Boncuk, thanks for the advice and the battery idea. Researching the BAT85.
The stored electricity won't be used, as the circuit will only run during the day. (The circuit answwers: "Send a radio message if you see the sun.") Could I just discharge the electricity as it's generated? What about a variable-speed fan?
DX3, thanks for your efforts and for the reference to the amp-hour fallacy. Yes, it was aimed at me, the guy trying to fix the tail light on his van.
My nearest power plant monitors how much electricity our county is using. If we're using less, they shut down a generator. If we're using a little more, they add another generator at half speed. I'm trying to do that with my meagre 45 mA.