Grid Tied Battery Energy Storage: A Regulated Utility’s Path Forward 

Sherif Abdelrazek, Ph.D., PE

5 June 2018

Photo: The Duke Energy 1,775 megawatt Bad Creek-Jocassee Pumped-Storage Hydroelectric Station in South Carolina, in operation since 1991.
Outline

 Duke Energy R&D and Early Adoption of Energy Storage

 Energy Storage Project Pipeline within Duke Energy

 Duke Energy’s Future Outlook for Energy Storage: Renewables Integration

 Ancillary Services

 Renewables Integration

Copyright © 2016 Duke Energy All rights reserved. 2
Outline

 Duke Energy R&D and Early Adoption of Energy Storage

 Energy Storage Project Pipeline within Duke Energy

 Duke Energy’s Future Outlook for Energy Storage: Renewables Integration

 Ancillary Services

 Renewables Integration

Copyright © 2016 Duke Energy All rights reserved. 3
4

Duke Energy R&D and Early Adoption of Energy Storage

**402 kW / 282 kWh

Sodium Nickel Chloride - Mt. Holly, NC 36 MW / 24 MWh

Advanced Lead Acid / Li Ion - West Texas

250 kW / 750 kWh

Lithium Polymer - Charlotte, NC

75 kW / 42 kWh

Lithium Titanate - Indianapolis, IN

200 kW / 500 kWh

Lithium Iron Phosphate - Charlotte, NC

25 kW / 25 kWh

Lithium Ion - Charlotte, NC

200 kW / 400kWh

Lithium Ion - St. Petersburg, FL

4 MW / 1.5 MWh

Beckjord Station - New Richmond, OH

Residential Product Testing

Misc. - Mt. Holly, NC

Duke Energy 

tested the most 

technically 

attractive lithium 

battery 

chemistries with 

nearly 40MW of 

R&D and 

Commercial

Installations
Duke Energy R&D and Early Adoption of Energy Storage

Explore 

Technology

(R&D)

Scalable 

Demonstration

(Prove Business Case)

Regulated Asset

(Capture Benefits)

We have been here... Now we are moving here...

5
Outline

 Duke Energy R&D and Early Adoption of Energy Storage

 Energy Storage Project Pipeline within Duke Energy

 Duke Energy’s Future Outlook for Energy Storage: Renewables Integration

 Ancillary Services

 Renewables Integration

Copyright © 2016 Duke Energy All rights reserved. 6
Energy Storage Project Pipeline within Duke Energy

7

 DEP/DEC

 95 kWh Mt. Sterling 

Microgrid (Commissioned)

 75MW placeholder in the 

Carolinas IRP

 4 MW Hot Springs and 

9 MW AVL Rock Hill 

(Announced)

 DEO

 10 MW pilot program 

included in ESP

 DEI

 5 MW Camp Atterbury and 

5 MW Nabb

 Approved by IURC

 DEF

 50 MW included in utility rate settlement

 Approved by FPSC
Outline

 Duke Energy R&D and Early Adoption of Energy Storage

 Energy Storage Project Pipeline within Duke Energy

 Duke Energy’s Future Outlook for Energy Storage: Renewables Integration

 Ancillary Services

 Renewables Integration

Copyright © 2016 Duke Energy All rights reserved. 8
9

Duke Energy’s Future Outlook for Energy Storage

Duke Energy’s 

ES Outlook

Ancillary 

Services

Stand Alone

AC Coupled 

Solar Plus 

Storage

Renewables 

Integration

DC Coupled 

Solar Plus 

Storage
10

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 

How does the utility grid perceive energy 

storage?
11

Energy 

Storage 

Well, as seen by the grid,

=

How does the utility grid perceive energy 

storage?

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 
12

Energy 

Storage 

Well, as seen by the grid,

=

How does the utility grid perceive energy 

storage?

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 
13

Energy 

Storage +

Well, as seen by the grid,

=

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 

How does the utility grid perceive energy 

storage?
14

Energy 

Storage + +

Well, as seen by the grid,

=

How does the utility grid perceive energy 

storage?

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 
15

Energy 

Storage + + +

Well, as seen by the grid,

=

How does the utility grid perceive energy 

storage?

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 
16

Energy 

Storage + + +

Well, as seen by the grid,

=

How does the utility grid perceive energy 

storage?

All Basic Physical Electrical Elements in One! Energy 

Storage =

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 
Identify

Evaluate

Prioritize

Implement

Find nodes on the 

grid with maximum 

ES need. 

Conduct detailed ES 

studies to identify 

ES applications and 

stackability

Prioritize ES 

opportunities 

according to net 

value 

Implement ES 

Projects that are in 

the rate payers best 

interest

17

Energy Storage Opportunities Identification & Implementation in a Regulated Environment 

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 

• ES Can Become Cost 

Effective Through: 

1. Multi-Application Systems

2. Multi-Avoided Cost Stream 

Systems
Find nodes on the 

grid with maximum 

ES need. 

