TUTORIAL PROBLEMS-01
1. A generating station has an overall efficiency of 15% and 0·75 kg of coal is burnt per kWh by the station. Determine the calorific value of coal in kilocalories per kilogram. [7644 kcal/kg]
2. A 75 MW steam power station uses coal of calorific value of 6400 kcal/kg. Thermal efficiency of the station is 30% while electrical efficiency is 80%. Calculate the coal consumption per hour when the station is delivering its full output. [42 tons]
3. A 65,000 kW steam power station uses coal of calorific value 15,000 kcal per kg. If the coal consumption per kWh is 0·5 kg and the load factor of the station is 40%, calculate (i) the overall efficiency (ii) coal consumption per day. [(i) 28·7% (ii) 312 tons]
4. A 60 MW steam power station has a thermal efficiency of 30%. If the coal burnt has a calorific value of 6950 kcal/kg, calculate:
(i) the coal consumption per kWh,
(ii)the coal consumption per day. [(i) 0·413 kg (ii) 238 tons]
5. A 25 MVA turbo-alternator is working on full load at a power factor of 0·8 and efficiency of 97%. Find the quantity of cooling air required per minute at full load, assuming that 90% of the total losses are dissipated by the internally circulating air. The inlet air temperature is 20º C and the temperature rise is 30º C. Given that specific heat of air is 0·24 and that 1 kg of air occupies 0·8 m3. [890 m3/minute]
6. A thermal station has an efficiency of 15% and 1·0 kg of coal burnt for every kWh generated. Determine the calorific value of coal. [5733 kcal/kg]
TUTORIAL PROBLEMS-02
1. A hydro-electric station has an average available head of 100 metres and reservoir capacity of 50 million cubic metres. Calculate the total energy in kWh that can be generated, assuming hydraulic efficiency of 85% and electrical efficiency of 90%. [10·423 106 kWh]
2. Calculate the continuous power that will be available from hydroelectric plant having an available head of 300 meters, catchment area of 150 sq. km, annual rainfall 1·25 m and yield factor of 50%. Assume penstock, turbine and generator efficiencies to be 96%, 86% and 97% respectively. If the load factor is 40% what should be the rating of the generators installed? [7065 kW, 17662 kW]
3. A hydroelectric plant has a reservoir of area 2 sq. kilometers and of capacity 5 million cubic meters. The net head of water at the turbine is 50 m. If the efficiencies of turbine and generator are 85% and 95% respectively, calculate the total energy in kWh that can be generated from this station. If a load of 15000 kW has been supplied for 4 hours, find the fall in reservoir. [5·5 105 kWh ; 27·8 cm]
4. It has been estimated that a minimum run-off of approximately 94 m3/sec will be available at a hydraulic project with a head of 39 m. Determine the firm capacity and yearly gross output. [3600 kW, 315·36 106 kWh]
5. A hydroelectric power station is supplied from a reservoir having an area of 50 km2 and a head of 50 m. If overall efficiency of the plant is 60%, find the rate at which the water level will fall when the station is generating 30,000 kW. [7·337 mm/hour]
6. A hydro-electric plant has a catchment are of 120 square km. The available run off is 50% with annual rainfall of 100 cm. A head of 250 m is available on the average. Efficiency of the power plant is 70%. Find (i) average power produced (ii) capacity of the power plant. Assume a load factor of 0.6. [(i) 3266 kW (ii) 5443 kW]
