Thermal Energy Storage

SpaceNut · 2024-05-26 08:36:04

Here is another brick Energy-smart bricks keep waste out of landfill

AA1nwKth.img?w=768&h=461&m=6

make bricks with a minimum of 15% waste glass and 20% combusted solid waste (ash), as substitutes for clay.

More information: Yuecheng Xin et al, Utilizing rejected contaminants from the paper recycling process in fired clay brick production, Construction and Building Materials (2023).
https://dx.doi.org/10.1016/j.conbuildmat.2023.134031
Yuecheng Xin et al, Energy efficiency of waste reformed fired clay bricks-from manufacturing to post application, Energy (2023).
https://dx.doi.org/10.1016/j.energy.2023.128755
Yuecheng Xin et al, A Viable Solution for Industrial Waste Ash: Recycling in Fired Clay Bricks, Journal of Materials in Civil Engineering (2023).
https://dx.doi.org/10.1061/JMCEE7.MTENG-15165
Yuecheng Xin et al, Transformation of waste-contaminated glass dust in sustainable fired clay bricks, Case Studies in Construction Materials (2022).
https://dx.doi.org/10.1016/j.cscm.2022.e01717

Terraformer · 2024-07-24 15:27:45

From 2013 -- Cost analysis of district heating

Their estimated costs for installation were around €2000 per house in prebuilt areas. It shouldn't be an especially expensive infrastructure to construct -- £2-400/m? -- because it's "just" trenching and piping, no messing around with high pressure gas. If it cost £2500 per house to put the pipes in, about £75 billion for all the homes in the country. Several years of gas bills, not a particularly large amount relative to other plans for a clean energy transition, and would be largely privately funded. And of course, costs will depend on the type of housing -- terraced houses with alleyways to run the pipes without disruption could be a lot cheaper to supply, whilst being the biggest beneficiaries due to limited space for more individual systems.

EDIT: I didn't realise how small the domestic distribution system would need to be. A litre of water cooled through 10c (say, 35 to 25 Celsius) would give up 40kJ of heat. A house might only need to tap 0.1L/s then, so a street of forty houses needs to provide 4L/s at peak. At 0.1m/s flow, that's a pipe ~25cm wide. We can easily fit that in alleys or under pavements.

Last edited by Terraformer (2024-07-25 02:48:43)

Calliban · 2024-07-25 06:28:52

Interesting. I think there are a number of different ways a district heating system can work. There are hot systems that distribute water at close to boiling. Warm systems that distribute at 30-60°C. Cold systems distribute heat at <30°C. The latter only work in combination with heat pumps. Cold systems have the advantage of not needing insulated pipework. The dirt and paving above the pipe will provide what little insulation is needed. In addition, there are hybrid systems. In this case, a cold water main would run under a main street, supplying large heat pumps that provide hot water to branching streets.

Each town has its own local resources and limitations and the design of each system will be specific to these. Some variation of district heating will be necessary in most parts of Europe, UK especially. Without gas, the only heating choices for urban homes are solid fuels like biomass, heat pump or resistance heating. The first is only available in limited amounts, is expensive and is restricted by clean air regulations. Ground source heat pumps require either a large garden or deep boreholes, which implies high capital cost. Air source has poor COP. Resistance heaters are cheap to buy but costly to operate. They will have niche applications but most people could not afford to heat this way.

Taking the UK as a case study, most UK towns are densely populated. The majority of houses are either terraced or semi-detached. Gardens are typically small. If district heating can work anywhere it will work here. I suggest we resurect our previous case study (Carnforth) and produce a concept design that accounts for local resource and limitations.

Last edited by Calliban (2024-07-25 06:49:41)

Terraformer · 2024-07-25 06:43:43

Re. boreholes, the cost per borehole goes down the more you drill, but the figures I've seen are for systems with only three to five. I can't find anything solid for how much it would cost to drill one hundred in under say a school playing field, as would be used in a district heating system.

One advantage of having a centralised heatpump I suppose is that upgrading the electricity supply to it to benefit from strong wind generation might be easier than upgrading it for multiple neighbourhoods and homes.

Terraformer · 2024-07-25 07:41:03

Taking the UK as a case study, most UK towns are densely populated. The majority of houses are either terraced or semi-detached. Gardens are typically small. If district heating can work anywhere it will work here. I suggest we resurect our previous case study (Carnforth) and produce a concept design that accounts for local resource and limitations.

I'd suggest the locations to look for are (1) large heat users that are (2) located next to open spaces for ease of borehole drilling and which (3) can be connected to domestic customers relatively easily (no long stretches that involve shutting down roads to install pipes).

In the case of Carnforth, I can see 2/3 -- the triangle I've mentioned before (primary school field, hotel and civic hall and school and church located around the edge, terraced houses also along it); the high school (large playing field, school and swimming pool adjacent); and possibly the area next to the train station (car park for boreholes, station hotel as anchor customer, terraced homes with alleys for running piping). Aside from that, there are various school fields and parks and car parks throughout the Victorian centre of town, an area that benefits from alley access (the cold water supply presently runs under these also).

