Coolest thing I've read today (so far)
Every time a train rumbles to a stop, the energy generated by all that friction is converted to electricity, which is fed through inverters and distributed throughout the subway system. One-third of that powers the trains; the rest provides juice to station amenities and a growing network of EV chargers. https://grist.org/transportation/barcelona-is-turning-subway-trains-into-power-stations/