Sparkfun Artemis Nano https://www.sparkfun.com/products/15443
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Monocrystalline Silicon Solar Panel 2V 160mA 50*50mm
& 800 Lumen Philips 10.5W bulb 2700K.
The next step is to get the blue light that flashes when it boots with a standard 3.7V battery & recharge the battery at the same rate it discharges. A larger solar panel will easily work, but I had to unplug it because the Nano immediately started smoking, not realizing I was using the wrong 4.4V out with an Adafruit Solar Lipo Charger. Really important tip: Make sure you have the right regulated output or it will fry the MCU
I attended a webinar by E-peas, Epishine & Cap-XX, and found this slide helpful