Yesterday was the first full day of Solar Panel operation. The panels themselves went online Nov 30th about midday.
The website and the mobile application provide pretty nice insight into the system status. What’s very cool is that I can see individual panel production and therefore can see if a panel is having trouble.
I’m figuring that we’ll run for several months before deciding if the system needs to be tweaked or if adding battery backup would be something useful.
One of the things that was befuddling me when we got into this, was that a solar array of interconnected panels would only produce power skewed to the lowest common denominator.
In other words, the laziest panel on the roof would drag all the other panels to its level not the other way around. When I was a kid playing with Radio Shack solar panels, this effect really annoyed me. I kept adding panels to a small array but the voltage never increased above the output of my oldest little panel. Oddly and very confusing to my little child brain taking that oldest panel out of the circuit, then measuring I’d see the best output from the next lowest producing panel and so on.
I could see the pattern, but couldn’t explain what I was seeing. I hadn’t really thought about it until we began this project.
I’d seen a similar effect with my portable panels while recharging battery packs, but it was so negligible in that application that I’d just shrugged and moved on to something else I was doing around the house. In that case, either way, the battery pack would be recharged in 3 or 4 hours, so the impact wasn’t a big deal.
When you’re talking about a large array on your roof that’s costing you money and it’s supposed to lower your electric bill you kinda want to know these things. Well, at least I do.
I was really confused on Wednesday, when I got a look inside the “Controller box” mounted on the wall of the house. I was expecting to see a D/C (Direct Current) to A/C (Alternating Current) conversion device, but what I saw instead was more or less standard A/C connections and breakers.
The mystery deepened, I did see a coil of the type that’s used to detect current flowing through wire. In fact it had a single wire running through it. That wire went to a grounding block, the coil itself was connected to a small digital circuit board mounted at the very back of the controller box. This board was in no way going to be capable of handling the kind of power that could be coming from the panels on the roof. Looking at it, I thought, “That much power would turn that board into a burnt green popcorn kernel.”
The mystery deepened. The installer had no information about the details. He was just finalizing the A/C hookup to the house. But I saw inside the Controller Box, a makers logo.
“To the Internet, Boy Blunder!” Yeah, as a kid in the 1960’s I watched “Batman” and I read “Mad Magazine”. What of it?
When I got to the manufacturer’s web site. All was revealed.
Turns out, each panel has its own inverter attached to it. Meaning the D/C to A/C conversion is done at the panel. As I read the specs and dug into the installer side of the website I sat there going, “Duh!!!”
The design is brilliant. Since the power coming from the panels is already A/C it’s just a matter of connecting the array to the house A/C (with some safety features of course,)
Electricity flows a lot like water. If there’s more electricity coming from the house then it flows back into the grid. This is a gross oversimplification but it’s easy to visualize.
Since the D/C to A/C conversion is done on panel, each panel can produce at its own rate without the other panels affecting it, or it affecting the other panels.
That mystery was solved, so what is this controller doing?
It’s talking to each of the inverters on the panel, and then sending that data to me, and sending it to the installation company so they can address any warranty issues and they’ll know if a panel needs servicing. It also allows accounting. Since the system knows how much power each panel is producing, and therefore what the array is producing the Electric company can’t get away with “fudging” the numbers about credit owed.
The Controller monitors how much power we use, how much power is produced, simple math calculates the difference. It’s the difference that gets sent back to the electrical grid for the power company to “purchase” from me as an electrical producer.
The Controller also provides for the addition of battery backup, and would manage a switchover if needed due to a power failure.
Another thing I didn’t realize was that if the main power goes off and I don’t have a battery backup, I’ll still be without power.
I understood that I’d be without power if a power failure happened at night, but I thought if the power was off during the day, I’d still have my fridge and essentials running. That’s not the case.
Thinking about it it makes sense. It’s a safety feature. If I’m generating power at my end and feeding it back into the main electrical grid, then the electrical linemen could never work on the power lines. The lines would always be powered up until each house with solar panels was physically disconnected from the grid.
The Controller box handles that automatically in the configuration I’ve got installed.
I’m thinking that a battery pack is probably in the future.
I don’t want the hassle and noise of a gas powered generator running during a power outage.
When the inspection was finished, the solar guy pulled off the protective plastic on the controller box and voila the manufacturer’s logo is now visible.
I knew I shoulda peeked under that protective plastic film. I’d have been able to have my questions answered a lot sooner!
Now I just have to wait. A couple of months of runtime data and I’ll be in a better position to decide if I need to add a couple of panels and what size battery pack I’ll need to install.
I’ll also need to figure out if making those modifications will add to the overall value of the house if I decide to sell it.
I also suspect that if I leave California, where-ever I move to, I’ll be installing Solar probably with batteries because I like the idea of being able to sail through power outages without really noticing them.
I don’t like to be inconvenienced!
Call me a snooty, spoiled, first world person if you like!
