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Energy uses: 1.3
Comparing renewable and non-renewable sources of energy
Doc Brown's Physics exam study revision notes
INDEX physics notes: Energy 1.
Comparing resources, uses, issues, trends, renewables, non-renewables
1.3A Comparing renewable and non-renewable sources of energy
INTRODUCTION
Generally speaking the world-wide demand for
energy, in particular, electrical energy is continually increasing.
This is due to the population increasing and
increasing electricity demands from the ever increasing technology in our homes
e.g. computers - often left on all day!
We do need to use as far as is practicable
sustainable e.g. renewable energy resources we can use long-term, without
running out, and are constantly replenished without harm to the environment.
Its very much in the hands of governments to
promote sustainable and renewable energy resources including sponsoring research
into energy technology - all of which takes time and money!
For any particular use of an energy resource
you have to weigh up the benefits versus the drawbacks and risks.
Which energy resources are readily
available?
What is their cost and reliability?
What is their impact on the environment?
What employment will a power generation
plant bring to a community?
Limits to the use of fossil fuels and global warming are critical problems for
this century.
Physicists
and engineers are working hard to identify ways to reduce our energy usage.
Most energy resources are used to generate
electricity and include both renewables like wind/solar power and, at the
moment, and historically, mainly fossil fuels like gas, oil and coal.
The second biggest use of energy resources is
powering transport systems and heating buildings - domestic or industrial.
 Finite
non-renewable energy resources
- fossil fuels (coal, oil, natural gas, peat) and
nuclear materials
Fossil Fuels
The fossil fuel energy resources coal, oil
and gas are non-renewable and will all run out one day in the future.
It has taken millions of years of years to form
fossil fuels from once living materials but we are consuming them at a vast rate
and contributing to global warming.
Energy store changes for fossil
fuel power station:
chemical potential energy store
(in fossil fuel)
==> thermal energy store of steam
(thermal energy store transfer from hot gases of furnace to water)
==> kinetic energy store of
turbine (mechanical energy transfer)
==> kinetic energy store
of generator (mechanical energy transfer)
==> electrical energy
output (to power line system)
Burning fossil fuels damages the environment
but we have become very dependant on them for our energy needs.
There will be plenty of fossil fuels
for hundreds of years, but the rate at which we burn them, far exceeds
the long geological time needed to form them!
Therefore we need other energy
sources in the long-term anyway, AND, minimising the impact of these
'new' renewable sources on our environment - the 'biosphere'!
Another problem in reducing our
'carbon footprint' is the large quantities of fossil fuels we use to
heat our homes (in the UK).
Four out of five homes are heated
by natural gas and many other homes will use kerosene central
heating oil. Its going to be difficult to replace this situation
with other energy resources.
Gas and oil from the North Sea
fields is running out and we have to import gas from Norway.
BUT, the cost of renewable energy is
falling all the time.
Nuclear fuels like uranium and plutonium are also finite resources and
uranium ores will all be exploited in the future - assuming nuclear power
develops on a large scale.
Energy store changes for nuclear
power station:
nuclear
potential energy store (in uranium or
plutonium fuel rods)
==> thermal energy store of steam
(thermal energy store transfer from hot gases of furnace to water)
==> kinetic energy store of
turbine (mechanical energy transfer)
==> kinetic energy store
of generator (mechanical energy transfer)
==> electrical energy
output (to power line system)
Nuclear power stations take a long
time to build, but fossil fuel power stations are much simple and faster
to build.
There is also the VERY costly problem
of dealing with dangerous radioactive nuclear waste and the safe
dismantling (decommissioning) of a nuclear reactor.
With nuclear power stations there is
always the risk of a major catastrophe, the latest being the Fukushima
nuclear power station in Japan in 2011. The accident was initiated
primarily by the tsunami following the Tōhoku earthquake, but it
demonstrated the vulnerability of such power plants to natural
disasters. An earthquake could have been just as easily been the cause.
These non-renewable energy sources are
reliable, particularly for large demands of electricity.
There are plenty of fossil fuel
resources to meet current energy demands.
Such power plants can respond quickly
to changes in demand, from peak time demands, to rapidly growing
countries like India and China with their huge populations of consumers
and resulting energy demands.
However, there is a big cost to the
environment in terms of pollution and 'greenhouse' warming of our
planet. Acid rain, global warming, oil spillages, ugly open cast coal
mines can all be minimised if not eliminated all together.
For more on pollution see ...
Fossil fuel air pollution -
incomplete combustion, carbon monoxide & soot particulates
Fossil fuel air pollution - effects of sulfur oxides
and nitrogen oxides
Pollution, Accidents
and Economic Aspects of the Petrochemical Industry
and
Greenhouse
effect, global warming, climate change,
carbon footprint
 Renewable
energy resources
Renewable energy resources rely on sunlight, wind, wave power, hydro power, biofuel, tidal
power and geothermal - they are not perfect, but renewable sources of energy
usually do less harm to the environment.
Renewable resources, theoretically,
will never run out (infinite) because the energy is renewed as it is
being used e.g. the wind blows frequently, tides and waves are always on the
move.
