Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies (2014)

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6C H A P T E R 3 This chapter provides a discussion of energy saving technologies for escalators and moving walkways. The discussion is divided into two sections that focus on (1) technologies included in the financial tool and recommended for consideration and (2) technologies not included in the financial tool and not recommended for installation. Various reasons are provided for why the second group of technologies should not be included in the financial tool. Technologies not included in the financial tool may result in low energy savings and, consequently, long payback periods; may no longer be available for instal- lation; or may have limited data available, resulting in difficulty estimating the energy use of the technology. Technologies Included in the Financial Tool All technologies in the following section should be considered and evaluated for installation prior to selecting a technology. A brief description of each technology, along with a summary of benefits and limitations, is provided. This section discusses both stand-alone technologies and technology pairings that are included in the financial tool that accompany this report. The technologies described in the following sec- tion include: • LED lighting, • Capacitors, • High-efficiency motors, • Motor efficiency controllers (MECs), • Intermittent drives, • Intermittent dives paired with motor efficiency controllers, • Intermittent drives utilizing variable voltage–variable frequency drives, and • Intermittent drives paired with regenerative drives. LED Lighting Overview—LED or light emitting diode lighting is a semiconductor light source. It is available for handrail and landing platform lighting for escalators and moving walkways as an upgrade or replacement to the existing fluorescent. They are straightforward replacement/upgrades for existing linear lighting. All manufacturers offer LEDs as an upgrade or with new installations. LEDs have the advantages of lower energy consumption, extended time between failures, and longer life. The largest disadvantage is cost. While LED pricing has been decreasing over Energy Saving Technologies

Energy Saving Technologies 7 the years, LED purchase costs are still several times more than fluorescent lamps. Prices vary so shopping around will assist in price control, and decisions should consider life cycle costs. Benefits—Installing LED lights will result in reduced energy consumption, reduced mainte- nance downtime, and extended time between failures. Limitations—LEDs are sensitive to heat; so, operations in hot areas will reduce time between failures. However, this typically will not be an issue for escalators and moving walkways since the movement of the rotating steps and handrail creates adequate air movement. Capacitors Overview—In an electrical distribution system, a load with a low power factor7 draws more current than an equivalent load with a high power factor, resulting in the same amount of useful power. This need for a higher current increases the energy lost in the distribution system, and requires larger wires and other electrical equipment. Due to the costs of larger equipment and wasted energy, utilities may charge a higher cost to customers for a low power factor. Linear loads with low power factor, such as an unloaded or lightly loaded escalator motor, can achieve greater energy efficiency through the addition of capacitors. Capacitors (see Fig- ure 3-1) used for the correction of a power factor in escalators and moving walkways should be installed as close to the motor as possible to maximize the energy savings. Power factor correction capacitors bring the power factor of an alternating current (AC) circuit closer to 1.0, which is the ideal power factor. It is usually impractical to correct the power factor com- pletely to unity (1.0). There is a diminishing benefit per incremental cost. Adding capacitors will act to cancel the inductive effects of the load, thus reducing the need for reactive current to be generated by the utility and reducing the current flow through the distribution system, and therefore in lower power loss. 7 Power factor (PF) is a measure of the efficiency use of power, or ratio of working power (kW) to apparent/total power (kVA). Figure 3-1. Capacitors.

8 Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies Benefits—Installing capacitors can result in reduced electricity costs if the utility rate structure includes penalties for low power factor. A typical payback period is less than 2 years.8 Capacitors can increase system capacity (e.g., for generators, cables, transformers, etc.), improve voltage regulation, and reduce losses in transformers and cables. Capacitor installation requires minimal capital or labor investment. Typical distribution system losses are in the range of 1 to 4 percent of total kilowatts used. Capacitors can improve distribution losses by 1.5 to 2 percent on average.9 Limitations—Capacitor installations may not result in an acceptable economic payback, even when a facility is being charged kVA billing at a 1.0 power factor target, the most expensive power factor penalty. Capacitors should not be installed on distribution systems with high harmonics since har- monics can cause capacitors to fail. Harmonics are non-linear current or voltage in an electrical distribution system that increase power system heat losses.10 There is the possibility of the distribution system going into a leading power factor situation at light load if passive capacitors are installed. Some utilities charge for a leading power factor. To avoid this, an active switched capacitor bank may be required, which, depending upon com- plexity, can be cost prohibitive. High-Efficiency Motors Overview—The majority, if not all, of the power consumption within an escalator/moving walkway is consumed by its motor. A typical escalator is equipped with a 7.5 to 15 kilowatt (10 to 20 horsepower) inductive AC motor.11 The most common AC motor seen in escalators is the induction asynchronous squirrel-cage motor (see Figure 3-2), composed of an external stator core and rotating rotor.12a The power consumption of a motor is inversely related to the 8 “Power Quality Solutions and Energy Savings—What Is Real?” Eaton Industry Application 1A02704001E, March 2010, Daniel J. Carnovale and Timothy J. Hronek. 9 Ibid. 10 Ibid. 11 “Overview of a Typical Motor,” Power Sines, http://www.powersines.com/SinuMEC_Market_need 12a Christine Toledo, “Improving Motor Efficiency in Constant Speed Applications,” Elevator World, Oct. 2007, http://www. elevator-world.com/files/oct07_copy.pdf Figure 3-2. Asynchronous squirrel-cage AC induction motor. Source: Elevator World

