The power output of a wind turbine is largely dependent on two factors: the wind speed and the height of the tower. Currently, the tallest wind turbine in the world is the Nordex N131/3300, located in Hausbay, Germany, and it stands 164 meters tall (230 counting the rotors) with a capacity of 3.3 MW. Clearly, it is advantageous for industrial windmills to be as tall as possible to maximize electricity generation. However, taller towers and rotors confront issues with installation and maintenance; for any type of service work, taller wind turbines require tower elevators.
Wind turbine tower elevators differ from conventional elevators found in buildings and other structures, and thus cannot meet the same requirements and standards. This is because lifts and elevator shafts in buildings contain many welds, which, if incorporated into the tower of a wind turbine, could compromise its structural integrity and worker safety. Instead, windmill service lifts are cable-driven and guided.
Another unique characteristic of wind turbine elevators is the environmental factors that they are exposed to, an anticipated byproduct of permanently being placed inside technology that functions from air currents. These service lifts undergo the effects of extreme temperatures, humidity variations, and substantial horizontal motions. Due to this, these elevators are not expected to maintain full compliance with ASME A17.1 – Safety Code for Elevators and Escalators, since doing so would be impractical in many instances.
However, despite not abiding strictly to general elevator requirements, wind turbine service lift guidance calls for similar considerations. This includes specifications for counterweights, lift cars, standard railings, and lighting, along with the allowable stresses, safeguarding, and identification marking of such equipment. This also includes recommended dimensions, such as those for clearances addressed in the following figure:
The above measurements, along with all other considerations relating to wind turbine tower elevators, are addressed in ASME A17.8-2016/CSA B44.8-2016 – Standard for wind turbine tower elevators, the official code for the service lifts.
This is the first edition of the standard, as wind turbine tower elevators used to be covered by past revisions of ASME A17.1. Prior to its publication, requirements for service lifts and wind turbines varied from state to state, and some states still require official approval by an elevator inspector before a service lift is used in a tower. It is anticipated that the publication of ASME A17.8-2016/CSA B44.8-2016 – Standard for wind turbine tower elevators will allow for a unified certification process in both the United States and Canada.
ASME A17.8-2016/CSA B44.8-2016 – Standard for wind turbine tower elevators is now available on the ANSI Webstore.
1. The American Society of Mechanical Engineers (ASME) and CSA Group, ASME A17.8-2016/CSA B44.8-2016 – Standard for wind turbine tower elevators (New York: ASME, 2016), 59.