primary energy#Conversion to energy carriers (or secondary energy)
{{Short description|Energy form not subjected to any human conversion process}}
{{Other uses|PE (disambiguation){{!}}PE}}
{{Wikipedia:Latest world total primary energy consumption by type}}
{{Pie chart
| thumb = right
| caption = World total primary energy supply of 162,494 TWh (or 13,792 Mtoe) by region in 2017 (IEA, 2019)
{{cite web
|title = 2019 Key World Energy Statistics
|date = 2019
|publisher = IEA
|url = https://webstore.iea.org/download/direct/2831?fileName=Key_World_Energy_Statistics_2019.pdf
}}
| other =
| label1 = OECD
| value1 = 38
| color1 = #66CCFF
| label2 = Middle East
| value2 = 5.4
| color2 = #FFFF57
| label3 = Non-OECD Europe /Eurasia
| value3 = 8.0
| color3 = #009a39
| label4 = China
| value4 = 22
| color4 = #de2821
| label5 = Non-OECD Asia (w/o China)
| value5 = 13.4
| color5 = pink
| label6 = Non-OECD Americas
| value6 = 4.4
| color6 = #211873
| label7 = Africa
| value7 = 5.8
| color7 = #ef8e39
| label8 = Bunkers (marine/air)
| value8 = 3
| color8 = #313c42
}}
Primary energy (PE) is the energy found in nature that has not been subjected to any human engineered conversion process. It encompasses energy contained in raw fuels and other forms of energy, including waste, received as input to a system. Primary energy can be non-renewable or renewable.
Total primary energy supply (TPES) is the sum of production and imports, plus or minus stock changes, minus exports and international bunker storage.{{cite book|url=https://read.oecd-ilibrary.org/economics/oecd-factbook-2013_factbook-2013-en#page110|page=108|title=OECD Factbook 2013: Economic, Environmental and Social Statistics|year=2012|publisher=OECD Publishing|last=OECD|doi=10.1787/factbook-2013-en|isbn=9789264177062 |access-date=16 August 2021}}
The International Recommendations for Energy Statistics (IRES) prefers total energy supply (TES) to refer to this indicator.{{cite book |last1=Department of Economic and Social Affairs |title=International Recommendations for Energy Statistics |date=2018 |publisher=United Nations |location=New York|url=https://unstats.un.org/unsd/energystats/methodology/documents/IRES-web.pdf |page=105,137}} These expressions are often used to describe the total energy supply of a national territory.
Secondary energy is a carrier of energy, such as electricity. These are produced by conversion from a primary energy source.
Primary energy is used as a measure in energy statistics in the compilation of energy balances,{{cite web |title=Primary energy |url=https://www.eia.gov/tools/glossary/index.php?id=P |website=Glossary |publisher=U.S. Energy Information Agency |access-date=18 August 2021 |location=Washington, DC}} as well as in the field of energetics. In energetics, a primary energy source (PES) refers to the energy forms required by the energy sector to generate the supply of energy carriers used by human society.{{cite book |last1=Giampietro |first1=Mario |last2=Mayumi |first2=Kozo |title=The Biofuel Delusion: The Fallacy of Large Scale Agro-Biofuels Production |publisher=Earthscan, Taylor & Francis group |year=2009 |pages=336 |isbn=978-1-84407-681-9 }} Primary energy only counts raw energy and not usable energy and fails to account well for energy losses, particularly the large losses in thermal sources. It therefore generally grossly overcounts the usefulness of thermal renewable energy sources and by comparison undercounts sources like renewables that produce secondary energy.
Examples of sources
File:Global primary energy consumption by source 1900 - 2021.png
File:Global fossil fuel vs. low-carbon primary energy consumption, OWID.svg
Primary energy sources should not be confused with the energy system components (or conversion processes) through which they are converted into energy carriers.
Usable energy
{{main|exergy}}
File:Different energy forms (PES).png
Primary energy sources are transformed in energy conversion processes to more convenient forms of energy that can directly be used by society, such as electrical energy, refined fuels, or synthetic fuels such as hydrogen fuel. In the field of energetics, these forms are called energy carriers and correspond to the concept of "secondary energy" in energy statistics.
=Conversion to energy carriers (or secondary energy)=
Energy carriers are energy forms which have been transformed from primary energy sources. Electricity is one of the most common energy carriers, being transformed from various primary energy sources such as coal, oil, natural gas, and wind. Electricity is particularly useful since it has low entropy (is highly ordered) and so can be converted into other forms of energy very efficiently. District heating is another example of secondary energy.[https://www.energystar.gov/buildings/facility-owners-and-managers/existing-buildings/use-portfolio-manager/understand-metrics/difference U.S. EPA Energy STAR] Retrieved 2017-11-03
According to the laws of thermodynamics, primary energy sources cannot be produced. They must be available to society to enable the production of energy carriers.
Conversion efficiency varies. For thermal energy, electricity and mechanical energy production is limited by Carnot's theorem, and generates a lot of waste heat. Other non-thermal conversions can be more efficient. For example, while wind turbines do not capture all of the wind's energy, they have a high conversion efficiency and generate very little waste heat since wind energy is low entropy. In principle solar photovoltaic conversions could be very efficient, but current conversion can only be done well for narrow ranges of wavelength, whereas solar thermal is also subject to Carnot efficiency limits. Hydroelectric power is also very ordered, and converted very efficiently. The amount of usable energy is the exergy of a system.