Energy Saving Technologies 9 efficiency of the motor; therefore, the energy consumption of the escalator or walkway can be greatly reduced by installing a high-efficiency motor (see Figure 3-3). There are two basic classes of motors, direct current (DC) and alternating current (AC). AC motors are less expensive, more reliable, and more efficient for applications requiring extended periods of use such as escalators or moving walkways. Within the motor class of AC motors, there are two main types: induction and synchronous. Losses make a motor inefficient. There are five main types of losses in an AC induction motor: stator power losses, rotor power losses, magnetic core losses, friction and windage losses, and stray losses. These losses can be minimized by constructing the motor with superior magnetic materials, larger magnetic circuits with thinner laminations, and larger copper or aluminum cross sections in the stator and rotor windings. High-efficiency motors are usually constructed with these features, and have tighter tolerances, better quality control, and optimized designs. These modifications result in the motors having lower losses, improved efficiency, lower operating tem- peratures, and improved reliability. In addition, most motors within escalators are oversized because they are designed for maxi- mum capacity of two people per step. In a typical AC motor, the efficiency peaks when 90 per- cent loaded, and drops significantly when the load is between 25 percent and 50 percent.12b If a motor is oversized, running with a load less than 50 percent, it will not run efficiently and the energy consumption will increase. If the actual required peak load is known, installing a smaller motor to match the load required can also greatly reduce the energy consumption of an escalator or moving walkway. If a smaller motor cannot be installed, a variable voltage–variable frequency drive (VVVF) can be installed to reduce the energy consumption at lower loads. (See this chap- ter’s section on VVVFs for more information.) A typical standard efficiency induction motor has an efficiency of approximately 84 percent when fully loaded in the size range typically found in escalators and moving walkways. The highest efficiency motors commercially available typically have a nominal efficiency of approxi- mately 90.2 percent in the size range used for escalators and moving walkways.13 The potential savings from installing a high-efficiency motor depends on the number of operating hours, motor horsepower, and typical load. 12b Toledo, Christine. “Improving Motor Efficiency in Constant Speed Applications.” Continuing Education: Motor Efficiency. Elevator World, Oct. 2007. Web. 30 Apr. 2013. http://www.elevator-world.com/files/oct07_copy.pdf 13 “Improving Motor and Drive System Performance,” US Department of Energy, September 2008, https://www1.eere.energy. gov/manufacturing/tech_assistance/pdfs/motor.pdf Figure 3-3. Sample efficiency curve for a standard AC induction motor.

10 Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies Benefits—Installing a high-efficiency motor on an escalator or walkway can greatly reduce operating costs. The operating cost of a motor can represent up to 97 to 98 percent of lifetime costs.14 For small motors that have high operating hours, the payback period for a high-efficiency motor can be as low as 7 months. Typically, as the size of the motor and the operating hours increase, the payback period decreases. In addition, high-efficiency motors are often more reliable, durable, and quieter than standard efficiency motors. Limitations—High efficiency motors cost approximately 15 to 25 percent more than standard motors depending on the size, or $8 to $40 more per horsepower.14 Like all upgrades requiring a component to be replaced, the installation of a high-efficiency motor will require the escalator or walkway to be turned off for a period of time for the installation and will be accompanied by an installation cost, if installed by an outside contractor. Depending on the motor and system, modifications may need to be made to the drive system or motor controls if a high-efficiency motor is installed. If modifications are required, the instal- lation cost will be higher and the payback period will be lengthened. In addition, high-efficiency motors often have less slip, which can result in a slightly higher rotational speed. Slip is the differ- ence between the rotational speed of the stator and rotor. The change in rotational speed should be considered when contemplating installing high-efficiency motors. Motor Efficiency Controller Overview—A motor efficiency controller (MEC) improves the efficiency of a motor dur- ing various loading conditions. MECs are solid-state controllers that dynamically optimize the efficiency of 3-phase AC motors. MECs should only be used on 3-phase motors in escalator and walkway applications. Use of MECs with single-phase motors requires replacement of wiring and produces increased line losses, and therefore is not recommended for single-phase motors. Motors typically operate most efficiently when loaded to 75 percent of their maximum capac- ity. However, escalators and walkways are commonly loaded from 0 percent to 50 percent; as a result, the motors do not run at their most efficient condition. A fully loaded escalator is defined as having two people on each step, a situation that rarely is seen in practice. MECs are designed to address this low loading issue. As stated previously, the six main losses in an AC motor are: friction, windage, stator power, rotor, magnetic core, and stray losses. The magnetic core loss is the energy lost due to eddy currents and hysteresis effects in the magnetic iron cores of the stator and rotor; it is a function of the voltage of the motor terminals. This loss is independent of the load. A motor operates most efficiently when the motor load is above 75 percent of the fully rated load. When the load is very low, the magnetic core loss dominates, representing most of the energy loss. By lower- ing the voltage, the MEC reduces the magnetizing current and thus the magnetic losses. This reduces the total power delivered to the motor; and since the power delivered to the load has not changed, the efficiency is increased. In addition, the MEC reduces the magnetizing current, which is the inductive component of the total power and total current, resulting in an increased power factor. MECs, also known as sinusoidal controllers, modify the shape of the standard AC current wave to reduce voltage and thus improve efficiency and power factor, as shown in Figure 3-4. 14 Lowe, Golini, Gereffi, “U.S. Adoption of High-Efficiency Motors and Drives: Lessons Learned,” Center on Globalization Gover- nance & Competitiveness, February 2010, http://www.cggc.duke.edu/pdfs/CGGC-Motor_and_Drives_Report_Feb_25_2010.pdf

