Non-renewable resources exist in finite amounts and are not renewed after they have been depleted (they are forms of solar energy stored in the Earth, that are no being extracted and burned by humans), eg. coal, oil.
Renewable resources can be used over and over agains and are considered to be sustainable, eg. geothermal, solar, wind.
Replenishable resources: in between renewable and non-renewable sources of energy, can be replaced over a long period of time (if depletion rate is faster than recharge rate, the natural capital is depleted, eg. fuelwood.
Energy consumption and trend
Currently, oil is the largest energy source, supplying 33% of all energy, followed by coal (30%) and natural gas (24%). In other words, fossil fuels power more than 85% of the world’s economy. 4% of the energy is nuclear power (from uranium).The remaining 11% are renewable energy sources, with hydro-electric power (HEP) generating 7% of the total.
Renewable energy production is growing, with wind power that accounts for more than half of the growth.
The nuclear energy consumption is declining due to the dangers of radioactive waste (especially in Japan after Fukushima incident).
Energy and development
As the world’s population continues to grow and as peoples level of development continues to grow, so does the demand for energy. In traditional less developed societies the main source of energy tends to be fuelwood.
As countries begin to develop they can begin to afford to buy raw materials and to build power stations. Most commonly fossil fuels are burned because the technology exists and at the moment they are widely available.
However, as countries develop further their sources of energy may change again. They will probably still be heavily dependent on fossil fuels, but will begin to use more renewable energy and probably more nuclear. The reasons for the change include:
- Greater concern for the environment
- Rising prices of fossil fuels
- The knowledge that fossil fuels are finite
- Aim to reduce reliance on fossil fuel exporting countries
- Improvements in renewable technology
- The hope of developing and selling renewable technology
- Better technology and increased stability allowing nuclear development
There are always some exceptions to the rule. For example Costa Rica gets the majority of its power from renewable sources and countries like Lithuania and France get nearly all of theirs from nuclear.
Why use renewable energy?
Many countries are preferring renewable sources of energy as they are more environmentally friendly than the combustion of fossil fuels, and many countries are concerned about global warming. Countries may wish to reduce the reliance of imported fuels and fosssil fuels may be more expensive than alternative means of generating energy.
And why not?
Other countries are not using renewable energy sources, as they are often in early stages of development and may not be able to afford alternative energy sources, especially as technology is often limited. Furthermore, countries may gear towards fossil fuels, as they do not meet the criteria for certain types of renewable energy (not enough sunshine for solar energy, no coastal areas for tidal energy) and governments may not prioritise renewable energy.
Wind energy is a renewable source of energy in which wind powers turbines. The kinetic energy from the turbines is then converted into electricity.
Advantages of wind power
- produces reasonable levels of electricity (effective and comparatively cheap)
- suitable locations for turbines can be found in almost every country
- flexibility of location with offshore windfarms gaining in popularity
- visual impact on scenic landscapes
- NIMBY (not in my backyard) protests
- noise pollution for residents and wildlife
- rotor blades may kill birds
- TV and radio reception can be affected by wind farms
- requires wind
Solar energy can be obtained from solar photovoltaic cells, which convert light energy into electricity.
- potentially infinite supply of free fuel
- safe and emission-free
- effective for low power uses such as heating
- less effective in cloudy countries and higher latitudes
- high initial capital input (costly)
- less effective for high output uses
Geothermal energy is extracted from hot rocks or water beneath the Earth’s surface, as temperatures rise when you go deeper into the Earth.
Advantages of geothermal energy:
- extremely cheap and emission-free
- water is pumped back into the ground and re-used
- can operate any time of the day/year (not affected by weather conditions)
Disadvantages of geothermal energy:
- requires suitable geology
- each well may only be used for about 25 years
- saline and poisonous ground water
Hydroelectric power plants
In hydroelectric power plants, water is stored behind a dam, before it flows down a slope to turn a turbine. The kinetic energy from the turbine is converted to electricity via a generator.
