My Solar PV Installation

[Andy]

As many of you know I design and manage the installation of PV Solar Systems for a living.

It's been years in the planning, but I have finally gotten around to installing a system on my house.

It's a 15 kW DC 60 panel system with 2 SMA SunnyBoy 6000TL-US-22 Inverters.

Yesterday we made good progress getting all the racking, array grounding and DC wiring complete.

 

[icerabbit]

Impressive. Keep us posted! The one thing that has always worried or bugged me when it comes to solar on the roof, is the shingles. So I've always had thoughts about a metal roof first, solar awnings or a free standing rack. What is your experience when it comes to longevity of shingles in and around a solar install? And how about keeping things free from leaves etc. when there's several horizontal channels, for those who live with trees nearby.

 

[nayr]

buy the 50 year shingles when redoing your roof instead of 20 year shingles; I imagine having a new roof put in after a solar install wont be cheap or easy.

 

[Andy]

Regarding shingles. If a roof is not in good shape we always recommend that the roof be replaced prior to solar being installed. Their are several studies that were done that the solar panels actually protect the roof and significantly slow down it's degradation. The flashing and mounting system used and the quality of the install is very important when you don't want to have to touch it for 30 plus years. Regarding leaves, etc. Yes they will catch under the array. Typically the trees that would be prone to dropping leaves on the roof have been removed to minimize shading. Also a few leaves under the array usually just wash or blow away.

 

[Andy]

Today's progress Panels up inverters up, wiring to go

 

[Mike]

Looks great! Looking forward to seeing the end result.

 

[icerabbit]

Wait? You have panels in two directions? Which way is south?

 

[Andy]

Wait? You have panels in two directions? Which way is south?

It's what's called an East-West Array. The 40 panels have an Azimuth of 120 degrees and the 20 panels Azimuth is 300 degrees.

Overall it results in about 15% less production than a due South 180 degree Azimuth array. One of the benefits of an east west array is that you get better production earlier and later in the day.

California just increased the rebate on west facing arrays to try and increase production late in the day when the power company needs it the most.

If you're interested in seeing how Azimuth and tilt effect production you can play with NREL's PV Watts simulator. http://pvwatts.nrel.gov/

For my 40 panel array 180 degrees is 13,163 kWH/year and 120 degrees is 12,079 kWH/year (91.2%)
The 20 panel array 180 degrees is 6,581 kWH/year and 120 degrees is 4,654 kWH/year (70.7 %)

For a total projected production of 16,733 kWH vrs 19,744 kWH (84.75 %) in a nominal year

Only time will tell and we'll also see how many snow covered days we have.

 

[icerabbit]

Cool. I'd read before that off-axis works pretty well, due south isn't required, and facing sw can actually be better to deal with peak needs; but I hadn't seen it done like on your install. Probably due not seeing much solar in both places I frequent. Anyhow. Looking forward to hearing how it works out.

I assume you will need to "rake" the panels with a foam scraper on an extended pole, after every snow, to keep the panels clear?

Playing with that website calculator, looks like I'd need a pretty big install. Bank the excess in the summer and put it towards the shortage during winter. That is with ideal siting, I presume. It is just not practical with the direction of the house, surrounding trees, steep roof pitch, ... I'd have to build a long south facing rack on the north side of the property facing south. Maybe integrate it in a carport or get several solar pedestals racks (or whatever name they might be using for racks on a post) I think I'll wait till we downsize

 

[Andy]

Cool. I'd read before that off-axis works pretty well, due south isn't required, and facing sw can actually be better to deal with peak needs; but I hadn't seen it done like on your install. Probably due not seeing much solar in both places I frequent. Anyhow. Looking forward to hearing how it works out.

I assume you will need to "rake" the panels with a foam scraper on an extended pole, after every snow, to keep the panels clear?

Playing with that website calculator, looks like I'd need a pretty big install. Bank the excess in the summer and put it towards the shortage during winter. That is with ideal siting, I presume. It is just not practical with the direction of the house, surrounding trees, steep roof pitch, ... I'd have to build a long south facing rack on the north side of the property facing south. Maybe integrate it in a carport or get several solar pedestals racks (or whatever name they might be using for racks on a post) I think I'll wait till we downsize

I might rake off the panels with something soft but I may no have too. They are pretty slippery and the panel itself tends ot warm..The snow usually comes off in a large Heavy sheet that you don't want to be under. Onmany commercial building and schools we put snow guards up to stop the snow from coming off in one sheet

 

[Andy]

Playing with that website calculator, looks like I'd need a pretty big install. Bank the excess in the summer and put it towards the shortage during winter. That is with ideal siting, I presume. It is just not practical with the direction of the house, surrounding trees, steep roof pitch, ... I'd have to build a long south facing rack on the north side of the property facing south. Maybe integrate it in a carport or get several solar pedestals racks (or whatever name they might be using for racks on a post) I think I'll wait till we downsize

What's your annual usage PM me your address and I'll look at your roof

 

[icerabbit]

Thank you for the generous offer, Andy.

I'll gather some details and summarize for you what I've got going, tomorrow. Been a long day. Time for a shower and some zzz. And, maybe we can exchange email via pm. Would make it easier for me to send a few details as attachment your way, vs having to host them online and then link to.