Energy Saving Technologies 11 There are several methods used by MEC manufacturers to accomplish this, but the end result remains the same: reduced voltage to improve efficiency and save energy for motors at low load. The method shown here is the Nola Method designed by the National Aeronautics and Space Administration (NASA). The Nola Method is named after its inventor, Frank Nola, an engineer with NASA’s Marshall Space Flight Center. The energy savings as a result of MEC installation will vary based upon the escalator or mov- ing walkway loading, but it is expected to be approximately 10 to 25 percent for lightly loaded escalators. No savings will be achieved if the load factor is above 75 percent, and minor losses will be incurred to the added energy consumed by the MEC.15 Benefits—MECs bring other benefits in addition to energy savings. MECs are soft start motor controllers, thereby resulting in energy savings during start-up and when the escalator is actively being slowed. MECs have an option to handle regenerative energy on the down escalator without any additional filters or bypasses. When passengers are being transported on a down escalator, a motor acts like a generator (asynchronous motor) and energy is produced. In a traditional escalator with a control system, this energy is converted into heat using dynamic braking resis- tors and dissipated as heat. The MEC controls the escalator load under all conditions and sheds excess energy by converting the energy into electricity and adding it safely back into the supply network for use in building lighting or other applications. However, the accompanying financial tool does not account for regenerative savings. Other potential benefits include reduced operating temperatures of the motor, which in turn reduces maintenance costs and extends motor life (not quantified under this study). In addition, MECs minimize conductive losses in a fashion similar to capacitors. Limitations—In areas where loading is high, above approximately 75 percent of the full load capacity, there would be little savings when using a motor controller. In addition, motor con- trollers can cause significant harmonic distortion, which can increase distribution losses and kilowatt usage, as well as damage equipment and reduce motor life. The motor that the MEC is installed on must be inverter rated. MECs are only compatible with inverter rated motors. If the MEC is programmed to handle regenerative energy, the elec- trical distribution system must be able to handle regenerative energy and fully protected from short circuits and disturbances. 15 “MEC vs. VSD,” Power Efficiency Corporation, May 2012. Figure 3-4. Standard AC motor current.

12 Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies Intermittent Drive Overview of Technology—An escalator equipped with an intermittent drive allows for two- speed operation. With an intermittent drive, the escalator speed can be reduced to a minimally accepted speed or to a complete stop depending on the variance received by local authorities. Escalators using an intermittent drive slow down or stop when the escalator is not in use and speed up to normal operating speeds when a rider appears. Significant energy is saved by slowing down or stopping the electric motor driving the escalator. The traditional AC-motor-driven escalator design assumes the worst-case scenario where the escalator is fully loaded with two riders per step. However, escalators usually operate with much fewer riders than a full load, resulting in a partially loaded escalator. This low load results in resistance losses in the stator and in the rotor, miscellaneous stray losses, and a low power factor, impacting efficiency and electricity costs. An intermittent drive is usually comprised of an inverter and sensor. Typically, a variable fre- quency drive (VFD), which also is known as an adjustable-speed drive (ASD), is used as the inverter. A VFD regulates the frequency delivered to the motor, which directly affects the speed and rotational force of the motor. By installing an entrance monitoring system and VFD, an escalator can be turned on automatically when the passenger activates the sensor or barrier. If the entrance monitoring system is not activated during a pre-defined time, the escalator slows to an allowable speed or stops completely (see Figure 3-5). When activated, the escalator ramps up to a rate of speed based on configurable acceleration curves. Some escalator manufacturers use motion sensors to detect an approaching passenger; others use light barriers or contact mats. It is important that whatever the detection method used, it is reliable to ensure that the escalator will not change speed while there are passengers on board. The most recent American Society of Mechanical Engineers (ASME) Code A17.1: Safety Code for Elevators and Escalators allows the speed of the escalator or moving walkway to change after start-up. The minimum allowable speed is 10 feet per minute and maximum allowable speed is 100 feet per minute; however, variations have been allowed so the escalator may come to a complete stop. Under this provision, escalators and moving walkways must have a means of passenger detection at both landings of the escalator or walkway; additionally, acceleration and deceleration rates cannot exceed 0.3 m/s2. As stated in Chapter 2, in the Applicable Standards section of this report, prior to 2010, the ASME A17.1 code did not allow the use of intermittent drives on escalators or moving walkways. Changes to Sections 6.1.4.1.2 and 6.2.4.1.2 of the code allow for variation of escalator and mov- ing walkway speed after start-up. Not all states have adopted ASME A17.1-2010/CSA B44-10 yet; however, some states that have not yet accepted the code may make exceptions for installation of intermittent drives on a case-by-case basis. Figure 3-5. Typical automatic speed reduction system.