If there's a mass buildout, we could manufacture pre insulated pipes? I know a cold system doesn't necessarily require much, but I'd like to futureproof it so we can do things like seasonal heat storage and supply heat at 25c instead of 10c...

EDIT: One problem that occured to me in cases where there are no convenient alleys -- gas pipes are routed under streets. Any attempt to run pipes under the pavements would have to deal with the connections to the houses every 5-10m. Obviously not a problem if the entire street switches over at once, but that is likely to take a level of coercion that will be difficult to achieve. Perhaps we could compulsory purchase easements right down the middle of the block and make an alley...

Last edited by Terraformer (2024-07-25 15:00:29)

Calliban · 2024-07-26 13:18:56

I have ordered an ordance survey map covering the Kendal area and north Lancashire. When it arrives it will provide a scale street map of Carnforth. I will attempt to scan that section of map and draw proposed pipe routes on printouts.

Additional: This website suggests that real heat pumps achieve about half of the Carnot efficiency. This seems to be a common metric for small heat engines.
https://learnmetrics.com/coefficient-of-performance/

For practical household heat pumps, it suggests a COP greater than 3 is highly efficient. I beg to differ. With a COP of 3, the case for a heat pump is marginal in most places. In the UK, domestic electricity typically costs about £0.2/kWh base rate. A COP of 3 would barely break even with gas, for a device that has higher capital cost. But a few things come to mind.

1. Heat pumps like other heat engines achieve efficiency gains as they scale up. This means that a heat pump supplying an entire street will have better COP than single house sized unit of just a few kWth. This is because larger systems have lower frictional and pumping losses.

2. The upper limit of COP (4.5) stated in the article only applies to an air source heat pump, drawing air at 0°C and producing hot water at 35°C. These units are relatively inefficient, because heat load is highest when outside temperature is lowest. Extracting heat from air also involves greater pumping losses than a water source heat pump, because large flowrates of air must be pushed through heat exchangers to transfer sufficient heat. An airsource heat exchanger will typically suffer a higher temperature drop between the air and heat exchanger tubes, as gas phase heat transfer coefficients are substantially lower than liquid. For all these reasons, the COP of ground source heat pumps is usually substantially greater than COP of air sourced heat pumps.

3. A heat pump installed into a district heating system can be supplied with warm water as its cold source. The required temperature rise is substantially lower than for an air sourced heat pump. A heat pump supplied with warm water at 30°C and suppyling hot water at 40°C, would have an ideal COP of 31.32. Real COP should be higher than 15 for a 100kWth machine capable of supplying up to 40 houses.

This suggests that heat pumps could yet have a valuable role in district heating systems. Warm water at 30°C can be generated using solar thermal panels. It is produced in GW quantities by nuclear reactors. A single 1000MW reactor, could produce all of the heat needed by a city like Manchester, if a distribution system were inmplace to bring the heat to customers. The heat source is effectively free, as the heat is a waste product. If we assume a temperature drop of 5°C as a result of heat pumping, the required water flowrate is 96m/s. This could be piped into urban areas using a warm water main build from concrete pipes and covered in dirt.

Last edited by Calliban (2024-07-26 14:55:23)

Terraformer · 2024-07-26 14:49:40

Hmm I could do this in QGIS... going to be getting a lot of experience with that over the next few months of my dissertation...

Back alleys form an almost complete loop around the central triangle of A6-Haws Hill-Market Street. I expect it would be the second easiest location to build a heat network in, after the A6-North Road-Kellet Road one I've mentioned before.

There should be maps of the gas network available; you have to sign up, but the maps are free because they don't want people rupturing gas lines whilst repaving driveways (gas is probably the craziest infrastructure ever built -- at least high voltage power lines carry versatile electricity and are unlikely to cause explosions if damaged...).

As an alternative to district heating for houses with front gardens, perhaps the costs of an individual borehole could be brought down significantly by doing the entire street in one go?

EDIT: the street map is already available online? https://explore.osmaps.com/?lat=54.1272 … rd&type=2d Scanning and printing seems a little overcomplicated.

Last edited by Terraformer (2024-07-26 14:52:30)

kbd512 · 2024-07-27 15:55:04

Using ocean-based trompes to compress air is a near-isothermal process. A hydraulic piston could be added to significantly decrease the depth required for the trompe. From watching YouTube demonstrations of various homebuilt units, some of which were intended to provide hydraulic vs pneumatic power for farming / irrigation pumps, there seems to be a rough "factor of 10" improvement associated with readily achievable trompe depth reduction. 147psi/10bar air would be supplied by shallow water trompes, to reduce the total cost of the system, and we'll call this "LPA" for "Low Pressure Air". LPA, would then be further compressed to 1,470psi / 100bar, which we'll call "HPA" for "High Pressure Air", using mechanical wind turbines. The heat from HPA compression would be removed using sea water, to supply hot desalinated water, forming the basis of the thermal energy storage subsystem required to run a natural energy system. For commuter vehicles, we need "VHPA" / "Very High Pressure Air", at 12,495psi. Motor vehicles require 12,495psi / 850bar for volume-efficient storage of their energy supply. If CNT-reinforced CFRP storage tank tech allows, 1,000bar would be better still. However, existing 850bar Type IV H2 CFRP tanks can successfully complete 15,000 pressure cycles at pressurization / depressurization rates far in excess of what they'd see in actual use. Dry air should be less damaging to these composite tanks than H2, but only testing can confirm that VHPA doesn't chemically attack the liner.

