Unit 2 – Sources of Electrical Energy
STUDENTS’ GUIDE
CHALLENGE
What are the advantages and disadvantages of each energy source that can be used
to GENERATE electricity?
ACTIVITY FOCUS
Read about the many ways to generate electricity. Some use renewable resources
such as wind and solar, while others use non-renewable resources such as coal,
natural gas, and fuel oils. Identify the advantages and disadvantages of each. Which
sources of electrical energy are available for Hong Kong? Do you think they cost the
same?
MATERIALS
For each student
“Electrical Energy Sources” Chart
SAFETY NOTE
General classroom safety precautions apply.
PROCEDURE
1.
Use the reading below to identify the advantages and disadvantages of the
different sources of electrical energy.
2.
List the advantages and disadvantages of each energy source on your copy of the
“Electrical Energy Sources” chart your teacher distributes.
Reading: Energy Sources Used to Produce Electricity
Biomass Energy
Biomass power refers to the production of power by burning plants or waste material.
Power plants that use biomass (wood, paper, or municipal waste) are similar to power
plants that burn coal, oil, and natural gas. The fuels are combusted in a boiler and
produce steam to drive a conventional steam TURBINE. The material burned can be a
combination of renewable [wood] and non-renewable [garbage, coal etc.] materials.
One of the advantages of the production of biomass energy is to reduce the waste in
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landfills. This has some of the same environmental concerns as incinerators. Currently
biomass is not a major electrical energy source in Hong Kong, though it is used for a
few other purposes.
Fossil Fuels (Coal, Fuel Oil, and Natural Gas)
Coal is the most abundant fossil fuel in the world and the leading source of electricity in
Hong Kong. Coal is powdered into a fine dust and injected into the furnace to power a
conventional steam boiler. Fuel oil and natural gas are also used as fuels to boil water
in the steam boilers. The gases produced by the combustion of coal – sulphur dioxide
and nitrogen oxides – have been the major producers of acid rain and other gases and
byproducts that can harm the environment. Modern methods of burning fossil fuels
can reduce significantly the harmful gases released in the environment. Natural gas
produces only water and carbon dioxide when burned “cleanly”. Fossil fuels are nonrenewable energy sources. Currently fossil fuels (primarily coal and gas) are the major
energy source used to generate electricity in Hong Kong.
Geothermal Energy
Geothermal Energy is heat (thermal) derived from the earth (geo). It is the thermal
energy contained in the rock and fluid (that fills the fractures and pores within the rock)
in the Earth's crust. It is usually used to heat water to produce steam, which drives
conventional turbines. It is considered renewable because the resource is vast. The
materials and energy used to build and maintain geothermal power plants are usually
non-renewable. There are some environmental concerns related to the impact on the
land where such plants are located. Geothermal energy is not used in Hong Kong
because it is too far below the ground for practical use here.
Hydroelectric Power
Hydroelectric power generators use water to spin a turbine connected to a generator.
The water may come from rivers, streams, or lakes. Hydroelectric power, therefore is a
renewable energy source. Construction of a dam is often necessary. The KINETIC
ENERGY in the flowing or falling water is converted to mechanical energy by the
turbine and then into electricity by the generator. The materials and energy needed to
construct necessary dams, turbines etc. usually are non-renewable. There are
significant concerns related to the blocking of streams, rivers, or lakes to create dams,
and to relocating people who live there. There is a pumped hydroelectric storage
facility for Hong Kong. Pumped storage is not renewable unless the energy it stores
was generated with renewables. Ocean Energy is similar to hydroelectric power
because it uses the motion of water in waves, tides or currents. There are limited
investigations underway regarding the use of Ocean Energy in Hong Kong.
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Nuclear Power
When atoms of uranium are split apart (fission reactions), the heat generated can be
used to boil water and produce steam to power a turbine. Concern over environmental
effects and accidents, such as the accidents at Chernobyl in the former Soviet Union
(1986) and Three Mile Island in Pennsylvania (1979), have raised serious questions
regarding the construction of new plants and the safety and maintenance of existing
plants. Recently, nuclear power has been considered to be one of the solutions to tackle
global climate change problem, as there will be no greenhouse gas emissions. Moreover,
nuclear power plants do not produce the air pollution of fossil fuel burning plants.
However, they do generate RADIOACTIVE waste that raises many safety and
environmental issues and require special facilities for disposal. A considerable amount
of Hong Kong’s electricity comes from nuclear power generating stations on the
Chinese mainland.
Solar Energy
Energy from the Sun can be directly converted into electricity by using solar cells
(PHOTOVOLTAICS). It can also be used to heat water (solar thermal energy) and
other liquids, causing them to transfer their thermal energy to other sources, such as
swimming pools, hot-water heaters, and even turbines to produce electricity. In order
to generate significant amounts of electrical energy solar collectors require large areas of
land. The photovoltaic energy from the Sun is renewable. Currently the production of
some solar cells creates hazardous wastes, and uses a lot of energy. The materials and
energy used to produce the cells are usually non-renewable. Photovoltaic energy is
used in Hong Kong to provide electricity for road signs and for other specialized
applications. There are examples of integrated photovoltaic facilities in some of the
buildings in Hong Kong. It is common that calculators and toys are powered by
photovoltaics. Some solar thermal energy is used for water heating in Hong Kong.
Units 4 & 5 provide additional experiences with the use of solar energy to heat water
and produce electricity.
Wind Energy
Wind can turn the blades of large turbines to produce energy. Wind farms can be set
up in areas where the wind blows at speeds of at least 4 meters per second for long
periods of time. If the wind speed is higher, more energy will be produced. However,
vast areas of land must be used for wind turbines to produce a significant amount of
electric power. The wind as an energy source is renewable. The materials needed to
build the turbines and the energy used in building them may not be renewable. The
land on which the wind farm is placed can be used for some other purposes such as
farming. Currently, pilot wind generation projects are being built to produce electricity
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in Hong Kong. There are also some small wind turbines in use here. In Unit 12, you
will investigate wind and the operation of wind turbines.
ELECTRICAL ENERGY SOURCES CHART
Energy Source
Advantages
Disadvantages
Availability in
Hong Kong
Biomass
Coal
Gas
Geothermal
Hydro
Nuclear
Oil
Solar
Wind
3.
In your group, discuss the advantages and disadvantages you selected and
recorded on your chart for each energy source. Come to agreement on each choice
for your group. Add the results to your group’s copy of the chart. Be prepared to
add your group’s choices to the class list projected by your teacher.
4.
In your group complete the “Availability in Hong Kong” column on your group
“Electrical Energy Sources” Chart. Make your decision based on those sources of
energy that are available and in use at the present time. Add any comments that
you think are important to the group chart or as notes and be ready to share your
group’s decisions with the class.
DISCUSSION
5. Discuss in your group how the generation and use of electricity in Hong Kong can
be made more sustainable, and still affordable. After the discussion, plan with your
group to do research and develop recommendations based on your research on this
topic. Be prepared to share your group’s plan with your teacher and classmates.
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