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Mimi Zhang, Sustainable Energy Advantage, LLC
EBC Renewables Committee Meeting
October 16, 2012
Energy Storage: Technology
and Market Overview
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Overview
• Energy Storage Basics
• Technology and Cost
• Implementing Storage
– Renewables
– Markets/Applications
• Challenges/Looking Forward
2
Objective: to provide an overview of energy storage
technologies and applications rather than focus
specifically on storage and renewables
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What is Energy Storage?
• Ability to control energy delivery timing
• Roles: Can be located at transmission, distribution, end-use,
and aggregated (community ES) for a number of applications
• Size range: kW up to MW-scale (this presentation will focus
on utility-scale storage)
• Technologies range from batteries to pumped hydro
Image sources: Beacon Power facility graphic from ecofriend.com; Okinawa pumped hydro from wastedenergy.net
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Energy Storage Definitions
• Power and Energy: Different technologies will be designed to provide
different combinations of power and energy, making them ideal for different
applications
• Cycle Life: Number of times the system can charge/discharge before
replacement. This can vary based on “depth” of discharge (cycling between
50% and 100% wears down less than 0% and 100%)
• Efficiency: Accounts for energy losses between charge and discharge
(energy used for charging/energy discharged)
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Power Energy
Units kW (instantaneous) kWh (amount over time)
Associated Terms Capacity Duration
Depends on: Power Electronics or Turbines Cells or Reservoirs
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Uses of Energy Storage
• Storage can be used for
applications that address
different levels of the grid:
– Generation: time-shifting
and firming of renewables
generation
– Transmission/distribution:
capacity enhancement
deferrals, time-shifting,
reliability, ancillary services
– Commercial/Industrial:
Retail load shifting, backup
power, power quality
– Residential: community
energy storage
• Applications will be explained
in more detail
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Image from Oncor.com: http://www.oncor.com/EN/Pages/Transmission.aspx
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Main ES Technology Types
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Technology Power (kW) Energy (kWh) Applications
Pumped Hydro Hundreds of MW 4+ hrs Time shift, reserve, black start
Compressed Air
(CAES)
~100 MW, (mini
CAES ~10 MW)
4+ hrs Time shift, reserve
Flywheels kW to MW Minutes Frequency regulation, power quality
Batteries (many other types not covered in detail)
Lead Acid
Modular: ~100
kW – MW-scale Hour+
Backup power, time-shift, black
start, capacity deferral
Sodium Sulfur Time-shift, black start, capacity
deferral
Flow Batteries Time-shift, black start, capacity
deferral
Lithium Ion Modular: kW to
MW
Minutes* Frequency regulation, backup
power, time-shift, capacity deferral
Other Technologies: Supercapacitors, temperature-based solutions
* Can be hours by adding cells
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Pumped Hydro
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• Two water reservoirs at different elevations. Water is
pumped to the higher reservoir during off-peak hours,
and released during peak hours.
(Image from Hawaii Electricity Company http://www.heco.com)
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Pumped Hydro (cont.)
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Power/Energy High/High, depends on reservoir and turbine sizes
Sizing Usually very large—hundreds to 1,000+ MW
Cost $1000-2000/kW (very dependent on site, transmission, etc.)1
Efficiency 85%1
Cycle Life 25,0001 (decades+)
Pros Mature technology, straightforward concept
Cons Environmental impact, geographically constrained, requires large
size to be economically viable
History Mature: >127,000 MW installed globally, 21,000 MW in the U.S as of
2009.2
Example Bear Swamp (600 MW in MA owned by Emera)3
Companies Brookfield, Suez, Riverbank
1. Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
2. Oak Ridge National Laboratories. “Pumped Storage Hydropower”. September 20-21, 2010.
3. Emera website (http://www.emera.com/en/home/bearswamp.aspx)
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Compressed Air Energy Storage (CAES)
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Off-peak hours: a
generator forces
air into a
reservoir (usually
underground)
On-peak hours:
compressed air
is released to
help drive
turbines to
produce power
(Image from State Energy Conservation Office of Texas, via Imperial College, London report
(http://www.seco.cpa.state.tx.us/re_wind-reserve.htm)
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CAES (cont.)