All-mechanical wind turbines would provide desalinated hot water for both human consumption and thermal energy storage, during the process used to convert HPA to VHPA, in order to add energy back not to VHPA, but HPA fed to homes and businesses to produce electricity. Buildings would be supplied with HPA, for purposes of onsite electrical energy generation using small Tesla turbines that power lights and personal electronics. Central air conditioning units and furnaces would also be supplied with HPA. Vortex tubes would supply hot or cold air, and pneumatic power would drive the circulating fans.

Most of the Copper and Aluminum can be replaced with much cheaper coated steels. The very short wiring runs would enable the use of Iron wiring. Site wiring would be heavier, but there'd be less of it, because you're running an onsite air-driven electric generator. A lot of the electrical equipment installed in every building then becomes superfluous, especially for homes or apartments, because your electricity isn't coming from a high-voltage / high-amperage centralized source capable of destroying all the electrical and electronic devices in your home without numerous protections at every step along the way. If the supply of electricity dips by 10%, that's catastrophic to an electric grid. If the pressure of the air fed into an onsite air driven electric generator dips by 10%, the effect may not even be noticeable.

Those stainless steel vortex tubes I provided a link to create 260C air on one side of the tube, so you don't need electricity to run a convection oven. With a little creativity, we can also figure out how to make a cooktop that uses vortex tubes to boil water. We certainly don't need electricity to run a dishwasher or central heating and air unit. Using HPA and hot water is an 85% solution to the numerous intractable issues associated with providing reliable electrical power, which seems to go beyond the capabilities of major corporations and governments to provide with an acceptable degree of reliability (not losing all electrical power for a week or two at a time).

The trompes and vortex tubes allow us, to a degree, to side-step the issue of bulk energy storage systems, since gravity is "turned on" at all times. The mechanical wind turbine output, which is highly variable, is immediately converted into stored VHPA for commuter vehicles. What was previously too erratic to predict with any degree of accuracy is now "completely knowable", based upon how much VHPA each wind turbine or field of wind turbines produces each week of the year, and that will inform decision making about how many of them to build. How many cars do we need to supply compressed air to, how much VHPA do the vehicles consume per day, how much VHPA are our wind turbines producing, and now we no longer have to guess, no longer have to dump energy into the ground, and no longer have to "over-build" something chock-full of Copper, Aluminum, and rare Earth elements. We've reduced the most erratic natural energy source to something that is totally reliable, insofar as its output can now be measured in cubic meters of VHPA and hot water per week / per month / per year, both of which are "ready to consume" energy products that only require pipelines to supply gas stations or buildings. Very little of the stored energy is "lost" during transmission. It's a fluid inside a pipe, one of which requires no pumping to reach its point of use. If the wind blows too hard for the mechanical wind turbines to tolerate, then we simply increase the force on the water brake, reducing air compression efficiency but increasing the desalinated hot water supply. Production doesn't stop, unless the wind quits blowing. The air and water energy products being consumed are returned right back to where we got them from after we're done using them.

Whatever salt we collect during the desalination process can either be used for direct thermal energy storage in abandoned oil wells, or we can use Sodium, Carbon from sea water CO2, and Iron to make more Sodium-ion batteries as a substitute for the environmental catastrophe associated with Lithium-ion batteries. Energy production remains the focus of the effort, because it greatly reduces the requirement for storage. VHPA is stored only very briefly and in relatively small storage containers, similar to gasoline, except that it's consumed even faster because it contains less energy. Both the starting and final products from air powered motorized vehicles are the exact same thing. The "battery" lasts for at least a human lifetime worth of driving. Most of the machine can either be produced from burnable composites made from natural fibers such as flax, or it can come from steel. Either way, breaking down the machine after it becomes uneconomically repairable is much easier to do.

If all 33.58M passenger cars in the UK were powered by compressed air stored in a 250L 1,000bar CFRP storage tanks, that's 8.395M cubic meters of compressed air storage tank capacity. We do need to store some VHPA, but no more than whatever is required to refill all of the vehicles once per day. Assuming all vehicles have a range of about 100 miles and are refilled every other day, the total compressed air energy production system requires 3GW to 6GW of input power to fill up all passenger cars with VHPA on an every other day basis, some of which will be provided by gravity to create the initial supply of 10bar LPA, with the HPA and VHPA provided by mechanical wind turbines to obtain desalinated water in conjunction with HPA and VHPA. Providing enough HPA requires a much greater energy input, though, since HPA is powering most homes and businesses.

