<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>dpark</author><text>&amp;gt; &lt;i&gt;The first sentence of that section says that &amp;quot;geothermal power is considered to be renewable because any projected heat extraction is small compared to the Earth&amp;#x27;s heat content.&amp;quot; I&amp;#x27;d like to see some estimates on how much of that heat content is available on the depths we&amp;#x27;re drilling down to (as opposed to the contents of the whole planet);&lt;/i&gt;&lt;p&gt;Wikipedia links to an article with more detail.  The crust alone is estimated to hold enough heat to supply all of the Earth&amp;#x27;s electricity generation at current levels for about 80 million years.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;web.archive.org&amp;#x2F;web&amp;#x2F;20100308014920&amp;#x2F;http:&amp;#x2F;&amp;#x2F;www.iea-gia.org&amp;#x2F;documents&amp;#x2F;FridleifssonetalIPCCGeothermalpaper2008FinalRybach20May08_000.pdf&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;web.archive.org&amp;#x2F;web&amp;#x2F;20100308014920&amp;#x2F;http:&amp;#x2F;&amp;#x2F;www.iea-gi...&lt;/a&gt;&lt;p&gt;&lt;i&gt;The total heat content of the Earth is of the order of 12.6 x 10^24 MJ, and that of the crust the order of 5.4 x 10^21 MJ (Dickson and Fanelli, 2004). This huge number should be compared to the world electricity generation in 2005, 6.6 x 10^13 MJ.&lt;/i&gt;&lt;p&gt;&amp;gt; &lt;i&gt;and again, trees were a renewable resource too, before the industrial revolution.&lt;/i&gt;&lt;p&gt;Trees are still a renewable resource, more so since we largely stopped using them for fuel as a result of the industrial revolution.</text><parent_chain><item><author>TeMPOraL</author><text>Almost everything we do that initially seems like a good idea stops being such when we start doing it at scale. Burning fuels wasn&amp;#x27;t a problem at the eve of the industrial revolution. I wonder what ecological issues will hit us globally as we scale up geothermal energy use. E.g. I&amp;#x27;ve read somewhere that people putting too many ground-exchange heat pumps in a small area can cause problematic cooling of the ground. Right now it&amp;#x27;s probably only a problem for the energy efficiency of the pumps themselves, but as we scale up, I worry about unintended environmental consequences.&lt;p&gt;Wikipedia seems to have only basic numbers up:&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Geothermal_energy#Renewability_and_sustainability&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Geothermal_energy#Renewability...&lt;/a&gt;&lt;p&gt;The first sentence of that section says that &amp;quot;geothermal power is considered to be renewable because any projected heat extraction is small compared to the Earth&amp;#x27;s heat content.&amp;quot; I&amp;#x27;d like to see some estimates on how much of that heat content is available on the depths we&amp;#x27;re drilling down to (as opposed to the contents of the whole planet); and again, trees were a renewable resource too, before the industrial revolution.</text></item></parent_chain></comment><story><title>Cornell wants to drill 2-4mi underground for enhanced geothermal heating</title><url>http://arstechnica.com/science/2016/09/cornell-has-a-plan-to-prove-that-the-east-coast-can-have-geothermal-heat/</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>SamBam</author><text>The point of renewables is rarely to do them all &amp;quot;at scale&amp;quot; where we&amp;#x27;re expecting that one renewable to power the entire planet.&lt;p&gt;Yes, if we try to use solar for the entire planet, we&amp;#x27;ll destroy the world trying to mine every last bit of silica. If we try and use wind for the entire planet, we&amp;#x27;d need to build something like 6-8 million turbines, possibly causing environmental destruction on the way.&lt;p&gt;Rather, the point is to say &amp;quot;here&amp;#x27;s a huge vein of untapped energy, some of which could be tapped without damaging the environment and without releasing carbon.&amp;quot;&lt;p&gt;Green energy is a mix, and extrapolating to &amp;quot;what if everybody did this&amp;quot; is rarely the right question, especially when the current alternative is &amp;quot;keep burning oil.&amp;quot;</text><parent_chain><item><author>TeMPOraL</author><text>Almost everything we do that initially seems like a good idea stops being such when we start doing it at scale. Burning fuels wasn&amp;#x27;t a problem at the eve of the industrial revolution. I wonder what ecological issues will hit us globally as we scale up geothermal energy use. E.g. I&amp;#x27;ve read somewhere that people putting too many ground-exchange heat pumps in a small area can cause problematic cooling of the ground. Right now it&amp;#x27;s probably only a problem for the energy efficiency of the pumps themselves, but as we scale up, I worry about unintended environmental consequences.&lt;p&gt;Wikipedia seems to have only basic numbers up:&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Geothermal_energy#Renewability_and_sustainability&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Geothermal_energy#Renewability...&lt;/a&gt;&lt;p&gt;The first sentence of that section says that &amp;quot;geothermal power is considered to be renewable because any projected heat extraction is small compared to the Earth&amp;#x27;s heat content.&amp;quot; I&amp;#x27;d like to see some estimates on how much of that heat content is available on the depths we&amp;#x27;re drilling down to (as opposed to the contents of the whole planet); and again, trees were a renewable resource too, before the industrial revolution.</text></item></parent_chain></comment><story><title>Cornell wants to drill 2-4mi underground for enhanced geothermal heating</title><url>http://arstechnica.com/science/2016/09/cornell-has-a-plan-to-prove-that-the-east-coast-can-have-geothermal-heat/</url></story>