12 hours of night time is not 30TWh The world is currently at 26TWh A DAY

https://en.wikipedia.org/wiki/Electric_energy_consumption

Let's say it is 30Twh a day in 2030 - you can calculate 50% less energy usage during night making it 20 TWh during daytime and 10Twh during night time. This excludes large wind farms that add to base load if you average over the world. There is always wind somewhere around you.

Realistically if we reach 5Twh storage we are able to be >90% renewable.

Having 5Twh of storage is of course not an easy feat if estimates are correct we will have 6.5TWh battery production in 2030. If we amount for 10% of that used in grid storage we would need a decade for a 90%+ renewable grid. There is no faster method. It is realistic.