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Energy Storage as a Key Element in Smart Grids
Ross Baldick, Department of Electrical and
Computer Engineering
1Copyright © 2017
Bill Muston
Oncor
Spring 2017Final #2 Version
Outline
Why Now? Cost trend for energy storage
Energy Storage System (ESS) Definition
Roles – Bulk power, wires, customer and DER
Utility distribution systems & ESS
Power, energy, reactive
Delivery asset alternative, reliability, microgrid
Multiple uses of a single ESS
Regulatory & market construct considerations
2Copyright © 2017
Acknowledgements
Thanks to Oncor for allowing the use of slides and knowledge
Thanks to Nathan Kassees and Mila Hunt at Oncor for partnership is developing slides, content, and homework assignment
Copyright © 2017 3
ONCOR AT A GLANCE
Texas' largest regulated transmission and
distribution utility
Serves over 3.3 M customers/meters
402 Cities and 91 counties
3,784 Employees
REGULATE
D
TRANSMISSION
DISTRIBUTION
METERING
COMPETITIVECOMPETITIVE
GENERATIONRETAIL
ELECTRIC
PROVIDERS
Outline
Why Now? Cost trend for energy storage
Energy Storage System (ESS) Definition
Roles – Bulk power, wires, customer-sited and DER
Utility distribution systems & ESS
Power, energy, reactive
Delivery asset alternative, reliability, microgrid
Multiple uses of a single ESS
Regulatory & market construct considerations
5Copyright © 2017
WHY NOW?
• Energy storage – to complement grid functions at
substations and in distribution systems – has never been
utilized widely
• Traditional equipment is economical and works well
• High cost of storage for proven types of storage
• Technical maturity of many newer storage technologies is not yet
proven, predictable, and reliable, as compared to traditional utility
equipment
• Commercial maturity – standardized performance needs for
distribution applications have not been established, and, therefore,
standardized products have not been widely available with
standard warranty for standard performance expectations
• BUT –
• Costs and maturity are changing rapidly
• Standardization thru common application types and functional
specifications is underway6
7GTM Research Storage Cost Outlook
Grid-Scale Storage Project Cost Forecast – Medium Duration (2-hour)
System Costs ($ per kWh) 2015 2016E 2017E 2018E 2019E 2020E
BOS $335 $299 $269 $241 $217 $195
Li-ion Battery $330 $304 $279 $257 $236 $217
Total $665 $603 $548 $498 $453 $412
Li-ionBattery
$330 $304 $279 $257 $236 $217
BOS $335
$299$269
$241$217
$195
$0
$100
$200
$300
$400
$500
$600
$700
legend 2015 2016E 2017E 2018E 2019E 2020E
Sto
rage S
yste
m C
ost
($/k
Wh)
Source: GTM ‘Grid-Scale Energy Storage Balance of Systems 2015-2020: Architectures, Costs and Players’
Used with Permission of GTM
Lithium-Ion Battery
Oncor Confidential - For Internal Use Only8
Anode - Copper conductor in Carbon, Titanium-
Oxide, or Silicon-Tin structure
1 - Lithium Ions release electrons and dissolve into
electrolyte
4 - Lithium Ions combine with electrons and layer
onto anode
Cathode - Lithium-Metal-Oxide or Lithium-Metal-
Phosphate structure
2 - Lithium Ions combine with electrons and
integrate with cathode
3 - Lithium Ions release electrons and dissolve into
electrolyte
ElectrolyteLiquid or Gel electrolyte of Lithium-Carbonate or
Lithium-Flouride Compound
Conductive to Lithium Ions (Li+)
Polymer Hydrocarbon barrier conductive to Lithium Ions
(Li+)
Outline
Why Now? Cost trend for energy storage
Energy Storage System (ESS) Definition
Roles – Bulk power, wires, customer-sited and DER
Utility distribution systems & ESS
Power, energy, reactive
Delivery asset alternative, reliability, microgrid
Multiple uses of a single ESS
Regulatory & market construct considerations
9Copyright © 2017
ENERGY STORAGE SYSTEM – ‘ESS’
• Energy stored in a form other than AC electricity
• The energy storage unit is ‘filled’ with energy from the
grid
• Conversion from AC to stored energy and back to AC
• Grid interface equipment and controls
• Energy storage unit internal controls to protect the asset
• Often called Battery Management System (BMS)
• A set of equipment that can be ‘placed’
• As used in these slide, an ESS is NOT pumped hydro or compressed air
energy storage where siting is driven by geography
10
BATTERY STORAGE SYSTEMS
11
Battery cell
Inverter
Grid
Electric Customer
BMS Controls
ESS Controls
Battery rack
Battery Array
Switch
Transformer
12
Source: DOE’s Sandia National Laboratory, Energy Storage Systems Program –
http://www.sandia.gov/ess/wp-content/uploads/2015/04/EsPositioningHandbook.png
http://www.sandia.gov/ess/publication/doeepri-electricity-storage-handbook/
Outline
Why Now? Cost trend for energy storage
Energy Storage System (ESS) Definition
