A. Shakouri 9/18/2008
Energy Storage and
Hydrogen Economy
Ali Shakouri
University of California Santa Cruz
Electrical Engineering Department
Edited by Mona Zebarjadi for EE80j, Summer 2009
EE80J-180J; 21 May 2009
Electricity Usage Pattern
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Energy Usage in a typical household
Electricity Usage ~15 kWh/day (54 MJ/day)
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power ~ 625W
Storage:
•Water: 78,717 liter (a cube whose side measures at 4.3 m) at 100
meter (70% conversion efficiency)
•Flywheel: 2138kg, 4m radius, 600rpm (80% conversion efficiency)
•Compressed Air: 3600 liter (0.03 MJ/liter, 50% conversion efficiency)
Hot Water Usage ~25-35MJ
150-200 liter water heated from 15C up to 55C
•Burn 4-5kg of wood in 50% efficient wood stove.
Energy Storage Options
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Compressed air energy storage
• Air is compressed and stored under
ground
– Huntorf, Germany 1978, hold pressures up to
100bar (2kWh/m3)
– Alabama (1991) 70bar energy density
0.54kWh/m3
Battery
• Primary batteries
– Zinc-Carbon
– Alkaline
• Secondary (rechargeable) batteries
– Lead-Acid
– Nickel-Cadmium
– Vanadium
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Battery Characteristics
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• Battery capacity: Amount of charge that it
holds (amp-hours) I x t
• Discharge rate: number of hours over
which the battery discharges
• A battery rated at 100 A·h will deliver 5 A over a 20 hour
period at room temperature. However, if it is instead
discharged at 50 A, it will run out of charge before the 2
hours theoretically.
. Practically, when discharging at low rate, the battery's
energy is delivered more efficiently than at higher
discharge rates
Discharge Characteristics
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Battery Characteristics
Cycle life
• State of charge (SOC): percentage of
storage capacity still available in the
battery
• Battery cycle: cycle of discharge and
recharge from a given SOC down to a
lower state of charge and back to the
original state of charge
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Battery Characteristics
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Figure 1: Cycle life of nickel-metal-hydride
batteries under different operating
conditions. (Zhang, 1998)
NiMH performs best at DC and analog
loads and has lower cycle life with digital a
load.
Figure 2: Cycle life of lithium-ion at varying
discharge levels. (Choi et al., 2002)
Like a mechanical device, the wear-andtear of a battery increases with higher
loads
Lead Acid Battery
www.daviddarling.info
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Battery Discharging
Pb+PbO2+2H2SO4
H2SO4
Pb PbO2
→ 2 PbSO
4
+ 2 H2 O
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Battery Charging
Pb+PbO2+2H2SO4
← 2 PbSO
4
+ 2 H2O
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Vanadium flow Battery
•
Advantages:
–
–
–
–
•
Rechargeable
it can offer almost unlimited capacity simply by
using larger and larger storage tanks,
it can be left completely discharged for long periods
with no ill effects,
it can be recharged simply by replacing the
electrolyte if no power source is available to charge
it, and if the electrolytes are accidentally mixed the
battery suffers no permanent damage.
Disadvantages
–
–
–
a relatively poor energy-to-volume ratio, 87 liter
1kWh (compare to 1liter gasoline which has 9.3kWh)
the system complexity in comparison with standard
storage batteries
Shortage of vanadium supply
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What are Fuel Cells?
Fuel Cells
2H2+ O2 2H2O + electricalpower + heat
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membrane conducts protons from anode to cathode
Membrane
conducts protons from anode to cathode
ProtonExchangeMembrane (PEM)
cathodeproton exchange membrane (PEM)
www.hpower.com
(PEM)
H2 + O2  H2O + electrical energy
Specific Power (W/kg)
Energy Storage Options
Combustion
Engine
Specific Energy (Wh/kg)
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Basic Research Needs
for the Hydrogen Economy
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June 24, 2004
DOE Nano Summit
Washington, D.C.