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Power/Energy High/High, depends on reservoir and turbine sizes
Sizing Underground CAES usually 100+ MW; new technology targeting smaller
above-ground units ~10 MW
Cost $600-800/kW (large underground CAES), $1000-2000/kW (smaller
above-ground units)1
Efficiency ~70% (not apples to apples comparison because of NG usage)1
Cycle Life 25,0001 (decades)
Pros Mature technology, low cost, long duration
Cons Requires natural gas (30-40% less than NG plant)2,
environmentally/geographically constrained
History Has been around for decades (~1980 unit in Germany, 290 MW). First
and only CAES in US was built in 1991, but other projects are ongoing3
Example McIntosh, AL (110 MW owned by PowerSouth Utility Cooperative and
built by Dresser-Rand)4
Companies Ridge Energy Storage, Dresser-Rand, Energy Storage and Power LLC
1. Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
2. DOE Energy Storage DB (http://www.energystorageexchange.org/projects/136) updated 6/2012
3. Ridge Energy Storage (http://www.ridgeenergystorage.com/caes_history.htm)
4. PowerSouth website (http://www.powersouth.com/mcintosh_power_plant/compressed_air_energy)
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Flywheels
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• Flywheel storage systems
are mechanical/kinetic
batteries that store energy by
spinning.
• Small flywheels systems are
used for power quality
applications (a few seconds
of outage)
• Larger systems can be ~100
kW/flywheel, adding up to
MW+ systems (image to the
right shows Beacon Power’s
2 MW ISO-NE project made
up of 100-kW flywheels)
(Images from Beacon Power http://www.beaconpower.com)
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Flywheels (cont.)
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Power/Energy Low-Medium/Low
Sizing Usually small but modular—can be a few kW (for power quality) or
hundreds of kW to MW (frequency regulation)
Cost $1000-$2000/kW for 15 min duration (grid-scale) 1
Efficiency 95%1
Cycle Life 25,0001 (decades)
Pros Requires less rare or toxic materials than batteries, very high cycle
life that is perfect for frequency regulation
Cons Costly, limited duration
History Utility-scale demos installed in last few years (2009)2, flywheels used
for power quality for decades
Example Beacon Power projects in ISONE and NYISO
Companies Beacon Power (utility-scale), Active Power and Pentadyne (retail
customers)
1. Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
2. Beacon Power
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Lead Acid Batteries
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• Lead Acid batteries have been around for decades (think
car batteries), and are commonly used as backup power
for telecom and data uses. Advanced Lead Acid systems
with carbon-enhanced electrodes greatly increase cycle
life for grid-scale storage.
(Images from Axion Power http://www.axionpower.com)
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Lead Acid Batteries
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Power/Energy Med/Med-high
Sizing kW (backup power) or MW+ (advanced lead acid)
Cost $400/kW, $350/kWh1 ($750/kW for 1 hr, $1800/kW for 4 hrs)
Efficiency 75%1
Cycle Life 2,000-20,0001 (yrs)
Pros Long history, proven technology
Cons Safety concerns, Lead contamination (Xtreme Power’s
Kahuku unit caught on fire in 8/2012)2
History Oldest battery technology (1800s)
Example Xtreme Power’s 15 MW advanced lead acid project at First
Wind’s 30 MW Kahuku Wind Project in Hawaii (March 2011)3
Companies Xtreme Power, East Penn, Axion Power
1. Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
2. Wesoff, Eric. “Battery Room Fire at Kahuku Wind-Energy Storage Farm”. Greentechmedia
(http://www.greentechmedia.com/articles/read/Battery-Room-Fire-at-Kahuku-Wind-Energy-Storage-Farm)
3. First Wind (http://www.firstwind.com/projects/kahuku-wind)
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Sodium Sulfur Batteries
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One of the more common large-scale batteries, with Sulfur
at positive electrode, Sodium at negative electrode, and
beta conductive ceramic separating the two.