Roles – Overview – Bulk power, wires, customer-sited and DER
Utility distribution systems & ESS
Power, energy, reactive
Delivery asset alternative, reliability, microgrid
Multiple uses of a single ESS
Regulatory & market construct considerations
13Copyright © 2017
BATTERY
TRANSMISSIONGENERATION
RETAIL ELECTRIC
PROVIDERS
DISTRIBUTION LINES
CompetitiveRegulated
GRID ENERGY STORAGE VALUES
15
BULK GRID
Wind & solar firming, smoothing and dispatch
Time-shift energy supply vs. need (eg. wind & solar) to meet market needs and/or energy arbitrage
Grid reliability services
• Supply regulation
• Frequency regulation
• Responsive reserves for grid contingency
• Fast response
DISTRIBUTION FEEDERS &
SUBSTATION
Support the local grid during upstream outages
Defer or substitute for traditional upgrades needed to support growing loads
Integrate distributed renewable sources (DERs) to the local grid to maintain grid stability & voltage control
CUSTOMER
Manage peak demand on the grid to limit demand charges
Smooth & firm customer-sited solar or wind
Time-shift energy from the grid or from customer-sited solar, such as to manage energy use under a time-of-use retail rate
Support islanded microgrid operation for critical services during grid outage
Focus of this lecture
ENERGY STORAGE USE CASES
16
• Various studies, projects, and organizations have
developed use cases for energy storage applications
• These use cases are generally high-level descriptions
and ESS performance expectations
• The following 2 slides show use cases from a very
recent study, the Lazard Levelized Cost of Storage v2.0
17
18
For further information on applications, cost, and
performance –
• See the Lazard Levelized Cost of Storage v2.0 –
• Examines the lifetime ownership cost for energy storage in a
variety of applications and of a variety of types of energy storage –
https://www.lazard.com/perspective/levelized-cost-of-storage-
analysis-20/
• See the DOE/EPRI Electricity Energy Storage Handbook
in Collaboration with NRECA 2013 version
• http://www.sandia.gov/ess/publication/doeepri-electricity-storage-
handbook/ (Update anticipated in 2017 does not appear to be
available at this point in time.)
19
http://www.nytimes.com/2010/11/07/us/07ttbattery.html
Electric Transmission Texas energy
storage project in Presidio, Texas.
• Commercial operation in 2010
• Serving transmission purposes
• http://www.ettexas.com/projects/presnas.asp
Slide compiled by Oncor from public sources
21
22 Slide compiled by Oncor from public sources
Outline
Why Now? Cost trend for energy storage
Energy Storage System (ESS) Definition
Roles – Bulk power, wires, customer-sited and DER
Utility distribution systems & ESS
Power, energy, reactive
Delivery asset alternative, reliability, microgrid
Multiple uses of a single ESS
Regulatory & market construct considerations
24Copyright © 2017
DISTRIBUTION SYSTEM USE CASES FOR ESS
• ASSET ALTERNATIVE – An asset to meet a portion of
growing local peak demand without requiring that
traditional upstream facilities be upgraded to meet that
demand
• RELIABILITY – Supply local downstream loads when the
upstream power is out
• INTEGRATE SOLAR – Maintain required feeder voltage &
power factor during rapid feeder power changes for
feeders with high solar penetration when clouds come
and go
25
ASSET ALTERNATIVE – Substation
• Meet the incremental peak demand on a substation
• When that incremental demand would create total substation
demand that is greater than what the substation equipment can
support
• Case 1 – The peak demand on substation equipment is
growing slowly
• A major substation upgrade or expansion is the primary or
traditional approach
• The cost of the upgrade would be high
• Case 2 – The peak demand on substation equipment is
expected to grow very rapidly
• The time required to implement traditional upgrades is longer than
the expected timing of the increased peak demand
• The cost required to quickly implement traditional upgrades in the
short timeframe would be prohibitive
26
ASSET ALTERNATIVE – Distribution Feeder
• Meet the local demand growth downstream on a feeder
• The demand growth will otherwise require that a portion
of the feeder that is upstream of the demand growth
would need to be upgraded
• The cost or lead time or community impact might be
limiting factors in upgrading the feeder
• Siting is available for a storage facility
29
RELIABILITY – At transformer serving customers
• Supply downstream loads with ESS when the upstream
power is out
• Goal: reduce total annual outage time as measured by SAIDI for
the affected portion of feeder
• Reduce outage times by utilizing storage for localized
