Energy storage for vehicles: when will they become economically feasible

A/Prof Jeffrey Funk
Division of Engineering and Technology
Management
National University of Singapore
For information on other technologies, see http://www.slideshare.net/Funk98/presentations

Objectives
 What are the important dimensions of
performance for energy storage devices and higher-
level systems?
 What are the rates of improvement?
 What drives these rapid rates of improvement?
 Will these improvements continue?
 What kinds of new higher-level systems will likely
emerge from the improvements in energy storage
devices?
 What does this tell us about the future?

Session Technology
1 Objectives and overview of course
2 Two types of improvements: 1) Creating materials that
better exploit physical phenomena; 2) Geometrical scaling
4 Semiconductors, ICs, electronic systems
5 MEMS and Bio-electronic ICs
6 Nanotechnology and DNA sequencing
7 Superconductivity and solar cells
8 Lighting and Displays (also roll-to roll printing)
9 Human-computer interfaces
10 Telecommunications and Internet
11 Energy Storage, Wind Turbines and 3D Printing
This is Part of the Eleventh Session of MT5009

 Creating materials (and their associated processes)
that better exploit physical phenomenon
 Geometrical scaling
 Increases in scale
 Reductions in scale
 Some technologies directly experience improvements
while others indirectly experience them through
improvements in “components”
As Noted in Previous Session, Two main
mechanisms for improvements
A summary of these ideas can be found in
1) forthcoming paper in California Management Review, What Drives Exponential Improvements?
2) book from Stanford University Press, Technology Change and the Rise of New Industries

 Creating materials (and their associated processes) that
better exploit physical phenomena; finding/creating
materials that
 have higher energy and power storage densities
 are easy to fabricate
 Geometrical scaling
 To what extent will increases in scale of production equipment
lead to lower costs?
 What about nano-scale batteries?
 Some technologies directly experience improvements
while others indirectly experience them through
improvements in “components”
 Better energy storage devices lead to better electric vehicles
 Better power integrated circuits lead to electrification of vehicles
Both are Relevant to Energy Storage for Vehicles

Outline
 Importance of Energy/Power Density
 Energy/Power Storage Density
 Batteries
 Flywheels
 Capacitors
 Electrification of Vehicles
 How can electric vehicles be implemented?
 My vision for the future of transportation

A Key Issue is Energy (and Power) Densities
Why is this
important?
When will
batteries have
similar levels of
energy density
as gasoline?
1 megajoule = 0.28 kwH
MegaJoulesPerLiter
MegaJoules Per Kg

Cognitive Biases
Nobel Laureate Daniel Kahneman
 People assess relative importance of issues, including new
technologies
 by ease of retrieving from memory
 largely determined by extent of coverage in media
 E.g., media talks about solar, wind, battery-powered vehicles, bio-fuels
and thus many think they have rapid rates of improvement - but only
some are
 Second, judgments and decisions are guided directly by
feelings of liking and disliking
 One person invested in Ford because he “liked” their products – but was
Ford stock undervalued?
 Many people “like” some technologies and dislike others without
considering rates of improvement
Source: Daniel Kahneman, Thinking Fast and Slow, 2011
http://edition.cnn.com/2014/03/19/opinion/kohn-flight-370-
obsession/index.html?iid=article_sidebar

High Energy Densities
 Are obviously important for vehicles
 The vehicle must carry the fuel
 The fuel must have a certain level of energy density
before the vehicle can move (what about a solar
helicopter?)
 But also important for all energy technologies
 Higher energy/power density of engines leads to better
fuel efficiency for automobiles, aircraft, ships
 Even for stationary engines, higher energy/power
densities often lead to lower costs per output since costs
are often related to size

Storage type Specific energy (MJ/kg)
Indeterminate matter and antimatter 89,876,000,000 *
Deuterium-tritium fusion 576,000,000
Uranium-235 used in nuclear weapons 88,250,000
Natural uranium (99.3% U-238, 0.7% U-235) in fast breeder reactor 86,000,000
Reactor-grade uranium (3.5% U-235) in light water reactor 3,456,000
30% Pu-238 α-decay 2,200,000
Hf-178m2 isomer 1,326,000
Natural uranium (0.7% U235) in light water reactor 443,000
30% Ta-180m isomer 41,340
Even Higher Energy Densities Exist
Source: http://en.wikipedia.org/wiki/Energy_density
*about 4740 kg of antimatter could have supplied humans with all their energy needs in 2008. for more information
on anti-matter, see Michio Kaku, Physics of the Impossible, New York: Doubleday, 2008

