Economic of power generation 4

Question =  A generating Plant has a maximum capacity of 100 kW and cost RS 1,60,000 . The annual fixed charges are 12% consisting of 5% intererst , 5% depreciation and 2% taxes . Find the fixed charges per kWh if the load factor is (1) 100% (2) 50% . 

Solution = (1) load factor is 100% , 

» fixed charges per kWh = annual fixed charge ÷ unit generated per annum , 

» annual fixed charges = 1,60,000 × RS 0.12 = 19,200 RS , 

» unit generated per annum = maximum demand × L.F. × hours in a years , = 100 kW × 1 × 8760 ,= 8,76,000  kWh , 

» So, fixed charges per kWh = RS 19,200 ÷ 8,76,000 = 0.0219 RS or 2.19 paise , answer ✓ 

(2) load factor is 50% , 

»fixed charges per kWh = annual fixed charge ÷ unit generated per annum , 

» annual fixed charges = 1,60,000 × RS 0.12 = 19,200 RS , 

» unit generated per annum = maximum demand × L.F. × hours in a years , = 100 kW × 0.5 × 8760 , = 4,38,000 kWh , 

» So, fixed charges per kWh = RS 19,200 ÷ 4,38,8000 = RS 0.0438 or 4.38 paise , answer ✓

It is interesting to note that by decreasing the load factor from 100% to 50% , the fixed charges/kWh have increased two fold incidentally , this illustrates the utility of high load factor . 

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