Energy Storage for
Automotive Applications
26 November 2014
David Greenwood
Professor, Advanced Propulsion Systems
WMG
d.greenwood@warwick.ac.uk
Outline
• Drivers for “electrification” of transport
• Future powertrains types – and their energy storage
requirements
• Charging methods – and their implications for energy storage
• Energy storage as an automotive component
• Conclusions
Outline
• Drivers for “electrification” of transport
• Future powertrains types – and their energy storage
requirements
• Charging methods – and their implications for energy storage
• Energy storage as an automotive component
• Conclusions
There are many drivers for energy efficiency
Energy Security
Source:Cornell University from Edwards 2001
Climate Change &
Air Quality
Energy
Efficient
Transport
$
Source:Adweek
Industrial Opportunity
Consumer demand
Transport accounts for 30% of Energy Use
Road Transport is >75% of that
Most markets now regulate CO2 or fuel economy
Grams CO2 per kilometer, normalised to NEDC
270
US-LDV
California-LDV
Canada-LDV
EU
Japan
China
250
230
EU Requires 3.9%
annual reduction
210
China proposing
aggressive targets
190
170
US requires 4.7%
annual reduction
150
130
US 2025:
China
109
2020: 117
Japan 2020: 105
EU 2020: 95
110
90
2000
Source: ICCT
2005
2010
2015
2020
2025
Gradual global
convergence of
targets
OEM’s must meet fleet-wide targets or be fined
PIV sales increase as more models available
Outline
• Drivers for “electrification” of transport
• Future powertrains types – and their energy storage
requirements
• Charging methods – and their implications for energy storage
• Energy storage as an automotive component
• Conclusions
Broad consensus exists on powertrain roadmap
Hybridisation / Electrification works by:
Stopping engine when idling and
decelerating
Allows engine to be used at more
efficient operating point
4-6% FE benefit NEDC
>10% in city drive
Smaller engines used
With bigger motors
15% FE benefit
Captures braking energy for re-use
later
Allows use of electricity as primary fuel
source in place of hydrocarbons
Store as electricity
Not lost as heat
Zero tailpipe emissions
Lower CO2/km*
(-10%) to 95%
10% FE benefit
* Depending on grid mix
X
Primary functions of the battery system
Conventional
Mild Hybrid
Full Hybrid
Electric
Vehicle
Engine starting (3kW, 2-5Wh)
Ancillary loads (400W average, 4kW peak, ~1kWh)
Absorb regenerated braking energy (per event)
3kW, ~50Wh for micro hybrid
13kW, ~100Wh for mild hybrid
40kW, ~ 1000Wh for HEV, PHEV, FC
Support Acceleration (power and energy as above)
Provide primary energy and power
10kWh – 80kWh
50-300kW
Engine and Motor Requirements – typical pass. car
Engine
Conventional 100kW
Full transient
Mild Hybrid 90-100kW
Full transient
Full Hybrid 60-80kW
Less transient
PHEV 40-60kW
Less transient
REEV 30-50kW
No transient
EV No Engine
Motor
Starter motor
Stop/start
“Battery”
12V
3kW, 1kWh
3-13kW
Torque boost / re-gen
12-48V
5-15kW, 1kWh
20-40kW
Limited EV mode
100-300V
20-40kW, 2kWh
40-60kW
300-600V
Stronger EV mode 40-60kW, 5-20kWh
100kW
Full EV mode
300-600V
100kW, 10-30kWh
100kW
Full EV mode
300-600V
100kW, 20-60kWh
Biggest challenge for commercialization is cost
Battery cost is
the single
largest element
Range drives battery cost – how low can it be ?
