1. Optimizing Deployment of CCGT Duct Firing Capacity in the Nodal Market Josh Clevenger Brazos Electric Cooperative

2. Combined Cycle Plants with Duct Firing Duct firing allows the capacity of the steam turbine generator (STG) to be extended beyond the waste heat captured from gas turbines (GT’s) through gas burners located in the Heat Recovery Steam Generator (HRSG). Duct firing capacity is less efficient than GT /STG capacity thus it is typically only utilized when the GT/STG is completely dispatched (“base load”.)

3. The Challenge in Nodal Duct Firing capacity has dynamic limitations. Ramp rates for DF/STG capacity are significantly lower than CT/STG ramping capabilities. The maximum output capability of GT’s varies significantly with ambient conditions, thus the net MW transition from base load to duct-firing will vary day to day and hour by hour.

4. CCGT with Duct Firing Minimum Output Variable – GT/STG Output Variable – DF/STG Output Minimum OutputVariable – GT/STG Output Variable – DF/STG Output Warmer Temperatures Cooler Temperatures HSL can differ for each hour in COP. Ramprate curve can only be updated in MIS Operating Parameters Transition from base-load to duct firing

5. ERCOT Limitations ERCOT processes (DAM and RUC) utilize RARF data for CCGT’s that recognize multiple plant configurations ERCOT has ruled out acceptance of additional configurations specifically set around duct-firing operations.

6. Current ERCOT Treatment DAM and SCED take into account ramp rate curve submitted by QSE in the RARF to detect limitations on base-point changes as well as Regulation and Responsive limitations at specific plant dispatch levels. ERCOT will accommodate updating the CCGT ramp rate curve through MIS operating parameter submittals.

7. Questions Will DAM clearing engine replace RARF ramp rate curve with operating parameter values? If yes, does this still leave inaccuracies with regard to hourly changes in base load capability for the next day? Is DRUC/HRUC impacted by incorrect information on ramp rate if DAM/SASM fail to procure sufficient A/S capacity?

8. Questions Will SCED have a delay in processing updated ramp rate curves submitted as MIS operating parameter updates? Or will this data be transferred in real time? Under what circumstances will the ramp rate curves submitted as MIS operating system updates be rejected as conflicting with the RARF?