CAES Compressed Air Energy Storage

tahanson43206 · 2024-09-13 07:46:42

This topic is offered because several members have included CAES references in posts in other topics.

The most recent post by Calliban, showing the outlines of a practical system for Mars, inspires this topic.

This topic is intended to provide a place for a vision of a clean CAES system, whatever that might mean in the context of a particular situation.

This line is provided for a link that was posted by Void, to a 2008 study of CAES on Earth
https://www.livescience.com/4955-compre … lectricity

This line is provided to link to a post by Calliban showing a practical application of CAES on Mars.
http://newmars.com/forums/viewtopic.php … 98#p226498

(th)

tahanson43206 · 2024-09-13 07:47:20

This post is reserved for an index to posts that may be contributed by NewMars members over time.

This topic was opened with as wide a range for posts as possible, so long as compressed gas is in the post somewhere.

With this in mind, a post by kbd512 includes a comment on the idea of storing CAES in abandoned oil wells.

https://newmars.com/forums/viewtopic.ph … 20#p226620

Update 2024/10/01 .... here is a post by Calliban that describes advances in concrete technology for CAES ...
http://newmars.com/forums/viewtopic.php … 05#p226905

(th)

Calliban · 2024-09-13 08:58:58

Compressed CO2 energy storage, which is of course CAES for Mars.
https://en.m.wikipedia.org/wiki/Compres … gy_storage

A cubic metre of L-CO2 has stored potential energy of 66.7kWh and a density of 1100kg/m3, so 0.06kWh/kg. The same technology can work on Earth, but it does require an expansion dome to capture the expanded CO2 for recompression. On Mars, there is an endless supply in the atmosphere. For Earth, this is arguably a more promissing technology for home energy storage than CAES or vacuum energy storage because the L-CO2 has substantially superior energy density. The exansion tank is an ambient pressure balloon and need not be a pressure vessel.

At standard conditions, CO2 is a gas with density 1.8kg/m3. A 2m wide, 5m tall expansion tank attached to a house, could store 28kg of CO2. This could be compressed into a 26 litre pressure cylinder, storing 1.7kWh of energy. This is something that would work even for homes will comparatively little space.

tahanson43206 · 2024-09-13 09:20:48

For Calliban re #3

Thanks for helping to build this new topic ...

Is the potential energy you've shown (66.7kWh) due to phase change alone? In other words, is that energy achieved without changing the temperature?

I have no way of knowing if you read the article that Void showed us from 2008. The key element that the article revealed was/is an attempt to manage heat as part of the CAES system. The ideal would be to capture ** all ** the thermal energy so it can be used to restore the gas in order to perform work against a turbine or other mechanical translation device. Is the CO2 system you are describing potentially able to do that. According to the article, saving the thermal energy dramatically improves performance of the storage system.

Please note that you are creating IP as you design this system online. Thank you for generously contributing to the shared IP of the NewMars readership.

(th)

Terraformer · 2024-09-14 04:36:14

Hmm, 60Wh/kg? Good enough to power Martian vehicles, equipment?

SpaceNut · 2024-09-14 07:31:06

Thats like the issue for gasoline engines as we only convert 25% of that potential energy due to equilibrium being 50%. So far only the solar thermal conversion is higher.

The energy equivalent of a gallon of gasoline is approximately 33.7 kWh or 1.213x10^8 joules. A gallon of gasoline contains the equivalent of 36 kWhs of electrical energy. Alternatively, a gallon of gasoline is equivalent in energy terms to 4 kilowatt hours

tahanson43206 · 2024-09-14 07:34:12

For SpaceNut re #6.... What are you replying to?

What is "like the issue of gasoline engines"?

(th)

kbd512 · 2024-09-15 02:58:19

On Mars 1,100kg of LCO2 only weighs 418kg. Let's assert that our rover weighs 1,500kg on Mars with a pair of suit astronauts, so Earth weight is about 3,950kg. That's a beast of a vehicle, not some dinky little ATV. The Hummer H1 4-door has a curb weight of 3,559kg and a payload capacity of 1,113kg here on Earth. H1 or "military" Hummers were initially equipped with a 160hp naturally aspirated diesel engine, which was later replaced with modestly more powerful turbo-diesels. On Mars it would require 60.8hp to achieve its top road speed of 89km/hr at max gross weight.

