1.14 The following table gives capital costs and variable costs for coal plants, NGCC plants, and natural-gas-fired CTs. Coal NGCC CT Capital cost ($/kW) 2000 1200 800 Variable cost (/kWh) 2.0 4.0 6.0 This is a municipal utility with a low fixed charge rate of 0.10/yr for capital costs. Its load duration curve is shown below. 62 1000 900 Demand (MW) 800 700 600 500 400 300 200 100 0 0 1000 2000 3000 6000 7000 8000 9000 4000 5000 Hours/year FIGURE P1.14 a. On a single graph, draw the screening curves (Revenue required $/yr-kW vs. h/yr) for the three types of power plants (like Figure 1.29). b. For a least-cost system, what is the maximum number of hours a CT should operate, the minimum number of hours the coal plant should operate, and the range of hours the NGCC plants should operate. You can do this algebraically or graphically. c. How many MW of each type of power plant would you recommend? FIGURE 1.29 A graphical presentation of Examples 1.2 and 1.3. The average cost of electricity is the slope of a line drawn from the origin to the revenue curve that corresponds to the capacity factor. Capacity factor 0.0 0.2 0.4 0.6 9,8 1.0 800 - CF = 0.7 Z 600 Fixed costs $218/yr-kW Total costs line Revenue required ($/yr-kW) 400- $579/yr-kW 200 Slope = 579 / 6132 = $0.1017/kWh 0.7 x 8760 = 6132 hrs/yr 04 0 8760 2000 4000 6000 8000 Equivalent hours per year at rated power 1.6.3 Screening Curves Some technologies, such as coal and nuclear plants, tend to be expensive to build and cheap to operate, so they make sense only if they run most of the time. Others, such as combustion turbine (CT), are just the oppositecheap to build and expensive to operate, so they are better suited as peakers. An economically efficient power system will include a mix of power plant types appropriate to the amount of time those plants actually are in operation. 1.14 The following table gives capital costs and variable costs for coal plants, NGCC plants, and natural-gas-fired CTs. Coal NGCC CT Capital cost ($/kW) 2000 1200 800 Variable cost (/kWh) 2.0 4.0 6.0 This is a municipal utility with a low fixed charge rate of 0.10/yr for capital costs. Its load duration curve is shown below. 62 1000 900 Demand (MW) 800 700 600 500 400 300 200 100 0 0 1000 2000 3000 6000 7000 8000 9000 4000 5000 Hours/year FIGURE P1.14 a. On a single graph, draw the screening curves (Revenue required $/yr-kW vs. h/yr) for the three types of power plants (like Figure 1.29). b. For a least-cost system, what is the maximum number of hours a CT should operate, the minimum number of hours the coal plant should operate, and the range of hours the NGCC plants should operate. You can do this algebraically or graphically. c. How many MW of each type of power plant would you recommend? FIGURE 1.29 A graphical presentation of Examples 1.2 and 1.3. The average cost of electricity is the slope of a line drawn from the origin to the revenue curve that corresponds to the capacity factor. Capacity factor 0.0 0.2 0.4 0.6 9,8 1.0 800 - CF = 0.7 Z 600 Fixed costs $218/yr-kW Total costs line Revenue required ($/yr-kW) 400- $579/yr-kW 200 Slope = 579 / 6132 = $0.1017/kWh 0.7 x 8760 = 6132 hrs/yr 04 0 8760 2000 4000 6000 8000 Equivalent hours per year at rated power 1.6.3 Screening Curves Some technologies, such as coal and nuclear plants, tend to be expensive to build and cheap to operate, so they make sense only if they run most of the time. Others, such as combustion turbine (CT), are just the oppositecheap to build and expensive to operate, so they are better suited as peakers. An economically efficient power system will include a mix of power plant types appropriate to the amount of time those plants actually are in operation
