Permenance Movement

Calliban · 2023-03-22 19:06:46

1. On the topic of railway longevity, curvature has a big impact on track wear. Heavy freight trains can also do a lot of damage if wheels slip on the track. Ensuring that loads are well distributed and freight cars are kept beneath loading limits is important. But ensuring that track is straight and level is a beggining of life planning decision that will effect maintenance costs for centuries to come. We do have railway track that is a century old. But heavily used track in high curvature areas can wear out in 10 years or less.
https://www.quora.com/How-often-on-heav … ar?share=1

2. Roman roads were thick structures that were more like underground walls. The surfaces were made up of heavy stone blocks, which were held in place by gravity and lime cement.
https://en.m.wikipedia.org/wiki/Roman_roads

In the modern world they would be expensive and labour intensive to create. But they appear to have been more durable than modern tarmac roads. I wonder if they offer any lessons for how we might build roads with permenance in mind? A solid stone surface is harder than tarmac and should be more resistant to wear, but could be vulnerable to cracking if subject to heavy point loads from heavy vehicles.

On Mars and the moon, there is no tar to produce road surfaces. But the Martian soil contains gypsum and will provide a good mortar if wetted. Lunar fines are naturally sticky. Loose stone of various grades is also abundant on the Lunar and Martian surface. These will provide hardcore which will help spread load. Maybe we can cut loose stones into rectangular blocks to provide the camber. On the moon and Mars, roads will be important infrastructure, as regolith fines are highly abrasive. Exposure to these fines will severely reduce the effective lifetime of vehicles. So a hard, clean surface with low friction would be valuable.

3. Forest gardening is a non-till form of agriculture that preserves soil fertility, avoids soil erosion and obviates the need for ploughing. Many trees can be grown in dwarf varieties to allow easier harvesting. Nut trees like walnut can last hundreds of years.
https://en.m.wikipedia.org/wiki/Forest_gardening

4. Ditch the batteries! Why compressed air has a brighter future.
https://www.lowtechmagazine.com/2018/05 … orage.html

For short term energy storage associated with grid frequency control, low pressure compressed air could be a resource cheap way of storing modest amounts of energy. At low pressures, air can be compressed isothermally. For air at pressure <1 bar, we could create underground air stores by digging trenches and then providing say 2m of dirt and rock overlay, turning the trenches into underground tunnels. Air stored in these tunnels would have pressure of about 1.5 bar(a) or 0.5 bar(g). This is quite low energy density. But the tunnels, once built, could last for centuries. A water locke, rather like a toilet u-bend, would let out excess air if pressure rose too high. This prevents any potential for overpressure. This is a CAES system that is uncomplicated and simple enough for people to make themselves. Because containment relies onmthe static pressure provided by overburden, there are no life limiting fatigue problems.

Each cubic metre of air at 0.5bar(g), will store some 60.8KJ of energy. To store 1kWh, some 59m3 of storage volume would be needed. Assuming that tunnels are dug 2m deep and 2m wide, some 15.25m of tunnel must be dug per kWh stored. If we were to tunnel through 1km2 of land, such that 50% of the surface are is ubderlane by tunnels, we could store some 16.9MWh. The land on top of the air store could be farmed, provided that some weight margin is provided.

Last edited by Calliban (2023-03-22 19:56:57)

SpaceNut · 2023-03-23 19:56:31

Between hot and cold we are very close to making a sterling energy generator.

Calliban · 2023-04-03 13:37:47

I learned today that the US railroad system provides about 40% of the total inland freight ton-miles. Trucks make up about half and water about 10%, with air providing about 1%. That is very impressive when you consider that rail consumes less than 2% of the total transportation energy consumed in the US. I cannot get exact figures because eia lump buses and trains together. As if they have anything to do with each other.
https://www.eia.gov/energyexplained/use … -depth.php

Below is a link that contains a map of the us rail network.
http://www.destination360.com/travel/us-railroads

This tells me that there aren't very many population centres in the US that are more than about 30 miles from a railway. And railways are a very energy efficient way of transporting goods. We know that rail can be used to transport goods because it already is. It isn't new and exciting, so it tends to get ignored as something that we might rely upon more in the future. If we are heading into tougher times, with less liquid fuel available, it strikes me as a sure bet that rail transportation will be a promising technology to expand upon. We don't really need any radical new technology to make it work, because its costs are relatively insensitive to energy costs. This is not the case for trucking, which is about an order of magnitude more energy intensive per ton-mile.