Let's assert that we need a 12.33kW / 16.5hp air turbine to propel this vehicle at about 25km/hr. We can make a 61hp air turbine. A 4.5kW / 6hp air turbine only weighs about 2kg, so something 10X as powerful won't weigh much more than 20kg. However, we'll have a pair of them to power each pair of wheels. To each air turbine, we'll attach a flywheel and suitable gearbox to increase torque. We'll have a pair of spherical LCO2 tanks with 0.5m^3 of capacity per tank, located just inboard of where each axle would be. Each tank is about the same weight and volume as the Duramax diesel engine that powered the final incarnation of the H1 Hummer.

Even if your name was Usain Bolt, you can't run at that speed, unencumbered by a space suit, for 1 hour. That means the vehicle is quite useful, even at relatively low speeds. We'll presume 70% efficiency for the air motor, because this is typical of a decent air turbine design, rather than the best or worst overall efficiency. That means we actually need 17,614Wh of power from the expanding CO2 to achieve 25km/hr. We need 294kg of LCO2 to provide power for 1 hour. We have about 3.75 hours of power, while covering 93.5km.

I don't know how many Watts of thermal input power are required to double the volume of gas fed into the air turbine, but you're only generating, via expanding gas, 4.893 Watts of power per second. One would think that a nuclear decay heat source, such as Strontium-90, could feasibly double the gas volume and therefore double how far that rover can travel before it runs out of CO2. 187km / 117 miles is a lot farther than a person wearing a space suit could feasibly walk in a day. By including a radiator to perform thermal power transfer using a Strontium-90 heat source, the vehicle could theoretically, albeit slowly, recharge its own LCO2 tanks overnight by running a pump to compress more CO2.

I'm quite sure you could get more range from a Lithium-ion battery, but batteries require electricity, electrical power control requires fully functional micro-electronics to regulate battery charge / discharge, as well as the power from the electric motor, and space radiation does a number on electronics that are not rad-hardened. They work perfectly, until they don't, and then you'd better have a solid "Plan B". With LCO2, if you have gas in your gas tanks, then the power turbines will produce power. They're just not very fussy. Messing them up requires a good deal more effort. Recharging the tank can be accomplished in a matter of minutes. You don't need to wait all day to recharge.

When you have one of these, you probably don't need ATVs:

kbd512 · 2024-09-15 15:18:20

Actual dry ice bulk density is around 1,000kg/m^3, very similar to water, even though it's technically 1,600kg/m^3. LCO2 bulk density is modestly higher, at around 1,100kg/m^3, as Calliban already pointed out.

Here's a "design guide" for LCO2 pumping equipment:
Liquid Carbon Dioxide Design Guide

The design guide establishes acceptable pumping criteria for liquid vs gaseous vs supercritical CO2.

The tank will require a heat source to maintain its pressure, thus it's really a pressure vessel even if it's storing super-cold dry ice vs LCO2. To get the dry ice out of the pressure vessel, it needs to be gas or liquid. We cannot work with a solid. If it's a solid, it's also super-cold, which means less readily extractable energy is available when expanding it through an air turbine. Ideally, we want supercritical CO2, but a liquid maintained at room temperature is also fine. I'd rather store the collected CO2 as a denser liquid or supercritical fluid, rather than a theoretically denser solid that's not actually as dense as its liquid form, then use a heating element to add thermal energy to the gas just before it's expanded through an air turbine.

The heating element can be electrical or it can be nuclear, but doubling the volume of gas requires quite a bit of energy input, so a nuclear heat source is better. A nuclear heating element doesn't require any electrical or electronic devices. Strontium-90 has a surface temperature of 700C to 800C, so that's a good place to start.

To achieve 16.5hp, our gravimetric flow rate is 4.8927kg/min, or 0.0815kg/sec. We need to input 849J/kg⋅°C, or 69.233J/sec. That equates to 69.233W. However, to achieve 61hp, we need a heat transfer rate of 256W per second. 1kW is the same as 1,000J/s, so I presume our in-line heater consists of about 560g of Sr-90. We may as well use 1kg of Sr-90 per machine, which should account for output decline over as it approaches its half life and other heat losses. I'm also forgetting that Sr90TiO3 is not as energy dense as pure Sr90, so only 1kg is probably close to the minimum amount required, rather than an optimal amount for 20+ years of driving. I think we still have enough heavy metal to do this.

Our waste Sr-90 nuclear waste recovery rate from four selected government-operated reactors, is or could be about 100,000Wth per year. That's only enough for 217 vehicles per year. This is also sourced from a Savannah River document from 1982. Hanford, for example, has been shut down for quite some time now. However, it's 3% to 4% of all the high level nuclear waste that we don't reprocess, so there's actually an enormous quantity of the stuff. We produce 2,000t of high level waste each year, which equates to 60,000kg of Sr-90 per year, which is enough for 30,000 vehicles per year.

