Transcript Water Power

Do Now:
What are the 4 steps of the Water Cycle?
 What is the difference between
transcription and evaporation?


The Water Cycle
Evaporation & Transpiration
2. Condensation
3. Precipitation
4. Infiltration, Storage & Runoff
1.
The Parts of a
Hydroelectric Plant
Essential Questions
How is moving water an energy source?
 How can flowing water do work?
 What is hydropower’s potential?

The Water Cycle
The Water Cycle ensures that water flows from
mountain peaks, down rivers and streams back
into the ocean. That continuous flow of water
carries with it a large amount of kinetic energy.
…kinetic energy that can be
transformed into electrical
energy, with the aid of
hydroelectric power plants,
to power our homes and
businesses!
Hydroelectric Power Plants
Water enters hydroelectric plants from a
river or reservoir; each plant has essentially
8 different elements:
1.
2.
3.
4.
5.
6.
7.
8.
Reservoir
Penstock
Turbine Blades & Shaft
Generator
Step-up Transformer
Transmission Lines
Tailrace
Dam & Spillway
Reservoir

The reservoir for a hydroelectric plant is
a man-made lake/pond where water
stored so that it backs up behind a dam;
the height of such a mass of water is a
way of storing gravitational potential
energy.
Penstock

Penstock is the pipe that channels water
from the reservoir to the blades of the
turbine. As the water moves through the
penstock, its potential energy is
transformed into kinetic energy.
Turbine Blades & Shaft

The turbine blades transform the
kinetic energy of the water into
mechanical energy which the shaft
transmits on to the generator.
Generator

The generator transforms the
mechanical energy transmitted from the
turbine blades into electricity, into
electrical energy.
Step-up Transformer

The step-up transformer increases the
voltage of the electrical current generated
so that it can be transmitted long
distances more efficiently.
Dam & Spillway

A Dam is a barrier that blocks the
regular flow of a river or stream, causing
the water to back up behind it.

Spillways are holes in the dam that can
be opened to allow water to flow past
the dam to prevent water from
overflowing the dam.
Types of Hydroelectric Plants

There are 3 main types of hydroelectric
plants:
3.
1.
2. Run-of-River
Traditional
Pumped Storage
Hydro Turbines:
Power & Efficiency
The Potential Energy of Reservoirs
The amount
Dams
force water
of energy
to back
stored
up behind
is proportional
them into
to
reservoirs
the
head –which
the height
store of
thewater
gravitational
in the reservoir
potential
energythe
above
of water.
turbine. The stored energy can be used
to generate power.
head,
h
Volumetric Flow Rate

Volume Flow Rate Through a Pipe
Example:
Water
flows
at a rate
of 1
In this case,
the
pipe
we’re
m/s through a round pipe with a
talking
about
is theis the
diameter of
3 cm. What
volumetric
ratechannels
[L/s]?
penstockflow
that
water from the reservoir
to the turbines where
power is transmitted to
Q =the
AVgenerators.
Q, volumetric flow rate
A, cross-sectional area
V, average fluid velocity
How much power does a hydro
turbine produce?
Power = hrghQ
h, efficiency
r, density
Q,
g,
h,
acceleration of gravity
head
volume flow rate
Example: A hydroelectric plant employs a turbine with an overall
efficiency of 85% in conditions where the flow rate is 30000 liters per
second and the surface of the reservoir is 20m above the turbine.
How much power is produced [kW]?
Power, Head & Flow Rate
Large h
Small Q
Average h
Average Q
Small h
Large Q
Thiswe
As
image
means
follow
shows
that,
theinrun-off
atheory,
cross-section
from
it would
A toofC,
be
surface
the
possible
vertical
run-off
to drop
achieve
at of
three
the
water
same
separate
power
flow locations:
decreases
when installing
(A)
(h goes
a small,
a down),
hydroelectric
fast-flowing,
but thepower
steep
mountain
volumetric
plant
at any
stream;
flow
of the
rate
(B)
three
increases
a deep,
locations
quick
(Q goes
shown.
flowing
up).river in a
narrow channel; and (C) a very wide, but shallow, slowmoving river.
Types of Turbines

Impulse
◦ Pelton Wheel - large h, small Q

Reaction
◦ Kaplan - small h, large Q
◦ Francis - large h, large Q
Pelton Wheel
Kaplan
Francis
Choosing Turbines
Which type of turbine would
you choose if you were
designing a hydroelectric power
plant for a site similar to the
conditions at location C? Why?
What’s Coming Up?

Impacts on Environment/Society
Homework Due
Tomorrow
Homework 3 Water Flow