The Death Of Fossil Fuels

Discussions about serious topics, for serious people
Post Reply
User avatar
bjn
Stummy Beige
Posts: 2970
Joined: Wed Sep 25, 2019 4:58 pm
Location: London

Re: The Death Of Fossil Fuels

Post by bjn » Wed May 15, 2024 10:49 am

Global battery based grid storage deployment is accelerating rapidly. In terms of GWh it is set to overtake pumped hydro next year.
In 2020 17.6GW BESS vs 159.5GW PHES (90% PHES)
In 2021 27.3GW BESS vs 165.0GW PHES (86% PHES)
In 2022 44.9GW BESS vs 175.0GW PHES (80% PHES)
In 2023 89.2GW BESS vs 185.5GW PHES (68% PHES)
In 2024e 156.6GW BESS vs 196.6GW PHES (56% PHES)
Battery electricity storage systems are still dropping down the learning curve and are much faster to deploy than pumped hydro. Pumped hydro does store more GWh, but for diurnal and short term storage, batteries are going to take over. Pumped hydro complements battery electric storage quite well, filling in for longer durations.

User avatar
bjn
Stummy Beige
Posts: 2970
Joined: Wed Sep 25, 2019 4:58 pm
Location: London

Re: The Death Of Fossil Fuels

Post by bjn » Wed May 15, 2024 12:27 pm

bjn wrote:
Wed May 15, 2024 10:49 am
Global battery based grid storage deployment is accelerating rapidly. In terms of GWh it is set to overtake pumped hydro next year.
In 2020 17.6GW BESS vs 159.5GW PHES (90% PHES)
In 2021 27.3GW BESS vs 165.0GW PHES (86% PHES)
In 2022 44.9GW BESS vs 175.0GW PHES (80% PHES)
In 2023 89.2GW BESS vs 185.5GW PHES (68% PHES)
In 2024e 156.6GW BESS vs 196.6GW PHES (56% PHES)
Battery electricity storage systems are still dropping down the learning curve and are much faster to deploy than pumped hydro. Pumped hydro does store more GWh, but for diurnal and short term storage, batteries are going to take over. Pumped hydro complements battery electric storage quite well, filling in for longer durations.
Missed the edit window. That second sentance should read In terms of GW not GWh.

IvanV
Stummy Beige
Posts: 2848
Joined: Mon May 17, 2021 11:12 am

Re: The Death Of Fossil Fuels

Post by IvanV » Wed May 15, 2024 12:38 pm

bjn wrote:
Wed May 15, 2024 10:49 am
Battery electricity storage systems are still dropping down the learning curve and are much faster to deploy than pumped hydro. Pumped hydro does store more GWh, but for diurnal and short term storage, batteries are going to take over. Pumped hydro complements battery electric storage quite well, filling in for longer durations.
Most grid batteries have about 2 to 4 hours storage at their maximum output rate, though occasionally you see longer. Their cost is such that the longer period is not usually economic.

Whilst PHES operates well over a longer time period, it typically has only about 12 hours storage. We need a kind of storage that is economic over much longer periods to smooth out the supply from intermittent renewables. I suspect the practical mechanism for that will be some kind of chemical storage, because storing energy-dense substances is the more practical method for long-term, as such things can be much cheaper to store. Essentially, things you can store like you can store relatively easily like coal, methane, etc, but used in a round-trip rather than burnt once.

Hydrogen is an example of that, though storing it is harder than methane. I recently saw an article recently on using elemental sulphur for chemical storage, simply because it is so easy to store - you can just leave it in an outdoor heap. Though the chemical round trip is more complicated than with hydrogen. A demonstration scheme for using elemental iron has as storage has been exhibited also, though I've not come across anyone replicating it. Probably it isn't going to happen until we get a bit more desirous of cutting down on methane.

User avatar
dyqik
Princess POW
Posts: 7671
Joined: Wed Sep 25, 2019 4:19 pm
Location: Masshole
Contact:

Re: The Death Of Fossil Fuels

Post by dyqik » Wed May 15, 2024 1:17 pm

bjn wrote:
Wed May 15, 2024 12:27 pm
bjn wrote:
Wed May 15, 2024 10:49 am
Global battery based grid storage deployment is accelerating rapidly. In terms of GWh it is set to overtake pumped hydro next year.
In 2020 17.6GW BESS vs 159.5GW PHES (90% PHES)
In 2021 27.3GW BESS vs 165.0GW PHES (86% PHES)
In 2022 44.9GW BESS vs 175.0GW PHES (80% PHES)
In 2023 89.2GW BESS vs 185.5GW PHES (68% PHES)
In 2024e 156.6GW BESS vs 196.6GW PHES (56% PHES)
Battery electricity storage systems are still dropping down the learning curve and are much faster to deploy than pumped hydro. Pumped hydro does store more GWh, but for diurnal and short term storage, batteries are going to take over. Pumped hydro complements battery electric storage quite well, filling in for longer durations.
Missed the edit window. That second sentance should read In terms of GW not GWh.
No, it shouldn't. Because you can't store power, you can only store energy.