Presented by:
Mildred Dresselhaus
Massachusetts Institute of Technology
millie@mgm.mit.edu
617-253-6864
Hydrogen: A National Initiative in 2003
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“Tonight
I'm proposing $1.2 billion in research funding
so that America can lead the world in developing
clean, hydrogen-powered automobiles… With a new
national commitment, our scientists and engineers will
overcome obstacles to taking these cars from
laboratory to showroom, so that the first car driven by
a child born today could be powered by hydrogen, and
pollution-free.”
President Bush, State-of the-Union Address,
January 28, 2003
M. S. Dresselhaus, MIT
The Hydrogen Economy
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solar
wind
hydro
H2O
nuclear/solar
thermochemical
cycles
Bio- and
bioinspired
automotive
fuel cells
H2
gas or
hydride
storage
H2
stationary
electricity/heat
generation
fossil fuel
reforming
production
storage
9M tons/yr
4.4 MJ/L (Gas, 10,000 psi)
8.4 MJ/L (Liquid H2)
150 M tons/yr
(light cars and trucks in 2040)
consumer
electronics
9.70 MJ/L
use
in fuel cells
$3000/kW
$30/kW
(Internal Combustion Engine)
(2015 FreedomCAR Target)
M. S. Dresselhaus, MIT
Hydrogen issues
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1 –H2 is not dense even liquid H2 is 10 times less dense than gasoline
H2 vs Gasoline
– 3 x more energy per gram (or per lb)
– 3 x less energy per gallon (or per liter)
2- H2 liquid is dangerous to store; expands by a factor of a thousand if warmed
3-There is virtually no hydrogen gas in the environment
3.1.If we use methane to create H2, we also create Co2
3.2.A Hydrogen production plant would get its power from somewhere else.
Hydrogen is not a source of energy. It is only a means for transporting energy.
4-Hydrogen production (electrolysis) 70% efficient, Best efficiency from a fuel
cell 60%>>Overall 70x60~ 40%
5-It is not yet competitive with the fossil fuel economy in cost, performance, or
reliability
- The most optimistic estimates put the hydrogen economy decades away
Hydrogen Production Panel
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Panel Chairs: Tom Mallouk (Penn State), Laurie Mets (U of Chicago)
Current status:
• Steam-reforming of oil and natural gas produces 9M tons H2/yr
• We will need 150M tons/yr for transportation
• Requires CO2 sequestration.
Alternative sources and technologies:
Coal:
• Cheap, lower H2 yield/C, more contaminants
• Research and Development needed for process development,
gas separations, catalysis, impurity removal.
Solar:
• Widely distributed carbon-neutral; low energy density.
• Photovoltaic/electrolysis current standard – 15% efficient
• Requires 0.3% of land area to serve transportation.
Nuclear: Abundant; carbon-neutral; long development cycle.
M. S. Dresselhaus, MIT
Hydrogen Storage Panel
Panel Chairs: Kathy Taylor (GM, Retired) and Puru Jena (Virginia Commonwealth U)
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Current Technology for automotive applications
• Tanks for gaseous or liquid hydrogen storage.
• Progress demonstrated in solid state storage materials.
System Requirements
• Compact, light-weight, affordable storage.
•No current storage system or material meets all targets.
