Energy Resources (Cambridge (CIE) AS Environmental Management)

Renewable Energy Sources

What Are Renewable Energy Sources?

• Renewable energy comes from energy sources that will not run out and includes:

  • Biofuels (biomass including wood, bioethanol and biogas)

  • Geothermal energy

  • Hydroelectric dams

  • Tidal energy

  • Wave energy

  • Solar energy

  • Wind energy

• Once in place, these renewable energy sources do not produce any greenhouse gas emissions (with the exception of biomass):

  • However, it is important to note that greenhouse gases may be emitted in the production, construction and transport of the equipment required for the above renewable energy sources

Renewable Energy Sources Examples

Biofuels

• Biofuels (also known as biomass fuels) are renewable fuels derived from organic materials, such as plants and animal waste, that can be used as an alternative to fossil fuels:

  • However, they have only half the energy density of fossil fuels

• The three main biofuels are:

  • Biodiesel - made by refining renewable fats and oils (e.g. vegetable oils, animal fats or recycled cooking oil)

  • Bioethanol - made by fermentation (of crops rich in sugars or starches, such as corn or sugarcane)

  • Biogas - released when organic waste products decompose

   Advantages

• Biofuel is a renewable resource - uses waste or bioproducts that can be regrown

• Some vehicles can be powered by biofuel rather than using fossil fuels

• Biofuel is considered to be carbon neutral

• No sulfur dioxide is produced

   Disadvantages

• Crops of biofuel producing plants must be grown, which takes time

• Growing the crops takes a lot of land, and takes resources needed for food production

• Burning biofuels releases carbon dioxide into the atmosphere (however, it is considered carbon neutral because plants take in carbon dioxide when they photosynthesise)

Geothermal Energy

• Geothermal energy is caused by the heat that is generated from within the Earth:

  • The Earth's interior is extremely hot, partly due to radioactive elements deep in the Earth that release energy as they decay

• This geothermal energy heats up rocks in the Earth's crust, sometimes to an extremely high temperature:

  • Water can be poured into shafts below the Earth's surface

  • The water is heated and returned via another shaft as steam or hot water

  • Steam can be used to turn a turbine and generate electricity, and the hot water can also be used to heat homes

   Advantages

• Renewable resource

• Reliable source of energy

• Geothermal power stations are usually small compared to nuclear or fossil fuel power stations

   Disadvantages

• Few suitable locations on Earth, so only viable for small scale electricity production in many countries

• Can result in the release of greenhouse gases from underground

• Expensive to build and maintain

Hydroelectric Dams

• When water is stored above ground level it has gravitational potential energy

• This energy can be transferred to kinetic energy if the water is allowed to flow down the slope

• Flowing water turns the turbine to generate electricity

   Advantages

• Can respond to demand quickly so is reliable and available

• Can generate large-scale amounts of electricity in a short period of time

• Often in sparsely populated areas

   Disadvantages

• Expensive to build and maintain

• Creating reservoirs sometimes results in the need to flood valleys, which destroys habitats, towns and villages

• The pumping systems (used if water needs to be pumped up to the reservoir) often rely on fossil fuels, releasing large amounts of greenhouse gases

• Dam traps sediment which can affect ecosystems downstream

• Visual pollution

• Can prevent fish movement and migration upstream

Wave & Tidal Energy

• The rise and fall of waves or the tide can be used to turn a turbine and generate electricity

Advantages

• No pollution

• Reliable and can produce a large amount of electricity at short notice

• Renewable energy resource

• Small systems are being developed to provide electricity for small islands

Disadvantages

• Expensive to build and maintain

• Damages fragile habitats

• Very few suitable locations

• The technology is not advanced enough for large-scale electricity production

Solar Energy

• The energy from the Sun that falls on the Earth is transferred by radiation:

  • Mostly visible light and infrared radiation

• The amount of energy transferred from the Sun to the Earth each hour is roughly equal to the energy use of the world for one year

• Therefore, scientists are working hard to find methods of harnessing this energy:

  • Solar energy has a low energy density, which means large collecting devices are required

  • Collecting solar energy is expensive (due to the equipment required) and inefficient

Solar PV panels

• Solar photovoltaic (PV) panels transfer energy from sunlight electrically producing a current and therefore generating electrical power:

  • Solar cells, sometimes called photovoltaic cells, are made of semiconducting materials

  • A number of photovoltaic cells or panels connected together can supply electricity to homes, small-scale businesses, communication devices and satellites

  • Energy generated can be stored in batteries for later use

   Advantages

• Solar energy is a renewable resource

• In many places on Earth sunlight is a reliable energy resource (this means that the sun shines most of the time)

• Solar farms produce no greenhouse gases or pollution

• Solar energy can be generated in remote places where they don't have electricity (e.g. to power solar street signs in rural areas)

• Can be small- or large-scale

• Can be incorporated into building design

• Technology is improving and reducing the cost

   Disadvantages

• Solar farms need to be large-scale to produce large amounts of electricity, which is expensive to set up

• Uses large areas of land

• People often don't like the appearance of large solar farms; this is known as visual pollution

• In many places on Earth sunlight is not a reliable energy resource (there are not enough sunshine-hours to justify the set-up costs)

Wind Energy

• Wind energy is a renewable form of energy that harnesses the power of the wind to generate electricity

• It involves the use of wind turbines, which have large blades that spin when the wind blows

• The rotating blades transfer kinetic energy to a generator, which converts it into electrical energy

   Advantages

• Wind is an abundant resource that will never run out, making wind energy a sustainable and renewable source of power

