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Flexibility and Storage for Integration of Renewables

Daidipya Patwa

Senior Analyst,

Renewable Integration and Integrated Resource Planning

Pacific Gas & Electric

January 25, 2011

Flexibility and Storage for Integration of RenewablesDaidipya Patwa

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Outline

I. Background

II. Renewable Integration in California

III. PG&E’s Storage Projects

IV. On-going Industry Initiatives

Flexibility and Storage for Integration of RenewablesDaidipya Patwa

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Background

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California Future Generation Mix

Source: CPUC, 33% RPS Implementation Analysis Preliminary Results. June, 2009, California Public Utilities Commission

Flexibility and Storage for Integration of RenewablesDaidipya Patwa

5Wind and Solar are Highly Variable• Wind and solar are variable resources:

– Variability: the magnitude of power output from one moment to the next can change dramatically

– Unpredictability: sudden changes in generation output not well-forecasted

Sources: http://www.caiso.com/2747/274778eb12970.xls

Apt J. and Curtright A., “Spectrum of Power from Utility-Scale Wind Farms and Solar Photovoltaic Arrays”

CAISO July 2009 Wind Generation, MW Solar Generation in Springfield, AZ

Flexibility and Storage for Integration of RenewablesDaidipya Patwa

6Flexible Resources Maintain BalanceFlexible generation manages uncertain real-time load and generation

-

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

55,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Load

Hours

MW

-

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

55,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Load

Real-Time Load Uncertainty and Forecast Generation(CA 5 Minute Load 11am-12pm Peak Day 2005 and Hypothetical Generation)

5 Min Avg Load with Intra 5 Min Vol bounds

39,500

39,700

39,900

40,100

40,300

40,500

40,700

40,900

41,100

41,300

41,500

661

664

667

670

673

676

679

682

685

688

691

694

697

700

703

706

709

712

715

718

5 Min Avg Load

MW

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7Flexible Resource Provide Ancillary Services

Load Following: Difference between the hourly schedule (red line) and the 5-minute schedule (blue line)

Regulation: Difference between the 5-minute schedule (blue line) and the actual load/wind (green line)

Source: California ISO

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Renewable Integration in California

Flexibility and Storage for Integration of RenewablesDaidipya Patwa

9Integration Framework to Determine Flexibility Need

Reserve Requirements

Additional System

Requirements

Technology Mix and Costs

Define reserve requirements based on load and generation characteristics

Evaluate system operation to determine additional resource needs and characteristics (MW, ramp times, etc)

Determine mix of technologies for meeting system needs weighed against costs

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Integration Studies in California

Approaches CAISO StudyRenewable Integration Model

(PG&E)

Explanation

• Production simulation model using Plexos

• Simulate operation of grid hourly

• Identify and solve operating violation by adding flexible capacity

• Estimate flexibility need analytically

• Simplified representation of key drivers of flexibility need

Advantages

• Detailed representation of grid

• Existing and new resource limitations represented

• Produces results in minutes

• Can vary/test sensitivity of results

• Accessible (uses simple tools)

Disadvantages

• Requires thousands of assumptions

• Slow (takes days) to estimate need

• Becomes outdated fast

• Simplified representation of grid

• Need to calibrate results

There is no standard approach to estimate flexibility needs

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Integration Needs Defined

Statewide Maximum Operating Flexibility

Requirements (Summer Season)

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

2009 PG&E RIM20% RPSin 2020

PG&E RIM33% RPSin 2020

CAISO33% RPSIN 2020

MW

Regulation

Load Following

Day-ahead Commitment

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Sources for Flexibility

Source: P. Denholm, NREL, 2010; B. Nickell, DOE, 2008

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PG&E’s Storage Projects

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Helms Pumped Storage Plant

Location Central California

Commissioned June 30, 1984

Installed

Capacity

Three units;

1,212 MW generating;

930 MW pumping

• Storage of economy energy at night and spring run-off

• Alleviate over generation and minimum load conditions

• Meet fluctuations in demand and act as reserves

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Current Storage Initiatives

CAES

• 4 MW system in San Jose

• 2 MW system at Vaca-Dixon substation

• Test load shaping, providing ancillary services, balancing solar

NaS Battery Pumped Hydro

• Mokelumne

• Proposal to connect 2 reservoirs

• Existing salt dome reservoir

• Partnership with DOE, CEC, CPUC

• 300MW, up to 10* hours storage

* Final project size to be determined

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Current Industry Initiatives

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CAISO: REM Initiative

• Regulation Energy Management (REM)

• Program to test usefulness of limited energy resources (batteries) for regulation services

Source: CAISO, “Regulation Energy Management Draft Final Proposal” Dec 14, 2010

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CPUC AB2514

Directs California Public Utilities Commission to:

• Determine targets, if any, to procure viable and cost-effective energy storage

• Adopt by October 1, 2013, an energy storage system procurement target, if appropriate.

•Approved by Governor September 29, 2010

CPUC initiated Order Instituting Rulemaking (OIR) on December 21, 2010

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Conclusion

• At penetrations of 33% of electricity from renewable resources, changes will be required in the supply portfolio.

• At higher penetrations, highly flexible resources will be essential.

• A mix of supply-side and demand-side resources (including storage) will create a flexible electric supply portfolio.

• On-going industry initiatives to investigate storage in California

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Thank You

Daidipya Patwa

d2pa@pge.com