Renewables include solar power (direct sunlight), wind, hydro-electricity,
water waves, tidal movement (tides), geothermal energy and biofuels.
These have
several advantages over non-renewables e.g. infinite - shouldn't run out, less
damaging to the environment.
However, there are some disadvantages e.g. some are
not suitable for large scale power production AND they can be unreliable e.g.
wind speed and intensity of sunlight can be very variable.
For more details see
Renewable energy (1) Wind power and
solar power, advantages and disadvantages
Renewable energy (2) Hydroelectric power and
geothermal power,
advantages and disadvantages
See also
Biofuels & alternative fuels,
hydrogen, biogas, biodiesel (gcse chemistry revision notes)
3B. More on comparing biofuels, renewables and non-renewables
ENERGY FLOW:
chemical/nuclear
energy (fuel) => heat energy (steam) => kinetic energy (turbine blades)
=> electrical energy (generator)
Non-renewable
energy resources
The
non-renewable fossil fuels (coal, oil and gas) which are burned to heat water or air.
Fossil fuels do provide a cost
effective energy resource that can readily produce large quantities of
thermal energy - most of which is converted into electrical energy for
general home and industry use, fuels for domestic use in the home and
road and rail transport.
The cost of building fossil fuel
power stations is quite high, BUT they can be built relatively
quickly, fuel is relatively cheap and running costs are relatively
low.
Fossil fuel power plants are very
reliable and can respond to periods of high electricity demand -
they are rarely short of stocks of oil, natural gas or coal - but
these may run out many decades in the future.
The burning of fossil fuels leads to all sorts of
pollution and environmental impact
issues.
The carbon dioxide produced by combustion is a
'greenhouse gas' implicated in global warming and climate change.
See
Greenhouse
effect, global warming, climate change,
carbon footprint from fossil fuel burning
In the
smoke are acidic gases like sulfur dioxide and nitrogen oxides which are
harmful to our health as air pollutants, and, by forming 'acid rain' wreak
havoc with ecosystems (particularly aquatic ones and trees) and cause extra
corrosion of stone and metal structures.
It is possible to remove most of
the sulfur from oil hydrocarbons before their use, and smoke from power
stations can be treated with an alkali to remove acidic gases.
See
Fossil fuel air pollution - effects of sulfur oxides
and nitrogen oxides
There are
other environmental issues eg the 'high price' dangers of coal mining, ugly
open-cast coal mines, oil pipelines/tankers and oil spillage effects on
wildlife.
See
Pollution, Accidents
and Economic Aspects of the Petrochemical Industry
In the UK, old coal/oil fired
power stations are being replaced with cleaner less polluting gas fired
power stations which have faster start up times - much easier to respond to
higher/lower power demands.
Non-renewable fossil fuel power
stations do provide a stable and reliable electricity supply, unlike some
renewable energy resources which are distinctly unreliable eg wind power and
solar power which depend on the weather.
 The
non-renewable nuclear fuels uranium and plutonium provide energy from nuclear fission
(splitting atomic nuclei).
In principle and general design, a
nuclear power station is similar to a fossil fuel power station.
However, the initial source of the
energy store is nuclear energy, not chemical potential energy.
Inside a nuclear reaction, uranium or
plutonium atoms undergo fission to release nuclear energy.
See
Nuclear Fission Reactions, nuclear power
as an energy resource
The thermal energy generated from the
nuclear energy store is used to heat
water or carbon dioxide gas, either way, the hot fluid is used to make steam
via a heat exchanger for safety reasons to drive turbines and generators.
Good points
Nuclear power plants do not emit
greenhouse or harmful polluting gases into the atmosphere.
They, in most cases, reliable
sources of 'bulk' electricity production.
There is enough nuclear fuel
around to meet current nuclear power station demands - but building
new nuclear power plants is controversial in some countries e.g.
Iran, for fear of more countries developing nuclear weapons.
There are unfortunately some
serious issues with nuclear power.
Environmental issues include how do we store, and where do we put,
dangerous
radioactive waste from nuclear power stations?
Some waste is highly
radioactive for a short time, but other waste is still radioactive for
thousands of years - this is a really big problem.
Disasters such as the
Chernobyl nuclear power plant explosion in Russia have long term effects
on people and the local flora (plants) and fauna (animals) - the local
population in the nearest town and villages had to be relocated to safe
areas.
Nuclear power
stations are very expensive and may take over a decade to build and involve the most complicated
technology of any means of power production.
Safety standards must be
exceptionally high and very costly.
The availability of uranium ores,
and plutonium made in nuclear reactors, is quite limited (finite)
and the production of suitable nuclear fuel rods is very expensive.
As well as costly to build, they
are very expensive to decommission, e.g. the central core of a
disused nuclear reactor is full of radioactive material and much of
the surrounding structure will also be contaminated with harmful
radioisotopes.
See
Properties of radioactive
nuclear emission & symbols - dangers of radioactive emissions
Fossil and nuclear fuelled power
stations are reliable and there is plenty of coal, oil, natural gas,
uranium and plutonium to power them.
They are also capable of responding to
high demand situations.
Its particularly easy to increase the amount of
fossil fuel burning to make more steam to drive the generators.
