Operation Lux has been running over one year on the roof of Elmwood Park taking measurements minute by minute of sunlight intensity. Now that I have a complete years worth of data (less some downtime from last September) I decided to analyze it.
Here are the most important results from the operation—the average amount of light received during a day for each of the months throughout the year. The thick black trace is the yearly average, but as the chart shows each individual month can differ significantly.
Shown are monthly averages of light for the entire year. Clearly visible are the effects of the sun's declination with daylight beginning shortly before 6:00 am and lasting until after 8:00 pm in the summer months, but not until after 8:00 am and only until 5:30 pm in the winter.
Here we see the average amount of light in a 24 hour period for each in watt hours per square meter. Notice how much less light hits the roof in January, December and November than the rest of the year. Factors include the angle of the sun, the tree line around our house, cloud cover, and snow.
So in the summer months I see no problems having my 50 watt solar panel power the web server. But for a couple of the winter months there may not be enough light to keep the server battery from running low. This is why I have designed the Sun Dragon with a relay to switch itself to auxiliary power. This will allow the battery to recharge from solar power for however long is needed. Thus the Sun Dragon may not be 100% solar powered all the time, but it should be close.
During the summer months there is much more power available than the server needs. I have been thinking about what can be done about this. One option is to have the server contribute to some distributed computing projects such as Einstein@Home when there is excess power available. Because of the quantity of power, I may have to add a couple of additional computers to fully utilize this power. This is only a concept right now.