The Solar Pi is an idea I had for a project/concept art project: a Raspberry Pi powered directly from a solar panel, hosting a website. When the sun is down, the site isn’t available. There are other solar powered websites out there, but forgoing storage is an interesting idea.
It wouldn’t have to be a Pi, other single board computers could work. The key is that the load is light enough that a solar panel itself can power it without much reserve, over a reasonable period during the day. With a larger panel, even during overcast days you might be able to keep it running somewhat. The idea is to see how useful you can make this without introducing a battery, although I’m considering a supercapacitor to provide enough storage to shutdown gracefully, and handle a single cloud going overhead.
Spiritually, this is similar to things like solar water pumping off-grid: the sun powers the pump whenever it’s out, and you pump water into a tank for use. That’s your energy (and water) storage. Or, a solar vent fan. Conventional grid-tied solar is like using the grid as a battery, although if you time your loads right you can end up using it this way too.
This has gotten me thinking about a couple things. For one, maybe running a mail server too? Email should, in theory, work if a receiving server becomes unavailable. It would be neat to include this as well.
Another idea: what about leveraging something like syncthing? The website could be shared on the Pi, and then others would just download it when it’s online. Not only that, but users could help distribute it as well.
Amusingly, given my home network, the site would probably sit behind a proxy. In other words, another web server and mail server that would relay to the Pi. These would almost certainly be powered from the grid, although I may tackle that as an other project. It kind of takes the starch out of the initial proposal, but from my perspective at least it’s kind of fun to set this all up.