supply while utility crews are correcting the outage and
restoring normal service
• Storage as the sole energy resource for the islanded segment of
the feeder
• Storage provides a less costly means to improve SAIDI than
traditional means
30
31
Purpose
• Evaluate effectiveness of deploying small-scale battery storage to bridge outages and improve local power quality
Details
• Six 25 kW lithium ion batteries
• Installation, testing and monitoring
Capacity
• These batteries are capable of bridging outages up to a few hours of duration
NEIGHBORHOOD STORAGE RELIABILITY INITIATIVE
NEIGHBORHOOD STORAGE RELIABILITY INITIATIVE
Distribution level outage backup, voltage regulation
25 kW, 25 kWh
Installed at single phase 120/240 secondary
1 at an Oncor facility
5 on Oncor System
Supports residential homes during outages and maintains
voltage within mandated levels (114 – 126 V)
32
Oncor Initial Installation at Oncor Facility Neighborhood in South Dallas
NEIGHBORHOOD STORAGE RELIABILITY INITIATIVE
Goals:
• Demonstrate the use of energy storage technology to improve
reliability
• Outage backup
• Voltage regulation
• Gather performance data to identify value of technology on system
• Efficiency
• Customer feedback
33
Example: Outage
34
ESS
Tie
Breaker
Example: Outage
35
ESS
Tie
Breaker
Example: Outage
36
ESS
Tie
Breaker
Normal Switching Scheme
37
CES = Community Energy Storage
Bypass Switching Scheme
38
CES = Community Energy Storage
NEIGHBORHOOD STORAGE RELIABILITY INITIATIVE
Location Selection
120/240 Single Phase
Test Installation (SOSF)
South Dallas Target Area
High SAIDI Feeders
Customer Verbal Approval
Available Space
39
SAIDI = System Average Interruption Duration Index
NSRI Testing
Inverter overload capability
40
0
20
40
60
80
100
120
140
160
180
200
0
5
10
15
20
25
30
28.7 32.7 37.2 41.9
Cu
rre
nt
(A)
Tim
e (s
)
Load (kW)
Inverter Overload
Time to Inverter Overload
RMS current
NSRI Testing
Open circuit island test
Oncor Confidential - For Internal Use Only41 Oncor Confidential - For Internal Use Only41
25.5 ms
Transition to
Inverter
Transition to
Grid
34.4 ms
NSRI Testing
25 kW Load Island Test
42
Transition to
Inverter
Transition to
Grid
26.7 ms
33.0 ms
NSRI Testing
Small Fridge Island Test (2 amp motor)
Oncor Confidential - For Internal Use Only43
26.0 ms
Transition to
Inverter
Large A/C Load Island Test
44
1 second later
Operational Settings
Based on ITI (CBEMA)
curve defining voltage
tolerance thresholds of
power supplies
NSRI islanding settings
based on this curve
45
Results
46
LocationNumber of Operations
Total Island Minutes Average Efficiency
1 7 872 125 95.41%
2 3 267 89 98.10%
3 5 453 91 97.49%
4 8 361 45 96.82%
5 3 231 77 97.53%
All 26 2184 84
Efficiency measured as energy in vs.
energy out over the life of the system
RELIABILITY – SEGMENT OF A FEEDER
• Storage as sole energy resource
• Sized based on specific statistics of outage and restoration times for that
local area
• Location of ESS unit based on feeder and load topology
• Adds technical requirements to ESS
• Provide magnetizing in-rush current to transformers and motor
start
• Supply fault current to fuses to clear smaller, typically single phase,
faults and return to operation
• Add distribution automation for sectionalizing for the
original fault location, fault isolation, sectionalizing, and
reconfiguration (FLISR)
47
RURAL FEEDER RELIABILITY PROJECT STUDY
Can an energy storage system (ESS) on a long, rural
distribution feeder improve the reliability of that feeder?
Can it support small towns at the end of long overhead
lines?
• These towns are vulnerable to extended outages
Reliability measured by SAIDI
ESS located downstream on the feeder
• At or near the small towns affected by outages
48
49 Oncor Proprietary and Confidential - Not for external distribution
Approaches Used Today to Improve Feeder Reliability
• Vegetation Management
• Feeder Maintenance
• Automation –
• Fault Location, Isolation, Service Restoration/Reconfiguration
• Distribution automation switching devices
• Autonomous communications and control
https://www.smartgrid.gov/files/B5_draft_rep
ort-12-18-2014.pdf
Fault Location, Isolation, and Service Restoration (FLISR)
An essential component for
successful FLISR operations is the
communications network for
remote monitoring and control of
technologies and systems. FLISR
communication networks require
increased resilience because they
must operate under conditions
where the grid itself is damaged or
not functioning properly. The two-
way communications network must
have sufficient coverage and
capacity to interface and
interoperate with a wide variety of
technologies and systems,
including various field devices and
DMS, OMS, and SCADA systems.
