Supercaps
A number of tramway manufacturers are offering battery railcars that combine the traction battery with a supercapacitor that will be loaded at each stop. The main motivation for the usage of battery-powered tramways is to avoid overhead wires across the city. Using boost charging at each stop allows to lower the size of the required traction battery.
The CAF Urbos 3 tramways was ordered for the Seville metro with the Acumulador de Carga Rápida system which uses short overhead wires at each stop for charging. The Seville trams have been operating since Easter 2011.
The Siemens Avenio tramways was ordered for Doha, Qatar with the Sitras HES system with an overhead conductor rail at each stop using a contact shoe instead of a pantograph. The opening of the system is scheduled to be in the autumn of 2015. There is already one Combino tramway equipped with Sitras HES that is running in regular service from Almada to Seixal, Portugal, since November 2008.
Read more about this topic: Accumulator Railcar