Energy resources and their uses - a general survey and trends

Comparing biofuels, renewables and non-renewables

Doc Brown's Physics Revision Notes

Suitable for GCSE/IGCSE Physics/Science courses or their equivalent

 The concept of energy emerged in the 19th century.

 The idea was used to explain the work output of steam engines and then generalised to understand other heat engines.

 It also became a key tool for understanding chemical reactions and biological systems.

We now know energy can exist in many forms.



 

INTRODUCTION

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.

The fossil fuel energy resources coal, oil and gas are non-renewable and will all run out one day in the future. 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. 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. Burning fossil fuels damages the environment but we have become very dependant on them for our energy needs.

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.


Energy for Transport

Petrol, diesel or heavy fuel oil are all derived from the fossil fuel oil and are burned directly in internal combustion engines e.g. in cars, lorries, diesel locomotives, ships etc. Coal was once used extensively to fire steam locomotives, but these have been mostly replaced by diesel and electric traction.

BUT much of the electricity used in trains or cars is still generated from burning coal or oil.

However, it is now possible to make biofuels that can be used directly in motor vehicles or using a mixture of biofuel and petrol, though only the biofuel component is renewable.


Energy for heating

Historically most homes and factories would be heated by coal and some domestic heating from wood. Many homes in Europe are heated from natural gas (e.g. the UK uses gas directly from the North Sea gas fields or piped gas from Norway). The gas (mainly methane, CH4) is burned in open fires or boilers to make hot water for pumping round the house, office or factory in central heating system.

Wood stoves are growing in popularity and wood can be considered renewable - but the smoke is quite polluting!

Electric heaters are obviously cleaner for cooking and heating and night storage heaters offer efficiency for the consumer, but, its still a matter of how the electricity is generated, still mainly from non-renewables sources.

Solar water heaters capture sunlight energy (infrared radiation) directly to heat up water that can be pumped to a storage tank or radiators.

A geothermal energy source uses either hot water pumped from deep underground to the surface OR using a heat pump system rather like a refrigerator working in reverse.


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. 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. 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. 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.

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) and 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. Environmental issues include how do we store, and where do we put, dangerous radioactive waste from nuclear power stations?, disasters such as the Chernobyl nuclear power plant explosion in Russia with its long term effects on people and the local flora (plants) and fauna (animals). Nuclear power stations 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.

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 in 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 ans surrounding construction materials.


Renewable Biofuels

Renewable biofuels that can be burned to heat water to make steam to drive a turbine and generator.

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.

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.

Bio-fuels when first produced are somewhat 'impure' are quite costly to refine into quality fuels.

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. 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 (habitats, species rich) are being cut down to grow crops for biofuels.

There is also 'cash crop' criticism of biofuel production because of water and land demands limiting space for food production - often affecting poorer countries. In some countries large areas of indigenous forest are being cleared in order to grow plant material for biofuels. This leads to loss of rich wildlife habitat affecting many species and ecosystems. Also, clearing vegetation in this way, releases (i) methane and (ii) carbon dioxide adding to the emissions from burning fossil fuels (ii) and cattle (i).


Other 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

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.


Some trends in the use of energy store resources

The industrial revolution in Europe was powered by fossil fuels, mainly coal until the mid-20th century.

In the 20th century, and into the 21st century, populations have increased and the demands for electricity are ever increasing in our 'consumer' societies.

However, with increased home insulation and more efficient electrical appliances, demand has levelled off in the UK, and may actually fall in the future.

Apparently UK demand for electricity has fallen by 9% from 2011 to 2017. A slowing economy, mild weather and energy-efficient appliances are among possible reasons for decline

The move away from fossil fuels

Much of electricity generation in the UK was based on fossil fuels (oil and natural gas), but not anymore.

The figures for 2017: Natural gas 40%, coal 7%, renewables (wind, solar, hydroelectric) 30%, nuclear 21% and 2% from other sources. This is part of a good trend as we become less reliable on fossil fuels.

