Nearly 160, but leaner and meaner than ever
The safety elevator, as we know it today, was introduced nearly 160 years ago, and the first electric elevator 30 years later. The first patents for escalators were filed in the 1890s.
Elevators and escalators account for 2 % to 10 % of the energy used in a commercial building, so cutting their consumption is important.
A number of IEC TCs (Technical Committees) prepare International Standards to ensure systems used in elevators and escalators are energy-efficient and safe to operate.
Traction elevators are the most common type in commercial buildings. They are considered more efficient than hydraulic elevators, which are suitable for low-rise buildings (up to six floors) only.
The basic design of traction elevators, with the machine room housing the motors on top of the lift shaft, dates back to the 1900s. Technological developments in the elevator sector were mainly incremental, rather than revolutionary, until the last decades of the 20th century. Key drivers for more modern elevators then have centred on smaller and more efficient motors, space efficiency and electronic or computerized controls.
In addition to mechanical parts, many electrical elements affect the efficiency of elevators:
- Drive systems (both motor and gearing), and their respective efficiencies, are central to an elevator’s overall energy efficiency.
- Countless control systems that adjust mechanical and electrical functions and have an effect on energy consumption. These systems determine speed, acceleration, door systems (drive, passenger detection etc.), traffic and dispatcher efficiency, and also lighting, ventilation, heating and cooling.
Escalators present different advantages and challenges. They are more convenient to move large flows of people continuously in large stores, railway and underground stations and airport halls. They are not as efficient as elevators to move smaller numbers of people intermittently and, in some countries, cannot be on standby but must operate at all times.
The current generation of elevators is significantly more energy-efficient than the previous ones. Advances concern drives, with more efficient motors and machine room-less systems that see the motor, controller and other components placed on top of the elevator cabin, reducing or eliminating the need for separate cooling. Regenerative braking systems using the energy recovered when braking or slowing down the cabin (like in hybrid vehicles) are also being introduced, reducing power consumption.
Additional energy savings are achieved by using more efficient types of lights with LEDs (light-emitting diodes) replacing incandescent or fluorescent lights and reducing heat and the need for cooling. Sensors that turn off cabin lighting while elevators are in standby mode (up to 50 % of operating time) and turn them on before the doors open, cut electricity use, too.
As for escalators, there are three main options to reduce their energy consumption. All are costly and best considered when installing new systems or refurbishing older ones:
- Turning the escalator off when not in use. This is made possible with the new generation of escalators equipped with sensors that turn them off when no one is using them or approaching. This can cut consumption by 50 %. However, in some countries, in particular some US (United States) states, safety codes require that non-functioning escalators be blocked off, effectively preventing the use of such systems.
- Installing variable-frequency drives and numerous sensors to reduce the speed of the escalators when no one is using them. The drawbacks of this alternative are the high cost of retrofitting existing equipment and, again, that they that they do not meet safety codes in some important markets (for example, the US) and pose potential liability issues for escalator manufacturers and property owners owing to the increased risk of individuals falling and blaming the escalator’s changing speeds.
- Installing an energy-saving soft start system that leaves the speed of the escalator unchanged but reduces the power it consumes when fewer people are on it, reducing energy consumption by up to 33 %.
Installing the latest generation of escalators and elevators can achieve significant savings in the medium- to long-term. However, short-term capital costs rather than long-term operating expenditures often dictate the choice of equipment. The high outlay of replacing older installations and lengthy return on investment periods are the main obstacles to the modernization of equipment, which is best done during major refurbishment phases.
IEC central to efficient and safe operation
Elevators and escalators are complex systems that rely entirely on electrical or electronic parts to function. Many IEC TCs and SCs (Subcommittees) are involved in the preparation of International Standards that ensure these systems work as efficiently and safely as possible. A non-exhaustive list of such TCs and SCs includes
- TC 17: Switchgear and controlgear, which prepares International Standards for these systems as well as for their assemblies, associated control and power equipment
- TC 20: Electric cables, which prepares International Standards for rubber-insulated cables for elevators
- TC 34: Lamps and related equipment
- TC 47: Semiconductor devices, for sensors and other systems
- SC 61D: Appliances for air-conditioning for household and similar purposes
That elevator and escalator producers and suppliers mention the IEC in their trade publicity material — “Motors meet requirements of IEC” (Otis); “Excellent features and simple structure with the relevant requirements of IEC Standards” (Kone); “Global switches meet IEC standards for worldwide acceptance” (Honeywell), or “Designed to comply with the standard IEC/EN 61508 for safety-related systems” (ThyssenKrupp) — attests to their belief that IEC International Standards are essential as well as powerful marketing arguments.