Another way to look at energy density:
This is from the perspective of land
Source: Vaclav Smil

Source: (Koh and Magee, 2008)
Improvements in Power Density of Engines (per weight)

Source: Koh and Magee, 2008
Improvements in Energy Storage Density (per weight)
1 megajoule = 0.28 kwH

Improvements in Energy Storage Density (per volume)

Improvements in Energy Storage (per cost)

Improvements in Energy Storage Density
 Batteries have experienced a very slow rate of improvement
 30 times in 120 years
 Much slower than found with most electronic technologies such as
integrated circuits
 Li-ion batteries have the highest densities per volume and
volume, but not per cost
 Flywheels have a similar level of storage density as batteries
 Capacitors are experiencing a faster rate of improvement than
are flywheels and batteries, but are behind batteries and
flywheels
 Key questions
 Can these rates of improvement be accelerated or even maintained?
 Which one will win?

Source: Tarascon, J. 2009. Batteries for Transportation Now and In the Future,
presented at Energy 2050, Stockholm, Sweden, October 19-20.

Lithium-Ion Batteries
 Rate of improvement is rather slow (5% per year)
 A doubling in 15 years
 Much slower than ICs (doubling every 18-24 months)
 Most recent announcement (271 Wh/kg Li-ion battery in
October 2013) is consistent with rate of improvement
shown in previous slide
 At current rates of improvement, it will take 70 years
before batteries have the same level as gasoline
 Can this rate of improvement be increased or even
maintained?
 By focusing on radical new materials?
 Or materials completely different from lithium-ion?
 Or maybe we should look for a new solution?
http://www.nec.com/en/press/201310/global_20131001_03.html

Radical New Materials Might Enable a Doubling of Energy Density
Source: Nexergy

Source: Tarascon, J , 2010. Key Challenges in future Li-battery research.
Philosophical Transactions of the Royal Society 368: 3227-3241
But this Doubling Might
Take a Long Time

What about Sodium Batteries?
http://phys.org/news/2013-09-sodium-ion-battery-cathode-highest-energy.html
Power Density
Higher densities than for Li-ion batteries
Seoul National University announced 600 Wh/kg in September 2013
But densities quickly decrease with charging and discharging

What About Batteries that Benefit from
Reductions in Scale
 Thin-film ones that benefit from geometric scaling in the same that
solar cells do
 Nano-scale ones
 While conventional batteries separate the two electrodes by thick barrier,
nano-scale batteries place the electrodes close to each other with nano-
wires and other nano-devices
 By reducing the diameter of the electrode or catalyst particles, the ratio of
surface area-to volume goes up and thus the rate of exchange between
particles increases
 Remember the discussion of nano-technology where surface area-
to volume ratio was emphasized
 Some technologies or phenomena benefit from increases in this ratio
Sources: 1) Economist, 2011. The power of the press. January 20, 2011, p. 73; 2) Scientists Reveal Battery Behavior at the Nanoscale,
Science News, September 15, 2010, http://www.sciencedaily.com/releases/2010/09/100914151043.htm. 3) Building Better Batteries from
the Nanoscale Up, Scientific computing, http://www.scientificcomputing. com/news-DS-Building-Better-Batteries-from-the-Nanoscale -Up-
121010.aspx,

What About Costs?
 Lithium-ion batteries are more expensive than lead
acid batteries
 Can the costs of lithium-ion batteries be reduced on a
storage density per cost basis?
 Some argue that the costs will fall as the scale of
production is increased (Lowe, M, Tokuoka, S, Trigg, T, Gereffi, G 2010. Lithium-ion
Batteries for Electric Vehicles, Center on Globalization, Governance & Competitiveness, Duke University,
October 5)
 Although large volumes for portable electronic application,
lithium-ion batteries for cars are different from those for
electronic products
 Also currently have lower production volumes and higher
costs
 Perhaps higher volumes and thus larger scale production
equipment will improve the economics of electric vehicles

http://www.intechopen.com/books/dynamic-modelling/dynamic-modelling-and-control-design-of-advanced-energy-
storage-for-power-system-applications
For Flywheels:
Energy = F(MV2)

http://www.flybridsystems.com/flywheeltech.html

http://physics.technion.ac.il/~rutman/jeremy's%20seminar.html
Flywheels vs. Other Types of Energy Storage
in terms of Power and Energy Densities

