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energy>Ethan.boechler at 20:45, 10 September 2021

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	[[category:Lecture 1B_Human_effects]]		[[category:Lecture 1B_Human_effects]]
	[[Category:Done 2020-02-29]]		[[Category:Done 2020-02-29]]
			[[Category:Translated to Spanish]]
			[[es:Flujo de energía primaria]]
			[[Category:Translated to French]]
			[[fr:Flux d'énergie primaire]]
	[[File:sunlight2.jpg\|400px\|framed\|right\|Figure 1. Sunlight is a crucial part of life on Earth. It's also a flow of energy from the Sun to the Earth, providing most of the energy for other flows as well like wind and hydropower.<ref>Pixabay. (May 20, 2015). ''Sunlight'' [Online]. Available: http://pixabay.com/en/sunlight-sky-daylight-summer-422710/</ref>]]		[[File:sunlight2.jpg\|400px\|framed\|right\|Figure 1. Sunlight is a crucial part of life on Earth. It's also a flow of energy from the Sun to the Earth, providing most of the energy for other flows as well like wind and hydropower.<ref>Pixabay. (May 20, 2015). ''Sunlight'' [Online]. Available: http://pixabay.com/en/sunlight-sky-daylight-summer-422710/</ref>]]
	<onlyinclude>A '''primary energy flow''' (or within the energy education site '''primary flow''' or just '''flow''') refers to natural processes with [[energy]] that can be extracted and transformed in a useful way. Primary energy flows include solar [[radiation]] shining on the [[Earth]] from the [[Sun]], or [[water]] flowing downstream in a river. The energy in these primary flows can be harnessed to provide [[energy service]]s such as [[home heating]], [[transportation]] and [[electrical generation]].</onlyinclude><ref>Wolfson, ''Energy, Environment and Climate,'' Second edition. New York, USA: W.W. Norton, 2010</ref>		<onlyinclude>A '''primary energy flow''' (or within the energy education site '''primary flow''' or just '''flow''') refers to natural processes with [[energy]] that can be extracted and transformed in a useful way. Primary energy flows include solar [[radiation]] shining on the [[Earth]] from the [[Sun]], or [[water]] flowing downstream in a river. The energy in these primary flows can be harnessed to provide [[energy service]]s such as [[home heating]], [[transportation]] and [[electrical generation]].</onlyinclude><ref>Wolfson, ''Energy, Environment and Climate,'' Second edition. New York, USA: W.W. Norton, 2010</ref>

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energy>Jmdonev at 21:05, 10 April 2020

2020-04-10T21:05:22Z

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[[category:371 topics]]
[[category:Lecture 1B_Human_effects]]
[[Category:Done 2020-02-29]]
[[File:sunlight2.jpg|400px|framed|right|Figure 1. Sunlight is a crucial part of life on Earth. It's also a flow of energy from the Sun to the Earth, providing most of the energy for other flows as well like wind and hydropower.<ref>Pixabay. (May 20, 2015). ''Sunlight'' [Online]. Available: http://pixabay.com/en/sunlight-sky-daylight-summer-422710/</ref>]]
<onlyinclude>A '''primary energy flow''' (or within the energy education site '''primary flow''' or just '''flow''') refers to natural processes with [[energy]] that can be extracted and transformed in a useful way. Primary energy flows include solar [[radiation]] shining on the [[Earth]] from the [[Sun]], or [[water]] flowing downstream in a river. The energy in these primary flows can be harnessed to provide [[energy service]]s such as [[home heating]], [[transportation]] and [[electrical generation]].</onlyinclude><ref>Wolfson, ''Energy, Environment and Climate,'' Second edition. New York, USA: W.W. Norton, 2010</ref>

Primary energy flows are one of two broad types of energy humans harvest from nature ([[primary energy]]), the other being [[primary fuel]]s. Just like with primary fuels, most of the energy in the Earth's primary energy flows come either directly from the [[Sun]] or indirectly from the Sun (see [[Earth's energy flow]]). Primary flows tend to be diffuse (low [[energy density]]) which can lead to surprising [[environmental impact]]s. It is difficult to compare the energy density or environmental impact of primary flows to fuels (see [[fuel vs flow | primary fuel vs. primary flow]]). When people talk about energy conservation, usually they mean using less of the energy from these primary flows or [[fuel]]s (see [[fuel conservation]]).

