2013.10.18 alfred piggott gentherm nrel sae thermoelectric battery thermal management
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Transcript of 2013.10.18 alfred piggott gentherm nrel sae thermoelectric battery thermal management
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Distributed Battery Thermal Management Using ThermoelectricsAuthor(s): Todd Barnhart1, Madhav Karri1, Dmitri Kossakovski1, Alfred Piggott1, Kandler Smith2
Organization: Gentherm Inc.
1 , NREL2
Paper Number: 13TMSS-0006
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Overview
Concept Description
Proposed Packaging
Experiment Summary
Thermal Impact Simulations
Battery Life Calculations
Future Development Testing
BTMS Value
Summary
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Battery Thermal Management via Thermoelectrics
Approach: localized, individually controlled, distributed thermal management of individual cells via direct conductor cooling using thermoelectric devices
* Patent pending
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Thermal Gradients in Working Cells
Cell level thermal gradients:Simulated thermal gradient of discharging cell (Tata Motors, UK)S. Chacko, Y.M. Chung / Journal of Power Sources 213 (2012) 296-303
Pack level thermal gradients:Also: .. a 5 K difference across the pack would result in an approximate 25 % acceleration of the aging kinetics (JCI, EVS24 2009).
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Thermoelectrics Can Compensate for Thermal Gradients
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Advantages of Thermoelectrics
Provide low power active cooling solutions for start/stop or mild/micro-hybrid battery applications.
Air cooled TE solutions can provide a “stand-alone” active cooling system.• “Stand-alone” = No liquid or refrigerant loops required.
Potential enabler to allow under-hood packaging of Li-ion batteries.
Precision independent cell cooling, reducing pack gradient and improving life.
Light weight and compact packaging.
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30 Watt TE Cooling System
• 12 V Li-ion Battery for hybrid electrical system.
• 4 cells - per DIN SPEC 91252 dimensions for prismatic cells.
• 10 Watt TED’s integrated into bus bars.
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Thermoelectric Battery Thermal Management
• BTMS fully integrated with existing BMS (Battery Management System).
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Assembly details
Integrated Battery Management System (BMS) and Thermoelectric Management System (TMS)
Integrated TED and bus bar.
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Modeling of Benefits of Distributed Thermal Management – Gentherm/NREL
StudyApproach:
- Simulate a pack of 50 power cells- Use existing thermal network models- Apply TEDs either to all or selected cells- Use typical drive cycles- Analyze thermal conditions and predict life Lump thermal
network model, excludes 3D FEA of cells/pack
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Simulation Definition
Application: HEVBattery warranty: 10 years, 150k miles Cell: 5 Ah (power cell) Pack: 50 cells Driving:
US06 cycle (48A RMS current, 8.01 miles/cycle,48.4 mph average speed)
41.1 miles/day (150k miles, 10 years) 2 driving trips/day (20.5 min ea.), 8 am and 5 pm
Ambient temperature 28°C (e.g. Phoenix average) Chilled fluid @ 23°C (e.g. via secondary HVAC loop) Or, conditioned air from cabin
Heat transfer: •Cooled surface area: 0.0208 m2/cell •Air ~ 9 W/m2 K •Liquid ~ 85 W/m2 K
Thermal Management Objectives used in Simulation:
• Lumped cooling: Maintain pack average temperature at 25oC
• Distributed cooling: Maintain individual cell temperatures at 25oC
Thermal Management Modes of Operation:
• Nominal cooling: Key-on
• Standby cooling: Key-off, drawing power from either HEV battery (50 Wh limit) or external source such as solar panel
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Lumped cooling: Cell-to-cell T difference
Temperature of cell
vs. cell location
Temperature of cell
vs. cell location
High ambient T
Low ambient T
DT across pack vs. Ambient temp
Distributed cooling is preferred over
lumped
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Battery Life vs. Control Strategy @ Various Cooling Power Levels
Notes: The results are specific to pack model, control algorithm and environmental conditions.
>10 yr life with TE-only (no chilled air or liquid) cooling becomes feasible with ~5 W/cell
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Future Development Testing
Modeling & Test Plan: Evaluate 2 TE based cooling
concepts. Evaluate 2 air cooled solutions for
baseline comparison. Testing to be conducted by NREL. Use simplified 48V micro-hybrid
cycle. Averages 3.5 – 5.0W of heat
generation per cell.
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Development Test Configuration
Electrode Tab TE Cooling
Power Cell
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Charge/Discharge Cycle
Simplified 48V Drive Cycle
Cell Based Cycle
Cycle generates 3.5 – 5.0 Watts of heat per cell, depending on cell temperature.
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Value of Thermal Management
The value equation for BTM systems is still TBD for small pack formats: Life targets are still being established; 4, 6, 8 or
10years?
Replacement cost vs. customer expectations
Life targets will set thresholds for peak operating temperatures.
The BMS will limit battery function to avoid exceeding peak operating temperatures.
BTM systems value will be in enabling wider operating ranges, which allows OEM’s more output (FEI) and life from their battery. TE based BTMS is first being targeted for applications requiring
“Stand-alone” solutions requiring 50-200W of cooling.
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Summary
TE cooling may be well aligned with start/stop or micro-hybrid battery applications. Affordable & flexibility of design options.
TE’s provide light weight, solid-state, scalable & “Stand alone” cooling systems.
Optimized BTM systems add value by allowing OEMs to drive batteries harder and still meeting life targets. (Delivers more FEI)