Advantages and disadvantages of HEP
HEP is a renewable source of energy that is relatively cheap to maintain and is emission-free (won’t enhance global warming or contribute to acid rain). Also, storage of water helps reduce the likelihood of water shortages, while more energy production may attract manufacturind industries and foreign investors. Besides, the dam may protect areas further downstream from flooding.
On the contrary, settlements upstream of the dam may be more threatened by flooding, so people would need to be relocated. Also, roads may have to be rerouted and farmland and forests may be lost to flooding. However, only a limited number of rivers is suitable for HEP and the construction of dams can hamper navigation up and down a river and disrupt migration patterns of wildlife. Dams also reduce the deposition of alluvium further downstream. Furthermore, the construction of dams could result in noise pollution and visual pollution, and the cost of the dam may have to be funded by local residents, increasing taxation.
Factors for location of HEP station
HEP stations are usually located in mountainous areas in a valley that can be dammed. They should be located at rivers that have a steep gradient to supply sufficient headwater. Furthermore, the local geology must be of stable, impermeable bed rock to prevent water from soaking through. Also, HEP stations are mainly built in regions where climate ensures the supply of water (areas with high amounts of precipitation and meltwater). HEP stations are favourably constructed along transmission lines, which transport the electricity to markets (often industies)
Nuclear energy is obtained from from the fission of uranium atoms (uranium atoms split to release heat). This heat causes water to evaporate and form steam. Steam is then used to power a turbine and the kinetic energy from the turbine is converted into electricity by a generator.
Advantages of nuclear energy
Nuclear energy is cheap to produce and does not contribute to global warming as no greenhouse gases are released in the process. It requires only small amounts of uranium, as these produce a large amount of energy.
Disadvantages of nuclear energy
However, the construction cost for nuclear reactors is high and many people are concerned about the possibility of accidents such as a reactor meltdown (Chernobyl and Fukushima). Furthermore, radioactivity of waste may be harmful to public health, causing cancers or mutations. Besides, decommisioning nuclear power plants is expensive, and the land on which they were built can not be used for many generations due to the long half-life time of uranium.
Also, nuclear power plants may become terrorist targets and technology could be used to make nuclear weapons.
Accidents at nuclear power stations (eg. reactor meltdown at Chernobyl) cause long lasting radiation leakage and pollute the atmosphere and environment for hundreds and thousands of years (due to the long half-life time of uranium).
Fossil fuels: Oil
Oil is a fossil fuel that has mostly been formed from prehistoric organisms whose remains settled at the bottoms of oceans and lakes millions of years ago. As layers of sediment covered them, the pressure on them increased which in turn increased the temperature. This process changed their chemical composition, eventually transforming them into oil.
In an oil station, the chemical energy in the oil is converted to electrical energy. The oil is piped into a boiler, where it is burned, thus releasing heat, which is used to warm pipes of air coiled around the boiler. The air expands and therefore the steam is under high pressure. This pressure is used to drive a turbine and a generator converts the kinetic energy into electrical energy. Then a transformer converts the electrical energy from the generator to a high voltage, which allows the energy to enter the power grid.
Advantages of oil as an energy source:
- relatively cheap to extract and convert
- energy production can be increased or decreased according to demand
- the technology to burn oil to generate electricity already exists
- oil fired power stations have a high efficiency
- produces sulfur as a by-product that can be used for many industrial applications
Disadvantages of oil as an energy source
- produces hazardous waste, emits greenhouse gases and metals and contributes to acid rain
- is vulnerable to large scale changes in its price
- risk to people and environment, eg. Oil spills or drilling accidents
- often located in politically unstable countries or environmentally sensitive areas e.g. Libya and Iraq.
- depends on water for turbines
Fossil fuels: Coal
Coal is a fossil fuel (mainly made of carbon) that was produced by the burial of swamps and peat bogs by sediments and tectonic activity. With burial, the plant material was subjected to high temperatures and pressures. This caused physical and chemical changes in the vegetation, transforming it into peat and then into coal.