From U.S. Department of Energy report
Fault Location, Isolation, and Service
Restoration Technologies Reduce Outage
Impact and Duration
Long Rural Feeder
Traditional FLISR, non-ESS approach
Switches
New line
Existing line
Substation
Switches
Substation
52
Using Energy Storage to Improve Feeder Reliability
• Energy Storage System (ESS)
• Automation –
• Fault Location, Isolation, Service Restoration/Reconfiguration
• Distribution automation switching devices
• Autonomous communications and control
Long Rural Feeder
A battery that serves downstream customers when the upstream grid is
out
Transmission lines
Pockets
of load
Additional
pockets of load
Substation
GEOGRAPHIC REGION FOR THIS PROJECT
54
Area of interest is in
blue oval
Characteristics of the
area
• Agriculture
• Forestry
• Sparse population
FEEDER SELECTION CRITERIA
1. Consistently high SAIDI
2. Majority of faults along feeder backbone
3. Ties to other feeders not easily accessible
4. Minimum of a few hundred customers
5. No heavy industrial customers
6. Feeder length >40 miles primary 3-phase
7. Pockets of load located toward the end of the line
55
SAIDI = System Average Interruption Duration Index
Feeder B
56
73 Miles of Primary Feeder
379 Customers
4.3 kW of load/meter avg
2.3 MW of peak load
Feeder B Battery Solution
57
c
c
Automated
Switches
S
S
S
2 mi
Install N/O IRPC with Intelliteam II.
Install N/C IRPC with Intelliteam II.
R
Install N/CNova Form 6 Recloser
R
Honey Grove Substation
29,000 ft. of 3-#2 ACSR reconductor/rebuild
R
Install N/C IRPC with Intelliteam II.
Install/Upgrade regulators/controls [3 locations]
Install N/O IRPC with Intelliteam II.
31,000 ft. of 3-#2 ACSR reconductor/rebuild
8,000 ft. of 3-#2ACSR reconductor/rebuild
R
Install N/CNova Form 6 Recloser
N
Feeder B Alternative Solution
RURAL FEEDER – Lessons Learned
• Feeder in-rush current on blackstart via ESS imposes
additional specification and design needs, in order to
procure an ESS today for this specific application
• System protection requires adequate fault current from an
ESS to blow fuses on feeder lateral lines. This also
imposes additional specification and design needs, in order
to procure an ESS for this specific application
• Suggests to vendors of ESS a need to develop standard
options for ESS that incorporate in-rush current and fault
current needs
59
INTEGRATE SOLAR ON A DISTRIBUTION FEEDER
• Utility need: Maintain required feeder voltage & power
factor during rapid feeder power changes – when clouds
come and go for feeders with high penetration of solar PV
systems
• Utilize ESS to complement to deployed voltage & power
factor control, such as load tap changers (LTC), capacitor
banks, and voltage regulators, all of which were not
designed for frequent operation
• Utilize energy, power, and reactive capabilities of the ESS
• Frequent use of LTC’s, capacitor banks and voltage regulators will
wear them out, requiring higher maintenance
• Inverter is utilized for feeder voltage & reactive power management
• ESS main capability is utilized for other purposes
60
Outline
Why Now? Cost trend for energy storage
Energy Storage System (ESS) Definition
Roles – Bulk power, wires, customer-sited and DER
Utility distribution systems & ESS
Power, energy, reactive
Delivery asset alternative, reliability, microgrid
Multiple uses of a single ESS
Regulatory & market construct considerations
61Copyright © 2017
MICROGRID
• A microgrid is a group of interconnected loads and
distributed energy resources within clearly defined
electrical boundaries that acts as a single controllable
entity with respect to the grid. If desired, a microgrid can
connect and disconnect from the grid to enable it to
operate in both grid-connected or island-mode.
• Microgrid Key Attributes (Defining Characteristics):
• Grouping of interconnected loads and distributed energy resources
• Can operate in island mode or grid-connected if desired
• Can connect and disconnect from the grid if desired
• Acts as a single controllable entity to the grid
62
63
https://www.youtube.com/watch?v=hSOTfAOoGBs
Video of Oncor Microgrid
ONCOR MICROGRID OVERVIEW
Located at Oncor’s System Operations & Services Facility (SOSF)
What questions were we seeking
to answer by building a microgrid?
• What DER will be part of the
future grid and does it matter
where they are located?
• Will DER have an impact on
reliability or is the main driver to
be an economic generation
alternative?
• How do we educate our
customers, regulators and
legislators to their potential?
