Jean-Francois Reynaud, Product Development Manager – CAF Power & Automations
Catenary free tramways with Energy Storage System: next trends
In recent years there is an increasing interest for catenary-free tramways with the objective of reducing the visual impact of the catenary, especially in the historical urban areas. The tramway manufacturing companies have answered to this demand with two principal approaches: ground level power supplies and on-board energy storage systems (OESS), or a combination of both systems.
CAF Power & Automation is a pioneer (with systems in revenue service since 2010) in the development of OESS-s. The OESS product of CAF P&A, is a hybrid solution integrating ultracapacitors and batteries. This OESS solution answers effectively to another market demand, the reduction of the energy consumption bringing important additional benefits, such as reducing the infrastructure costs and eliminating catenary maintenance tasks. The ultracapacitors, due to their high cyclability are used in nominal operation and the batteries are used in non-expected situations as an extra energy supply, for example in traffic jams. In both cases only well proven cells based on the latest energy storage technologies are integrated in the OESS.
Although the ultracapacitor technology has made significant progress these years, the major breakthrough has been the introduction of the lithium ion batteries. This technology improves considerably the cyclability and the output power of the previous batteries (NiMH), and thus introduces a new degree of freedom to achieve an optimum sizing of the OESS. This sizing has to be customized for the duty cycle of each profile and has to consider the limitations of each technology: temperature control, charge/discharge power as well as the end of life estimation.