Elevators are typical potential energy loads. Under specific operating conditions, the traction machine motor switches from power consumption to power generation, continuously producing regenerative electrical energy. This primarily occurs in three scenarios: first, heavy-load downward travel, where the car's load exceeds the counterweight's mass, and gravitational potential energy drives the car downward, reversely rotating the motor to generate electricity; second, light-load or no-load upward travel, where the counterweight is heavier than the car, causing it to descend and pull the car upward, again reversely driving the motor to produce electricity; third, deceleration and braking, where the elevator decelerates before reaching the target floor, rapidly releasing its mechanical kinetic energy and converting it into electrical energy.
Practical project verification has shown that after installing energy feedback devices on building elevators, the average energy saving rate for a single elevator can reach 30%, and can exceed 40% under optimal conditions. For commercial buildings or residential complexes equipped with multiple elevators, the economic and social benefits of energy conservation are significant, offering high promotional and application value.
Figure 1: Elevator Power Generation Scenarios: Heavy-load Downward and Light-load Upward (Schematic Diagram)
I. Principle of Energy Recovery
Conventional unmodified elevators lack an energy recovery function. The regenerative electrical energy generated during elevator operation continuously raises the DC bus voltage of the variable frequency drive (VFD). To ensure safe equipment operation, the system dissipates this excess energy as heat through braking resistors. This not only wastes a large amount of electrical energy but also continuously increases the ambient temperature in the elevator machine room, accelerating equipment aging and compromising the overall operational stability of the elevator.
After installing a dedicated elevator energy feedback device, the regenerative electrical energy can be recovered, purified, and fed back into the grid for reuse. The complete energy recovery process consists of three main steps:
1. Energy Capture: The AC power generated by the elevator during operation is converted to DC power by the VFD's rectifier and temporarily stored in the DC link capacitors of the VFD, achieving the initial collection of regenerative energy.
2. Intelligent Inversion: When the VFD's DC bus voltage reaches a system-set threshold, the energy feedback device activates preferentially (with priority over the braking resistor). Utilizing core components like an IGBT full-bridge inverter and a DSP microprocessor, the device inverts the DC bus voltage into three-phase AC power that matches the building's low-voltage grid in frequency, phase, and voltage.
3. Purification and Feedback: The inverted AC power is filtered and purified through components like filter reactors to effectively eliminate harmonic pollution. After ensuring the power quality meets standards, the power is safely fed back into the building's public AC grid, achieving waste-to-energy reuse.
Figure 2: Schematic Diagram of Elevator Energy Recovery
II. Relevant Standards Requirements
The national standard GB/T 32271-2015, "Elevator energy feedback device," specifically governs the technical parameters, test methods, and safety performance of elevator energy-saving feedback equipment. It is applicable to uncontrolled rectifier variable voltage and variable frequency (VVVF) elevators with rated voltages up to 400V in TN-S power supply systems. The standard imposes mandatory constraints on core indicators such as device energy efficiency, power quality, and operational safety. Specific requirements are as follows:
Efficiency Classification Requirements: Three levels of efficiency standards are defined based on load conditions: conversion efficiency ≥85% at 25% load, ≥90% at 50% load, and ≥95% at 100% rated load.
Power Quality Requirements: The Total Harmonic Distortion of current (THDi) fed back to the grid must be ≤5%. Additionally, specific limits are set for the content of odd and even harmonics to prevent pollution of the public grid.
Power Factor Requirements: When the device's output power reaches 50% of its rated power, the operating power factor must be ≥0.90 to ensure grid operational efficiency.
Safety Protection Functions: The equipment must be equipped with comprehensive protection mechanisms, including anti-islanding, overvoltage, undervoltage, short-circuit, and open-circuit protection. It should also be capable of handling fault scenarios like abnormal grid frequency, ensuring the safe and stable operation of both the device and the grid.
This standard also specifies the test platform, conditions, and measurement methods for verifying these indicators. It requires the use of high-precision bidirectional energy meters for simultaneous metering at the DC input and AC output terminals of the device. By comparing the DC input active energy with the AC output active energy, the actual conversion efficiency of the energy feedback device is calculated to ensure the equipment meets performance standards.
III. Selection Scheme for Elevator Energy Feedback Energy Metering
According to the national standard's technical requirements and considering the operational characteristics of elevator energy feedback systems, retrofit projects require the deployment of metering devices on both the DC side (device input) and the AC side (device grid-connection output). This setup covers data monitoring needs for power generation, feedback quantity, power quality, and conversion efficiency. Specifically, the DC side monitors DC voltage, DC current, and bidirectional DC regenerative energy. The AC side monitors three-phase voltage, three-phase current, bidirectional active energy, reactive power, and apparent power. Simultaneously, power quality parameters such as current harmonic distortion, individual harmonic content, power factor, and DC component are monitored across the entire system.