User avatar
bjn
Stummy Beige
Posts: 2970
Joined: Wed Sep 25, 2019 4:58 pm
Location: London

Re: The Death Of Fossil Fuels

Post by bjn » Wed May 15, 2024 1:45 pm

I’m well aware of the difference between power and energy. Apart from my stupid typo, how is that statement incorrect? It was explicitly a statement about power, not energy.

User avatar
dyqik
Princess POW
Posts: 7671
Joined: Wed Sep 25, 2019 4:19 pm
Location: Masshole
Contact:

Re: The Death Of Fossil Fuels

Post by dyqik » Wed May 15, 2024 1:56 pm

bjn wrote:
Wed May 15, 2024 1:45 pm
I’m well aware of the difference between power and energy. Apart from my stupid typo, how is that statement incorrect? It was explicitly a statement about power, not energy.
The corrected sentence would read "Pumped hydro does store more power, but for diurnal and short term storage, batteries are going to take over."

You cannot store power. Do you mean that it stores more energy (in GWh) or do you mean that it can release stored energy at a higher rate (in GW)? As corrected, the sentence does not say either of those things.

User avatar
bjn
Stummy Beige
Posts: 2970
Joined: Wed Sep 25, 2019 4:58 pm
Location: London

Re: The Death Of Fossil Fuels

Post by bjn » Wed May 15, 2024 3:48 pm

The second sentence, where my typo was, should have read....
Global battery based grid storage deployment is accelerating rapidly. In terms of GW it is set to overtake pumped hydro next year.
I said nothing about changing GWh -> GW in the second paragraph.

I should have just reposted the whole thing.

IvanV
Stummy Beige
Posts: 2848
Joined: Mon May 17, 2021 11:12 am

Re: The Death Of Fossil Fuels

Post by IvanV » Wed May 15, 2024 4:16 pm

Electricity storage has two aspects, the energy stored measured in Wh, and the output, measured in W. For the kind of short-term grid services that grid scale batteries are mostly designed to supply, their power in W is more important than their capacity in Wh, because they are mostly only called for short periods of time. So their owners tend to size them by reporting their power in W, rather than their capacity in Wh, as it is the W that earns them money.

This has an unfortunate effect that the less informed tend to go, look how huge this battery storage is, it is on the way to solving our renewable intermittency problems. But clearly to know if we have a solution to renewable intermittency problems, then capacity becomes important. And these batteries have relatively low capacity in comparison to their power output.

In fact, we are reaching the point in Britain that there is so much grid scale battery already available, that the grid has about as much of that kind of short-term storage as it needs. The market price of that kind of service is starting to drop more because of supply conditions than demand conditions.

Another place where large scale batteries can be useful is for smoothing demand and supply at EV fast charging stations. Probably they will be used over a somewhat longer period than for supplying grid services.

User avatar
dyqik
Princess POW
Posts: 7671
Joined: Wed Sep 25, 2019 4:19 pm
Location: Masshole
Contact:

Re: The Death Of Fossil Fuels

Post by dyqik » Wed May 15, 2024 6:16 pm

bjn wrote:
Wed May 15, 2024 3:48 pm
The second sentence, where my typo was, should have read....
Global battery based grid storage deployment is accelerating rapidly. In terms of GW it is set to overtake pumped hydro next year.
I said nothing about changing GWh -> GW in the second paragraph.

I should have just reposted the whole thing.
Sorry, I didn't even see that paragraph.

User avatar
bjn
Stummy Beige
Posts: 2970
Joined: Wed Sep 25, 2019 4:58 pm
Location: London

Re: The Death Of Fossil Fuels

Post by bjn » Wed May 15, 2024 7:07 pm

My bad, I should have made the edit explicit in the text, less chance for talking at cross porpoises angry dolphins.