Calliban · 2024-07-27 17:16:08

There is a large field to the south of Carnforth.
https://www.google.co.uk/maps/@54.12197 … 697753,17z

By my estimate, it is about 15 hectares, or 150,000m2. I would propose filling this area with solar thermal collectors. If we assume 500kWh/m2 of unobscured sunlight per m2 per year and a panel density of 50%, the total thermal energy captured would be 37,500,000kWh. That is enough to provide 3000 homes with 12,500kWh of heat each year, if a district heat network is in place to deliver it.

Heat storage could be achieved by pumping hot water down boreholes directly under the panels. Let's assume heat is injected into a rock layer 100m thick, with an additional 100m of rock and soil providing insulation. During heat withdrawal, temperature drops by 3°C. The amount of heat stored would be:

Q = m x Cp x dT = (100m x 150,000 x 2500) x 800 x 3 = 90TJ (25 million kWh)

This is enough stored heat to provide 2000 homes with 12,500kWh each.

Heat delivery would take place by running a warm water main along the A6 until kellet road. The main would run along Kellet road until it reaches highfield road, where it turns right again. The main continues turning right again down windermere road. Upon reaching the end of windermere road, the main has completed a circuit of the town.

Last edited by Calliban (2024-07-27 17:23:07)

Terraformer · 2024-07-27 17:38:43

Well, we're not allowed to have houses there in case they want to mine gravel for 22nd century motorway construction, might as well make use of it for something that benefits the town...

What I have in mind though are smaller such schemes. Admittedly greenfield solar collectors will probably be cheaper than over car parks and roofs, even flat ones. But the space for boreholes is certainly not hard to find. I suppose the solar thermal collectors would be angled for summer?

The other issue is that running the mains along the road means digging up the roaad. Unfortunately there's a gas main under the townpath until I think the canal turn, but if there's room it would be far less disruptive. But past the canal turn (next to where the town gas was made, hence the gas lines) I think it is clear and would not be a bad place to run a hot water mains if so. Certainly they dont trim the trees the way they're supposed to near gas lines in that section.

Last edited by Terraformer (2024-07-27 17:43:46)

Terraformer · 2024-07-28 14:32:10

Hmm at some point it might end up being cheaper and easier to just keep drilling. Go a couple of kilometres down and tap 30-40c temperatures. But if solar thermal is used, I don't think 100m is necessary as an insulation layer. IIRC when I looked at this last 10m would suffice to achieve quite small heat losses.

For a network serving the central part of the town where almost all the terraced housing it, it could wrap around running along Grosvenor then down Haws Hill, back up Hawk Street, down to the canal and returning via the marina. Then presumable supply pipes would run across town between these, probably through the back alleys. Another advantage of the alleys being that the switchover can be more gradual -- if people want to keep their ridiculous gas line they can, no need to switch everyone over at once to minimise disruption. Political palatability is quite important as well. Though I'm not averse to compulsory purchasing easements through people's back gardens to run the service lines...

There are maybe 600 to 800 homes in that central area (I think closer to 600). Almost all terraced, so heat demand should be on the low end for houses. Unfortunately subject to some historic conservation order. Which may actually make a heat network one of the few acceptable ways to decarbonise heating...

Calliban · 2024-07-28 15:27:28

You are correct concerning required drilling depth. Fourier's Law:

Q=kA x dT/dX

If we assume:
1. A 10m insulating layer with a thermal conductivity of 2W/m.K, for damp soil and gravel;
2. A year round average ambient temperature of 10°C;
3. A heat storage temperature of 30°C immiediately after summer, dropping to 20°C by late spring;
...Thermal losses average out to 26kWh/m2/year. I estimate thermal losses no more than a few percent of total heat inventory per year.

One way of gathering heat that is relatively light on infrastructure, would be to lay pipes a few inches under a tarmac or gravel surface. During summer days, soil temperature can easily get to 20°C. Use solar PV to power a heat pump that uses this heat as a cold source and produces warm water at 30°C. The warm water is then used to charge the boreholes. At those temperatures, ideal COP is ~30, realistic COP is about half of this. The gravel or tarmac area could double as a car park.

Last edited by Calliban (2024-07-28 15:38:32)

Terraformer · 2024-07-28 16:37:11

What sort of heat transfer rate are we looking at, for a given temperature difference? Obviously its going to take time for 30c water to heat a 25c borehole...

One thing we could do with geothermal heat is to circulate it during the summer to heat the entire borehole rather than just the bottom. Then draw the heat out during the winter. Improved capacity factor.

As for car park heat collection, there are four sizeable car parks in central Carnforth, the three supermarkets and the railway station. Looks like they could be enough for the centre?

tahanson43206 · 2024-07-29 00:48:06

For Terraformer and Calliban...

Thank you for continuing to refine and add to your discussion of large scale Thermal Energy Storage.

Because of the large investment required, I'm wondering if a large scale industrial project might be worth pitching for a first venture. There may be something large scale in planning in the UK, and the managers might be amenable to suggestions to increase their long term profitability by managing thermal energy more effectively than is normal(default).