A sensible national strategy would look for ways of extending railways such that every large town has a rail hub that businesses can use. Trucks can then be used for shorter distance transportation to and from rail hubs. This would cut down the average distance travelled by truck. Even without a change in technology, this would reduce average fuel consumption per ton-mile. But limiting trucks to short distance trips opens options for powering them using lower energy density energy sources. This could be battery-electric, a synthetic fuel, compressed or liquid air, flywheel, stored heat, etc. These solutions are very difficult for long haul trucking, but for smaller vehicles with shorter range, they look more practical. If a truck needs to ship goods from Long Beach California to Las Vegas, it will add a lot of cost if it is forced to work on a low energy density fuel. The number of stops will increase. Journey times will be longer. But if a truck is needed only to ship goods from a Las Vegas rail hub to suburbs within 20 miles, then a large number of technological options are possible for that truck, because energy density requirements are relaxed.

Discussions with Kbd512 have identified a number of potential options for powering freight trains. We have discussed molten salts, liquid air, hot saturated water, direct-electric, nuclear fission and biofuels. All of these options are workable for rail vehicles because of the inherently low friction factor of steel wheels on steel rails and the low air resistance of long thin vehicles, travelling at modest speeds. We can get away with relatively heavy and low energy density power sources. Large diesel engines can also be adapted to burning fuels that are unsuitable other uses. Ship engines used to burn bunker fuel, which is viscous and requires heating before injection. The point is, that in a world of less abundance, a freight transportation system that combines local truck freight with regional rail, provides our best option for a goids transportation system that breaks the need for abundant, high quality liquid fuels.

Mars_B4_Moon · 2023-12-01 13:33:22

Ancient Roman road found in Stirling garden
https://www.bbc.com/news/articles/cn0d83q4ng1o

Calliban · 2023-12-13 10:42:42

Something Terraformer wrote a while back got me thinking about the idea of generating power from interseasonal temperature differences. If we invest in borehole heat storage systems, we can build wind catcher towers and store summer heat underground. Come winter, the same wind catchers will be exposed to cold air, allowing winter cold to be stored in an ice house. A heat engine running between the two reservoirs could generate baseload power 24/7/365.

The power density of this interseasonal heat engine wouod be poor. But boreholes, ice houses and wind towers, are passive components without moving parts. They shoukd last for centuries once constructed. So the high embodied energy cost can be ammortised over a long period of time. This sort of thermal difference engine would work best in places with a relatively high annual temperature swing. In the US, this wouod work best in the western states.

On Mars, there are huge temperature fluctuations between day and night. Something like this could work well there. Solar power on Mars doesn't neccesarily need to rely on PV. The daily temperature fluctuations are so extreme that flat plate heat panels, attached to thermal reservoirs, could harvest both hot and cold needed to drive a 24/7 heat engine.

Last edited by Calliban (2023-12-13 10:55:15)

Mars_B4_Moon · 2024-03-30 14:59:55

Nevada lawmakers back bill that aims to free up Hoover Dam funding

https://lasvegassun.com/news/2024/mar/3 … ree-up-fu/

Terraformer · 2024-03-30 15:17:00

I've also suggested before that flat plate collectors/radiators could work in deserts for a low power density but very cheap and simple base load system. Nighttime temperatures can get low enough to freeze water, daytime flat plates can reach maybe 80c? 60c? Enough to get power -- iirc you talked about using butane as the working fluid.

When it comes to space based power, flat plates should be able to get *really* hot, radiators really cold, and afaik using mirrors is far easier. I just don't see solar PV being able to compete if we're using say Lunar ISRU. Not even if we're bringing the system from Earth, potentially. Solar thermal could allow a rapid buildout of space based solar power generation using Lunar resources. And with that power we can smelt aluminium and ship it down...

kbd512 · 2024-03-30 20:41:33

I found this hydraulic Sun tracker that requires no electricity or external power to follow the Sun:

This is the sort of tech we'll need, both here on Earth and on Mars, after our attempts to turn every last bit of tech into short-lived electronic motorized gadgets, ultimately doesn't produce the result we're after.

