Hydroelectric

Question 1

What is hydroelectric energy?

Answer 1

A clean, renewable, and consistent source of electricity generation that uses the natural flow(kinetic energy) of water downhill(potential energy) to turn a water turbine connecting to an electricity generator and then convert to electric energy. Therefore, it is often placed along heavy water currents such as waterfalls or rivers

Question 2

what are the 3 steps listed for a hydroelectric power plant to generate electricity

Answer 2

1. convert water from the intake to the power house
2. Flowing water drive the turbine to rotate, convert the waters kinetic energy into mechanical energy
3. The mechanical energy then is converted into electric energy through generator

Question 3

What are the components in hydroelectric

Answer 3

Reservoir,
trash rack
control gate
Intake
penstock
draft tube
turbine
generator
powerhouse
transformer
outflow
spillway

Question 4

What are the types of hydropower systems

Answer 4

Storage systems
run-of-the-river systems
pumped-storage systems

Question 5

What is the capacity range of hydroelectric installations

Answer 5

few hundred watts to more than 10 GW

Question 6

Describe the storage system

Answer 6

typically a dam to create a reservoir that releases
water through turbines; the system can be shut down and started up
at short notice according the demands of the system (peak load)

Question 7

describe the run-of-the-river system

Answer 7

a river’s current go through a canal or
penstock to spin a turbine, typically provides continuous supply of
electricity (base load) without storage facility

Question 8

describe the pumped storage system

Answer 8

water is pumped to a reservoir at a higher
elevation using energy produced from solar, wind, and nuclear.

Question 9

Which hydroelectric system provides peak load and which one provides base load

Answer 9

Peak load: storage systems
base load: Run-of-the-river systems

Question 10

what is considered as low head medium head, and high head for a hydroelectric system

Answer 10

low head < 10m - run-of-the-river
medium head 10-100m
high head > 100m smaller turbine but larger penstock

Question 11

what are the advantages of hydroelectric energy

Answer 11

• Zero air pollutants during operation, ultra low life-cycle
  greenhouse gas emissions.
• The ONLY abundant form of renewable, flexible baseload
  electricity generation with long-duration energy storage.
• Commonly 100+ years of facility life.
• Converts over 90% of available renewable energy from
  water into electricity. Hydropower is the most efficient
  source of electrical energy. By comparison, the best fossil
  fuel power plants operate at approximately 60% efficiency.
• It can prevent floods and facilitate irrigation by storing
  water at upstream reservoir at flood season and release it
  during dry season

Question 12

what are the disadvantages of hydroelectric energy

Answer 12

• Very high up-front project costs
• Environmental damage/disturbance
• Disruption of the aquatic eco-systems
• Suffer from drought seasons ‒ global warming!
• Hydro projects must be sited where the hydrology is feasible, and
  this may be unattractive from the perspective of transmission
  access and proximity to major load needs
• People living in the area are displaced
• Dam failure can be catastrophical

Question 13

What is the worlds largest power station

Answer 13

three gorges dam - 22,500MW

Question 14

what is Canadas largest hydroelectric power station

Answer 14

Robert-Bourassa - 7,722 MW

Question 15

What is spillway

Answer 15

Passages built besides the dam as part of structure that accommodate high flood that exceed normal flow conditions in the river

Question 16

what is the cost advantage of hydroelectric energy

Answer 16

provinces who have the greatest access to hydropower also tend to pay the least for their electricity

Question 17

Define mechanical energy

Answer 17

form of energy that can be converted to mechanical work completely and directly by an ideal mechanical device such as an ideal turbine

Question 18

What does it mean when the change in mechanical energy is greater than 0

Answer 18

mechanical work supplied to the fluid by increasing the pressure, velocity and/or elevation of a fluid with a pump, fan or a compressor

Question 19

what does it mean when the change in mechanical energy is less than 0

Answer 19

mechanical work extracted from the fluid by a turbine to rotate the shaft that can drive a generator or any other rotary device

Question 20

What is the equation for mechanical energy of a flowing fluid per unit mass

Answer 20

e mech = P/p + V^2/2 + gz

Question 21

In this equation, what does each term represent? e mech = P/p + V^2/2 + gz

Answer 21

P/p = flow energy
V^2/2 = kinetic energy
gz = potential energy

Question 22

what is the equation for the change in mechanical energy

Answer 22

△e mech = △P/p + △V^2 /2 + g△z

Question 23

the maximum ideal power generated by a water turbine is

Answer 23

W.max = m. △e mech
where m. is the mass flow rate of the fluid

Question 24

what is the maximum power generated by a water turbine when we consider the point 1. surface of the water reservoir and 2. surface of discharge water from the turbine

Answer 24

W. max = m.△e mech = m.g △z = m.gh
P1= P4 = Pat,
V1=V2 = 0

Question 25

what is the maximum power generated by a water turbine when we consider the point 1. turbine inlet and 2. turbine outlet

