NASA ANNOUNCED its InSight lander will run out of power in a few months because its solar panels have become covered with many years of Martian dust. Meanwhile, my solar panel is covered with many days of New Mexico dust and fire ash.
Cleanliness is next to wattage-ness
The solar panels we nomads use offer only 12 to 25 percent efficiency when they’re absolutely clean. Any bit of shade or dirt cuts that efficiency further. So if it seems it’s taking longer and longer to recharge your battery or power station, try cleaning your solar panel(s).
I have a single 270 Watt panel mounted on the roof of my van. About once a month or so I spray it (and the van) clean at a car wash. In between I stand in the doorway of the van, pour water on the panel, scrub it with a pad attached to a painter’s pole, then rinse with more water. Those of you in wetter climates might have Mother Nature cleaning your panels for you — at the cost of having less sunlight. But if you have a portable panel, wiping it down regularly is a much easier task.
Not made in the shade
Even the slightest bit of shade across your panel — from roof vents, cargo boxes, antennas, trees — can reduce its output to a surprising degree. Keep shadows in mind when you position your rig or set out your panel. And remember that shadows move.
If keeping your solar panels clean and shadow free isn’t feasible for you, an alternative solution might be adding more solar panels to compensate for the lost power output. The usual rule of thumb for a healthy system is about 1 Watt of panel output per Amp hour of battery capacity. So, like a 100W panel for a 100Ah battery. You might need to go to one-and-a-half to two times more wattage if the panels are going to spend most of their time less than clean. Or you could keep what you have, reduce your power usage, and cope with slow battery charging or batteries that never fully charge, while complaining about solar energy not being as good as people claim.