User avatar
bjn
Stummy Beige
Posts: 2970
Joined: Wed Sep 25, 2019 4:58 pm
Location: London

Re: The Death Of Fossil Fuels

Post by bjn » Wed May 15, 2024 8:01 pm

Back to the topic. Talking of grid services, batteries can help alleviate transmission capacity bottle necks. Transmission is traditionally built to service peak demand, but peak demand doesn’t last for days on end. So you are seeing batteries installed at the “far end” of distribution systems to service peak demand and so avoid having to upgrade trunk power lines. For example one of the inhabited island off the USA (Martha’s Vineyard I think) has a a battery system built to avoid spending a small fortune upgrading the power cable from the mainland.

In Sydney they are installing batteries in neighbourhoods near the transformers, which lets them avoid upgrading distribution lines which were getting overloaded both ways. On sunny days they couldn’t handle all the solar being dumped back into the grid, on peak days they couldn’t cope with demand placed on the grid.

This scales down to the domestic level. People are building electric cookers with batteries on board. You don’t run a cooker at full power for hours on end, it heats up and then maintains a steady temperature with a much lower power draw, but you need a dedicated circuit handle that peak power. Bung an appropriately sized battery in the thing and you can run a cooler off a standard plug.

IvanV
Stummy Beige
Posts: 2848
Joined: Mon May 17, 2021 11:12 am

Re: The Death Of Fossil Fuels

Post by IvanV » Thu May 16, 2024 11:21 am

bjn wrote:
Wed May 15, 2024 8:01 pm
Back to the topic. Talking of grid services, batteries can help alleviate transmission capacity bottle necks. Transmission is traditionally built to service peak demand, but peak demand doesn’t last for days on end. So you are seeing batteries installed at the “far end” of distribution systems to service peak demand and so avoid having to upgrade trunk power lines. For example one of the inhabited island off the USA (Martha’s Vineyard I think) has a a battery system built to avoid spending a small fortune upgrading the power cable from the mainland.

In Sydney they are installing batteries in neighbourhoods near the transformers, which lets them avoid upgrading distribution lines which were getting overloaded both ways. On sunny days they couldn’t handle all the solar being dumped back into the grid, on peak days they couldn’t cope with demand placed on the grid.

This scales down to the domestic level. People are building electric cookers with batteries on board. You don’t run a cooker at full power for hours on end, it heats up and then maintains a steady temperature with a much lower power draw, but you need a dedicated circuit handle that peak power. Bung an appropriately sized battery in the thing and you can run a cooler off a standard plug.
Using large batteries to alleviate transmission capacity bottlenecks is one of the most valuable uses of batteries, according to some research leading energy economist David Newbery showed me a few years ago. But this only works if they are in the right place. So if you have some big battery in some random place, it can't provide that service. Which is why I'm saying the market for big batteries in (kind of) random places, able to provide high level short term grid services, is being exhausted. But that doesn't mean that there isn't substantial value for batteries in other locations.

A problem in many places is that there aren't mechanisms for remunerating batteries that provide bottleneck alleviation services. Often this is something that is required and goes on down at the distribution level, rather than high level transmission level, where charging mechanisms are very flat, and there is no mechanism for doing this. So it is down for distribution companies to do this off their own bat, and maybe the regulatory mechanisms don't suit it either.

User avatar
bolo
Dorkwood
Posts: 1031
Joined: Mon Nov 11, 2019 1:17 pm
Location: Washington DC

Re: The Death Of Fossil Fuels

Post by bolo » Thu May 16, 2024 11:45 am

In California, there are enough houses with PV on the roof, selling their excess back to the grid, that on some days the daytime price of electricity is zero. As a result, some homeowners are buying batteries so they can save up their excess and sell it back at night instead.

User avatar
Grumble
Light of Blast
Posts: 4877
Joined: Mon Nov 11, 2019 1:03 pm

Re: The Death Of Fossil Fuels

Post by Grumble » Fri May 17, 2024 2:34 pm

bolo wrote:
Thu May 16, 2024 11:45 am
In California, there are enough houses with PV on the roof, selling their excess back to the grid, that on some days the daytime price of electricity is zero. As a result, some homeowners are buying batteries so they can save up their excess and sell it back at night instead.
California could do with electrifying a lot more stuff from what I read.
where once I used to scintillate
now I sin till ten past three

