Permenance Movement

tahanson43206 · 2024-10-04 21:21:59

For kbd512 re #75

First, thank you for your clear presentation in this post....

Since Terraformer is talking about boreholes 100 meters deep or so, I decided to see how many boreholes that deep and 1 meter in diameter would be needed to reach the volume you specified.

A cylinder of the size given would be 78 cubic meters and change.

That number divided into the total you provided would be: 59,843,448 wells, which is ** way ** more than you computed, so I assume your wells are deeper.

Calliban had been suggesting the UK consider taping hot crust at 1 km deep, so I changed the depth to 1000 meters. That reduces the number of wells to:

(785 cubic meters per well) 5,946,228 wells, which is still a ** lot ** of wells.

On the other hand, going that deep insures access to hot crust in much of the UK, so the energy stored from renewable sources would be supplemented by natural heating from the core, with the caveats that Calliban keeps reminding us... The energy flow from the core is slow due to poor thermal conductivity in the absence of water in the crust.

Follow up question: 78 cubic meters of Earth crust might have some use on the surface. ???

(th)

kbd512 · 2024-10-05 15:50:14

tahanson43206,

When you use natural temperature deltas for thermal energy storage, the system's volume is enormous out of necessity. It has to be that way because the energy density is so low. That is why energy storage materials must be incredibly abundant and not require any energy-intensive conversion process prior to using them. Water, air, rock, sand, salt, and Iron or Aluminum oxides all immediately come to mind. Everything else we have is a minor fraction of what we require to live as we presently do.

H2O (84.7bars / 1,246psi of pressure): 4,184J/kg⋅°C * (300°C - 20°C) = 1,171,520J/kg
Very hot highly pressurized H2O (300°C to 20°C):
434,000,000,000,000Wh / 325.42Wh/kg = 1,333,652,007,648kg or 1,333,652,008m^3 or 1.3337km^3

H2O (15.5bars / 228psi of pressure): 4,184J/kg⋅°C * (200°C - 20°C) = 753,120J/kg
Hotter moderately pressurized H2O (200°C to 20°C):
434,000,000,000,000Wh / 209.2Wh/kg = 2,074,569,789,675kg or 2,074,569,790m^3 or 2.0746km^3

H2O (1bar / 14.7psi of pressure: 4,184J/kg⋅°C * 80 * (95°C - 15°C) = 334,720J/kg
Hot to warm unpressurized H2O (95°C to 15°C):
434,000,000,000,000Wh / 92.98Wh/kg = 4,667,782,026,769kg or 4,667,782,027m^3 or 4.6678km^3

To supply 434TWh using diesel fuel:
434,000,000,000,000Wh / 5,350Wh/L (50% thermal efficiency, so half of 10,700Wh/L) = 81,121,495,327L
81,121,495,327L / 1,000L/m^3 = 81,121,495m^3 = 0.0811km^3

To supply 434TWh using U-235 (19,050kg/m^3) fuel:
Uranium 235: 3,900,000,000,000J/kg or 1,083,333,333Wh/kg
434,000,000,000,000Wh / 1,083,333,333Wh/kg = 400,615kg or 21.03m^3

Alternative thermal energy storage materials:
Al2O3: 880J/kg⋅°C * (800°C - 200°C) = 528,000J/kg
Fe2O3: 750J/kg⋅°C * (800°C - 200°C) = 450,000J/kg
"Solar Salt" / KNO3-NaNO3: 1,520J/kg⋅°C * (565°C - 290°C) = 418,000J/kg
"Pure Iron" / Fe: 450J/kg⋅°C * (800°C - 200°C) = 270,000J/kg

4X smaller is a meaningful difference, but requires a lot more technology to store the water as a liquid, namely boiler plate steel. I'm merely talking about heating up the water to 300C, keeping it pressurized at 1,246psi in a steel or steel-lined concrete pressure vessel so it doesn't flash to steam, and then siphoning off "the heat" using sCO2, and then transferring or "dumping" that heat into a much greater volume of water in a secondary loop which provides district heating. The input heat into the hot water tanks can be provided by resistive electrical heating elements powered by wind turbines, concentrated solar thermal, nuclear thermal, natural gas, or coal.

A typical commercial electric power reactor is pumping out about 3.75GWth if it's producing 1.25GWe, so we'd need 12 reactors to supply most of the input heat. If all of its power was dumped into a district heating system, then only 13 thermal power only reactors are required to supply the heat required. All told, all of UK's wind turbines produce 81.6TWh of electrical power.

UK consumed 357.2TWh of electrical power in 2005 (60.4M people), but only 266TWh in 2023 (68.7M people), because they installed a lot of wind turbines to provide a lot less power for a lot more money. UK has 9 nuclear reactors spread across 5 locations, with a demonstrated need for about 6 more reactors. All of the reactors could be engaged in direct heating applications, rather than electric power generation. That makes them incredibly simple water boilers. A very funny thing happens when you do this, though. You no longer have any use for a ridiculously large energy storage system. You only need pipelines, which are a lot more cost-effective and use a lot less material, but this requires uncommon sense.

