A Look at Secondary Use Energy Storage

Michael Starke, PHD Oak Ridge National Laboratory

Hosted by:

FEDERAL UTILITY PARTNERSHIP WORKING GROUP SEMINAR

April 22-23, 2015 Nashville, TN

Project Overview

• Supporting the industry investigation into vehicle battery secondary-use through testing, demonstration, and modeling. – Potentially a cost competitive energy storage technology – Validate reliability and safety – working with industry to

troubleshoot and test systems under operational conditions – Examining regulatory environment – investigating hurdles

that are institutional – Industry acceptance – build confidence in this technology.

2

Secondary Use of EV Batteries

• Potentially significant electric vehicle market. – Projections from different studies

show significant growth.

– March 2014, Tesla announces news on the building of a Gigafactory with projections of 500,000 vehicle production capability by 2020.

– June 2014, Tesla is releasing all patents to encourage electric car production

• What can we do with the on-board battery technologies?

Repackage/Reuse: Could provide a low-cost grid storage solution (if design of repackaged system does not require significant modifications and added expense.)

Already Available in USA • Over 150,000 plug-in electric vehicles (PEVs) currently in USA (study

by UCLA Luskin Center for Innovation – December 2013)

– ~ 55% of PEVs are PHEV and 45% are BEV

– Near 70% of these vehicles are Nissan Leaf, Chevy Volt, or Tesla

• Leads to a an estimated 3.485GWh of existing battery storage.

• Estimates on capacity of the batteries. Detailed analysis will need to consider operational constraints, BMS level limits, and other aspects.

Nissan Leaf Nearing 40,000

Vehicles 24 kWh per pack

~960MWh

Chevy Volt Exceeding 50,000 Vehicles

16.5 kWh per pack ~825MWh

Tesla Nearing 20,000

Vehicles 85 kWh per pack

~1700MWh

Demonstration Sites: Repurposing of Batteries

• Utilizes BMW mini-E batteries and BMS/Princeton Power Systems interface hardware

• 108 kW/180kWh with DC coupling to PV

• Utilizes General Motors Volt batteries and BMS/ABB interface hardware.

• 25kW/50kWh system connected to ORNL test-bed, PV smoothing and shifting.

Current Activities

HARDWARE

SYSTEMS INTEGRATION

SOFTWARE

• Energy Storage – Used EV Batteries

• Energy Management System • Electric Grid

An effective partnership that merges equipment, technical know-how, and infrastructure:

ORNL is testing and demonstrating the technology as a third party.

The Technology

Grid Application(25kW/50kWhr)

– Expected capacity for 10 Years of Operation

– 5 Volt Battery Packs

– 5 kW per Volt Battery

– Air Cooled/Heated

Automotive Application

– Capacity for 10 Years in Automotive Application

– Power 111kW

– Liquid Cooled / Heated

GM Chevy Volt Battery

Re-Packaged

ABB Enclosure

The Working System

Grid Load

Inverter

Battery

Management

System Cell

Modem

Battery Stack

240V

1ϕ

Voltage Sense AC Input

DC Output CAN Comm.

Temperature Sensors

Voltage/Current

Sensors

Contactor Control

CAN Comm.

Interlocks

Door/Estop Sw.

Intput

Door/Estop Sw.

Intput

EstopBatt. Door

Switch

Inv. Door

Switch

Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

HVAC

Unit

PV Array

Zone 1: The system has a single-phase connection with the grid, PV Array, AC breakers, islanding contactor, and voltage sensing. Zone 2: Inverter measures and senses inputs to control charging and discharging needs (4 quadrant) Zone 3: Batteries connected on DC link and controlled by BMS. BMS uses voltage, current, and temperature information to relay control information to inverter. Zone 4: Safety interlocks to prevent unsafe access Zone 5: Thermal management with fans, heaters, and HVAC. Multi-tiered layers of security are present in the

system to ensure a safe operation

Islanding Contactor

System Benefits: CES

CES

CES

CES

Subst

atio

n

Command

and Control

ISO request

(ancillary

services)

Local benefits: Real and Reactive Power Support • demonstrate that load factor and power factor can

be maintained.

Service reliability • during outage, CES unit can still supply load for a

period of time.

Phase balancing • if three units are installed (each on separate

phases) additional energy can be used to balance phases.

Grid benefits: Firming and shifting Renewables and Load leveling / T&D Deferral • battery can charge/discharge depending on

control and load behavior.

Ancillary Services • regulation/spinning

Transformer

Renewables

Bi-directional

smart meter

Junction

Box

Disconnect

switch

DC/AC

AC/DC

Converter

Repurposed

Battery

Pack

CES Unit

EV/PHEV

Similar benefits can be realized by distributed energy storage for commercial applications

Testing Setup at ORNL • ORNL objective for testing: Provide real world examination systems

integration and applications with the flexibility to capture many different case scenarios.

ORNL Distribution

System

750kVA, 13.8kV/2.4kV

Circuit #22.4kV System

750kVA, 2.4kV/480V

480V, 3 Phase, 60Hz

2.4kV, 3 Phase, 60Hz

13.8kV, 3 Phase, 60Hz 480V Distribution

Panel

Disconnect Switch

37.5kVA, 120V-240V/480V

Programmable Load Bank (240V,

Split Phase, 24kW)

Community Energy Storage (240V, Split

Phase, 25kW)

Disconnect Switch

480V, 3 Phase, 60Hz

240V, Split Phase, 60Hz

480V/2.4kV

50kW PV

50kVA inverter

15kW PV

1 Hardware 2 Communications 3 Controls

Hard/Soft: Communication and Control

Communications and Control

and Measure & Validate

• Communications and control done through Serial, Modbus over Serial, and TCP/IP

• All integrated through Matlab/Labview

• Load Bank utilized for Emulation.

