a quantitative assessment of community energy storage for...

Towards a Distributed Grid: A Quantitative Assessment of Community

Energy Storage for Islanding

Robert L. Fares UT Energy Symposium

March 21, 2013


March 21, 2013 2

Introduction

• Community Energy Storage

–  25 kW –  25 kWh –  85% efficient

• Applications: –  Load shifting –  Islanding –  Local power system

control


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The Grid Has a Centralized Architecture

Source: Texas Electricity Alliance


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Distribution-Level Outages Aren’t Uncommon


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Solar Photovoltaic Installations by State

The Grid Has Grown More Distributed

Source: National Renewable Energy Laboratory Open PV Project


March 21, 2013 6

Solar Photovoltaic Installations by State

The Grid Has Grown More Distributed

Source: National Renewable Energy Laboratory Open PV Project

1998 2000 2002 2004 2006 2008 2010 20120

2

4

6

8

10

12U.S. Photovoltaic System Prices

Year

Ave

rage

Inst

alle

d C

ost (

$/W

)


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Distributed Energy Storage Can Form a Microgrid During an Outage


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• The instantaneous electric load

• The instantaneous level of solar generation

• The capabilities of the battery system

The Islanding Lifetime of Community Energy Storage Depends on a Number of Factors


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1

2

3

4

5

6One Home - August 5th, 2011

Time

Pow

er (k

W)

0:00 4:00 8:00 12:00 16:00 20:00

Electric DemandPV Generation

-10

0

10

20

30

Seven Homes - August 5th, 2011

Time0:00 4:00 8:00 12:00 16:00 20:00

Net

Ele

ctric

Dem

and

(kW

)Pecan Street Data Reveals the Precise Load on

Community Energy Storage


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A Circuit Model Describes the Dynamic Capabilities of Community Energy Storage

M. Chen, G. Rincon-Mora, Accurate electrical battery model capable of predicting runtime and I-V performance, IEEE Transactions on Energy Conversion 21 (2) (2006) 504 – 511. doi:10.1109/TEC.2006.874229.


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• Community energy storage powers seven downstream homes in the case of an outage

• Outages occurring each hour of August 2011-February 2012 are simulated using Pecan Street data

• Homes with and without rooftop solar panels are considered

Thousands of Outages Are Simulated to Show the Expected Islanding Lifetime


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August - September 2011

Time of Outage

Isla

ndin

g Li

fetim

e (h

ours

)

0

3

6

9

12

15

18

21

0:00 4:00 8:00 12:00 16:00 20:00

Lifetime Range (No Solar)Mean Lifetime (No Solar)Lifetime Range (Solar)Mean Lifetime (Solar)


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October - November 2011

Time of Outage

Isla

ndin

g Li

fetim

e (h

ours

)

0

3

6

9

12

15

18

21

0:00 4:00 8:00 12:00 16:00 20:00



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December 2011 - February 2012

Time of Outage

Isla

ndin

g Li

fetim

e (h

ours

)

0

3

6

9

12

15

18

21

0:00 4:00 8:00 12:00 16:00 20:00



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August 2011 - February 2012

Time of Outage

Isla

ndin

g Li

fetim

e (h

ours

)

0

3

6

9

12

15

18

21

0:00 4:00 8:00 12:00 16:00 20:00



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Comparison to Weather Data Provides a Sanity Check

• Minimum Islanding Lifetime Observed: –  42 minutes for an outage at 4:00 pm on August

28, 2011

3/15/13 Austin ties all-time high: 112 degrees | www.statesman.com

www.statesman.com/news/news/local/austin-ties-all-time-high-112-degrees/nRdyW/ 1/2

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Updated: 10:13 p.m. Sunday, Aug. 28, 2011 | Posted: 8:08 p.m. Sunday, Aug. 28, 2011

Austin ties all-time high: 112 degreesRelated

By Suzannah Gonzales

AMERICAN-STATESMAN STAFF

The high Sunday of 112 degrees tied the all-time hottest temperature recorded at Camp Mabry.

And the weather recording station at Austin-Bergstrom International Airport had its third-warmest day ever and broke therecord for the month of August with a temperature of 109.

Before Sunday, the record high logged at Camp Mabry came on Sept. 5, 2000, National Weather Service forecaster PatMcDonald said. The previous August record at Austin-Bergstrom was 108, reached on Aug. 8, 2003, he said.

By Sunday evening, both Austin-Bergstrom and Camp Mabry had broken records for the day set in 1990, according to theweather service .

Today's forecast calls for 106 degrees at Austin-Bergstrom and 108 degrees at Camp Mabry, temperatures that, if reached,would also break daily records, National Weather Service forecaster Chris Morris said.

The Texas Commission on Environmental Quality said today 's ozone forecast for Austin and several other Texas cities is atLevel Orange, which means that active children and adults and people with lung disease or asthma should cut back onlengthy or heavy activity outside.

The hot temperatures didn't stop hundreds of people from going to Waterloo Park in downtown Austin on Sunday for theAustin Chronicle Hot Sauce Festival , an annual contest and fundraiser for the Capital Area Food Bank of Texas.

"This is a hot sauce paradise," Nikhil Choudhary said, waiting in a "XXX" line to sample the hottest of the hot.

"If it burns, just keep going," advised Mark Webb , a 20-year veteran of the festival. For Webb, the hotter, the better. "It makesyou feel alive."

On Sunday, the Electric Reliability Council of Texas reported that customers' weekend usage was record-breaking andwarned that an all-time peak demand record could be set today or Tuesday. ERCOT, which operates the power grid thatserves three-fourths of the state, urged Texans to conserve power from 3 to 7 p.m. daily.

"If every person in ERCOT does a little, it makes a huge difference," the council said in a statement on its website.

A heat advisory for South Central Texas has been extended through 9 tonight , Morris said . Heat advisories are declaredwhen the heat index — what it feels like, or the apparent temperature — is 105 or above and the low temperature overnightdoesn't drop below 80, Morris said.


March 21, 2013 17

Conclusions

• High-resolution residential energy data permits novel analysis of emerging energy technologies

• Rooftop solar panels significantly increase the islanding lifetime of community energy storage during a morning outage

• Community energy storage significantly increases the value of rooftop solar panels during an outage


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• Explore synergy between existing distributed solar assets and community energy storage

–  Correct power factor

–  Firm solar generation to compensate for clouds

–  Storage and then dispatch solar energy

Future Work


March 21, 2013 19

Acknowledgements

• The University of Texas at Austin

• Dr. Michael E. Webber

• Pecan Street Inc.

• U.S. Department of Energy Smart Grid Demonstration Program


March 21, 2013 20

Questions? Robert L. Fares

[email protected]

Graduate Research Assistant Thermal Fluids Area

Mechanical Engineering The University of Texas at Austin

www.webberenergygroup.com

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