Thursday, June 29, 2017

Suburban 5-4-and-a-door Solar: Day 1

Two weeks ago, we finally got the electrical systems installed for our new solar panels (see more here).

A week ago, we got the formal inspection approval from the city.

Two days ago, after waiting a week for a call from Georgia Power, we called them to see if they were planning to come out and flip the switch to turn on the power. We discovered that (1) we could have turned on the power at any time, Georgia Power just might have seen some alarms that caused worry and (2) as of that morning our meter had been reprogrammed and we were welcome to turn on the power ourselves.

Which we did.

It took a while to get the wireless interconnection to the smart meter established, and the system needed to sit for a while to discover the panels. That meant that yesterday was our first full day with the panels online and the ability to watch them work.

We have been told that within the next week or so, the full internet capabilities will become available. The installer has to do some back-end work to set up a correlation between the readings and the panel locations, and we will have all sorts of fun data to play with when everything is complete. Not being an especially patient people, we logged into the system directly and spent the day watching production numbers. As the productivity of our system went up, our own productivity went down due to irrational exuberance over the numbers coming from the panels.

By the end of the day, we had collected about 200 power generation numbers. Without further ado, here's what they looked like over the productive hours of the panels.

The maximum power generation recorded was just over 5.5kW, which we were told would be about the maximum (AC) generation for our system. (The DC rating is about 6.9kW.) Those dots below the curve were probably clouds passing in front of the sun. Most of them lasted only a few minutes, and it's good to see that production didn't drop completely to zero.

At the top of the curve, we went out to our meter to watch it spinning backwards. It's a digital meter, so no spinner, but we could watch the LCD lines moving from right to left. Generally, we'd prefer not to sell power back to the grid since the pricing setup in Georgia isn't in our favor, but yesterday was a very bright day with moderate temperatures. When the real heat sets in, we probably won't be selling back much if any.

Doing some discrete integration on the curve shows that we generated around 27.5kWh during the time that we measured. According to Georgia Power, our peak usage in the summer is around 40kWh, rising to as much as 70kWh on some days. So it looks like we generated just over half of our needs on a typical peak summer day and a little less than half on a really hot summer day. But that's an oversimplification, of course, since no power is generated at night when we turn on the lights and the Netflix.

What does this mean for our power bill? It's too complicated to know right now, since power generation and consumption varies throughout the day. We should know more in a month and get a better view over the next year.

Today, we're not watching as closely since we have real work to do. We'll probably start watching again when the internet apps are enabled, but I suspect that this will all just be commonplace in a few months. Which is the point.

For a full list of articles on our solar panel installation, click on the "solar" keyword below.

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