The Footprint Coalition invested in Turntide, whose motors could reduce CO2 emissions by 25 percent.
For more than a century, the squirrel cage induction motor—which generates motion through a constantly rotating magnetic field—has been the workhorse of industrial HVAC units. In its heyday, the induction motor was state of the art, but by today’s standards, the word “quaint” comes to mind. Although variable-frequency drives (VFDs) have improved HVAC system efficiency by allowing the induction motor to rotate at multiple speeds, the design and efficiency of the motor itself haven’t changed a lot since its invention. Engineers have eked out as much performance as the laws of physics will allow these motors to deliver. Given that electric motors consume nearly half of the world’s electricity—a number that’s bound to increase with the proliferation of electric vehicles—it’s high time for a new motor technology. The Footprint Coalition, a consortium of investors committed to a sustainable future, is betting on Turntide and its Smart Motor system, which, according to third-party testing, uses up to 57 percent less electricity than a single-speed induction motor and 11 percent less than an induction motor controlled by a VFD. We’ll take a look at the motor’s technology and examine its performance and energy savings in a few scenarios.
Switched Reluctance Motors
Unlike an induction motor—which generates a constantly rotating magnetic field in the stator windings—its distant cousin, the switched-reluctance motor (SRM), sends a series of pulses to the stator windings to create torque and produce rotational motion. To operate the SRM at peak efficiency, the field pulse timing must be precisely controlled. Until recently, the technology needed to achieve that was too costly, but today’s microcontrollers are more than adequate for the task, making SRMs a logical choice to replace induction motors. The brushless DC (BLDC) motor offers similar performance advantages as an SRM, but the BLDC motor costs more and uses rare earth permanent magnets, which complicates the sourcing of materials. An SRM is made of steel and copper wire, making it more affordable, simpler, and free of rare earth metals.
Turntide Claims
Turntide says that its patented high-rotor pole switched reluctance motor (HRSRM) takes the SRM to new levels of performance, partly through its optimized ratio of rotor-to-stator poles, and offers the best overall balance of price, performance and reliability. Here’s the company’s promotional video explaining how the motor works:
Video courtesy of Turntide.
Turntide also claims that its motor has a nearly flat efficiency curve across all motor speeds, with the exception of low speeds, where it’s a little less efficient. Because of its simple stator windings, lack of rare earth materials, and solid steel rotor, the motor is easier to assemble, less expensive, and inherently more reliable than an induction motor or a BLDC motor. On the flip side, Turntide recognizes a few disadvantages of its HRSRM. Acoustically, it generates more noise than an induction motor or a BLDC. Also, its control algorithm is quite a bit more complicated. However, that’s only a problem for Turntide engineers, as the unit ships with a plug-and-play interface that can be easily customized by the end user.
Motor Control Unit
Each HRSRM is managed by a controller, which functions like a VFD, with the same reliability, cost, benefits and drawbacks. The Turntide controller also has built-in sensors for speed, torque and other parameters, and includes Internet of Things (IoT) capabilities for remote monitoring and control.
IoT Interface
Between the controller and the cloud lies a supervisor, which can oversee up to 10 motors on a Modbus interface or up to 20 motors via Wi-Fi. Each supervisor has 16 inputs and 12 outputs, which are user configurable and customizable. Turntide provides built-in application-specific control algorithms, such as regulating fan speed based on temperature. The IoT interface allows a facility manager (FM) to monitor all motor functions and parameters via a dashboard. This information can be further analyzed at the cloud level, where a machine learning algorithm can optimize the HVAC system. The FM can also receive text or email alerts, helping to facilitate predictive maintenance by providing early warnings when measurements indicate an impending fault.
Case Studies
A variety of businesses have replaced their induction motors with Turntide’s HRSRM, reporting energy savings, improved reliability and short payback periods. The industries include commercial office buildings, restaurants, biotech companies, grocery stores, fast-food operations and more. We’ll take a quick look at three case studies, but you can read more at Turntide’s Learning Center.
The owner of a 20,000-square-foot office building replaced the single-speed induction motors in its rooftop HVAC units with single-speed Turntide Smart Motor systems. Prior to the upgrade, the company installed energy monitors on the units to establish a baseline. After the retrofit, the HVAC fans used 30 percent less energy during heating and cooling modes and 87 percent less energy in ventilation mode, with an overall energy savings of 53 percent—a savings of 881 kWh per month. During the pilot phase, the IoT remote-monitoring feature alerted the facility manager of anomalies with the motor pulley that suggested an imminent failure. A technician replaced the pulley before it could cause the unit to malfunction. As a result, the building operators changed from a scheduled (preemptive) maintenance routine to a predictive maintenance model.
A biotech company headquartered in San Francisco, Calif. was looking to reduce maintenance costs, decrease production line downtime, and improve its environmental footprint. Taking advantage of the power company’s incentives for energy efficiency, the firm replaced the induction motors in three rooftop HVAC units with Turntide systems. Much like the previous example, comparisons with baseline data showed a dramatic reduction in fan energy use during ventilation mode (up to 90 percent) and significant energy savings in heating and cooling modes (up to 42 percent). Overall energy savings approached 63 percent, resulting in a payback period of just over two years. The IoT interface improved reliability. As a result, the company decided to replace the exhaust fan motors in its manufacturing labs as well.
A fast-food franchise noted a survey indicating that an overwhelming majority of customers prefer eating at green establishments. With razor-thin profit margins, the company looked for the “low hanging fruit” of energy efficiency: LED lighting. After reaping the benefits of efficient illumination, the company moved on to improve its HVAC system. Upgrading a pair of 3 hp motors in its rooftop units allowed the restaurant to reduce its HVAC energy consumption by 70 percent with no impact on performance or comfort levels. In addition to the improved efficiency of the motors themselves, the IoT function helped to ensure that the units only powered up when necessary. The facility reported a payback period of 1.6 years.
Investing in Sustainable Technology
The Footprint Coalition was founded by “Iron Man” portrayer Robert Downey, Jr. He explained his rationale behind assembling this team of venture capitalists for the purpose of investing in sustainable technology: “I’ve been dealing with false existential threats in the Marvel Universe and thought it was time to think about real ones.”
Not all superheroes wear costumes.