Ucs, the controversial organization, has an interesting analysis of geothermal.<p><a href="https://www.ucsusa.org/resources/environmental-impacts-geothermal-energy" rel="nofollow">https://www.ucsusa.org/resources/environmental-impacts-geoth...</a><p>The takeaway<p>> Enhanced geothermal systems, which require energy to drill and pump water into hot rock reservoirs, have life-cycle global warming emission of approximately 0.2 pounds of carbon dioxide equivalent per kilowatt-hour [11].<p>> To put this into context, estimates of life-cycle global warming emissions for natural gas generated electricity are between 0.6 and 2 pounds of carbon dioxide equivalent per kilowatt-hour and estimates for coal-generated electricity are 1.4 and 3.6 pounds of carbon dioxide equivalent per kilowatt-hour.<p>Nothing is really truly zero carbon currently. Solar has manufacturing and maintenance. Nuclear has construction, mining, refinement, containment, etc. It's nice to see the full lifecycle being looked at.<p>We can't pretend that something essential for the process doesn't matter because we do a classification handwaving. It all counts
The first geothermal wells in Germany have exhausted their heat gradient; after less than 30 years … so, unless you’re actually in Iceland or the Canaries or something similar, this might not even sustainable for even one full generation …
I just priced out HVAC for a large home in central KY. It worked out to 3 of the highest efficiency American Standard/Trane units (Central Heating and Air) for around 50k or a touch over 70k for Bosch Geothermal. The big caveat for geothermal was the 70k price was guaranteed <i>only</i> if they didn't hit rock when digging. They couldn't give me a guaranteed price if they did hit rock so the choice was obvious. I picked Central Heating and Air.<p>For horizontal or vertical geothermal loops, the biggest cost is always going to be digging for the loops. Until they make that more affordable, they're going to have a hard time making it more ubiquitous.
This seems to be all about Geothermal HEATING, which seems pretty tough in most places. I thought Geothermal Cooling is easier/cheaper in many areas? Heat from Geothermal seems really difficult because you have to drill so deep almost everywhere, but that's not the case for cooling, is it?<p>Iceland seems to have some decent heat there: <a href="https://en.wikipedia.org/wiki/Geothermal_power_in_Iceland" rel="nofollow">https://en.wikipedia.org/wiki/Geothermal_power_in_Iceland</a><p>Five major geothermal power plants exist in Iceland, which produce approximately 26.2% (2010) of the nation's electricity.
For nordic climates: After running the numbers I was surprised by how little benefit I'd get from geothermal drilling + heat pump for a <i>much</i> larger investment (like $30k including internal fitting of water-based radiators) compared to a regular outdoor air/air heat pump for $2k. Ongoing costs would be like 5-8% lower.<p>Modern air/air heat pumps are awesome.
<i>Most current efforts need a lot to go right just to reach mediocrity.</i><p>Right. It may be do-able, but unlikely to be cost effective in deep hard rock.<p>One of the deepest drilling projects got down 31,400 feet, but instead of hitting something saleable like natural gas or oil, they got liquid sulfur.
Hug of death?<p><a href="https://web.archive.org/web/20210707172539/https://austinvernon.eth.link/blog/geothermal.html" rel="nofollow">https://web.archive.org/web/20210707172539/https://austinver...</a>
IMO, geothermal doesn't really make sense. It's expensive, and the heat gradient isn't huge- you have to drill or dig huge trenches to make up for it.<p>Solar water heating is extremely efficient (and less complicated), but I have never seen it in the US.<p>As for cooling, if it's hot out, the sun is probably out- solar PV with AC/heat pump should be fine.
I've wondered if there could be a way to use the Earth's heat by drilling a small hole in your back yard a few km deep and somehow embedding a tiny generator down there to take advantage of the heat differential between various layers of rock. Maybe a Stirling engine? I'm thinking like a long thin tube filled with liquid that boils at low temps. The liquid would boil, expand, rise up through an insulated tube, condense at a cooler layer and circulate back down. A little generator could use the constant motion to power a house.