Finally, after a few weeks without sunshine, the weather cleared up and the sun was shining brightly and the batteries on my solar energy system finally got some serious charge, reaching close to full charge by Friday afternoon. It was also the ideal time to take current measurements and figure out what should be expected of a solar energy system in different weather conditions.
For optimal energy production, a solar panel should be inclined about 30 degrees facing south. The panel I used is installed on a roof deck tent structure which is currently not an ideal position for a solar panel. It is facing east more than it is facing south, thus, solar energy production is highest between 10AM to 12NN and would start to decrease by 1PM. That means I should soon modify the roof deck structure so that the panels are in the ideal position.
I took various measurements of the current going into the batteries when the clouds cover is very thick, when there is just a thin layer of clouds and when the sun is fully out. This week, I was taking measurements between 10AM to 12NN so I can compare the results for various cloud coverage.
When tropical depression Agaton was still in full swing, cloud cover was very thick and the sun was never out. In a previous issue, I measured about 0.4 to 0.7A at about 4PM. I measured between 0.6A to 1.1A between 10AM to 12NN.
Last Thursday and Friday, the cloud cover was such that the sun would be fully out for a few minutes then get covered again. The highest current I measured when the sun is fully out was 4.5A, which is close to the maximum expected current from the panel.
When there is some cloud cover, but not very thick clouds, I measured between 1.9A to 3.1A.
On Saturday, the sun was mostly out with minimal cloud cover in the morning. However, I was surprised to find that the maximum current I could measure was 4.0A. After some research, I found out that solar panel energy production is reduced by increased temperature. So the difference in measurements from Friday is likely due to the higher temperature of the panel on Saturday because the sun was out most of the time. On Friday, the cloud cover kept the panel cool and when the sun is fully out briefly, the panel is still cool and generated more current.
So taking the conservative results, I am concluding that:
- on very cloudy weather much like that during the past few weeks, energy production of a solar panel can be about 15% only from the expected production during sunny days
- thinner cloud cover can reduce the energy production to about half
- hot days may mean that energy production can be reduced slightly even if the sun is fully out due to the effect of temperature on the panels.
The next step for me now is to put some load on the panels and observe the performance over time. After taking measurements of various electrical loads at the office, I found a possible set of loads for the real-world testing. This will be our lighting for our right of way and the perimeter which is controlled by an optical switch so it turns on when it is almost dark and turns off when it is bright enough in the morning. During daytime, there will be no load so the batteries will be charged by the panel.
Solar Energy Tips:
- Best position for solar panels is to make them face south with approximately 30% incline. This position will result to an overall maximum energy production throughout the year.
- Dust and dirt that accumulate on the panel will reduce energy production. Regular cleaning should be planned, especially in dusty locations.