GEOTHERMAL POWERPLANT

ACTIVITY

Name: ______________________
Student No. __________________

PROBLEM SOLVING
1. A Geothermal energy system consists of a water well, flasher and a 15MW
Turbine power. The pressurized ground water at 17.5Mpa,300 ℃ leaves the well
kj
to enter the flasher maintained at 1.3Mpa ( h f =814.93, h fg =1972.7 ¿ . The flashed
kg
vapor passes through the separator and collector to enter the turbine as
saturated vapor at 1.3Mpa. The turbine exhausts at 1bar. Find the hourly amount
of ground water required in kg.
A. 464,848 kg/hr C. 564,848 kg/hr
B. 484,848 kg/hr D. 664,848 kg/hr

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2. A flashed steam geothermal plant has pressurized underground water available

at 102 kg/cm2 and240 ℃. In order to produce steam water mixture, the ground
water is passed and throttled to 5.4 kg/cm 2in a steam separator. The dry steam
produced in the separator is fed to double flow impulse and reaction turbine with
guaranteed engine efficiency of 85%. The turbine is directly coupled to a 3
phase, 60HZ, 80% power factor, 13800V air cooled generator . Exhaust is to be
direct contact spray type main condenser designed to operate a vacuum of
647.5mmhg. Generator Efficiency is 95%, ground water is 459 kg/s. What is the
enthalpy of steam water mixture in the steam separator?
A. 1038.10 kJ/kg C. 1543.25 kJ/kg
B. 1245.78 kJ/kg D. 1052.35 kJ/kg

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3. Based on the data in Problem No. 2, What is the enthalpy of steam entering the
turbine.
A. 2876.68 kJ/kg C. 2751.3 kJ/kg
B. 1874.67 kJ/kg D. 3574.4 kJ/kg

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4. Based on the data in Problem No. 2, What is the enthalpy of the Exhaust steam.
A. 2876.68 kJ/kg C. 2751.37 kJ/kg
B. 1874.67 kJ/kg D. 2204.15 kJ/kg

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5. Based on the data in Problem No. 2, What is the mass flow rate of the steam
entering the turbine?
A. 84.88 kg/s C. 94.88 kg/s
B. 74.88 kg/s D. 104.88 kg/s

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6. Based on the data in Problem No. 2, What is the actual power generated by the
plant in MW?
A. 37.50 MW C. 35.40 MW
B. 27.50 MW D. 25.40 MW

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7. Based on the data in Problem No. 2, What is the apparent power developed by
the generator in KVA?
A. 43,576.687 kVA C. 45,275.375 kVA
B. 51,874.678 kVA D. 46,877.475 Kva

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8. Based on the data in Problem No. 2, how many cubic meter per hour of fresh
water that must be supplied to the main condenser if water from cooling tower
enters the condenser at 35 ℃ and leaves at 48 ℃ ?
m3 m3
A. 11,105.393 C. 22,751.377
hr hr
3
m m3
B. 12,874.677 D. 21,204.158
hr hr

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9. Based on the data in Problem No. 2, how many production wells are needed to
supply the plant with pressurized water if each well has a capacity of 127,200
kg/hr?
A. 13 wells C. 12 wells
B. 14 wells D. 10 wells

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10. Based on the data in Problem No. 2, determine the thermal efficiency of the
geothermal power plant?
A. 9.88% C. 8.69%
B. 9.57% D. 7.86%

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11. In a Geothermal power plant, the mass flow rate of the ground water is 400 kg/s
and the quality after throttling is 20%. If the turbine power is 80MW, what is the
change in enthalpy of steam at the inlet and outlet of the turbine?
A. 1000 kJ/kg C. 2000 kJ/kg
B. 1500 kJ/kg D. 2500 kJ/kg