RADIOISOTOPES FOR HEAT-SOURCE APPLICATIONS

Calliban · 2024-09-15 16:12:50

Sr-90 accounts for 4.5% of total fission product yield. By my estimation, a 1000MWe reactor will produce some 34kg of Sr-90 per year.
https://en.m.wikipedia.org/wiki/Fission_product_yield

The US has about 100GWe of nuclear generating capacity. If all of this fuel were reprocessed, it would yield 3.4 tonnes of Sr-90 every year. Even more could be extracted from legacy fuel.

There are other isotopes that could be extracted and used as well. Cs-137 is a bit more tricky, but it could be used if we surrounded it with phase change heat storage material that also provided shielding. But Sr-90 is one of the best isotopes in terms of total energy released per unit mass. I would propose a liquid alloy of strontium and lithium. That would minimise x-ray emissions from beta particle interactions.

Last edited by Calliban (2024-09-15 16:21:27)

kbd512 · 2024-09-15 16:47:32

Calliban,

Argh! You're right. I forgot that only a very small percentage of the fuel has actually fissioned. Well, that throws a bit of a damper into the production pipeline, but we also have decades of unprocessed waste.

Calliban · 2024-09-15 17:25:46

kbd512 wrote:

Calliban,
Argh! You're right. I forgot that only a very small percentage of the fuel has actually fissioned. Well, that throws a bit of a damper into the production pipeline, but we also have decades of unprocessed waste.

Correct. Sr-90 is by far the most useful fission product as far as RTGs are concerned. It has a half-life of 30 years. So in the past 30 years of spent fuel, we would expect to find about 80 tonnes of Sr-90, if reprocessing were employed. Now would be a good time to start reprocessing in north America. The Ukraine conflict is resulting in a shortage of enriched uranium. Reprocessing would reduce the potential for supply shortages. I think it could realistically reduce uranium demand by about one third in the existing fleet. Maybe something Trump can get the ball rolling on assuming he is successful in November.

Other options for a Mars vehicle would be a small mobile fission reactor, which has been discussed before on this board. If NASA are successful in developing their LCF fast-fission reactor, it would be a strong contender. A portable solar thermal collector would work as well, though it would be less versatile. In the long run on Mars, we will have a domestic nuclear industry with its own reprocessing programme. I would expect a great deal of isotopes from waste streams to be redirected into productive applications. This takes care of the waste problem to a substantial degree, given that waste by definition is something that isn't being used. On Mars, it won't make sense to waste raw materials.

tahanson43206 · 2024-09-15 19:33:19

Gents.... Spacesuit conversation has drifted over into the Compressed Air Energy Storage topic.

Both topics are important and I hope each will continuing developing.

However, if we ever attract a serious reader who might hope to learn something useful from this forum, it will help if we can keep the topics generally moving to the title objective.

(th)

tahanson43206 · 2024-09-15 19:36:28

For SpaceNut ... what were you trying to tell us when you brought up gasoline?

You might have been trying to remind us that gasoline is a more dense energy storage material.

The Compressed Air Energy Storage topic is never going to achieve ** anything ** like what gasoline provides.

On the other hand, as Calliban reminds us frequently, a simple mechanical system that is recharged by renewable energy sources might last for centuries.

(th)

tahanson43206 · 2024-09-15 19:38:48

Here is a copy of the opening post for this topic:

I think it is possible for the members of this group to work out the details of what a system might look like. It will never win any awards for energy density, but it may win awards for outlasting the competition.

This topic is offered because several members have included CAES references in posts in other topics.

The most recent post by Calliban, showing the outlines of a practical system for Mars, inspires this topic.

This topic is intended to provide a place for a vision of a clean CAES system, whatever that might mean in the context of a particular situation.

This line is provided for a link that was posted by Void, to a 2008 study of CAES on Earth
https://www.livescience.com/4955-compre … lectricity

This line is provided to link to a post by Calliban showing a practical application of CAES on Mars.
http://newmars.com/forums/viewtopic.php … 98#p226498

(th)

tahanson43206 · 2024-09-15 19:53:05

Rather than start a new topic, I would like to try adding this wrinkle to the flow...

There are oil wells that are no longer producing oil. My understanding is that most of these wells are capped.

I've seen reports that geothermal researchers and entrepreneurs have investigated trying to use these out-of-service oil wells for geothermal experiments.

