Empirical data

• Measurements on retrofitted trainsets at NS Reizigers yielded annual energy savings of 7250 kWh per coach.
• Measurements on retrofitted Intercity coaches at SBB yielded energy savings of 14% of total consumption. This impressive figure is not only owed to demand-operated ventilation but rather to a bundle of measures including coach insulation and other.

Estimate of overall potential

No exact data on saving effects as a percentage of total consumption are available. Therefore an estimate of the potential is derived:

According to a rough estimate by DB AG one third of the energy for air-conditioning is needed to climatise fresh air intake. Since demand-operation ideally reduces air intake from the current 100% to actual occupancy ratio, the corresponding energy savings may be up to "100% - occupancy ratio" of this energy, e.g. for a typical occupancy of 40%, the energy saving potential amounts to 60% of the energy needed for fresh air climatisation.

Collecting these figures and taking into account that climatisation is about 20% of total energy consumption of a passenger train, one gets a saving potential of 4 %:

100 % (total consumption) × 0,2 (climatisation energy) × 1/3 (climatisation of fresh air intake)

× 0,6 (saving potential of demand-operated ventilation for typical occupancy) = 4 %

This is a rough estimate of maximum potential and will only be reached (or exceeded) under favourable conditions.

It is obvious that the saving potential is dependent on

• potential for regions with extreme conditions such as cold winters or hot summers)
• average occupancy (high potential for low average occupancies)