posts_gdocs: 1GIW9wdZxEVlCp76-UD86ZgnMmzztgC3aIN3Y33qb3fM
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1GIW9wdZxEVlCp76-UD86ZgnMmzztgC3aIN3Y33qb3fM | energy-substitution-method | article | { "toc": [ { "slug": "undefined-fossil-fuel-energy-is-measured-differently-from-renewable-electricity", "text": "Fossil fuel energy is measured differently from renewable electricity", "title": "Fossil fuel energy is measured differently from renewable electricity", "isSubheading": false }, { "slug": "undefined-the-substitution-primary-energy-method", "text": "The \u2018substitution\u2019 primary energy method", "title": "The \u2018substitution\u2019 primary energy method", "isSubheading": false }, { "slug": "undefined-the-difference-between-substitution-and-direct-primary-energy", "text": "The difference between \u2018substitution\u2019 and \u2018direct\u2019 primary energy", "title": "The difference between \u2018substitution\u2019 and \u2018direct\u2019 primary energy", "isSubheading": false } ], "body": [ { "type": "text", "value": [ { "text": "Understanding the breakdown of our energy systems \u2013 how much energy we get from coal, oil or gas, how much from nuclear, solar or wind \u2013 is crucial. It lets us compare energy mixes across the world and track progress on decarbonization.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "But summarizing global energy with just ", "spanType": "span-simple-text" }, { "children": [ { "text": "one", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " metric is not simple. Researchers used a range of measures that tell us different things. There are four different measures, which capture the transformations and losses that occur across the energy chain: primary, secondary, final, or useful energy. I write about these in ", "spanType": "span-simple-text" }, { "url": "https://ourworldindata.org/energy-definitions", "children": [ { "text": "another article", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ", and summarize them in the chart below.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "size": "wide", "type": "image", "filename": "Four-ways-of-measuring-energy.png", "parseErrors": [] }, { "type": "text", "value": [ { "text": "But a further problem is that energy sources are often reported in commodity markets and some of the most commonly-used datasets using ", "spanType": "span-simple-text" }, { "children": [ { "text": "different", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " metrics.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "In this article I focus on various ways in which \u2018primary energy\u2019 is measured. I explain how different energy sources are quantified in these datasets, and what adjustments are made to make them more comparable.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "text": "Fossil fuel energy is measured differently from renewable electricity", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "Energy from fossil fuels \u2013 coal, oil and gas \u2013 are usually measured as ", "spanType": "span-simple-text" }, { "children": [ { "text": "primary", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " energy. That is, the amount of energy that\u2019s generated when they are burned in their raw form. For coal, it\u2019s the total amount of energy you get when you burn it.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "But, a large amount of this raw energy is wasted as heat. A ", "spanType": "span-simple-text" }, { "url": "https://www.energy.gov/fecm/transformative-power-systems", "children": [ { "text": "typical coal plant in the US", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " has an efficiency of 33%.", "spanType": "span-simple-text" }, { "url": "#note-1", "children": [ { "children": [ { "text": "1", "spanType": "span-simple-text" } ], "spanType": "span-superscript" } ], "spanType": "span-ref" }, { "text": " Only one-third generates electricity, and the other two-thirds is wasted as heat. You need to burn three units of coal to get one unit of electricity.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Gas electricity is slightly better, with ", "spanType": "span-simple-text" }, { "url": "https://www.eia.gov/todayinenergy/detail.php?id=44436", "children": [ { "text": "an efficiency", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " of around 45%. Put two units of gas energy in, and you get ", "spanType": "span-simple-text" }, { "children": [ { "text": "almost", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " one unit of electricity out.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "size": "narrow", "type": "image", "filename": "efficiency-coal-gas-plants.png", "parseErrors": [] }, { "type": "text", "value": [ { "text": "In popular datasets, such as the ", "spanType": "span-simple-text" }, { "children": [ { "url": "https://www.energyinst.org/statistical-review", "children": [ { "text": "Statistical Review of World Energy", "spanType": "span-simple-text" } ], "spanType": "span-link" } ], "spanType": "span-italic" }, { "text": ", published by the Energy Institute (it was formerly published by BP), coal and gas are reported in their primary energy terms \u2013 as the fuels going ", "spanType": "span-simple-text" }, { "children": [ { "text": "into", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " the power plant.