High Performance Elevators
Elevators: High Performance vs. Conventional
Passenger and freight elevators with efficiency features such as gearless permanent magnet synchronous motors, traction belts instead of steel ropes, dispatch control, and motors with regenerative braking.
Item ID: 471
Transportation--Elevators & Escalators
Technical Advisory Group: 2014 Commercial Building TAG (#9)
Average TAG Rating: 2.71 out of 5
TAG Ranking Date: 03/17/2014
TAG Rating Commentary:
- Unless this is combined with integrated PV I think there are better solutions.
- Technology is commercially available but with very low penetration.
- How new are these technologies?
- Also offer several non-energy benefits such as increases comfort, less waiting and travel time.
Losses in an elevator system include hydraulic and gear, friction, transmission, motor, controller, and brake losses. Recent advances are directed towards loss reduction. KONE developed a gearless vector drive that uses a permanent magnet synchronous motor (PMSM) that can be made in a compact, disc-like shape that allows it to be integrated into the traction sheave. No machine room is necessary, resulting in space and weight savings. Variable speed PMSM motors provide high efficiencies in multi-pole slow speed/high torque designs resulting in no need for gears. Kone claims energy savings of up to 40% compared to geared elevators and over 60% when compared to hydraulic lifts. Kone now offers a gearless traction design for the low-rise applications (up to 7 stories) that previously were served by hydraulic systems. Replacement of hydraulic system at their time of renovation saves a great deal of additional energy as these systems do not employ counterweights to offset the lifting requirements for the car.
Otis developed their Gen2 system, replacing steel ropes with a flexible traction belt consisting of ultra-thin (3-mm) steel fibers encapsulated in a polyurethane sheath. Sheave diameter was limited by the bending radius of the steel ropes, but advanced materials and innovative rope construction has resulted in reducing sheave size and rope weight. Flat traction belts allow the use of a four-inch rather than a 30-inch diameter drive sheave for the company's geared or gearless traction elevator systems. A smaller motor can be used to meet system power requirements. Otis claims as much as a 50% reduction in energy use with a gearless machine and a variable speed permanent magnet (PM) motor with advanced traction belts as compared to a conventional geared machine.
Magnetek also introduced their Quattro AC and DC elevator drives with regenerative braking, which they claim will produce energy savings of 40% compared with DC motor generator sets and 25% when compared with DC-SCR (silicon-controlled rectifier) drives. Regeneration is not always cost effective, especially in mid-rise buildings with low traffic.
While simple payback for these elevators is at least 50 years, the non-energy benefits of speed and comfort as well as reduced maintenance and space requirements (no penthouse or elevator room) are attractive to some buyers. The simple payback for installing high performance elevators in taller buildings is longer due to the higher efficiency of standard practice.
Baseline Description: Traditional Hydraulic Low-Rise Elevator
Baseline Energy Use: 16227 kWh per year per unit
Energy savings from improving elevator efficiency depend heavily upon the baseline technology plus usage and traffic patterns. Critical assumptions include the weight (capacity) of the elevator, loading (persons or weight per trip), the number of trips, and the average lift or height per trip. Generally, a hydraulic elevator is assumed for low-rise applications with a DC traction motor drive is taken as the baseline case for mid and high-rise buildings.
Assumptions for energy savings estimates are: hydraulic elevator with a DC-traction motor a load of 3500 pounds, an elevator speed of 300 feet per minute, 200,000 starts per year, and an average travel height of 37 feet in a four-floor building.
Kone estimates an annual energy consumption of 16,227 kWh/year for the upgrade of a traditional hydraulic elevator with a gearless traction unit requiring only 3,308 kWh/year for an energy savings of 12,919 kWh annually (79.6%). The advanced elevator is equipped with their permanent magnet synchronous motor with regenerative braking.
Manufacturer's Energy Savings Claims:
"Typical" Savings: 30%
Savings Range: From 12% to 63%
These claims are from Kone.
Best Estimate of Energy Savings:
"Typical" Savings: 80%
Low and High Energy Savings: 12% to 80%
Energy Savings Reliability: 4 - Extensive Assessment
Elevators account for 2% to 4% of a building's energy consumption. Studies conducted for the European Commission indicate that energy savings of up to 63% are obtainable through use of "best available technology" instead of conventional hydraulic or a geared traction lift powered by a DC motor.
