Renewable & Alternative Energy Sources

Renewable & Alternative Energy Sources

What are Renewable Energy Sources?

• Sources of energy with lower carbon dioxide emissions than fossil fuels include renewable energy sources

• Renewable energy are energy sources that will not run out and include:

  • Solar

  • Biomass

  • Hydropower

  • Wind

  • Wave and tidal

  • Geothermal

• 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:

Solar

• 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)

Solar PV panels use energy from sunlight to produce electricity

Solar thermal panels

• Solar thermal panels transfer energy from sunlight to the thermal store of the solar panels which is used to heat water in the pipes

  • Solar panels can be used to warm domestic water supplies

  • This can reduce the cost of producing hot water since it is heated partially by solar panels

   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 thermal panels produce no greenhouse gases or pollution once they are operating

• Solar thermal panels can cut the cost of energy bills for households

   Disadvantages

• Additional energy (e.g. from fossil fuels) is still needed to heat water to a higher temperature in domestic households

• In many places on Earth sunlight is not a reliable energy resource (the sun doesn't shine regularly enough to justify the set-up costs)

Solar thermal panels use energy from sunlight to heat water directly

Biomass

• 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)

Plants take in carbon dioxide during photosynthesis, but carbon dioxide is released back into the atmosphere when biofuels are burned

Hydropower

• 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

A hydroelectric dam transfers the gravitational potential energy of the water to kinetic energy in order to generate electricity

Wind

• 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

Photo by Zbynek Burival on Unsplash 

A wind farm in Austria - some people think wind turbines are an eye-sore, especially when installed in large numbers

Wave and tidal

• 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

Underwater turbines generate electricity from the movement of waves

Tidal barrages can generate electricity from the movement of water, both as the tide comes in and as it goes out again

Geothermal

• 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

Cold water is heated by natural geothermal energy underground, and then returned as hot water or steam, which can be used to generate electricity

Nuclear

• 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 fission occurs when a large nucleus is broken into two smaller nuclei, releasing large amounts of energy

• 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)

Share of electricity production from nuclear power plants