroom points approx.165 degrees South. The roof is very strong. I used 3/4" tongue and groove "plywood" on top of material that is substantially stronger than 2 x 10's. We used hurricane ties and "compute" the roof overhang can easily handle at least 140 mph winds. Not uncalled for since location winds hit 80 mph a couple times/year. People talk about 100 mph winds but people also exaggerate.
Here is the problem: I have 18 panels that are 32" wide (62" tall). Total width=48'. The roof is 45' wide. The sunroom is 40' wide. I had four racks welded up. Two are about 11' wide. Two are about 13' wide. The panels will sit at 42 degrees, thus favoring winter time solar optimization.
This is the sunroom that the panels will sit on. It is about 15' from front to back. I can't run 24' racks in the front and the back because the front rack would block the back rack in the winter time.
The empty racks are sitting on the roof. I can easily climb up there and try out any suggested configuration. As we all know, what looks good on paper may not be the ultimate solution.
I appreciate all efforts. I may be on the roof so please be patient if I am gone for 1/2 hour or so.
Location:37 degrees N and 105 degrees W (southern Colorado)
Dry, sunny climate at 7800 feet elevation.
This sunroom points approx.165 degrees South. The roof is very strong. I used 3/4" tongue and groove "plywood" on top of material that is substantially stronger than 2 x 10's. We used hurricane ties and "compute" the roof overhang can easily handle at least 140 mph winds. Not uncalled for since location winds hit 80 mph a couple times/year. People talk about 100 mph winds but people also exaggerate.
Here is the problem: I have 18 panels that are 32" wide (62" tall). Total width=48'. The roof is 45' wide. The sunroom is 40' wide. I had four racks welded up. Two are about 11' wide. Two are about 13' wide. The panels will sit at 42 degrees, thus favoring winter time solar optimization.
This is the sunroom that the panels will sit on. It is about 15' from front to back. I can't run 24' racks in the front and the back because the front rack would block the back rack in the winter time.
The empty racks are sitting on the roof. I can easily climb up there and try out any suggested configuration. As we all know, what looks good on paper may not be the ultimate solution.
I appreciate all efforts. I may be on the roof so please be patient if I am gone for 1/2 hour or so.
First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
Comments
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Re: How should I point 48' of panels with 45' of roof space?
So far, I keep coming back to this: 4 panels oriented to SE 10 panels oriented to South 4 panels oriented to SW Is there a real problem with this configuration?
I want to built a small astronomy/observation tower behind the panels. Thee are also three skylights. So elevating rear racks is not attractive.
Outback FM80 controller & Outback 3648 inverter. Midnite Solar MNEV6 combiner. Will employ 48 volt battery array. All bought three years ago. Yikes.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
This is a great community. I hope that nobody draws up a map and sends me a Paypal bill. Someone did that to me at a different board. I would have paid but my inverter user manuals had more complete and detailed information. Not knocking the guy but I already knew what goes where.
Not averse to paying for needed expertise. Just want a heads up if that is the game plan.
I have read two intro solar books. Just ordered three more in depth solar books. I have an interest in professional solar work of some type. I have a backhoe with a huge trencher and significant construction experience. This is a great area, and time, for solar. Feeling itchy to make a little progress today.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
Maybe you could split them into two rows instead of a single 48' one. The overlap at the end of the roof isn't so much a problem as how it would look to you.
Personally, I would point them all in the same direction.Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year. -
Re: How should I point 48' of panels with 45' of roof space?So far, I keep coming back to this: 4 panels oriented to SE 10 panels oriented to South 4 panels oriented to SW Is there a real problem with this configuration?
I want to built a small astronomy/observation tower behind the panels. Thee are also three skylights. So elevating rear racks is not attractive.
Outback FM80 controller & Outback 3648 inverter. Midnite Solar MNEV6 combiner. Will employ 48 volt battery array. All bought three years ago. Yikes.
While I am by no means an expert (yet!
), I recall reading here that having panels oriented in multiple directions is problematic for a single MPPT controller.
If there's any way for you to use a separate MPPT controller for each subarray, that ought to work well. In fact, you'll start your charging day earlier and end it later, when compared to a PV array that has all panels oriented in the same direction. That could help with both bringing your battery bank up to full charge (you make better use of the early-morning insolation) and also running opportunity loads in the afternoon. -
Re: How should I point 48' of panels with 45' of roof space?
