024 -- Role of Variable Speed Drives in Safe, Reliable and Energy Efficient Tunnel Ventilation

With the urbanization growth, infrastructures develop rapidly, including tunnels and subways construction. In such projects, special attention is paid to ventilation since it provides comfort for tunnel users as well as safety in emergency situations. Active ventilation implies air movement via a fan wheel driven by a motor. To control the air flow rate, direction and pressure, variable speed drives (VSDs) are used. Nowadays, drives are an integral part of the tunnel ventilation – they help secure process efficiency and reliability, as well as the tunnel safety. As ventilation accounts for a big portion of the energy consumed by a tunnel, drives have been proposed to provide improvements to the tunnel energy efficiency and decrease operating expenses. Drives adjust the fan motor speed to a specific need depending on the vehicle exhaust concentration. Active front end drives go beyond fan speed control for efficient energy use. They focus on power quality eliminating disturbances in the network to ensure continuous and reliable ventilation – extremely relevant for remotely located tunnels with a weak power supply. In a fire case, VSDs add flexibility to a smoke suppression strategy. They can adjust fan speed and direction to maintain smoke stratification and prevent backlayering for safe tunnel users' evacuation, as well as provide access to the fire location for emergency services. Fire in a tunnel requires immediate reaction from the ventilation or smoke extract system, and drives can ensure a prompt fan start, stop or direction change addressing stringent requirements of the industry.