Summer Solstice

Maximal sun makes maximal power.

Today is the summer solstice in North America, so I was especially interested to see how our solar tracker managed on the longest day of the year. A few weeks ago we doubled our battery storage so we could extend our independence from the grid. Given the extended daylight (15 hours and 27 minutes, from 0507–2034), and the extra battery, the batteries can now last through until sunrise. Although today’s weather was not purely sunny, the system produced over 50 kWh.

In the graph below, the green line shows the battery level declining in the early hours, and climbing after sunrise. The dark blue region shows the house consumption, and the gold region shows the excess solar production… used first to replenish the batteries, and then, after 2pm, to feed back to the grid.

Today was a good day… but not the best day yet. Two days ago was more sunny, and we set a personal record for solar production: 58.58 kWh:

Author: dfkotz

David Kotz is an outdoor enthusiast, traveller, husband, and father of three. He is also a Professor of Computer Science at Dartmouth College.

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