GW is a unit of power, it’s not a unit that energy storage capacity can be measured in.
As far as 17GW of battery, the only technology shipping at that scale is lithium ion, and all lithium ion grid batteries are designed for 30 minutes to 4 hours of duration at maximum discharge.
The idea of a week long battery is not a realistic one at this stage. With Texas' excellent solar resources, it may never need long-duration storage, whenever/if that tech gets developed.
> we haven't figured out a good way to store electrical energy.
Before batteries solve all the problems in the grid, they get installed in smaller amounts. We are in the "smaller" amounts, even though small isn't that small actually. And even 17GW with 2 hours duration can help massively with congestion on transmission lines.