Answer 25

W.max = m. △e mech = m. △P/p V2 = V3 z2 = z3

Question 26

define turbine efficiency - hydro

Answer 26

quantifies degree of perfection of the conversion process between the mechanical work extracted and the mechanical energy change

Question 27

what is the equation for turbine efficiency - hydro

Answer 27

n turbine = W.shaft/ △E. mech,fluid = W.shaft/W.max

Question 28

how can we approach 100% efficiency for a hydro turbine

Answer 28

frictional effects are minimized

Question 29

what is the equation for generator efficiency - hydro

Answer 29

n generator = W.electric/ W.shaft

Question 30

what is the combined/overall efficiency of turbine-generator in hydro

Answer 30

n turbine and generator = n turbine * n generator = W. electric / W. max

Question 31

what is the average efficiency of hydro turbines

Answer 31

about 90% larger hydro turbines can achieves efficiency's above 95%

Question 32

describe the impulse turbine

Answer 32

uses the velocity of the water to drive the runner and discharges at atmospheric pressure. Water stream hits each bucket on the runner and flows out the bottom of the turbine housing. An impulse turbine is generally suitable for high head(300-4000m), low flow application

Question 33

what types of turbines are impulse turbines

Answer 33

Pelton cross flow turbine - water to flow through the blades twice

Question 34

describe the reaction turbine

Answer 34

generates power from the combined forces of pressure and moving water. A runner is immersed in the water stream, allowing water to flow through and create pressure difference between two sides of the blade. Its generally used for sites with lower head(2-25m) and higher flows (70-800m^3/s)

Question 35

what is adjustable on the kaplan turbine that allows it for a wider range of operation

Answer 35

wicket gates and blades

Question 36

what are the types of reaction turbines

Answer 36

Kaplan turbine and Francis turbine

Question 37

A water turbine is a _____ machine that convers _____ energy and ______ energy of water into ________ work

Answer 37

rotary kinetic potential mechanical

Question 38

In an impulse turbine, the fluid is sent through a _______ so that most of its available _______ energy is converted into ________ energy of the turbine

Answer 38

nozzle mechanical kinetic

Question 39

how do we increase the velocity of the jets for a impulse turbine

Answer 39

jets increase the velocity of the flowing water (kinetic energy) by restricting the area which the water moves through

Question 40

The buckets of a ________ turbine split the incoming fluid flow in ____, and turn the flow nearly ____ around. In this way, the maximum amount of ________ from the jet is utilized

Answer 40

Pelton half 180 degrees momentum

Question 41

there are 2 main types of reaction turbines - francis and kaplan, based on the ______ that the flow enters into the runner

Answer 41

angle

Question 42

Francis: has a runner with ____ blades, usually ____ or more; water is introduced just above the falls through causing _______________

Answer 42

fixed 16 the blades to spin

Question 43

________ suits medium to high head situations, which lies between the high heads of ________ wheel turn=bines and the low heads of _______ turbines

Answer 43

francis pelton kaplan

Question 44

What are the 2 types of flow for francis

Answer 44

francis radial flow francis mixed flow

Question 45

describe francis radial flow

Answer 45

the flow enters the runner radially and discharges axially

Question 46

describe the the francis mixed flow

Answer 46

the flow enters the runner at some angle between radial and axial

Question 47

describe the spiral case for the francis turbine

Answer 47

the spiral casing is the inlet medium of water to the turbine. The water flowing from the reservoir or dam is made to pass through this pipe with high pressure

Question 48

what is the stay ring for the francis turbine

Answer 48

stay vanes remain stationary at their position and reduces the swirling of water due to radial flow, as it enters the runner blades, thus, making the turbine more efficient

Question 49

what is the guide vane for the francis turbine

Answer 49

guide vanes change their angle as per the requirement to control the angle of striking of water to turbine blades to increases the efficiency. They also regulate the flow rate of water into the runner blades thus controlling the power output of the turbine

Question 50

What is the runner blades for the francis turbine

Answer 50

runner blades are the heart of any francis turbine. These are the centers where the fluid strikes and the tangential forces of the impact causes the shaft of the turbine to rotate, producing torque

Question 51

what are all the parts of the francis turbine

Answer 51

Guide vane stay ring spiral case runner blades head cover water inlet main shaft operating ring water guiding device guide vane runner draft tube

Question 52

What are the two types of flow for kaplan

Answer 52

Propeller mixed flow and axial flow

Question 53

what is kaplan propeller mixed flow

Answer 53

if the runner has no band, and flow enters the runner partially turned

Question 54

what is the kaplan axial flow

Answer 54

the flow is turned completely axially before entering the runner. flow rate is controlled by blades and wicket gates

Question 55

the wicket gates are adjustable to...

Answer 55

control the volume floe rate through the runner

Question 56

flow rate is

Answer 56

the volume of fluid that passes a point per unit time

Question 57

what type of hydro turbine is commonly used for run of the river

Answer 57

The kaplan because it works for high velocity, low elevation, and where the water flow varies