Energy Saving Technologies 13 Benefits—Installing an intermittent drive can result in energy savings of up to 25 percent depending on passenger load.16 The actual savings on a given escalator or moving walkway will depend on how often the unit is idle, but a recent study done by Portugal’s University of Coim- bra estimated that installing intermittent drives on an escalator or moving walkway could reduce total electricity use by about 28 percent. Limitations—The intermittent operation of an escalator has limited applicability. It is not suitable where escalators are in constant use as this leaves little to no intermittent periods to gen- erate reasonable savings. It also is not suitable on systems that do not have inverter-rated motors. Retrofitting an escalator or moving walkway to run intermittently or replacing it with a new intermittent-run escalator is expensive. According to a 2006 GSA and National Institute of Building Sciences’ Intermittent Escalator Study, the design, equipment, and construction may cost $15,000 to $30,000 per escalator.17 The equipment required for intermittent operation includes a sensor for oncoming passen- gers and enough space for a corridor (or a gate/turnstile) to prevent passengers from stepping on the escalator before it is up to full speed. In some situations, there is not enough space for the installation, or architectural changes needed to allow the installation are cost prohibitive. Changing an escalator’s speed may increase potential liabilities for escalator manufacturers and property owners, due to the increased potential for passengers to lose balance and fall during acceleration or deceleration. Intermittent Drive with Motor Efficiency Controller Overview—By pairing an intermittent drive with a motor efficiency controller, the energy consumption of an escalator is not only decreased by reducing the speed when passengers are not present, but also by reducing the energy consumption when the escalator is running at full speed and carrying passengers. As described in the previous section on motor efficiency con- trollers (MECs), the MEC dynamically optimizes the efficiency of a 3-phase alternating current (AC) induction motor. A MEC lowers the voltage delivered to a motor when the load is low (e.g., below 50 percent). This reduces the magnetic losses in the motor, which are the most sig- nificant losses, and increases the motor’s overall efficiency. The intermittent drive technology is a solid-state control that takes input from sensors to deter- mine if someone is on the escalator. The sensors are located at either end of the escalator/walkway and communicate to the two-speed motor to stop or start the unit. Energy savings in the range of 30 percent to 35 percent can be achieved by both slowing the escalator when not in use and by reducing the energy consumption through voltage reduction when passengers are present.15 Benefits—When paired together, an intermittent drive and MEC can result in significantly higher savings. The MEC reduces the energy use during full speed, but low passenger load opera- tion, and the intermittent drive reduces the energy use when passengers are not present. As stated earlier, MECs have an option to handle regenerative energy on the down escalator without any additional filters or bypasses. In addition to energy and cost savings, chances of motor failure are reduced since the motor operating temperature is lowered by the MEC. By lowering the motor operating temperature, the motor life also will be extended and conductive losses in the electrical line will be reduced. 16 ISR—University of Coimbra (Portugal), Energy Efficient Elevators and Escalators. “E4. Intelligent Energy Europe” N.p. Mar. 2010. Web. 30 Apr. 2013. 17 U.S. GSA and National Institute of Building Sciences, Intermittent Escalator Study, 2006, as required by the Energy Policy Act of 2005.

14 Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies Limitations—An intermittent drive paired with a MEC can result in higher savings than either technology would achieve if installed alone. However, the limitations for both technolo- gies still apply, even when paired together. Retrofitting an escalator to run intermittently or replacing it with a new intermittent-run escalator is expensive. The equipment costs for the sensors and a corridor/gate can be significant. In addition, the motor on the system must be inverter-rated in order for an intermittent drive and MEC to be installed. ASME’s recent changes to Code A17.1 allow the speed of the escalator or moving walkway to change after start-up. However, the code has not yet been adopted in all states. If instal- lation is being considered in a state in which the code has not been adopted, the facility owner may apply for a variance to allow the escalator speed to change despite the lack of code adoption. Intermittent Drive Utilizing a Variable Voltage–Variable Frequency Drive Overview—Motor controls such as variable voltage drives, variable frequency drives, and vari- able voltage–variable frequency drives can result in significant energy savings for escalators and walkways. A variable voltage drive (VVD) increases and decreases the voltage delivered to the motor, directly affecting the energy consumption of the motor. Similarly, a variable frequency drive (VFD) changes the frequency delivered, which directly affects the escalator’s speed. Vari- able voltage–variable frequency (VVVF) drives allow for the control of both the voltage and frequency delivered to the motor. Figure 3-6 shows a standard configuration for a VVVF drive. The incoming alternating cur- rent is converted to a direct current before it enters a filter. The exiting current is then converted to the desired frequency and voltage in a DC/AC inverter before passing to the motor. The most common VVVF drive is the pulse width modulation (PWM) voltage source inverter. A PWM divides a sinusoidal output wave into a series of narrow voltage pulses by alternating between a positive voltage, no voltage, and negative voltage. The main benefit of using a PWM is that power loss in the switching devices is very low. In addition, with a PWM the lower voltage harmonics can be greatly reduced, resulting in a smooth rotation in the motor and comfortable rides on escalators and walkways. VVVF drives are often used in conjunction with other technologies to reduce the energy use of an escalator or moving walkway. For example, if paired with a sensor, a VVVF can be used for an intermittent drive system. The sensor will note when the escalator is not in use and drop the voltage and frequency delivered. This, in turn, reduces the speed and energy drawn by the motor. The highest potential savings for a VVVF is seen when it is paired with a sensor to form an intermittent drive. Alone, a VVVF cannot detect a lack of passengers to adjust the speed of the escalator accordingly. When paired with a sensor, a VVVF reduces the energy consumption during start-up and at low speed when passengers are not present. However, no additional sav- ings occur during start–stop operation. Figure 3-6. General configuration of a VVVF drive.

