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Geothermal's path to relevance: cheap drilling

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Re: Geothermal's path to relevance: cheap drilling

#21

Post by cdeonier »

streamofdigits wrote: post #4
phreeza wrote: post #2

I 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

How does a deep well extract all along its length? My belief was the production well will experience a gradient (so the bottom of the well will have the temperature you need), and the temperature will drop as you get closer to the surface (which also contributes to the calcite scaling problem geothermal can experience).

Also, I think a lot of wells add concrete casing (or metal, as indicated in the article) around portions of the well, which would prevent extraction around those zones of the well.

Re: Geothermal's path to relevance: cheap drilling

#22

Post by streamofdigits »

cdeonier wrote: post #21
streamofdigits wrote: post #4

Earlier quoted context omitted.

is surface area a fair comparison? A deep well should be able to extract all along its length

How does a deep well extract all along its length? My belief was the production well will experience a gradient (so the bottom of the well will have the temperature you need), and the temperature will drop as you get closer to the surface (which also contributes to the calcite scaling problem geothermal can experience). Also, I think a lot of wells add concrete casing (or metal, as indicated in the article) around po…

assuming you can reach a working temperature differential why not continue deeper with the well? From that threshold depth onwards you can extract heat along a line segment that extends to the ultimate depth (which is pressumably dictated by engineering limitations)

caveat: thinking like a physicist, not an engineer :-)

Re: Geothermal's path to relevance: cheap drilling

#23

Post by brtkdotse »

Factorium wrote: post #11

Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all new suburban constructions, alongside passivhaus standards, we could eliminate residential fossil fuel connections for huge sections of the Western world. Like another commenter mentioned, we could even have communal systems for individual streets, drilled beneat…

Geothermal heat pumps are very common in the Nordics. It’s a one day operation, they come in, drill a 150M hole and run a brine loop hooked up to a heat pump. Sorts the heating and hot water for a 180 m2 house above the attic circle with less than 7000 kWh per year.

Re: Geothermal's path to relevance: cheap drilling

#24

Post by brtkdotse »

goldenshale wrote: post #18
phreeza wrote: post #2

I 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…

Yeah, per-house is probably never going to make sense, but larger scale operations where they can use hydraulic fracturing techniques to expand the surface area could be the solution. They call these Enhanced Geothermal Systems, and basically they frack the rock between two well bores to try to maximize connectivity and surface area.

I’d say more than half of single family houses in Sweden are heated by geothermal heat pumps, so it’s _very_ viable.

Re: Geothermal's path to relevance: cheap drilling

#25

Post by cmrdporcupine »

Scoundreller wrote: post #9
WarOnPrivacy wrote: post #3

From 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?

I looked into this here, and couldn't find a company to do a heat exchanger hookup for my pool, but also... at least here in the great lakes area, when you want to heat your pool the most is the time when your AC isn't really running (spring / fall), and you don't care about heating your pool as much when the AC is blasting. So while the pool may offer some efficiency gains to the AC, the waste heat from the AC doesn't help much with the pool.

Re: Geothermal's path to relevance: cheap drilling

#26

Post by serpix »

brtkdotse wrote: post #23
Factorium wrote: post #11

Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all new suburban constructions, alongside passivhaus standards, we could eliminate residential fossil fuel connections for huge sections of the Western world. Like another commenter mentioned, we could even have communal systems for individual streets, drilled beneat…

Geothermal heat pumps are very common in the Nordics. It’s a one day operation, they come in, drill a 150M hole and run a brine loop hooked up to a heat pump. Sorts the heating and hot water for a 180 m2 house above the attic circle with less than 7000 kWh per year.

that is a ground-source heat pump as the heat energy is mostly from ambient solar. But yes very common and I used to have one in my home before I moved away. It cost practically nothing to keep the house at t-shirt temperature during -25c cold weather snaps.

Re: Geothermal's path to relevance: cheap drilling

#27

Post by serpix »

turtlebits wrote: post #19
Factorium wrote: post #11

Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all new suburban constructions, alongside passivhaus standards, we could eliminate residential fossil fuel connections for huge sections of the Western world. Like another commenter mentioned, we could even have communal systems for individual streets, drilled beneat…

Yes, ground source/loop is considered geothermal. The problem is that you need to a dig up a large area of possible natural vegetation to do it.

I had my borehole going straight down about ~150m deep from right next to the side of my house. I moved the lawn right next to the pipes.

Re: Geothermal's path to relevance: cheap drilling

#28

Post by generalizations »

Factorium wrote: post #11

Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all new suburban constructions, alongside passivhaus standards, we could eliminate residential fossil fuel connections for huge sections of the Western world. Like another commenter mentioned, we could even have communal systems for individual streets, drilled beneat…

I'd be more interested in residential heat pumps if there were also heat engines that were feasible at that scale. Seems like it needs to scale up by at least an order of magnitude though, before electricity can be generated efficiently.

Re: Geothermal's path to relevance: cheap drilling

#29

Post by [deleted] »

serpix wrote: post #27
turtlebits wrote: post #19

Earlier quoted context omitted.

Yes, ground source/loop is considered geothermal. The problem is that you need to a dig up a large area of possible natural vegetation to do it.

I had my borehole going straight down about ~150m deep from right next to the side of my house. I moved the lawn right next to the pipes.

[deleted]

Re: Geothermal's path to relevance: cheap drilling

#30

Post by briffle »

cdeonier wrote: post #5

Cheap 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…

My old University powers, heats, and cools itself with Geothermal wells that are at 195F, not sure about the 300C either. (and clears snow/ice from sidewalks and outdoor staaircases) The college also sells extra power to the hospital next door. (it makes around 2MW with a binary cycle plant) https://urbanecologycmu.wordpress.com/2016/11/01/geothermal-...
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