Six Days of Solar Power Summary

Morning system wakeup. Battery voltage at top. Red and blue lines at bottom are panel and charger amperages.

We lost power at 3:30 pm on September 10, 2017, as the outer bands of hurricane Irma, impacted West Palm Beach. Because of the extreme weather conditions, little if any power was being generated from the rooftop panels. The system switched battery power off at 3:30 am. when battery voltages reached the low-level cutoff of 46 volts. energy was directed to the batteries to bring them up to charge.  When they reached a level of 50 volts, the system restored power to the house and also when the sun came up the next morning, all of the solar panel output continued 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 squeezzed 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.

Hurricane Irma and my photovoltaic system.

 

Hurricane Irma came through Florida the weekend before September 11, 2017 and did massive damage throughout the state.  It lost its tropical characteristics after 11 days and traveling 4,000 miles.  Half of Palm Beach County, 500,000 people are without power.

 I am running completely on my photovoltaic system and have been for two days now.  This is the first extended operation of my system in emergency mode and it has been interesting.  We, my step-daughter and her husband, sheltered in place.  We lost power at about 3:30 in the afternoon on the day the storm went up the west coast of Florida.  The system switched to battery backup which carried us into the next morning until about 3:30 am.

When the sun came up the next morning, the charge controllers directed all of the energy from the solar panels to the battery bank.  We had no power in the house while that was taking place.  That was because we lost power in the afternoon and it was cloudy and stormy.  Also, we didn’t have a good idea of how to manage our consumption.  My children have returned to their home so I will be consuming much less tonight.  It will be interesting to see how things perform.  With careful management my house is powered for about 12 hours on the battery backup.

So, what can I run on emergency power from the solar panels and/or the battery backup?  Pretty much everything in the house except for air conditioning.  With the tight envelope this house has, impact glass windows with low-e reflective glass and good insulation in the attic, the house stays around 80 – 83 in the day and cools down at night.  It’s quite comfortable sitting under a ceiling fan.  I am definitely not uncomfortable or suffering.  This, after all, is what we designed and implemented the system for.  It is basically functioning as a generator would, but with no noise or fuel.  Additionally, it runs every day all year long, generating power.  It will eventually pay for itself while a generator never would.

 

Lots of Watts

Yesterday was so clear and cool that I think the charts from my house might represent an ideal system maximum for March 17th at this location. March 16th, the day before yesterday, was almost identical.

This chart reveals that night time usage runs around .5 kWh.  That’s got to be phone chargers, DVR, and some other “phantom” loads from various small electronic devices that are plugged in.  The increase in usage just before sunrise is my irrigation system coming on.

The percentage of total electricity used from my solar panels was 108.  Yesterday and the day before the totals generated for both days were exactly 24.7 kWH. That’s why I think this is a good measure of the maximum my system can generate under ideal conditions in mid-March.  Because of differences in my usage, there is a slight difference in the percentage generated for yesterday and the day before.

 

 

 

The last ten days are shown below in both graphic and tabular form. So far, we have had three 100 percent plus days and one 90 percent plus day.

Worst Case

Yesterday, March 3, 2107, was overcast and gray all day long.  We even had some light showers.  It was probably a worst case day for solar energy generation.  Even so, we generated 28 percent of our energy from the sun.  This ends. a series of very good days up in the 80 percent range.  Our best days are ahead in the months of April and May.  My energy efficient window replacement project should be done by then so I am optimistic about how well the system will perform then.  The time-lapse for the day reveals some opportunities for generation were available in the morning.

Worst Case Scenario

January 29, 2017, was cold, cloudy, and rainy, a worse case scenario for our photovoltaic system.  I stood the chill as long as I could, but finally gave in and turned on my electric heat.  Because of the clouds, our solar panels only generated 1.9 KWH of energy while the heat used over 30 KWH.  The percentage from solar shown in the chart is the result. The chart below shows a very atypical day where all of our energy came from the grid and none from our solar panels.

The chart below shows the last ten days of percentage from solar. We were doing quite well actually until the cold front came down and stalled over us.

A Productive Winter Day

Almost a perfect day for solar yesterday. A/C was off most of the day. Ran it briefly during the night to take the humidity down a notch for sleeping. These are still the shortest days of the year.  Firstly, you see my daily percentage meter for yesterday, followed by my hourly consumption chart.   At the bottom of this post,  is the time-lapse video for the daylight hours yesterday.  You can see that the day was not unusually clear.  The temperatures were mild so the A/C was off for most of the day.  I turned it on briefly in the evening to drop the humidity, you can see that in the hourly chart by the noticeable increase in grid consumption around 11 pm.   My irrigation system also ran in the early hours of the morning.  Notice in the time-lapse,, that the sun is still very low on the horizon and is hardly visible in the video.

2016 Year End Analysis

Here’s the histogram for last year’s daily percentage electricity from our solar panels. It gives a good overall picture of the characteristics of our system.  The year started with unusually high consumption for a variety of reasons.  Nevertheless, you can see that we had more days above 50 percent than below.  With more increases in efficiency, I should be able to shift that peak some more to the right. You can mouse over the bars to display individual day values.