<story><title>Tidal energy is not renewable</title><url>https://cs.stanford.edu/people/zjl/tide.html</url></story><parent_chain><item><author>Nition</author><text>Humanity needing that amount of energy seems obviously absurd, but then I suppose a CPU with 100 billion transistors seemed clearly impossible in 1960.&lt;p&gt;Maybe a few hundred years from now, Internet archaeologists will find your comment as one of the first harbingers of the coming World Energy Crisis, much as we see the 1912 Rodney &amp;amp; Otamatea Times &amp;quot;Coal Consumption Affecting Climate&amp;quot; snippet today.[0]&lt;p&gt;Then they&amp;#x27;ll find this comment...&lt;p&gt;----&lt;p&gt;[0] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;paperspast.natlib.govt.nz&amp;#x2F;newspapers&amp;#x2F;rodney-and-otamatea-times-waitemata-and-kaipara-gazette&amp;#x2F;1912&amp;#x2F;08&amp;#x2F;14&amp;#x2F;7&quot; rel=&quot;nofollow noreferrer&quot;&gt;https:&amp;#x2F;&amp;#x2F;paperspast.natlib.govt.nz&amp;#x2F;newspapers&amp;#x2F;rodney-and-otam...&lt;/a&gt;</text></item><item><author>wcoenen</author><text>I&amp;#x27;m not sure the author realized this, but they&amp;#x27;re actually making a statement about how crazy exponential growth is. Not about the sustainability of tidal power. This becomes obvious once you look closer at what that 2% growth rate (as assumed in the post) implies.&lt;p&gt;Our global energy consumption in 2008 was estimated to be 474 exajoules. The total energy received by the earth from the sun during a year is about 5 million exajoules, a fraction of which reaches the surface. 5 million is much more than 474. But at a seemingly modest 2% per year growth rate (as it was between 1980 and 2006), our energy consumption will match those 5 million exajoules in less than 500 years!&lt;p&gt;Think about that: if energy consumption growth continues at the current pace, then in 500 years we&amp;#x27;ll either be using ALL solar energy received by the earth (leaving none for the biosphere), or we&amp;#x27;ll have figured out some magic technology to produce 5 million exajoules of energy per year. Assuming the magic technology, where are we going to get rid of all that extra heat? It would effectively be like having a second sun on earth, cooking us in place.&lt;p&gt;edit: I copied the numbers above from a post I wrote in 2010, so it may be a bit out of date. But Sabine Hossenfelder recently made a video where she talked about a similar timescale, i.e. boiling oceans in 400 years: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=9vRtA7STvH4&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=9vRtA7STvH4&lt;/a&gt;</text></item></parent_chain><comment><author>crote</author><text>I&amp;#x27;d say that the CPU example actually &lt;i&gt;proves&lt;/i&gt; the point.&lt;p&gt;A computer today costs &lt;i&gt;roughly&lt;/i&gt; the same as a computer in the 1980s, and it also consumes &lt;i&gt;roughly&lt;/i&gt; the same amount of energy as a computer from that era. We got faster computers because we got better at making transistors.&lt;p&gt;If we look at laptops, a device which consumes 200W already gets hot enough that it is uncomfortable to actually place on your lap. A 1kW desktop computer is pretty much impossible to cool.&lt;p&gt;At our current population, those 5 million exajoules a year is a constant power consumption of roughly 16 megawatt per person. For comparison, that&amp;#x27;s about the same magnitude of energy you&amp;#x27;d need for every human to launch a Falcon 9 to eat lunch in the ISS. Once figures get this big, you simply run out of things to do.</text></comment>
<story><title>Tidal energy is not renewable</title><url>https://cs.stanford.edu/people/zjl/tide.html</url></story><parent_chain><item><author>Nition</author><text>Humanity needing that amount of energy seems obviously absurd, but then I suppose a CPU with 100 billion transistors seemed clearly impossible in 1960.&lt;p&gt;Maybe a few hundred years from now, Internet archaeologists will find your comment as one of the first harbingers of the coming World Energy Crisis, much as we see the 1912 Rodney &amp;amp; Otamatea Times &amp;quot;Coal Consumption Affecting Climate&amp;quot; snippet today.[0]&lt;p&gt;Then they&amp;#x27;ll find this comment...&lt;p&gt;----&lt;p&gt;[0] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;paperspast.natlib.govt.nz&amp;#x2F;newspapers&amp;#x2F;rodney-and-otamatea-times-waitemata-and-kaipara-gazette&amp;#x2F;1912&amp;#x2F;08&amp;#x2F;14&amp;#x2F;7&quot; rel=&quot;nofollow noreferrer&quot;&gt;https:&amp;#x2F;&amp;#x2F;paperspast.natlib.govt.nz&amp;#x2F;newspapers&amp;#x2F;rodney-and-otam...&lt;/a&gt;</text></item><item><author>wcoenen</author><text>I&amp;#x27;m not sure the author realized this, but they&amp;#x27;re actually making a statement about how crazy exponential growth is. Not about the sustainability of tidal power. This becomes obvious once you look closer at what that 2% growth rate (as assumed in the post) implies.&lt;p&gt;Our global energy consumption in 2008 was estimated to be 474 exajoules. The total energy received by the earth from the sun during a year is about 5 million exajoules, a fraction of which reaches the surface. 5 million is much more than 474. But at a seemingly modest 2% per year growth rate (as it was between 1980 and 2006), our energy consumption will match those 5 million exajoules in less than 500 years!&lt;p&gt;Think about that: if energy consumption growth continues at the current pace, then in 500 years we&amp;#x27;ll either be using ALL solar energy received by the earth (leaving none for the biosphere), or we&amp;#x27;ll have figured out some magic technology to produce 5 million exajoules of energy per year. Assuming the magic technology, where are we going to get rid of all that extra heat? It would effectively be like having a second sun on earth, cooking us in place.&lt;p&gt;edit: I copied the numbers above from a post I wrote in 2010, so it may be a bit out of date. But Sabine Hossenfelder recently made a video where she talked about a similar timescale, i.e. boiling oceans in 400 years: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=9vRtA7STvH4&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=9vRtA7STvH4&lt;/a&gt;</text></item></parent_chain><comment><author>mNovak</author><text>A direct link to the mentioned snippet:&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;paperspast.natlib.govt.nz&amp;#x2F;newspapers&amp;#x2F;ROTWKG19120814.2.56.5&quot; rel=&quot;nofollow noreferrer&quot;&gt;https:&amp;#x2F;&amp;#x2F;paperspast.natlib.govt.nz&amp;#x2F;newspapers&amp;#x2F;ROTWKG19120814....&lt;/a&gt;</text></comment>