Introduction to High Efficiency Elevators
As building codes push for greater energy efficiency, elevators are following suit. While elevators are vital in modern buildings, they are also big energy consumers, accounting for up to 10% of a building’s total energy use. Furthermore, elevator energy consumption can be more significant in high-performance buildings where other energy use categories have been minimized.
High-efficiency elevators available in the market feature improved controls, hardware, and other systems that help improve energy efficiency, are more compact, and even generate electricity through regenerative technology. High-efficiency and conventional elevators may differ by their type (hydraulic or traction), the presence or absence of gearing, the drive types they use, or their ability to regenerate power. According to the American Council for an Energy-Efficient Economy (ACEEE), the best opportunities to save energy, more specifically for hydraulic elevators, are optimizing cab efficiency, maintaining proper valve adjustment, and employing sequential standby modes identified in the ISO standards. These changes can seem modest, but the potential exists to cut hydraulic elevator energy use in half.
Energy-Efficiency Elevator Components
Regenerative Drives
High-efficiency traction elevators often use regeneration drives to offer the greatest efficiency
possible. Regenerative systems turn the motor backward during descent so that it acts as a generator, and the resulting power is sent to uses within the building. Regenerative drives on the market today in North America are offered by most of the major elevator manufacturers. Modern component costs have dramatically reduced regenerative drive costs to nonregenerative prices. Regenerative systems can recover up to 30 percent of an elevator’s total energy consumption and are an improved technology over nonregenerative drives.
Energy-Efficient Motors
Higher-efficiency elevators implement gearless motors, which directly attach the wheel to the electric motor. In traditional geared motors, the gearbox is attached to the motor, causing
wear and tear, friction and resistance, leading to significant energy loss. Getting rid of the gear leads to a longer lifespan for the equipment and lowered maintenance costs. Although geared elevators cost less, they cannot operate as swiftly as gearless elevators, which results in poorer performance for mid- and high-rise buildings. Geared elevators can travel up to 500 feet per minute (fpm), whereas gearless elevators can travel as fast as 1,200 fpm. Speeds of at least 700 fpm are often preferred for high-rises and some mid rises. Passengers benefit from a quieter ride and smoother operation due to the advanced technology of gearless elevators.
Smart Elevator Control Systems
Utilizing sensors and Internet of Things (IoT) connectivity, smart elevator control systems can
help ensure energy-efficient elevator operation. Newer controls provide more convenient, efficient operation for mid- to high-rise buildings. Old, outdated controls consisting of electromechanical relays inherently can’t provide the same level of functionality as smart control systems. With smart control systems, machines can gather data to make informed decisions such as predicting traffic patterns, adjusting waiting times, and managing energy distribution efficiently. Based on the real-time data smart elevators collect, they optimize energy efficiency by adjusting lighting, ventilation, and other systems.
New smart elevator controls are microprocessor-based and are controlled by software that may incorporate algorithms to save energy, typically achieving around 5% savings compared to systems without these controls. This technology optimizes elevator placement to meet demand, reduce wait times, and automatically shuts down unnecessary cars when they aren’t needed. In addition, smart elevator control systems allow for remote monitoring of elevators and predicts when maintenance needs will arise. This allows for issues to be prevented or addressed before they become serious, cause a breakdown, and add-on unexpected costs.
LED Lighting
Utilizing LED lighting in elevators not only improves energy efficiency but also extends the
lifespan of the lights. LED lights are more efficient than incandescent lights because most of the energy used by an LED creates light, whereas incandescent lights lose a significant amount of energy as heat. This reduces both energy consumption and heat gain, making LED lighting a more sustainable choice.
Standby Mode
When an elevator sits idling for a set period, standby mode activates, shutting off non-essential systems to conserve energy. This feature not only reduces energy consumption but also prolongs the elevator’s lifespan by minimizing wear and tear during inactivity. Using standby mode during low-demand periods is crucial for optimizing energy efficiency and lowering overall energy use in a building.
What Are the Benefits?
- Energy cost savings: High efficiency elevators use advanced technologies like regenerative drives, which convert the energy generated during braking into electricity that can be used elsewhere in the building and can reduce energy consumption by up to 50%.
- Space saving: Eliminates the need for a machine room, allowing for more flexible building designs.
- Improved performance: Gearless motors and advanced controls enhance reliability, providing smoother and quieter rides.
- Longevity: Advanced controls predict maintenance needs, reducing unexpected breakdowns and extending the elevator’s lifespan.
- Reduced size of electrical service: Elevators that have lower power requirements may reduce installation costs if the required capacity of the electrical service is reduced.
What Are the Challenges/Constraints?
- Costly replacements: High performance elevator maintenance can be more complex and expensive compared to traditional elevator systems.
- Higher initial costs: Advanced technology requires a higher initial upfront investment.
- Specialized knowledge: Installation and maintenance of advanced technologies requires technical expertise.
- Integration challenges: Advanced technologies may require additional effort to integrate with existing building systems, especially in older buildings.
Efficiency Codes and Standards
The current California Title 24 energy code, under Section 120.6(f): Mandatory Requirements for Elevators, addresses only lighting and ventilation within elevators. However, ANSI/ASHRAE/IES Addendum cf to ANSI/ASHRAE/IES Standard 90.1-2019 sets minimum efficiency levels for cab lighting, ventilation, energy use, and introduces standby-mode requirements. While these are considered industry standards, they have yet to be adopted into California building codes. Efforts to standardize elevator energy use have also led to the development of VDI 4707 and the broader ISO 25745 standards, which are internationally recognized by experts.
What Are the Qualifications for CEDA Inducement?
To support electrification and decarbonization efforts in buildings and the grid, CEDA offers inducements for installing elevator systems that exceed energy code requirements.
The ISO 25745 standard provides a method to estimating energy consumption and classifying the energy efficiency of elevators – whether new, existing, or modernized. The rating system, ranging from A to G, accounts for both travel and standby energy usage, factoring in variables like travel height, speed, load, and frequency of use. To qualify for CEDA inducements, projects must achieve an elevator efficiency classification of at least Class C or better, as defined by the ISO 25745-2 standard.
Energy Efficiency Letter Grade Classes per ISO Standard 25745-2:2015
In addition to the ISO letter grade class, to be eligible for CEDA inducement, elevators must also achieve a performance level 6 or better for both specific running energy (ISO 25745-2, Table 5) and idle/standby power (ISO 25745-2, Table 6). These performance levels reflect the amount of energy consumed while the elevator is running and in idle/standby mode, based on factors such as travel distance and load.
These classifications enable the comparison of different elevator systems, helping building owners choose elevators with optimal energy efficiency to meet sustainability goals.
Eligibility Requirements:
- Enroll in CEDA
- Be located within the SCE, SoCal Gas, PG&E or SDG&E territory
- Designed to fit the ISO classification and performance levels mentioned above
- Integrate the elevator into the building’s energy management system or be equipped with monitoring systems to track energy usage
- Provide elevator design documentation (including calculations and cost data), selection criteria, alternatives considered, and any design or construction challenges
- Participate in on-site verification and possible data logging of the system
- Applicable only to non-residential and high-rise multifamily buildings with three or more floors above grade
Project may be selected by PG&E for a future case study