In a coal power station, the chemical energy in coal is converted to electricity. After transport into the coal plant, coal is pulverised and fed into a large industrial furnace that is surrounded by large boiler tubes filled with water. Coal is burnt and heats the water in the boiler tubes, which turns to steam. Steam is used to turn a turbine and a generator converts the kinetic energy into electricity.
Advantages of coal as an energy source:
- plentiful supply (up to 250 years of coal left)
- energy production using coal can be increased or decreased according to demand
- the technology to burn coal to generate electricity already exists
- relatively cheap to mine and convert energy by burning
Disadvantages of coal as an energy source:
- burning releases C02 (greenhouse gas)
- burning of sulfur forms sulfur dioxide which causes acid deposition
- soot particles produce smog and lung disease
- land degradation and pollution due to coal mines
- lower heat of combustion than other fuels
Location of coal power stations
Coal power stations are commonly located on flat, cheap land near coal mines, as coal is bulky and transport consts would be high. Also, they are often near rivers or lakes, as water is required in the cooling processes. Furthermore coal power station are often found along transport routes (roads/railways) for coal deliveries and along transmission lines, to transport energy to its market.
Fossil fuels: Natural gas
Natural gas is formed when layers of buried plants and animals are exposed to intense heat and pressure over thousands of years. The energy that the plants and animals originally obtained from the sun is stored in the form of carbon in natural gas.
Energy from natural gas is produced by extracting the gas from the Earth which is then transported to the power station where it is combusted in boilers and turbines to provide electricity.
Advantages of gas as an energy source:
- Energy production using gas can be increased or decreased according to demand
- The technology to burn gas to generate electricity already exists
- Cleaner and cheaper than coal and oil
- Easy transport
- Safer than nuclear energy
Disadvantages of gas as an energy source:
- Gas is finite so will eventually run out (probably in 50-70 years)
- A lot of gas is located in politically unstable countries or environmentally sensitive areas.
- Gas is vulnerable to leaks and explosions
- Terminals are unattractive and take up lots of space
Greenhouse effect and global warming
Global warming is the gradual increase of the average temperature of the Earth’s atmosphere and oceans. Shortwave radiation from the Sun is reflected off the Earth as longwave radiation. Greenhouse gases such as CO2, SO2 (sulfur dioxide) or methane prevent longwave radiation from escaping into space, and instead redirect the rays of longwave radiation back to the Earth, which again absorbs part of the heat. This repeated absorption of heat is thought to lead to a rise in global temperatures.
Global warming is a natural process, and without it, global temperatures would average at -18°C, not 15°C. However, when referring to the global warming, most people think of the enhanced greenhouse effect (or enhanced global warming): in other words, an increase in global temperatures due to human activites beyond climatic equilibrium.
Human causes of global warming
There are multiple human activities that have contributed to the rise in the percentage of greenhouse gases in the atmosphere. For example, combustion of fossil fuels in power stations for the purpose of generating electricity has increased the concentration carbon dioxide and sulfur dioxide. These gases are also released in transportation including automobiles and air travel. Furthermore, agricultural activities such as cattle grazing (releases methane) and rice production are contributors to greenhouse gas emissions. Additionally, deforestation prevents the use of carbon dioxide by trees, as this type of carbon sink is being destroyed for logging or alternative land uses.
Impacts of global warming
Global warming results in the melting of polar ice, and consequently a loss of habitat for species and loss of biodiversity in the tundra ecosystems (eg. polar bears may become extinct). Also, melting of polar ice may result in sea level rise, so coastal areas may become flooded. Areas in higher altitudes may become drier due to sparse and irregular rainfall, and consequently crop production would be reduced. Higher temperatures would also increase the incidence of weather related hazards and tropical species may spread to other areas.
