Equinox

Equal day and night.

Today (22 September) is the fall equinox – when we have equal amounts of the day with sun and no sun. The length of the day is changing fast – indeed, faster than any other time of the year except spring equinox – and it is really noticeable every day. Today was rather cloudy, not a great day for solar power:

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Spring equinox

Spring is here in the valley.

Today is the vernal equinox – the spring equinox – when the length of day and night are equal (equi = equal, nox = night). Actually, “They are not exactly equal, … due to the angular size of the Sun, atmospheric refraction, and the rapidly changing duration of the length of day that occurs at most latitudes around the equinoxes” [Wikipedia]. Here in New Hampshire, Sunrise was at 6:51am, Sunset at 7:01pm.

For those who welcome the arrival of spring, today is when we are adding more minutes of sun per day than at any other time. We’re on the steep part of the curve! This is great news for our solar tracker, which put in a banner effort today under nearly clear skies, with a total production of 45.57kWh:

Technically, the equinox is “the instant of time when the plane of Earth’s equator passes through the geometric center of the Sun’s disk” [Wikipedia]. This year, that occurred at 0937 UTC, or 5:37am here in Lyme, which happens to be about when I got up this morning.

Interestingly, it has long been noted this is the “day when the Sun rises due east and sets due west, and indeed this happens on the day closest to the astronomically defined event.” [Wikipedia again].

On cue, the Connecticut River decided it is also ice-out day – the day the winter’s ice breaks up and the river begins to visibly flow. I’m pleased to see open water, because it means that bald eagle might be seen more often in our neighborhood once again, now that it has an opportunity to fish.

ice-out on the Connecticut River, in front of our house

The forecast shows nothing but clear skies, warm days (50-60º) and cool nights (20-30º). Great weather for sugaring! More on that to come…

Solar flat

Even on a windy day, we can still generate power.

It was a wild and windy night, as a cold front blew away yesterday’s warm temperatures. Our solar tracker is designed to protect itself by going flat when there are gusty or strong winds, and that’s how I found it this morning.

Solar tracker goes flat in windy conditions.

You can see the anemometer at the far-right corner, which is on a gimble so it can measure horizontal wind speed even as the tracker tilts.

That picture was taken about two hours ago. It’s now quite sunny, and still windy; the tracker is still flat (and thus not pointed at the sun), but still generating enough power to serve the house, charge the battery, and feed the grid:

Solar complete

Solar and battery and generator.

Finally, more than six months after we received the initial proposal from a local solar-power company (Solaflect), we have a complete system installed: last week, they completed the installation of a battery back-up solution from a German company called Sonnen. Our house can now be supplied by solar power, grid power, battery power, or propane-generator power, depending on the situation. Although I won’t dig into all the details, it’s pretty cool, so read on…

diagram of power flowing
A screenshot from the Sonnen battery portal showing power flowing from the solar tracker into the house (supporting its consumption) and into the battery (keeping it charged) and into the grid (selling power back to the electric company). The actual graphic is animated, showing power ‘flowing’ from the top to the other three destinations.
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Solar power

Now I can charge my car with the sun.

One of our other major summer projects was the installation of a solar-panel tracker from Solaflect Energy – a local company from Norwich, VT that designs, builds, and installs its custom solar-tracker system in households and small businesses around the Upper Valley. We’ve been interested in going solar for years, and finally decided to take the plunge. As an added bonus, it (indirectly) serves to fuel my new Tesla. Read on!

The Tesla can now be charged by Solar power.
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