100%
93%
Cumulative Journey Count
78%
80%
88%
77%
70%
60%
99%
98%
90%
57%
62%
50%
40%
Total car trips – Cumulative
37%
30%
23%
20%
Total car CO2 – Cumulative
19%
10%
Average Trip Distance (miles)
Source: DfT 2002/2006
0%
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
•
>90% of UK journeys are less than 25 miles (similar in EU and US)
•
Average total daily distance is 24 miles
•
Shorter journeys show greater benefits from electrification
Cost effective range will define products
100%
93%
78%
80%
88%
77%
70%
60%
99%
98%
90%
57%
62%
EV
50%
PHEV
40%
Total car trips – Cumulative
37%
30%
23%
20%
Total car CO2 – Cumulative
19%
10%
Average Trip Distance (miles)
Source: DfT 2002/2006
0%
0
•
5
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
For PHEV, the battery should be large enough for typical daily mileage
•
•
10
As small as possible for cost and packaging => 20-40 miles
For EV, 100 miles (real world) covers 98% of usage
Pack Power (kW)
Power/Energy ratio dictates battery technology
EV P/E will increase
As range becomes more rational
And performance improves
High volume opportunity
In 30-40C packs for
Mild hybrid applications
Pack Capacity (kWh)
Battery challenges differ by powertrain
High C Rates (>20C)
For mild and micro hybrids and high performance cars
Key technical challenges are thermal and impedence
Cost/kW
Cell Level
•
Chemistry and electrode structure suited to high C
•
Internal resistance of cell traded against capacity
•
Thermal conductivity to cell walls/ends important
•
Accurate cell level SoC understanding is critical
Source: McLaren
Source: BMW
Pack level
•
Liquid cooling or forced air cooling required
•
BMS algorithms and sensors must respond to rapid
transients – active balancing sometimes required
Source: Continental
Battery challenges differ by powertrain
Low C Rates (<5C)
For Electric Vehicles
Key technical challenges: energy density & Cost /kWh
Although C rates rising as performance / range increases
Cell Level
•
Capacity more important than rate of reaction
•
Chemistry and electrode structure designed for
durability at high depth of discharge
•
Slower transients allow for simpler cell design and
monitoring
Pack level
•
Air cooling generally sufficient (unless sealed)
•
Simpler BMS due to slower transients.
•
Packaging volume and shape constraints
Battery challenges differ by powertrain
Intermediate C Rates (5C-20C)
For PHEV Vehicles
Key technical challenges are blend of high and
low C rate issues
Cell Level
•
Capacity and rate of reaction both required
•
Opportunity for mixed storage types
•
Need to respond to combination of deep and
shallow cycling
Pack level
•
Liquid or forced air cooling generally required
•
BMS must do both high and low rate operation
•
Possibility to use mixed types of energy store to
serve high and low C requirements
Outline
• Drivers for “electrification” of transport
• Future powertrains types – and their energy storage
requirements
• Charging methods – and their implications for energy storage
• Energy storage as an automotive component
• Conclusions
Smart charging needed for PIV mass market
Without smart charging, 1M vehicles at
12kWh (24km)/day could challenge
peak capacity. Fast charging worse
Same vehicles charged overnight
at lower cost and CO2
Source: demand data from National Grid
Generation capacity adequate with smart charge
>30M vehicles “possible” within
current peak capacity
Source: demand data from National Grid
Role of PIVs in Grid Balancing
•
The UK Market for grid balancing services is worth >£1bn/yr (2013)
•
This will grow with larger power stations and more renewables.
Type
Method
Capacity
Duration
Notice
Total
Total
FREQ
Supply
>3MW
>30 mins
2 seconds
2.5GW
£160M/yr
FAST
Ramp
>25MW/min
>15mins
2 minutes
STOR
Supply
>3MW
>2 hrs
4 hours
£130M/yr
4GW
£90M/yr
•
Aggregated EVs with smart charging / smart meters could deliver this
•
At 3kW, charge interruption alone could saturate balancing
requirements with only 3.5M connected vehicles (10% of UK fleet)
•
Difficult to make business case for V2G or >3kW in high volumes
•
Potential “second life” application for batteries
Source: National Audit Office May 2014
Distribution may be more challenged
Source: BIS
•
High voltage grid is sized for peak
capacity – not challenged by PIVs
•
Local distribution network
(substations, transformers, cables
etc.) typically sized at 1.5kW per
household
•
Draw from EV charging would be 3kW
for slow charging, increasing to
9kW or more for faster charging
•
Households OK - especially newer
housing but PIV neighbourhoods
could overload local substations
•
Linkage of EVs to smart meters is
proposed but no agreed method is yet
implemented
The role of fast charging
•
A gasoline fuel nozzle dispenses at 20MW
equivalent, delivering over 500 miles range in just
a few minutes. We can’t do this electrically.
