JR East prototype flywheel energy storage

[kuro68000]

https://trafficnews.jp/post/119400

https://www.jreast.co.jp/press/2022/20220607_ho01.pdf

 

Looking at the document it seems that it sits by the side of the track and recovers energy when the train uses regenerative braking, then releases it again when needed. It's a clever idea, the flywheel is not on the train where it could cause problems taking curves or add extra weight and take up space. I wonder how much modification the trains need to support it.