(Image from NGK Insulators, Ltd. http://www.ngk.co.jp)
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Sodium Sulfur Batteries (cont.)
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Power/ Energy Med-High/High
Sizing Modular—can be multi-MW
Cost $350/kW and $350/kWh1 (~$700/kW for 1 hr, ~$1750/kW for 4 hrs)
Efficiency 75%1
Cycle Life 3,0001
Pros Track record, long duration, more compact than lead acid batteries
Cons Chemicals may pose safety concerns, limited cycle life. One of
NGK’s TEPCO systems caught on fire on 9/21/20112
History First installed in Tokyo in 1998 (6 MW/8hrs), 200 MW installed
worldwide
Example ERCOT’s “BOB” installed in Presidio, west TX in 2010 (Big-old
Battery, 4 MW for 8 hrs) for reliability applications3
Companies NGK (Japan)
1. Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
2. NGK Insulators, Ltd. http://www.ngk.co.jp
3. NPR. “In Texas, One Really Big Battery”. 4/4/2010 (http://www.npr.org/templates/story/story.php?storyId=125561502)
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Flow Batteries
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Similar to other
batteries, but stores
electro-active chemicals
in external electrolyte
– Often uses an ion
membrane to prevent
mixing
– Hybrid flow batteries (1
electrolyte is stored
separately)
– Certain fuel cells are
flow batteries (H2-Br2)
Image from Nguyen and Savinell. “Flow Batteries”. Electrochemical Society Interface. Fall 2010
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Flow Batteries (cont.)
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Power/Energy Medium/Medium-High
Sizing Varies, can be kW to MW+
Cost ~$400/kW, $400-600/kWh ($800-1000/kW for 1 hr, $2000-
2400/kW for 4 hrs)1
Efficiency 65-85%1
Cycle Life 3,000-5,0001
Pros Lasts longer than NaS and traditional Lead Acid, scalable
Cons New technology, relatively unproven, requires pumps and
other equipment to manage electrolyte flow2
History Very few deployed, usually as demos
Example VRB installed a 250 kW (2 MWh) Vanadium Redox battery for
Pacificorp in Utah (2004)3
Companies Premium Power, ZBB, Prudent Energy (formerly VRB)
1. Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
2 Nguyen and Savinell. “Flow Batteries”. Electrochemical Society Interface. Fall 2010.
3 VRB Presentation to CA Energy Commission 2/2005 (http://www.energy.ca.gov/research/notices/2005-02-
24_workshop/07%20Kuntz-VRB%20PacifiCorp%20Flow%20Battery.pdf)
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More Flow Batteries Examples
21 1. Nguyen and Savinell. “Flow Batteries”. Electrochemical Society Interface. Fall 2010.
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Lithium Ion Batteries
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Lithium Ion batteries have very high energy density and
slow degradation, making it already popular for consumer
electronics and vehicles.
(Image from Greentech Media http://www.greentechmedia.com/articles/read/a123-lands-grid-batteries-in-maui-massachusetts)
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Lithium Ion Batteries (cont.)
