Escalators and moving walkways are common fixtures in a wide range of buildings including offices, malls, and airports, and they consume large amounts of energy. Technologies are available that can reduce escalator energy use, many of which are prominent in Europe and Asia and have yet to be implemented in the United States. The Airport Cooperative Research Program (ACRP) published a report titled Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies. Though its research is specific to airport applications, the findings are largely applicable to escalators for all building types. The ACRP suggests that the energy-saving potential for escalators and walkways in the US is in the range of 10 to 40 percent per device.
Generally, both escalators and moving walkways consume energy based on how long they run and their passenger load. Because both of these factors are variable, determining energy savings opportunities will be specific to each situation. Although this page focuses primarily on escalators, nearly all of the measures described can also apply to moving walkways.
What are the options?
Key components that affect the energy use of this technology include motors, controls, and lighting. Both escalators and moving walkways are installed as pairs operating in opposite directions. They are usually driven by electric motors connected to the steps or belts and the handrail via a chain mechanism. Motor sizes depend on expected passenger load, but they typically vary between 10 and 20 horsepower (hp). Lighting can be implemented along the handrail as well as at the start and end to make the device more noticeable. There are a wide range of available efficiency technologies (Table 1).
Almost all of the electricity consumed by an escalator is used by its motor. AC induction motors between 7.5 to 15.0 kilowatts—10 to 20 hp—are the most common. Federal standards have been recently updated to mandate NEMA Premium—an efficiency level set by the National Electrical Manufacturers Association—as the baseline when replacing older models. Most escalator motors are oversized because they’re sized for maximum capacity (two people per step), but motors tend to operate inefficiently at the part-load conditions—between 25 and 50 percent of full-load capacity—that are more commonly seen.
Installing a smaller motor to match the load required can also reduce the energy consumed. If it isn’t possible to use a smaller motor, consider installing an adjustable-speed drive to reduce consumption at lower loads. The savings gained from replacing old motors with NEMA Premium models will depend on the number of operating hours, the motor’s horsepower, and the device’s typical load. For small motors with long operating hours, simple payback periods can be as short as 7 months.
Motor efficiency controllers
A motor efficiency controller (MEC) improves efficiency under part-load conditions. MECs optimize the efficiency of three-phase alternating current (AC) inverter-rated motors. Although motors typically operate optimally at 75 percent load, escalator motors often operate in underloaded conditions. Estimated savings from installing a MEC on an underloaded escalator ranges from 10 to 20 percent, with no savings being achieved if the escalator is loaded over 75 percent. MECs can only be used on inverter-rated motors, which are more expensive than general-purpose motors.
MECs’ variable-speed capability allows escalators to save energy during start-up and in slower-run modes. For down escalators, MECs also support regenerative braking operation, in which the motor acts as a generator when passengers are being transported downward, turning brake heat into energy that can be used to power other systems. Keep in mind that if the MEC is programmed for regenerative braking, the electrical distribution system must be protected from short circuits.
Additional energy can be saved if escalators can reduce speed when passengers aren’t present and increase speed to normal levels as they approach; it’s important to ensure that the speed won’t change once passengers are on board. This speed adjustment is accomplished with an intermittent drive that combines a sensor-based monitoring system with an adjustable-speed drive that regulates the frequency delivered to the motor. Three types of sensors are available: motion sensors, light barriers, or contact mats. Intermittent drives are not cost-effective in high-use areas because the volume of traffic allows very little opportunity for the escalator or walkway to slow or stop.
Updated safety standards. Prior to 2010, the American Society for Mechanical Engineers (ASME) maintained a federal policy standard (ASME A17.1) that prohibited the use of intermittent escalator drives. The prohibition was due to concerns that motion changes would cause passengers to lose their balance. The current standard—ASME A17.1-2010/CSA B44-10, allows the escalator speed to be changed as long as there are no passengers using the escalator (Table 2).
Integrating intermittent drives. Coupling energy-efficient technologies can potentially result in larger benefits than if technologies are installed alone.
- Integrating with MECs. The MEC reduces energy use during full speed but low passenger load, and the intermittent drive reduces energy when passengers are not present. Together, these technologies work to increase motor life by reducing temperature and conductive losses.
- Integrating with regenerative drives. Regenerative drives allow for energy recovery from down escalators rather than dissipating waste heat. The recovered energy can be fed back into the building’s systems for use in lighting or other applications. Special care must be taken to ensure that power quality is maintained. According to the escalator manufacturer Schindler in its report on Regenerative Drive Upgrades (PDF), utilizing a regenerative drive can “reduce energy consumption by up to 50 percent when compared to a traditional escalator.”
Upgrading or replacing existing fluorescent lighting on escalator handrails and landing platforms with LEDs can be an opportunity for energy savings. The ACRP estimates that switching escalators to LED lighting from fluorescents will save 30 to 40 percent of lighting energy consumption, and the savings will persist over time because LEDs typically last 60 percent longer than fluorescents.
How to make the best choice
Older escalators tend to be prime targets for efficiency upgrades. To calculate cost-effectiveness, consider the following factors when evaluating potential efficiency upgrades:
- Passenger traffic flow
- Energy-saving technologies currently installed
- Age and operation of equipment
- Space available to install new technologies
- Safety considerations (ASME A17.1)
- Length, width, and height of escalator or moving walkway
The ACRP created a financial calculator (available in the downloadable ISO image on the report order page) that can determine:
- Total energy savings
- Financial payback period
- Return on investment
- Net present value
Note that as of 2014, many states have yet to adopt the federal standards allowing a change in escalator speed as an efficiency improvement. Be sure to check your local and statewide codes.
What’s on the horizon?
Europe and Asia have led the way in escalator energy efficiency. By contrast, the US has not implemented these efficiency measures due to outdated safety restrictions put in place prior to 2010. As states begin to adopt the current ASME standard, however, facilities will be able to capitalize on these potential savings.
Who are the manufacturers?
Most manufacturers provide maintenance and retrofit service packages in addition to entire new systems. Here is a list of prominent manufacturers that serve the US and offer energy-efficient options.
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