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Geothermal's path to relevance: cheap drilling

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Re: Geothermal's path to relevance: cheap drilling

#61

Post by kragen »

fulafel wrote: post #55
kragen wrote: post #49

Earlier quoted context omitted.

No, this is totally irrelevant to anything in the article, except in the sense that both pertain to thermal energy and the earth. They have nothing else in common. The difference is not just a matter of sexiness; you can't run a factory, a computer, or a car off a ground-source heat pump, because heat pumps consume energy; they don't produce it.

Maybe a factory, many of them use heat in the range that heat pumps are suited for.

Only if they have access to another source of energy to power the heat pump and the other machinery that doesn't run on low-grade heat.

Re: Geothermal's path to relevance: cheap drilling

#63

Post by Animats »

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…

This is a good article.

The big breakthrough seems to be making drill bits out of a composite material formed from diamond and tungsten carbide.[1] One of their bits lasted through 25km of drilling. (Not one hole, re-used for multiple shallow holes.) That's encouraging. The geothermal people only need to go down 10km. Being able to do much of the job without backing out the drill string, one pipe section at a time, to change the bit is what seems to yield the cost estimates in the original article.

The next problem is to get everything at the down-hole end up to that level of reliability. Which is why the author talks about seal problems in mud-powered drilling motors. For the geothermal application, they just want to drill straight down, so they don't need all the fancy stuff used for slant and horizontal drilling.

So there remain some grungy, hard, and important problems to solve, like a seal material that will work better at high temperatures. Such things exist.[2]

This is encouraging.

The article points out that this isn't like hunting for oil and gas pockets; if you have roughly the correct overall geology, there will be hot rock down there anywhere you drill. This upsets some financial models, where drilling the first well in a new area is more like a VC-funded high-risk high return project. You're really drilling for the valuable info that oil or gas is there, not for the oil or gas from the exploration well. Deep geothermal is going to be dull, boring (literally), usually successful, and profitable over a long period but not in the short term. Great for regulated utilities.

[1] https://palmerbit.com/

[2] https://allsealsinc.com/HighTemperatureGaskets.html

Re: Geothermal's path to relevance: cheap drilling

#64

Post by guerby »

uuddlrlr wrote: post #14
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…

There's a 52-home community in Alberta that provides ~all of their winter heating by storing heat in the ground throughout the summer: https://www.dlsc.ca/borehole.htm It gets up to nearly 80C, but took a few years of operation to get there. The website covers it really well and I'd recommend checking it out.

I looked up the following paper:

https://www.researchgate.net/publication/326121453_Drake_Lan...

They get around 2000 GJ/year out of the storage, so 555 MWh, so 10.7 MWh/home.

Estimated current price of the system 4 millions USD (excluding one off 3 millions USD R&D costs) so 77000 USD/home.

7.2 USD/kWh of yearly thermal storage.

LFP battery is probably currently below 100 USD/kWh, so for this use the thermal battery is 10x cheaper.

Re: Geothermal's path to relevance: cheap drilling

#65

Post by dredmorbius »

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, in much the same way that passive or thermal (e.g., hot-water) solar designs are a form of solar power.

The principle difference, as others have pointed out, is that when converting heat to mechanical energy, or for electrical generation (mechanical + a generator), efficiency greatly increases as the temperature gradient between the hot and cold ends of the process increases.

There's still a lot of utility from lower-grade heat, for space heating (to about 24C/75F), water (about 60C/140F), and cooking (175C/350F). Even a partial boost can assist with other heating methods.

But for large-scale electrical generation, high temperatures, well above boiling point, are what are needed.

Community thermal energy storage is a thing. That can use either geological formations or specially-constructed insulated structures. Thermal potential may be stored as a hot or cold medium, for heating or cooling.

Re: Geothermal's path to relevance: cheap drilling

#66

Post by fulafel »

kragen wrote: post #61
fulafel wrote: post #55

Earlier quoted context omitted.

Maybe a factory, many of them use heat in the range that heat pumps are suited for.

Only if they have access to another source of energy to power the heat pump and the other machinery that doesn't run on low-grade heat.