Flywheels (1)
 Compared to lithium-ion batteries
 Power Densities are higher for flywheels
 But energy densities are slightly larger for batteries
 Particularly relevant for hybrid vehicles
 twice as much energy is converted during braking than
with batteries
 This is probably why they are used in Formula One Cars
 But can they diffuse to other types of automobiles?
Source: The Economist Technology Quarterly, December 3, 2011

Flywheels (2)
 Rate of improvement is steeper with flywheels than
batteries
 Energy is function of mass times velocity squared for
flywheels, stronger materials (carbon fiber) enable
higher speeds
 What about carbon nanotubes? Their high strength to
weight ratios mean they can spin very fast
 Superconducting bearings, higher voltages from better
power electronics are also source of improvements
 What about cost? ¼ price per storage of batteries?
 One challenge is reliability with required vacuums
Source: The Economist Technology Quarterly, December 3, 2011

Source: Renewable and Sustainable Energy Reviews 11(2007): 235-258
High strength to weight ratios and thus high
energy densities for some rotor materials

Carbon Nanotubes or Graphene
 Carbon nanotubes and/or graphene enable even
higher velocities
 Since CNTs have strength to weight ratios 15 times
higher and graphene has ones 30 times higher than do
carbon fiber (approximately), energy storage densities of
120,000 kJ/kg or 33.6 kWh per kilogram may be possible
with graphene
 This energy density is about 15-30 times higher than is
currently available from lithium-ion batteries
Source: Presentation by my students on April 11, 2013.
Slides can be found on http://www.slideshare.net/Funk98/presentations

Capacitors
 Much lower energy densities than for batteries, but
higher power densities (but not as high as
flywheels)
 Energy density is a function of
 Capacitance
 Voltage squared
 Improvement efforts focus on new materials
(mostly carbon now) such as
 Double layer carbon capacitors
 Pseudo capacitors (many exotic variables)
 Hybrid (asymetric) capacitors

Source: Naoi K and Simon P, 2008, New Materials and New Configurations for Advanced Electrochemical
Capacitors; The Electrochemical Society Interface, Spring 17(1): 34-37.

http://www.extremetech.com/extreme/122763-graphene-supercapacitors-are-20-times-as-powerful-can-
be-made-with-a-dvd-burner

But Most Commercialized Ultracapacitors are Made from Carbon
which have lower energy densities than other materials
Source: Andrew Burke, Proceedings of the IEEE 95(4): 806-820, 2007.

High Surface to Volume Ratios
 Are important for many things (remember the
session on nanotechnology)
 They are also relevant for capacitors
 Ruthenium-based capacitors also use thin sheets to
achieve higher surface-to volume ratios
 Carbon nanotubes have high surface to volume
ratios and thus high capacitance

Electrification of Vehicles (1)
 It’s not just the addition of an energy storage
devices; electrical controls are replacing
mechanical controls for
 water and oil pumps, radiator cooling fans
 steering systems, brakes, throttles, shock absorbers
 The next great step, which has already occurred in
locomotives, large trucks, and aircraft
 Electric drive trains will replace the
gearbox, driveshaft, differential
 They have higher power densities and are more reliable
than drives that rely on shafts, gears, belts, and hydraulic
fluids

More general source: Peter Huber, Mark Mills, 2006, The Bottomless Well:
The Twilight of Fuel, the Virtue of Waste, and Why We Will Never Run Out of Energy

http://cesa-automotive-electronics.blogspot.sg/2012/09/dual-voltage-power-supply-system-with.html

Electrification of Vehicles (2)
 Part of the trend towards electrical controls are
being driven by improvements in semiconductors
 Electrical controls use semiconductors
 Power semiconductors experience improvements each
year as do integrated circuits (ICs)
 but not to the extent of microprocessors and memory
 Electrical controls reduces cost and weight of
vehicle
 The latter also reduces the necessary energy storage
capacity of the batteries, flywheels, or capacitors
Sources: http://www.manhattan-institute.org/html/eper_07.htm and The Bottomless Well: The Twilight of Fuel, the
Virtue of Waste, and Why We Will Never Run Out of Energy, Peter Huber and Mark P. Mills

IGBT: Insulated-gate bipolar transistor
GTO: Gate turn off thyristor

Source: http://www.embedded.com/design/components-and-packaging/4371098/New-power-semiconductor-technologies-
challenge-assembly-and-system-setups
Reductions in Voltages (and thus Resistances) for same Current (and thus area
and cost) for IGBTs (Insulated Gate Bipolar Transistor)