IDEAL SOLID STATE STORAGE MATERIAL
• High gravimetric and volumetric density
• Fast kinetics
• Favorable thermodynamics
• Reversible and recyclable
• Safe, material integrity
• Cost effective
• Minimal lattice expansion
• Absence of embrittlement
M. S. Dresselhaus, MIT
Priority Research Areas in Hydrogen Storage
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NaAlH4 X-ray view
Metal Hydrides and Complex Hydrides
Degradation, thermophysical properties, effects
of surfaces, processing, dopants, and catalysts in
improving kinetics, nanostructured composites
NaAlD4 neutron view
X ray cross section
H
D
C O
Al
Si
Fe
Neutron cross section
Nanoscale/Novel Materials
Finite size, shape, and curvature effects on
electronic states, thermodynamics, and bonding,
heterogeneous compositions and structures,
catalyzed dissociation and interior storage phase
Neutron Imaging of
Hydrogen
NaBH4 + 2 H2O

4 H2 + NaBO2
Theory and Modeling
Model systems for benchmarking against
calculations at all length scales, integrating
disparate time & length scales, first principles
methods applicable to condensed phases
Cup-Stacked Carbon
Nanofiber
H Adsorption in
Nanotube Array
M. S. Dresselhaus, MIT
Types of Fuel Cells
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Phosphoric Acid FC
(PAFC), 250 kW
United Technologies
Alkaline Fuel Cell
(AFC), Space Shuttle
12 kW
United Technologies
Low-Temp
Proton Exchange
Membrane (PEM)
50 kW, Ballard
High Temp
Solid Oxide FC
(SOFC) 100 kW
SiemensWestinghouse
Molten Carbonate FC
(MCFC) 250 kW
FuelCell Energy,
Fuel Cell Vehicle Learning Demonstration
Project Underway; 3 Years into 5 Year Demo
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• Objectives
– Validate H2 FC Vehicles and Infrastructure in Parallel
– Identify Current Status and Evolution of the Technology
Hydrogen refueling station, Chino, CA
Photo: NREL
Keith Wipke
National Renewable Energy Laboratory
Vehicle Status: All of First Generation Vehicles Deployed,
2nd Generation Initial Introduction in Fall 2007
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On-Board Hydrogen Storage Methods
90
# of Vehicles (All Teams)
80
Liquid H2
10,000 psi tanks
5,000 psi tanks
70
77
60
50
40
30
20
10
2005Q2 2005Q3 2005Q4 2006Q1 2006Q2 2006Q3 2006Q4 2007Q1 2007Q2
Created Aug-28-2007 9:29PM
Keith Wipke
National Renewable Energy Laboratory
Fuel Cells and Novel Fuel Cell Materials Panel
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Panel Chairs: Frank DiSalvo (Cornell), Tom Zawodzinski (Case Western Reserve)
2H2 + O2  2H2O + electrical power + heat
Current status:
Limits to performance are materials, which
have not changed much in 15 years.
Challenges:
Membranes
Operation in lower humidity, more strength,
durability and higher ionic conductivity.
Cathodes
Materials with lower overpotential and resistance to impurities.
Low temperature operation needs cheaper (non- Pt) materials.
Tolerance to impurities: S, hydrocarbons, Cl.
Anodes
Tolerance to impurities: CO, S, Cl.
Cheaper (non or low Pt) catalysts.
Reformers
Need low temperature and inexpensive reformer catalysts.
M. S. Dresselhaus, MIT
Messages
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 Enormous gap between present state-of-the-art capabilities
and requirements that will allow hydrogen to be competitive
with today’s
energy technologies
 production: 9M tons  150M tons (vehicles)
 storage: 4.4 MJ/L (10K psi gas)  9.70 MJ/L
 fuel cells: $3000/kW  $30/kW (gasoline engine)
 Enormous R&D efforts will be required
 Simple improvements of today’s technologies
will not meet requirements
 Technical barriers can be overcome only with high
risk/high payoff basic research
 Research is highly interdisciplinary, requiring chemistry,
materials science, physics, biology, engineering,
nanoscience, computational science
http://www.sc.doe.gov/bes/
hydrogen.pdf
 Basic and applied research should couple seamlessly
M. S. Dresselhaus, MIT
Some Useful References
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Basic Research Needs for the Hydrogen Economy (DOE/BES)
http://www.sc.doe.gov/bes/hydrogen.pdf
Basic Research Needs to Assure a Secure Energy Future (DOE/BES)
http://www.sc.doe.gov/bes/besac/Basic_Research_Needs_To_Assure_A_Secure_Energy_Future_FEB2003.pdf
Powering the Future - Materials Science for the Energy Platforms of the 21st Century: The
Case of Hydrogen (MIT lecture notes)
http://web.mit.edu/mrschapter/www/IAP/iap_2004.html
Hydrogen Programs (DOE/EERE)
http://www.eere.energy.gov/hydrogenandfuelcells/
National Hydrogen Energy Roadmap (DOE/EERE)
http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/national_h2_roadmap.pdf
FreedomCAR Plan (DOE/EERE)
http://www.eere.energy.gov/vehiclesandfuels/
Fuel Cell Overview (Smithsonian Institution)
http://fuelcells.si.edu/basics.htm
The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs
(National Research Council Report, 2004)
http://www.nap.edu/books/0309091632/html/
M. S. Dresselhaus, MIT