Our solar arrays have been in for over a month now, so let’s check in on the systems.
Moontree Studios (7.1 kW DC power)
So far, things are performing as expected. As much as I want exciting things to happen, the panels are actually kind of… boring. No moving parts to lubricate or replace, just electrons flowing. And boring infrastructure is good, because that means it’s working and we can focus on other things.
Our intention with Moontree is not to take the buildings “off the grid.” While interesting in an experimental sense, there’s not really an advantage in doing so for us. We partner with the grid with a bi-directional exchange of electricity, allowing us to deploy renewable energy at a cheaper cost (therefore, to install more of it). We didn’t spend any money on batteries. At the peak of the day, we are credited for excess electrons that are sent back to the grid and will feed the next available building. When we are running a deficit, we draw from the grid. This arrangement is called “net metering.”
In the end, we expect the Moontree Gallery and Shop to be 40% solar powered, 25% wind, and the remaining 35% by the grid (that’s another post, but you can see real-time grid data here).
Nevertheless, I thought it would be neat to see the solar and wind production data on a single chart. The two systems are from different manufactures, running different software, so it was… tricky. But nothing that a little time with an Excel sheet couldn’t fix! (Just don’t ask me to do this for each day).
Don’t worry too much about the units on the vertical (y) axis. Just looking at the relative values across the course of one 24-hour day.
The orange line shows solar production. The “perfect” curve of solar production we would get on a day with no clouds… the power output steadily rises until midday, plateaus, then descends with the setting sun. On this day, there were clearly a few clouds starting around 11:30 AM.
The wind is a little less predictable. Some days have virtually no wind at lower altitudes. Others are quite productive. For this day, the wind starting picking up around 3:30 PM and provided power through midnight. Again, the nice thing about net metering we as individuals don’t really care when the power is produced, just how much total by the end of the month or year. Each day’s chart will look different.
Wastewater Plant (75.52 kW DC power)
Our less visible solar installation is about 10x the size of the Moontree array. We located it in an adjacent cattle pasture, which we determined was better than any of the alternatives we had examined (roofs, parking lots, etc). Sheep routinely graze under solar arrays in Europe, but cattle are simply too big and powerful (and curious). So after the install was complete, we put up the fence. It was a team effect, and we all learned a little something. The solar production has already “paid off” the financial cost of the fence, and probably the ecological debt of the metal panels and wooden posts.
Following the example of some pioneering solar installations, we plan to eventually replace the pasture grasses under the panel with low-growing native wildflowers to give a boost to pollinators, including the honey bees just down the road at our greenhouse. Solar honey… what’s sweeter than that?!
I took a few readings of the electric meter to make sure everything is tracking properly. We have been pushing on to the grid about 45% more electricity than we have been pulling. That’s a good feeling! And it was as-designed… we will use up these credits on our bill as the days get shorter and cloudier and production begins to drop. After a year, we expect the system to cover about 80-90% of our energy needs for the plant.
Killowatt-hours and voltages and such can get a little confusing. So let’s put it in a more tangible way: in the the first 5 weeks of production, the wastewater arrays have produced enough energy to run my home for about 2 years. Cool!
I look forward to coming back next year with a full year of data. My home array just had it’s first anniversary, so I’ll be posting that data soon.