That is the real reason we built modern society on hydrocarbon energy. Without a highly concentrated energy source, we couldn't produce enough materials to use natural energy systems at the scale required until after we harnessed the power of hydrocarbon fuels to do it. We've had mirrors, pipes, wheels, gears, pistons, and crankshafts for centuries, photovoltaics and batteries since the late 1880s, yet nobody built that first 1MW photovoltaic power plant until 1982. The ancient Greeks had a steam engine for crying out loud. All the basic tech was proven to work a century or multiple centuries before, yet manufacturing capabilities hadn't "caught up" to where science took us until 100 years and 1,000X+ greater energy abundance / pervasiveness later. Maybe 100 years from now we will truly have a workable all-electric solution we can manufacture at the scale required, but in the mean time we still need energy to keep people alive, in order to reach that coveted future state.

The H2O at 200°C vs 95°C only reduces total volume to 44% of the zero pressure system that runs 95°C to 15°C, but it adds quite a bit of cost, complexity, and extreme operating conditions requiring certified boiler pressure vessels. 4 vs 2 cubic kilometers is not a deal breaker, never mind a game changer. We're still talking about very large systems. H2O at 300°C is quite a bit smaller, but also requires another level of storage tech, with highly robust boiler pressure vessels being mandatory.

If you're wondering why I didn't use even higher temperatures for the Iron, ask yourself what you're going to use to transfer power and how long it's expected to not completely oxidize and then crack from repeated extreme thermal cycling at temperatures above 800°C. There are some materials which will work, but they're not cheap or abundant and require quite a lot of energy-intensive processing. Are you going to keep something super-heated under a hard vacuum so Oxygen in the air doesn't interact with it? How practical is that likely to be at the scale required?

This is why building energy systems which require either energy input or operating conditions extremes are mostly a waste of time and money, because they simply cannot scale up to the degree required to be truly useful at a human civilization scale. That's why I've gone so hard after nuclear thermal and solar thermal. Nothing else scales.

Water below its boiling point provides 80% of the heat energy storage capacity of much more energy intensive materials such as solar salt or various metal oxides would provide over a much greater temperature range. That means the physical size of your energy storage system doesn't get meaningfully smaller until extreme temperatures or pressures are involved. High pressures or temperatures are great for mobile applications where weight matters more than cost or complexity, or for generating electrical power, because the thermal efficiency of the turbo-generator goes up substantially, but it's ultimately a losing battle when you somehow have to source enough salt or other materials and process them into usable forms.

kbd512 · 2024-10-06 14:21:56

The UK's annual direct thermal energy consumption is 434 TeraWatt-hours of low-grade heating applications, which is presently provided by burning natural gas or heating oil. That is what we're attempting to replace with natural energy. Total global oil storage capacity is 1.1447km^3 or 7.2 billion barrels or 302.4 billion gallons. For a natural energy system to supply the UK alone with seasonal / winter heating using water heated to 300°C, the UK alone requires a pressure vessel storage capacity equivalent to total global oil storage capacity.

For anyone who thinks it's an unworkably large energy storage solution, realize that our electronics advocates are asserting that the oil and natural gas will somehow be replaced by electro-chemical batteries which consume materials that are orders of magnitude more scarce than water, concrete, and steel. On top of that, they require orders of magnitude more input energy to create, and last for perhaps 10 years at most, rather than 75 to 100 years typical of all thermal power plants.

The total materials weight and input energy requirement doesn't get any smaller using batteries, because water at 300°C stores more Watts of energy than Tesla Lithium-ion batteries, and water-to-water heat transfer is about as efficient as electro-chemical batteries attached to a grid. There's no energy conversion taking place here. Hot water is being used to directly heat-up buildings (homes) using storage tanks filled with hot water.

Even if said hot water was used to power motor vehicles, water heated to 300°C stores the same amount of extractable energy as a Tesla Lithium-ion battery pack, kilo-for-kilo or pound-for-pound. The pressure vessel storage container makes the solution modestly heavier than the battery pack itself, but the battery also requires a charge / discharge controller that pretty much cancels out any weight differential between the two solutions. If we can't re-power homes and motor vehicles using 300°C water, which is almost free in terms of energy input and availability, then what made anyone think we could do that using scarce metals such as Lithium, Sodium, and Copper?

You'll need the same weight of materials to implement either solution (electro-chemical batteries or 300°C hot water). One consumes a lot of water, concrete, and steel for pressure vessel liners and piping. The other requires Lithium and/or Sodium, Copper, Cobalt, Nickel, Aluminum, and a bunch of other metals to make the electronics. If we cannot do this with water, steel, and concrete, then we have no hope of doing it with far less abundant materials.

Why did anyone believe that electronics provided a more practical or faster-to-implement solution?

