Hi,
My name is John Lester Soronio. I am a senior design engineer and working as project lead for many electronics design project released in the market.
I can give you some simple options for this project:
1. Water level sensor using only the conductivity of water and three 2 LEDs
2. Battery charging solution using solar panels
3. Switch Mode Power Supply
3. Boost converter, buck converter, flyback, forward, LLC, etc
4. Charger design with constant current nad constant voltage
5. Low standby power consumption circuit
6. Over current protection circuit
7. Curren level monitoring circuit and display in RGB LED
ETC...