Between July 2020 and Feburary 2022, Slipstream conducted a field investigation of switched reluctance motors in a project funded by Commonwealth Edison (ComEd) Energy Efficiency Program.
For this pilot, the Turntide Smart Motor System technology was used at a commercial office building in Schaumburg, Illinois and two retail stores in Countryside and Norridge, Illinois. Switched-reluctance motors, or SRMs, operate by reluctance torque, and their stator poles are driven by DC power, resulting in higher-efficiency operation compared to constant-speed induction induction motors. Turntide paired its high-rotor SRM with a software-driven-motor controller to make a “smart” or software-controlled system: the SRM System. The SRM System can replace fan motors in RTUs and some other HVAC equipment from 1 to 20 hp capacity.
The SRM System is new to the market in the last few years; so far two other parties have performed studies of the SRM System performance. In 2018, Southern California Edison performed a study (SCE 2018) comparing the performance of a 3 hp SRM System with two scenarios: a 3 hp induction motor with VFD in a laboratory setting and a 3 hp single-speed induction motor in a field setting. A 2020 study (NREL 2020) performed by the National Renewable Energy Laboratory (NREL) for ComEd compared the performance of three RTU technologies, one of which was the SRM System, using simulation methods. The results of these studies are discussed in the Findings section of this report alongside our own results, providing a broader understanding of field data related to this technology.
This report investigates the benefits and potential of the SRM System. The primary quantitative benefits we measured are energy savings and peak power savings. Two additional benefits of the SRM System are flexible-remote configuration and ongoing data-collection capabilities, both making operational abnormalities visible and addressable to both the motor manufacturer and, through a web portal, the building owner/operator.
The primary objective of this study is to compare the energy usage of the SRM System to constantspeed induction motors in rooftop unit (RTU) supply fans, in terms of energy performance and installation procedure. This report examined the following key questions:
- What is the typical annual energy (kWh) savings of SRM System in RTU supply-fan motors at a commercial property? What is the corresponding peak power (kW) reduction?
- What effect, if any, does the SRM System have on total RTU energy consumption?
- What is the estimated annual energy (kWh) savings for the SRM System for each of the building and system types represented in this study in ComEd territory?
- What is the total resulting technical potential for this technology in ComEd territory?
- Are there any aspects of installation or operation of the SRM System (from the perspective of building owners and/or contractors) that could affect the ease and scale of future program deployment of SRM technology?