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Power/ Energy Med/Low-Med
Sizing Modular—can be multi-MW
Cost $400/kW and $400/kWh1 (~$800/kW for 1 hr, ~$2000/kW for 4 hrs)
Efficiency 85%1
Cycle Life 4,0001
Pros Fast response, high energy density
Cons Higher cost, shorter duration, less likely than lead acid to overheat
History Installed grid-scale as demo projects in the last 5 years, over 100
MW installed to-date worldwide, mostly by A123
Example A123 installed 32 MW/8MWh at AES’s Laurel Mountain Wind Farm
(98 MW in WV) in 9/20112
Companies A123, Altair Nano, Saft
1. Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
2. A123 (http://www.a123systems.com/smart-grid-storage.htm)
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Other ES Technologies
• Other Batteries:
– Nickel Cadmium
– Nickel Metal Hydride
– Magnesium Ion (Pellion)
– Ambri (previously Liquid Metal
Batteries—uses 2 metals and
a salt at high temperatures)
• Supercapacitors
• Electric Vehicles
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Image: European Commission (http://ec.europa.eu/research/energy/eu/research/smartgrid/index_en.htm)
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Storage Technology Comparison
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Minutes
Hours
Day
10 kW 100 kW 1 MW 10 MW 100 MW 1,000 MW
compressed air
batteries
flywheels
capacitors
Pumped hydro
Power/Size
En
erg
y/D
isch
arg
e
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Cost Comparison
• Storage costs cannot be compared on a straight $/kWh
basis due to power and energy factors
26 Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
Frequency Regulation
(15 min)
$/kW 0 1,500 500 1,000
NaS
Lead Acid
Flow Batteries Pumped Hydro
CAES
Flywheels
LiOH Batteries
Time Shift
(1 hr)
$/kW 0 1,500 500 1,000
Time Shift/Deferral/Reserve
(4 hrs)
$/kW 0 2,500 1,000 2,000
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Technology Recap
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Technology Power (kW) Energy (kWh) Efficiency Cycle Life Cost
Pumped Hydro Hundreds of MW High 85% 25,000 $1000-2000/kW
Compressed Air MW+ (though
companies are
exploring small-
scale CAES)
High ~70% 25,000 $600-800/kW (large
underground CAES), $1000-
2000/kW (smaller above-ground
units)1
Flywheels kW to MW Low 95% 25,000 $1000/kW (15 min)
Batteries
Lead Acid Modular: usually
~100 kW – MW-
scale
High
80% 2,000-
20,000
$400/kW, $350/kWh1 ($750/kW
for 1 hr, $1800/kW for 4 hrs)
Sodium Sulfur High 75% 3,000 $350/kW, $350/kWh1 ($700/kW
for 1 hr, $1750/kW for 4 hrs)
Flow Batteries High 65-80% 3,000-
5,000
~$400/kW, $400-600/kWh
($800-1000/kW for 1 hr, $2000-
2400/kW for 4 hrs)1
Lithium Ion Modular, up to
MW+
Low 85% 4,000 $400/kW and $400/kWh1
(~$800/kW for 1 hr, ~$2000/kW
for 4 hrs)
(Many other battery types are not covered in detail)
Other Technologies: supercapacitors, temperature-based solutions
Schoenung, Susan. “Energy Storage Systems Cost Update”. SANDIA National Labs. 4/2011 (SAND2011-2730)
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Energy Storage Applications
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• Table Time Scale Application Description
seconds-
minutes
Frequency
Regulation
Seconds-minute fast response for system
load changes (ancillary service)
Power Quality Seconds-minutes fast response to prevent
outages (end-use)
1 hr+ Renewables Addressing challenges from RE integration
(reliability, time-shift, capacity deferral)
Load Shifting Hour+ shifting for price arbitrage (charge off-
peak, sell on-peak)
Capacity
Deferral
Using storage to bypass or delay expensive
T&D upgrades
Backup Power Hour+ backup power systems (end-use)
Reserves Storage for spinning reserve on a system
(ancillary service)
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Renewables + Energy Storage RE Integration poses a number of challenges that storage can address: time-
shifting, capacity enhancement deferral, reliability, and ancillary services
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Time-shift: store wind at night,
sell during the day; or shift solar
to be peak coincident
Capacity Deferral: certain T&D
upgrades required to integrate
new RE could be deferred with
properly placed ES
Reliability: power quality for solar
project under cloud cover or wind
cut-out (firming). “Firming” RE
could enhance capacity value
Ancillary Services: system-
related reliability needs stemming
from large % of variable
resources—increased demand for
FR, load following, spinning
reserve
Image from Renewable Energy World
(http://www.renewableenergyworld.com/rea/blog/post/2012/03/minnesota-
electricity-could-be-100-renewable-100-local)
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Ancillary Services • Frequency Regulation is the most attractive
market for storage (requires fast response)
– Market size: FR requirements are 0.5-1% of
a system’s peak load (~130 MW in ISONE)
– FR payments fluctuate with energy prices:
ISONE is now $5-10, was ~$30 in 2007-08
– FERC Order 755 requires ISOs to
compensate more for faster response
(October 2011), and ISOs are in the process
of implementing fast FR programs2
• Storage can provide other ancillary
services on a longer timescale (pumped
hydro provides spinning reserve)
• Increased RE penetration increases need
for FR and other ancillary services
• Technologies for FR: flywheels, batteries
(preferably with high cycle life)
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1. ISONE Historic data (http://www.iso-ne.com/markets/)
2. FERC Order 755 (http://www.ferc.gov/whats-new/comm-meet/2011/102011/E-28.pdf) 10/20/2011
Figures: Markov et al. “Incorporating Wind Generation and Load Forecast Uncertainties into Power Grid Operations”.