Thanks for the effort 706 jim. I did explain the problems (several) with what would appear to be the solution. The shadow from the front row literally covers the roof this time of year. Skylights make raising the second row problematic. Along with the planned astronomy room.Maybe you could split them into two rows instead of a single 48' one. The overlap at the end of the roof isn't so much a problem as how it would look to you.
Personally, I would point them all in the same direction.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
Thanks. I love everything about this solution except for the considerable added expense and complexity.While I am by no means an expert (yet! ), I recall reading here that having panels oriented in multiple directions is problematic for a single MPPT controller.
If there's any way for you to use a separate MPPT controller for each subarray, that ought to work well. In fact, you'll start your charging day earlier and end it later, when compared to a PV array that has all panels oriented in the same direction. That could help with both bringing your battery bank up to full charge (you make better use of the early-morning insolation) and also running opportunity loads in the afternoon.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
I see you are in CO, here in central BC we get lots of late afternoon/evening summer sun, do you get enough summer evening sun to place a few panels NW to extend your summer charging time? Just thinking...
There was also a recent thread about 2 sided E/W array on one CC and owner said it worked fine ...
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada -
Re: How should I point 48' of panels with 45' of roof space?
Seems like I get a lot. But nothing compared to British Columbia. :roll:
There would appear to be a powerful argument for placing 4-5 panels due west - with their own charge controller. That would free up tremendous space. While increasing my charging time by a large amount. I think I have enough panels to spare some mid-day charging. Have 3300 watts of panels in a fantastic solar location. I do not know what my usage will be but there are only 1-3 people living here. One unless I need to rent a couple rooms...decent chance for that. Pretty energy conscious. Heavily insulated home with led and roof (tube) lighting. A lot of passive energy when the sun shines. I've got six big 4' x 10' passive solar water heating units that I hope to install.....someday. Those things normally cost plenty.
I can't find the thread that you mentioned....yet.westbranch wrote: »I see you are in CO, here in central BC we get lots of late afternoon/evening summer sun, do you get enough summer evening sun to place a few panels NW to extend your summer charging time? Just thinking...
There was also a recent thread about 2 sided E/W array on one CC and owner said it worked fine ...First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
There have been a number of "Virtual Tracker" Threads, here and elsewhere.
Here is one:
http://forums.energymatters.com.au/solar-wind-gear/topic5064.html
FWIW, VBOff Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes. 25 KVA Polyphase Kubota diesel, Honda Eu6500isa, Eu3000is-es, Eu2000, Eu1000 gensets. Thanks Wind-Sun for this great Forum. -
Re: How should I point 48' of panels with 45' of roof space?Thanks for the effort 706 jim. I did explain the problems (several) with what would appear to be the solution. The shadow from the front row literally covers the roof this time of year. Skylights make raising the second row problematic. Along with the planned astronomy room.
Well, how about just leaving one panel off? That would pretty much take care of the roof overlap.
As to your "Astronomy room": Don't know if you're planning to put a telescope up there, but you should be aware that you will be subject to thermal currents rising from the roof and considerable vibration unless you have some sort of massive column going down to the ground.
I sometimes use my telescope off a wooden patio deck and you can literally see the image jump in time with your heartbeat as the veins in your feet pulse (!)
On a positive note, it takes only miniscule amounts of power to run a clock drive.Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year. -
Re: How should I point 48' of panels with 45' of roof space?
Do you have an issue with just letting the array hang out 1-1/2' on each end? (properly supported of course)
There is no other way to squeeze in 18 panels on that roof. -
Re: How should I point 48' of panels with 45' of roof space?There have been a number of "Virtual Tracker" Threads, here and elsewhere.
Here is one:
http://forums.energymatters.com.au/solar-wind-gear/topic5064.html
FWIW, VB
Those are expensive and sometimes foul up. My neighbor has one and wishes he had simply bought more panels. That is a common concensus I think.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?Well, how about just leaving one panel off? That would pretty much take care of the roof overlap.
As to your "Astronomy room": Don't know if you're planning to put a telescope up there, but you should be aware that you will be subject to thermal currents rising from the roof and considerable vibration unless you have some sort of massive column going down to the ground.
I sometimes use my telescope off a wooden patio deck and you can literally see the image jump in time with your heartbeat as the veins in your feet pulse (!)
On a positive note, it takes only miniscule amounts of power to run a clock drive.
Strings should be equal. Have to have even amount of panels I would think when all the panels are the same.
I am thinking of a 4' buffer so the skylights still get light. I also love being up high. I am surrounded by 14,000 foot mountain ranges. The views up high are just spectacular.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?Do you have an issue with just letting the array hang out 1-1/2' on each end? (properly supported of course)
There is no other way to squeeze in 18 panels on that roof.