In the area where I live, a huge Intel factory is under construction. I'll bet the project managers do not have a clue how your ideas might benefit them.

(th)

SpaceNut · 2024-07-29 18:39:42

Ground level working fluids will mean an antifreeze as to not freeze and that means you will need to keep any leaks out of the ground water unless using food grade. I am thinking that Pex tubing will be a possible pipe material to use under the asphalt surfaces.

kbd512 · 2024-07-29 23:42:21

SpaceNut,

You don't have to drill very deep before arriving at a constant temperature which remains above the freezing point of water. After enough heat is injected, the great thermal mass involved prevents freezing.

The oil and gas industry super-saturates water-based drilling fluids with various salts. Salt is pretty effective at preventing freezing, especially if the fluid is constantly moving. You need to use concrete, plastic, or coated steels to inhibit corrosion, but it works quite well. Drilling occurs in bitterly cold places around the world, especially during the winter, by adding salt.

Silicon CVD coating works very well for inhibiting corrosion of steel. There are also various plasma spray ceramic coatings that work. Alternatively, given the very low "high" temperatures involved (near the boiling point of water), plastics would also work well for carrying the hot water. Plastic coated steel or concrete pipes are increasingly common. Most of the drainage / sewage pipes around here get coated with a plastic, which both acts as an impermeable barrier, is slick so water flows more freely, and even "holds the concrete together" as the ground moves around due to significant fluctuations in the amount of water in the ground / top soil.

Plastic and concrete are harder to recycle than coated steel, but they don't have the corrosion issues that metals do, and most of the very large pipes are coated concrete, rather than steel or plastic. If the pipe or bore hole is stable, then concrete is what you want. All oil and gas bore holes are "cased" using cement, rather than metal or plastic, because that is what will last the longest. The only piping that really needs to be steel or CFRP-reinforced plastic are for compressed air, for which there aren't any good substitutes.

The implication is that concrete-lined bore holes are used to store water heated by compressing air. Thicker but still relatively small steel pipes with Silicon-based CVD coatings pump HPA / VHPA, and HPA or VHPA air tanks really need to be Type IV plastic-lined CFRP. A polymer liner, especially a fluoropolymer, prevents the resin in the composite from absorbing any residual water present in the compressed air, preserving the structural integrity of the tank as it experiences many thousands of pressure cycles over its service life. At 1,000bar, the energy density is on-par with a Lithium-ion battery, but without the recycling headaches.

HPA and VHPA should be thought of as useful byproducts derived from mechanical wind turbines or solar thermal tubes "making hot water" or "making desalinated water". Tahanson43206 once asked me for a denotative formula describing the energy available in compressed air expanded in a near-isothermal process, but I will put a link and formula in Terraformer's compressed air topic, because I found it again.

Getting back on topic, human civilization consumes more fresh water and hot water than any other single material. However, I think of hot water as being an "in conjunction with" energy storage subsystem that involves compressed air. We need both. We need sCO2 and salt for places that have lots of sunshine, but no water, meaning deserts. Desert-based natural energy systems are closed-loop, by necessity, whereas ocean-based natural energy systems are open-loop, because that's optimal.

Calliban · 2024-07-30 05:51:16

Terraformer wrote:

What sort of heat transfer rate are we looking at, for a given temperature difference? Obviously its going to take time for 30c water to heat a 25c borehole...
One thing we could do with geothermal heat is to circulate it during the summer to heat the entire borehole rather than just the bottom. Then draw the heat out during the winter. Improved capacity factor.
As for car park heat collection, there are four sizeable car parks in central Carnforth, the three supermarkets and the railway station. Looks like they could be enough for the centre?

To model heat transfer into the surrounding rock and soil, a spreadsheet can be used. The material around the wells is divided into concentric rings and temperature rise due to conduction is calculated for each ring across each timestep. This is useful for determining how far apart the boreholes should be drilled, which is an important cost driver.

Terraformer · 2024-07-30 12:12:27

Hmm. One advantage of being able to connect homes without forcing them to disconnect from gas is that they can save the expense of a heat pump (for now) and can still gain benefits from preheating water. Could also incentivise lower temparature heating systems -- ceiling radiators could use 40c water directly, especially if the home is insulated. I think the system needs to be able to accept gradual improvements both on the user end and on the production end That would also allow it to perhaps be built for what homes with reasonable insulation would require, rather than current demand -- people who don't insulate will just have to make up the loss with their gas boilers I guess.

SpaceNut · 2024-07-30 19:48:10

Yes heat pumps make heat or cold mostly with air to air systems at the expense of the electrical energy. The few that do a stable table really are not changing much other than efficiency of temperature for the compression and cooling cycles of the heat pump.

What I was talking about was storing the raw heat from the hot surface for later use.

tahanson43206 · 2024-09-16 14:56:15

In his personal topic, kbd512 seems to have invented an energy storage system that might be cost effective in some circumstances.

The initial proposal to which this post is a reply offered a vision of pumping air into an abandoned oil well, to store energy in the form of CAES.