(1) AC Grid-Connection Side Metering Scheme (for Overall Elevator Energy Consumption and Feedback Energy Statistics)
Installation Location: At the 380V three-phase incoming line of the elevator distribution panel and the grid-connection terminal of the energy feedback device.
Core Purpose: To meter the electrical energy drawn from the grid and the regenerative energy fed back to the grid by the elevator. This allows for calculating the overall elevator energy consumption and energy-saving benefits, providing data support for energy efficiency assessments.
1. Wired Networking Scheme (Standard for New Projects):
Selected Device: DTSD1352 Three-Phase Rail-Mounted Energy Meter.
Device Advantages: Supports three-phase four-wire metering, offers 0.5S class high-precision four-quadrant bidirectional metering. Can be used with external split-core current transformers. Suitable for batch retrofit projects for elevators in new residential complexes and commercial buildings. Wired networking is stable and reliable, suitable for standardized engineering construction
Figure 3: New Photovoltaic Primary Diagram
3.2 Relay Protection and Safety Automatic Devices
Microcomputer-based protection is adopted for all major electrical equipment in the PV station to support data upload. Component protection is configured in accordance with Technical Specifications for Relay Protection and Safety Automatic Devices (GB 14285-2006).
1) Anti-islanding Detection
The AM5SE-IS anti-islanding device deployed in this Project applies to grid-connected new energy power generation systems including 35kV, 10kV and low-voltage 380V PV and gas power stations. It features three-stage overcurrent protection, inverse time protection, two-stage zero-sequence overcurrent and zero-sequence inverse time overcurrent protection, with the following core functions: ① Personnel Safety Protection: Upon grid or PV-side power loss, the anti-islanding device acts rapidly to disconnect the grid connection point, preventing maintenance staff from contacting live equipment unknowingly and safeguarding personal safety. ② Prevention of Grid Surge and Equipment Damage: Quick disconnection eliminates abnormal voltage and frequency fluctuations caused by islanding, avoiding impact and damage to both the power grid and PV equipment. ③ Improved System Reliability: Real-time monitoring and rapid response stabilize grid-connected PV systems, balance power exchange with the main grid, and enhance overall system reliability.
Inverters for distributed PV projects must feature rapid islanding detection and instant disconnection from the grid upon islanding identification. Anti-islanding schemes shall coordinate with relay protection, safety automatic devices and low-voltage detection equipment with matched action timing, complying with State Grid specifications.
2) Grid-connected Line Relay Protection and Safety Automatic Equipment
When short-circuit faults occur on distributed PV grid-connected lines, line protection shall act instantly to trip the corresponding grid-connected circuit breaker, enabling fast and reliable fault clearance across the full line. A fault splitting device shall be installed on the 10kV busbar of user substations hosting PV facilities to implement emergency control over abnormal frequency and voltage, tripping dedicated circuit breakers as required.
3) Power Quality Monitoring Devices
Distributed PV projects must meet national grid power quality requirements. Per national standards such as Technical Rules for PV Power Systems Connected to the Grid (GB/T 15543-2008), power quality parameters including voltage, current, frequency and harmonic distortion shall be controlled to ensure stable operation of PV systems and reliable grid power quality.
4) AGC/AVC Devices
For integration into China Southern Power Grid, distributed PV projects must comply with Technical Specifications for Distributed PV Generation Connected to Distribution Networks (GB/T 29319-2024) as required by CSG dispatching departments. Equipping AGC/AVC devices enables regulation of active and reactive power of inverters, fulfilling the "Four Visible & Controllable" requirements: observable, measurable, controllable and adjustable.
Figure 3: DTSD1352 Three-Phase AC Rail-Mounted Energy Meter
2. Wireless IoT Scheme (for Retrofit Projects with Difficult Wiring):
Selected Device: ADW300 Series Wireless IoT Power Meter.
Device Advantages: Optional 4G, Wi-Fi communication modules support TCP bidirectional transparent transmission, allowing data to be directly uploaded to the cloud platform. Requires no complex wiring and supports installation without power outage, suitable for energy-saving retrofits of elevators in older residential areas or standalone buildings.
Figure 4: ADW300 Three-Phase AC IoT Energy Meter
(2) DC Feedback Bus Side Metering Scheme (for Regenerative DC Energy Statistics)
Installation Location: On the DC540V/750V bus side inside the energy feedback device.