IvanV
Stummy Beige
Posts: 2848
Joined: Mon May 17, 2021 11:12 am

Re: The Death Of Fossil Fuels

Post by IvanV » Fri May 17, 2024 3:54 pm

bolo wrote:
Thu May 16, 2024 11:45 am
In California, there are enough houses with PV on the roof, selling their excess back to the grid, that on some days the daytime price of electricity is zero. As a result, some homeowners are buying batteries so they can save up their excess and sell it back at night instead.
In Britain, these days it is now pretty much routine to get a battery when you install solar, even though we don't have that issue. It's mostly about being able to use more of your own electricity, and reducing the amount you sell back to the grid, as the price you get for selling is typically rather less than the price you buy electricity at. Time of use tariffs are relatively uncommon for domestic customers, and certainly not yet enforced on them.

But time-of-use tariffs are available for domestic customers, if they choose, and that gives them the ability to arbitrage the price. Typically you top up your battery from the grid - rather than PV - in the middle of the night when electricity is cheap to sell it back in when it is more expensive. So a similar idea, except the cheap excess electricity is typically at a different time of day. A friend of mine is doing that. My own equipment is insufficiently smart to do it. Of course it cycles your battery a lot more, so may reduce the life of your battery.

Though they have just brought in a new regulation that you must not put batteries in lofts, roofspaces, or voids. Presumably there is some greater fire risk. But this is typically the most convenient place to put them. My friend got his battery installed in his loft very shortly before that came in. So that is likely to complicate solar installations... Mine is in an outdoor cabinet, such was the difficulty of finding somewhere acceptable in the house.

IvanV
Stummy Beige
Posts: 2848
Joined: Mon May 17, 2021 11:12 am

Re: The Death Of Fossil Fuels

Post by IvanV » Tue Jun 11, 2024 5:16 pm

The thermodynamics of direct air capture of CO2 (Wired)

This article demonstrates from thermodynamics the minimum amount of energy required to capture CO2 from the air at ambient concentrations and temperatures. It comes out at 652kJ/kg.

The author then asks how much power would you need to capture all the CO2 the world is currently emitting, and it comes to 764GW. It didn't exhibit the whole calculation of that, but I checked the bits it didn't show and came to the same answer.

It then laughed at that number, and said that's a lot. Must be a complete waste of time then.

I'm not terribly fond of proof by derision. I remember William Happer, President Trump's climate advisor correctly calculating the climate forcing from CO2, and then asserting by derision that was "obviously" immaterial as it was a small number. But of course he was wrong about that bit.

I did the same calculation for the UK's CO2 emissions of 406 million tonnes per year, and got to 8.4 GW to remove it. And that's all of it, not just from the electricity system. About 20% of the UK's energy consumption is electricity, so our consumption is about 150GW. So we are talking about 5% extra energy consumption to remove all the UK carbon dioxide by DAC. In those terms, that's quite a plausible expenditure of effort. Of course, the amount is a thermodynamic minimum and 50% is usually quite good efficiency in this kind of thing, so I guess in reality we are talking double. But even at double, it doesn't seem totally implausible.

Of course, there are much better easier ways to decarbonise than DAC for a large part of our energy consumption. No one is realistically proposing DAC for the lot. So the article sought to demolish a straw man, and I would say failed to demolish it. And if you were capturing CO2, you would first go for those localities where CO2 has a much higher concentration, like the source that is emitting it. There you get a thermodynamic advantage you wouldn't have when capturing it from ambient air. But I would say that, rather than proving that DAC is bonkers, it really failed even to demolish the straw man it sought to demolish. And in reality showed that DAC is potentially quite promising for hard-to-decarbonise sources, if you can get enough efficiency in the engineering. I don't know what efficiencies have actually been achieved.

I've long thought, even in a decarbonised future, if you want to buy some camping gas, say, then just pay to have its carbon content captured. There should be some system where you pay a charge, and someone actually does that removal.

User avatar
shpalman
Princess POW
Posts: 8363
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond
Contact:

Re: The Death Of Fossil Fuels

Post by shpalman » Tue Jun 11, 2024 6:04 pm

https://en.wikipedia.org/wiki/Energy_in ... ed_Kingdom says that "Demand for electricity in 2023 was 29.6 GW on average"

But it's fairly obvious to me that if a country is mainly using fossil fuels to meet its energy needs then it will need at least the same amount of energy again (from a non-fossil source) to get the CO2 back out of the air.