In the post below, kbd512 explains possible drawbacks with the original idea, and offers an alternative that I am hoping our members will find interesting, and that this topic will attract helpful ideas to turn the idea into a thriving business.

kbd512 wrote:

tahanson43206,
I'm saying that you load the well with an incompressible fluid, such as hot water or molten salt, and you stick your radiator (a metal pipe) in that fluid, and you transfer heat in and out of the fluid using a gas (CO2). Heat is pumped into the well using CO2. Heat is extracted from the well using CO2. Topside, you have a heat exchanger that uses water or air. The gas flows through the radiator in the well, where it picks up heat and expands, so it comes rocketing back out of the well and you run the hot expanding gas through a power turbine. In addition to the power turbine which extracts mechanical work from the hot expanding gas, you also have a heat exchanger to cool the gas before it's re-injected into the well. This is your complete thermal power transfer loop.
The first loop pumps heat into the well using heat collected from solar thermal. We don't have to worry about "loosing" heat, because we're always pumping more in, and the insulation provided by the wellbore liner is pretty good.
The second loop routes hot CO2 into the radiator piping (a literal steel pipe that transfers heat into the gas using conduction) in the well where it gets heat from the water or salt sitting in the wellbore. The exit pipe leaving the well is fed into a sCO2 gas turbine. Immediately after the sCO2 turbine, you have a radiator to cool the gas before it then passes back into the thermal storage well.
Only the small diameter metal piping has to contain and deal with pressure changes. The well itself is only containing a hot fluid (salt or water), that doesn't mess with the static pressure at any given point in the well, so the ambient conditions in the well do not involve extreme expansions and contractions from huge pressure changes, as would be the case if we pressurized and depressurized the well. Hydrostatic pressure changes as depth increases. Maybe you could do 350bar at the bottom of the well bore, Earth is pressing inwards on the wellbore with 350bar of pressure at the deepest point in the well, but 350bar at the top of the wellbore may fracture the concrete casing / wellbore liner and then you start loosing gas into the rock formation. This concept is very important to prevent a catastrophic collapse or a surge of pressure forcing the contents of the wellbore out of the well. Adjusting hydrostatic pressure was a constant concern while drilling. The well has to be filled with something at all times, or the Earth fills it for you.

(th)

tahanson43206 · 2024-09-16 14:57:48

This post is reserved for an index to posts that may be contributed by NewMars members over time from Post #245

(th)

tahanson43206 · 2024-09-16 15:10:40

As a follow-up to the idea shown in Post #245 of this topic....

There may be a sweet spot that would allow the maximum return for investment.

Given availability of an abandoned oil well, and taking the ideas of kbd512 into account...

1) Cost of clear license to the abandoned well, or clear title
2) Cost of engineering studies to find the optimum combination of materials and methods for this particular well
3) Cost of permitting in the locality where the well resides (Concerns are many but all must be addressed satisfactorily)
4) Cost of a pair of pipes to descend into the well for passage of working fluid (eg, CO2)
5) Cost of material chosen to hold the thermal energy (eg, water, sodium, other)
6) Cost of plug to be installed at the bottom of the well to prevent material from escaping into the crust of the Earth
7) Cost of entire above ground package to store and recover energy from the well
8) Cost of accounting services for the business
9) Cost of legal services on an "if needed" basis

If anyone can think of anything I've missed, please post a reminder.

For all...

There are numerous abandoned oil wells in the US and around the world. Many of these are located where solar power or wind are available. The idea of kbd512 might represent a competitive solution for storage of energy from intermittent sources.

An investigation of the potential business opportunity would include:

1) Confirmation that the idea itself is practical
2) Confirmation that the idea is competitive with other solutions that might be considered
3) Inventory of potential wells that might be suitable and available at a reasonable price
4) Inventory of wind and solar companies that might be interested in using this energy storage method

? other ?

(th)

kbd512 · 2024-09-16 18:16:05

I haven't invented anything. You wanted a thermal energy store that utilizes existing frack wells. I only told you how to do it without causing serious problems, based upon what little I know / remember about drilling from the bits and pieces of Mud School that I was taught by the engineer who taught Mud School for the oil company I used to work for. I worked with him to develop drilling software to estimate volumes / tonnages of materials consumed, so I learned a little bit about drilling, because I had to.

Highly pressurized gas is bad for long term longevity concrete wellbore liner longevity because the gas pressure will need to be far above what it should be at the surface, in order to keep the well from collapsing nearer to its maximum vertical depth. An incompressible fluid solves that hydrostatic pressure differential problem. A molten salt is very good at storing heat, but won't change much in volume very much as heat is added or taken away to sustain the output of a power plant and thermal input located on the surface.

You never want the well to collapse, or the contents of the well to come flying back out of the well. Hydrostatic pressure has to be adjusted appropriately, or that's exactly what will happen. The density of the drilling fluid is adjusted appropriately during drilling operations, and then an incompressible fluid is used to fill the well bore after drilling is complete. The incompressible is usually water, actually a very high salinity brine, or water and oil (because that's what is naturally present in the ground), or it could be a molten salt.

