Assessing the National Off-Cycle Benefits of 2-Layer HVAC Technology Using Dynamometer Testing and a National Simulation Framework

Chad Baker, Matthew Moniot, Brennan Borlaug, Jason Lustbader, Saad Akhtar, Forrest Jehlik, Scott Agnew, Jason Lee, Insu Lee, Jinho Ha

Research output: Contribution to conferencePaperpeer-review


Some CO2-reducing technologies have real-world benefits not captured by regulatory testing methods. This paper documents a two-layer heating, ventilation, and air-conditioning (HVAC) system that facilitates faster engine warmup through strategic increased air recirculation. The performance of this technology was assessed on a 2020 Hyundai Sonata. Empirical performance of the technology was obtained through dynamometer tests at Argonne National Laboratory. Performance of the vehicle across multiple cycles and cell ambient temperatures with the two-layer technology active and inactive indicated fuel consumption reduction in nearly all cases. A thermally sensitive powertrain model, the National Renewable Energy Laboratory's FASTSim Hot, was calibrated and validated against vehicle testing data. The developed model included the engine, cabin, and HVAC system controls. Validation of component thermal models and engine efficiency ensured accurate thermal dynamics, fuel consumption, and two-layer benefit. The real-world benefit of the two-layer technology was calculated by simulating the validated powertrain model across a representative test matrix comparing performance with and without the two-layer system. Simulation across the test matrix revealed a real-world representative benefit of 0.0835%. Analysis of test matrix results at the regional level revealed the most benefit in cold climates and rural regions. Mean results across cycle length sensitivity simulations revealed a larger real-world benefit of 0.0872%. These benefit values can be considered a more accurate assessment of real-world technology performance. Future work is planned to explore the requisite number of drive cycles to ensure the full technology benefit is captured.

Original languageAmerican English
Number of pages15
StatePublished - 11 Apr 2023
EventSAE 2023 World Congress Experience, WCX 2023 - Detroit, United States
Duration: 18 Apr 202320 Apr 2023


ConferenceSAE 2023 World Congress Experience, WCX 2023
Country/TerritoryUnited States

Bibliographical note

Publisher Copyright:
© 2023 SAE International; UChicago Argonne, LLC.

NREL Publication Number

  • NREL/CP-5400-84477

Other Report Number

  • SAE Technical Paper No. 2023-01-0942


  • 2-layer
  • climate control
  • dual layer
  • off-cycle benefits
  • vehicle HVAC
  • vehicle thermal management


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