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Microenvironmental Control and Thermal Barrier Curtains/Shades for Long-Haul Trucks

National Renewable Energy Laboratory

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Technology Marketing Summary

Cab climate conditioning is one of the primary reasons for idling the main engine in a long-haul truck during driver rest periods. In the United States, long-haul trucks (trucks that travel more than 500 miles per day) use approximately 667 million gallons of fuel annually for rest period idling[1]. Including workday idling, over two billion gallons of fuel are used annually for truck idling[2]. Idling represents a zero freight efficiency operating condition for the truck. As awareness of idle fuel use has increased, federal regulation and incentives have been created. An example is the idle reduction technology credit in the Heavy-Duty Greenhouse Gas Emissions Standards, which began in 2014[3]. Increased awareness has also spurred implementation of many stringent state and city anti-idling regulations[4].

By reducing thermal loads and improving the efficiency of climate control systems, there is a great opportunity to reduce fuel use and emissions associated with idling. Enhancing the thermal performance of cab/sleepers will enable smaller, lighter, and more cost-effective idle reduction solutions. In addition, if the fuel savings from new technologies provide a one- to three-year payback period, fleet owners will be economically motivated to incorporate the new technologies. Therefore, financial incentive provides a pathway to rapid adoption of effective thermal load and idle reduction solutions.

[1] Stodolsky, F., Gaines, L., Vyas, A. Analysis of Technology Options to Reduce the Fuel Consumption of Idling Trucks. Argonne National Laboratory, ANL/ESD-43, June 2000.

[2] Gaines, L., Vyas, A., Anderson, J., “Estimation of Fuel Use by Idling Commercial Trucks,” 85th Annual Meeting of the Transportation Research Board, Washington, D.C., January 22-26, 2006, Paper No. 06-2567.

[3] “Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles, Final Rule.” Federal Register 76 (15 September, 2011): 57106-57513.

[4] “Idling Regulations Compendium, American Transportation Research Institute.” Accessed on 9/16/2013.



Engineers at the National Renewable Energy Laboratory (NREL) have developed a microenvironment control system to decrease climate control loads while improving comfort. Called “The Comfort Shower,” this invention uses an overhead supply manifold with directed outlets and near occupant return lines built into the sleeper bed area. Air exits through the supply manifold and is drawn into the return lines near the occupant. This configuration limits the mixing and entrainment of air from outside the intended climate control zone creating a smaller conditioned space within the sleeper compartment without the need for physical barriers. When the occupant(s) is sleeping in the truck the air flows down along the length of the person with returns along the side of the bed (Figure 1).

By limiting the conditioned space only to the air in close proximity to the occupant, the system needs to add or remove less energy from the air stream, thus improving the HVAC efficiency. The reduced air mass also makes it easier to control air conditions (temperature, humidity, etc.) to meet the occupant needs, improving thermal comfort.

Additionally, engineers at NREL have developed an improved thermal barrier which also acts as a privacy shade and cab-to-sleeper separator curtain to provide the occupants with the ability to isolate a spatial region of the vehicle and control the lighting/privacy of an area. Thermal performance as a design criterion for existing curtains and shades is often limited, with the design focus primarily on privacy and cost. The thermal barrier curtains and shades developed at NREL differ significantly from existing designs in their ability to provide a significant reduction in both heating and cooling climate control loads of the vehicle for long-haul truck driver rest periods.

  • Limits the volume of conditioned air needed to keep the occupant comfortable
  • Adjustable vents which can be moved to improve comfort
  • Can be used for one or more occupants
  • By limiting the entrainment of air from outside the microenvironment climate control zone, fresh air can be provided more directly to the occupants, reducing the total outside air required to meet occupant needs
  • Reduced thermal inertia of the smaller climate controlled zone will also respond faster to climate control, providing opportunity for better transient control response
  • Reduced controlled air volume allows for easier humidity control of the conditioned space
  • Comfort Shower can reduce the sensitivity of the climate control loads to the sleeper curtain and may allow for a more open environment without increasing loads
Applications and Industries
  • Truck cab/sleeper climate control
  • Heating
  • Cooling
  • Localized ventilation
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Application 20150290998
Systems and methods for providing conditioning to a space within an environment are provided. Such a system may include a solid boundary, at least one air supply aperture configured to direct a conditioned airflow towards the solid boundary, and at least one air return aperture configured to receive a return airflow. At least one of the conditioned airflow or the return airflow may create an air boundary, such that the air boundary and the solid boundary define the space within the environment. At least a portion of the conditioned airflow may enter the space, and at least a portion of the return airflow may exit the space, thereby conditioning the space.
National Renewable Energy Laboratory 04/09/2015
Application 20170100990
An aspect of the present disclosure is a thermal barrier that includes a core layer having a first surface, a second surface, and a first edge, and a first outer layer that includes a third surface and a second edge, where the third surface substantially contacts the first surface, the core layer is configured to minimize conductive heat transfer through the barrier, and the first outer layer is configured to maximize reflection of light away from the barrier.
National Renewable Energy Laboratory 10/12/2016
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 14-06, 15-54ProposedAvailable12/28/201512/28/2015

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To: Eric Payne<>