During a 12-month review period ending Feb. 29, in order to minimize fuel costs, Progress Energy Carolinas took advantage of a “dramatic decrease” in natural gas prices and operated its natural gas-fired combustion turbines at much higher capacity factors as compared with prior review periods.
Dewey Roberts II, Manager-Power System Operations in the Transmission Operations and Planning Department at PEC, outlined the company’s power plant performance in annual fuels case testimony filed May 9 at the South Carolina Public Service Commission. PEC is a unit of Progress Energy (NYSE: PGN).
“Combustion turbines are very effective in providing reserve capacity because they can be started quickly in response to a sharp increase in customer demand, without having to continuously operate the units,” Roberts wrote. “During the review period, in order to minimize PEC’s fuel costs, PEC took advantage of the dramatic decrease in natural gas prices and operated its natural gas-fired combustion turbines at much higher capacity factors as compared with prior review periods.”
PEC’s baseload plants, on the other hand, are intended to meet the constant level of system demand. These are PEC’s large coal units and nuclear plants. The company’s four nuclear units, four Roxboro coal units, the Mayo coal unit, and two Asheville coal units are its baseload facilities. PEC’s intermediate load facilities include smaller coal units and its Richmond County CC4 and CC5 combined cycle natural gas-fired units. The intermediate coal-fired units are best utilized to respond to the more predictable system load patterns because the intermediate coal-fired facilities take some time to bring on-line from a cold shutdown state. Gas-fired combined cycle units take less time to bring on-line from a cold shutdown state.
“During the review period, due to the dramatic decrease in natural gas prices and the generator efficiency of our Richmond County combined cycle units, these combined cycle units were operated in more of a baseload manner and often were dispatched before PEC’s large baseload coal units,” Roberts said.
Coal units at Cape Fear and Weatherspoon retired
With respect to unit additions and retirements, for the 12-month period ending Feb. 29, PEC added the Richmond County CCS combined cycle generator with summer and winter capacity ratings of 652 MW and 708 MW, respectively. During the review period, PEC retired the Cape Fear 1 Steam Turbine, Cape Fear 2 Steam Turbine, and Weatherspoon Units 1-3. The total summer rating capacity retired was 188 MW. The Weatherspoon coal units were retired last October.
In 2009, Progress Energy announced a plan to shut down 11 coal-burning units at four sites in North Carolina. Other plants slated for retirement besides the Weatherspoon coal units include H.F. Lee near Goldsboro, L.V. Sutton near Wilmington and Cape Fear near Moncure. The retirements of these unscrubbed units, representing about 1,500 MW, or 30% of Progress Energy’s coal fleet in North Carolina, are scheduled to be completed by the end of 2013.
“The transition from older coal-fired units to new combined cycle gas-fired units is a result of our [integrated resource plan] process that includes consideration of retrofits and additions of clean air equipment that would have been required to comply with federal regulations,” Roberts said. “This transition also places the Company in a good position to take advantage of increased natural gas supplies and resulting lower natural gas prices. This transition will continue through 2013.”
For the 12-month period ending Feb. 29, the company generated 58,275,560 megawatt hours of electricity. Nuclear plants generated 48.19% of that, coal plants generated 35.74%, combined cycle and combustion turbine units generated 14.93%, and hydroelectric units generated 1.14%.
The combustion turbines averaged 83.96% equivalent availability for the review period. Their capacity factor was 6.65%, which is higher than normal due to the cheap gas supplies.
The Richmond County combined cycle units had an average equivalent availability of 93.14% and a capacity factor of 72.86% for the twelve-month period. The increased capacity factor compared to prior review periods reflects the gas-fired combined-cycle unit’s taking advantage of cheap gas.
The intermediate (or cycling) coal units had an average equivalent availability factor of 88.68% and a capacity factor of 27.36% for the twelve-month period. This lower capacity factor reflects PEC’s greater use of its natural gas-fired generation. The baseload coal units had an average equivalent availability of 89.67% and a capacity factor of 72.21% for the twelve-month period.
For the twelve-month period, the company’s nuclear generation system achieved an actual capacity factor of 91.77%. Excluding outage time associated with reasonable outages, such as refueling outages, the nuclear generation system’s net capacity factor for this period rises to 101.8%. In contrast, the NERC five-year average capacity factor for 2006-2011 for all commercial nuclear generation in North America was 89.59%, Roberts noted.
PEC owns and operates four nuclear generating units: Brunswick Units 1-2, Harris and Robinson.
The coal-fired fleet achieved an equivalent availability factor of 86.62% for the latest review period. This performance indicator exceeds the most recently published NERC average equivalent availability for coal plants of 83.61%. The NERC average covers the period 2006-2010 and represents the performance of 921 coal-fired units. Equivalent availability is a more meaningful measure of performance for coal plants than capacity factor because the output of PEC’s coal units varies significantly depending on the level of system load.
For the twelve-month period ending Feb. 29, the baseload coal units Asheville 1 and 2, Mayo Unit 1, and Roxboro Units 1-4, operated at equivalent availabilities of 82.33%, 87.80%, 90.05%, 70.86%, 70.93%, 91.71%, and 98.84%, respectively. Roxboro Units 1-2 equivalent availabilities are low relative to the NERC average primarily as a result of a major boiler overhaul outage and a major condenser tube replacement outage for Units 1 and 2, respectively.
The gas combined-cycle units achieved an average equivalent availability of 93.14% and a capacity factor of 72.86%. These indicators compare well with the NERC 2006-2010 five-year industry average equivalent availability of 87.17% and capacity factor of 37.40% for 187 combined-cycle units, Roberts said.
The hydroelectric units, which can see wide variances due to factors like seasonal water flows, had an equivalent availability of 95.74% and operated at a capacity factor of 33.26% for the twelve-month period. The five-year industry average for hydro generation as published in NERC’s most recent report reflects an average equivalent availability of 84.93% and an average capacity factor of 39.86%.