Source: http://www.embedded.com/design/components-and-packaging/4371098/New-power-semiconductor-technologies-
challenge-assembly-and-system-setups
Reductions in Resistance and thus Area (and costs) for MOSFETS

What can we Conclude about Electrification
of Vehicles?
 It is going to happen very soon
 Much faster than doubling of energy storage densities
 Electrification will reduce weight of vehicle and thus
necessary size of the energy storage
 It also facilitates vehicles working with smart grid
 Smart grids are being rapidly implemented
 Electrical grid is being combined with the Internet
 What other automotive technology will likely be
deployed before energy storage densities are doubled?
 What are the implications for electric vehicles and
energy usage by vehicles in general?

Many Ways to Do This
 1) Electric vehicle with same range and acceleration as
gasoline engines
 Low energy and power storage densities of
batteries, capacitors, and flywheels make this difficult to
achieve
 2) Use both gasoline and electric storage, i.e., hybrid
 Very expensive to include both
 Most users choose vehicles based on price
 3) All electric but with low capacity electric storage
and many fast/rapid charging stations
 Use flywheels since they have high power densities?
 Use high voltages for rapid charging?
 Use wireless charging?

Many Fast Charging Stations
 Utilities sell high voltage electricity to parking garages,
other parking places, and other companies that provide
users with rapid charging
 Cars can also be charged wirelessly (getting cheaper
through advances in power electronics)
 GPS enables cars to know where they are going, when
they will arrive and thus how to find and reserve a
charger
 Falling weight of vehicles, driven by replacement of
mechanical with electric controls, also facilitates move
towards low capacity electric storage in vehicles
 Eventually charging may be done when vehicles are
stopped at traffic lights, or moving on highways
Source: http://www.manhattan-institute.org/html/eper_07.htm

 Cost of charging station?
 Rate of charging?
 How much more expensive for fast
charging?
 Is wireless cheaper or faster?
Performance and Cost of Charging Stations

Can Higher Efficiencies be Achieved in Wireless Charging?
Can we
charge
vehicles while
they move?
Source: Wireless Charging for Smartphone, MT5009 group presentation

My Vision of the Future
 Most people will live in cities
 Public transportation becomes better through better
information
 GPS and thus accurate locations for buses
 Smart phones (improved interface) for better info on buses, MRT
 Less breakdowns through better sensors
 Highways and roads dedicated to autonomous vehicles (falling
cost of lasers, ICs)
 Most autonomous vehicles will be rented via smart phones
 Most rented vehicles will be small (single person) and light
(electrification)
 Most vehicles will be electric with frequent charging at rapid
charging stations
 Wireless charging on roads and highways?
 Superconducting cables for highways?

Conclusions, Relevant Questions for Group Projects
 Energy and power storage densities are important
 Energy storage densities of batteries, flywheels and
capacitors are much lower than for gasoline
 Rates of improvements are also fairly slow
 Can these rates of improvements be accelerated?
 Are their radical new materials that will enable much
higher energy and power densities?
 How can we find these materials?
 Maybe we should admit that improvements won’t be
made and devise new types of vehicular systems

Conclusions, Relevant Questions……(2)
 Many more choices for energy storage than are
ordinarily presented
 Even these slides don’t consider all the possible choices
 But focusing on rates of improvement gives us better
information than do current methods
 Media focuses on hybrid vehicles, when it should be
focusing on the
 low storage densities of these batteries
 slow rates of improvement
 other choices, of which there are many

IGBT: insulated gate bipolar transistor; MCU: microprocessor control unit
Vehicle electrification drive trends in power semiconductors,
Kevin Anderson, July 12, 2011, Freescale
Are the improvements in these devices sufficient?

FET: field-effect transistor; WBG: wide-band gap semiconductor such as SiC
Vehicle electrification drive trends in power
semiconductors, Kevin Anderson, July 12, 2011, Freescale
Maybe Wide Band Gap Semiconductors can enable the
necessary improvements?

http://www.semicon.toshiba.co.jp/eng/product/transistor/mos/hvmos.html
9.2%/year
Lower Resistance Leads to Smaller and Cheaper Power Electronics

http://www.eetimes.com/document.asp?doc_id=1272514
New Materials Have Even Lower Resistance
(and higher breakdown voltages)

http://iopscience.iop.org/0268-1242/28/7/074012/article#fnref-sst455286bib22

http://electronicdesign.com/power/improved-power-ics-give-
supply-designers-more-bang-buck

Daniel Kahneman, Thinking Fast
and Slow
 An individual has been described by a neighbor as
follows: “Steve is very shy and withdrawn, invariably
helpful but with little interest in people or in the world
of reality. A meek and tidy soul, he has a need for order
and structure and a passion for detail.” Is Steve more
likely to be a librarian or a farmer?