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12. The mass flow rate of ground water in a 20MW geothermal power plant is 150
kg/s and its enthalpy is 1000 kJ/kg. If the quality after throttling is 28% and the
over-all plant efficiency is 20%, what is the mass flow rate of the steam entering
the turbine?
A. 28 kg/s C. 18 kg/s
B. 76 kg/s D. 24 kg/s

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13. The turbine power of a geothermal power plant is 2MW and the enthalpy at the
inlet of the turbine is 2500 kJ/kg. Steam flows at the rate of 2.5 kg/s. If the
enthalpy at the outlet of the condenser is 300 kJ/kg and the temperature rise of
the cooling water is 10 ℃, what is the volume flow rate of the cooling water?
A. 109.37 m3/hr C. 300.924 m3/hr
B. 237.68 m3/hr D. 320.47 m3/hr

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14. In a Geothermal power plant, the enthalpies of the ground water and the turbine
inlet are 1500 kJ/kg and 3500 kJ/kg respectively. If the enthalpy of the hot water
in the flash tank is 700 kJ/kg and the mass flow rate of steam is 15 kg/s, what is
the mass flow rate of the ground water?
A. 52.50 kg/s C. 55.49 kg/s
B. 48.69 kg/s D. 345.48 kg/s

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15. A flashed steam geothermal power plant is located where underground hot water
is available as saturated liquid at 700 kpa. The well head pressure is 600 kpa.
The flashed steam enters a turbine at 500 kpa and expands to 15 kpa, when it is
condensed. The flow rate from the well is 29.6 kg/s. Determine the power
produced in KW.
A. 453.16 kW C. 254.25 kW
B. 540.36 kW D. 430.16 kW

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16. In a certain geothermal area, studies show that 1,500,000 kg/hr of pressurized
ground water is available at 2,500 psia and 620°F. The water will be throttled to
250 psia to produce wet steam and this mixture will be passed through a water
separator to remove the water droplets so that saturated steam at 250 psia is
available at the entrance of steam turbine for the proposed power plant. Other
power plant data are as follows:
Discharge pressure of turbine = 25 in Hg vacuum
Turbine engine efficiency = 75%
Mechanical Loss = 1.5% of shaft power
Generator Efficiency = 97%
Assume atmospheric pressure to be 30 in Hg. Determine the maximum amount
of power in Kilowatts that the plant can generate. (ME Bd. Oct. 1981)
A. 60 MW B. 68 MW C. 66 MW D. 74 MW

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17. A liquid dominated geothermal plant with a single flash separator receives water
at 204°C. The separator pressure is 1.04 MPa. A direct contact condenser
operates at 0.034 MPa. The turbine has a polytropic efficiency of 0.75. For a
cycle output of 50 MW, what is the mass flow rate of the well-water in kg/s? (ME
Bd. Oct. 1995)
A. 2871 B. 2100 C. 186 D. 2444

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18. A certain geothermal power plant shows that 1,700,000 kg/hr of pressurized
ground water is available at 17.5MPA and 330deg.C. The water will be throttled
to a pressure of 1.7Mpa to produce wet steam and this mixture will be passed
through a water separator to remove the water droplets so that saturated steam
at 1.7Mpa is available at the entrance of the turbine. Other data are as follows.
Discharge pressure turbine = 85kpa Vac
Turbine Efficiency = 73%
Mechanical loss = 2% of shaft power
Generator Efficiency = 95%
Determine the mass flow rate of steam entering the turbine.
A. 401,000 kg/hr C. 501,000 kg/hr
B. 461,000 kg/hr D. 561,000 kg/hr

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19. In problem no. 18, Determine the maximum amount of power in KW that the plant
can generate.
A. 66,858 KW C. 86,858 KW
B. 76,858 KW D. 96,858 KW

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20. A single-flash geothermal power plant uses hot geothermal water at 230ºC as the
heat source. The mass flow rate of steam through the turbine, the isentropic
efficiency of the turbine, the power output from the turbine, and the thermal
efficiency of the plant are to be determined.

