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Energy uses: 1.3 Comparing renewable and non-renewable sources of energy

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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.

non-renewable fossil fuel coal oil gas diagram electricity power generation turbine generator transformer power lines

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.

gcse physics diagram of nuclear power station electricity generation non-renewable reactor fuel rods heat echanger

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

non-renewable fossil fuel coal oil gas diagram electricity power generation turbine generator transformer power lines

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.

gcse physics diagram of nuclear power station electricity generation non-renewable reactor fuel rods heat echanger

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.

renewable biomass energy store fuel diagram electricity power generation turbine generator transformer power lines

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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