•
For long journeys (<2% of all journeys made) fast
charging allows range extension to ~80% SoC in
as little as 40 minutes
•
Charging at 50-120kW, ideally located on trunk
routes at service stations.
•
Vehicles require battery cooling and DC charger
•
Regular fast charging would reduce battery life
•
Main problems for use in mass market will be:
– Electrical demand at charger sites
– Incompatibility of OEM systems
– Queues for chargers at busy sites
Alternatives to plug-in charging
Inductive charging
Battery Swap
Static home charging
Most charging done at home/work
• Wire free convenience
Battery swap enables extended range
for circa 5% of charges
• Common standards ?
Smaller footprint than fast charging
Static fast charging
• Fixed route vehicles
• High stop/run ratio
Dynamic charging
• Dedicated charging lane
• Minimised battery size
• Infrastructure cost and power
Allows battery to be managed as a
separate asset to the vehicle
Prefers small number of battery
variants
Outline
• Drivers for “electrification” of transport
• Future powertrains types – and their energy storage
requirements
• Charging methods – and their implications for energy storage
• Energy storage as an automotive component
• Conclusions
Automotive requirements – High Volume
• A typical production car makes 100,000 – 500,000 units/yr
• At 200 cells per pack, this is 3 cells per second or .3s/cell
• At 7000 cells per pack, this is 100 cells per second or .01s/cell
Photograph by Michael Conroy/AP Images
Automotive requirements – High Quality
• The best laptop cells have circa 1 in 200,000 failure /yr
• Laptops have typically 6-12 cells and 3 year life so premature
battery failure affects <0.01%/yr
• Automotive batteries have 200 to 7000 cells/car and 8-10
year life, so higher quality standards are required.
Automotive requirements – Robustness
Hot
50 degrees C
2kW/m2 solar load
Fine dust ingress
Cold
-40 degrees C
Snow packing
Ice formation
Automotive requirements – Robustness
Water
Wading / flooding
Salt and silt ingress
Shock
High frequency vibration
(Belgian Pave)
High amplitude (kerb strike)
Automotive requirements – Safety
Crash
Frontal impact
Side impact (pole)
Rear impact
Fire
Battery damage / malfunction
Involvement in 3rd party
incident
Automotive requirements – Low Cost
Low C Rate Battery Pack Cost Forecasts (€/kWh)
500
450
Overheads
Battery Management
Manufacturing
Materials
Battery Pack Price Including Battery
Management System & Housing/Cooling
€10,000
400
€ /kWh
350
€7,500
300
-21%
CAGR
€6,500
250
€5,500
200

€4,500
150
100
Estimates based
on 20kWh High
Energy pack
(provides ~150
km urban range)
50
Source: Ricardo 2013
0
2010
2015
2020
2025
2030
•
Once “acceptable” EV range (100 miles ?) and life (8-10 years) is
reached, sales volumes in mass market will be driven by vehicle (and
battery) price rather than by additional range
•
<€200/kWh required to give payback vs fuel cost
Life Cycle Emissions
• Batteries have high (net)
embedded CO2
• Materials content
• Manufacturing energy
• At point of sale, EV has
higher CO2 emissions than
gasoline vehicle
• Benefit occurs in-use,
depends on
• Generation mix
• Gasoline miles displaced
• EV as 2nd or 3rd car may
increase overall CO2 unless
Source: UK LowCVP / Ricardo – Preparing for a life cycle CO 2 measure
Outline
• Drivers for “electrification” of transport
• Future powertrains types – and their energy storage
requirements
• Charging methods – and their implications for energy storage
• Energy storage as an automotive component
• Conclusions
In Conclusion
• Automotive battery technology is far from fully mature
• Opportunities exist at every scale
•
Electrode and electrolyte chemistry and structure
•
Cell design and manufacture
•
Pack design and manufacture
•
Battery management
• Tools and knowledge are required to support their delivery
• These are interdisciplinary problems
•
thermal, mechanical, electrochemical and economic interactions
must be simultaneously optimised as part of a powertrain system
• The market needs innovative solutions to allow
electrified powertrains to become truly commonplace.
Don’t forget to read between the lines !
1801
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2014
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Any Questions ?
David Greenwood
Professor, Advanced Propulsion Systems
WMG
d.greenwood@warwick.ac.uk