Feature Report: Understanding Electricity

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Electricity Generation and Related CO2 Emissions

Electricity is essential for industry, buildings and all aspects of daily life. But it has to be generated from a primary energy source, such as coal, natural gas, uranium, the sun, wind or water. The methods used to produce electricity also make it the main source of global CO2 emissions. For this reason, the choice of generation technology will play a decisive role in reducing electricity's environmental footprint, especially considering that coal, at one end of the spectrum, has a carbon impact 20 times greater than renewables, at the other.  

Electricity is used in a wide variety of areas including industry, housing and transportation, such as here for a tram in the city of Toulouse.
©EDF / GROLLIER PHILIPPE

Electric current is created by the movement of electrons. Today, the most widespread technique used to generate this current is still the conversion of mechanical movement into electrical energy. This is typically achieved by rotating a turbine connected to a generator, which causes a conductor to move through a magnetic field that attracts the electrons. The turbine is usually driven either by steam, made from heating water in various types of fossil-fuel-fired powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... plants, or by renewable energies such as wind and water.

41%: The share of CO2 emissions caused by electricity generation.

The Different Generation Methods

Combustion power plants, which burn fossil fuels (coalCoal is ranked by its degree of transformation or maturity, increasing in carbon content from..., oil or natural gas) or biomassIn the energy sector, biomass is defined as all organic matter of plant or animal origin... (household waste or plant matter), are the most widespread type of power station and the least expensive to build. Coal-fired plants are the most common, currently generating more than 40% of the world's electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... – but also emitting the most co2See Carbon Dioxid per kilowatt-hour (kWh). Large countries such as China and India rely primarily on coal for their electricity.

Nuclear power plants function on the heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter... produced by fissioning atoms of uranium-235 or plutonium-239. Concentrated solar power technology harnesses the heat of the sun, which is amplified by mirrors.

However, turbines can also be driven by other sources of mechanical energySum of the potential energy and kinetic energy of an object or system..., such as water and wind. Hydropower plants use the energy of water as it tumbles from natural waterfalls or is moved by dams, tides or currents. Wind turbines capture the wind's energy with their enormous blades and use it to spin turbines. A group of typically five-to-fifty wind turbines is called a wind farm.

Several emerging technologies exploit the energy of the ocean. Wave powerWave power involves capturing the energy of ocean waves to generate electricity... can be captured using a variety of systems, such as huge buoys that rise and fall with the swell and large tube sections installed on the water's surface. Underwater turbines work similarly to their onshoreRefers to land-based oil exploration and production operations, as in "onshore seismic data acquisition" or "onshore drilling". counterparts, only they are driven by ocean currents instead of wind. Other technologies are being developed to make use of temperature differences at various depths of the ocean.

Lastly, solar photovoltaic (PV) power plants, or solar farms, consist of arrays of solar panels (covered in a semiconductor material, such as siliconSilicon crystals come from silica, the main compound in quartz and sand. Silicon is a semi-conducting material.) that convert sunlight directly into electricity. This technology should not be confused with solar thermal systems, which mainly use the heat of the sun to rotate turbines.

A coal-fired power plant emits over 40 times more CO2 than a hydropower plant.

Output Could Double by 2040

Global electricity generation is constantly increasing, as evidenced by the three-fold rise between 1973 and 2013 to 23,318 terawatt-hours (1012 watt-hours)1. Of this amount, 41% is produced from coal, 22% from gas, 16% from hydropower, 11% from nuclear power, 4% from oil and a mere 6% from renewables (biomass as well as geothermalDescribes the technology used to tap subsurface heat to produce energy..., wind and solar power), which remain marginal despite making progress.

China is the world's largest generator of electricity (24% of global output), followed by the United States (18.3%), India (5.1%), Russia (4.5%) and Japan (4.5%), then by Canada, Germany, Brazil, France and South Korea.

Electricity needs have soared as a result of population growth and economic development, with global power generation increasing by 2.2% a year and expected to double by 20402. This is even faster than primary energyAll energy sources that have not undergone any conversion process and remain in their natural state.. consumption, which is only projected to rise by 47%. India and China in particular are forecast to step up their power generation by 261% and 177%, respectively, between now and 2030.

Electricity is essential to households and businesses alike. The residential and commercial sector, including farming and public services, absorbs 56.2% of electricity output to power such things as home appliances, electronic devices, televisions, lighting, heating and air conditioning. Industry uses 42.3% to run electric motors, cool IT servers, and keep production lines running. Transportation currently consumes just 1.5% due to its heavy reliance on gasoline and dieselDiesel is the name of an internal combustion engine that works by compression-ignition....

Electricity and Greenhouse Gases

Electricity generation is responsible for 42.5% of global CO2 emissions. Of this, 73% can be attributed to coal-fired power plants, which emit 950 grams of CO2 for every kilowatt-hour of electricity they generate, compared with 350 grams for gas-fired power plants3. For power plants that run on renewable energies, such as hydro, wind, solar PV and solar thermal, the only CO2 emissions are attributable to their construction. Accordingly, for every kilowatt-hour of electricity generated, a solar PV system "emits" between 60 and 150 grams of CO2 (depending on where the solar panels were manufactured), a wind turbine between 3 and 22 grams, and a hydropower plant 4 grams. As for nuclear power plants, even after the future need to dismantle aging facilities is factored in, CO2 emissions still only represent 6 grams per kilowatt-hour of electricity generated – a stark contrast with the 950 grams emitted by coal-fired power plants.

Electricity generated from renewable sources has a much smaller impact on the environment and is virtually inexhaustible, which is why it is attracting new investment. In 2015, for the first time, investment in new renewables capacity, at $266 billion, was more than double the $130 billion invested in coal- and gas-fired power plants4.

While nuclear power only emits a small amount of CO2, some countries refuse to use it for fear of nuclear accidents and radioactive waste, especially after the 2011 Fukushima disaster in Japan. Other countries, including the United Kingdom and China, are investing heavily in new-generation nuclear plants. France, meanwhile, manages to generate its electricity while only making a small carbon impact thanks to its many nuclear and hydropower plants.