Sure, factories run on many inputs, you cany do much with just electricity either :)

Re: Geothermal's path to relevance: cheap drilling

#67

Post by phreeza »

brtkdotse wrote: post #24
goldenshale wrote: post #18

Earlier quoted context omitted.

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.

But not as a source of electricity right?

Re: Geothermal's path to relevance: cheap drilling

#68

Post by jillesvangurp »

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…

The 300 degrees is needed to get enough steam pressure to drive a turbine. You need the temperature gradient basically to get that. It's all about efficiencies. A lower efficiency basically means you need to pump more water through, which means more drilling, which raises the cost.

Heat exchange pumps work with much lower temperature gradients which is great for heating a building or some water since you don't need to drill that deep. But it's not very efficient for generating electricity. There actually are some companies that can use heated water in your boiler as a battery and generate electricity from it but that is more from the point of view of using the energy you are storing anyway instead of letting it cool down. So a lower efficiency is acceptable for that.

The open question mark for geothermal is if the cost of drilling will ever be low enough to compete with solar and wind + batteries. Solar and wind are a lot cheaper per kwh but of course intermittent. There are various ways of fixing that that basically involve using some form of battery. You can think of geothermal as a battery where the fully charged battery simply is our planet. Nice if you can get to it but not necessarily cheap enough compared to other ways to store energy. Getting to it involves expensive drilling projects and operating a lot of plumbing to get energy out of it.

An example of a battery that is pretty cheap is a thermal mass based batteries. It is basically the same material (i.e. rocks) plus some insulator. Given enough mass, you can store quite large amounts of energy for very long and there are some companies starting to do exactly that. Several companies are working on those. It's all going to boil down to cost per kwh in the end. wind and solar converging on about a cent per kwh. Batteries tend to be more expensive but still cheaper than burning gas/coal. Geothermal sits somewhere in between. It could be cheaper in some places long term. But then batteries are also getting cheaper.

Re: Geothermal's path to relevance: cheap drilling

#69

Post by HPsquared »

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 power is based on a heat engine: a machine which produces usable energy (e.g. electricity) out of the transfer of heat from a high-temperature heat source to a low-temperature heat sink (a process which would happen naturally, given a transfer process).

A ground-source heat pump is a heat pump: a machine which consumes usable energy in order to move heat from a LOW-temperature heat source to a HIGH-temperature heat sink (a process which would not occur naturally without energy input due to the 2nd law of thermodynamics).

Re: Geothermal's path to relevance: cheap drilling

#70

Post by DoingIsLearning »

avernon wrote: post #38
chris_va wrote: post #32

Drilling cost is usually estimated as ~depth^2. So, a 1km geothermal well? Break even, and you are limited to only a few places in the world. A 5km geothermal well (needed for broad power availability)? 25x the cost... So, sure, if you can get a 25x cost reduction in an already cutthroat industry, all power to you (no pun intended).

Drilling cost is usually estimated for drilling in sedimentary rock with assumptions about how casing is run ;) It is possible that drilling 30,000' of granite has conditions that make the estimation model irrelevant. 5 km isn't really deep enough, anyway. My next post will cover the thermo. It is pretty dang hard to get down to anything approaching $50/MWh. Definitely need more than cheap drilling.

It is important that we discuss cost, but I think the urgency of our need for mass generating non-intermitent power should override costs.

As an example Solar energy as it exists now would have been ridiculed in the late 80s as something that would never be cost effective.

It was the massive subsidies/tax rebate schemes in Germany and later on in other EU countries that open the window for manufacturers to produce at scale and make it the cost competitive source of energy that we see now.

I mentioned this in a previous comment on a biomass thread. We would be better off with EU funds allocated to solving the massification of geo-thermal or the massification of small vessel nuclear reactors, than to continue to pour money into converting coal plants into natural gas plants and opening up new biomass furnaces.

Natural gas and biomass are just a means for governments to play with statistics on 'renewable' pie-charts. Until we solve the problem of mass energy storage of intermitent renewables or a far away nuclear fussion we need to start _now_ deploying non-carbon emitting non-intermitent energy generation.

We have to be realistic and accept that we need to find a means of replacing coal and not all regions have the resources for hydro-generation, geo-thermal is the next best bet considering the time and friction it would take to roll out more nuclear for example.

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