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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