1. Bill Blevins Sep. 24, 2014 PV Forecasting RFP

2. 2 Projected Installed Capacity of PV in ERCOT

3. 3 PV Short-term Forecast Value of solar forecasts to bulk power system reliability To assist the balancing area operators in performing their duties To enhance the economic efficiency and manage bulk power system reliability operational affects on the remainder of the generation fleet Key Features: Address photovoltaics (PV) only Centralized solar forecast Benefits of size Different forecasts for different uses and time periods Next hours forecast Next day forecast Unbiased forecast typically the 50% POE (probability of exceedance)

4. 4 Experiences with Wind Forecast at ERCOT and Potential Needs for PV Forecast Delivery: Hourly - 15 minutes after the hour (may change this) Forecast period: rolling 48 hour ahead forecast Forecast parameters for each WGR -Average hourly MW -50% POE MW (labeled as STWPF used for COP) -80% POE MW (labeled as WGRPP) Short Term Wind Power Forecast

5. 5 NPRR 615 PVGR Forecasting PVGRPPPhotoVoltaic Generation Resource Production Potential STPPFShort-Term PhotoVoltaic Power Forecast PVGR PhotoVoltaic Generation Resource Approved by Board of Directors on Aug. 12, 2014

6. 6 Global Solar Irradiance (~90%), Temperature (~10%), Wind (<1%) Type of Plant –Determines exact impact of all three factors –Categories of plants: (1) PV, (2) Concentrating PV, (3) Solar thermal (also concentrating) –PV is sensitive to Global Irradiance –Concentrating types (thermal and PV) are sensitive to Direct Normal Irradiance –Also significant sensitivity variations within basic categories Factors that Affect Solar Power Solar Power Forecast Challenge

7. 7 Making the Best Forecast for Various Time Scales Minutes Ahead Cumulus clouds, small-scale cloud structures, fog Rapid and erratic evolution; very short lifetimes Mostly not observed by current sensor network Tools: persistence, skycams, local irradiance trends Very difficult to beat a persistence forecast Need: Data & tools to handle development & dissipation Hours Ahead Frontal bands, mesoscale bands, fog, thunderstorms Rapidly changing, short lifetimes Current sensors detect existence but not structure Tools: satellite-based cloud advection and NWP Need: Better forecasts of development & dissipation Days Ahead “Lows and Highs”, frontal systems Slowly evolving, long lifetimes Well observed with current sensor network Tools: NWP with statistical adjustments > ~ 10 days- climatology and climate trends Need: better NWP performance & improved MOS

8. 8 Timelines of PV Forecasting RFP 7/16/2014 RFP release 7/23/2014 Optional Notice of Intend to Propose Due 08/18/2014 Vendor Proposals Due 09/30/2014 Vendor Presentations 12/01/2014 Anticipated Contract Award 01/01/2015 Anticipated Contract Start Date Proposed/ Current timeline. May be modified based on expected ability of respondents and ERCOT to complete necessary RFP evaluations.

9. 9 Data Flow and Dependencies of Renewable Production (PVGR) Potential Forecast

10. 10 PVGRs Telemetry Meteorological Data Points ElementDevice(s) NeededUnits Plane of Array Irradiance Pyranometer or Equivalent W/m² Back Panel Temperature (Degree C) Temperature probe for back panel temperature ⁰C⁰C Air Temperature (Degrees Celsius) Temperature probe & shield for ambient temp ⁰C⁰C Wind Speed (Meter / Second) Anemometer, wind vane and wind mast m/s Wind Direction (Degrees - Zero North 90CW) Anemometer, wind vane and wind mast Degrees Barometric Pressure (hecto Pascals) BarometerhPA Plane of Array Irradiance (POA irradiance) is a measure of the total amount of solar energy that is available to an array, based the location of the array and the direction of the modules. POA irradiance is calculated at the module level, and averaged across modules to generate system-level values.

11. 11 PVPF Process Inputs Source Data Registration system 1.Resource Parameters  Resource Name  Location of PVGR (latitude and longitude or equivalent for the center point of PVGR)  Location of the meteorological station (latitude and longitude or equivalent)  Type (manufacturer/model) and number of PV panels  Panel Power Rating  Number of inverters  Inverter ratings  Tracking/Single or Dual Axis Tracking  Tracker Manufacturer  Tracker Model 1.Resource Commercial Operation Date Energy Management System (EMS) 1.Most recent Resource (PVGR) status with date/time 2.Most recent MW output of PVGR with date/time 3.Most recent meteorological measurement from one meteorological station with date/time 4.Temperature and barometric pressure on the meteorological station Telemetry valueSCADA telemetry values are sent every 5 minutes from EMS to the PV forecast service provider (all of these are Unit specific information with their Qualified Scheduling Entities (QSE) mapping) 1.MW Average 2.Wind Speed 3.Wind Direction 4.Temperature 5.Barometric Pressure 6. Back Panel Temperature(*) 7. Plane of Array Irradiance(*) 8.HSL Average 9.Num of Panels ON 10.Num of Panels Off 11.Num of Panels Unknown 12.Curtailment Flag

12. 12 PV Forecasting RFP Requirement STPPF/PVGRPP will be delivered to ERCOT hourly, providing a rolling 48-hour hourly forecast of production potential for each PVGR or the entire ERCOT systems MTPVGF is an hourly forecast service for PVGR generation and the ERCOT system for the current day and the next 7 days. The performance of PV forecasting is evaluated based on both accuracy and reliability

13. 13 Progress on RFP More than 60 questions were clarified 8 respondents received in response to RFP 6 proposals were selected for presentation to narrow down the participants in the RFP ERCOT is identifying parties to provide presentations on their approach as the next step in commencing solar forecasting.

14. 14 Bill Blevince Manager Operations Planning Electric Reliability Council of Texas, Inc. 2705 West Lake Drive Taylor, Texas 76574 Bill.Blevins@ercot.com