Energy Saving Technologies 15 Benefits—A VVVF can reduce energy consumption of an escalator by up to 30 percent.18 In addition, VVVFs can increase the useful life of a motor. According to the Intermittent Escalator Study, controlling the speed of a motor can reduce maintenance costs by up to 2 percent per year.19 In addition to energy and cost savings, VVVFs allow for the most precise control of escalator speed when compared to other means of control. In the past, it was difficult to precisely control the acceleration and deceleration rates of escalators and moving walkways. However, technol- ogy advances over the past 15 years have resulted in the ability to precisely control the speed of AC motors used for escalators and moving walkways. VVVF motor controllers available today provide that control for escalators and moving walkways so that the desired rate of speed change is never exceeded, not even for a fraction of a second. The VVVF also allows for low starting currents when compared to a two-speed AC motor or an AC motor with a variable voltage controller. Figure 3-7 shows a comparison of the current 18 “KONE Solutions & BREEAM.” KONE: Dedicated to People Flow. KONE Great Brittain, n.d. Web. 30 Apr. 2013. http:// www.kone.com/countries/en_GB/environment/BREEAM/Pages/default.aspx 19 U.S. GSA and National Institute of Building Sciences, Intermittent Escalator Study: As Required by the Energy Policy Act of 2005, https://fortress.wa.gov/ga/apps/sbcc/File.ashx?cid=719 Figure 3-7. Comparison of AC motor, AC motor with VV, and AC motor with VVVF.

16 Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies over time for a two-speed AC motor, an AC motor with a variable voltage controller, and an AC motor with a VVVF. The increase in current for the motor with a VVVF drive is more gradual than the increase for a two-speed motor or a motor with a basic variable voltage controller. This provides a smooth ride for the passengers and a higher power factor. Additionally, the low starting currents help to increase the useful life of the motor serving the escalator or walkway. Limitations—Variable voltage–variable frequency drives do not work for all applications. As with any escalator technology that automatically changes the speed of an escalator or walk- way, the chance of an accident or injury occurring increases. However, advances in technology over the past 15 years have greatly reduced the likelihood of accidents caused by equipment malfunctions. Studies done by Power Efficiency Corporation have shown the energy consumption of the escalator can increase by as much as 15 percent when a VVVF is installed, and the escalator is running constantly at full speed. Therefore, a VVVF may not be appropriate for all situations, such as in locations where the passenger flow is relatively constant. Intermittent Drive with Regenerative Drive Overview—Escalators equipped with intermittent drives can be used in conjunction with regenerative drives to produce significant energy savings. An intermittently run escalator stops or slows the escalator when passengers are not present and increases the speed of the unit to normal operating speeds when passengers approach the entrance. When paired with a regen- erative drive, energy is recovered when the escalator is moving in a downward direction with passengers present. Regenerative drives are one of the latest developments in escalator technology that focuses on recovering escalator energy and converting this energy to electricity. When passengers are being transported on a moving escalator, the drive motor acts like a generator (asynchronous motor) and energy is produced. In a traditional escalator, this energy is converted into heat using dynamic braking resistors. The regenerative drive controls the escalator load under all conditions and sheds excess energy by converting the energy into electricity and feeding it safely back into the supply network for use in building lighting or other applications. This technology can be used in conjunction with soft start-up or intermittent start–stop drives. A soft starter is a device that temporarily reduces the torque and current surge of the motor during startup. This reduces the mechanical and electrical stress on the motor, thus extending the lifespan of the system. The basic requirements of soft start-up and intermittent start–stop can be programmed into a regenerative drive. When using a regenerative system, special care has to be taken to ensure that the regenerated power is of sufficient quality to be accepted into the grid and that the grid is fully protected from short circuits and disturbances. Standard inverter drives have an input section, a power reservoir, and an output section. In general, they operate with energy freely flowing in both directions through the output (inverter) sections, but the input section is a diode bridge that only permits energy to flow in one direction. Regenerative drives maintain these three sections, allowing power to flow in both directions across the input, as well as the output, section. This is achieved by merging two inverters back to back. The additional input inverter allows power to flow from the power distribution system to the power reservoir when needed, and allows unimpeded reverse flow into the power distribu- tion system when the reservoir is above normal operating levels. When the escalator motor is under load, the input inverter circuitry is automatically operated to allow the power supply to pass through and maintain the power reservoir at the optimum

