Solar Carports

[Space Buff]

Hi,

tl;dr: Looking for pricing on the carport structures for solar panels.

Longer story:

My roof has two different materials. The East/West facing roof is modern composite shingles, the North/South facing roof is wood shakes. The South facing roof could fit 14 or 15 panels and I need about 6-7kW, so I would still need some on the E/W roof. The E/W roof could fit all the panels I need on either side, but the West side is street facing and my wife isn't keen on the Solar Panels on the front of the house (even though other neighbors do).

I got some price quotes for reroofing the wood shake roof and it's in the $8k range. I could just put all of the panels on the East roof, but would of course need more panels to make up for the loss of not using South facing. Eventually I'm going to have to reroof the wood shakes, but can't afford to do that and the solar.

I'm about to build a play yard for my kids this winter and I was thinking how cool would it be if it was shaded with one of the carport structures. I would get two for one, a unique shade structure and south facing solar. Not sure what the permitting would be like either, but if the cost is less than reroof and/or the extra panels needed for East facing, I thought it might be a win win. I found a couple of places online that supply them, but no one with pricing.

[philips]

I don't know if carport pricing will be cheaper (I doubt it), but I just had a patio cover installed (TEMO branded) that I had engineered to support 5.7 kW DC of solar panels and associated equipment. The patio cover was 50% of my installed cost (solar was about 40% and permits/electrical upgrades filled out the rest) and I self installed the panels and electrical.

Re-roofing would be cheaper in the short-term I would think. The advantage of the carport is that you should be able to take the federal tax credit on that, where you can't on a re-roof which may tilt the numbers in favor of the carport - check with your accountant.

[philips]

Photo of solar patio cover:

solar patio.jpg

[Space Buff]

Wow, that looks great. Love it.

[Mike90250]

with that flat of a roof, you should inspect it for debris (leaves, bird stuff) and be prepared to wash it monthly

[SunEagle]

with that flat of a roof, you should inspect it for debris (leaves, bird stuff) and be prepared to wash it monthly

I was kind of surprised about the flat mounting. You would think the panels could have been raised on one end to provide a more angled exposure to the sun.

Then again everything that got on those panels would wash into the pool.

[philips]

They are almost flat (2.5% slope) mostly for aesthetic reasons. I didn't want a downspout on the pool side of the cover so it needed to slope the other direction which faces northeast . Also, my house looks out over the pool and the valley below and I didn't want to be looking out at solar panels.

I have measured a 7% production loss due to soiling over a two month period by cleaning one panel and comparing it to an adjacent one. Rain came shortly there after, and brought all of them to within 2% of the panel I cleaned. The effort to clean them manually is not worth it to me, but I will keep an eye on it.

Lastly, I modeled the system against my utilities TOU rates (which are much higher in the summer months) and found from the ideal tilt to where they are only made an annual difference of a couple hundred dollars, so I found it better to add a couple more panels to make up for the difference.

The rear of my house roof faces south and southwest, but it is shaded by tall trees and the hillside behind me for a good 6 months of the year, so I ended up being better off building the solar patio.

[DanKegel]

They are almost flat (2.5% slope) mostly for aesthetic reasons. I didn't want a downspout on the pool side of the cover so it needed to slope the other direction which faces northeast . Also, my house looks out over the pool and the valley below and I didn't want to be looking out at solar panels.

I have measured a 7% production loss due to soiling over a two month period by cleaning one panel and comparing it to an adjacent one. Rain came shortly there after, and brought all of them to within 2% of the panel I cleaned. The effort to clean them manually is not worth it to me, but I will keep an eye on it.

Thanks for posting that measurement!

[J.P.M.]

An artificial rainstorm with a hose (but always in the morning before the sun is high) will probably restore a lot of the clean performance. Low slopes usually require more frequent attention to cleaning.

FWIW, your observation about 7 % performance degradation from dirt (fouling) in 2 mo. and rain cutting that loss to about 2% seems generally in line with my SWAG at about 1%/week fouling for my array when it doesn't rain and, depending on intensity and duration, rain restoring about 2/3 to 3/4 of the performance loss. At its most precise, solar's not an exact science and this fouling business is about the least precise of all or most of it.

[philips]

An artificial rainstorm with a hose ...

I've thought of that, but I know if you wash something around here and don't dry it off, you get calcium spots which are harder to remove than the dirt, so I hesitate to take a hose to them.

[J.P.M.]

I've thought of that, but I know if you wash something around here and don't dry it off, you get calcium spots which are harder to remove than the dirt, so I hesitate to take a hose to them.

FWIW: H2O chemistry is different everywhere, but I've been washing my array for about 2 years now, about every 3-6 months depending on rain, and how the fouling measurements I do are proceeding, and because I usually, but not always squeegee the array after a wash/rinse, I haven't seen any water spots of a major nature.

Perhaps more importantly, and contrary to what may be accepted as fact (or simply repeated information), my experience is such that whether I soft scrub wash and rinse w/D.I. H2O, or regular H2O rinse, or simply rinse w/a hose w/o squeegeeing the panels afterward, any visible spots that remain from not squeegeeing seem to have no measurable effect on array performance or perhaps more accurately, the efficacy of the cleaning with respect to restoring clean performance.

I believe the eye may not always be the best indicator of surface cleanliness with respect to transmission of solar radiation for PV applications. Also, the spots that may remain are easily removed if such removal by squeegee is done soon after deposition. I'm not too sure that dust that turns to hard surface mud/crust from morning dew doesn't, over time, leave some unremovable scale depending on the pollutants in the air. As I suggested, this is not an exact business.

Take what you want of the above. Scrap the rest.