Solar Panel Placement on Roof

Hi,

I have to lust after that 17 kwh 2 volt battery bank at Starlight.

mena661 wrote:
Thanks, it should work well. I'm going to use #4 from roof to controller ($50 for 50ft on ebay),

Make sure it is pure copper, not copper coated aluminum.

Meet this camper in Deep Creak Beach, AK and he had 4 panels. He indicated that he could have gone higher but had eliminated the shadows. The material was from a used screen porch.

CA Traveler wrote:
That will be a nice system. Set up the wiring for 3 panels. You can actually go to 5 panels with that controller.

Here's a link to a Starlight installation. Unfortunately no details in the picture. I'll search for one of my pictures.

Thanks, it should work well. I'm going to use #4 from roof to controller ($50 for 50ft on ebay), that should be plenty for the 3 panels. Those are some interesting mounts on that site. Definitely the way to go to get big solar on the roof.

mena661 wrote:
I have the Morningstar PWM 45A so 1 and 2 would be the only options. I know I can get two up there easily. 3 would be great. 6 inches off the roof might be good for a future expansion idea that PT came up with.

That will be a nice system. Set up the wiring for 3 panels. You can actually go to 5 panels with that controller.

Here's a link to a Starlight installation. Unfortunately no details in the picture. I'll search for one of my pictures.

Thanks, Updated MPPT efficiency to 3% and an additional 8% for PWM.

I have the Morningstar PWM 45A so 1 and 2 would be the only options. I know I can get two up there easily. 3 would be great. 6 inches off the roof might be good for a future expansion idea that PT came up with.

Hi CAtraveller,

MMPT loss is not 8%. More like 4%, worst case.

MPPT gains are about 8% under most conditions, compared to PWM. That might be where you got the 8% figure?

Mounting the panels close to the roof will cause significant shadows and it's not necessary Every time I see a rig with the panels mounted higher I ask them what they have done. One of many options is to use used 2” aluminum square channel (like the kind used in sun rooms) and mount the panels at a height that shadows become a non issue, like 6” or more high. Mount the panels EW, the channel are mounted NS and considerations like rafters securing become a non issue. And with say a 6” high mounting the worst case rig orientation, shadows would be about 15 degrees of sun rise to no shadows and ditto for sun setting. Different rig orientations could reduce or eliminate the sun angle with shadows.

Here is a comparison of some possible solar configurations based on current Solar Blvd and Rogue costs.

1. 2 PV-SC150J12 panels 300/267W TS 45 controller. $476 (2*165+146) $1.59/W 21.4 sq ft parallel
2. 3 PV-SC150J12 panels 450/401W TS 45 controller. $641 (3*165+146) $1.42/W 32.1 sq ft parallel


1A. 2 PV-SC150J12 panels 300/291W Rogue MPT 2024. $605 (2*165+275) $2.02/W 21.4 sq ft serial or parallel
2A. 3 PV-SC150J12 panels 450/437W TS Rogue MPT 3048. $870 (3*165+375) $1.93/W 32.1 sq ft serial

The second watt number is the effective wattage due to the controller losses not counting wiring losses. 3% MPPT controller efficiency loss and an additional 8% PWM controller efficiency loss.

Here’s an expanded and more expensive setup:

3. 2 LG270 panels 540/523W TS MPPT 45 controller. $836 (2*203+439) $1.54/W 36.0 sq ft serial or parallel

Panel size: PV-SC150J12 58.2×26.4 LG270 65.67x39.3

With raised panel mounting there appears to be two locations for a third panel. More information would be required for further analysis.

Updated MPPT efficiency.

Hi,

Home Depot sells the grape solar as well--and has a gs-100 model.