Where was the basic math which computed the materials requirements against materials availability and present total energy usage?

Apart from the work of Professor Simon Michaux, which has never been refuted by actual academics who study energy, I've yet to see any numbers pinned to these 70% photovoltaics / wind turbines / electro-chemical batteries solutions, regarding their total metals consumption and where we expect to source those materials from. For Copper alone, it certainly won't be Earth. YouTubers who earn their keep selling products don't produce half a dozen 1,000+ page studies backed by years of research, so finding a nit to pick doesn't begin to invalidate the entire premise of a report that large and comprehensive.

Professor Michaux's ideas aren't much better, but seem to boil down to:
1. Liquid Fluoride Thorium Molten Salt reactors to provide most of our energy.
2. Burning Iron powder to produce high grade heat.
3. Converting the Iron oxide powder from high grade heat production, back into Iron, and creating Hydrogen using human sewage, for the purpose of creating Ammonia to power large ships, trains, and airliners.
4. Somehow running society without most of the large trucks and motor vehicles that deliver goods.
5. Retaining some EVs for short range transport.

1. After going on at length about LFTRs becoming the future of electrical power generation, he then says that nobody actually knows how viable LFTRs are at a human civilization scale, because nobody has done the long term decay chain studies to evaluate what comes out of a LFTR, thus whether or not we can readily recycle that waste stream or dump it back into the reactor. This seems like a research project we should've completed decades ago, but we didn't, because we were too focused on producing nuclear weapons to care about how viable Thorium molten salt was for civil commercial electric power generation. I would be quite willing to spend the money to run the experiment to get our answers, but relying on an unproven technology to underpin the energy demand of modern human civilization is a serious problem.
2. The idea of replacing coal with Iron powder is intriguing, but how well-developed is the tech to do this? A pilot plant project is required to know for sure. I don't think there's a resource limitation here, so that's good, but electrolytic Iron production is very limited at the present time because it's very energy-intensive to do. You can get remarkably pure Iron, which could make alloy steels less necessary because all the undesirable things that weaken natural steel (Iron and Carbon) to the point of requiring alloying metals (Nickel, Chromium, Manganese, Cobalt, etc) are almost entirely absent, but I haven't seen energy-viable plans to scale-up to the degree required for that purpose, much less using it as a coal substitute.
3. Ammonia / Hydrogen from Iron oxide and human sewage is definitely a left-field idea, and also quite intriguing, but if we don't know, then we should run another experiment. Ammonia has great promise, and we're beginning to look at replacing Haber-Bosch, but only if we can scale the tech. I have no idea if this will work, because basic research is still in progress.
4. I've heard that large trucks are going extinct for decades now, yet we keep building more of them, so maybe we should figure out how to power them in the future. Running railways everywhere is also very expensive, because a lot of existing infrastructure would have to be torn up and completely replaced. I feel like a trade study is required here to figure out "maximum railroad", in the same way that Senator Tillman had the US Navy run trade studies after WWI about "maximum battleship".
5. I think EVs will supplant ICEs for short duration trips, but only if we replace the scarce battery materials with far more abundant, cheaper, and less energy-intensive materials. His beliefs about Sodium and Fluoride being cheaper is unfounded. Sodium is far more abundant than Lithium, but not in the form required to make batteries, and it's even more energy intensive than Lithium to convert it into that usable form, which is why global Sodium metal production is even lower than Lithium metal production.

That sums up current counter-narrative thinking on the future of energy, as well as my responses to it. All of his ideas require fundamental research to be done to know if they will work, or work at the scale required to actually replace what we're presently using. This is very predictable, because he's an academic and academia loves feeding money and status into itself. Frankly, I would like to see what we can do with air, water, concrete, and steel, because the tech is so exhaustively proven to work. For long range / heavy transport, I think the best solution, the one guaranteed to work, is to start recycling CO2 to make more fuel. I don't like gambling with energy, because you're literally gambling with peoples' lives. That's why we were still using so many horses and other draft animals a half century after we created cars. It takes time to know what works and why it works, as well as what new set of problems you're creating for yourself to solve later on down the road.

We already know what set of problems we'll have with intermittent natural energy systems, since we used them for most of the time humanity has existed, as well as how to minimize their impacts, and it's not by throwing more tech at the problem. Heck, the Egyptians and Romans knew you had to store water to avoid losing all of your crops to droughts. For whatever reason, all the energy we have today makes us believe that we can simply throw a switch to eliminate energy storage problems. That solution doesn't work past a certain scale. At somepoint, you need to accumulate truly enormous energy and material reserves or you will run out. For any kind of re-power solution, we're going to have to become far more pragmatic about which solutions we choose to pursue. Any major deviation from thoroughly proven solutions requires a substantial payback for it to be worth the asking price.