PNNL-19189 1/2010
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Time-Shift (arbitrage, peak-shifting)
• Value of price arbitrage is not high enough to pay for storage
– In the past week, ISONE’s average daily differential was $17.631 (~$6,500/yr)
– A 1 MW (1hr) storage unit with 85% efficiency would earn ~$5,500/yr, would not
justify $700,000 capital cost
– Costs only work with further incentives
• Technologies: Pumped hydro, CAES, Batteries
32 Image: http://greensmith.us.com/applications/peak-shifting/
1. ISONE Historic data (http://www.iso-ne.com/markets/)
•Storing off-peak/selling on-peak, value comes from price arbitrage and
reducing system peak
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Capacity Enhancement Deferral
• Storage can be used
to bypass or delay
T&D upgrades
– Best for urban
locations with
expensive upgrade
costs
– Limited to “critical
peak” situations that
occur only a few times
a year (peak shaving)
• Technologies:
Batteries, mini CAES
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(Image from NGK Insulators, Ltd. http://www.ngk.co.jp)
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End-User Applications
• Backup Power – Longer duration (4+ hours) to cover an outage
– Technologies:
• Lead Acid batteries have highest market penetration
• LiOH batteries could also perform well
• Power Quality – Seconds-minutes energy to cover power quality events
– Technologies:
• Small flywheels
• Fast response batteries could provide this, but may be oversized
• Retail Load Shifting/Demand Charge Reduction – Similar to time-shift but on a smaller scale
– End-users with spiky loads could get significant cost savings from
decreasing demand charges
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Residential backup
generator (bowa.com)
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Summary of Applications
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Power/Size
En
erg
y/D
isch
arg
e
Minutes
Hours
Day
10 kW 100 kW 1 MW 10 MW 100 MW 1,000 MW
Spinning Reserve
End-use
power
quality
Time-shift (arbitrage and RE
shifting) T&D Upgrade Deferral
Frequency Regulation
Power/Size
En
erg
y/D
isch
arg
e
Renewables
Firming
End-use
backup
power
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Barriers to Widespread Implementation
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• High Cost
– Storage technologies usually don’t pay for themselves under current
market structures
– New technologies are still in R&D phase or have safety concerns
– Costs have been declining and are expected to keep doing so
• Policy/Incentives
– Regulatory barriers have delayed adoption of storage
• ISO rules originally required 1-hr availability for all ancillary services,
including frequency regulation, which precluded flywheels and some LiOH
• FERC Order 755 will result in premiums for fast frequency response,
rewarding energy storage systems
• Asset classification confusion may deter deregulated utilities from trying to
own and operate storage systems
– Storage incentives/policies are difficult to frame because of the wide
variety, applications, and system vs. project uses
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Looking Forward Storage is part of a portfolio of solutions to RE integration as well
as an important part in upgrading our power infrastructure
38
Image from Mark Thiele article (http://www.infowars.com/smart-grid-the-cloud-why-are-they-linked/)
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Sustainable Energy Advantage, LLC
Mimi Zhang
10 Speen Street
Framingham, MA 01701
tel. 508.665.5860
www.seadvantage.com
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