In actual operation, energy savings are dependent upon a number of variables including the baseline technology, car capacity (nominal load), travel speed (feet per minute), travel distance, number of floors served, and number of starts per year. Savings increase when the new technology includes regenerative braking. The "typical" 79.6% savings cited is due to the use of a Kone EcoSpace gearless traction design instead of a traditional geared traction system in a 3,500 lb capacity elevator in a 4 floor building.
Kone mocked up a number of "Elevator Energy Calculation Reports" in March of 2014 that examine potential savings from low-rise, mid-rise, and high rise elevator applications. The low rise elevator improvement produces an energy savings of 12,920 kWh/year per elevator (a 79.6% savings). The savings come from replacement of a hydraulic elevator with an EcoSpace Gearless traction unit. Basic assumptions include a 4-story building, 3500 pound nominal load, speed of 150 fpm, travel distance of 37 feet, and 200,000 starts per year. The mid-rise scenario produces an energy savings of 5,801 kWh annually (42.2%) through use of a MonoSpace gearless traction design instead of a geared traction system. Assumptions include a 16-story building, nominal travel speed of 350 fpm, a travel distance of 147 feet, and 200,000 starts per year. The high-rise comparison produces an annual energy savings of 1,745 kWh per year (12.8%). Assumptions for this analysis included an EcoSystem MR for the more efficient elevator versus a gearless traction system with a SCR static converter. The 32-story high-rise elevators have a speed of 700 fpm with an average travel distance of 300 feet. Again, a 3500 pound nominal load is assumed with 200,000 starts per year. In all cases, the Kone solution featured regenerative drives.
Energy savings come not only from changing the hoisting motor/drive system to permanent magnet motors with regenerative drives but also from reducing or eliminating standby losses due to elevator control systems, lighting, ventilation, floor displays, and operating consoles on each floor and inside the elevator cabin. Elevator car lighting can be changed from incandescent or fluorescent to LED lighting technologies. LEDs can be dimmed or cycled on/off without impacting operating lifetime. Elevators can be put in a low energy mode when not in use. During low demand periods, one or more elevators within a group can be shut down without compromising service quality. Controls for multiple elevators can be optimized to enhance both service effectiveness and energy efficiency.
Energy Use of Emerging Technology:
3,245.4 kWh per unit per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
According to the National Elevator Industry, Inc., there are 900,000 elevators in the U.S (NEII, 2014). If we take 4% of that, assuming the number of elevators is proportional to the population, that equals approximately 36,000 elevators in the Northwest. During the time that most existing elevators were installed, the dominant technology has been hydraulic. Assuming that 25% of existing elevators in the Northwest are hydraulic and serve 3 or more floors (see WA state breakout of elevators by type, below), yields a potential retrofit population of approximately 9,000 hydraulic elevators.
Note: The WA Department of Labor and Industries performs elevator safety inspections and maintains an elevator database for the state. Of the 26,474 elevators in their database, 11,094 are passenger hydraulic elevators and 6,023 of these operate to serve 3 or more floors. (The remainder are freight elevators, wheelchair lifts etc.). All could be upgraded to gearless traction elevator drives at their time of replacement or upgrading.
Also note that ACEEE states that the U.S. installs about 15,000 to 20,000 elevators annually (Sachs, 2015). Prorating by population yields about 5% x 17,500 = 875 elevator installations per year.
Regional Technical Potential:
0.12 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: unit
Emerging Technology Unit Cost (Equipment Only): $116580.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $24968.00
Baseline Technology Unit Cost (Equipment Only): $61890.00
Elevator modernization may require six figures per elevator. The time to upgrade is when ordering elevators for a new facility or when modernization, renovation, or upgrading is required. Indicators that modernization is required include elevators no longer meeting code requirements, when they are no longer supported by the manufacturer, when the elevator no longer meets service expectations, or when maintenance costs and frequency increase and reliability suffers.
From RS Means Facilities Construction Cost Data (2014) the total cost of a geared traction passenger elevator with 3500 lbs capacity is $141,550, including equipment, installation, overhead, and profit. A hydraulic passenger elevator with a speed of 150 fpm, 4 stops, and a 3500 lb capacity car would have a total cost of $88,925 including equipment, installation, overhead and profit.
Simple payback, new construction (years): 46.8
Simple payback, retrofit (years): 121.2
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.