Study Unit 2

Question 1

How is a turbine used to generate electricity?

Answer 1

1. 400psi motive steam enters through a governor speed control valve. The governor valve controls the flow of steam into the steam chest.
   The steam’s pressure drops by 100psi in the governor due to friction in the valve (isoenthalpic expansion).
   2.The 300psi steam passes through a steam nozzle.
   The nozzle is shaped to convert the steam to velocity. When the steam escapes from the nozzle it has a pressure of 100psi (exhaust steam pressure). (200psi loss is called isoentropic expansion).
2. The high velocity steam pushes the bucket around the rim of turbine wheel which transfers the steam’s velocity to the spinning turbine wheel.
3. If the turbine is spinning too slow, the speed controller opens the governor control valve to allow more steam to enter.
4. If the turbine is spinning too fast the speed controller closes the governor control valve.

Question 2

What are the basic components present in a thermal power plant?

Answer 2

Boiler
Pump
Turbine
Condenser
Rotating shaft
Synchronous generator
Cooling tower

Question 3

How is nuclear power generated?

Answer 3

Uranium nucleus is excited by the capture of a neutron causing it to split into two nuclei, krypton and barium, releasing 3 neutrons.

Question 4

How is geothermal power generated?

Answer 4

Geothermal power plants use steam to produce electricity. The steam comes from reservoirs of hot water found a few miles or more below the earth’s surface. The steam rotates a turbine that activates a generator, which produces electricity.

Question 5

How is solar power generated?

Answer 5

Solar Photovoltaic (PV) cells generate electricity by absorbing sunlight and using that light energy to create an electrical current.

Question 6

Isoenthalpic expansions

Answer 6

Heat content of the steam in a turbine has been preserved during reduction in pressure in the steam chest.
Irreversible. The ability of the steam to do work has been reduced.

Question 7

Isoentropic expansion

Answer 7

Entropy of the steam does not increase.

Reversible and frictionless. The ability of the steam to do work has not been reduced.