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Title: Barriers to the Application of High-Temperature Coolants in Hybrid Electric Vehicles

Abstract

This study was performed by the Oak Ridge National Laboratory (ORNL) to identify practical approaches, technical barriers, and cost impacts to achieving high-temperature coolant operation for certain traction drive subassemblies and components of hybrid electric vehicles (HEV). HEVs are unique in their need for the cooling of certain dedicated-traction drive subassemblies/components that include the electric motor(s), generators(s), inverter, dc converter (where applicable), and dc-link capacitors. The new coolant system under study would abandon the dedicated 65 C coolant loop, such as used in the Prius, and instead rely on the 105 C engine cooling loop. This assessment is important because automotive manufacturers are interested in utilizing the existing water/glycol engine cooling loop to cool the HEV subassemblies in order to eliminate an additional coolant loop with its associated reliability, space, and cost requirements. In addition, the cooling of power electronic devices, traction motors, and generators is critical in meeting the U.S. Department of Energy (DOE) FreedomCAR and Vehicle Technology (FCVT) goals for power rating, volume, weight, efficiency, reliability, and cost. All of these have been addressed in this study. Because there is high interest by the original equipment manufacturers (OEMs) in reducing manufacturing cost to enhance their competitive standing, themore » approach taken in this analysis was designed to be a positive 'can-do' approach that would be most successful in demonstrating the potential or opportunity of relying entirely on a high-temperature coolant system. Nevertheless, it proved to be clearly evident that a few formidable technical and cost barriers exist and no effective approach for mitigating the barriers was evident in the near term. Based on comprehensive thermal tests of the Prius reported by ORNL in 2005 [1], the continuous ratings at base speed (1200 rpm) with different coolant temperatures were projected from test data at 900 rpm. They are approximately 15 kW with 103 C coolant and 20 kW with 50 C coolant. To avoid this 25% drop1 in continuous power, design changes for improved heat dissipation and carefully managed changes in allowable thermal limits would be required in the hybrid subsystems. This study is designed to identify the technical barriers that potentially exist in moving to a high-temperature cooling loop prior to addressing the actual detailed design. For operation at a significantly higher coolant temperature, there were component-level issues that had to be addressed in this study. These issues generally pertained to the cost and reliability of existing or near-term components that would be suitable for use with the 105 C coolant. The assessed components include power electronic devices/modules such as diodes and insulated-gate bipolar transistors (IGBTs), inverter-grade high-temperature capacitors, permanent magnets (PM), and motor-grade wire insulation. The need for potentially modifying/resizing subassemblies such as inverters, motors, and heat exchangers was also addressed in the study. In order to obtain pertinent information to assist ORNL researchers address the thermal issues at the component, module, subassembly, and system levels, pre-existing laboratory test data conducted at varying temperatures was analyzed in conjunction with information obtained from technical literature searches and industry sources.« less

Authors:
 [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Power Electronics and Electric Machinery Research Facility
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
974604
Report Number(s):
ORNL/TM-2006/514
VT0302000; CEVT022; TRN: US201008%%501
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
33 ADVANCED PROPULSION SYSTEMS; CAPACITORS; COOLANT LOOPS; COOLANTS; DESIGN; EFFICIENCY; ENGINES; HEAT EXCHANGERS; INVERTERS; MANUFACTURERS; MANUFACTURING; MOTORS; HYBRID ELECTRIC-POWERED VEHICLES; PERMANENT MAGNETS; RELIABILITY; TRANSISTORS; VELOCITY

Citation Formats

Staunton, Robert H, Hsu, John S, and Starke, Michael R. Barriers to the Application of High-Temperature Coolants in Hybrid Electric Vehicles. United States: N. p., 2006. Web. doi:10.2172/974604.
Staunton, Robert H, Hsu, John S, & Starke, Michael R. Barriers to the Application of High-Temperature Coolants in Hybrid Electric Vehicles. United States. doi:10.2172/974604.
Staunton, Robert H, Hsu, John S, and Starke, Michael R. Fri . "Barriers to the Application of High-Temperature Coolants in Hybrid Electric Vehicles". United States. doi:10.2172/974604. https://www.osti.gov/servlets/purl/974604.
@article{osti_974604,
title = {Barriers to the Application of High-Temperature Coolants in Hybrid Electric Vehicles},
author = {Staunton, Robert H and Hsu, John S and Starke, Michael R},
abstractNote = {This study was performed by the Oak Ridge National Laboratory (ORNL) to identify practical approaches, technical barriers, and cost impacts to achieving high-temperature coolant operation for certain traction drive subassemblies and components of hybrid electric vehicles (HEV). HEVs are unique in their need for the cooling of certain dedicated-traction drive subassemblies/components that include the electric motor(s), generators(s), inverter, dc converter (where applicable), and dc-link capacitors. The new coolant system under study would abandon the dedicated 65 C coolant loop, such as used in the Prius, and instead rely on the 105 C engine cooling loop. This assessment is important because automotive manufacturers are interested in utilizing the existing water/glycol engine cooling loop to cool the HEV subassemblies in order to eliminate an additional coolant loop with its associated reliability, space, and cost requirements. In addition, the cooling of power electronic devices, traction motors, and generators is critical in meeting the U.S. Department of Energy (DOE) FreedomCAR and Vehicle Technology (FCVT) goals for power rating, volume, weight, efficiency, reliability, and cost. All of these have been addressed in this study. Because there is high interest by the original equipment manufacturers (OEMs) in reducing manufacturing cost to enhance their competitive standing, the approach taken in this analysis was designed to be a positive 'can-do' approach that would be most successful in demonstrating the potential or opportunity of relying entirely on a high-temperature coolant system. Nevertheless, it proved to be clearly evident that a few formidable technical and cost barriers exist and no effective approach for mitigating the barriers was evident in the near term. Based on comprehensive thermal tests of the Prius reported by ORNL in 2005 [1], the continuous ratings at base speed (1200 rpm) with different coolant temperatures were projected from test data at 900 rpm. They are approximately 15 kW with 103 C coolant and 20 kW with 50 C coolant. To avoid this 25% drop1 in continuous power, design changes for improved heat dissipation and carefully managed changes in allowable thermal limits would be required in the hybrid subsystems. This study is designed to identify the technical barriers that potentially exist in moving to a high-temperature cooling loop prior to addressing the actual detailed design. For operation at a significantly higher coolant temperature, there were component-level issues that had to be addressed in this study. These issues generally pertained to the cost and reliability of existing or near-term components that would be suitable for use with the 105 C coolant. The assessed components include power electronic devices/modules such as diodes and insulated-gate bipolar transistors (IGBTs), inverter-grade high-temperature capacitors, permanent magnets (PM), and motor-grade wire insulation. The need for potentially modifying/resizing subassemblies such as inverters, motors, and heat exchangers was also addressed in the study. In order to obtain pertinent information to assist ORNL researchers address the thermal issues at the component, module, subassembly, and system levels, pre-existing laboratory test data conducted at varying temperatures was analyzed in conjunction with information obtained from technical literature searches and industry sources.},
doi = {10.2172/974604},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Sep 01 00:00:00 EDT 2006},
month = {Fri Sep 01 00:00:00 EDT 2006}
}

