Log In | Register
Skip to main content
Topic: Some solar considerations... (Read 6 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.
Some solar considerations...
Yahoo Message Number: 2531
To elaborate on a previous reply, I wanted to bring up a few more points about solar panel use and expectations, for those who do not yet have them. This is old news for those that do:

- Rated output. The wattage of a solar panel is a maximum extracted from a curve of its Voltage vs. its Current, measured at a standard 'one sun' at room temperature (25 C). For a typical useful crystalline silicon panel, the open circuit (zero current) voltage of a 36-cell unit is about 17.5 Volts under these conditions, dropping to about 17 Volts at the max power point.

For this technology, the output voltage drops as the light drops, but especially as the operating temperature increases.
Conversion efficiency is about 14%, which means 86% of the solar power absorbed by the panel is heat. Since it may additionally be 80 F outside or more, the panel is rarely running anywhere near the room temperature at which it is rated - so the voltage falls.

The current capacity of the panel does NOT fall off as the panel heats up, but if the voltage drops to below what is required to charge the battery, this is irrelevant for that purpose.

- Solar exposure. When siting in a campground, the solar panels require you to carefully seek FULL exposure to the sun for the maximum part of the day, if you want them to have useful output. Even the tiniest shadow of a leaf will kill the solar charging. On a hot day, this is where you will be very happy you chose a Lazy Daze, since the ventilation is excellent in all their models.

- Now a note for those who intend to have a tilting arrangement for their panels, to increase their output - particularly in winter. This is very effective, but in siting, orientation too is critical. It may be hard enough to find a site with full exposure, but now you have to limit it further to those that allow your tilting panels to face due south! This is not a problem in Quartzite.

Steve
2004 FL
2013 Honda Fit