Calliban · 2024-10-06 17:42:08

Kbd512, what you are describing in the storage of energy in hot, saturated water, is a steam drum.
https://en.m.wikipedia.org/wiki/Steam_drum

A thermal storage system could make use of a combination of technologies. The steam drum is effective at storing energy in hot water up until the critical point of water (221.2bar, 374.15 °C). Go higher than 374°C and all of the water is steam regardless of pressure. We could have a steam drum generating wet steam and then a sand / rock heat store that is heated to a higher temperature, providing heat to a superheater, generating dry superheated steam. That is necessary for generation of power at high efficiency (above about 33%) using steam. Even ultra-critical cycles producing steam at temperature greater than 600°C, struggle to get much above 45% efficiency and corrosion becomes more of a problem the hotter the steam gets. But condenser temperatures of ~30°C would work for space heating if we took advantage of underfloor, inwall and ceiling heating. There comes a time when investments need to be made.

Steam drums are one of the most capital intensive parts of a steam powerplant. But this is an application where I believe pre-stressed concrete pressure vessels will prove to be useful. These have no practical size limit and allow economy of scale. They should also avoid a lot of the cost associated with engineering a pressure vessel, because strength is provided by multiple independant steel cables, rather than a single pressurised component.

tahanson43206 · 2024-10-06 18:54:51

kbd512 is looking at your post in the Google Meeting ...

Please clarify that the steel cables are outside the concrete .... kbd512 is asking how long that concrete shell will last.

(th)

Calliban · 2024-10-07 03:22:54

This paper discusses the design of several PCRVs.
http://www.civil.northwestern.edu/peopl … rs/175.pdf

The tensioning cables usually run through sleeves within the concrete, allowing them to be removed for inspection or replacement. Cables are tensioned using bolts, which transfer stress to steel spreader plates. In a PCRV, the steel cables take the tensile stress. The advantage being that for large pressure vessels, it is easier to engineer thousands of smaller cables than a single steel vessel that may require a foot or more of wall thickness. British AGRs operate at about 80 bar pressure and require a pressure vessel substantially larger than any LWR. It was simply impossible to create steel vessels with the required wall thickness at the time and remains extremely difficult and expensive today.

The concrete is effectively sandwiched between the inward compressive stress imparted by the cables and the outward compressive stress imparted by the contained pressure. So the concrete remains under compression. The concrete is not usually the life limiting component. But concrete may suffer from being exposed to high temperatures, i.e. above the boiling point of water for prolongued periods. This could complicate design somewhat. The yield strength of concrete is the point at which stress fractures begin to form within it. This is usually about 40% of ultimate compressive strength. When stress exceeds ultimate strength, the stress fractures join together and the structure crumbles.

For nuclear reactors, the shape of the vessel was constrained by the geometry of the core, the need for blowers and the need to accomodate boilers within the PCRV. For a much simpler heat storage system, the most efficient shape for the pressure vessel aporoximates a sphere. Boilers and blowers are not needed. If you are sending wet steam to a secondary superheater, you can do away with the need for steam dryers as well. In that case, the pressure vessel avoids the need for internal structure. It may need some form of solid mineral insulation and cooling channels within the concrete to protect it from thermal damage. I'm uncertain about that. I will see what I can find about concrete thermal stability.

Last edited by Calliban (2024-10-07 03:46:03)

Calliban · 2024-10-07 10:22:35

On a slightly different topic, concrete has been used as a solid thermal energy storage material. It is stable up to temperatures of 400°C, after which permanent chemical changes occur that undermines its strength.
https://www.sciencedirect.com/science/a … 462300008X

Solid concrete appears to be an excellent heat storage material. Its specific heat at room temperature is about 1.05KJ/kg.K and its its density is 2400kg/m3. Volumetric heat capacity is comparable to most rocks. However, we can pour concrete into a container in a way that eliminates void spaces and we can embed rock and other material within it. The concrete will retain enough strength to suppirt its weight and shape, so we do not need to be concerned with structural integrity. The low thermal conductivity of concrete (0.5W/m.K) could be improved by adding high thermal conductivity rocks and iron filings to the mix. I think thermal stabiluty could be improved further by reducing water content and using ultrafine sand and silica fume. The obvious advantage of storing heat in a material like concrete instead of compressed hot water, are avoidance of the need for a pressure vessel.

I would propose a combined approach to thermal storage. The thermal store should absorb intermittent electricity from the grid and return a mixture of stable electricity (40%) to the grid and low grade heat (60%) for use in a local district heating network. To do that we need to generate superheated steam with a temperature of at least 500°C. Different thermal materials are effective over different temperature ranges. Water can be stored at temperature up to 100°C without need for external pressure. Concrete can be used to store heat at temperatures between 100 - 400°C. To store heat at temperatures >400°C, we need materials that combine high volumetric heat capacity with tolerance to temperature and temperture changes. Crushed basaltic rock is an obvious choice. Purposefully designed bricks may be another option.