This is one
of the main reasons why changing to renewable energy stores will not happen
quickly. Fossil fuels are a finite resource and would run out in the
long-run, but there still huge deposits available of coal, oil an natural
gas.
The cost to extract fossil fuels and
build power stations is relatively low, but nuclear power plants are VERY
costly to build and technically much more demanding to produce a safe
operation.
Nuclear power plants are also very costly to
decommission at the
end of their useful life - you have to deal with a lot of radioactive waste
from the reactor core and surrounding construction materials - its costing
billions of pounds in the UK to clean up the oldest nuclear power
stations.
Renewable Biofuels
Renewable biofuels that can be burned to heat water
to make steam to drive a turbine and generator.
The basic idea is to have an
alternative combustible material instead of coal, oil or natural gas.
Bio-fuels from bio-mass are used to
power electricity generator or motor vehicles.
BUT, not every example is large
scale, on decaying, animal dung generates methane gas which on burning
can be used for cooking or very small scale electricity generation.
Biofuels are a renewable energy stores
made from plant materials or animal waste.
They can be gases, liquids or solids and
all can be burned to create steam to drive turbines and electricity
generators.
Biomass, like woodchips, can be burnt on
a large scale to make steam to drive turbines and generators to produce
electricity.
Energy store changes for biomass
power station:
chemical potential energy store
(in woodchip fuel)
==> thermal energy store of steam
(thermal energy store transfer from hot gases of furnace to water)
==> kinetic energy store of
turbine (mechanical energy transfer)
==> kinetic energy store
of generator (mechanical energy transfer)
==> electrical energy
output (to power line system)
Biofuels are renewable
energy sources and come in a variety of forms eg woodchips (trees or waste
from timber products), alcohol (ethanol
from fermenting sugar cane), biodiesel (from vegetable oil) and
biogas (methane from anaerobic digestion of sewage waste) and are all
derived from plant materials eg crops or bacterial digestion/decay of waste
organic material.
They are 'reasonably' reliable through
the yearly (or more) growing seasons and crops take a short time to grow,
BUT, they cannot respond quickly to high demand without a huge pre-arranged
store of fuel - dependant on how much crop is grown, harvested and processed
- not quite as fast as 'harvesting' fossil fuels from oil wells or coal
mines!
Bio-fuels when first produced are
somewhat 'impure' are quite costly to refine into quality fuels.
Reducing our carbon footprint or just
maintaining a sort of 'neutrality' maybe?
The theoretical 'carbon neutral' idea behind using
biofuels is that the carbon dioxide released on burning is re-absorbed by
plants and utilised in photosynthesis to create the next fuel crop.
In other words, you try to match the
rate of crowing a biofuel crop, with the rate you burn it as a fuel.
Issues and criticisms of renewable
biomass fuel production
But,
even though this sounds fine in principle, there are still environmental
issues eg in Brazil and other countries, huge areas of ecological valuable
natural rain forest (loss of plant and animal species rich habitats) are being cut down to grow
crops for biofuels.
Also, the cost of refining biofuels is very
high - technology and energy costs - renewable rarely means 'cheap'.
AND you are still producing carbon
dioxide to contribute to global warming - no good, especially if we are
burning biomass at faster rate than it grows back!
There is also 'cash crop' criticism of
biofuel production because of water and land demands limiting space for food
production - often affecting poorer countries.
There is a lack of farmland for
growing suitable biofuel crops.
Unfortunately, one solution, in some countries,
is large areas
of indigenous forest are being cleared in order to grow plant material for
biofuels. This leads to loss of rich wildlife habitats affecting many
species in their ecosystems.
Also, clearing vegetation in this way, releases (i) methane
and (ii) carbon dioxide adding to the emissions from burning fossil fuels
(ii) and from cattle (i).
The animals that create dung
biomass, also produce methane gas, a powerful greenhouse gas, whose,
albeit minute, concentration is steadily rising - in fact large
tracts of forest are being cut down in favour of rearing huge herds
of beef cattle.
For more see ...
Biofuels & alternative fuels,
hydrogen, biogas, biodiesel (GCSE level chemistry revision notes)
Other notes on renewable energy resources
These do not run out, the energy store
is being constantly replenished - renewed!, but there both
advantages and disadvantages to their use. For detailed discussions read
the following pages ...
Renewable energy (1) Wind power and
solar power
Renewable energy (2) Hydroelectric power and
geothermal power
Renewable energy (3) Wave power and tidal power
Biofuels & alternative fuels,
hydrogen, biogas, biodiesel
You can't say renewable energy stores do
no harm to the environment, but they are less damaging than non-renewable
energy resources such as burning fossil fuels.
Two major problems that can beset some
non-renewable energy stores is there inability to cope with high demand
situations and unreliability.
INDEX physics notes: Energy 1.
Comparing resources, uses, issues, trends, renewables, non-renewables
Keywords, phrases and learning objectives
on energy resources
Comparing renewable and non-renewable sources of
energy advantages disadvantages
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INDEX physics notes: Energy 1.
Comparing resources, uses, issues, trends, renewables, non-renewables
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