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Global Energy Capacities

Renewable energy sources are called such because they can be replenished by natural processes within a timescale that humans find useful. This means for the goals of human systems, exhausted resources will recover in an economically calculable period.

Global energy demand has risen dramatically in the past decades. 144 countries had made commitments to a transition to renewable energy through a promotion mechanism by 2013 (48 in 2004).

Global renewable energy statistics:

Generation capacityEnd 2003 /GWEnd 2013 /GW
Total with hydro8001,560
Total w/o hydro85560

Worldwide investment in renewable energy is estimated to have been 214 billion dollars in 2013.

Energy consumption around the world experienced a small decline in the late 1970s, but otherwise has been increasing fairly consistently right through since the advent of the Industrial Revolution. In 2014, 81% of our total primary energy supply depended on burning fossil fuels, namely 29% coal, 31% oil, and 21% natural gas. In terms of final energy consumption electricity only accounted for 18.1%, but was responsible for 35.2% of the total CO2 emissions.

Primary energy

Primary energy (PE) is the form of energy which enters the human system. It is any form of energy, renewable and non-renewable found in nature. After conversion it is known as secondary or tertiary energy. For example, electricity is a secondary form of energy generated by various primary sources (coal, hydro, solar, etc.).

Total primary energy supply (TPES) = sum of production and imports minus exports and inventory changes.

    TPES of fuels and energy sources in 2012:
  • Oil: 31.4%
  • Coal/peat/shale: 29.0%
  • Natural gas: 21.3%
  • Biofuels and waste incineration: 10.0%
  • Nuclear: 4.8%
  • Hydro: 2.4%
  • Others (renewables): 1.1%

(Data source: IEA, 2014)

Fossil fuels: energy, whether electricity generation or fuel for transport or industry, has traditionally been predominantly oil, followed by coal, then gas. Coal plateaued in the 1990s, before resurging between 2005 and the present to be almost at the level of oil. Gas is rising and gaining gradually on the other two fossil fuels. In 1985, gas consumption (c. 15,000 TWh/y) was half that of oil (c. 30,000 TWh/y), and close to coal (c. 22,000 TWh/y). By 2015, gas was two-thirds of oil, 35,000 TWh/y, coal at 44,000 TWh/y, and oil at 50,000 TWh/y.

Renewables worldwide were mainly hydropower and fairly consistent at around 15 TWh/y till the 1980-90s, when an exponential growth began. Renewables are currently at c. 4,000 TWh/y.

The only energy to have shown a decline is nuclear. In the 1980s nuclear was providing just as much energy needs as renewables, but is now less than half.

In 2012 the world energy consumption was 104,426 TWh (= 8,979 mega-tonne of oil equivalent (Mtoe)).This breaks down to:

  • Oil: 40.7%
  • Coal/peat/shale: 10.1%
  • Natural gas: 15.2%
  • Biofuels and waste incineration: 12.4%
  • Electricity: 18.1%
  • Others (renewables): 3.5%

Energy investment around the world decreased 8 per cent from 2014 (c. 2.0 trillion$) to 2015 (c. 1.8 trillion$). Renewables accounted for USD 313 billion (17.4%), while national oil companies enjoyed 44% of upstream investment.

China invested $315 bn in 2015, beating the USA's $280 bn (US investment was down from $355 bn in 2014). The decline in the USA was due mainly to falling investment in oil and gas. Oil and gas however still account for 45% of the total.

The link between energy demand and GDP growth weakened further, due to the greater dominance of the service sector in mature economies (e.g. Europe, Japan, USA).

Energy efficiency saw a rise in investment of 6%, to US$220 bn, stimulated by government policies on minimum standards for buildings, appliances and motor vehicles. However, the trend towards more fuel-efficient vehicles slowed, particularly in the USA, due to low oil prices.

Electricity sector investment reached a record US$690 bn, or 37% of global energy investment. This was despite a slowdown in demand growth due primarily to the expansion of renewables and networks.

Source: http://www.iea.org/Textbase/npsum/WEI2016SUM.pdf


Renewable energy sources are called such because they can be replenished by natural processes within a timescale that humans find useful. This means for the goals of human systems, exhausted resources will recover in an economically calculable period.

Sustainable use of energy would therefore be logically a use of a resource that does not exceed the natural restoration capacity. Fossil resources are utilized far above this limit, so are considered 'non-renewable'.

It is important to note the difference between 'primary energy carrier' and 'secondary energy carrier'. Energy carriers are substances that can release their energy content through energy conversion processes. 'Primary energy carriers' are the energy sources that are available from nature: e.g. fossil fuels (petroleum, coal, natural gas) in their extracted state, uranium, biomass, gravity (e.g., water in dams), kinetic energy (e.g. wind), radiation (e.g. sunlight), thermal (earth crustal heat). Secondary energy carriers are produced only after conversion of primary or other secondary energy sources by humans: e.g. fuels, biofuels, electrical energy: e.g. derived fuels from petroleum cracking (petrol, diesel), ethanol (biofuel), electrical energy, thermal pumps.

Fossil energy sources regenerate over millions of years. Fossil fuels, such as mineral oil, natural gas, and coal, release their chemical energy mainly through combustion. In this process, they cause environmental pollution. Therefore, the popular interpretation of the expression 'non-renewable' has extended beyond 'exhaustive' to include 'dirty' and 'polluting'.

All renewable energy sources are freely available through natural processes. The origin of solar and wind energy is solar radiation. Photovoltaic panels and solar collectors convert the solar radiation directly into electric current or heating. Wind uses the energy of the wind, which is air that is set in motion by solar energy. Hydropower comes from gravity acting on water - water which is lifted by evaporation into clouds by solar radiation.

Tidal energy comes from the effects of the gravity of the moon. Geothermal energy is due to the heat that results from radioactive elements in the earth's mantle.

However, despite the great need for alternatives to fossil fuels, solar, wind, and geothermal plants produce only 3% of the world's electricity. Hydropower, on the other hand, contributes 16%.

Renewable heat is the thermal energy that is extracted from bioenergy, solar thermal energy or geothermal energy. A common (and permissible) synonym for electricity from renewable energy sources is green power.

Solar incident radiation brings 3.9 YJ of energy in to the Earth atmosphere each year.

Annual potential of RE:

  • Solar = 3.9 x 1024 J (3.9 YJ yottajoule). This equates to an average of = 1.236 x 1017 W (0.1236 EW exawatt) constant power over the year.
  • Geothermal = 1.0 x 1021 J (1.0 ZJ zettajoule) = 31.6 x 1012 W (31.6 TW terawatt).
  • Gravitation (tidal) = 94 x 1018 J (94 EJ exajoule) = 2.98 x 1012 W (2.98 TW terawatt).

For comparison, the International Energy Agency IEA estimates that in 2013 the total world energy consumption was 3.89 × 1020 joules (9,301 Mtoe), equal to an average power consumption of 12.3 terawatts.

Hence, total human energy demand is of the order of 0.1% (one-thousandth) of available solar incident energy, 39% of geothermal energy, and 4.1 times available tidal energy. Note that solar energy produces wind and wave energy sources as well.