Primary energy flows include harnessing [[wind power]], [[solar power]] (both [[photovoltaic system | photovoltaic]] and [[solar thermal power plant|solar thermal]]), [[hydropower]], [[energy from ocean waves|wave power]], [[tidal power]] and [[geothermal energy|geothermal]] power. Because flows take advantage of energy in Earth's systems, flows tend to replenish their energy supply. This is why flows are usually thought of as renewable, and often sustainable (see [[renewable and sustainable energy]]). Despite this, it is possible to use primary flows unsustainably, which has specifically been a problem with geothermal energy.

At the moment energy accounting only keeps track of primary flows that are used for harnessing power for power's sake like generating [[electricity]]. There's a fair amount of [[power]] taken from primary flows that don't get formally accounted for. For example sailing ships use wind and many ships using tides (which is different from the electrical generation of [[tidal power]]). The largest flow used is of course [[sunlight]], and the biggest way that's used is by keeping the Earth at a comfortable living [[temperature]].

The amount of [[solar energy|energy from sunlight]] is enormous, but mostly it goes towards keeping the [[atmosphere]] at a livable temperature, evaporating [[water]] for the [[hydrologic cycle]] and driving [[wind]]. Because this total flow of solar energy is thousands of times greater than the total energy use by humans many people advocate for using more solar energy. The difficulty with this energy is that it's delivered over a very wide area (it's very diffuse) and impossible (and expesnive) to catch it all, but it is there.

By formal reckoning, primary flows provide only a small fraction (~5%) of today's [[primary energy]], see figure 1. Almost all of this energy is going into [[electricity generation]]. Due to peculiarities of [[thermodynamics]], primary flows generate practically no [[waste heat]] (using fuels in a [[heat engine]] creates waste heat). All the energy successfully harvested from the primary flow is used for generating electricity (see [[Betz limit]] for why not all of the energy can be harvested for wind power). This means that despite being only ~5% of the primary energy, flows make up ~20% of electrical generation, the bulk of which is hydro and with wind being the second largest contributor. Different countries have very different energy mixes, please see [[electricity generation]] for a detailed map of where different countries get their electricity from.

<html><iframe class="data-visualization topic-Production offset-Flows" id='oecd-pie'></iframe></html>

Figure 1. Only a small fraction, shown as the extracted pie pieces, of the world's energy comes from primary flows. Most of this energy comes from [[hydropower]], although a small fraction is [[wind power]], [[solar power]], [[geothermal energy]], and [[tidal power]]. Since primary flows usually go into electricity, the percent of electricity generated by primary flows is ~20% (still mostly hydro) because flows don't have the same limitations of having a [[thermal efficiency]]'s that [[heat engine]]s have and flows are used almost entirely for electricity generation.

==Potential confusion==
People occasionally confuse energy flows with other concepts that are related:
*[[Electricity]] is flowing energy, but it is '''not''' a flow in this sense. Electricity is produced through energy transformations from primary energy. It's not itself a primary energy form but an [[energy currency]].

*[[Heat]] is flowing energy. Specifically, it's thermal energy flowing from hot to cold. This is tricky, because there are times when heat can be considered a primary energy source, when taking geothermal energy from the ground. Likewise, when using the Sun's heat, that would be a flow. When something is merely hot and giving off heat, like a fire, that's not a flow.

*There are also [[material flow]]s, which aren't energy at all. This refers to how certain materials, like [[metal]]s, move through the world's economy. This isn't primary energy, so it's not a flow.

==References==
{{reflist}}
[[Category:Uploaded]]

Primary energy flow - Revision history

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energy>Ethan.boechler at 20:45, 10 September 2021

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energy>Jmdonev at 21:05, 10 April 2020