We are only at the beginning of the development of a smart network for charging electric vehicles, particularly in major cities. This is demonstrated by the innovative project developed in Madrid. The city has indeed seen the inauguration of the first "Metrolinera" — a charging station for electric vehicles that uses the electrical energy produced through the regenerative braking of trains running in the underground metro network.

The first charging station is located outside the Sainz de Baranda metro station on lines 6 and 9 of the Madrid underground, and will operate free of charge from 8:00 to 21:00 every day from Monday to Friday.

Train2Car, as the project is called, saw a wide-ranging collaboration between the Instituto Catolico de Artes e Industrias (ICAI) of the Universidad Pontificia de Comillas, CIEMAT (Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas), and the companies SICA, Siemens and Citroën Spain.

Having begun back in 2011, with the replacement of old trains with new regenerative braking carriages, the metro today produces electrical energy when trains slow down or brake. This electricity is channelled and stored in special batteries before being distributed to the charging network.

A perfect example of what is known as a smart grid — a network capable of producing energy in a non-conventional way and of distributing it wherever it is needed. The "Metrolinera" will allow electric car batteries to be recharged in around 20 minutes. If the test results prove satisfactory, Metro de Madrid has committed to installing further stations at various locations across the city.