• Which customers are good
candidates for integrated DER
solutions fashioned as a
microgrid?
66
RELIABILITY & RESILIENCE FOR A KEY ONCOR
OPERATIONAL SITE
• 100-acre industrial-campus site with key operations for
meter testing, transformer testing and refurbishment,
communications, and environmental labs and compliance
• During major grid outages, site takes on 24x7 roles for
restoration and environmental management
67
Original site: 10 metered services, UPS & 3 emergency
gensets, with limited site operations during local grid outages
Project objective: single primary-metered point of service, site-
wide microgrid, adaptable to a variety of situations
ESS USES AT ONCOR’S MICROGRID
• Blackstart capability for the site
• Preserve minimum levels of state-of-charge to support the blackstart
• Demonstrate role of ESS for feeder reliability
• Time-shift energy to demonstrate
• Storage as an distribution upgrade deferral tool
• A TOU rate and energy arbitrage technical capability
• Manage site peak demand on the grid
• Future studies
• Smooth the rapid fluctuations of solar due to clouds
• Firm solar as a resource – variability due to clouds
• Power factor management for the site
68
TECHNOLOGY DEVELOPMENT & EDUCATIONAL
CENTER (TDEC)
• Create a friendly, non-technical center for conversations
about the future
• Customers
• Developers
• City leaders
• State officials
• Competitive market players
69
Microgrid
70
Oncor Microgrid Demonstration Project
Goals
• Autonomously controlled microgrid
• Multiple generation sources, both renewable and non-
renewable
• Diverse equipment from diverse suppliers to
demonstrate the integration typical of brownfield sites
• Demonstrate the ability to seamlessly combine and
switch between multiple generation sources
• Remotely control from user-friendly GUI
• Develop an Immersion Room capable of displaying the
evolution of the power grid
• Design a control room that also accommodates tour and
educational uses
71
Sequence of Operations
Oncor Confidential - For Internal Use Only72
Tesla Battery• 200 kW/ 400 kWh Stationary
Storage
• Six 70 kWh Li-Ion batteries
• Two 100 kW bidirectional
Princeton Inverter/Chargers
Specifications
• DC Capacity: 420 kWh
• Nominal AC Power: 200 kW
• Voltage Range: 288-403.5 V DC
• Nominal Voltage: 345 V DC
• Efficiency: 85%, Roundtrip
• Nominal Discharge Current (per
sub-pack) : 320 A DC
• Peak Discharge Current (per
sub-pack): 350 A DC
• Input Voltage(communications
and charging) : 3 phase 480 V
Solar Canopy and
Ground mounted PV
ArrayCanopy
• 112 kW DC
Composed of the following:
• 448 Kyocera KD F 250 W
modules
• 6 SMA Sunny Tri Powers –
480/277 V centralized inverters
• 97% Efficiency
• Large, full cantilever “tapered”
tee support structure
• South-facing – maximize energy
production
Ground Mount
• 3.5 kW DC
• Single pole mounted inverter
• Schletter FS ground mount
racking
• West-facing – output correlates
better with grid peak load times
65 kW Propane
MicroturbineSpecifications
• Output Power: 0-65 kW
• Output KVA: 65 kVA
• 30-35% efficiency
• 96000 RPM at full power
• Voltage Operating Range:
360-528 V AC
• Max Output Current: 100 A
• Short Circuit Rating: 145 A
• Power Required at Start:
6.8 kW peak, 0.014 kW/hr,
42 seconds
• Cool Down Power: 2.0 kW peak,
0.3 kWh for 90 seconds
• Standby Power: 0.8 kW
• Grid Inrush Current: 24 A
• Starting Current from Grid:
16 A
• Output Power Slew Rate:
1.15 kW/sec (900 rpm/sec)
GeneratorsTotal of 4 generators on site
supporting the micro-grid at
various locations
• Micro-grid Section 2
• Generator 2• 210 kW 480 V
• Generator 4• 45 kW 120/208 V
• Micro-grid Section 3
• Generator 3• 175 kW 120/208 V
• Generator 5• 175 kW 120/208 V
• Generator 2 and Generator 5 do
not sync correctly and therefore
cannot be paralled.