Technical Report:

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  • This study was performed by the Oak Ridge National Laboratory (ORNL) to identify practical approaches, technical barriers, and cost impacts to achieving high-temperature coolant operation for certain traction drive subassemblies and components of hybrid electric vehicles (HEV). HEVs are unique in their need for the cooling of certain dedicated-traction drive subassemblies/components that include the electric motor(s), generators(s), inverter, dc converter (where applicable), and dc-link capacitors. The new coolant system under study would abandon the dedicated 65 C coolant loop, such as used in the Prius, and instead rely on the 105 C engine cooling loop. This assessment is important becausemore » automotive manufacturers are interested in utilizing the existing water/glycol engine cooling loop to cool the HEV subassemblies in order to eliminate an additional coolant loop with its associated reliability, space, and cost requirements. In addition, the cooling of power electronic devices, traction motors, and generators is critical in meeting the U.S. Department of Energy (DOE) FreedomCAR and Vehicle Technology (FCVT) goals for power rating, volume, weight, efficiency, reliability, and cost. All of these have been addressed in this study. Because there is high interest by the original equipment manufacturers (OEMs) in reducing manufacturing cost to enhance their competitive standing, the approach taken in this analysis was designed to be a positive 'can-do' approach that would be most successful in demonstrating the potential or opportunity of relying entirely on a high-temperature coolant system. Nevertheless, it proved to be clearly evident that a few formidable technical and cost barriers exist and no effective approach for mitigating the barriers was evident in the near term. Based on comprehensive thermal tests of the Prius reported by ORNL in 2005 [1], the continuous ratings at base speed (1200 rpm) with different coolant temperatures were projected from test data at 900 rpm. They are approximately 15 kW with 103 C coolant and 20 kW with 50 C coolant. To avoid this 25% drop1 in continuous power, design changes for improved heat dissipation and carefully managed changes in allowable thermal limits would be required in the hybrid subsystems. This study is designed to identify the technical barriers that potentially exist in moving to a high-temperature cooling loop prior to addressing the actual detailed design. For operation at a significantly higher coolant temperature, there were component-level issues that had to be addressed in this study. These issues generally pertained to the cost and reliability of existing or near term components that would be suitable for use with the 105 C coolant. The assessed components include power electronic devices/modules such as diodes and insulated-gate bipolar transistors (IGBTs), inverter-grade high-temperature capacitors, permanent magnets (PM), and motor-grade wire insulation. The need for potentially modifying/resizing subassemblies such as inverters, motors, and heat exchangers was also addressed in the study. In order to obtain pertinent information to assist ORNL researchers address the thermal issues at the component, module, subassembly, and system levels, pre-existing laboratory test data conducted at varying temperatures was analyzed in conjunction with information obtained from technical literature searches and industry sources.« less
  • This final report details technical accomplishments for Phase I of the ''Low Cost, Compact High Efficiency, Traction Motor for Electric Vehicles/Hybrid Electric Vehicles'' program. The research showed that the segmented-electromagnetic array (SEMA) technology combined with an Integrated Motion Module (IMM) concept is highly suited for electric vehicles. IMMs are essentially mechatronic systems that combine the motor, sensing, power electronics, and control functions for a single axis of motion into a light-weight modular unit. The functional integration of these components makes possible significant reductions in motor/alternator size, weight, and cost, while increasing power density and electromechanical conversion efficiency.
  • A new motor drive, the switched reluctance motor drive, has been developed for hybrid-electric vehicles. The motor drive has been designed, built and tested in the test bed at a near vehicle scale. It has been shown that the switched reluctance motor drive is more suitable for traction application than any other motor drive.