Core Purpose: To independently meter the elevator's DC regenerative generation and calculate the conversion efficiency of the energy feedback device. Also suitable for scenarios integrating elevator energy storage systems (capacitor/lithium battery), for real-time monitoring of DC energy data during storage device charging/discharging.
Selected Device: DJSF1352-RN Bidirectional DC Rail-Mounted Energy Meter.
Device Advantages: Voltage measurement range covers DC 0~1000V, supports connection to 75mV shunts and 0~20mA/0~10V Hall sensors. Optional dual-channel DC input can simultaneously monitor regenerative generation and energy storage charging/discharging. Available in accuracy classes 0.5 and 1.0 to meet high-precision testing requirements.
Figure 5: DJSF1352-RN DC Energy Meter and Matching Hall Sensor
(3) Data Acquisition and Transmission Scheme
Wired metering devices require dedicated data acquisition equipment to centrally collect, parse, and upload field instrument data to the cloud, ensuring stable data transmission.
Selected Devices: ANet-1E2SM-4G, AWT100-4G Data Concentrators.
Device Advantages: The downstream side is compatible with the RS485 interface and the Modbus-RTU standard protocol, adaptable to all on-site smart instruments. The upstream side supports both 4G wireless and Ethernet transmission methods. Features a rail-mounting design suitable for various equipment room scenarios, with flexible device model selection based on the requirements of the superior platform.
Figure 6: ANet-1E2SM-4G and AWT100-4G Data Acquisition Scheme
IV. Elevator Energy Feedback Management System Solution
The solution is complemented by the Acrel-EIoT Energy IoT SaaS Cloud Platform, a self-developed, lightweight intelligent management platform. It supports multi-protocol device access and multi-terminal synchronous access. It integrates comprehensive functions such as real-time energy monitoring, equipment efficiency analysis, power quality diagnosis, fault alarm push notifications, and automatic generation of data reports, enabling remote visualization, digitalization, and intelligent management of the elevator energy feedback system. Users can quickly complete device commissioning via a mobile app QR code scan. Energy consumption data, operational parameters, and energy-saving statistical results can be accessed anytime via the computer WEB interface or mobile devices.
Figure 7: Acrel-EIoT Energy IoT Cloud Platform
System Hardware and Software Device Selection Summary Table:
Name
Picture
Model
Function
Application
DTSD1352
·Three-phase current and voltage measurement
·Time-of-use (TOU) energy metering
·Bi-directional (import/export) energy statistics
·Multi-tariff (TOU) rate configuration, compatible with multiple time-of-use rate schedules
·Accuracy Class 0.5S
·RS485 communication interface
Elevator power distribution incoming line or energy feedback grid-connection point
ADW300
·Three-phase electrical parameter measurement
·Time-of-use (TOU) energy metering
·Bi-directional (import/export) energy statistics
·Built-in split-core current transformers
·Supports installation without power outage (live installation capable)
·RS485 communication interface
·4G wireless communication capability
·Accuracy Class 0.5S (when using external/standard CT connection)
·Accuracy Class 1.0 (when using the built-in split-core current transformer solution)
Elevator power distribution incoming line or energy feedback grid-connection point
DJSF1352
·Measures voltage, current, power, and bi-directional (import/export) energy in DC power systems
·Compatible with Hall sensors (optional)
Elevator variable frequency drive (VFD) DC output terminal
AHKC-EKA
·Measuring range: DC 0 to (5~500) A current
·Output: DC 4~20 mA
·Operating power supply: DC 12/24 V
Matching DC energy meter
ANet-2E4SM
·Embedded Linux operating system
·Network communication supports Socket mode
·Supports XML format compressed data upload
·Provides ARS encryption and MD5 identity authentication to meet security requirements
Supports resumable data transmission (breakpoint resume)
·Supports multiple communication protocols: ·Modbus (RTU), Modbus TCP, DL/T645-1997, DL/T645-2007, IEC 60870-5-101, IEC 60870-5-103, IEC 60870-5-104
·Compatible with various platforms
Compatible with Acrel-EIoT or third-party platform
Wireless router
AWT100-4G
Equipped with data acquisition and 4G upload capabilities, utilizing wireless transmission mode, connecting to the Acrel-EIoT Energy IoT Cloud Platform.
Compatible with Acrel-EIoT Cloud Platform
Acrel-EIoT
Equipped with functions such as data acquisition, data analysis, fault warning, data reporting, and equipment asset management. Supports APP-based QR code scanning for commissioning, which essentially enables a "commissioning-free" setup.
Supports both private cloud and public cloud deployment, with data hosting options available.
Post time: Jul-22-2026