• As a result, Micro-grid sections
1 & 2 can not be tied in to
section 3 if both generator 2 & 5
are running
Transformer 16
• ABB 500 kVA , 12.47 kV/480/277
V with 480 V Delta Tertiary
• The Delta Tertiary winding has
an electrically actuated
contactor inside of the cabinet
• This contactor is used to
provide a 480 V and 12.47 kVA
ground reference when Micro-
grid Section 1 is islanded
Outline
Why Now? Cost trend for energy storage
Energy Storage System (ESS) Definition
Roles – Bulk power, wires, customer-sited and DER
Utility distribution systems & ESS
Power, energy, reactive
Delivery asset alternative, reliability, microgrid
Multiple uses of a single ESS
Regulatory & market construct considerations
78Copyright © 2017
THE OBJECTIVE – MAXIMIZE USE OF THE ASSET
• Many studies of energy storage have sought to maximize
the value of the asset by finding multiple uses
• Implementations in demonstrations and in commercial
projects also have often adopted that approach
• Uses may each draw on the energy reservoir, the immediate
power response, the reactive power capability of the power
conversion system
• Key engineering considerations are the determination of the
operating requirements for each proposed application, and
the design of a control system that will not compromise
other uses
79
GRID ENERGY STORAGE VALUES
80
BULK GRID
Wind & solar firming, smoothing and dispatch
Time-shift energy supply vs. need (eg. wind & solar) to meet market needs and/or energy arbitrage
Grid reliability services
• Supply regulation
• Frequency regulation
• Responsive reserves for grid contingency
• Fast response
DISTRIBUTION FEEDERS &
SUBSTATION
Support the local grid during upstream outages
Defer or substitute for traditional upgrades needed to support growing loads
Integrate distributed renewable sources (DERs) to the local grid to maintain grid stability & voltage control
CUSTOMER
Manage peak demand on the grid to limit demand charges
Smooth & firm customer-sited solar or wind
Time-shift energy from the grid or from customer-sited solar, such as to manage energy use under a time-of-use retail rate
Support islanded microgrid operation for critical services during grid outage
Focus of this lecture
Outline
Why Now? Cost trend for energy storage
Energy Storage System (ESS) Definition
Roles – Bulk power, wires, customer-sited and DER
Utility distribution systems & ESS
Power, energy, reactive
Delivery asset alternative, reliability, microgrid
Multiple uses of a single ESS
Regulatory & market construct considerations
81Copyright © 2017
BATTERY
TRANSMISSIONGENERATION
RETAIL ELECTRIC
PROVIDERS
DISTRIBUTION LINES
CompetitiveRegulated
ONCOR’s ROLE IN THE MARKET
Competitive ERCOT wholesale and retail electric energy market
since 2002 for investor-owned players
Regulated delivery utilities – do not generate, own, or sell electricity
Generators Transmission &
Distribution
RegulatedCompetitive
Retail Electric
Providers (REP)
Competitive
Generators Transmission &
Distribution
RegulatedCompetitive
Retail Electric
Providers (REP)
Competitive
83
Reliable delivery through the application of technology
Summary
84Copyright © 2017
LEARNINGS TO DATE
Storage is a complex technical and business consideration
Direct learning from detailed study, design, procurement,
and internal coordination is invaluable. Storage isn’t easy,
yet, for distribution feeders.
Services model: Regulation services will place challenges
on feeder voltage management and coordination, to avoid
undue wear on transformer LTC and risk of overvoltage.
Additional expense may be required.
Reliability operation: Novel blackstart with battery and
PCS present analytical challenges to assure in-rush
currents are met without damaging the ESS. Assuring
adequate fault current to operate existing protection/fuses
on the feeders is challenging.
85
EXPERIENCE WITH DISTRIBUTED STORAGE AND SOLAR
Design & specification
Siting & commissioning
Integration with system protection, SCADA, control of
traditional utility switchgear
Operational experience
• Reliability – backup to utility power
• Inverter-based systems – IEEE 1547
• Solar smoothing
• Reactive power management
86
CONTACT
Bill Muston
Oncor Electric Delivery Company LLC
214-486-3015
87
How do we reduce the length
& frequency of power
outages?
How do we increase the
efficiency of the grid?
How do we create a more
resilient, secure and even
self-healing power grid?
How do we integrate
increasing amounts of solar
and wind power into the
grid?
How do we support
customers who choose
rooftop solar and electric
vehicles?
How do we achieve all this and still
keep your monthly bill affordable?