Calliban has warned us that the nature of the material around these wells is such that heat flows poorly. If entrepreneurs pull thermal energy out of a region near the bottom of one of these wells, it will take the Earth many years to recover the temperature present at the beginning of the removal.

I'd like to offer an alternative suggestion, based upon a hint provided by a paper that Void found. That paper reported that researchers are trying to improve the efficiency of CAES systems by saving the thermal energy accumulated by compressing air.

My idea for the unused oil wells is to pump air into them to a pressure below whatever their safety limits might be.

The bottom of each such well must be secured so that air does not push out into the crust of the Earth nearby.

Given the volume available in a deep well with a reasonable diameter, and assuming the pressure can reach multiple bars, I am hoping it will turn out that a decent quantity of energy can be stored.

If there is a member of the forum with the needed skills, and if this question is of interest, I would like to know what quantity of energy might be stored.

A consideration is that the Earth should act as an insulator, so that thermal energy invested in the air that is compressed is not lost but instead is preserved, so that when the air is released to make power, the needed thermal energy will be available.

If the well is deep enough, the natural warmth of the crust of the Earth may contribute modestly to the store of thermal energy in the pipe.

During early days/weeks/months of operation, some thermal energy will flow into the crust surrounding the pipe, but due to the poor thermal conductivity of the material, I am hoping that losses due to this flow will decrease.

(th)

kbd512 · 2024-09-16 11:14:20

If we're talking about what is most practical to use on Mars, that's going to be a de-rated internal combustion engine burning compressed natural gas and O2. Even with 350bar steel storage tanks, we're talking about considerably more range for far less weight, which means more weight can be devoted to vehicle and crew protection measures. We only need 60hp to make a Mars-based Hummer perform like an Earth-based Hummer, or we can massively increase the vehicle's durability by adding more steel weight. These are fun thought exercises, but off-road vehicles are very power-hungry when run at significant speed.

For a light low-speed vehicle operating around a base that already makes and stores significant quantities of LCO2, it makes sense to run a vehicle off the product you're already using for construction purposes, because then you don't need your ACME Organic Chemistry Starter Set to make and store LNG and LOX. Water will be in chronic short supply, so making fuel might not be a good use of limited energy resources, but CO2 is everywhere at all times.

As for using abandoned oil wells to store compressed air, that's a very different application. The compressed air is an energy store, and potentially a very cheap one. Cheap is highly desirable when you need to supply massive amounts of energy. Compressed air can be converted to mechanical power output, air conditioning, or electricity, or all three at the same time.

As of late, no green energy solution except solar thermal come with their own onsite massive energy store. Most of those have 10 to 16 hours of storage, which is the minimum amount required to make it to the next morning. All the batteries have output measured in minutes to hours. Abandoned oil wells can be and frequently are huge concrete encased pressure vessels. So long as they're filled with something, they're pretty stable. I cannot evaluate long term durability under significant pressure cycling. I would say pumping heat from a solar thermal plant into an abandoned oil well filled with water or molten salt, with thermal energy extracted as needed using compressed air or sCO2, is probably a good way to ensure the long-term stability of the well bore because it's not subjected to repeated pressure cycling.

Calliban · 2024-10-01 16:03:21

The science behind concrete has advanced considerably over the past 30 years. There are ultra high performance concretes that have compressive strength over 150MPa (1500 bar). Some UHP concretes have strength as high as 250MPa.
https://www.sciencedirect.com/topics/en … e-concrete

These concretes are produced using ordinary portland cement, but replace ordinary sand and aggregate with a mixture of ultra-fine sand and silica fume. Water content is kept as low as possible - about 7% by volume. The resulting concretes are almost as strong in compression as mild steel. The thing I find most impressive is that flexural strength can be as high as 50MPa. Flexural strength is not something usually associated with concrete.

How is this relevant to compressed air energy storage? For CAES to be a practical way of powering vehicles, we need to operate at high pressures, the higher the better. Otherwise, the compressed air tank is too bulky to be practical for any decent range. Kbd512 has written extensively about the use of 300 bar pressure tanks made from carbon nanotube reinforced polymers. At that pressure, compressed air at room temperature has about 40% the density of water.

To generate compressed air efficiently at those pressures, we need to use multistage axial compressors, with interstage cooling. As many as 60 stages are needed to achieve these pressures with intercooling between each stage. These work better as large units, in the 10s to 100s MW range, mainly because as air gets denser, volumetric heat capacity increases and it becomes more difficult to provide compact intercooling. This makes it desirable to be able to transport compressed air by pipe and store it at filling locations to provide a buffer between usage and generation. If air is compressed using intermittent energy, storage becomes even more important.

