Power Generation

The decision to upgrade powerplant control systems is not a simple one; however, the economic payoff can be substantial. Recent studies by Siemens Westinghouse (Newcastle, UK) indicate that improvements in plant performance thorough controls modernization can be substantial. For a typical 540-MW coal-fired powerplant, instrumentation and controls changes are projected to save a combined $1.8 million per year:

• Fuel savings during normal operation: 0.4%—or $283,000/yr—is possible, mostly from tighter steam-temperature control, more accurate combustion and oxygen control, and conversion from fixed-pressure to sliding-pressure operation.
  
• Fuel savings during startup: 50%—approximately $17,000/yr—is possible. Automated controls enable a plant to adhere more closely to stress limitations.
  
• Fuel savings during load ramps: It is possible to achieve load-ramp rates of 5% of MCR/min above 60% load and 3%/min between 35% and 60% load. Improved ramp rates allow the unit to respond faster, thus “catching” higher market prices and reducing load quicker when the market prices drop. Savings are estimated at $532,000/yr.
  
• Fuel savings due to reduced forced-outage rates: National Electric Reliability Council data indicate that the average forced outage rate for a coal-fired unit lasts about 20 hours. If a plant can reduce that figure by more intelligent controls, safe run-back to partial loads instead of a trip, and improvements in trip-system reliability, then it can save just over $1 million/yr.