Here is a 3D model (kicad 3D view) of the Energy harvesting module.

It is based on a BQ25504 Energy Harvester (with MPPT and Battery management), pair with TPS63030 Buck/Boost Converter. It's perfboard/breadboard compatible.

There is also a 1V precision voltage reference.

You can adjust the parameters (Under & Over voltage protection, Output voltage...) by changing the value of some resistors.

I also made a breakout board for BCAP0350 E270 T13 Supercap (350F, 2,7V).
It's also perfboard/breadboard compatible, but you can use M3 Mounting Hole as terminals if you want (for high current).

There will be more details (explanation and schematic) on the main project page.
I still have to do the other modules (I2C motor driver, sensors...) before I can order PCBs and components (and wait for my salary).
I also have to open a GitHub repository to share files and documentation, but I have never used it ...