=Site and source energy=
Site energy is the term used in North America for the amount of end-use energy of all forms consumed at a specified location. This can be a mix of primary energy (such as natural gas burned at the site) and secondary energy (such as electricity). Site energy is measured at the campus, building, or sub-building level and is the basis for energy charges on utility bills.{{cite web|title=Measuring energy: site energy vs. source energy in ENERGY STAR Portfolio Manager|date=28 March 2017 |url=http://www.nrcan.gc.ca/energy/efficiency/buildings/energy-benchmarking/update/getready/19453|publisher=Natural Resources Canada|access-date=November 8, 2017}}
Source energy, in contrast, is the term used in North America for the amount of primary energy consumed in order to provide a facility's site energy. It is always greater than the site energy, as it includes all site energy and adds to it the energy lost during transmission, delivery, and conversion.{{Cite journal|last1=Torcellini|first1=Paul|last2=Pless|first2=Shanti|last3=Deru|first3=Michael|last4=Crawley|first4=Drury|date=June 2006|title=Zero energy buildings: a critical look at the definition|url=https://www.nrel.gov/docs/fy06osti/39833.pdf|journal=ACEEE Summer Study|publisher=National Renewable Energy Laboratory/U.S. Department of Energy}} While source or primary energy provides a more complete picture of energy consumption, it cannot be measured directly and must be calculated using conversion factors from site energy measurements. For electricity, a typical value is three units of source energy for one unit of site energy.{{cite web|title=Site Energy vs Source Energy|url=http://wbi.worldbank.org/energy/content/site-energy-vs-source-energy|publisher=The World Bank|access-date=November 8, 2017}} However, this can vary considerably depending on factors such as the primary energy source or fuel type, the type of power plant, and the transmission infrastructure. One full set of conversion factors is available as technical reference from Energy STAR.{{Cite web|url=https://portfoliomanager.energystar.gov/pdf/reference/Source%20Energy.pdf|title=Technical Reference: Source Energy|access-date=2017-11-09}}
Either site or source energy can be an appropriate metric when comparing or analyzing energy use of different facilities. The U.S Energy Information Administration, for example, uses primary (source) energy for its energy overviews{{Cite web|url=https://www.eia.gov/totalenergy/|title=Total Energy - U.S. Energy Information Administration (EIA)|website=www.eia.gov|access-date=2017-11-09}} but site energy for its Commercial Building Energy Consumption Survey{{Cite web|url=https://www.eia.gov/consumption/commercial/terminology.php|title=Commercial Buildings Energy Consumption Survey (CBECS) - U.S. Energy Information Administration (EIA)|website=www.eia.gov|language=en|access-date=2017-11-09}} and Residential Building Energy Consumption Survey.{{Cite web|url=https://www.eia.gov/consumption/residential/terminology.php|title=Residential Energy Consumption Survey (RECS) - U.S. Energy Information Administration (EIA)|website=www.eia.gov|language=en|access-date=2017-11-09}} The US Environmental Protection Agency's Energy STAR program recommends using source energy,{{Cite web|url=https://www.energystar.gov/buildings/facility-owners-and-managers/existing-buildings/use-portfolio-manager/understand-metrics/difference|title=The difference between source and site energy|website=www.energystar.gov|language=en|access-date=2017-11-09}} and the US Department of Energy uses site energy in its definition of a zero net energy building.{{Cite web|url=https://energy.gov/eere/buildings/articles/doe-releases-common-definition-zero-energy-buildings-campuses-and|title=DOE Releases Common Definition for Zero Energy Buildings, Campuses, and Communities|website=Energy.gov|access-date=2017-11-20}}
Conversion factor conventions
File:Energy_Flow_US_2016.png for the United States 2016 shows that 66.4% of primary energy ends up as waste heat]]
Where primary energy is used to describe fossil fuels, the embodied energy of the fuel is available as thermal energy and around two thirds is typically lost in conversion to electrical or mechanical energy. There are very much less significant conversion losses when hydroelectricity, wind and solar power produce electricity, but today's UN conventions on energy statistics counts the electricity made from hydroelectricity, wind and solar as the primary energy itself for these sources. One consequence of employing primary energy as an energy metric is that the contribution of hydro, wind and solar energy is under reported compared to fossil energy sources, and there is hence an international debate on how to count energy from non-thermal renewables, with many estimates having them undercounted by a factor of about three.{{cite web|last1=Sauar|first1=Erik|title=IEA underreports contribution solar and wind by a factor of three compared to fossil fuels|url=http://energypost.eu/iea-underreports-contribution-solar-wind-factor-three-compared-fossil-fuels/|website=energypost.eu|date=31 August 2017 |publisher=Energy Post|access-date=22 April 2018}} The false notion that all primary energy from thermal fossil fuel sources has to be replaced by an equivalent amount of non-thermal renewables (which is not necessary as conversion losses do not need to be replaced) has been termed the "primary energy fallacy".
See also
Notes
References
{{reflist|30em}}
Further reading
- Kydes, Andy (Lead Author); Cutler J. Cleveland (Topic Editor). 2007. "Primary energy." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth June 1, 2006; Last revised August 14, 2007; Retrieved November 15, 2007.
- {{cite book
| last1 = Øvergaard | first1 = Sara
| title = Definition of primary and secondary energy
| date = September 2008
| publisher = Statistics Norway
| location = Norway
| url = http://unstats.un.org/unsd/envaccounting/londongroup/meeting13/LG13_12a.pdf
| access-date = 2016-12-17
}}
External links
- [https://editors.eol.org/eoearth/wiki/Primary_energy The Encyclopedia of Earth: Primary energy]
- [https://web.archive.org/web/20120127193231/http://ourenergyfutures.org/page-cid-7.html#Primary_Energy_Sources Our Energy Futures glossary: Primary Energy Sources]
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