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "But this is not how renewable electricity \u2013 such as solar and wind is recorded. It\u2019s reported in terms of its electricity output.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Think about what this means. We\u2019re comparing the amount of energy generated by fossil fuels ", "spanType": "span-simple-text" }, { "children": [ { "text": "with", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " all of the wasted heat, to the amount generated by renewables ", "spanType": "span-simple-text" }, { "children": [ { "text": "without", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " this wastage. If you were to replace the electricity from coal and gas with renewables, the energy requirements would be much lower.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "text": "The \u2018substitution\u2019 primary energy method", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "To \u2018correct\u2019 for these different methods of accounting, researchers can apply the \u2018substitution method\u2019. This tries to adjust non-fossil energy sources to the inputs that would be needed if it was generated from fossil fuels. It assumes that wind and solar electricity is as inefficient as coal or gas.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "This adjustment is fairly crude. Non-fossil electricity generation is divided by a \u2018thermal efficiency factor\u2019, which is the average efficiency of fossil electricity. In the chart, we see the factor that the Energy Institute applies. This factor has changed over time due to changes in the composition of the fossil fuel mix (the split between coal and gas), and efficiency improvements in power plants over time.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "url": "https://ourworldindata.org/grapher/thermal-efficiency-factor", "type": "chart", "parseErrors": [] }, { "type": "text", "value": [ { "text": "Let\u2019s say that a country produces 100 terawatt-hours (TWh) of electricity from solar, and the thermal efficiency factor is 0.4. To get the \u2018primary energy equivalents\u2019 we divide 100 TWh by 0.4. That\u2019s 250 TWh.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "What this means is that if this electricity was produced by fossil fuels, we\u2019d need 250 TWh of energy ", "spanType": "span-simple-text" }, { "children": [ { "text": "in", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " to get 100 TWh of electricity ", "spanType": "span-simple-text" }, { "children": [ { "text": "out", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ".", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "In the substitution method, non-fossil electricity sources are divided by this efficiency factor.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "The same is done for nuclear. In reality, nuclear does experience thermal losses in a power plant, just like fossil fuels. It has ", "spanType": "span-simple-text" }, { "url": "https://www.world-nuclear.org/uploadedFiles/org/WNA/Publications/WNA_Position_Statements/PS-cooling.pdf", "children": [ { "text": "a thermal efficiency", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " ranging from around 33% to 40%. But since it\u2019s reported in terms of electricity ", "spanType": "span-simple-text" }, { "children": [ { "text": "output", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ", we need to do this adjustment to calculate its equivalent ", "spanType": "span-simple-text" }, { "children": [ { "text": "input", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " value.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "size": "narrow", "type": "image", "filename": "primary-energy-adjustment-solar.png", "parseErrors": [] }, { "type": "text", "value": [ { "text": "Since we\u2019re adjusting renewables ", "spanType": "span-simple-text" }, { "children": [ { "text": "upwards", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " \u2013 to assume that they\u2019re more inefficient than they are \u2013 primary energy measured by the \u2018substitution method\u2019 overstates the amount of energy that\u2019s produced.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "text": [ { "text": "The difference between \u2018substitution\u2019 and \u2018direct\u2019 primary energy", "spanType": "span-simple-text" } ], "type": "heading", "level": 2, "parseErrors": [] }, { "type": "text", "value": [ { "text": "How we measure primary energy matters for the comparisons of energy sources.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "One way to look at this is to see the production of renewables and nuclear changes based on the \u2018direct\u2019 and \u2018substitution\u2019 method. This is shown in the chart below. You can see that \u2018substituted energy\u2019 is always higher than \u2018direct energy\u2019.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "Again, to be clear: nuclear energy also has inefficiencies in thermal generation in a power plant. But national statistics tend to report it as electricity ", "spanType": "span-simple-text" }, { "children": [ { "text": "outputs", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": ", so we need to apply the same conversion factors as we do for renewables.