Things to need:
1. 150 KW Solar Panel pricing Rs.6500
2. 50 AH Battery (Excide, Osaka, Phoenix, AGS etc) pricing Rs.3200
3. Wire (According to your requirements) approximately Rs.500
You can run your 12 volts DC fan whole day direct connecting from Solar Panel, and also can charge your battery with same solar panel while using during day from solar. If your buy seprate 10 Amps Battery Charger, then charge your battery with that for night backup.