Each of these heat storage options can be used to heat the steam to different temperatures. But the superheat temperature is the most onerous. Saturated water at 300°C and 86 bar has specific enthalpy of 1.35MJ/kg. Superheated steam at 500°C and 86 bar has specific enthalpy of 3.49MJ/kg. So the superheater provides more than half the total enthalpy of the steam. So the high temperature thermal storage needs to contain a little over half of the total heat.

If we build TES units like this in sizes of 100MWe, then we have 150MWth of waste heat at temperature of about 30°C. That is enough to meet the annual space heating needs of about 100,000 homes if we can store heat underground. A TES powerplant could meet the heating needs of a small city.

Looking at UK RE production, there are a lot of peaks in production due to high wind or solar generation, with troughs lasting several days. We would aim to buy electricity during those peaks, store perhaps 30GWh as thermal energy in a bulk medium and generate 100MWe 24/7. In this way, a TES powerplant can have a smoothing function.
https://gridwatch.co.uk/renewables

Last edited by Calliban (2024-10-07 10:58:03)

tahanson43206 · 2024-10-07 11:14:36

For Calliban re recent posts ....

In particular, as I read #82, I ** think ** I am seeing a business scenario suitable for private enterprise.

I don't know anything about Great Britain, other than impressions, but I ** do ** know that private enterprise (and some cooperatives) produce most of the power for customers in the US. The scenario you just described, of smoothing power flow to a customer base, sounds to me like a business waiting to happen.

There are already businesses that perform that function in the US, but at the moment my impression is that these depend upon fossil fuel to meet customer demand. The scenario you describe would require investment, but once that investment is made, it looks to me as though the uncertainty of the fossil fuel supply can be eliminated from the business decision making process.

I note that this forum includes mention of hydroelectric facilities that store energy and deliver it as needed.

(th)

Calliban · 2024-10-07 14:57:46

Boiling water reactors generate steam at 285°C and have a net thermal efficiency of 34%.
https://en.m.wikipedia.org/wiki/Economi … er_Reactor

That is impressive because it is almost three-quarters of the Carnot efficiency. It achieves that efficiency partly because it is so large (1530 MWe) which reduces irreversibilities like heat loss and pipe friction.

It occurs to me that a site that can use sea water as a heat source could build a pumped heat power station. This would use a very large heat pump to pump heat from sea water at 12-17°C to a hot reservoir at 300°C. If we assume that the heat pump can get 70% Carnot efficiency, then we get 1.4 units of heat for every unit of input power. If we then turn heat back into electricity at 34% efficiency, round trip efficiency is 47.8%. For every 2 units of electric power we put in, we get 1 unit of electricity back plus two units of low grade heat at 30°C. That heat could be used for district heating.

But the scale of the plant is immense. An ESBWR produces 3GW of waste heat. That would be sufficient to heat 2 million homes if we employ seasonal heat storage and 1 million if we don't. In other words, the waste heat from just one of these powerplants would heat a large part of London if the pipework were in place to deliver the heat. We are talking about a pumped heat powerplant that is similar in size.

I think it would work better to have numerous smaller stored heat powerplants if the impact on efficiency is only small.

Last edited by Calliban (2024-10-07 15:08:09)

kbd512 · 2024-10-07 22:44:13

Calliban,

Thanks for the paper. It was an interesting read and I actually learned something about using concrete instead of steel.

I priced out concrete alone for above ground store, 5m inner diameter bore holes 500m deep, plus a couple of other materials. The costs are just so far beyond what a literal handful of reactors would require to provide district heating that I've kinda given up on this idea. We either go to much higher temperatures, or the cost of concrete alone makes a natural energy storage solution a non-starter.

At 3.75GWth, you guys only need 13 reactors to supply 434TWh of direct heating per year. That truly is the most cost-effective solution, and not by a little bit. Beyond that, a low temperature reactor design could be stupidly simple.

At $10B per reactor, 13 brand new 3.75GWth reactors cost $130B, maybe a lot less since nothing more complex than water pumping equipment is required. What kind of reactors do we have that can supply district heating water at 95°C? What kind of not-even-boiling water reactors could we build?

An above-ground "giant hot water tank" solution was $1.5 trillion.

A 5m inner diameter / 500m depth bore hole solution was about $35 trillion, with $33.485 trillion to drill the wells, at $100 per meter drilled.

To be quite frank, at this scale you'd have to recycle and recondition water-based mud to avoid running out of certain materials to drill with. We did that a few times for certain customers or use cases, but it's not as easy to do as it is with oil-based mud (which is almost infinitely recyclable, but comes with environmental challenges we probably don't want here) and it's usually more costly than buying new products. The sheer scale involved here would mandate recycling, though. That might be a good thing if we become more inventive about water-based mud recycling, but it'll definitely add cost.