That is certainly common sense at work. I worry about the additional wind load on overhangs that are already oversized. Yes....I think they could handle it. But the consequences of a roof failure boggle my imagination. The wind load of 42' of 62" panels mounted at 42 degrees? No idea but it is a lot. People in windy areas know that you do not leave exposed edges.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?Those are expensive and sometimes foul up. My neighbor has one and wishes he had simply bought more panels. That is a common concensus I think.
Virtual trackers are not actually mechanical trackers, they are just panels oriented in different directions, mostly SE and SW. -
Re: How should I point 48' of panels with 45' of roof space?solar_dave wrote: »Virtual trackers are not actually mechanical trackers, they are just panels oriented in different directions, mostly SE and SW.
Oops.
Great idea but I believe that both SE and SW would require two additional charge controllers. Nice system but expensive and more complex. First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?Oops. Great idea but I believe that both SE and SW would require two additional charge controllers. Nice system but expensive and more complex.
Actually that is not the case, check the link, many have successfully done it on a single charge controller. -
Re: How should I point 48' of panels with 45' of roof space?solar_dave wrote: »Actually that is not the case, check the link, many have successfully done it on a single charge controller.
I have only read a couple pages but it appears to be THE simple solution so far. I have also read that panels pointing due west perform quite well indeed. As long as this doesn't foul up the MPPT efficiency.
First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
My power will soon look like this! :cool:
Attachment not found.
Note to mods....my apologies but I simply couldn't resist some humor. I'll likely remove it soon...if it doesn't disappear on its own.
My new array is much smaller than many. But a large step up from the approx. 300 watts that I currently have.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
What no arrays? :roll:
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada -
Re: How should I point 48' of panels with 45' of roof space?westbranch wrote: »What no arrays? :roll:
Tornado won after awhile. First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?Note to mods....my apologies but I simply couldn't resist some humor. I'll likely remove it soon...if it doesn't disappear on its own.
Nothing wrong with a bit of humour.
BTW with newer MPPT controllers like the Classic or FM series multiple arrays in different directions is not a problem so long as they are identical in Voltage. The older controllers that periodically 'swept' to obtain their power point could get confused by the different power levels of the arrays and not choose the best I*V. This does not seem to be an issue anymore. -
Re: How should I point 48' of panels with 45' of roof space?Cariboocoot wrote: »Nothing wrong with a bit of humour.
BTW with newer MPPT controllers like the Classic or FM series multiple arrays in different directions is not a problem so long as they are identical in Voltage. The older controllers that periodically 'swept' to obtain their power point could get confused by the different power levels of the arrays and not choose the best I*V. This does not seem to be an issue anymore.
Thanks...I rather liked my power picture. Thanks again!!! My Outback FM80 was made and bought in 2011. I think this fits your "approval".
Man alive...this off grid stuff is interesting. And challenging.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
hang on tight, the ride is just starting! YeeHa...
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada -
Re: How should I point 48' of panels with 45' of roof space?westbranch wrote: »hang on tight, the ride is just starting! YeeHa...
Definitely get that impression! I've been using small arrays and gensets for four years. Feel like I am back in college these days.
Played with some numbers at this web site. http://rredc.nrel.gov/solar/calculators/pvwatts/version1/US/Colorado/ Pretty handy I must say. This is what I have arrived at: Point 10 panels at 165 degrees. Point 4 panels at about 140 degrees. Point 4 panels at about 210 degrees. The 42 degree panel pitch works just fine. Slightly biased towards winter production while losing some summer production.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries -
Re: How should I point 48' of panels with 45' of roof space?
Good choice , in summer there is usually lots of output, not so in the winter, for us at least and that is the part to optimize..
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada -
Re: How should I point 48' of panels with 45' of roof space?
And in my case the summer production is more important for my AC loads. It is all about the loads you expect and when they occur. -
Re: How should I point 48' of panels with 45' of roof space?solar_dave wrote: »And in my case the summer production is more important for my AC loads. It is all about the loads you expect and when they occur.
To be expected in Phoenix. I bought an a/c unit and really do not believe that I will ever need it. I did a couple things right. This place stays cool in he summer. White roof, R-30 roof insulation, well sealed. Large eave overhangs on south sides. Here it is all about staying warm in the winters. The average winter night drops to about 0 F degrees.First Bank:16 180 watt Grape Solar with FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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