A train accelerates, carries energy in its motion and can return some of it during braking. Can Wan and colleagues ask a question different from that of an onboard battery: could this flexibility become a resource for the electricity system? The interest lies in looking differently at equipment that already exists, rather than announcing a miraculous new material.

Calculated potential, not an installed fleet

The authors analyse railway operations and model their possible contribution to balancing electricity. Their global estimate of 190 gigawatts for 2025 represents potential power. It is neither a measure of stored energy in gigawatt-hours nor the power of installations already connected to provide this service.

The publication is a peer-reviewed, accepted version released before final production. Its recent availability does not turn modelling results into a commercial demonstration. Extrapolations depend on assumptions about grids, train operations and investment.

Passengers must not become the adjustment variable

Our analysis: the value of this approach would depend on its compatibility with safety, punctuality and transport capacity. An electricity saving would lose its relevance if it degraded the service expected by passengers or freight customers. Grid benefits must therefore be examined alongside railway constraints, not separately.

It would also be necessary to identify who controls this flexibility, who benefits and how it is paid for. An international study does not, by itself, settle each country’s operating and market rules. It does not mean French trains already participate in a new storage service.

A complementary option to test

The finding is interesting because it invites comparison between using existing assets and building new installations. That comparison must include full costs, losses and the resource’s actual availability. High theoretical power does not show how long it could be used when the grid needs it.

For readers, the next useful signal would be a documented trial demonstrating both an electricity service delivered and a railway service maintained. Data, methods and limitations should remain accessible for independent assessment.

Conclusion

Rail could become a more active partner of the power grid. The study opens a research and planning avenue; it does not yet demonstrate lower prices or operational giant-scale storage.