Assumptions:
1. Steady operating conditions exist.
2. Kinetic and potential energy changes are negligible.

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21. In a geothermal power plant, the mass flow rate of ground water is 400 kg/s and
the quality after throttling is 20%. If the turbine power is 80 MW, what is the
change in enthalpy of steam at the inlet and outlet of the turbine?
a. 1000 kJ/kg b. 1500 kJ/kg c. 2000 kJ/kg d. 2500 kJ/kg

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22. The mass flow rate of ground water in a 20 MW geothermal power plant is 150
kg/s and its enthalpy is 1000 kJ/kg. If the quality after throttling is 28% and the
over-all plant efficiency is 20%, what is he mass flow rate of steam entering the
turbine?
a. 28 kg/s b. 76 kg/s c. 18 kg/s d. 24 kg/s

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23. In a geothermal power plant, the enthalpies of the ground water and the turbine
inlet are 1500 kJ/kg and 3500 kJ/kg respectively. If the enthalpy of the hot water
in the flash tank is 700 kJ/kg and the mass flow rate of steam is 15 kg/s, what is
the mass flow rate of ground water?
a. 52.50 kg/s b. 48.69 kg/s c. 55.49 kg/s d. 345.48 kg/s

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24. A double-flash geothermal power plant uses hot geothermal water at 230 deg C
as the heat source. The temperature of the steam at the exit of the second flash
chamber, the power produced from the second turbine, and the thermal
efficiency of the plant are to be determined?

Assumptions:
1. Steady operating conditions exist.
2. Kinetic and potential energy changes are negligible.

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25. A combined-flash binary geothermal power plant uses hot geothermal water at
230 deg C as the heat source. The mass flow rate of isobutane in the binary
cycle, the net power outputs from the steam turbine and the binary cycle, and the
thermal efficiencies for the binary cycle and the combined plant are to be
determined.

Assumptions:
1. Steady operating conditions exist.
2. Kinetic and potential energy changes are negligible.

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26. Mass flow rate of ground water in a geothermal power plant is 1,500,000 kg/hr
and the quality after throttling is 30%. Determine the brake power of turbine if the
change of enthalpy of steam at inlet and outlet is 700 kJ/kg.
A. 68.5 MW B. 87.5 MW C. 64.5 MW D. 89.5 MW

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27. The enthalpy entering the turbine of a geothermal power plant is 2750 kJ/kg and
mass rate of 1 kg/sec. The turbine brake power is 1000 KW condenser outlet has
enthalpy of 210 kJ/kg. If temperature rise of cooling water in condenser is 8°C,
what is the mass of cooling water requirement?
A. 44 kg/sec B. 45 kg/sec C. 46 kg/sec D. 47 kg/sec

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28. In a 12 MW geothermal power plant, the mass flow of steam entering the turbine
is 26 kg/sec. The quality after throttling is 25% and enthalpy of ground water is
750 kJ/kg. Determine the overall efficiency of the plant.
A. 7.4% B. 9.6% C. 5.4% D. 15.4%

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29. In a Geothermal power plant, the mass flow rate of the ground water is 400 kg/s
and the quality after throttling is 20%. If the turbine power is 80MW, what is the
change in enthalpy of steam at the inlet and outlet of the turbine?
C. 1000 kJ/kg C. 2000 kJ/kg
D. 1500 kJ/kg D. 2500 kJ/kg

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30. The turbine power of a geothermal power plant is 2MW and the enthalpy at the
inlet of the turbine is 2500 kJ/kg. Steam flows at the rate of 2.5 kg/s. If the
enthalpy at the outlet of the condenser is 300 kJ/kg and the temperature rise of
the cooling water is 10 ℃, what is the volume flow rate of the cooling water?
C. 109.37 m3/hr C. 300.924 m3/hr
D. 237.68 m3/hr D. 320.47 m3/hr

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