1. WORKSHOP ON UTILITY WIND INTEGRATION STUDIES: MODELS AND METHODS Panel 6 – Base Load Unit Cycling Costs Gene Danneman P.E. June 24 & 25, 2010

2. 2 Thermal Plant Wear and Tear (Wind Wear) Wind Penetration Wind and solar load ramps faster than load demand Thermal Plants mission changes System bottoming Ramp rate – up/down Ramp range # of cycles Increased thermal cycles cause additional wear and tear Metal Fracture causes forced outage Forced outages Increase - $$ Cost Optimization Dispatch Operations Maintenance Capital retrofits Resource planning New Flexible Units Mitigate costs / risks Start Here - Wear and Tear

3. 3 MN Wind 2008/2009 (smoothed) Day of year MW / hour (smoothed) Time of Day

4. 4 Load, Wind and Net Load: January 2013 – System Bottoming

5. 5 Conventional Plant Challenges of Wind Integration More Net Load Ramp Up & Down cycles on all units More Turn-down on baseload units Lower unit minimums Faster ramps up and down Greater Cumulative System Variability (Net Load = Load - Wind) Increased Starts/Stops on Gas-fired units Gas pipeline balancing & coal supply issues More Net Load Ramp Up & Down cycles on all units More Turn-down on baseload units Lower unit minimums Faster ramps up and down Greater Cumulative System Variability (Net Load = Load - Wind) Increased Starts/Stops on Gas-fired units Gas pipeline balancing & coal supply issues

6. 6 Load Cycling LL1Lowest Load at Which Design Superheater / Reheater Temperatures can be Maintained LL2Current Advertised Low Load (~AGC minimum) LL3Lowest Load at Which the Unit can Remain On-Line Generation Unit Cycling Definitions

7. 7 Deep Load Following Scenario Safe, Stable, Environmentally Compliant Down- Up Ramp Rate Time Ancillary Services $? ~95% FULL Load LL1 LL2 MW

8. 8 Cycling Effects Lost Generation

9. 9 Increased O&M costs Reduction in the life of key plant components and overall unit life Decrease in overall unit reliability Increase fuel cost Consequences of Cycling Damage - $$$

10. 10 Unit Flexibility Options – Many Moving Parts Unit Operation Fatigue Stress cycle damage Unit Maintenance Cycle Damage EFOR PdM/PMs System Dispatch Lower Cycling costs Energy and Capacity Transactions Impact on cycle wear Resource Planning Low cost flexible resources Unit Upgrades Improve flexibility Optimize Overall System Costs Fuel Flexibility emissions