Appendices: Glossary & References
88
Terms
SAIDI – System Average Interruption Duration Index
• Quantitative measure of the reliability of power service
• Measured in minutes/year
ESS – Energy Storage System
PCS – Power Conversion System
SCADA – Supervisory Control and Data Acquisition
BES – Bulk Electric System – definition http://www.nerc.com/pa/RAPA/BES%20DL/BES%20Definition%20Approv
ed%20by%20FERC%203-20-14.pdf
Battery Terminology Reference –
mit.edu/evt/summary_battery_specifications.pdf
89
References – Page 1
DOE Global Energy Storage Database – database of projects –
http://www.energystorageexchange.org/
Energy Storage Integration Council (ESIC), hosted by EPRI, focused on utility distribution
applications http://www.epri.com/Pages/EPRI-Energy-Storage-Integration-Council-
(ESIC).aspx
MESA – Modular Energy Storage Association – ‘Open Standards for Energy Storage’ –
http://mesastandards.org/
Sandia National Laboratory – Energy Storage Systems Program – facilitates and publishes a
variety of DOE-sponsored studies and reports related to the application of ESS –
http://www.sandia.gov/ess/
http://www.sandia.gov/ess/publication/doeepri-electricity-storage-handbook/
Lazard Levelized Cost of Energy Storage v2.0 – Examines the lifetime ownership cost for
energy storage in a variety of applications and of a variety of types of energy storage –
https://www.lazard.com/perspective/levelized-cost-of-storage-analysis-
20/?utm_content=buffer7978d&utm_medium=social&utm_source=twitter.com&utm_campaig
n=buffer
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References – Page 2
Fault Location, Isolation, and Service Restoration (FLISR)
https://www.smartgrid.gov/files/B5_draft_report-12-18-2014.pdf
Northern Power Low Carbon Network Fund Youtube Video
http://www.youtube.com/watch?v=KUGpUaA4D5k&index=1&list=UUx_iDK8VCyKqYmAkORA
hNzw
AEP Filing with PUCT on storage for specific reliability and asset deferral projects (PUCT
46368)
http://interchange.puc.texas.gov/WebApp/Interchange/application/dbapps/filings/pgControl.asp?TXT_UTILIT
Y_TYPE=A&TXT_CNTRL_NO=46368&TXT_ITEM_MATCH=1&TXT_ITEM_NO=&TXT_N_UTILITY=&TXT_N_FILE
_PARTY=&TXT_DOC_TYPE=ALL&TXT_D_FROM=&TXT_D_TO=&TXT_NEW=true
• The initial filing to open a docket:
http://interchange.puc.texas.gov/WebApp/Interchange/application/dbapps/filings/pgSearch_Results.asp?TXT_CNT
R_NO=46368&TXT_ITEM_NO=1
• The filing that described the two grid applications for deployment of energy storage in lieu of traditional utility
equipment:
http://interchange.puc.texas.gov/WebApp/Interchange/application/dbapps/filings/pgSearch_Results.asp?TXT_CNT
R_NO=46368&TXT_ITEM_NO=2 Despite this being a legal document with a regulatory agency, it contains very
readable descriptions of the two projects
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References – Page 3
Austin Energy’s DOE SHINES Project
http://www.ercot.com/content/wcm/key_documents_lists/85512/02._ETWG_Austin_SHINES.p
ptx
Pedernales Electric Cooperative DOE Project
http://www.energy-storage.news/news/ams-and-pedernales-electric-cooperative-win-us3.24-
million-energy-storage-g
Arizona Public Service ‘Solar Partners’ Energy Storage
http://www.tdworld.com/energy-storage/aps-aes-bring-energy-storage-arizona-customers
San Diego Gas & Electric Unveils Worlds Largest Lithium-Ion Energy Storage
http://www.tdworld.com/renewables/sdge-unveils-worlds-largest-lithium-ion-battery-energy-
storage-facility?NL=TDW-01&Issue=TDW-01_20170301_TDW-
01_946&sfvc4enews=42&cl=article_4_b&utm_rid=CPG04000000116581&utm_campaign=1276
3&utm_medium=email&elq2=55c63a250535471ea5d6c1a4195b2961
Oncor Confidential - For Internal Use Only92
References – Page 4
Competitively Structured Markets – See the ABACCUS report by Distributed Energy Finance
Group
• http://defgllc.com/
• http://defgllc.com/publications/consumer-choice/ Annual Baseline Assessment of Choice in the
United States and Canada
Brattle Report Examining Dual Technical Uses of Battery wherein the Users Are Utility and
Market Participants, Respectively
• Brattle Press Release – a good summary of the report
• http://www.brattle.com/news-and-knowledge/news/749
•
• Link to Full-Length Technical Report Released in 2015
• http://www.brattle.com/system/publications/pdfs/000/005/126/original/The_Value_of_Distributed_Electricity_Storage_in_Texas_-
_Proposed_Policy_for_Enabling_Grid-Integrated_Storage_Investments_Full_Technical_Report.pdf?1426377384
• Presentation
• http://www.brattle.com/system/publications/pdfs/000/005/119/original/The_Value_of_Distributed_Electrical_Energy
_Storage_in_Texas.pdf?1423513210
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ONCOR STORAGE PROJECTS
NSRI – Neighborhood Storage
Reliability Initiative
Microgrid at Oncor operational
facility
Rural Feeder Reliability – Can a
battery located on long rural feeder
support customers when the
upstream portion of a feeder is
out?