Remember that gusher at Spindletop? We would consider that a serious mistake today, not merely for environmental reasons, but for the safety of everyone on or near the drilling rig. We would adjust the specific gravity of our drilling fluid by adding "heavy dirt" (Barite) or increasing fluid system volume (adding water or oil and chemicals) to ensure something like that doesn't happen. Too much hydrostatic pressure is every bit as bad as too little.

Median frack well depth is about 8,200ft, based upon data from 44,000 wells around the US. The total length can be much much longer than that, but let's use the simple case of a vertical soda straw. When wells are drilled the top sections are larger in diameter than the bottom section. That said, let's imagine the well bore as a 0.5ft by 8,200ft, and then double the volume to account for the much larger volume of the top sections. In reality, it will have more volume that than, but let's keep it simple.

(0.5)^2 * (22/7) * 8,200 = 1,610ft^3 <- Our 6 inch diamter 8,200ft long "soda straw"; the basic "volume of a cylinder formula"
3,220ft^3

Salt is about 80lbs/ft^3, so 3,220ft^3 * 80lbs/ft^3 = 257,600lbs / 116,846kg of salt

Salt can store about 1.53kJ/(kg·°C)

Let's say our hot side is 300°C (heat injected from solar thermal) and our cold side is 200°C, so ΔT is 100°C.

116,846kg * 1,530J * 100°C = 17,877,438,000 Joules of thermal energy (not what we can get out, but what we have to work with)
3,600J = 1Wh
17,877,438,000J / 3,600J/Wh = 4,965,955Wh

1kg of salt heated to 300°C on the hot side, with 200°C as the cold side temperature, equates to an energy storage of 42.5Wh/kg of salt, with 35% of that being 14.875Wh/kg of salt.

If we can convert 35% of that into electrical power, then our actual usable energy storage is 1,738,084.25Wh / 1.738MWh per well.

If we used all 44,000 of the wells from the data collection, then we can store 76,476MWh, or about 76.5GWh worth of energy. This is roughly equal to capturing the entire daily output of 3X 1GWe nuclear reactors. If we refill the captured heat every day, then over the course of a year, it's 27,914GWh, or almost 28TWh, so it's about equal to 1 days worth of our total primary energy consumption. We would need to expand our energy storage by roughly 365X for it to become 1/3rd of our daily energy consumption. There are 1.7M frack wells in the US, and all of them are very young, because fracking only became a thing relatively recently. We would need 16.06 million frack wells of average size / volume to store enough thermal energy to account for 1/3rd of our daily energy consumption.

We used about 95 quads of energy in 2022.
1 "quad" or "quadrillion BTU" = 293.0711TWh, or 27,841.7545TWh/year, or 76.279TWh of primary energy per day
1TWh = 1,000GWh

25,000,000,000,000Wh of energy storage / 14.875Wh/kg = 1,680,672,268,908kg / 1,680,672,269t of salt

From Bureau of Land Management:

Total salt crust volume has been estimated at 147 million tons or 99 million cubic yards of salt! The Bonneville Salt Flats are comprised of approximately 90% common table salt.

From USGS:

According to the U.S. Geological Survey (USGS), Earth plays host to some 88 million tonnes of lithium. Of that number, only one-quarter is economically viable to mine (this is known as “reserves”). Luckily, Earth's total reserves of lithium will likely increase as technology improves.

25,000,000,000kWh of energy storage * 0.16kg per 1kWh = 4,000,000,000kg or 4,000,000t of Lithium

That's for 8 hours of power for the US alone. The world would need 20,000,000t. To store power for 24 hours, the world would need 60,000,000t. That's the entire supply of reserve power if we use photovoltaics and wind turbines and Lithium-ion batteries. To still have power during winter months, we need to store about 2,160 hours of power. That is clearly never going to happen in the near future.

If we do 400°C to 200°C, then we get more than twice as much energy back out, at least 25Wh/kg, but it's easy to see it's not nearly enough to provide for daily let alone seasonal electrical energy storage demand. We need a math-based energy transition plan, not "hope and change". If we had 250Wh/kg Lithium-ion and Sodium-ion batteries, there is not nearly enough energy storage to power the world we live in today.

This is how I know for a fact, beyond any shadow of a doubt, that whatever energy system we devise to replace what we use now, it absolutely will not use electro-chemical batteries. Therefore, it won't involve the use of photovoltaics and wind turbines because those require electro-chemical battery energy storage to deal with the massive fluctuations they produce, at a national or global grid scale. There's simply not enough metal.

Anyway... That is why we're going to use enormous quantities of compressed air and water, with some salt and Iron providing thermal energy storage, and electricity only where absolutely required. If we consumed all of our battery making metals and salt or converted our salt into battery making metals, we cannot remotely approach our seasonal energy storage requirements. We need more steel, more compressed air, more hot water, and more synthetic hydrocarbon fuels to serve as energy stores for energy-hungry vehicles that do all of the real work society requires to maintain our standard of living. We could invent 500Wh/kg batteries tomorrow. It still doesn't change the math presented here in a way that actually matters at a global scale. We need a better plan. Thermal energy storage is part of that plan.

