There are lots of times and places where renewable production is higher than demand. When that's the case "the NPP will always feed all its constant production to the grid to satisfy the constant base load." increases costs.

> increases costs

“Increases costs” for who, the producer, the consumer, the distributor? If you have data on that I’d love to read about it.

I think the article mentions that recently batteries are always together with renewables. The reason this battery was built there has nothing to do with the NPP but with the proximity to the already developed power distribution infrastructure. You can assume they’ve all done the math when choosing to not build batteries next to working NPPs.