December 5, 2017 · solar vallibus energy

Solar PV installation complete

The gentleman who did most of the remodelling of my house several decades ago had intentions to fill the roof with solar panels, and designed it accordingly. At the time, solar photovoltaic (PV) was far more inefficient and much more expensive than it is today, but he had a lot of foresight. Circumstances took him elsewhere before ever seeing that project through, but I've picked up where he left off.

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I worked with Baseline Solar Solutions, a bunch of really smart, hardworking VT grads out of Blacksburg, Virginia. It was a little far afield for them, maybe the furthest install they've done from their home territory, but they came down in two trucks and banged out the whole thing in about a day and a half, including coordinating the local power utility and the county inspector. They did a stellar (get it?) job, and have my full recommendation.

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Based on budget and projected needs, I went with a 19-panel, 5.7 kW system, with an option to add another eight panels later on for an 8.1 kW system. It's a pretty bog-standard "grid tie" system, meaning the panels feed an inverter, and the inverter feeds the power generated directly back into the grid. The utility credits me at the market electricity rate, around $0.09/kWh through BVU Authority (which in turn gets its power from the TVA).

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The panels are mid-range Canadian Solar models (don't let the name fool you, these were made in China, no part of the panels have ever been on Canadian soil), and the string inverter is the latest SMA Sunny Boy model. It supports up to three "strings" of solar panels, of which I'm only using two, with nine panels on one, and ten on the other. The unique selling point of the Sunny Boy line is its "secure power supply" feature, which allows it to drive a standard 120 V outlet at up to 2000 W while the sun is shining, with no batteries or other hardware needed. This means that even without batteries, in the event of a power outage, there's some opportunity to have power during the day. As a work-from-home sysadmin, this is sorta important for job security.

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Being a giant geek, of course I track the power production through SMA's portal. So far I've seen it peak around 1PM at ~2300 kW, less than half the theoretical capacity. Keep in mind, though, that the array is tilted the wrong way in two axes. The roof faces northeast (ideally should face due south, but it's difficult to turn a house around), and the northern hemisphere is only a couple weeks away from winter solstice. After 12/22, it'll slowly start turning back towards the sun, and production will rise.

I don't like that there's not an application that directly connects to the inverter without having to travel through the internet and across SMA's servers first, but the "cloud" is just the model everyone uses nowadays, for better or for worse. Besides, the thing has USB and RS-232 connections. I'm confident that if I get motivated enough I can read the data out directly.

I've got some thoughts on tweaks and hacks of the system, but for now I'm in monitoring mode, and probably won't touch this again for many months.

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