Solar PV - Save Money & Shrink Carbon Footprint

[NeilBlanchard]

We have been driving EV's for 3 1/2 years, and we are now using a heat pump for most of heating our house, as well. We got a solar PV system installed yesterday, and it should soon be generating a large amount electricity, to offset our use. The system is Sunpower 327 watt panels (about 20% efficient), and it is warranted for 25 years. The system will pay for itself in just over 5 years, with all the incentives, and in less than 10 years without them.

It is a 10kW system on the AC output, and the estimated annual output is just under 13MWh.

We have expensive electricity here in Massachusetts - we pay between 18¢ and 22¢ total per kWh (both generation and distribution costs); and we also have chosen to pay another 2.4¢ / kWh to support renewable generation. Even with these costs, driving our two EV's (Bolt EV and e-Golf) cost us only about 4.5¢ / mile.

Here's the roof panels, on our reconstructed roof (which is still in process):




And the equipment in the basement:




I am really looking forward to our reduced electric bill, and our reduced carbon footprint.

[oil pan 4]

My power costs around 8 cents per kwh.
I plan on putting up solar panels as soon as I get my other house rented. It's about 90% done and I got someone beating down the door ready to move in.
I'm buying the system my self and installling it my self, since I do have an associates degree in applied science for wind and solar power generation and I am working on my journeyman electrician, I'm not letting some shady contractor make thousands of dollars off my install.
Put in about 4kw this year, then another 3 to 5 next year. Do 48v panels and 48v grid tie inverter.
I have heat pump now and hate it because it uses so much power, I have a new coal furnace to install before next winter, hopefully that will provide most of our heat next year.
Still looking to sell our 2000 VW bug, which is our spare car and buy a leaf and make it our primary car for all the little trips around town and drives to work.

I can't see your pictures, am I the only one?

[NeilBlanchard]

Sorry about the pictures - I will upload them to this site, when I can.

Our generation costs are about 14¢ / kWh. Do you you also have distribution costs?

I am looking at a rocket mass stove with a biochar maker, for backup heat.

We are doing all the construction, and roofing, but we had the solar PV system installed. My old roof was an 8 pitch hip roof, and the shingles were failing. We stripped the 3 layers of shingles (about 10,000 pounds total) and removed all the old roof framing. We then used the rafters to double the attic floor joists, and then framed the new 12 pitch gable roof with 2x12's and LVL ridge and valleys. The new roof is a 50 year asphalt shingle.

[oil pan 4]

I just lost a ton of welding related pictures on another site because they were 3rd party hosting them.

I have metal roofs.
The first building is an out building I was going to upgrade the main beam to a steel beam when I find an appropriate one at the scrap yard. Then double up some of each joists with my best salvaged 2x6 boards.
My worst case scenario is we get a bunch of heavy wet snow that drifts on the roof and hangs around the panels, then gets rained on.

[NeilBlanchard]

I fixed the picture links!

[oil pan 4]

Wow that's a lot of panels.
My roof is like a 2 pitch.

[oil pan 4]

What's your voltage?
Are they approximately 30v panels seriesed up for really high DC voltage?
Since that seems to be the standard for grid tie setups.

I am going 48v for 2 reasons, when one cell gets blocked by a leaf, bird poop or a tumble weed it wont cut the entire strings output in half, just the 1 or 2 panels (if seriesed) that get shaded lose power. Only losing 100 or 200 watts instead of 1 or 2kw if not more.
Then as I add more panels and use less power as I change out appliences for propane or more efficient versions. Then some day production may exceed demand and then I might move in a 5 to 8 ton 48v forklift battery, get stand alone inverters, plus charge controllers and go off grid.

[freebeard]

Grid-tied? Did you see this?

https://www.youtube.com/watch?v=NKWo-i-2pUA

Not to spoil it or anything, but...

It turns out that an installation that was signed off on by the installer, the inspector and Jack Rikard hisself was structured such that he was selling power to the grid at 2.4¢ per and buying it back from them at 12¢. ...Across a one and one-half inch shunt. ...For twelve years. He can't be making this up.

Also, where does the excess power go in a buffer overrun condition?

[oil pan 4]

They pay consumption rate for solar power generation here, which is 7 cents per kwh.

In a buffer over run situation the inverter would over volt fault and shutdown. Standard safety feature for all UL approved grid tie inverters.

[NeilBlanchard]

I think our panels are 35V. They each have a micro inverter. There are 3 AC strings that are current limited to 12 panels. My understanding is each panel is independent, so shading cuts out only the panels affected.