Calliban · 2024-09-19 12:17:09

The marginal cost of energy storage will increase in proportion to capacity squared. This is because the more we have, the less intensively it is used. Imagine having a 1MWh battery that can store enough energy to power something for a whole year. How many MWh will that battery store in a whole year? Ans: 1MWh. The marginal cost of that battery per MWh will be huge. This is why things like batteries are only suitable for small scale energy storage. For long term energy storage to be affordable, it must be really cheap to begin with. Thermal energy storage is one of the few energy storage options that is cheap enough to store energy long term. That is because the storage media are things like rock and water, that are almost free. They are free not just in terms of money, but also energy. Digging a thousand tonnes of rock out of the ground and putting it in a container, will be orders of magnitude less energy intensive than making a thousand tonnes of batteries. But the two will store about the same amount of energy within practical temperature ranges. So TES is much cheaper per MWh.

Synthetic hydrocarbons and other chemical based fuels are expensive to make, due to thermodynamic inefficiencies that waste exergy. But they are cheap to store, because they are energy dense and will sit in a tank. So we might affordably include some sort of syn hydrocarbon as part of a larger system that uses these fuels to produce energy when other energy stores are depleted. But in so doing we must account for the cost of the whole system. That means the making, storage and generation equipment. A heat engine that generates power only a few percent of the time is going to have high marginal capital cost. Which is a similar problem to the battery that has to store a whole year of power. This is why peaking powerplants tend to things like open cycle gas turbines burning liquid fuels. The fuel cost per MWh is relatively high. But their capital and operating costs are low, because they are compact devices and require little in the way of operator oversight. So these machines produce cheaper peak power even if they are less fuel efficient and have high per unit fuel cost.

Last edited by Calliban (2024-09-19 12:38:32)

Calliban · 2024-09-19 13:08:39

Calcium nitrate has a bulk cost of about $1/kg, a melting point of 561°C and a heat of fusion of 24KJ/kg.
https://www.agrigem.co.uk/product/calcium-nitrate-25kg/
https://en.m.wikipedia.org/wiki/Calcium_nitrate
https://energy.sandia.gov/wp-content/ga … ordaro.pdf

A cubic metre of CaNO3 will weigh 2504kg, will cost about $2500 and will store a 101kWh of heat through latent heat of melting. The cost of capacity works out at $25/kWh. Could we make a battery that store energy that cheaply?

According to this reference, battery energy storage declined in cost to $776/kWh in 2020. That is still over 30x as expensive. And batteries wear out, salt does not. Building salt based energy storage systems capable of powering the whole US for 3 days will still cost at least $1trillion when the cost of generating plant is factored in. But the task is achievable in a way that it just isn't for batteries. A well maintained steam generating plant can last for 50 years. That means the marginal replacement costs of a salt-steam power storage system would be about $20bn per year. That is <0.1% of US GDP.

Last edited by Calliban (2024-09-19 13:32:22)

New Mars Forums

Announcement

#226 2024-05-26 08:36:04

Re: Thermal Energy Storage

#227 2024-07-24 15:27:45

Re: Thermal Energy Storage

#228 2024-07-25 06:28:52

Re: Thermal Energy Storage

#229 2024-07-25 06:43:43

Re: Thermal Energy Storage

#230 2024-07-25 07:41:03

Re: Thermal Energy Storage

#231 2024-07-26 13:18:56

Re: Thermal Energy Storage

#232 2024-07-26 14:49:40

Re: Thermal Energy Storage

#233 2024-07-27 15:55:04

Re: Thermal Energy Storage

#234 2024-07-27 17:16:08

Re: Thermal Energy Storage

#235 2024-07-27 17:38:43

Re: Thermal Energy Storage

#236 2024-07-28 14:32:10

Re: Thermal Energy Storage

#237 2024-07-28 15:27:28

Re: Thermal Energy Storage

#238 2024-07-28 16:37:11

Re: Thermal Energy Storage

#239 2024-07-29 00:48:06

Re: Thermal Energy Storage

#240 2024-07-29 18:39:42

Re: Thermal Energy Storage

#241 2024-07-29 23:42:21

Re: Thermal Energy Storage

#242 2024-07-30 05:51:16

Re: Thermal Energy Storage

#243 2024-07-30 12:12:27

Re: Thermal Energy Storage

#244 2024-07-30 19:48:10

Re: Thermal Energy Storage

#245 2024-09-16 14:56:15

Re: Thermal Energy Storage

#246 2024-09-16 14:57:48

Re: Thermal Energy Storage

#247 2024-09-16 15:10:40

Re: Thermal Energy Storage

#248 2024-09-16 18:16:05

Re: Thermal Energy Storage

#249 2024-09-19 12:17:09

Re: Thermal Energy Storage

#250 2024-09-19 13:08:39

Re: Thermal Energy Storage

Board footer