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "url": "https://ourworldindata.org/grapher/renewable-nuclear-direct-substitution", "type": "chart", "parseErrors": [] }, { "type": "text", "value": [ { "text": "When we compare these energy sources to fossil fuels in ", "spanType": "span-simple-text" }, { "children": [ { "text": "direct", "spanType": "span-simple-text" } ], "spanType": "span-italic" }, { "text": " primary energy terms, we\u2019re comparing inefficient fossil fuel inputs to renewable energy sources without this inefficiency. That makes it look like solar and wind are making a small contribution to energy demand.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "When we adjust renewables via the substitution method, their share in the energy mix increases. We see this in the two charts below.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "url": "https://ourworldindata.org/grapher/share-of-primary-energy-consumption-by-source", "type": "chart", "parseErrors": [] }, { "url": "https://ourworldindata.org/grapher/share-energy-source-sub", "type": "chart", "parseErrors": [] }, { "type": "text", "value": [ { "text": "In general, the \u2018substitution method\u2019 gives us a better reflection of the contribution of different sources to the energy mix. That\u2019s why researchers often apply it.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "However, this still fails to account for many other inefficiencies that are removed when we decarbonize our energy systems. For example, electric vehicles are around ", "spanType": "span-simple-text" }, { "url": "https://www.sustainabilitybynumbers.com/p/inefficiency-ice", "children": [ { "text": "four times as efficient", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " as petrol or diesel cars. Similarly, electric heat pumps ", "spanType": "span-simple-text" }, { "url": "https://www.sustainabilitybynumbers.com/p/heat-pumps", "children": [ { "text": "significantly reduce", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": " gas demands.", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "text", "value": [ { "text": "These energy reductions are not captured in primary energy metrics. To understand them we need to look at final and useful energy demand. I cover this in a related article ", "spanType": "span-simple-text" }, { "url": "https://ourworldindata.org/energy-definitions", "children": [ { "text": "here", "spanType": "span-simple-text" } ], "spanType": "span-link" }, { "text": ".", "spanType": "span-simple-text" } ], "parseErrors": [] }, { "type": "horizontal-rule", "value": {}, "parseErrors": [] }, { "text": [ { "type": "text", "value": [ { "text": "This article was first published in November 2021, and updated in October 2023.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "type": "callout", "title": "Update", "parseErrors": [] } ], "refs": { "errors": [], "definitions": { "bf1246a5d3c330ce04b223bd3454719ebea512b3": { "id": "bf1246a5d3c330ce04b223bd3454719ebea512b3", "index": 0, "content": [ { "type": "text", "value": [ { "text": "This efficiency also depends on the age and type of coal or gas plant. Newer plants can achieve slightly higher efficiency.", "spanType": "span-simple-text" } ], "parseErrors": [] } ], "parseErrors": [] } } }, "type": "article", "title": "What\u2019s the difference between direct and substituted primary energy?", "authors": [ "Hannah Ritchie", "Pablo Rosado" ], "excerpt": "How do different metrics of energy quantification compare?", "dateline": "November 9, 2021", "subtitle": "", "featured-image": "" } |
1 | 2023-10-10 09:33:39 | 2021-11-09 08:51:14 | 2023-12-28 16:31:07 | unlisted | ALBJ4Ls2NzU2MkBou3a7cR6nAWc4IH_FVgV8J1nHZOp7vnVggsDyRUu2tuzz9_1VGEfAR83mGOk6Xah0icwSOQ | [ { "href": "/energy", "label": "Energy" }, { "label": "Direct vs. Substituted Primary Energy" } ] |
Understanding the breakdown of our energy systems – how much energy we get from coal, oil or gas, how much from nuclear, solar or wind – is crucial. It lets us compare energy mixes across the world and track progress on decarbonization. But summarizing global energy with just _one_ metric is not simple. Researchers used a range of measures that tell us different things. There are four different measures, which capture the transformations and losses that occur across the energy chain: primary, secondary, final, or useful energy. I write about these in [another article](https://ourworldindata.org/energy-definitions), and summarize them in the chart below. <Image filename="Four-ways-of-measuring-energy.png"/> But a further problem is that energy sources are often reported in commodity markets and some of the most commonly-used datasets using _different_ metrics. In this article I focus on various ways in which ‘primary energy’ is measured. I explain how different energy sources are quantified in these datasets, and what adjustments are made to make them more comparable. ## Fossil fuel energy is measured differently from renewable electricity Energy from fossil fuels – coal, oil and gas – are usually measured as _primary_ energy. That is, the amount of energy that’s generated when they are burned in their raw form. For coal, it’s the total amount of energy you get when you burn it. But, a large amount of this raw energy is wasted as heat. A [typical coal plant in the US](https://www.energy.gov/fecm/transformative-power-systems) has an efficiency of 33%.1 Only one-third generates electricity, and