• Wind energy produces no greenhouse gas emissions or air pollutants during operation, helping to reduce the negative impact on climate change and air quality

• Wind energy reduces dependence on fossil fuels and foreign energy sources, promoting energy independence and security

• The wind energy industry creates jobs in manufacturing, installation, operation and maintenance of wind turbines

• Can be small- or large-scale

• Can be on land or offshore

• Cheap to run

   Disadvantages

• Wind is not constant, and the availability of wind energy fluctuates

• Electricity generation from wind turbines depends on wind speed and consistency

• Wind turbines can be visually intrusive, especially when installed in large numbers

• Some people may find the noise generated by wind turbines to be disruptive

• Wind farms require large areas of land, which can have an impact on agricultural or natural landscapes

• Birds and bats may occasionally collide with wind turbines, causing some impact on local wildlife populations

Non-renewable Energy Sources

• Non-renewable energy comes from energy sources that will eventually run out, including:

  • Fossil fuels

  • Nuclear energy (using uranium as a fuel)

What Are Fossil Fuels?

• Fossil fuels include:

  • Coal

  • Natural gas (mostly methane) which is used in domestic boilers and cookers

  • Crude oil, which is refined into petrol, diesel and other fuels

• Fossil fuels are formed from the remains of plants and animals:

  • Chemical energy stored in fossil fuels originally came from sunlight

  • Energy from the sun was transferred to chemical energy stores within plants through photosynthesis (plants use energy from sunlight to make food)

  • Animals ate the plants and the energy was then transferred to their chemical store

Advantages

• The current systems of transport and electricity generation used by human societies rely heavily on fossil fuels, which are generally readily available on a daily basis

• In the past fossil fuels have been reliable for large-scale energy production (although this is changing as supplies deplete and prices rise)

• Efficient - fossil fuels typically have a high energy density (they produce a large amount of energy per kilogram)

Disadvantages

• It takes millions of years for fossil fuels to form:

  • This is why they are considered to be a non-renewable energy resource

• The increasing demand for a decreasing supply causes prices to increase:

  • Fossil fuels are predicted to completely run out within the next 200 years

• Burning fossil fuels pollutes the atmosphere with harmful gases such as:

  • Carbon dioxide, which contributes to the greenhouse effect

  • Sulphur dioxide, which produces acid rain

  • Both carbon and sulphur can be captured upon burning, preventing them from being released into the atmosphere, but this is expensive to do

• Oil spills can occur during transport of fossil fuels, which damage the environment and wildlife over very large areas

• Prices fluctuate rapidly

• Supplies can be affected by conflict and political disagreements (e.g. the war in Ukraine)

Uses of Fossil Fuels

• Fossil fuels are mainly used for:

  • Transport

  • Generating electricity

  • Heating

Transport

• The majority of vehicles in the world are powered by petroleum products such as petrol, diesel and kerosene:

  • These resources all originate from crude oil, which is a fossil fuel

• A growing number of vehicles are now being powered by electricity:

  • The advantage of this is that while the vehicle is being driven, it produces zero carbon emissions

  • The disadvantage is that when the vehicle is being charged, it is connected to the National Grid, which currently uses a combination of renewable and non-renewable energy sources

Electricity generation

• Fossil fuels, such as coal and oil, are used to produce energy on-demand when energy is needed:

  • This is done by burning the materials when the energy is required

  • When coal is burned, it produces thermal energy

• This is used to boil water creating steam

• Steam is forced around the system and this turns a turbine

• The turbine turns coils in a magnetic field in the generator:

  • This generates electricity

• The electricity is transferred through a step-up transformer and is carried out of the system by electrical lines

• The steam within the turbine will cool and condense and then be pumped back into the boiler to repeat the process

Energy Demand

• The demand for energy across the globe is rising

• Population growth and development are the two main causes of the increase in energy demand:

  • The higher demand for food leads to more intensive farming, which requires more energy for machines, light and heat

  • Increasing industry requires energy for heating, lighting and machinery

  • There is more transport, all of which requires energy in the form of petrol, diesel or electricity

  • Urbanisation increases with the development increasing domestic appliances, heating and lighting

  • Increased wealth means people buy more appliances and technology, which require energy

Nuclear Energy

• Energy stored in the nucleus of atoms can be released when the nucleus is broken in two:

  • This is known as nuclear fission

• Nuclear power stations use fission reactions to create steam to turn turbines to generate electricity

• Nuclear power is a low carbon, low-emission, non-renewable resource but is controversial due to the radioactive waste it produces and the potential scale of any accident

Advantages

• No pollution released into atmosphere

• Nuclear reactors are perfectly safe as long as they are functioning properly (rigorous safety checks must be routinely carried out and rigorous safety procedures followed)

• Nuclear power stations can generate electricity reliably on a large scale to be available as needed

• Small amounts of uranium are needed, and large reserves are available

• Reduces reliance on fossil fuels

• Increases energy security

Disadvantages

• Uranium ore found in the ground is used for fission reactions and since there is a finite supply, nuclear power is a non-renewable resource

• Nuclear fuels produce radioactive waste, which needs to be stored for thousands of years

• Safe ways of storing radioactive waste are very expensive

• If an accident occurs at a nuclear reactor, radioactive waste can leak out and spread over large areas

• Cost of decommissioning (shutting down) nuclear power plants is very high

• Nuclear energy is often used in countries who do not have their own supplies of fossil fuels, such as France

• In 2019 approximately 4% of the global primary energy supply was from nuclear power

• There are 439 active nuclear reactors across the world. Most of these are in just five countries:
  

  • USA (92)

  • France (56)

  • China (54)

  • Russia (37)

  • Japan (33)