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The hardware section mentions: > disaster.radio nodes are capable of functioning in most moderately sunny locations I live in Northern Europe (54N) and wanted

by fyfy18 7y ago

The hardware section mentions: > disaster.radio nodes are capable of functioning in most moderately sunny locations I live in Northern Europe (54N) and wanted to use an old phone as a time lapse camera in a remote location without power or internet (hence the phone rather than something like a Raspberry Pi). The battery when fully charged would last ~3 days, so I just needed a solar panel big enough to keep it topped up. I figured a 20W solar panel would be sufficient, as most phones use way less than that when charging. In my initial testing in direct sunlight this panel was barely able to keep the battery % the same, let alone charge it. I'm not sure whether I just needed or a bigger panel, or it was just the 20W solar panel I got from eBay not really being 20W. If anyone has any experience with this I'd still like to do the project :-)

baroffoos 7y ago
The rating for a panel is the absolute best case where it has full direct sunlight and the panel is cold. Most of the time you will be getting less than the rated power.
walrus01 7y ago
That will almost certainly need a much bigger panel. If a phone is a 3W constant load, that's 2232Wh in a month, except in summer there is no way a nominally 20W cheap PV panel will keep up with that from October to March at latitude 54. Combination of short daylight hours and overcast weather so rarely any direct sunlight. The 20W rating is at what is called standard test conditions, basically equivalent to direct sunlight in the Arizona desert. You'd probably want at least a nominal 180W panel and a basic 25 Euro PWM PV charge controller.
adrianN 7y ago
In Germany, the solar panels in commercial installations produce about 10% of their peak wattage averaged over a year. I guess these are installed in locations with good insolation. So at best you could assume some 2W on average from your 20W panel. But if it didn't even work in direct sunlight, the panel was probably broken.
- pbhjpbhj 7y ago
  In theory, couldn't you boost the input light by using a couple of mirrors (one capturing light below the panel, one above the solar-incident light shining down at a Summertime angle?) or some carefully position Fresnel-style lensing? Is polarisation of the reflected light an issue?

by fyfy18 7y ago

baroffoos 7y ago

The rating for a panel is the absolute best case where it has full direct sunlight and the panel is cold. Most of the time you will be getting less than the rated power.

walrus01 7y ago

That will almost certainly need a much bigger panel. If a phone is a 3W constant load, that's 2232Wh in a month, except in summer there is no way a nominally 20W cheap PV panel will keep up with that from October to March at latitude 54. Combination of short daylight hours and overcast weather so rarely any direct sunlight. The 20W rating is at what is called standard test conditions, basically equivalent to direct sunlight in the Arizona desert. You'd probably want at least a nominal 180W panel and a basic 25 Euro PWM PV charge controller.

adrianN 7y ago

In Germany, the solar panels in commercial installations produce about 10% of their peak wattage averaged over a year. I guess these are installed in locations with good insolation. So at best you could assume some 2W on average from your 20W panel. But if it didn't even work in direct sunlight, the panel was probably broken.

pbhjpbhj 7y ago
In theory, couldn't you boost the input light by using a couple of mirrors (one capturing light below the panel, one above the solar-incident light shining down at a Summertime angle?) or some carefully position Fresnel-style lensing? Is polarisation of the reflected light an issue?