ACE Information Programme
aric
Introduction
In the developed world, energy use contributes more than any other
activity to greenhouse gas emissions, which may cause global
warming. This is because most of our energy comes from carbonbased fossil fuels like coal, oil, and natural gas. When we burn these
fuels for heat, power, and transportation, the carbon they contain
combines with oxygen from the air to form carbon dioxide, the most
abundant greenhouse gas. Using energy more efficiently can help to
reduce carbon dioxide emissions, but won't eliminate them, so long
as we continue to rely on fossil fuels as our energy source to begin
with. To eliminate the problem altogether, and achieve a sustainable
energy future, we need to use renewable sources of energy, like the
wind, the sun, rivers, and oceans. This fact sheets looks at
renewable energy.
What is Renewable Energy?
Energy sources which are not used up or depleted by overconsumption are called "renewable". They are naturally replenished,
and can either be managed so that they last forever, or their supply
is so enormous that they can never be meaningfully depleted by
humans. In addition, unlike the fossil fuels, most forms of renewable
energy do not release carbon dioxide as a by-product into the
atmosphere. Biomass energy (energy obtained from the burning of
plant material) does release carbon dioxide, but it is only returning to
the atmosphere as much as was removed through photosynthesis
during the plant’s lifetime. Burning fossil fuels, by contrast, returns
carbon dioxide to the atmosphere which has been locked away in
the Earth’s crust for hundreds of millions of years.
Global Climate Change Fact Sheet Series: KS4 & A
117
ACE Information Programme
aric
Sources of Renewable Energy
Solar Energy
The Sun provides a basic form of energy for all
living organisms. It has been shining for nearly 5
thousand million years, and will probably go on
shining for at least as long. Solar energy is
therefore free and inexhaustible. Converting
sunlight into useful forms for human consumption
is not exactly free, but with today’s technology, it
is not nearly as expensive as it once used to be.
Sunlight has been used by humans for drying
crops and heating water and buildings for millennia - called passive
solar heating. A twentieth-century technology is photovoltaics, which
turns sunlight directly into electricity.
Wind Power
Air moves around the Earth because of the differences in
temperature and atmospheric pressure which exist. This movement
of air can also be harnessed as a form of energy, and has been
since
ancient
times.
Today,
advanced
aerodynamics research has developed wind
turbines that can produce electricity on a very
economic basis. Wind turbines are often grouped
together in farms, located in exposed areas of
countryside, either near coasts or on hill tops
which experience a regularly prevailing wind
throughout the year.
Geothermal Energy
Rocks under the Earth's crust contain naturally decaying radioactive
materials like uranium and potassium, producing a continuous
supply of heat The amount of heat within 10,000 meters of the
Global Climate Change Fact Sheet Series: KS4 & A
118
ACE Information Programme
aric
surface contains 50,000 times more energy than all the oil and gas
resources in the world. Geothermal energy taps into the heat under
the Earth's crust to boil water. The hot water is then used to drive
electric turbines and heat buildings. The areas with highest
underground temperature are in regions
with active or geologically young
volcanoes. These "hot spots" occur at
the boundaries between tectonic places
where the crust is thin enough to let the
heat through. Many of these “hot spots”
occur around the Pacific Rim, called the
"ring of fire" for all of its volcanoes.
Hydroelectric Power
On Earth, water is neither created nor
destroyed, but is constantly moved
around. Water evaporates from the
oceans, forming clouds, falling out as rain
and snow, collecting into streams and
rivers, and flowing back to the sea. All this
movement provides an enormous opportunity to create useful
energy. Hydroelectric power uses the force of moving water to
produce electricity. Hydropower is one of the main suppliers of
electricity in the world, and the main source of renewable energy,
but is most often in the form of large dams which disrupt habitats
and displace people. A better approach is to use small scale hydro
plants.
Biomass Energy
Biomass is a term we use to describe plant materials and animal
wastes used for energy. Plants form the basis of the food chain, on
which all life on earth depends. But in terms of energy production
“biomass” refers to using tree and grass crops, and forestry,
agricultural, and urban wastes. It is the oldest source of renewable
Global Climate Change Fact Sheet Series: KS4 & A
119
ACE Information Programme
aric
energy known to humans. Biomass is a renewable energy source
because the energy it contains comes from the Sun. Through the
process of photosynthesis, chlorophyll in plants captures the Sun's
energy by converting carbon dioxide from the air and water from the
ground into "carbohydrates," complex compounds composed of
carbon, hydrogen and oxygen. When these carbohydrates are
burned, they turn back into carbon dioxide and water, and release
the Sun's energy they contain. In this way, biomass functions as a
sort of natural store of solar energy.
Use of Renewable Energy
Compared to the use of fossil fuels, the harnessing of energy from
renewable sources for mass consumption is still limited. Large scale
hydroelectric power contributes about 20% of the world’s energy
needs. In the UK however, energy from renewables currently
contributes only 3% to the total electricity consumed. About half of
this comes from hydroelectric power, with about 20% from landfill
gas and 10% from wind power. In the UK, the Government is trying
to encourage the uptake of renewable energy through the NonFossil Fuel Obligation, which requires energy suppliers to purchase
some of their electricity from renewable sources.
Barriers to Renewable Energy
One of the major reasons why the use of renewable energy is still
relatively limited is its cost compared to fossil fuel generated power.
Recently, improved technology has made wind power and biomass
energy economically more competitive. The cost of some solar
energy designs, however, remains fairly high, and it is unlikely that
countries like the UK, with unreliable sources of sunlight, will invest
considerable sums of money into developing this resource within the
short term future. Furthermore, renewable energy systems can often
be locally intrusive: many people object to large numbers of wind
Global Climate Change Fact Sheet Series: KS4 & A
120
ACE Information Programme
aric
turbines occupying the countryside, and emissions from biomass
waste incineration have the potential to cause health problems if
unmanaged. Despite these barriers, however, renewable energy
over the long term is likely to have a secure future, and will continue
to provide an increasing proportion of the world’s energy needs
whilst concerns about the climatic impacts of fossil fuel power
generation remain.
Conclusion
Reducing our dependence on fossil fuels such as coal, oil and gas
for the production of energy will not be an easy task. Part of the
solution will come from a family of diverse energy technologies that
share one common thread - they do not deplete or destroy our
natural resources. Renewable energy technology taps into natural
cycles and systems, turning the ever-present energy around us into
usable forms. The movement of wind and water, the heat of the Sun,
heat trapped underground, and the carbohydrates in plants are all
natural energy forms which can supply our needs in a clean and
sustainable way, and in a way that will not change the global
climate.
Global Climate Change Fact Sheet Series: KS4 & A
121