Energy Saving Technologies 17 condition. When the passenger load reaches enough mass to drive the escalator down with- out the assistance of the motor, the electric motor acts as a generator and energy is passed back through the output inverter section and feeds into the power reservoir. Under these conditions, the regenerative drive switches the excess power using the input inverter action to return the excess energy to the power distribution system. An important function of the input inverter is to synchronize the regenerated power with the phase rotation of the incoming power distribution system. See Figure 3-8 for a typical regenerative drive configuration on an escalator. Benefits—According to one escalator manufacturer, an escalator equipped with a regenerative drive that captures energy generated by the escalator and delivers this energy back to the building for use by other systems can reduce energy consumption by up to 50 percent when compared to a traditional escalator.20 Combining the intermittent drive with regenerative technologies results in greater savings than when using each technology alone. In addition, the regenerative drive produces clean, safe energy that has added environmental and carbon footprint benefits. Limitations—The energy savings as a result of regenerative drive will not be achieved on a moving walkway. In addition, as stated earlier, the intermittent operation of an escalator has limited applicability. It is not suitable where escalators are in constant use as this leaves little to no opportunity for reasonable savings. Also, the electrical distribution within the building may not always be able to accept the regen- erated electrical energy. If there is no constant need for the regenerated energy, the payback of installing a regenerative drive may be excessive. In addition, braking resistors will still be required to dissipate the heat from the energy that cannot be repurposed. Due to significant added installation cost, regenerative drives are not always cost effective, especially in areas with reduced traffic. Also, retrofitting an escalator to run intermittently or replacing it with a new intermittent-run escalator is expensive. As stated earlier, in some situa- tions, there may not be enough space for the installation or architectural changes necessary to provide the needed space may be cost prohibitive. Figure 3-8. General configuration of a regenerative drive on an escalator. 20 “Sustainable Products: Drive Systems,” ThyssenKrupp Elevators, http://sustainability.thyssenkrupp-elevator.com/en/products/ drive-systems/

18 Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies Technologies Not Included in the Financial Tool Although the following technologies are often recommended as energy saving options for escalators and moving walkways, the report authors chose to exclude these technologies from the financial tool for one of the following reasons: • The technology may result in low energy savings and, consequently, long payback periods; • It may no longer be available for installation; or • Limited data may be available, that does not allow for analysis to determine the costs and benefits of the technology. Technologies excluded from the financial tool and discussed in the following section include: • Regenerative drives, • Wye-delta configured motors, • Direct drives, and • Intermittent drives with motor efficiency controller and variable voltage–variable frequency drive. Regenerative Drives Overview—Regenerative drives, as previously discussed, recover escalator energy and convert the energy to electricity. When an escalator is loaded, the drive motor acts like a generator and energy is added back to the grid. In a traditional escalator, this energy is converted into heat using dynamic braking resistors. The regenerative drive converts the excess energy into electric- ity and feeds it safely back into the supply network for use in the facility. Regenerative drives as a single technology are not included in the accompanying financial tool since energy data for validation of the savings was not available. However, regenerative drives are offered by many escalator manufacturers and are a recommended technology for consideration on down escalators and, in some cases, for up escalators, depending on the average loading for the escalator. Benefits—As stated earlier, regenerative drives can reduce an escalator’s energy consumption by up to 50 percent compared to a traditional escalator.21 Regenerative drives also reduce the heat generation from an escalator, which in turn, means a reduction in the cooling requirements around the unit. Limitations—Regenerative drives only result in energy savings on escalators and are not rec- ommended for moving walkways. In addition, the electrical building electrical distribution may not always be able to accept the regenerated electrical energy. Regenerative drives can be expensive to install, and therefore have very long payback periods in applications without a constant need for the regenerated energy. In addition, braking resistors will still be required to dissipate the heat from the energy that cannot be repurposed. Wye-Delta Configured Motors Overview—Wye-delta motors can operate in the star configuration when there is low escala- tor traffic. When the motor is switched to star operation, it is supplied with lower voltage, result- ing in lower torque. When several passengers enter the escalator (usually 5 passengers) the motor is switched to delta operation, and the motor voltage is returned to normal. 21 “Sustainable Products: Drive Systems,” ThyssenKrupp Elevators, http://sustainability.thyssenkrupp-elevator.com/en/products/ drive-systems/

