EN642/EN302: Power Generation and Systems Planning Assignment-2: Load Curve & Power Generation

1. A 120 MW power plant supplies following power to the consumers, with a connected load of 150

MW. Determine: average load, load factor, capacity factor, utilization factor, and demand factor. Draw the load curve and the load duration curve.

Time (h) 0-6 6-10 10-12 12-16 16-20 20-22 22-24

Load (MW) 30 70 90 60 100 80 50

2. Load data for a small isolated village is as follows. (a) A diesel generator without any storage is

planned to supply the demand. Determine its minimum capacity in kW. Determine average load,

and capacity factor. (b) An independent agency has suggested installing a diesel generator with a

capacity of 40 kW. However, the generator cannot run less than 40% of its rated capacity.

Determine the amount of energy to be dumped.

Time (h) 10-14 14-18 18-22 22-2 2-6 6-10

Load (kW) 20 12 35 10 8.5 12.5

3. A simple closed cycle gas turbine power plant runs on a novel non-ideal gas. However, it is known

that the specific heat of the novel gas is constant. The gas turbine cycle can withstand a maximum and a minimum temperatures of T1 and T2, respectively. (a) Draw the T-s and process flow diagrams of the cycle. Assuming the cycle to be internally reversible, determine (b) the maximum specific power developed by the cycle and (c) the efficiency at maximum power.

4. (a) A simple steam power plant is to be designed with the turbine inlet pressure of 80 bar and the

turbine exhaust temperature is 40 °C. After expansion of steam in the turbine, the moisture content at the turbine exhaust is not to exceed 15%. Assuming an ideal cycle, determine the allowable steam temperature (in °C) at the turbine inlet. Is it the maximum or the minimum allowable temperature? (b) For the condition derived in (a), calculate the cycle efficiency, without neglecting the pump work, for a simple ideal cycle. (c) For the condition derived in (a), and assuming non-ideal cycle with valid Salisbury approximation, determine the cycle efficiency and exhaust dryness fraction, without neglecting the pump work.

5. In a nuclear plant, dry saturated steam at 80 bar is supplied to the turbine. During expansion, the steam is removed completely from the turbine (at 10 bar), the water is separated in a separator, and dry saturated steam is fed back into the turbine. Condenser pressure is 0.075 bar. Isentropic efficiency of the turbine is 0.8. The water separated in the separator is discharged into the condenser. (a) Sketch the block diagram and T-s diagram of the cycle. (b) Determine all the state points (temperature, pressure, enthalpy, and entropy). (c) Determine specific heat input, net work output and efficiency of the cycle.

6. A textile plant requires 20 t/h of saturated steam at 5 bar and 2 MW of electrical power, using a back-pressure turbine with 65% isentropic efficiency and an electrical generator of 95% efficiency. Neglecting pump work, find the steam condition required at the inlet of the turbine.

7. Two endoreversible continuous Carnot heat engines are operated in series. The topping engine receives heat from a hot reservoir at temperature, Tmax and the bottoming engine rejects heat to a thermal reservoir at temperature, Tmin. Assume the overall heat transfer coefficient for all the heat exchangers is U. (a) Find the efficiency of the combined cycle at maximum power generation. (b) If the total heat transfer area available is A, find the distribution of the total heat transfer area among different heat exchangers that maximizes the power production.

8. (a) A simple steam power plant is to be designed with the turbine inlet temperature of 500°C and the turbine exhaust temperature of 40°C. After expansion of steam in the turbine, the moisture content at the turbine exhaust is not to exceed 15%. Assuming an ideal cycle, determine the allowable steam pressure (in bar) at the turbine inlet. Discuss whether it is the maximum or the minimum allowable pressure. Justify your answer. (b) Calculate the cycle efficiency and steam rate, without neglecting the pump work, for a simple Rankine cycle. The turbine inlet temperature and pressure are 550°C and 70bar, respectively. The turbine exhaust temperature and isentropic efficiency are 40°C and 0.85, respectively.

9. A gas turbine power plant consists of a regenerator. Air enters the compressor at 1 bar, 30°C. The maximum temperature of the cycle is limited to 1200°C and the maximum pressure ratio is 6. The effectiveness of the regenerator is 0.75. The rate of air flow through the plant is 200 kg/s and the calorific value of the fuel used is 40 MJ/kg. The isentropic efficiency of the compressor is 0.75 and that of the turbine is 0.8, the combustion efficiency is 0.95, the mechanical efficiency is 0.98, and the generator efficiency is 0.9. Take for air cP = 1.005 kJ/kg K and γ = 1.4 and for combustion gases cP = 1.148 kJ/kg K and γ =1.333. Neglecting any heat loss, calculate (a) power required in the compressor, (b) fuel consumption, (c) power produced in the turbine, and (d) net electrical power produced by the plant.

10. 1 MWe (peak) solar thermal power plant is designed and constructed by IIT Bombay at Gurgaon. The plant operates on simple Rankine cycle with turbine inlet of 350°C, 40 bar and condenser pressure of 0.08 bar. Isentropic efficiency of the turbine is 70%. (a) Draw the T-s diagram of the cycle. (b) Determine enthalpy at every state point. (c) Determine the efficiency of the cycle. (d) Suggests two different ways to improve efficiency of the plant and possible reasons for not implementing them in this plant.

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