Research and practice: Energy-efficient modernisation of lifts
When it comes to the modernisation of lifts, there are three main strategies: the reduction of electrical consumption using energy saving components, minimising heat loss through the lift shaft, and optimising lift operation by means of intelligent traffic management systems. Lifts account for approximately 2-5 % of total energy consumption in residential buildings, and in heavily trafficked office buildings it can increase to 15 % - clearly a very relevant savings potential. rnThe energy demand of a lift installation not only depends on the technology, but also the operating height, the number of floor levels and the intensity of use. A further factor not to be underestimated, is the ever-increasing safety standard which, on the one hand, has made lifts the safest mode of transport in the world, but has also significantly increased their energy consumption when stationary. As an example, modern systems use frequency inverter controls to ensure accurate positioning at each level, thereby reducing one of the main sources of accidents in lifts and improving user comfort, yet frequency inverters (in contrast to ageing two-speed, three-phase AC drives) consume electricity even when stationary. The same goes for supplementary safety related components like light sensors for automatic doors. It is only in the last few years that manufacturers have begun to focus their attention on the reduction of these standby requirements (Fig. 5).
