(SEM VII) THEORY EXAMINATION 2022-23 POWER PLANT ENGINEERING

SECTION A – Short Answers (2 Marks Each)

(a) Conventional vs Non-conventional power plants

Conventional power plants use exhaustible energy sources such as coal, oil, gas, and nuclear fuel, whereas non-conventional power plants use renewable sources like solar, wind, tidal, geothermal, and biomass energy.

(b) Function of cooling tower

A cooling tower removes excess heat from circulating water used in condensers by evaporative cooling, allowing water to be reused in the power plant.

(c) Specific speed of hydraulic turbine

Specific speed is the speed of a turbine that would produce unit power under unit head. It helps in selecting the suitable turbine type for given conditions.

(d) Function of reheater in gas turbine power plant

A reheater reheats the partially expanded gases before further expansion, increasing work output and improving thermal efficiency.

(e) Fission vs fusion reaction

Fission involves splitting of heavy nucleus like Uranium-235 releasing energy, while fusion involves combining light nuclei like hydrogen to form helium, releasing much larger energy.

(f) Function of solar thermal collector

A solar thermal collector absorbs solar radiation and converts it into heat energy, which is used to generate steam or hot water for power generation.

(g) Tidal energy vs ocean thermal energy

Tidal energy uses rise and fall of sea tides, while ocean thermal energy uses temperature difference between surface and deep ocean water.

(h) Principle of fuel cell

A fuel cell converts chemical energy of fuel directly into electrical energy through electrochemical reactions without combustion.

(i) Depreciation

Depreciation is the reduction in value of power plant equipment over time due to wear, aging, and obsolescence.

(j) Function of bus bar

A bus bar is a conductor that collects electrical power from generators and distributes it to outgoing feeders.

SECTION B – Long Answers (10 Marks Each)

(a) Modified Rankine Cycle

The modified Rankine cycle improves efficiency by incorporating superheating, reheating, and regenerative feed water heating. Steam expands in turbine, is reheated, and condensed. Feed water heaters reduce boiler heat requirement.
(T-s diagram explanation expected in exam.)

(b) Constant pressure open cycle gas turbine (Numerical – Method)

Given inlet and outlet pressures, compressor and turbine efficiencies, temperatures, and plant power output:

Compressor outlet temperature is calculated

Turbine work and compressor work are determined

Net work output gives air flow rate

Heat supplied per kg of air is calculated

Thermal efficiency = Net work / Heat supplied

(c) Working of BWR and comparison with PWR

In a Boiling Water Reactor (BWR), water boils directly in reactor core and steam drives turbine.
PWR (Pressurized Water Reactor) uses pressurized water to avoid boiling and transfers heat through steam generator.
BWR is simpler, while PWR offers better safety and control.

(d) Components of wind turbine

Main components include rotor blades, hub, nacelle, gearbox, generator, yaw system, tower, and controller. Blades capture wind energy and convert it into mechanical energy which drives generator.

(e) Power plant performance (Numerical – Method)

Given maximum demand, load factor, capacity factor, and use factor:

Reserve capacity = Installed capacity – Maximum demand

Daily energy = Maximum demand × Load factor × 24

Maximum possible energy = Installed capacity × Use factor × 24

SECTION C – Long Answers (10 Marks Each)

3(a) Energy sources for power plants

Power plants operate on coal, oil, gas, nuclear fuel, solar energy, wind energy, hydro energy, geothermal energy, tidal energy, and biomass. Each source differs in availability, efficiency, cost, and environmental impact.

3(b) Velox boiler & Fluidized Bed Combustion

Velox boiler uses high-velocity combustion gases to enhance heat transfer.
Fluidized bed combustion burns fuel in a bed of hot particles suspended by air, offering high efficiency and low pollution.

4(a) Hydro electric power plant arrangement

Major components include dam, reservoir, penstock, turbine, generator, draft tube, and tail race. Water energy is converted into mechanical and then electrical energy.

4(b) Layout of modern gas power plant

It consists of air compressor, combustion chamber, gas turbine, generator, heat recovery system, and exhaust. Each component plays a role in efficient power generation.

5(a) CANDU reactor & neutron comparison

CANDU uses heavy water as moderator and coolant.
Thermal neutrons are slow and effective for fission, while un-moderated neutrons are fast and less effective.

5(b) Solar cell & PV power system

Solar cell converts sunlight into electricity using photovoltaic effect.
PV system includes panels, charge controller, battery, inverter, and load.

6(a) Geothermal power plant

Heat from earth’s interior produces steam to run turbine.
Advantages: renewable, low emissions.
Drawbacks: location specific, high initial cost.

6(b) Bio-energy conversion & biogas plant

Bio-energy is converted using combustion, gasification, and anaerobic digestion.
Biogas plant produces methane gas used for power generation.

7(a) Economics of power generation

Factors include capital cost, fuel cost, operation & maintenance cost, depreciation, interest, and load factor.

7(b) Power plant pollution & control

Pollution includes air, water, thermal, and noise pollution.
Control measures include electrostatic precipitators, scrubbers, cooling towers, and waste management.