By Jay A. Popp
Sustainable design has become the popular buzzword in design and begins with the design intent. It is applied to the basic architecture of a building and is an optimization of the building design, the systems contained with the building, and the selection of materials used to construct the building. It is also commonly associated with obtaining LEED certification for a building.
Just as each building is a unique design, so, too, is the proper elevator solution for that building. Sustainable design or optimization of the elevator system begins with an efficient lobby design to optimize pedestrian flow, wayfinding, passenger loading and unloading at the main floor lobby, and sufficient numbers of elevators to minimize passenger waiting times during peak traffic periods while meeting the handling capacity requirements of the building tenancy. This is further tempered by the quality of the surrounding buildings, cultural expectations, and positioning of the building in the local and/or world real estate market.
Generally, traditional elevator design has been based on providing an equal number of elevators in each group or zone, thus simplifying the building core design. This philosophy, while still valid today in some buildings, may not be the most efficient design. Optimization could potentially be based on the use of a greater number of slower- speed elevators in the low-rise zone of a multizone building to reduce the number of high-speed elevators in the upper zone(s), reducing initial capital costs and maximizing rentable area and returns in the upper zone(s). In large buildings, optimizing the passenger handling capability of the elevator systems can include: "double deck" elevator systems with two elevator cabins in the same hoistway permanently connected together; specialized elevator systems with two elevator cabins in the same hoistway operating independently; and sky lobbies.
Sky lobbies, in effect, provide the opportunity to stack one multizone building on top of another in ultra high-rise projects. Passengers are transported from the main lobby to the sky lobby via large-capacity, high-speed shuttle elevators providing access to the next multizone groups of "local" passenger elevators. Mixed-use or ultra high-rise buildings may have one or more sky lobbies providing dedicated access to each of the tenancy types.
Sustainable design of the elevator systems is influenced by the sophistication of the elevator control and the quality of the power conversion unit selected. Modern elevator microprocessor control systems offered by all major manufacturers throughout the world come with some form of "learning" or advanced decision-making capabilities (such as genetic algorithm and fuzzy logic) to optimize system efficiencies. Sophisticated "Destination Control Selection" (DCS) systems offer further optimization by providing the ability for people to register their destination floors from a terminal in the elevator lobby prior to boarding the elevator. This information is then communicated to the elevator control system, which instantly assigns each person's destination to a particular elevator car. Persons arriving in the lobby are grouped together to minimize the number of stops that each elevator must make during any given trip up into the building. The result is that a greater number of persons can be handled with fewer stops, particularly during the morning up-peak traffic condition in an office building as persons arrive to start the business day.
In addition, special control features are becoming available that allow elevators to operate at higher speeds during off-peak traffic periods. Controls are also available that allow regenerative power to be temporarily stored and transferred to other elevators in the group during emergency standby power conditions, thereby providing additional elevator capacity for use by firefighters or building evacuees.
Modern low-, mid-, and high-rise buildings today also use efficient AC Gearless electric hoist motors. Further, modern power conversion units as well as those provided in buildings constructed within the past 20 years were provided with some form of regenerative power capabilities. Recent advances in electrical component design and manufacturing processes have also enabled several manufacturers to offer sophisticated Pulse Width Modulation (PWM) or Power Factor One (PF-1) drives that provide maximum regeneration capabilities. As PF-1 drives are not yet standard with all elevator manufacturers, they should be specified not only for optimal energy efficiency but also for the value-added benefit of substantially lower RFI emissions.
Jay A. Popp is executive vice president at Lerch Bates Inc., an internationally recognized independent consulting company specializing in vertical transportation, façade access, and materials handling systems.