DECC Facility

Communications Cable, RS232/RS485

over Modbus

Communications Cable, RS232

ORNL/Distribution

CT/VT

CT/VT

CES

ROOFTOP PV

CONTROL/COMPUTING

GRID

M&V

CT/VT

LOAD

Hardware: Equipment Inside DECC

480V/240V(split-phase) Transformer

Islanding Contactor/Relay

Programmable Load Bank

Emergency Disconnect

Battery Enclosure

Inverter

Hardware: Equipment Outside DECC

Emergency Disconnects

PV Array

Interface Set of pre-programmed controls

CES Alarms

Manual Control

State display

Controls and Programs

PV Forecast

Load Factor Control Points

SOC Estimate

text message

Cloud Cover

Solar Irradiance/PV output

Residential Model Consumption

% Cloud Cover Temperature (C)

Temperature

solarirradiance

GA Optimization

kW load

kW PV

Measured Data

Main ControlEmergency Monitoring

Data Acquistion

Load Bank

Shutoff

email

Data Processing

Data

Historian

Data

Load Bank Temp

Temperature (C)

Control Mode, P, Q

Storage

• Auto-runs at 12:00AM

• Controls depend on selected settings.

Measurements and Simulation Additions

• Load Bank is controlled to follow residential load profiles through macros.

Load Bank Interface

Residential Model Consumption

Macro is running

Power Consumed by Bank 1

• Residential profiles are developed through modeling and historical data collection.

Residential Modeling

Sleeping

Grooming Laundry

0.025

0.85

0.015

0.15

0.05

0.035

0.95

0.8

0.125

• Residential data has been sub-metered and collected for several years. Used to develop and validate load models.

Rin = 1/UAinsul

Tamb

Tindoor

Tmass

Cmass

Rin = 1/UAmass

Cair

QHVAC QSOLAR

QINTER

Home Model/HVAC

Markov Chains Activity Simulation

• Markov Chains are used to drive residential loads such as washer/dryer/water heaters…

PV Forecasting for Optimization

Solar Panel/Model

Cloud Forecast

Historical Data

Solar Irradiance

PV Curves

Maximum Value

MMPT (Power)

Module Temp

Ambient Temp

Solar Thermal Model

Neural Networks(Irradiance Forecast)

Collect Cloud Forecast

Weather Underground

Testing Procedure (Systems Tests) • Objectives:

– Obtain standard metrics (round-trip efficiency/ensure within bounds of standards)

– Demonstrate application examples

• Standard Metrics: – Round-trip efficiency

– Harmonics, etc.

• Applications – Load factor,

– Power factor,

– Renewable Integration,

– Islanding

Start

Charge Battery at Requested Power Level to 70% SOC

Rest Battery for 30 Minutes

Discharge Battery at Requested Power

Level for 30 minutes

Rest Battery for 30 Minutes

Time Since Last Power Level Change > 24 Hours?

At Maximum Power Level?

Increase Requested Power Level

No

Yes

No

Yes

Stop

Requested Power: 5

kW

Multiple Value Streams: Stacking Benefits (Load Factor/Power Factor, Renewable Integration)

Grid (nearly flat)

Power (W)

Time (hr)

Power (Var)

SOC (%)

Time (hr)

Time (hr) Time (hr)

Histogram power factor

Target Set to 0.97

SOC target to return to 50%

TE: PV Smoothing/Capacity Firming Objectives: Integrate PV by removing oscillations and error in forecast. Benefits: 1) Removing oscillations

in PV output can impact local voltage.

2) In some cases these oscillations lead to significant tap changes in transformers. Smoothing this behavior with storage can extend transformer life.

Power (kW)

8 10 12 14 16 18 20-6

-2

2

6

10

1403/22/2014

Time (Hr)

Pow

er (

kW

)

Total PV Power

CES Power

Net Power

Predicted PV Power

Power (kW)

TE: Islanding Mode Objectives: Utilize storage for emergency backup power Benefits: 1) Provides power during

an outage 2) Can be used to

support contingency type events as well to reduce load consumption.

Grid power

Battery-supplying

entire load

Initial Economic Approach

(Mixed Integer) Linear

Optimization Grid

Services

Battery Model

Data

Optimal Battery

Dispatch

Cost/Savings

• Arizona Public Service Company residential rate structures • Year-long simulated load for 3 homes • Dispatch the battery to minimize the homeowners’ cost • Utilized efficiencies of real system, 10year/3000 cycle

battery

Initial Economic Results

Initial Economic Results

Future Tasks

• Modeling and economics assessment for DES.

• Development of refurbished secondary use ES.

26

L1

L2

L3

S11

S12

S21

S22

S31

S32

C3

C2

C1

S1 S2 S3

S4 S5 S6

BMS

BMS

BMS

V1

I1

V2

V3

I3

Va

Vb

Vc

G12

G11

G21

G22

G31

G32

G1

G2 G3

G6G5G4

G11, G12

G1, G2, G3, G4, G5, G6

Estop1, SOC1, kWh1, kW1

Estop1, SOC1, kWh1, kW1

DC/DC Converter 1

V1, I1

Va, Vb, Vc

Ia, Ib, Ic

Inverter Control System

Preq, Qreq, Mode

DC/AC Inverter/Grid Connection

G1

La

Lb

Lc

Battery

I2

Battery

Battery

Ia

Ib

Ic

3ϕ 480VAC

600VDC

<500VDC,

25kW

L4

S41

S42

BMS

V4

I4

G41

G42Battery

L5

S51

S52

BMS

V5

I5

G51

G52Battery

<500VDC,

25kW

<500VDC,

25kW

<500VDC,

25kW

<500VDC,

25kW

C4

C5

100kW