My electric provider, Bluebonnet Electric Coop, just published the rate that they will pay for "customer production" for 2021. It is $.060631/kwh. For 2020, it was $.0645. So a reduction of about 5%. For 2019, the rate was a bit less than for 2020.
So, off I go. Planning to install new electric service for the sole purpose of feeding the grid. It will be a 50kva transformer for full 200 amp 240vac split phase service. Cost will be about $7k to get power to main breaker boxes.
My most recent iteration on two faced rails has been three joints of used oil field 2 3/8" pipe. Total rail length is near 100'. A 4th pipe joint is needed to cut into posts to support the rail. A rail can support up to 30 panels facing each direction. For string inverters, the panels are divided into four strings of up to 15 panels each. Two east strings and two west. Pairs of strings, one E and one W are combined at the rail. A pair of wires then carry power to the inverter for each pair of panel strings.
The most cost effective string inverter currently seems to be the old SMA/SunnyBoy 4kw transformer type. Cost about $600. Four strings, 2E and 2W, of 12 panels seems to be enough to keep the 4kw inverter busy. So, I plan to initially install 4 strings of 12 or 13 panels on each rail but leave room to add up to 2 panels to each string. I also plan wiring that will allow using two inverters per rail.
So, I'm planning 10 rails with 10 4kw string inverters.
Cost of materials for each rail:
1) four joints of pipe @ $20 = $80
2) 1 4kw inverter $600
3) 52 250w 60 cell PV panels @ $45 = $2340
4) 400' of two conductor 10ga DC wire @ $.40 = $160
So, about $3200 per rail or $32k for all ten.
Total project cost might be $45k excluding my labor.
Since I've had similar rails in production for several months, I should be able to come up with a pretty good average energy production estimate. September 2020 was not a particularly good sun month and the production average for a 48 panel rail was about 30 kwh/day. With several 40 kwh days. So, 365 x 10 x 30 = 109500 kwh/year. $6570/year. A seven year pay back period if rates remain fairly stable.
Note that paying for the meter/transformer is a significant fraction of the cost. I've been claiming that my pay back period for adding PV production to existing meters is about 5 years. These cost estimates support that claim.
Note that there is significant risk of declining rates. Utility scale PV installation costs are declining. It seems such installations are now selling energy as low as about $.02/kwh. I believe Bluebonnet is able to offer as much as $.06 due to their transmission costs for the cheap west Texas wind and PV energy.
I will build the inverter shed and install wiring to allow adding panels up to strings of 15. Several possibilities: I can use two 4kw inverters per rail; I believe each inverter would produce no more than about 3kw. Or, I might find more cost effective inverters around 3kw. Or, I might find ~6kw two tracker inverters that are attractively priced. All of those strategies would produce more energy per rail but might not be cost effective.
I've seen half rails of a pair of 15E and 15W strings produce about 2.5kw. So, I would lose about 1kw by running a full rail of 60 panels into a single 4kw inverter. OTOH, it would cost twice as much for inverters to get that 1kw. So, I'll likely use rails of 52 or 56 panels. Maybe even only 48.
For weed block, where the panels sit on the ground, I've been using used or scrap metal roofing material which is free. I'm mostly able to drive my mower over that metal to keep weeds from shading panels. I'm have trouble getting the material and priced new corrugated steel roofing. Near $2/foot. An additional cost of around $3/panel.
10/6/2020
Charge from Bluebonnet for new meter/transformer was slightly less than $2k rather than the expected/quoted $4k+. Other costs to get electricity flowing: an electrician to satisfy Bluebonnet and install disconnect and main breaker boxes. $2k+. Plus shed, $2k-$4k.
I haul panels sixty at a time. So, about ten trips to fill the ten rails. Once the transformer is in, I will need to try to haul about one load a week. Maybe I should consider building a loading dock or ramp and buying a fork lift.
10/13/2020
Getting all rails staked out before I construct the first. There will be 12 rails staked between the view point and the utility pole at the top of the hill. I'll likely select the ten to be constructed. South boundary fence is on left. Many Christmas Trees on right will be removed. North/south is slightly up hill from left to right not quite perpendicular to the fence; about 75-80 deg.
https://goo.gl/maps/RqAstVCSzDRa8izx7
Transformer and meter will be installed near the pole whose shadow is visible on the left of the map and is silhouetted against the sky in the photo.
10/14/2020
On ordering the needed inverters, I am informed that they are sold out. So, the search for most cost effective inverters resumes. With the conversion to one microinverter for a pair of panels on old rails, I will free up enough equipment to do one or two rails on the new project.
A test of using a more modern Enphase microinverter to serve four old 250w panels is planned.
Despite news of "rapidly declining" PV costs, much of the equipment remains astonishingly expensive.
10/20/2020
Bluebonnet decided their first cost estimate was correct. So, near $5k for the transformer/meter, near $3k for a shed, maybe $1k for an electrician. No doubt, other expenses also. I'm about to get another load of oil field pipe. $15 each for 40 plus ~$200 to haul. Crappy pipe has to be welded because threads are rotted. An additional cost of at least $20 per 3 joint rail. No joy in trying to get a cheap surplus SolarEdge inverter to work without the "optimizers" that cost $50-$100 per panel. Enphase and SolarEdge are the big players in the inverter game. Neither seems eager to drive down costs.
11/1/2020
The new shed should be completed today. These photos from yesterday.
Wood stake in foreground will be location of new transformer pole which is in line with other poles. Building will be 15 feet from power line. Building will be 8' x 24'. 8' high on near side, 7' on far. Two walls, left 8' and far 24'. Breaker boxes will be on 8' wall and inverters on 24'. Pine trees will be removed to allow for rails.
11/2/2020
New shed completed yesterday.
https://photos.app.goo.gl/UiuZ1Y9w1oamXVtTA
Some photos in the album have associated comments/explanations.
11/5/2020
Pole and transformer were installed this morning. I added a few photos to the above album. Breaker box not yet installed in the shed.
James welded up several rails for me. As soon as I get some 120vac I'll start boring holes for rail posts.
3/4/2021
12 of 18 pallets were delivered today:
https://photos.app.goo.gl/kTJeEQgRs4Q35NuX9
Two and a half rails have been producing for a couple of months but I had run out of panels.
This all seems like you are very busy with an interesting and productive project. Larry and I talked about coming by to see what you’re doing. Don’t know when, but we are wanting to come take a look one of these days.
ReplyDeleteOf course, you are welcome anytime. Unless you are applying for the position of housekeeper, I can not offer accommodations. However, I AM shopping for some cabin/trailer to put under the new guest house slab shed. Last trip through Athens, I stopped in one of the tiny house places. Tiny houses are very attractive but discouragingly expensive. If you encounter portable cabin deals, let me know. Perhaps I need to shed the "poor" mindset.
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