Reducing emission of carbon dioxide
Many countries are trying to reduce the emission of carbon dioxide. International agreements have been made to use more alternative energy supplies such as solar power and minimise the combustion of fossil fuels. Furthermore, afforestation or reforestation schemes will reduce levels of carbon dioxide in the atmosphere as trees absorb this greenhouse gas for photosynthesis. Also, people are encouraged to conserve energy and recycle more to reduce the incineration of waste, as well as use emission-free cars or bikes as a mode of transport.
Acid rain is caused by sulfure dioxide and nitrogen oxides in the atmosphere (from sulfur fuels and fertilisers). Sulfur dioxide and nitrogen oxides may be released by the combustion of fossil fuels in thermal power stations, industy, homes and car engines.
Acid rain results in the acidifications of lakes and seas, causing fish and other aquatic animals to die. Also, acid rain causes the soil to become acidic and ecourages the leaching of minerals from the soil. This can poison plants and trees.
Air pollution is worst in NIC’s and LEDC’s where industrialisation is rapid and strict regulation on industrial plants and vehicles does not exist.
Causes of air pollution
Air pollution may be attributed to transportation (car exhaust fumes), industry (manufacturing industries), power stations, domestic fires, and combustion of rubbish.
Effects of air pollution
Air pollution may result in poor levels of visibility, due to smog in the atmosphere. High levels of carbon dioxide in the atmosphere can lead to breathing difficulties such as asthma and may result in acid rain (which wears away stonework).
The effects of air pollution can be minimised by reducing traffic congestion, encouraging the use of scrubbers in factories and catalytic converters in cars.
Around 2.5 % of the water on Earth is freshwater, but only 1.5 % of freshwater is accessible to us, as the rest is frozen or part of the soil.
Almost 70% of the world’s water usage can be attributed to agriculture (growth of crops using irrigation and supplying livestock with drinking water. Around 15% of the water is used for industrial purposes. The remaining water is used domestically (home use, eg. washing, cooking).
In LEDC’s, water is mainly used for agriculture (and sometimes domestically). In developing countries such as China and Barzil water is mainly used for agriculture and industry, whereas in MEDC’s freshwater is utilised in industry mostly (and sometimes domestically. However, domestic water consumption for domestic purposes is around 6 times higher in MEDC’s than in LEDC’s.
Water deficit is when water demand exceeds supply (too little water).
Water surplus is when water supply exceeds demand (sufficient/enough).
Water shortages may occur for different reasons, including:
- prolonged periods of drought, coupled with population pressure
- inadequate supply of rivers (bodies of water to an area)
- overuse of water supplies for human demands such as irrigation (agriculture) or industry and mismanagement
- increased pollution
Consequences of water shortage include crop failure, livestock deaths, famine, refugee migrations for access to water and conflicts over water supplies.
Managing water supply
In case of water deficit in an area, several strategies can be adopted to provide sufficient water for agricultural, industrial and domestic purposes.
- Boreholes (vertical shafts can be drilled into the ground) can be used as water wells to extract ground water.
- Reservoirs and dams can be built to store water for dry periods.
- Desalinisation extracts salt from sea water to obtain purified water.
Due to the limited availability of water, this resource has to be used sustainably. This includes treating waste water and enforcing strict regulations on the prevention of pollution of rivers and seas. Also, people should be encouraged to conserve water, ie. by mending leaking pipes, turning off taps when not in use, showering instead of bathing, and carefully monitoring irrigation systems. This can be achieved by the use of water meters in houses, as paying for water makes people more aware of their consumption.
Causes and effects of water pollution
Water pollution may lead to eutrophication as nutrients from fertiliser runoff change the composition of water and encourage the growth of algae. This lowers the oxygen supply in the water, killing other water plants and fish, as predators have no food, so the entire food chain is disrupted.
Dirty water may lead to the spread of diseases such as diarrhea, typhoid, dengue fever and malaria (the last two are transferred by mosquitoes).