In 1980, after living in the woods of Vermont without electricity for five years, I bought my first photovoltaic (PV) module. Responding to a small ad in Mother Earth News, I sent a check to Joel Davidson, a back-to-the-land urban refugee who was facilitating a bulk purchase of PV panels. From his off-grid acreage in Pettigrew, Arkansas, Davidson was selling 33-watt Arco Solar modules for $275 each.
Many people ask, “How long do solar panels last?” To mark the 30th anniversary of my first PV module, I decided to climb up on my roof and bring it down for testing.
My Arco Solar panel (model 16-2000) was manufactured at a plant in Chatsworth, California. The module was designed to charge a 12-volt battery at a maximum voltage of about 16 VDC. When new, the 33-watt module produced 2.0 amps in full sunlight.
After being exposed to the weather for 30 years, how’s the old Arco module working now?
I decided to test my old PV module by connecting it directly (with no intervening battery) to two different 12-volt loads: a 35-watt incandescent light bulb, and a blower rated at 4.5 amps (about 54 watts).
I ran the test in my backyard, on a sunny day at about 11:30 a.m. The outdoor temperature was about 50°F.
The old PV module passed with flying colors. It easily powered up the light bulb; my Fluke multimeter showed that under a full load of 2.015 amps, the module’s voltage was an impressive 14.93 volts.
The next test was more challenging: I hooked up the 54-watt blower directly to the panel. Wow! The blower started spinning at a fast clip. According to the Fluke multimeter, the blower was drawing 2.5 amps from my ancient solar panel — more power than would be expected from the factory specs.
I described my test to Raju Yenamandra,…