At $139/kWh, a Lithium-ion battery solution was about $60.326 trillion to store 434TWh. Sourcing enough metal will be challenging, to put it mildly. This is enough battery making material for almost 5.8 billion Tesla Model 3 vehicles, a multiple of the global fleet of all vehicles of all types. I think the price tag succinctly explains why there are no grid storage batteries providing power for more than a few hours. I'm sure we could reduce this building more wind turbines, but then you'd have to pay for more wind turbines and batteries. There are nowhere near enough wind turbines presently in operation in the UK, though.

This is definitely a longshot idea, but is there any practical way to use trompes, tidal action, and heat from compression to heat up concrete salt water storage vessels sunk offshore into the ocean?

It's probably another technological dead-end, but I'm exploring unexplored options for reducing the size of the thermal energy store by using gravity to supply a steady energy input, regardless of season. Wave action is fairly reliable compared to the wind. You had a serious of posts I didn't really respond to involving sinking pre-stressed concrete pressure vessels to store compressed air. What about using the compressed air to heat up the water inside, so that no great pressure is being held back?

Maybe we need offshore trompes to feed-in compressed air, bore holes to store compressed air, ocean water to prevent freezing during later expansion, and water brakes to heat up the district heating water. The UK has 25GW to 30GW of available tidal energy resources, but that's still not enough. The basic requirement to supply the UK is 50GW of power. Your wind turbines supplied a constant 9.36GW, so you'd need a wholesale expansion of wind power, but the turbines could be really simple if all they do is compress air or heat up water directly.

I seriously doubt any of this will be cheaper or even comparable in price to a nuclear solution, but we should still put numbers to ideas, rather than blithely asserting ideas will or won't work, as if they were statements of fact, prior to using some very basic math to test those assertions. That's what our unthinking green energy enthusiasts did, which is why we now find ourselves in our current energy crunch, which nuclear energy could've solved decades ago.

Calliban · 2024-10-08 01:49:36

For the nuclear solution, the heat is actually free. We build nuclear reactors to produce electricity and the waste heat (which comes out of the condenser at 30°C) is a waste product that we build cooling towers to get rid of. The heat distribution system needed to get it to customers will not be free. The main problem with this idea is that reactors produce GW of heat and are often deliberately located away from population centres. So we would need heat mains to get it into cities and then an extensive distribution network to get it to various consumers. That is a lot of reinforced concrete pipes. It could be done. When SMRs reach the market, hopefully around 2030, these will be small enough to locate closer to our heat demand centres. But we are still talking about several hundred MW of waste heat for a single light water SMR. So nuclear reactors are city sized heating units.

For borehole geothermal storage, a single borehole 0.15m in diameter and 100m deep, costs about £10k and can supply 6kW of heat. So one borehole will supply enough heat for 2 average dwellings. There are about 25 million dwellings in the UK, so we need to drill 12.5 million holes at a cost of £10k each. That comes to £125bn, or about $150bn. That is the cost for the holes. The heat pumps and distribution pipework will cost more.

For the Carnforth scheme, my concept design was a 10MWth heat pump capable of supplying the whole town with warm water at 33°C. Some 1700 boreholes would be needed to supply input heat to the heat pump. These would be clustered into a green area just south of the town. The green area appears to be about 30 acres, which is more than enough to store a whole year of heat for the town. The town is quite compact, making heat distribution easier. A large heat pump using butane as working fluid is extremely efficient, with only 800kW of driving power able to supply 10MW of heat. That assumes a temperature rise of 18°C, from a heat supply whose temperature averages 15°C. To get that good a COP we need some way of recharging the boreholes with heat during summer. When heating starts around September time, we want borehole temperature to be around 16°C. By spring time, this will have dropped to 14°C. So pipework will be needed to gather heat from soil to recharge the boreholes.

Last edited by Calliban (2024-10-08 02:09:11)

Calliban · 2024-10-08 06:16:46

Article on nuclear district heating.
https://www.powermag.com/district-heati … er-plants/

Most studies focus on using nuclear waste heat for district heating. The Chinese have designed pool type reactors for direct heating applications. But the fact is that electricity is far more valuable than low grade heat. So it does make more sense thinking about district heating as a way of using otherwise wasted heat from an electricity producing powerplant.

This part interested me:
'Nuclear heat in the form of hot water can be economically delivered up to 100 miles away at competitive cost and with a heat loss of 2% to 3%.'

The cost in this case, is simply the cost of putting in place pipework to deliver the hot water and return cold water. In this case, probably buried reinforced concrete pipes. Whilst these do have a capital cost, their effective lifetime should be measured in centuries. For a small and densely populated country like England, it would appear to be entirely feasible to pipe heat from nuclear generating stations to major cities.

Sizewell B nuclear powerplant in Suffolk, is almost exactly 100 miles from central London. The single reactor unit produces 1198MWe and 2227MW of waste heat. The waste heat is sufficient for space heating for 900,000 dwellings at peak winter consumption. Even more if we can store at least some of the heat outside of winter months. This powerplant alone could provide about half of the heat needed by London.

