https://www.explainxkcd.com/wiki/api.php?action=feedcontributions&feedformat=atom&user=Bendkokexplain xkcd - User contributions [en]2026-04-13T17:34:30ZUser contributionsMediaWiki 1.30.0https://www.explainxkcd.com/wiki/index.php?title=2710:_Hydropower_Breakthrough&diff=3014082710: Hydropower Breakthrough2022-12-15T16:44:52Z<p>Bendkok: Added {{citation needed}}.</p>
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<div>{{comic<br />
| number = 2710<br />
| date = December 12, 2022<br />
| title = Hydropower Breakthrough<br />
| image = hydropower_breakthrough_2x.png<br />
| imagesize = 261x303px<br />
| noexpand = true<br />
| titletext = A hydroelectric dam is also known as a heavy water reactor.<br />
}}<br />
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==Explanation==<br />
{{incomplete|Created by a PRACTICAL WATER REACTOR. Do NOT delete this tag too soon.}}<br />
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In this comic, [[Beret Guy]] announces that their {{w|hydroelectric dam}} has reached "Q > 1" supposedly meaning that it is producing more water than is flowing into it. In reality, this would violate the physical law of conservation of mass. Over the lifetime of a dam, the volume of water that passes through the outflow gates will be less than the total volume of water precipitated in the catchment area due to evaporation, seepage, and other losses. To produce more water, matter would have to be created. If only a short time period is considered, a dam can naturally release more water than is fed into it, especially during dry seasons or after a dam break. The title "breakthrough" could refer to this, but it would not be a cause for celebration. While one audience member celebrates, another expresses concern. <br />
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The comic parodies {{w|fusion reactor}}s, a type of electrical generator that can use deuterium and tritium as inputs to produce helium and a large amount of power. However, maintaining a fusion reaction has historically been difficult, and fusion reactors often require more external power than they generate. In recent years, advances in fusion technology have increased the energy output of fusion reactors to more than the input. It is possible that this comic is a reference to the [https://www.washingtonpost.com/business/2022/12/11/fusion-nuclear-energy-breakthrough/ announcement of the first Q > 1 fusion reaction at the US National Ignition Facility], which was scheduled for the day after the comic was released. The symbol Q is used to refer to the {{w|fusion energy gain factor}}, the ratio of power generated by a fusion reactor to the energy used to maintain it. An energy source is only useful if it produces more power than it uses{{citation needed}}, so Q > 1 means the reactor is generating net energy. Q can also represent the flow rate of water through a hydroelectric dam, and in this case, a Q > 1 would not have significant meaning.<br />
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The title text further confuses the issue by introducing nuclear fission and equating the hydroelectric dam with a {{w|heavy water reactor}}, which is a type of nuclear fission reactor that uses deuterium oxide as a moderator. This is also a play on words, as the weight of water can be used to power a hydroelectric dam.<br />
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==Transcript==<br />
:[Beret Guy is standing on a podium behind a lectern. He is gesturing with his hand, palm up, towards a poster hanging behind him. On it is a picture of a tall dam, with a lake behind, and water coming out at the foot of the dam in the valley on the other side. Two voices reacts to Beret Guy's statement from off-panel.]<br />
:Beret Guy: We are pleased to announce that our hydroelectric dam has achieved Q>1, producing more water than we fed into it!<br />
:Off-panel voice 1: Hooray!<br />
:Off-panel voice 2: Wait.<br />
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{{comic discussion}}<br />
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[[Category:Comics featuring Beret Guy]]<br />
[[Category:Strange powers of Beret Guy]]<br />
[[Category:Public speaking]]<br />
[[Category:Physics]]</div>Bendkok