Description
A novel TVS scheme is being developed for new Metro lines to be implemented in Athens. The scheme is based on less TVS equipment than in typical metro stations, resulting in minimized energy consumption. The principle is based on the state of the art traction systems of these new projects that return the trains’ braking energy back to the 20 kV city grid instead of consuming it as heat on train on-board resistors and this reduction of heat production in stations and tunnels allows the elimination of underplatform and overtrack exhaust systems in the stations, leading to only natural piston effect induced ventilation during normal operation. TVS fans are temperature activated in extraction mode only when necessary, without compromising the temperature and comfort limits in stations and tunnels. In parallel, an overplatform supply system is necessary to provide fresh air to the platforms which are separated by full height platform screen doors from the tracks. As an overall result, both the TVS capital cost as well as the energy required to drive the TVS systems is significantly reduced.
Furthermore, within the above context, strict civil works restrictions and limited street level area availability in certain central stations resulted into elaborated station designs with minimal footprint with only one “double” TVS shaft incorporated within each station, with 4 parallel TVS fans and an independent air intake path behind the platform screen doors balancing the air extraction from the TVS fans.
Simulation results confirm the feasibility of the above designs, respecting of the operational specifications for both normal and emergency conditions, and indicating a 27% reduction in TVS energy consumption, a corresponding CO2 reduction of 58 tons/year/station and a 14% cost reduction in the TVS capital cost.