Robert Dell

Director, Center for Innovation and Applied Technology

Regenerative Braking in Elevators

 The Energy Potential of Regenerative Drive Elevator Technology
PON 2244, Environmentally Preferred Power Systems Technologies

Prof. Robert Dell, Lead Research Scientist


 The project is a Category A: Technological Facilitation Study to assess the technological,
operational and economic potential of regenerative drive elevator technologies (“regen”) to generate
environmentally benign electricity. In elevators equipped with regen, power is generated when a
downward traveling mass, either the elevator car or counterweight in a traction system, is greater than
that of the ascending counterweight or car. The project will address a range of reasons why regen
technology has not proliferated in retrofit situations.

        The C.V. Starr Research Foundation at The Cooper Union for the Advancement of Science and Art (CV
Starr) provides administrative and technical leadership for the study project. Subcontractors and
substantial contributors include New York City-based Energy Investment Systems (EIS), which supplies
policy analysis and coordinates industry participation, and the Industrial Technology Assistance
Corporation (ITAC), which donates business development and planning specialists to the project.
Additional team members include elevator experts, building managers, labor leaders and public officials
who are making in-kind contributions of their time and expertise to the project.

   There is no accepted specific measurement and instrumentation protocol for regenerative braking (regen) power. The main reason is that there as yet has been no published definitive study meeting the necessary research standards. A formal multiple-site and multiple-data collection approach is needed using accepted standards of precision and appropriate instrumentation. Both AC and DC power, in consumption, dissipation and regenerative scenarios should be measured at appropriate multiple points in the elevator power system.

    Measuring elevator regenerative braking potential requires extremely precise assessments of power and power consumption (energy) across both long and short time intervals to establish energy consumption time trends. In a long term time frame, this can include hourly, daily, weekly monthly, seasonal and annual energy consumption patterns. Power fluctuations from dynamic and regenerative braking for time periods as short as milliseconds must be accurately measured, documented and analyzedto truly understand the energy savings potentials.