PEEM (Power Electronics and Electrical Machine) technology is essential with electric-drive vehicles. PEEM technology comprises three main elements: power electronics (e.g., boost converters and inverters); electric motors; and thermal control and system integration.
Thermal control is a critical element to enable power density, cost, and reliability of the other components. It also is an important component of battery modules. “The plug-in hybrid Chevy Volt, due out in November 2010, will carry 16 kilowatt-hours and go up to 40 miles on a full charge,” reports Matthew Wald for the New York Times. “The battery pack alone would run from $9,600 to $16,000. And that does not count related parts like the system that maintains the temperature of the cells within an acceptable range and manages the charging and discharging.”
So, if companies are to mass produce and warranty electric drive passenger vehicles, they want them to have dependable thermal management. Unfortunately, the ICE (Internal Combustion Engine) paradigm still prevails in design of thermal management systems. Mitch Olszewsk of ORNL (Oak Ridge National Laboratory) warns that OEMs have in their mind that they would like to integrate the “power electronics cooling with the combustion engine cooling system. They’re going off on a pathway of high temperature systems, rather than looking at low temperature systems.”
“ORNL developed a cylindrical design for its inverter, and used a cylindrical capacitor. The power electronics cards (IGBTs and diodes) are mounted inside the center of the cylindrical capacitor, and this whole zone (slightly above the top of the capacitor) is submerged in liquid R134a refrigerant.” For comparison, the ORNL image on the left also shows a 1000 µF capacitor from a baseline Semikron inverter (top), and the SBE 500 µF for the ORNL inverter (bottom).
As reported by Green Car Congress, ORNL researchers have “developed an innovative two-phase “floating loop” cooling system for direct-contact cooling of power electronics and motors.” Even better, their design exceeds “DOE FreedomCAR 2020 targets for power density (13.4 kW/L).”
In a separate post Green Car Congress also reported on development at PNNL (US Department of Energy’s Pacific Northwest National Laboratory) of MOHCs (Metal Organic Heat Carriers). As GCC commentator clett keeps saying, “this is the century of the Organic Rankine Cycle!”
While Oak Ridge researchers envision the benefits to geothermal power production of the rapid expansion and contraction capabilities of MOHCs in a new biphasic fluid, GCC commentators were quick to pick up on other possible applications, e.g., GCC commentator takchess suggests that Raser Technology might be doing similar things.. Raser Technology has expanded into geothermal power as an another application for its advanced power electronics and electrical machines. This blog envisions that MOHCs could be useful not only to PEEM thermal management and even to the range extender in passenger electric vehicles.
GCC Recommended Resources
Curt W. Ayers, James C. Conklin, John S. Hsu, Kirk T. Lowe (2007) A Unique Approach to Power Electronics and Motor Cooling in a Hybrid Electric Vehicle Environment. (IEEE Vehicle Power and Propulsion Conference, 2007)
C.W. Ayers, J.S. Hsu, K.T. Lowe (2006) Fundamentals of a Floating Loop Concept Based on R134a Refrigerant Cooling of High Heat Flux Electronics. (22nd IEEE SEMI-THERM Symposium)
DOE Vehicle Technologies Program Power Electronics and Electric Machines FY 2007 Progress Report
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