Efficiency of photosynthesis is about 3-6% apparently but we may be able to engineer something better https://en.wikipedia.org/wiki/Photosynthetic_efficiency
having that swing is a necessary but not sufficient condition for it meaning a thing
@shpalman@mastodon.me.uk

IvanV
Stummy Beige
Posts: 2848
Joined: Mon May 17, 2021 11:12 am

Re: The Death Of Fossil Fuels

Post by IvanV » Tue Jun 11, 2024 8:27 pm

shpalman wrote:
Tue Jun 11, 2024 6:04 pm
https://en.wikipedia.org/wiki/Energy_in ... ed_Kingdom says that "Demand for electricity in 2023 was 29.6 GW on average"

But it's fairly obvious to me that if a country is mainly using fossil fuels to meet its energy needs then it will need at least the same amount of energy again (from a non-fossil source) to get the CO2 back out of the air.

Efficiency of photosynthesis is about 3-6% apparently but we may be able to engineer something better https://en.wikipedia.org/wiki/Photosynthetic_efficiency
I took av UK electricity demand is 30GW, usual rule of thumb, and electricity is 20% of total energy demand - I thought it was that but checked it, it was near enough - to get to 150GW-equiv av total energy demand for the country.

So when the article gives a calculation that suggests we can DAC our entire emissions, not just from electricity, for (at least) 8.4GW, that is a much smaller number than "same again" that your intuition suggested. Of course that is a thermodynamic minimum, real numbers probably start north of 15GW. I don't know how well people have done with practical equipment. But the point is, it is - or the thermodynamic minimum is - much smaller than the number we might guess. That is why I was saying the article actually failed to show what it purported to show. It tried to show that number was large, but in fact it showed it was potentially much smaller than you might guess.

User avatar
Grumble
Light of Blast
Posts: 4877
Joined: Mon Nov 11, 2019 1:03 pm

Re: The Death Of Fossil Fuels

Post by Grumble » Tue Jun 11, 2024 9:29 pm

IvanV wrote:
Tue Jun 11, 2024 8:27 pm
shpalman wrote:
Tue Jun 11, 2024 6:04 pm
https://en.wikipedia.org/wiki/Energy_in ... ed_Kingdom says that "Demand for electricity in 2023 was 29.6 GW on average"

But it's fairly obvious to me that if a country is mainly using fossil fuels to meet its energy needs then it will need at least the same amount of energy again (from a non-fossil source) to get the CO2 back out of the air.

Efficiency of photosynthesis is about 3-6% apparently but we may be able to engineer something better https://en.wikipedia.org/wiki/Photosynthetic_efficiency
I took av UK electricity demand is 30GW, usual rule of thumb, and electricity is 20% of total energy demand - I thought it was that but checked it, it was near enough - to get to 150GW-equiv av total energy demand for the country.

So when the article gives a calculation that suggests we can DAC our entire emissions, not just from electricity, for (at least) 8.4GW, that is a much smaller number than "same again" that your intuition suggested. Of course that is a thermodynamic minimum, real numbers probably start north of 15GW. I don't know how well people have done with practical equipment. But the point is, it is - or the thermodynamic minimum is - much smaller than the number we might guess. That is why I was saying the article actually failed to show what it purported to show. It tried to show that number was large, but in fact it showed it was potentially much smaller than you might guess.
Is that 20% of primary energy or 20% of useful energy?
where once I used to scintillate
now I sin till ten past three

IvanV
Stummy Beige
Posts: 2848
Joined: Mon May 17, 2021 11:12 am

Re: The Death Of Fossil Fuels

Post by IvanV » Tue Jun 11, 2024 9:50 pm

Grumble wrote:
Tue Jun 11, 2024 9:29 pm
Is that 20% of primary energy or 20% of useful energy?
Not primary, at point of usage, sometimes misleadingly called "final energy consumption". Primary electricity was 11% in 2021.

User avatar
bjn
Stummy Beige
Posts: 2970
Joined: Wed Sep 25, 2019 4:58 pm
Location: London

Re: The Death Of Fossil Fuels

Post by bjn » Wed Jun 12, 2024 9:42 am

My back of the envelope (well spreadsheet) calculation for carbon dioxide air capture says we need to process 4.48x10^12 cubic metres of air per hour to scrub current global emissions. To keep the airflow less than supersonic at the inlet of your CC devices, they would need to be or 3.6km^2. At a more reasonable beaufort 4 windspeed (25km/h), you would need just under 200km^2 of inlet.

