Geothermal's path to relevance: cheap drilling
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Geothermal's path to relevance: cheap drilling
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Re: Geothermal's path to relevance: cheap drilling
#2I am always a bit bearish on geothermal, because the energy flow through the earths crust is just so damn low. Per surface area, it is about 3 orders of magnitude less than solar irradiation, which means that the circumstances in which it really makes sense to exploit geothermal are those where you can effectively harvest flows from a much larger area, most likely due to convection of water or magma. My understanding is that it will never make sense for e.g. every house in a suburban setting to have their own heat probe and pull energy from that, they will be competing with their neighbors and effective energy gained will be negligible.
Re: Geothermal's path to relevance: cheap drilling
#3From the article: Traditional geothermal wells target rare hydrothermal resources
Florida geothermal systems pull cool water from the aquifer, use it for A/C and return it via a 2nd well. They're about the only wells that water management districts will rubberstamp.
Geothermal cooling (in FL) becomes cost efficient above 15k-20k sq ft (based on my 2010s exp). That led me to an idea that neighborhoods could be cooled by small geothermal utilities. I wonder about increased heat energy down the line but I've seen a doz+ chillers work efficiently, from one 4" well. On a larger scale, downstream heat buildup might be mitigated via a more distributed water system.
Re: Geothermal's path to relevance: cheap drilling
#4I am always a bit bearish on geothermal, because the energy flow through the earths crust is just so damn low. Per surface area, it is about 3 orders of magnitude less than solar irradiation, which means that the circumstances in which it really makes sense to exploit geothermal are those where you can effectively harvest flows from a much larger area, most likely due to convection of water or magma. My understanding…
is surface area a fair comparison? A deep well should be able to extract all along its length
Re: Geothermal's path to relevance: cheap drilling
#5Cheap drilling would be a large boon for geothermal, considering the cost of surveying/exploring/drilling is > 50% of the cost of the development of a geothermal site.
I don't understand the articles goal of 300C target, though. While some types of geothermal plants do require temperatures that high, binary cycle power plants can use lower temperatures (130C) [1], which seems to open up more area for geothermal development since we expect most gradients between the surface and bottom of the crust to be ~2.5-3.1C / 100M. A lower temperature requirement would in turn allow you to drill less deep, which could consequently also decrease drilling costs.
Another thing the article doesn't mention: another interesting approach (aside from improving the technology, like drill bits) is with financing innovation. There have been / are government programs to de-risk the exploration/drilling cost by reimbursing the costs of drilling (80% for failed wells, for example) which also likely adds well data that could better characterize the underlying geothermal resources in regions (which would allow more accurate future development).
Really glad to see a deeper dive on geothermal though; its non-intermittency is a valuable characteristic separating it from other renewables that we're currently favoring (solar/wind). Because we generally break down energy generation to LCOE, it omits advantages like uptime of the renewable resource.
[1] https://www.energy.gov/eere/geothermal/electricity-generatio...
Re: Geothermal's path to relevance: cheap drilling
#6From the article: Traditional geothermal wells target rare hydrothermal resources Florida geothermal systems pull cool water from the aquifer, use it for A/C and return it via a 2nd well. They're about the only wells that water management districts will rubberstamp. Geothermal cooling (in FL) becomes cost efficient above 15k-20k sq ft (based on my 2010s exp). That led me to an idea that neighborhoods could be cooled…
I'm reminded of this video talking about cooling the London Underground. Since it's running through clay, it's very well insulated and the ground around it is warming year over year.
Re: Geothermal's path to relevance: cheap drilling
#7I am always a bit bearish on geothermal, because the energy flow through the earths crust is just so damn low. Per surface area, it is about 3 orders of magnitude less than solar irradiation, which means that the circumstances in which it really makes sense to exploit geothermal are those where you can effectively harvest flows from a much larger area, most likely due to convection of water or magma. My understanding…
It’s often less about the heat flow than simply the amount of heat contained in that volume of rock.
For your example: A 1/2 acre home is 2023 m2, 1kg of rock is ~2000j/degrees Celsius, 1 cubic meter of rock is ~2500 kg, down 1k = ~2000 j * 2500 * 2023 * 1000 / 60 / 60 / 1000 ~= 2,800,000 kWh per degC. If you’re talking 1kw of heat on average from that rock you only drop 1 degree after 300 years.
Of course 1km is a fairly deep, but if you’re using a heat pump chances are you’re averaging much less than 1kw over the entire year.
Re: Geothermal's path to relevance: cheap drilling
#8Cheap drilling would be a large boon for geothermal, considering the cost of surveying/exploring/drilling is > 50% of the cost of the development of a geothermal site. I don't understand the articles goal of 300C target, though. While some types of geothermal plants do require temperatures that high, binary cycle power plants can use lower temperatures (130C) [1], which seems to open up more area for geothermal devel…
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Re: Geothermal's path to relevance: cheap drilling
#9From the article: Traditional geothermal wells target rare hydrothermal resources Florida geothermal systems pull cool water from the aquifer, use it for A/C and return it via a 2nd well. They're about the only wells that water management districts will rubberstamp. Geothermal cooling (in FL) becomes cost efficient above 15k-20k sq ft (based on my 2010s exp). That led me to an idea that neighborhoods could be cooled…
What I always find dumb is when I see a swimming pool and an air conditioner without the two being one system.
Do Floridians at least install heat-pump pool heater systems indoors so the cold goes indoors?
Re: Geothermal's path to relevance: cheap drilling
#10I am always a bit bearish on geothermal, because the energy flow through the earths crust is just so damn low. Per surface area, it is about 3 orders of magnitude less than solar irradiation, which means that the circumstances in which it really makes sense to exploit geothermal are those where you can effectively harvest flows from a much larger area, most likely due to convection of water or magma. My understanding…
Sounds like the systems would work best where you have both heating and cooling loads throughout the year.
Though usually you’re pumping more heat out of the ground than in. There must be a perfect place for these systems where it’s well balanced.