Energy Saving Technologies 19 Three-phase motors have three windings. On some motors, all six ends are utilized (two ends per winding). On those motors, it is possible to connect the three windings such that they form a triangle shape (delta configuration), or a radial shape resembling the letter Y (wye or star con- figuration). One then connects the three power leads from the 3-phase source to three points in those configurations. See Figure 3-9. Significant energy savings (up to 25 percent depending on passenger load) can be obtained in low passenger load situations when the motor is in the star configuration. A sensor will detect when a loading of approximately five or more people are present on the escalator. At this point, the unit switches to the delta contactor to allow for the added load. External electromagnetic contactors are used to change the motor windings between the two configurations. When the windings of a three-phase motor are connected in star configuration, the voltage and current applied to each winding are reduced by approximately 57 percent (1/3) of the voltage applied to the winding when it is connected in a delta. However, as a result, the total output torque when in a star configuration is only a third of the total torque it can produce when running in a delta. Benefits—Installing a wye-delta configured motor can result in energy savings up to 25 per- cent depending on passenger load. The actual savings on a given escalator will depend on how often the unit is run in the star configuration. Limitations—The wye-delta operation of an escalator has limited applicability. It is not suit- able where escalators are constantly heavily loaded (5 or more passengers) as this leaves little to no opportunity for long enough intermittent periods to generate reasonable savings. This technology was not included in the financial tool due to limited examples and available data for wye-delta motors being installed on escalators or moving walkways. Direct Drives Overview—A direct drive is a beltless and chainless drive connected directly to the main shaft of a motor. The direct drive takes the power coming from a motor without any reductions, such as a gearbox, thus maintaining motor efficiency. Being beltless and chainless eliminates the risk of slippage, belt or chain failure, and the need for oil. A direct drive consumes less electricity relative to other standard drives on the market. A direct drive has increased efficiency because power is not wasted in friction from belts, chains, and gearboxes. Direct drives operate at reduced noise levels since there are fewer parts that are prone to vibration. Having fewer parts results in improved reliability, thus less potential for escalator downtime. Benefits—The chainless drive eliminates the risk of chain failure and the need for oil. Fewer spare parts are needed due to the simple configuration and chainless design. Because the motor is directly coupled to the main shaft, efficiency increases and the power required to run the escalator is reduced. Figure 3-9. Wye (star) motor configuration versus delta motor configuration.

20 Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies Limitations—This technology was not included in the financial tool since it is no longer provided by escalator or moving walkway manufacturers. Retrofits may not be possible without significant space changes, thereby making this a cost-prohibitive technology. Intermittent Drive with Motor Efficiency Controller and Variable Voltage—Variable Frequency Drive Overview—An intermittently run escalator or moving walkway slows down or stops when passengers are not present and speeds up to normal operating speeds when a rider appears. By slowing down or stopping the electric motor driving the escalator, significant energy is saved. When paired with a MEC and VVVF, additional energy savings can be realized. When connected to a down escalator, a MEC reduces voltage and current as each passenger boards. The motor will naturally draw less current but the MEC will reduce that current even more. This process continues until the motor current monitored by the MEC reaches a value just above zero. At this point, the MEC will transition to energy saving mode and turn on the silicon- controlled rectifiers (SCRs), allowing full voltage and current conduction back to the building’s electrical distribution system. As the load increases, the motor starts running at the contact fre- quency. At this point, the motor actually stops using energy and starts producing energy, similar to a regenerative drive. The voltage and current have the same characteristics as the building dis- tribution system, therefore no harmonic disturbance is created in the building distribution system. The intermittent drive operating in the same load condition on a downward escalator will not reduce the current to the motor. The motor under the load on the escalator will naturally draw less current, although the motor voltage will stay the same. This will result in a higher energy usage compared to the MEC when the escalator is loaded. When the load reaches below zero current and the motor starts to produce energy, this power is sent back to the inverter. To control the rated speed of the down escalator, the inverter takes this excess power and diverts it to dynamic braking resistors. This excess power from the motor is turned into heat in these resistors and never goes back to the building distribution system. Therefore, this excess power is not available for use somewhere else in the building. This technology will require motion sensors to detect an approaching passenger. Some esca- lator manufacturers use light barriers or contact mats to detect passengers. It is important that whatever the detection method used, it is reliable to ensure that the escalator will not change speed while there are passengers on the moving steps. Benefits—The motor efficiency controller can save an average of 20 percent on escalators when the escalator is running at high speed. The intermittent drive saves additional energy depending upon the amount of time the escalator spends running in slow mode. When monitoring both an upward and a downward escalator, it is common to see the savings on the downward escalator to be higher than on the up escalator. This is due to the regenerative nature of the downward escalator. Theoretically, if both are installed on an escalator, the MEC will prevent the energy consumption of an escalator or moving walkway from increasing when at full speed due to the installation of the VVVF. With both technologies installed on an escalator or moving walkway, the benefits from each technology will be distinctly apparent; however, the limitations for each technology will still apply. Limitations—Of the manufacturers contacted for this project, none currently offer this grouping. In addition, limited examples of the technology configuration were available at the time of the study. Since limited data was available for this technology configuration, methodolo- gies for calculating the potential savings could not be developed or validated, and the configura- tion could not be included in the accompanying financial tool. Most of the limitations that apply to the intermittent drive, MEC, and VVVF still apply when the technologies are used together. The intermittent operation of an escalator is not suitable