Air storage at scale at 300 bar pressure is impractical using steel vessels. This is because it becomes increasingly difficult to fabricate pressure vessels as wall thickness grows. The development of UHP concretes allows pre-stressed concrete storage vessels to be developed. These use a relatively thin steel internal liner, surrounded by a concrete shell. The shell is compressed externally by steel cables and tendons. This allows a large number of relatively thin steel members to provide the tensile strength needed for the pressure vessel, by transfering compressive stress into the concrete, which balances the expansive force the contained pressure.

UHP concrete is the key enabling technology for storage of large volumes of air at high pressure. Such a storage vessel would be expensive to build. However, the working lifetime of such a vessel would be practically unlimited. The steel cables and tendons will have a fatigue life and they will require replacement after a defined number of pressure cycles. But the number of cycles could be as many as 1 million, implying an effective lifetime measured in centuries. Steel stressing cables are in any event replaceable components and the steel is readily recyclable. So the tank, once constructed, will have an unlimited effective lifetime. Like the axial compressors generating the HP air, this sort of infrastructure is a gift to future generations. With appropriate care and maintenance, these things don't wear out because the parts that do experience ageing (bearings in the compressor, stressing cables in the pressure vessel) are long-lived and replacable.

Last edited by Calliban (2024-10-01 16:15:07)

kbd512 · 2024-10-01 20:05:30

Little bits of CNT fiber are also mixed into concrete that was subjected to crushing railway loads at switching yards, in order to lock the bits of aggregate together, with the end result that concrete which previously wouldn't last for six months before crumbling under load would then last for multiple years before replacement was required.

In high strength CFRP pressure vessels, bits of CNT fiber are mixed into the resin matrix, in order to lock the plies of tape or fabric together. This prevents interlaminar shear stress from delaminating the plies of fabric.

In both cases, the CNT additive is highly effective at preventing the sort of "de-bonding" that can occur under extreme stress.

In large caliber tank and artillery barrels, the "autofrettage" technique is frequently employed to apply a pre-loading of compressive stress into the barrel steel, above the expected working pressure of the barrel during firing, so that the high rate stress induced by firing does not lead to plastic deformation or yielding during firing. A barrel undergoing this pre-stressing procedure is first filled with hydraulic fluid and then pressurized above the anticipated working pressure. After the hydraulic pressure is removed, the barrel "springs back" or "shrinks" in a predictable and uniform way. Ever after, that residual "compressive force" imparted into the steel precludes the high rate stress induced by firing from causing the barrel steel to yield. This mechanical property of the manufacturing process is retained so long as the steel's temperature does not become so great from rapid firing that the steel starts to soften or anneal.

I presume this autofrettage procedure could also be applied to a steel liner of a very large compressed air storage tank.

New Mars Forums

Announcement

#1 2024-09-13 07:46:42

CAES Compressed Air Energy Storage

#2 2024-09-13 07:47:20

Re: CAES Compressed Air Energy Storage

#3 2024-09-13 08:58:58

Re: CAES Compressed Air Energy Storage

#4 2024-09-13 09:20:48

Re: CAES Compressed Air Energy Storage

#5 2024-09-14 04:36:14

Re: CAES Compressed Air Energy Storage

#6 2024-09-14 07:31:06

Re: CAES Compressed Air Energy Storage

#7 2024-09-14 07:34:12

Re: CAES Compressed Air Energy Storage

#8 2024-09-15 02:58:19

Re: CAES Compressed Air Energy Storage

#9 2024-09-15 15:18:20

Re: CAES Compressed Air Energy Storage

#10 2024-09-15 16:12:50

Re: CAES Compressed Air Energy Storage

#11 2024-09-15 16:47:32

Re: CAES Compressed Air Energy Storage

#12 2024-09-15 17:25:46

Re: CAES Compressed Air Energy Storage

#13 2024-09-15 19:33:19

Re: CAES Compressed Air Energy Storage

#14 2024-09-15 19:36:28

Re: CAES Compressed Air Energy Storage

#15 2024-09-15 19:38:48

Re: CAES Compressed Air Energy Storage

#16 2024-09-15 19:53:05

Re: CAES Compressed Air Energy Storage

#17 2024-09-16 11:14:20

Re: CAES Compressed Air Energy Storage

#18 2024-10-01 16:03:21

Re: CAES Compressed Air Energy Storage

#19 2024-10-01 20:05:30

Re: CAES Compressed Air Energy Storage

Board footer