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.

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