Energy Saving Technologies 21 where escalators are in constant use as this leaves little to no opportunity for long enough inter- mittent periods to generate reasonable savings. Retrofitting an escalator to run intermittently or replacing it with a new intermittent-run escalator also can be expensive. Summary of Technologies Table 3-1 provides a summary of the technologies, including their benefits and limitations. Technologies Overview Benefits Limitations LED Lighting An LED, or light-emitting diode, is a semiconductor light source that consumes significantly less energy than typically used light sources such as incandescent lights. LED lighting can reduce lighting consumption by up to 38 percent and last much longer than other types of lighting. LED lighting may appear slightly dimmer compared to T8 and T12 lighting. Capacitors A capacitor is a passive two- terminal electrical component used to store energy and improve the power factor of an electrical line. Capacitors help avoid losses due to low power factor and penalty fees charged by utilities due to poor power factor. If the power factor on an escalator/moving walkway unit is fair to start with, the payback period for capacitors can be high. Capacitors also should not be installed on distribution systems with high harmonics since harmonics can cause capacitors to fail. High-Efficiency Motors High-efficiency motors are motors with 1 percent to 10 percent higher efficiency than standard motors because of less internal loss in the motor due to power losses and magnetic core losses. Fully loaded efficiency of a typical high-efficiency motor is 90.2 percent. Significant energy savings can be achieved and the useful life of the motor can be lengthened. High-efficiency motors are not compatible with all applications. Modifications may need to be made to the drive system or motor controls if a high-efficiency motor is installed. In addition, high- efficiency motors often cost 15 to 25 percent more than standard motors. Motor Efficiency Controllers (MECs) A motor efficiency controller (MEC), also known as a sinusoidal drive, is a solid- state controller that dynamically optimizes the efficiency of a 3-phase alternating current (AC) induction motor. A savings of 10 to 25 percent can be achieved depending on the load factor and escalator direction. MECs also reduce the operating temperature of the motor, thereby reducing maintenance costs and prolonging its useful life. Little savings are seen on systems that are over 75 percent loaded. Intermittent Drives Intermittent drives reduce the speed of an escalator when no passengers are present. A sensor is placed at the entrance and the exit of a moving walkway or escalator. When the sensor detects that no passengers are present, the motor controller reduces the speed of an escalator or moving walkway to a minimally accepted speed. Intermittent drives can result in significant savings. Since intermittent drives reduce the speed of an escalator/moving walkway when passengers are not present, they also increase the useful life of the motor and reduce maintenance costs. Little savings can be achieved on escalators/moving walkways on which passengers are always present. Installing an intermittent drive can be costly and may require modifications to the surrounding area to allow enough space for the sensors. In addition, not all states have adopted the ASME 17.1 2010 code that allows escalator/moving walkway speeds to be variable. Intermittent Drives (Start– Stop) with MECs Intermittent drives can be paired with a MEC. If paired together, to maximize savings potential, it is recommended that the escalator be brought to a complete stop when no passengers are present. When paired together, the savings achieved for an escalator/moving walkway is higher than when only one technology is installed. The limitations that apply to the intermittent drive and MEC still apply when the technologies are paired together. Table 3-1. Summary of technologies included in the financial tool. (continued on next page)

22 Airport Escalators and Moving Walkways—Cost-Savings and Energy Reduction Technologies Technologies Overview Benefits Limitations Intermittent Drives with Variable Voltage– Variable Frequency Drives (VVVF) A VVVF is a motor controller that regulates the voltage and frequency delivered to a motor depending on the loading. When paired with a sensor, the VVVF can act as an intermittent drive. When passengers are not detected by the sensor, the escalator/moving walkway can either be slowed to a minimum allowable speed or brought to a complete stop when no passengers are present. If an escalator is frequently found running when passengers are not present, significant savings can be achieved with a VVVF, and the useful life of the motor can be lengthened. The limitations that apply to the intermittent drive still apply when the technology is paired with a VVVF. Due to the installation of the VVVF, the energy consumption of the escalator/moving walkway may be increased when the unit is fully loaded. Intermittent Drives (Start– Stop) with Regenerative Drives Intermittent drives can be paired with a regenerative drive. When paired with a regenerative drive, the motor acts like a generator (asynchronous motor) and energy is produced when the escalator is moving downward and, in some cases, in the up direction. This technology pairing not only reduces the energy consumption of the unit, but can supply energy to the electrical grid. The installation cost for this pairing is the highest of all the technology pairings discussed in this report. The limitations that apply to the intermittent drive still apply when the technology is paired with a regenerative drive. In addition, the electrical supply grid may not always be able to accept the escalator- regenerated electrical energy. Table 3-1. (Continued). Technologies vs. Potential Savings Potential savings of various technologies are provided in Table 3-2. Technology(ies) Average Potential Savings LED Lighting 30 to 40 percent* Capacitors 0.5 to 2 percent High-Efficiency Motors 2 to 18 percent** Motor Efficiency Controllers (MEC) 10 to 25 percent Intermittent Drives 15 to 25 percent Intermittent Drives (Start–Stop) with MECs 30 to 35 percent Intermittent Drives (Slow down) with Variable Voltage–Variable Frequency Drives (VVVF) -15 to 57 percent Intermittent Drives (Start–Stop) with Regenerative Drives 30 to 50 percent (excludes moving walkways) * On lighting energy consumption only. ** Depends on loading and motor horsepower. Table 3-2. Potential energy savings.