Daniel Kahneman
 Many years ago I visited the chief investment officer of
a large financial firm, who told me that he had just
invested some tens of millions of dollars in the stock of
Ford Motor Company. When I asked how he had made
that decision, he replied that the had recently
attended an automobile show and had been
impressed. “Boy, do they know how to make a car!” was
his explanation. He made it very clear that he trusted
his gut feeling and was satisfied with himself and with
his decision.

Researchers at Rice University have come up with a new way to boost the efficiency of the ubiquitous lithium ion (LI) battery by
employing ribbons of graphene that start as carbon nanotubes.
Proof-of-concept anodes — the part of the battery that stores lithium ions — built with graphene nanoribbons (GNRs) and tin oxide
showed an initial capacity better than the theoretical capacity of tin oxide alone, according to Rice chemist James Tour. After 50
charge-discharge cycles, the test units retained a capacity that was still more than double that of the graphite currently used for LI
battery anodes.
In the new experiments, the Rice lab mixed graphene nanoribbons and tin oxide particles about 10 nanometers wide in a slurry with
a cellulose gum binder and a bit of water, spread it on a current collector and encased it in a button-style battery. GNRs are a single
atom thick and thousands of times longer than they are wide. The GNRs not only separate and support the tin oxide but also help
deliver lithium ions to the nanoparticles.
Lab tests showed initial charge capacities of more than 1,520 milliamp hours per gram (mAh/g). Over repeated charge-discharge cycles,
the material settled into a solid 825 mAh/g. “It took about two months to go through 50 cycles,” said lead author Jian Lin, a postdoctoral
researcher at Rice, who believes it could handle many more without losing significant capacity.
GNRs could also help overcome a prime difficulty with LI battery development. Lithium ions tend to expand the material they inhabit,
and the material contracts when they’re pulled away. Over time, materials like silicon, which shows extraordinary capacity for lithium,
break down and lose their ability to store ions.
http://nextbigfuture.com/search?updated-max=2013-06-14T16:50:00-07:00&max-results=7&start=70&by-date=false
How About Graphene Based Batteries?

Recently developed capacitor had
energy density of 16Wh/kg (100 times less than Li)
power density of 10 kW/kg (as high as flywheels)
40-Farads and maximum voltage of 3.5 V
On basis of accelerated tests, a 16-year lifetime was forecast
But too expensive!
Source: carbon nanotubes: present and future commercial applications, Michael
De Volder et al, Science 339(535): 535-539
To what extent can further improvements be made?
Carbon NanoTubes for Capacitors

Monash researchers have developed a completely new strategy to engineer graphene-based supercapacitors (SC)
with the energy density of lead batteries, making them viable for widespread use in renewable energy storage,
portable electronics and electric vehicles. The energy density of 60 Watt-hours per litre - comparable to lead-acid
batteries and around 12 times higher than commercially available SCs.
Science - Liquid-Mediated Dense Integration of Graphene Materials for Compact Capacitive Energy Storage
Porous yet densely packed carbon electrodes with high ion-accessible surface area and low ion transport resistance
are crucial to the realization of high-density electrochemical capacitive energy storage but have proved to be very
challenging to produce. Taking advantage of chemically converted graphene’s intrinsic microcorrugated two-dimensional
configuration and self-assembly behavior, we show that such materials can be readily formed by capillary compression
of adaptive graphene gel films in the presence of a nonvolatile liquid electrolyte. This simple soft approach enables
subnanometer scale integration of graphene sheets with electrolytes to form highly compact carbon electrodes with a
continuous ion transport network. Electrochemical capacitors based on the resulting films can obtain volumetric energy
densities approaching 60 watt-hours per liter.
http://nextbigfuture.com/2013_07_28_archive.html

http://www.cpes.vt.edu/public/nugget/2013_D1.7.php

http://www.eetimes.com/document.asp?doc_id=1272514

http://www.i-micronews.com/reports/Power-GaN-2012/3/170/

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