the other two-thirds is wasted as heat. You need to burn three units of coal to get one unit of electricity. Gas electricity is slightly better, with [an efficiency](https://www.eia.gov/todayinenergy/detail.php?id=44436) of around 45%. Put two units of gas energy in, and you get _almost_ one unit of electricity out. <Image filename="efficiency-coal-gas-plants.png"/> In popular datasets, such as the _[Statistical Review of World Energy](https://www.energyinst.org/statistical-review)_, published by the Energy Institute (it was formerly published by BP), coal and gas are reported in their primary energy terms – as the fuels going _into_ the power plant. But this is not how renewable electricity – such as solar and wind is recorded. It’s reported in terms of its electricity output. Think about what this means. We’re comparing the amount of energy generated by fossil fuels _with_ all of the wasted heat, to the amount generated by renewables _without_ this wastage. If you were to replace the electricity from coal and gas with renewables, the energy requirements would be much lower. ## The ‘substitution’ primary energy method To ‘correct’ for these different methods of accounting, researchers can apply the ‘substitution method’. This tries to adjust non-fossil energy sources to the inputs that would be needed if it was generated from fossil fuels. It assumes that wind and solar electricity is as inefficient as coal or gas. This adjustment is fairly crude. Non-fossil electricity generation is divided by a ‘thermal efficiency factor’, which is the average efficiency of fossil electricity. In the chart, we see the factor that the Energy Institute applies. This factor has changed over time due to changes in the composition of the fossil fuel mix (the split between coal and gas), and efficiency improvements in power plants over time. <Chart url="https://ourworldindata.org/grapher/thermal-efficiency-factor"/> Let’s say that a country produces 100 terawatt-hours (TWh) of electricity from solar, and the thermal efficiency factor is 0.4. To get the ‘primary energy equivalents’ we divide 100 TWh by 0.4. That’s 250 TWh. What this means is that if this electricity was produced by fossil fuels, we’d need 250 TWh of energy _in_ to get 100 TWh of electricity _out_. In the substitution method, non-fossil electricity sources are divided by this efficiency factor. The same is done for nuclear. In reality, nuclear does experience thermal losses in a power plant, just like fossil fuels. It has [a thermal efficiency](https://www.world-nuclear.org/uploadedFiles/org/WNA/Publications/WNA_Position_Statements/PS-cooling.pdf) ranging from around 33% to 40%. But since it’s reported in terms of electricity _output_, we need to do this adjustment to calculate its equivalent _input_ value. <Image filename="primary-energy-adjustment-solar.png"/> Since we’re adjusting renewables _upwards_ – to assume that they’re more inefficient than they are – primary energy measured by the ‘substitution method’ overstates the amount of energy that’s produced. ## The difference between ‘substitution’ and ‘direct’ primary energy How we measure primary energy matters for the comparisons of energy sources. One way to look at this is to see the production of renewables and nuclear changes based on the ‘direct’ and ‘substitution’ method. This is shown in the chart below. You can see that ‘substituted energy’ is always higher than ‘direct energy’. Again, to be clear: nuclear energy also has inefficiencies in thermal generation in a power plant. But national statistics tend to report it as electricity _outputs_, so we need to apply the same conversion factors as we do for renewables. <Chart url="https://ourworldindata.org/grapher/renewable-nuclear-direct-substitution"/> When we compare these energy sources to fossil fuels in _direct_ primary energy terms, we’re comparing inefficient fossil fuel inputs to renewable energy sources without this inefficiency. That makes it look like solar and wind are making a small contribution to energy demand. When we adjust renewables via the substitution method, their share in the energy mix increases. We see this in the two charts below. <Chart url="https://ourworldindata.org/grapher/share-of-primary-energy-consumption-by-source"/> <Chart url="https://ourworldindata.org/grapher/share-energy-source-sub"/> In general, the ‘substitution method’ gives us a better reflection of the contribution of different sources to the energy mix. That’s why researchers often apply it. However, this still fails to account for many other inefficiencies that are removed when we decarbonize our energy systems. For example, electric vehicles are around [four times as efficient](https://www.sustainabilitybynumbers.com/p/inefficiency-ice) as petrol or diesel cars. Similarly, electric heat pumps [significantly reduce](https://www.sustainabilitybynumbers.com/p/heat-pumps) gas demands. These energy reductions are not captured in primary energy metrics. To understand them we need to look at final and useful energy demand. I cover this in a related article [here](https://ourworldindata.org/energy-definitions). --- <Callout title="Update"/> This efficiency also depends on the age and type of coal or gas plant. Newer plants can achieve slightly higher efficiency. | What’s the difference between direct and substituted primary energy? |