TOPIC 8: ENERGY, POWER, &
CLIMATE CHANGE
SECTION 8.1 & 8.2
Allen High School
IB Physics SL
Source: Chris Hamper SL Physics
8.1 Energy Degredation &
Power Generation
 We remember that energy cannot be created
or destroyed only transferred by doing either
work or transferring thermal energy (friction).
 The energy that is transferred to its
surroundings (thermal energy) becomes
unavailable to do work. This is Degraded
Energy. This is part of the second law of
Thermodynamics (Entropy).
Examples of Energy Transfer
 Light Bulb
 Converts electrical energy to light + heat
 Motor
 Converts electrical energy mechanical + heat
 Battery
 Converts chemical energy to electrical + heat
 Car Engine
 Converts chemical energy to mechanical + heat
 Solar Cell
 Converts light to electrical + heat
Sankey Diagrams
 Sankey Diagrams are used to visualize the
flow of energy as it changes from one form to
another.
 The thickness of the arrow (band) represents
the proportion of energy of each kind.
 The direction is typically left to right, with
degraded energy angled down .
 Be sure to label the type of energy for each.
Examples of Sankey Diagrams
Power Generation
 The goal: Electricity!
 The “how”: a Generator
 A generator is a device that converts
mechanical energy into electrical energy.
This is what a power plant does.
 By the way, a motor does the opposite; it
converts electrical energy into mechanical
energy (think of a household fan).
E & M
 You previously learned a connection between
electricity and magnetism. This is the
foundation of a generator.
 If a coiled wire is rotated in a magnetic field, a
current is induced in the wire. Sometimes a
side of the wire is moving up and sometimes
down, this is what produces Alternating
Current (AC).
Diagram of a Generator
A basic generator has looped
wire (coil) that is rotated in
between a magnetic field
(present because of an existing
magnet) and as a result, current
is induced in the wire.
The rotation actually can wear
down the wire and thus, many
generators choose to move the
magnet instead of the wire.
(Next Slide)
Foundation of a Generator
 Notice the motion of the magnet, the
direction of current, and meter reading.
8.2 World Energy Sources
 With the knowledge that there is always
some energy degraded, you must have a
source that is sufficient enough to provide
useable energy and the degraded energy.
 The source of energy is called a Fuel. Fuels
release energy by changing its chemical or
nuclear structure.
 There are many different sources of fuel in
the world.
Fuel Sources
 There are two main categories of energy:
Non-Renewable
Coal
Oil & Gas
Wood & Biomass
Nuclear Fuel
Renewable (from Sun)
Solar Energy
Hydroelectric Power
Wind Power
Wave Power
Renewable (not derived from Sun)
Tidal Power (due to the oceans grav. pull with moon.)
Geothermal Energy (tectonic plate friction; geysers)
Non-Renewable Fuels
 Coal
 Composed from matter that died millions of years
ago. Over time, intense heat and pressure
transformed into coal, one example of fossil fuel.
 To retrieve the stored energy in the coal, you have
to first dig it up (coal mines) and then burn it, both
of which have environmental impacts.
 It has a limited supply. The rate at which it is being
used is much greater than the rate of production.
We may only have enough coal for 150 more years.
Non-renewable Fuels
 Oil/Gas
 Now more heavily used than coal. Oil/gas are
examples of fossil fuels. Oil/gas are easier to
extract than coal (pumps instead of mines).
 Oil/gas has to be burned (like coal) to release its
energy. That energy powers an engine. Burning
oil/gas also has environmental impacts.
 It is unknown how much oil/gas remains for the
future, however in 2003, it was estimated around
1 x 10 14 litres.
Non-renewable Fuels
 Wood/Biomass
 For ages, wood has been burned for heating and
cooking and this continues today.
 Sugarcane (and other plants) produce oils that can
be used to produce biofuel that can power cars.
 Food waste can also be used to produce fuel (as
well as cow manure). However, these are not high
grade fuels (see energy density later).
 All the above have to be burned for use, therefore
having environmental impacts.
Non-renewable Fuels
 Nuclear Fuel
 Nuclear energy does not come from the sun.
Nuclear fuel materials have unstable nuclei that
can split and give off energy.
 Nuclear fuel does not have to be burned, however
it does have radioactive waste and is difficult to
dispose of.
 Like coal, nuclear fuels (like uranium) have to be
extracted from the ground and then purified for
use.
 See Nuclear Power in 8.3/8.4 PowerPoint also.
Energy Density
 Some fuels are more
efficient than others,
we categorize this as
Energy Density.

Energy Density is
the ratio of the
Energy produced to
the mass required
(unit: MJ/kg).
Fuel
Energy Density (MJ/kg)
Fusion fuel
300,000,000
Uranium-235
90,000,000
Gasoline (Petrol)
46.9
Diesel
45.8
Biodiesel
42.2
Crude oil
41.9
Coal
32.5
Sugar
17.0
Wood
17.0
Cow dung
15.5
Household waste
10
Renewable Fuels = The Future
 Solar Energy
 Collecting the sun’s energy directly. Mirrors can
focus a “hotspot” to collect the energy that can
be used to power engines that can do work.
 Photovoltaic cells can also collect and store the
sun’s energy to power buildings and homes.
 Of course, this is only useful on sunny days and
places with a good source of sunlight.
Renewable Fuels
 Hydroelectric Power
 The principle begins with rain!
 The Sun heats the ocean and turns into water
vapour, which then produces clouds, which leads
to rain. When water rains onto a mountain, the
water has a high PE. This energy can do work as
the water runs down the mountain.
 Water wheels were an early discovery; utilize
falling water to generate usable energy.
Renewable Fuels
 Wind Power
 Warm , less dense air
moves upwards =
Wind.
 In the last couple of
decades, more wind
turbines have
popped up as
sources of energy.
Denmark produces 20% of its
electricity from wind power.
The kinetic energy of the wind
turns a fan, which turns a coil (in
the presence of a magnetic
field), which generates
electricity.
Renewable Fuels
 Wave Power
 Water waves spread out their energy that arrives
at beaches all around the world.
 This energy can be used to power turbines and
produce electricity.
 With today’s technology, it is now more viable to
use wave power more than ever.
Worldwide Consumption of Energy