Transcript Topic 8_2__World energy sources

Topic 8: Energy, power, climate change
8.2 World energy sources
8.2.1 Identify different world energy sources.
8.2.2 Outline and distinguish between renewable
and non-renewable energy sources.
8.2.3 Define the energy density of a fuel.
8.2.4 Discuss how choice of fuel is influenced by
its energy density.
8.2.5 State the relative proportions of world use
of the different energy sources that are
available.
8.2.6 Discuss the relative advantages and
disadvantages of various energy sources.
Topic 8: Energy, power, climate change
8.2 World energy sources
Identify different world energy sources.
We can divide our energy sources into two
categories: Sun-derived, and Non-sun-derived.
Fuels
Coal
Sun-Derived Energy Sources
Non-fuels
Fuels
Oil
Gas
Wood
Biomass
are
“burned”
CO2
Solar Energy
Hydroelectric
Wind
Wave
CO2
Photovoltaic
Non-Sun-Derived Energy Sources
Fuels
Non-fuels
Fuels
Hydrogen “burned”
Tidal
Uranium
Chemical
CO2
Geothermal
Chemical
CO2
3.2 +23.2 +23.0 +39.2 = 88.6%
Energy diagram for the US.
Most of our energy comes
from sun-derived fuels.
Topic 8: Energy, power, climate change
8.2 World energy sources
Outline and distinguish between renewable and
non-renewable energy sources.
Renewable resources
can be replaced in a
reasonable amount of time (or are not depleted).
Sun-Derived Energy Sources
Fuels
Non-fuels
Coal
Solar Energy
Oil
Hydroelectric
Gas
Wind
Wood
Wave
Biomass
Photovoltaic
Fuels
Non-Sun-Derived Energy Sources
Non-fuels
Hydrogen
Tidal
Uranium
Geothermal
Chemical
Chemical
Topic 8: Energy, power, climate change
8.2 World energy sources
Define the energy density of a fuel.
Energy density is how much energy you can get per
kilogram from a fuel.
EXAMPLE: Coal has an energy density of 32.5
MJ/kg. If a city has a coal-fired power plant
that needs to produce 30.0 MW of power, and it
has an efficiency of 25%, how many kilograms of
coal are needed per day?
SOLUTION: Since efficiency = output / input
0.25 = 30.0 MW / input
input = 120 MW
But 1 day = 243600 s = 86400 s so that
input = (120 MJs-1)(86400 s) = 10368000 MJ.
Thus
input = (10368000 MJ)(1 kg / 32.5 MJ)
= 320000 kg.
Topic 8: Energy, power, climate change
8.2 World energy sources
Define the energy density of a fuel.
Energy density is how much energy you can get per
kilogram from a fuel.
PRACTICE:
If coal is transported in rail
cars having a capacity of 1.5
metric tons, how many cars per
day must supply the power plant
of the previous example?
SOLUTION:
From the previous example we
calculated that we need
320000 kg of coal per day.
Since a metric ton is 1000 kg, we have
(320000 kg )/(1.5  1000 kg / car)
or 213 cars d-1!
Topic 8: Energy, power, climate change
8.2 World energy sources
Define the energy density of a fuel.
Most of our energy comes from fuels. Here is the
energy yield of various fuels:
Fuel
Fuel Type
Energy Density (MJ/kg)
Protons
Nuclear
300,000,000
Uranium-235
Nuclear
90,000,000
Petrol
Fossil
46.9
Diesel
Fossil
45.8
Biodiesel
Fossil
42.2
Crude Oil
Fossil
41.9
Coal
Fossil
32.5
Sugar
Fossil
17.0
Wood
Fossil
17.0
Cow Dung
Fossil
15.5
Household Waste
Fossil
10.0
Topic 8: Energy, power, climate change
8.2 World energy sources
Define the energy density of a fuel.
PRACTICE:
If a nuclear power plant
powered by uranium-235 has
the same output and the same
efficiency as the coal-fired
plant of the previous
example, how many kg of
nuclear fuel will it burn
per day? Per year?
SOLUTION:
From the previous example we calculated that we
need 10368000 MJ of energy per day.
Thus
(10368000 MJ)/(1 kg / 90000000 MJ)
or 0.1152 kg d-1!
This is only 42 kg y-1.
Topic 8: Energy, power, climate change
8.2 World energy sources
Discuss how choice of fuel is influenced by its
energy density.
PRACTICE:
Explain why it is advantageous
to have a submarine which is
nuclear powered, as opposed to
diesel powered.
SOLUTION:
There are two main reasons:
(1) Nuclear reactors don’t use
oxygen, so the sub can stay
under water for months at a
time.
(2) Nuclear fuel is extremely
compact for the amount of
energy it contains. Thus the sub
can cruise far before refill.
Topic 8: Energy, power, climate change
8.2 World energy sources
State the relative proportions of world use of
the different energy sources that are available.
You should have a good idea of these percentages,
from memory.
Fossil
CO2
fuels
Topic 8: Energy, power, climate change
8.2 World energy sources
State the relative proportions of world use of
the different energy sources that are available.
Topic 8: Energy, power, climate change
8.2 World energy sources
State the relative proportions of world use of
the different energy sources that are available.
PRACTICE:
Sun makes biomass through photosynthesis.
Biomass gathers and grows over time.
Biomass buried under great pressure and heat.
Biomass becomes coal, oil and natural gas over eons.
Coal, oil and natural gas are extracted.
Coal, oil and natural gas are used as fuels.
Topic 8: Energy, power, climate change
8.2 World energy sources
Discuss the relative advantages and disadvantages
of various energy sources
Renewable energy is better than non-renewable
because it will not run out.
Oil and gas are better than coal because they
burn more efficiently and produce less CO2.
Coal is cheaper and more plentiful than gas
and oil.
Nuclear power does not produce CO2.
Hydroelectric is useful to have in a grid
because it can be used to store extra energy.
Burning biomass alleviates landfills.
Nuclear waste lasts for thousands of years.
Renewable energy sources like wind turbines
and photovoltaic cells depend on the weather
conditions and have small output.
Topic 8: Energy, power, climate change
8.2 World energy sources
Discuss the relative advantages and disadvantages
of various energy sources.
Fuel
Proved
Production
PRACTICE:
reserves
in 2005
(and unit)
Proved reserves are
in 2005
resources that we are sure
Coal
909.1
5.85
we can obtain.
(109 tonnes)
Production means actual
Oil
1200.7
29.6
reserves that have been
(109 barrels)
obtained and placed on the
Gas
179.8
2.76
market.
(1012 m3)
Use the table to estimate
FYI
how long oil reserves
This is an
might last.
estimate because
SOLUTION:
Expectancy = Reserves / Production both numbers are
subject to yearly
= 1200.7109/29.6109
change.
= 40.6 years
Topic 8: Energy, power, climate change
8.2 World energy sources
Discuss the relative advantages and disadvantages
of various energy sources.
PRACTICE:
The machine shown is called
the “Bay View Bob” and can
produce enough power on Lake
Michigan waves to power a
cell phone.
Give reasons why this might
not be a good way to produce
energy?
Topic 8: Energy, power, climate change
8.2 World energy sources
Discuss the relative advantages and disadvantages
of various energy sources.
PRACTICE:
Wind power doesn’t produce greenhouse gas.
Wind power is a renewable resource.
Wind depends on the weather.
2 GW / 0.8 MW = 2500 turbines required.