SUSTAINABLE TUNNEL OPERATION - ELECTRICITY GENERATION BY THERMAL- AND PRESSURE DRIVEN AIR FLOWS.

The energy demand for the operation of a road tunnel is considerable. This results on one hand in high operation costs and – as the production of electricity is not free of fossil fuels – in a remarkable CO2 footprint. The need of reducing the energy costs as well as for improving the CO2 footprint is obvious. Due to the high energy costs, alternative options for generating electricity are coming into focus. The question arises as to whether mechanical ventilation systems can be used in reverse operation to generate electricity in road tunnels when pressure-driven air flows are present.
The present paper deals with aspects on pressure-driven air flows in general and their use to generate electricity in electrical machines. In the first step, a potential analysis was carried out for standard 2-lane tunnels with different lengths and meteorological pressure differences. In a second step, recorded pressure differences between portals or shafts were evaluated for selected Austrian roads tunnels.
The calculation of the annual energy quantities for possible electricity generation was based on the actual pressure differences in tunnel systems in the Austrian motorway and expressway network. Based on the available measurement data, those tunnel systems that have a high meteorologically-related pressure difference were selected for further consideration. Taking into account the aerodynamic conditions and the expected efficiencies of electricity generation, an expected annual amount of energy can be estimated.