About Energy Systems

Reports describing energy systems of the world and countries are readily available but compromised. BP’s ‘Statistical Review of World Energy'1 doesn’t fully account for biofuels, groups together some sources of non-combustible energy, and doesn’t list electricity trade. The IEA does separately list all energy sources and trade,2 but relies on calculations that relatively exaggerate the contribution of nuclear energy. This site overcomes these deficiencies using conventional methods described below.

A representation of a country’s energy system, or that of the world, is shown in figure 1.3 4 5

Figure 1. Representation of an energy system.

Fundamentally, studies and the IEA use the term ‘total primary energy supply’ (TPES) to describe, or account for energy in its primary form prior to any conversions such as coal to electricity, whereas energy in forms purchased and used by the consumer is accounted for separately as ‘total final consumption’ (TFC). A profile can be determined for each, for any country or the world. For simplicity this website uses the terms ‘energy supply’ and ‘energy consumption’ respectively.

Energy supplied by renewables cannot be directly compared with energy supplied by fossil fuels because renewables have natural forms of primary energy (i.e. sun, wind etc). For example, the quantity of kinetic energy in wind can’t be directly measured and compared to the quantity of coal or other combustible fuels. To overcome this, for each renewable energy source, an equivalent quantity of primary energy is determined. This allows the primary energy supplied by both combustible and non-combustible (i.e. renewable) energy sources to be compared. This is conventionally done by calculating for each quantity of renewable electricity, the quantity of primary energy that would be required to be input to a thermal (fossil fuelled) power station of average efficiency, in order to output an equivalent amount of electricity. This is one of three methods of ‘primary energy equivalency'6 named the substitution method, whereby the energy supplied by non-combustible sources is expected to have substituted thermal generation. This measures progress of the transition away from the supply of combustible energy to that of non-combustible energy, and is the method endorsed by the German Advisory Council on Global Change.7 Therefore, on this site, the quantity of energy shown for each non-combustible energy supply is that which would be required to be input to a thermal power station of average efficiency in order to generate an equivalent amount of electricity, or heat as the case may be. This is displayed below –

Figure 2. Calculation of TPES using the substitution method for representing the supply of energy from non-combustible sources.

The quantity of electricity and heat from each non-combustible source is divided by the average efficiency of a fleet of thermal power stations,8 thereby calculating the amount of energy that would need to be input to a thermal power station to produce an equivalent amount of electricity.9

For validation of this website’s methods, the world energy supply (TPES) from this site is compared below with that from the IPCC’s AR5. Both rely on IEA data for year 2010 and compare favourably (they are not exactly the same because the IEA annually applies quality control methods to historical data, and the IPCC used IEA data published in 2012 and this site used IEA data published in 2017).

Chart 1. World energy system (TPES), year 2010, substitution method of primary energy equivalency, comparison of this website’s results with those from IPCC AR5 WG3, Annex 2 Metrics & Methodology.10

Large numbers used on this website are expressed using prefixes. Commonly used metric prefixes are listed in table 1(a) below, and units in 1(b) –

Table 1. Explanation of (a) Prefixes, and (b) Units.
  1. https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy/downloads.html()
  2. https://www.iea.org/statistics/()
  3. J.M.K.C. Donev et al. (2017). Energy Education – Total primary energy supply [Online]. Available: https://energyeducation.ca/encyclopedia/Total_primary_energy_supply [Accessed: February 20, 2019].()
  4. The International Energy Agency (IEA) statistics overview()
  5. Macknick, Jordan. “Energy and CO2 emission data uncertainties.” Carbon Management 2, no. 2 (2011): 189-205.()
  6. Section A.II.4, Primary Energy Accounting, WG3, AR5()
  7. Future Bioenergy and Sustainable Land Use By Renate Schubert, German Advisory Council on Global Change()
  8. Footnote of Table A.II.10, WG3, AR5()
  9. The other two methods of primary energy equivalency are the direct method and the physical energy content method. The direct method is used by UN and directly compares quantities of energy from combustible and non-combustible sources, which is only useful for future scenarios where relatively large quantities of non-combustible energy may be supplied. The physical energy content method is used by the IEA and applies the following weights to non-combustible energy supplies causing nuclear energy to be relatively exaggerated: Nuclear = 33%, Geothermal heat = 50%, Geothermal electricity = 10%, Solar thermal heat = 100%, Solar thermal electricity = 33%, Hydro, wind, marine and solarPV = 100%. ()
  10. table A.II.10, p. 1294, Krey V., O. Masera, G. Blanford, T. Bruckner, R. Cooke, K. Fisher-Vanden, H. Haberl, E. Hertwich, E. Kriegler, D. Mueller, S. Paltsev, L. Price, S. Schlömer, D. Ürge-Vorsatz, D. van Vuuren, and T. Zwickel, 2014: Annex II: Metrics & Methodology. In:Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_annex-ii.pdf()