94
BRATTLE STUDY ON DISTRIBUTED STORAGE
• The Brattle Group examined the relative economics of 1000
MW to 8000 MW of distributed storage
• The system-wide (and societal) analysis shows that ~5000
MW (15,000 MWh) of distributed storage is most cost-
effective across ERCOT at $350/kWh storage cost
• System-wide benefits include:
Avoided distribution outages
Deferred distribution investment
Deferred transmission investment
Avoided new generation capacity investments
Production cost savings
• Positive payback is dependent on both regulated investment
deferral and merchant/market value of the energy
95
Homework Exercises:Thursday, March 30.
1. ESS specifications for distribution feeders depend on the applications they must serve (kVA capacity of inverter and kWh capacity of battery)
Peak Shaving (kVA and kWh requirement)
Islanding (kVA and kWh requirement)
System Protection (kVA requirement)
Background
Today, the maximum kVA of load on a feeder is 2750 kVA without overloading the substation transformer
The peak load on that feeder is projected to grow in a year from 2750 kVA to 2951 kVA
On peak load day the load is expected to go above 2750 kWh limit for 2.5 hours, as shown in the graph
The load shape is expected to be as shown in the graph, and the load will be greater than 2750 kVA for 2.5 hours
The first parts of the question will be to specify an ESS to support this increased peak load in lieu of a substation upgrade that would require a new substation transformer and bus
Assumption: assume the area of the peak load curve above the level of 2750 kVA is an isosceles triangle to simplify the calculation
Background
The next parts of the question will be, for the same feeder, specify an ESS to support the downstream half of the feeder with the ESS during an upstream outage
The outage is over the same future peak hours load curve as the prior problem
The last part of the question will be to size the ESS to support fault current for fuses serving a 3-phase load for a fault during islanded operation: A fault is assumed to occur on a feeder lateral during
islanded operation, requiring the inverter to provide fault current through the fuse on the lateral.
Additional assumptions
Assume the ESS is a perfectly efficient unit, with no losses through the inverter and no losses in the battery through charging or discharging A kWh ac is the same as a kWh dc
Assume the feeder is operating at unity (1.0) power factor
Assume the load shape during those peak hours (for the portion above 2750 kVA) is an isoceles triangle with the base being the segment along 2750 kVA
Assume the ESS performance is not affected by ambient temperature
Assume the feeder load curve is precisely halved for the A.2 problem
Questions
1. Refer to Feeder Load CurveA. What kVA capacity ESS can prevent feeder overload?B. Approximately how many kWh energy storage would be needed to
support the peaking period? C. Approximately what kVA capacity would the ESS need to be able to island
half of the feeder load during peaking time? Assume the load shape curve is precisely half for the half of the feeder to be supported by the ESS during an outage
D. How many kWh are needed? Assume the shape is a rectangle on the bottom and a triangle on the top
Refer to Fuse CurveE. A 1000 kVA 3-phase load is attached to the half of the feeder on island protected by 65 A primary fuses (12.5 kV phase-to-phase). Assume the ESS inverter can provide 150% of its continuous kVA rating for 10 seconds. Approximately what continuous kVA capacity would the ESS need to be able to operate all three fuses in under 5 seconds?
Feeder Load – 1 day
Peaking Time
5 s
Problem Statement 2Customer-Sited Storage
The commercial customer decides to install an ESS to limit its peak load, in order to reduce demand charges
The demand charge is based on the peak load over a 15-minute interval each month, and is reflected in a monthly charge on the utility bill
A. How large should the ESS be to reduce the demand incurred in the three hourly blocks of time of 14:00 thru 16:00 blocks to the level shown for the 08:00 thru 13:00 hour blocks?
B. What does the discharge and recharge profile look like, if a slow recharge is conducted over hours not being discharged?
Utility Customer
M
Meter• kWh – Total each 15-minute interval
• kW – Demand
• Time stamp
Load
Commercial Customer
Utility Customer Adds Storage
Load
ESSM
Customer Load Profile
Hour kW load
0 100
1 100
2 100
3 100
4 100
5 100
6 100
7 175
8 300
9 300
10 300
11 300
12 300
13 300
14 400
15 400
16 400
17 300
18 300
19 250
20 100
21 100
22 100
23 100
0 100
Description
The load profile is shown numerically at rightHour 0 = midnight
For simplicity, assume the load increases instantaneously at the start of the hour and continues at the level for the full hour
Assume this load profile is the same for all work days, M-F
Assume this load is not sensitive to weather changes
Demand Charge Mgt
Differential demand at peak = peak hours kW less mid-level demand = ESS kW capability
Peak duration is over the peak hour shown above
Energy in ESS needed = ESS kW x hours of discharge
Recharge Rate 24 hours less the hours being discharged