Western Wind Integration Study Kevin Porter – Exeter Associates, Inc. Brian Parsons, Michael Milligan, Debbie Lew – NREL DOE Wind Program Peer Review July 11-12, 2007

Why is this study needed? Southwest is fastest growing load in US (4%/yr) Many transmission projects planned to serve this region. Better information needed to select routing, generation sites, etc. RPS requirements in NV, AZ, NM, CO and increasing CA and NW already engaged in regional processes What is the goal of this study? To examine the operating and cost impacts due to the variability and uncertainty of wind and solar on the grid and to investigate mitigation options for those impacts To support the Western Governor’s Clean and Diversified Energy Initiative (30GW by 2015) and the President’s Advanced Energy Initiative (up to 20% wind in US)

Questions to answer Can the region accommodate wind penetration levels of up to 30%, and solar penetrations of up to 5%? How does potential large-scale wind deployment in WestConnect interact with potential large-scale deployment in the rest of WECC? What are the benefits and trade-offs of accessing in- state wind resources or importing better class resources from out-of-state? Can geographically diverse resources reduce variability and increase transmission utilization? What are the benefits of balancing area cooperation/consolidation (e.g., WestConnect Virtual Control Area project)? How can hydro help with wind integration? Are there limits to the use of hydro for wind integration? How does wind and solar contribute to reliability and capacity value? What is the role and value of wind forecasting?

Study footprint 9 Control areas Nevada Power Sierra Pacific Arizona Public Service Tucson Electric Salt River Project Public Service of NM El Paso Electric Xcel WAPA/Tri-State

Stakeholder Interactions Sought input and participation from: –DOE/OE 2/6 –WECC Transmission Expansion Planning Policy Committee 2/15 –WestConnect 3/15 –Southwest Transmission Expansion Planning 3/16 –Colorado Coordinated Planning Group 4/25 –SouthWest Area Transmission 5/15 –Transmission Expansion in the West Conference 5/21 Other stakeholders include: –Wind industry (AWEA, WWW, Interwest) –WGA Western Interstate Energy Board –PUCs and states (CO PUC, NMEMNRD, WIA) –Transmission project sponsors (Transwest, HPX, TOT3) Stakeholder kick-off meeting 5/23 at NREL: –56 participants including those listed above –Refined the study footprint, provided input into % penetration levels, and provided feedback on methodology

Tasks Data Collection –Wind and solar mesoscale modeling –Utility load, generator, transmission data Preliminary Analysis –Extensive statistical analysis of 10, 20, 30% wind with various options for wind sites and transmission Scenario Development –In-state vs out-of-state resources –Geographically diverse resources –Mega projects –Best correlated with load Run Scenarios –Examine costs due to regulation, load following, unit commitment –“Dives” to investigate issues such as Hoover –Examine mitigation strategies/options –Determine contributions to reliability and capacity value Draft and Final Report

Schedule Kickoff Stakeholder Meeting5/23/07 Data CollectionJun-Dec ’07 Wind/solar mesoscale modelingSep ‘07-Mar ’08 Preliminary AnalysisFeb-May ’08 Prelim. results stakeholder mtgJun ’08 Production Cost ModelingJul ’08-Jan ’09 Interim Technical Results mtgDec ’09 Draft reportFeb ’09 Draft results Stakeholder mtgMar ’09 Final ReportApr ‘09

Subcontract Costs PartnerTaskCost GEAnalysis and simulations~$1M 3TierWind mesoscale modeling~$ M Exeter AssociatesData collection~$50k Richard Perez/SUNY Solar modeling~$15k Oak Ridge National Lab Hydro Modeling~$50K UWIG, Renewable Energy Consulting Services Technical review and input~$40k