The Hinkley C powerplant will have two 1600MWe PWRs when it is finally completed. It will produce 5900MW of waste heat. That is enough to heat 2 million dwellings at peak consumption and maybe twice that number if we can store the heat. Unfortunately, it is 150 miles from London. It is 105 miles from Birmingham. The various towns of South West England are much closer. Cardiff is 68 miles from Hinkley C by road.

Last edited by Calliban (2024-10-08 06:43:41)

Terraformer · 2024-10-08 06:43:10

Carnforth is less than 10 miles from Heysham 1 and 2 The whole district (whole bay?) could be heated by nuclear, the sticking point is the ridiculous Green Party that's in power there.

EDIT: Or maybe not. City Council leader urges support for extension of Heysham 1 & 2

Last edited by Terraformer (2024-10-08 07:11:11)

Calliban · 2024-10-08 07:15:32

Terraformer wrote:

Carnforth is less than 10 miles from Heysham 1 and 2 The whole district (whole bay?) could be heated by nuclear, the sticking point is the ridiculous Green Party that's in power there.

I think the key thing to remember is that being a Green is an entirely different thing to being an Environmentalist. Green is a rather cranky political ideology that includes esoteric things like trans-rights, equality and inclusion and all that toxic nonsense. Environmentalism is about trying to meet human needs without damaging the plight of other living things on Earth. You can be an environmentalist without being a Green. In fact I would argue that the Greens have done a lot to damage environmentalist causes. They tend to be highly idealistic and impractical people that shoot down practical solutions in the name of ideological purity.

But I digress. Given how compact the UK actually is, I wonder if we could establish trunk lines for distribution of nuclear heat over long-distances? These would be large concrete pipes, several metres in diameter, with water pumped through them at about 10m/s. A trunk line could snake around the various population centres of England and would carry 10s of GW of heat. A large city like Birmingham, would take off maybe a GW of hot water at 30°C and would dump cold water at, say, 15°C into a return line. Nuclear powerplants would dump hot water into the hot line and would receive cold water from the cold line. The trunk line would have various branches allowing it to deliver hot water to towns and cities distant from the trunk.

Last edited by Calliban (2024-10-08 07:24:08)

Calliban · 2024-10-08 07:51:01

My idea for a trunk man: A pipe some 6m in diameter, carrying hot water at a flow velocity of 10m/s. A similar pipe would carry cold water in the opposite direction. Assuming the hot water has a temperature of 30°C and a 10°C temperature drop occurs during space heating, the pipe will be carrying almost 12GW of heat. At different points, branches will take off hot water and waste heat suppliers (large powerplants) will dump hot water into it. I had in mind a ring main that passes through the major population centres of England. We would extend it up to the Scottish central belt as well. South Wales would be served by a spure off of the hot and cold mains.

One side benefit is that no powerplant build anywhere within 100 miles of the trunk would need to build cooling towers. It would dump hot water into the hot main and get cold water from the cold main. Below is a map of the UK showing urban population centres.
https://ontheworldmap.com/uk/large-deta … -towns.jpg

Pipes would be reinforced concrete potentially with polymer lining. Insulation will be provided by soil piled over the pipe. A project like this is comparable in size to building a major motorway. But it only has to be done once. Once completed, this sort of infrastructure should last for an almost indefinite period.

At peak winter demand, each of the UKs 25 million dwellings will need 3kW of heat. Let's assume that 80% of UK housing stock is connected to the network. We would need 60GW of heat. ESBWR reactors produce 1.54 GWe and 3GW of waste heat. So in theory, twenty of those reactors could meet most of the UKs heating needs and most of its electricity needs as well. If these plants cost £10bn each, that would imply a cost of £200bn to take care of 80% the UKs heat and electricity needs for the next 80 years. That is a capital cost of £2941/ person. Or £36.70 per person, per year. Seems like a bargain. To be honest, I don't understand why the UK as a nation cannot commit to doing something like this. It would be a huge long-term infrastructure project. But the costs per capita would be quite low in the long run. The same is true for most other European countries.

Last edited by Calliban (2024-10-08 08:24:11)

Terraformer · 2024-10-08 09:32:08

Doesn't Scotland have a couple of nuclear power stations already? Or at least, did. And in the Central Belt too.

I know electricity is valuable, but I wonder how the costs compare for one for solely heating use. Without running it at boiling temperatures isn't complexity decreased and safety increased? Idk, maybe getting approval for a heat only SMR would be an easier sell... Got to consider politics as well here, unfortunately. Something something bird in the hand. And the really expensive part is going to be the distribution grid anyway, so we can pivot later to whichever the cheapest source of heat allowed is.

Finnish SMR targets district heating market. Why not have Rolls Royce manufacture some?

Last edited by Terraformer (2024-10-08 09:41:22)

Calliban · 2024-10-08 10:04:58

A pure heat producing reactor could be a pool type reactor. It would not require a pressure vessel, just a reliable containment vessel. So reinforced concrete, lined with stainless steel. Probably in a pit. Water can provide the shielding needed. Such a reactor would produce very little radioactive waste on decommissioning. It would have a very high level of inherent safety, given that a huge pool of water above the core would have to evaporate before the fuel were uncovered.