These aren't solar panels you can pretty much layout many square kms and forget about them, except for a bit of dusting. They are complex machines with moving parts. Capital cost and maintainence cost will be non trivial, to say the least.

I'd have included my spreadsheet, but it won't let me. Screenshot instead. 'm' is metres, not miles.
Attachments
Screenshot 2024-06-12 at 10.43.49.png
Screenshot 2024-06-12 at 10.43.49.png (279.93 KiB) Viewed 200 times

User avatar
shpalman
Princess POW
Posts: 8363
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond
Contact:

Re: The Death Of Fossil Fuels

Post by shpalman » Wed Jun 12, 2024 11:19 am

But I don't think anyone would be suggesting building one huge machine to deal with the whole world's emissions. Why don't you try to figure out how many reasonably sized machines the UK would need?
having that swing is a necessary but not sufficient condition for it meaning a thing
@shpalman@mastodon.me.uk

User avatar
Grumble
Light of Blast
Posts: 4877
Joined: Mon Nov 11, 2019 1:03 pm

Re: The Death Of Fossil Fuels

Post by Grumble » Wed Jun 12, 2024 11:26 am

shpalman wrote:
Wed Jun 12, 2024 11:19 am
But I don't think anyone would be suggesting building one huge machine to deal with the whole world's emissions. Why don't you try to figure out how many reasonably sized machines the UK would need?
I don’t think he was suggesting one big machine
where once I used to scintillate
now I sin till ten past three

User avatar
shpalman
Princess POW
Posts: 8363
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond
Contact:

Re: The Death Of Fossil Fuels

Post by shpalman » Wed Jun 12, 2024 11:26 am

IvanV wrote:
Tue Jun 11, 2024 9:50 pm
Grumble wrote:
Tue Jun 11, 2024 9:29 pm
Is that 20% of primary energy or 20% of useful energy?
Not primary, at point of usage, sometimes misleadingly called "final energy consumption". Primary electricity was 11% in 2021.
The CO2 which ends up in the atmosphere from fossil fuel usage corresponds to the primary not the useful. Electricity generation is, what, about 30% efficient? Maybe higher for gas-fired power.

But obviously if you were generating all your energy from fossil fuels you wouldn't have enough energy to reduce all the CO2 back to hydrocarbon form, otherwise we'd have invented perpetual motion. Unless there's some subtlety in the enthalpies of formation of the captured carbon compared to the original fossil fuels which overrides the inherent inefficiency.
having that swing is a necessary but not sufficient condition for it meaning a thing
@shpalman@mastodon.me.uk

IvanV
Stummy Beige
Posts: 2848
Joined: Mon May 17, 2021 11:12 am

Re: The Death Of Fossil Fuels

Post by IvanV » Wed Jun 12, 2024 12:02 pm

shpalman wrote:
Wed Jun 12, 2024 11:26 am
But obviously if you were generating all your energy from fossil fuels you wouldn't have enough energy to reduce all the CO2 back to hydrocarbon form, otherwise we'd have invented perpetual motion. Unless there's some subtlety in the enthalpies of formation of the captured carbon compared to the original fossil fuels which overrides the inherent inefficiency.
Obviously. But no one is seeking to sequester carbon dioxide by chemical reduction, that would take up more energy than you got from it, as you say. There are in fact energetically favourable ways of sequestering carbon. But mostly people propose pumping it into a hole in the ground, as we have lots of holes in the ground to store away lots of CO2. The more permanent solution is to get the CO2 to combine chemically with basalt in the presence of water, to form stable rocks, which is energetically favourable, but requires suitable temperatures and pressures to happen at an appreciable rate. Experiments near at the power station near that current volcanic eruption in Iceland have succeeded in demonstrating it, though it's a bit slow, takes place over months rather than seconds. But apparently there are enough impermeable voids in the ground, depleted gas fields for example, to store enormous centuries worth of CO2 until we find more permanent sequestration..

The calculation in the Wired article only looks at the energetic cost of capturing the carbon from the air. Essentially that treats the sequestration as energetically free, which thermodynamically is true - the combination of wet basalt and CO2 is energetically favourable, just very slow. So far, there has been a lot of focus on carbon sequestration, but actually the carbon capture is the more difficult bit. People think about capturing carbon from vents of power stations, and think it must be straightforward to capture it all. But actually the processes tested so far capture quite disappointing proportions of it. You'd have to be capturing 90%+ of the CO2 from a methane power station to get something properly worthwhile, and I don't think anything near that has been demonstrated at scale.

Post Reply