I got on the HOA board and made my info useful, at least in their opinions. Since I was the guy reviewing/recommending PV applications to the Arch. Rev. Comm., things worked well. Just sayin. Boards can be a PITA. I've found it's easier working with them when we're all peeing into the same field latrine.
I've used the single diode model in stuff I've written. Estimated output from my stuff to be in reasonable agreement most of the time w/array measurements and usually agrees pretty well w/SAM's est.
NOMB, but last time I checked the S.D. building code, vents couldn't be covered by arrays. maybe I missed the part about flush mounted vents. I'd find out who the AHJ inspector is and ask. No harm, no foul.
My est. SAM output is 9,469 kWh/yr. less ~ 3-4 % late afternoon shade. Considering weather/irradiance variability, I seem to be making that.
FWIW, 9,469/5,232 - .04 = 1.81 - .04 = ~ 1.77.
13,600 kWh/yr./7,840 W = 1.73 seems doable around here for a 7.84 kW array.
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Tandem's store worked / is working for me (Firefox), although I contacted them by email and had a short chat on the phone to get the quote put together. FWIW, I'm not receiving anything from them for mentioning them in this forum, although I let them know that I would be publicly documenting this installation experience.
I will be paying through paypal for a 2.9% surcharge, backed by a 2% cash back credit card (Citi double cash). The credit card balance will be immediately transferred to Chase Slate, the transfer is free and 15 months interest free gets me past taxes next year so I should have the tax credit in hand by then. I have a small windfall coming from one of my investments that will pay out later this year, covering the balance. I actually paid for the PV system on my old house the same way, and had cancelled the Chase Slate immediately after paying it off. Apparently they don't mind me doing this again 2 years later.
I intend for it to be truly DIY. I did my own permit, although for the amount of time it took (20ish hours), spending $350 for a local PE to handle it would probably have been worth it. I'll post more about that later. It is sort of a squishy reason, but this project will help me bond with this new house (we moved in last summer)... I had fully redone the kitchen in my old house, and find this kind of work to be enjoyable (when my livelihood doesn't depend on it). If I were to correctly account for my time, I doubt I'm coming out ahead, but I'd still like to show what the lower bound for installation cost might be, in practice, as well as contribute that experience to a forum from which I've learned so much. There are a couple of ways I could probably have shaved the cost down further, which will be clearer as I write more about this.Leave a comment:
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The Davis will go in immediately after I get PTO from SDG&E, I just don't want it up there sooner as a distraction. HOA might not like it someplace too prominent, my immediate neighbor is the board president so I'll have to talk with her more about it. Only the one vent shown is on this roof face, most are on the north face. (sadly, I was looking at stuff like this when we were house shopping last year). Attic ventilation is all low profile, so while it isn't exactly the right thing to do, I don't think I'll run into trouble covering over those areas.
The design is using the taller QMHSS hooks by Quickmount PV, with XR100 rail. Ironridge's engineering is based on 2" - 5" clearance, so I'll try to get as high up the 2.5" slot as I can within that range. I'd rather have the better airflow; this array won't be very visible from the ground so the aesthetic preference to keep it tight to the roof isn't so important to me.
Quickhooks.JPG
A quick PVWatts run at 10% loss (Premium, 19 deg tilt, 176 azimuth) puts it at 13600 kWh annually. Average monthly consumption over the past 7 mo since we moved in has been 650 kWh, about what I had in the old house (~8000 kWh annually). There, my bill was fully offset (in dollars) by a 3.1 kW array on TOU-EV-2, so this is definitely not winning design awards for cost-effectiveness unless some of our future plans become real. We could be putting 24k mi annually on the next EV, which would be another 6000 kWh or so of consumption. Assuming the EV TOU tariff is still open at that time, this system will still safely cover those costs even after the peak hours shift later.
Most of the work I've been doing with SAM lately is trying to re-create their implementation of the CEC module performance model (with NOCT modeled cell temps) in python. Even with NREL's technical documentation, I wouldn't get far without Duffie and Beckman's Solar Engineering of Thermal Processes textbook and explanation of the single diode model.
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Yes, please keep us updated on your progress. I'm getting ready to go down this road myself soon here in Scottsdale, AZ.
Tried to go to Tandem's online store, but it looks like that aspect of their website is NRFPT yet...
Couple quick upfront questions:
1) Where did you find financing, or are you paying for this in cash?
2) Have you lined up subs for any of the work (electrical, etc), or is it all truly DIY?Leave a comment:
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Lots of stuff to plan for. Where/when will the Davis be added ? FWIW, I moved one stink vent and reduced the height of 3 others. What are you planning for array to roof clearance ?
What does SAM say/SWAG for output ?
Add: Do you know how/where to walk on a tile roof ? Do you have spare tiles ? Just askin'. You'll need both.Last edited by J.P.M.; 03-24-2017, 04:44 PM.Leave a comment:
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DIY Self-Install in San Diego - 7.84 kW for < $1.30 / W
It looks like my permit is going to be issued, so it is about the right time to start a thread to document this installation. The plan is to put up 28X CS6K-280M with a 7600 W inverter. Here is the layout. All of the greenery south of and around the sides of the array are much lower than the 2nd story, so the only potential shade source I'm seeing is a plumbing vent that might affect the rightmost panel on the top row early in the morning, if that panel ends up too close to it (San Diego requires at least 4" clearance). Layout.JPG
I'll write more about some of the design decisions with updates to the thread, and provide pictures of progress as it is made... I expect this will be drawn out as I work on it in free time over the next several months. The system is sized much too large for any of my existing needs, but we are planning to add a 2nd EV in the next couple years, maybe an AC, and for this cost, I'd rather do this once and get locked in under NEM 2.0 than take my chances with what comes next. Until SDG&E's GRC phase 2 is approved, I should still be able to get into the tiered DR tariff, and receive the (small) credit back for the overproduction at the end of the year. Definitely not the most cost-effective design I could go with, but my wife had asked why stop at just 5 kW if I'm going to be up there anyway, so I took the easy way out. An installation of just the 16 panels across the bottom (4.5 kW) would probably have been enough for the short term (Thanks to the miracle of the TOU-EV-2 tariff).
The budget has been helped by working with Tandem Solar Systems, who look like a viable competitor to Renvu here in southern CA. Free delivery of a pallet of panels saves over $400, and their pricing is very competitive on the rest of the system (inverters, racking, tile roof attachments) as well. With the BOS electrical coming from big box stores, it looks like the total cost will come in somewhere around $10k ($7k after the tax credit).Last edited by sensij; 03-24-2017, 03:26 PM.
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