You should also appreciate that fossil fuels from oil and gas power most road vehicles e.g. petrol and diesel and be burn kerosene in central heating system boilers.

BUT, renewable energy resources can be used to fulfil these energy needs too. Biofuels can power vehicles, different kinds of solar panels can heat water for domestic use or heat the house or produce electricity - which can be used directly or fed into the National Grid system.

Reasons for the increasing use of renewable energy sources

The increasing use of renewable energy resources is driven by several factors ...

The highly polluting effects of burning fossil fuels on people and the environment

See  Fossil fuel air pollution - incomplete combustion, carbon monoxide & soot particulates

and  Fossil fuel air pollution - effects of sulfur oxides and nitrogen oxides

Climate change caused by increased levels of CO2 in the atmosphere - global warming.

See Greenhouse effect, global warming, climate change, carbon footprint

People power - many people, either as individuals, or members of organisations like 'Friends of the Earth' believe that use of renewables is better for our planet - and environmental science agrees with this view.

Governments of countries: This has put pressure on governments to introduce strategies and targets to reduce our impact on the 'biosphere' - we live in that narrow 'delicate' band on the Earth's surface! Energy providers are being encouraged, often with financial grants, to build plants powered by renewable energy resources.

 

What inhibits an even greater increase in renewables?

Technological change and time factors

Although we have made amazing technological advances very rapidly, it takes time to translate this into mass use of cleaner technologies using renewables.

e.g. car makers have developed electric cars and hybrid vehicles that combine the use of petrol and electricity.

Although their popularity is increasing, they are more costly than conventional petrol/diesel cars.

Research and development is ongoing, but is costly and takes time and so dependable non-renewable energy resources will be used for some time. In fact there is a case that some non-renewable power stations should be retained as an emergency backup.

Investment and cost factors

To build new renewable energy power plants is costly and not initially profitable, since fossil fuels are still more cost effective to meet our huge electricity demands.

Lack of public support

People object to industries on their doorstep e.g. wind farms can meet strong local opposition.

Making personal changes in life-style do not come easily to many of us and might be more expensive options.

At the moment, the cost of renewable electricity is higher than that generated from fossil fuels - are you prepared to pay more for YOUR environment.

As mentioned already, hybrid cars are more costly, as are solar panels - but pay back time is not unreasonable, including reducing energy requirements in the home ...

See More on methods of reducing heat transfer eg in a house - payback time

and Conservation of energy, energy transfers, efficiency - calculations

Lack of reliability compared to fossil fuels

It cannot be denied that the sun doesn't always shine to give a high light intensity for solar panels and the wind doesn't always blow strong enough to turn the turbine blades.

This situation could be helped if there was a cheaper way to store electrical energy for high peak demands.

At the moment, and I would think always, we must rely on a variety of sources and hopefully at any given time, enough electrical energy is produced to meet demand.


Energy for producing electricity is also dealt with in other pages listed below

In most power stations an energy source is used to heat water.

The heat is used to produce steam to drive a turbine that is coupled to an electrical generator.


Energy resources, and transfers, work done and electrical power supply revision notes index

Types of energy store - a comparison with examples explained, mechanical work done and power calculations

Conservation of energy, energy transfers, efficiency - calculations and Sankey diagrams gcse physics notes

Energy resources & uses, general survey & trends, comparing sources of renewables, non-renewables & biofuels

Renewable energy (1) Wind power and solar power, advantages and disadvantages gcse physics revision notes

Renewable energy (2) Hydroelectric power and geothermal power, advantages and disadvantages physics notes

Renewable energy (3) Wave power and tidal barrage power, advantages and disadvantages gcse physics notes

Comparison of methods of generating electricity, 'National Grid' power supply, mention of small scale supplies

Greenhouse effect, global warming, climate change, carbon footprint from fossil fuel burning gcse physics notes

See also The Usefulness of Electricity gcse physics electricity revision notes


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