Conduct detailed ES 

studies to identify 

ES applications and 

stackability

Prioritize ES 

opportunities 

according to net 

value 

Implement ES 

Projects that are in 

the rate payers best 

interest

Identify

Evaluate

Prioritize

Implement

18

Energy Storage Opportunities Identification & Implementation in a Regulated Environment 

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 

• Multi-Application Systems: 

1. The current cost of ESSs 

rarely allow single use case 

ESSs

2. ES applications can stack in 

simultaneous manners

3. Utility ES resiliency functions 

can be easily added to support 

customer power quality 

improvement at minimal 

additional cost 
Find nodes on the 

grid with maximum 

ES need. 

Conduct detailed ES 

studies to identify 

ES applications and 

stackability

Prioritize ES 

opportunities 

according to net 

value 

Implement ES 

Projects that are in 

the rate payers best 

interest

Identify

Evaluate

Prioritize

Implement

19

Energy Storage Opportunities Identification & Implementation in a Regulated Environment 

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 

• Multi-Avoided Cost Stream 

Systems: 

1. Multi-avoided cost value 

stream projects can counter 

act high ES cost in regulated 

environments.

2. Stacking of multiple functions 

may not be necessary here. 
20

Multi-Application Energy Storage Systems Operation Example: PVS+PLS

0 5 10 15 20

-200

0

200

400

600

800

1000

Power (kW)

7/27/2014

Ppv(t)

Ppr(t)

0 5 10 15 20

-300

-200

-100

0

100

200

300

Power (kW)

Pset(t)

PBESS(t)

0 5 10 15 20

0

0.2

0.4

0.6

0.8

1

Time (Hours)

SoC(pu)

SoC

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 

[S.Abdelrazek & S.Kamalasadan. (2016). Integrated PV Capacity Firming and Energy Time Shift. 

IEEE Transactions on Industry Applications. 52. 1-1. 10.1109/TIA.2016.2531639. ]
 12.47kV Waterville Village Distribution Feeder

 Installed in 1960s

 5 Miles from nearest disconnection point

 48 poles

 1 customer (Mt. Sterling Fire Tower)

 Planned Upgrades

 22 poles to be replaced through 2026

 High cost due to helicopter operation

 O&M Challenges

 Inaccessible Terrain

 High cost vegetation management and restoration

 Averages 3+ major outage events per year

 Roughly 1 week per outage

21

Multi-Avoided Cost Streams Energy Storage Systems Example: Mt. Sterling Microgrid

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 
Overview: Utility-owned and -operated Microgrid that serves a remote customer off-grid through 100% renewable energy

Problem: Inaccessible line installed in 1960s to support 1 customer load requires high-cost upgrades and long-term outages

Timeline: 11/2016– Filed for regulatory approval; 04/2017– Received regulatory approval; 05/2017– Construction complete

22

Duke Energy’s Future Outlook for Energy Storage: Ancillary Services 

Multi-Avoided Cost Streams Energy Storage Systems Example
23

Topologies:-

Camp Atterbury/Hot Springs Projects

Mature

Technical & Financial Analysis Phase

Recently Mature

AC coupled DC coupled 

Duke Energy’s Future Outlook for Energy Storage: Renewables Integration
24

Topologies:-

Camp Atterbury/Hot Springs Projects

Mature

Technical & Financial Analysis Phase

Recently Mature

• Advantage: More efficient for renewables 

Integration. Provides a semi-dispatchable trait to 

solar facilities, reduces power intermittency 

• Advantage: Better for ancillary services functions 

for ESSs

AC coupled DC coupled 

Duke Energy’s Future Outlook for Energy Storage: Renewables Integration
25

Topologies:-

Camp Atterbury/Hot Springs Projects

Mature

Technical & Financial Analysis Phase

Recently Mature

Decline in cost of 

modules drives towards 

higher DC/AC ratio 

designs 

Decline in cost of ES 

drives better economics 

for DC coupled Solar Plus 

Storage Systems. 

Especially with higher DC 

AC ratio solar facilities • Advantage: More efficient for renewables 

Integration. Provides a semi-dispatchable trait to 

solar facilities, reduces power intermittency 

• Advantage: Better for ancillary services functions 

for ESSs

AC coupled DC coupled 

Duke Energy’s Future Outlook for Energy Storage: Renewables Integration
26

Time

Power

12:00am 12:00am Time

Power

12:00am 12:00am

Solar Power 

from DC 

system

Inverter/ IA 

Maximum 

Capacity

Energy Delivered 

Directly to the Grid 

Energy Stored in 

Battery on DC 

side of Solar

Goal: maximize solar DC capacity relative to inverter capacity such that the additional capacity can be charged during the day and discharged 

during times when solar production is less than inverter maximum capacity. 

Energy Delivered 

Directly to the Grid 

Operation:-

With Energy Storage

DC Capacity

AC Capacity

• Advantages: 

1. Intermittency reduction

2. Improved grid impact of 

solar facilities (semidispatchable)

3. Ability for solar facilities to 

reduce power without loss

4. Reduction of “Duck Curve” 

effect

5. Can provide resiliency 

benefits 

Duke Energy’s Future Outlook for Energy Storage: Renewables Integration
27

1. Duke Energy views energy storage as a prime grid ancillary services tool.

2. Energy storage projects pursuing ancillary services benefits are more successful when grid locations are 

identified properly.

3. Renewables integration applications of energy storage are better suited for some topologies versus 

others.

4. DC coupled solar plus storage systems can reduce negative impacts of solar facilities on the grid.

Conclusion
28

Questions ?