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Old 12-14-16, 01:51 PM   #61
bennelson
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We got some sunny (and COLD) weather, so I set up a camera to see how much sun the roof actually gets.

The bad news is that there IS some shading. The good news is that we are nearly at the winter solstice, and that this is the craziest, WORST time of year in terms of bad sun angle, long shadows, and fewest hours of sunlight per day.

Solar power only goes UP from here!


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Old 12-14-16, 02:07 PM   #62
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I am not sure what solar you are going with. After watching that video you will want microinverters or per panel optimizers.
That will help your solar production by a fair amount over the life of the array.
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Old 12-17-16, 09:24 AM   #63
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Yeah, I was looking at micro-inverters from the start.

I did just borrow a Solar Path-Finder from a friend. I'll play around with running that too.
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Old 12-17-16, 10:58 AM   #64
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Ben,

You have enough room on your new garage roof to do an eight panel (60 cell) wide (panel width = 39 inches) install in a portrait configuration. This calculation allowed 0.5 between panels and 2 inches on the end for panel attachments to the rails. This would be with 255-265 W panels.

Two of the rows (16 panels total) would give you a ~ 3.7 kW (16*.23) with the Enphase M215 microinverters. Three rows (panel length of 65. 3") would need 17 feet from eve to ridge - and it looks like you have that space. Three rows (24 panels) would be a 5.5 kW system.

The current costs for such an Enphase M215 system are about $1.05 a watt not including wiring and other electrical conduit, ground rods, etc.

If you can pay a bit more per watt, then move up to the Enphase M250 and 280-290 watt panels. Three rows with the M250 would give you about 6.0 kW (24*.25). Costs here for a self install are about $1.15 per watt (excluding wiring stuff).

The "best' would be the Enphase S280 with 320-330 W panels - but now, the additional cost doesn't pay you off (~$1.45/watt).

A 24 panel system would be perfect and would shade your southern roof - allowing you to store the sofa up there in a temperature moderated space for "occasional" use.

Looking great!



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Old 12-17-16, 08:17 PM   #65
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The roof might be a little too tight for 8 panels across. You always need a little extra room on the ends for the start and finish of the rack. I don't know that 2 inches of roof on the edge of the roof would be allowed. There's no strength under the overhanging ends of the roof either.

I'm pretty confident about 7 panels across. If I can get away with 8, I'll try it. I still have to go talk to the building inspector and get everything checked out with him ahead of time.
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Old 12-17-16, 08:21 PM   #66
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I was also able to borrow a Solar Pathfinder.

The solar access at the garage is pretty good. Not perfect, but pretty good. As you could see from the time lapse video I already shot, there's a little shading at these very short days of the year.

I was only able to set up the solar pathfinder on the ground right at the base of the garage. The roof is covered with snow, and I didn't have any good way of doing the pathfinder actually on the roof. I'll to a Solar Pathfinder trace again sometime when it's reasonably safe and accessible.

Solar Pathfinding

http://300mpg.org/wp-content/uploads...nder_sunny.png
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Old 12-17-16, 09:04 PM   #67
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"I'm pretty confident about 7 panels across. If I can get away with 8, I'll try it. I still have to go talk to the building inspector and get everything checked out with him ahead of time."


Ben,

The brackets for your type and pitch of roof can be as much as four feet apart with a 2 foot overhang. You really don't even have to hit the trusses as you have a good plywood deck.

Do you have enough roof space, eve to ridge, for three columns?


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Old 12-26-16, 01:44 PM   #68
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Part of the reason to do the roof with real plywood, instead of OSB, etc., was to make it nice and solid for the metal roofing and solar panels. Should make it good for mounting the racking.

We had some nice weather today (sunny AND above freezing!) so most of the snow melted off the roof. That lets me actually make some measurements.

From the peak to the eave is almost exactly 18 feet. I don't actually have a tape measure long enough to measure the width of the garage, but on the plans, the building is 27 feet wide PLUS a one foot roof overhang on each side.

A projection for three rows of 8 solar panels comes out to 27 feet wide by 16 and a half feet tall.



That would put the edges of the solar all the way out to the edge of the frame of the building itself, but NOT put any weight on the overhang.

It seems like every solar install I've ever seen has an extra couple inches of rack on either end. I'd also need someplace for the combiner box to go, which usually is mounted on one of the rack rails. Because of the one foot overhang all the way around, this should give enough space for a few inches for racking and a 6x6" combiner box.

Again, I still have to go talk to the local building inspector in person to see exactly what he expects. I've kept my eye on the only other PV installation that I know of under the same jurisdiction, and it comes pretty close to the roof peak and a pair of valleys, so I think that the local regulations shouldn't be overly restricive.

I overlaid the solar panel layout on top of my garage plans diagram. The solar panels image is web-generated from a wizard, so it's not necessarily perfectly to scale or an exact representing. I think I got it pretty close though.

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Old 12-26-16, 02:10 PM   #69
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Here's a video tour, showing where the construction progress is so far!

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Old 12-27-16, 06:04 AM   #70
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Ben - just a thought here . . .

Assuming you can get permission for the array size of 8 panels wide by 3 rows. I might suggest EPDM roll roofing on this south aspect of the garage. It is cheaper than 3-tab, lasts longer, faster to put up and it won't be seen (covered by panels). Or are you doing metal? - can't recall.

In general, living spaces require a set back of the panels from the roof edge. Since this is a garage (not living space) and is a small area, I bet you can get permission to install the panels 8 wide (almost to the roof edge). Firefighters like "open" roof space to be able to vent roofs, letting out smoke allowing more time for people in lower living space to get fresh air. I understand the "walkway" around the panel edge is a secondary issue.

But the real reason is savings on the roof mounting brackets. There are a variety of names for the metal panel that slides under a 3-tab shingle and has an attachment for a L bracket (for rail attachment). About $12 -14 each.

These are a pain to put in and have only one long attachment screw that really needs to be into a truss.

The alternative is the S5! Versagard - about $4 each. Can be screwed into plywood (as you have put up), has six small screw holes (distribute stress) and is a lot cheaper and FAR faster to put up. And you don't need to find a truss underneath.

Assume a 26 foot rail length. You can cantilever the rails 2 feet on each end, but let's just go with one foot to a roof bracket. Then install another 5 brackets evenly between those two outside edge brackets. I think (note the time I am writing this), that the bracket spacing will be about 4 feet.

The EPDM roll roofing is quick to install, your roof has plenty of pitch (no seam leaks with minimal overlap) it will last a long time as it is shaded.

Not often that there is a choice on roofing materials, but this one seems like a no brainer as you are putting up solar.

If you are not looking at the north side of the garage roof - why not use roll roofing there too?

Very nice construction to date, well done and it looks like it has been fun AND an accomplishment.


Bravo!


Steve

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