Six Days on Solar Power

17 Sep

We lost power at 3:30 pm on September 10, 2017, as the outer bands of hurricane Irma, impacted West Palm Beach. At that time, due to the extreme weather conditions, little if any power was being generated from the rooftop panels, but the system switched instantly to battery power (120 volts from the inverters to all emergency circuits).  We continued on battery power until  3:30 am. when battery voltages reached the low-level cutoff of 46 volts and the charge controllers switched the system off.

The next morning after the sun came up and the panels started supplying power, energy was first directed to the batteries to bring them up to charge.  When the batteries reached a level of 50 volts, the system restored power to the house, while continuing to bring the batteries up to 52 volts.  At that point, the system switched to float to maintain the batteries at a fully charged state through the day while supplying power to the house, including two refrigerators, lights, ceiling fans, and TV.  As the sun went down, the system switched to the batteries as the source. The second night the system shut down at 6:30 am when the batteries again dropped to 46 volts.

For six more days the process continued but with no shutdowns due to reaching the lower battery voltage limit.  With a little more care in usage, I was able to have continuous, uninterrupted power for four more days.  Power from the grid returned in the afternoon of September 16, 2017.

Early in the morning on September 16, I became over confident about how much I could run while on battery backup. While still running on the last of the battery power, I started a load of laundry, made toast and coffee, and squeezed out the last of the battery reserve. Had I waited until the sun was fully up, I would have been okay. The charge controllers shut off the house at the low voltage threshold and directed all of the energy from the rising sun into topping off the battery bank. As soon as the batteries get up to around 50 volts, the house was powered up again.

All around me during the six days the grid was down generators were running noisily with their owners refueling them every few hours.  In conversation with my neighbors, I found their noisy generators were running no more circuits in the house than I was.  There was one exception, one neighbor was able to coax his air conditioner online for a couple of hours by shutting down all other circuits in his house.

I would say that my grid-tie photovoltaic system with battery backup performed exactly as it was designed to do.  I was able to run two refrigerators, all lights, ceiling fans, and 60 inch Samsung TV.  All of my lights are LED lights except for one halogen light which I avoided using.  I am most appreciative of the design work by Roger Messenger and the great installation by Mike Vergona and his crew at Urban Solar.