UK natural gas is running at about £1/therm, which is £0.034/kWh. Could a nuclear heat source produce thermal energy that cheaply? I would say that it is quite possible. The problem with nuclear power in any context is that site licencing strategy makes it an absolute pain in the arse to build anything. There is just so much paper work and red tape. This why it costs so much to build what are in reality, uranium heated boilers. None of high costs are inherent. They are a consequence of the climate of fear that has grown around nuclear energy. And regulators respond to that fear by making nuclear reactors very difficult to build.

Last edited by Calliban (2024-10-08 10:07:48)

kbd512 · 2024-10-09 23:00:07

This has to be the simplest and cheapest type of reactor to build, one not subject to extreme operating conditions that mandate expensive reactor control systems. The fuel doesn't need to be an expensive ceramic because it won't get hot enough to warrant the cost and complexity associated with fabricating UO2 pellets. The fuel can be a natural Uranium metal alloy, so there's no expensive and unnecessary enrichment process. Fuel recycling would consist of melting the metal, extracting unwanted fission products, and re-casting fresh fuel rods. The greater physical size of a natural Uranium reactor has little meaningful effect on cost, relative to all the other technology required to make it function in a specific way.

You still have to keep the core covered with water, but it operates at zero pressure and very modest temperature, so it's not dependent upon powerful pumps to continuously supply highly pressurized water to prevent the water from instantly flashing to steam. We can use water pressure or core temperature to keep the control rods suspended over the core. If pressure is lost or temperature spikes, then the control rods drop automatically without operator intervention. Overheating is possible with any reactor design, but this one is the least likely to overheat because we're not attempting to achieve high temperatures for sake of efficient electrical power generation. We're utilizing direct heating to cut out all the energy conversion losses and complexity associated with electrical power.

A tertiary water desalination thermal loop can be run in the summer to replenish fresh water losses and to supply drinking water. The reactor would heat the sea water in the secondary loop to 95°C, and then a modest amount of natural gas or solar thermal power can complete the process of flashing the sea water to steam. The residual salt can be sold for human consumption, deicing roads, or used to supply the material input to make Sodium-ion batteries so that every wind turbine has its own battery bank to buffer electrical power onto the grid in a predictable manner, not subject to the vagaries of wind speeds. Any other metals present (mostly Potassium, Magnesium, Lithium, and Uranium) can also be collected and processed. CO2 should also be separated and stored to make synthetic fuels.

Terraformer · 2024-10-10 03:05:35

Re. nuclear waste heat and boreholes, it seems that every option for heating besides direct nuclear (which presumably can be throttled over a year) would benefit from some means of interseasonal storage. If we're relying on reactors for electricity, that heat is being wasted in summer.

What's the waste heat production for Britain's current reactors, 10GW? I know they provide about 5GW of power. If some means of storing that heat was available, would the existing fleet be enough, combined with actually insulated houses?

The boreholes (storage) and network (distribution) concept seems to be pretty agnostic about what the source of heat is. Which is a bonus, because it doesn't become a stranded asset if we decide to pursue a different heat source. The systems in Europe have proven this.

Calliban · 2024-10-10 03:43:31

The UKs existing nuclear fleet, with the exception of Sizewell B, doesn't have much life left in it. All of the Magnox and about half of the AGRs have now closed. We made the historically bad decision of focusing nuclear development on graphite moderated, CO2 cooled reactors. Graphite oxidation in hot CO2, places hard limits on the operational life of these reactors. If water suffers irradiation damage, the irradiation products can be recombined to make water again. Water can be cleaned of contaminants and replaced if need be. That is impossible for graphite moderator blocks. When they degrade to the point where they no longer have reliable structural integrity, the reactor is done. The problem was known about. The reactors were designed for a 40-year life and most of them have or will meet that. There is just no option for life extension in the way there is for LWRs.

One minor technical point: Water moderated reactors cannot run on natural U, because light hydrogen absorbs too many neutrons. The Soviets got around that problem by building graphite moderated, water cooled reactors (RBMK). The water coolant still absorbed neutrons, but reactivity margins were still high enough to allow criticality using natural U, provided that other loss and leakage mechanisms were strictly controlled. So the Soviets were able to build pressure tube boiling water reactors that ran on natural or very low enriched uranium. That technology does have some great strengths. It allowed the Soviets to build very large and powerful reactors quite cheaply on a relatively meagre resource base. In its way, the RBMK was superior to western LWR technology. But it had also dangerous weaknesses, as the world learned at Chernobyl. So a pool type reactor needs low enriched uranium fuel. The alternative is to build graphite moderated reactors, that can use nat U, i.e. Magnox. But pool type using LEU is by far the simplest and probably cheapest design.

Last edited by Calliban (2024-10-10 03:50:11)

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