Calliban · 2024-03-31 15:59:12

Terraformer wrote:

I've also suggested before that flat plate collectors/radiators could work in deserts for a low power density but very cheap and simple base load system. Nighttime temperatures can get low enough to freeze water, daytime flat plates can reach maybe 80c? 60c? Enough to get power -- iirc you talked about using butane as the working fluid.
When it comes to space based power, flat plates should be able to get *really* hot, radiators really cold, and afaik using mirrors is far easier. I just don't see solar PV being able to compete if we're using say Lunar ISRU. Not even if we're bringing the system from Earth, potentially. Solar thermal could allow a rapid buildout of space based solar power generation using Lunar resources. And with that power we can smelt aluminium and ship it down...

Simple thermal systems like this could have really impressive lifetimes. A flat slab of stone can absorb heat and radiate heat for centuries before weathering finally cracks it. A low rate of energy return could add up to an impressive EROEI if the system lasts a long time. Solar thermal systems do seem to be more resiliant.

As a general principle, one way of living on low power density renewables is to build systems that don't wear out very quickly. Provided the investment window is long enough, we can increase EROEI by making systems that last longer. We have brick towered windmills dating back to the 17th century. But the sort of engineering this requires appears to diverge greatly from what we are seeing in practice. This is because economics is just as concerned with rate of return as it is total return.

Last edited by Calliban (2024-03-31 16:07:07)

Terraformer · 2024-06-05 02:25:21

What principles would you put in a Permenance Design Manifesto?

To some it up, I'd say: "Use what is abundant, and build to last." But what does that look like in practise? Simplicity in design -- so it can be maintained/repaired/replaced fairly easily by the users and has fewer things that can go wrong -- is definitely on the list. Building with very large margins so that normal use causes very little wear? Choosing materials that are known for their longevity (e.g. stone masonry vs reinforced concrete).

Neither techno-optimism nor degrowth, but a third, more obscure thing

Terraformer · 2024-06-05 03:13:59

Some overlap I'd expect with the Owner's Manifesto

306528267_7bb0ac881a-1.jpg?resize=342%2C500&ssl=1

kbd512 · 2024-06-05 06:24:56

I want my cell phone to be truly excellent at making calls and sending text messages, even if there's electromagnetic interference or low signal quality. Text-based e-mail would also be nice to have. Whether it can feasibly do anything else is largely irrelevant to its utility as a cellular telephone. I think that could be done using a single chip on a single circuit board, some bits of plastic, a battery, and an antenna. It might be possible to power something that simple using a photovoltaic cell so that recharging means turning the phone over and leaving it in sunlight.

That's my conception of what a cellphone is or should be, which is markedly different from a full-blown mobile computer.

Calliban · 2024-06-05 14:20:06

Terraformer, I like the list. It isn't possible to build things that never wear out. But modularising devices to make use of standardised, interchangable components, is a way of making them endlessly repairable.

We are entering a period of history in which technological progress is slowing down. Some view this with dread. But it does have silver linings. If you buy a computer, a phone or a car, that is unlikely to be surpassed technologically in 20 or 30 years, then there is less incentive to replace it and more incentive to repair it. We are also entering a period of shrinking population, declining scale economies, expensive capital and labour and expensive energy. Collectively, these trends would appear to favour a design philosophy that designs things to last. This is always the most efficient design philosophy for society as a whole. Even if a shorter lived item is cheaper to build than an item that lasts twice as long, you still have to buy it twice rather than once.

In Britain, we continue to benefit from the long-lived infrastructure laid down by the Victorians. They built in stone and iron and everything they made was deliberately over engineered. The railways, the ports, the universities, the building stock. These things were paid for once and we maintain a strong position in the world because we are able to continue leveraging that infrastructure, a century or more after it was built. That gives us an advantage over other nations that have to build those things from scratch.

The US pioneered the development of light water reactors. Great effort was made to ensure proper chemistry and materials controls, such that these reactors remained fit for purpose. It is now anticipated that some of them will be able to operate for a whole century.
https://www.utilitydive.com/news/how-lo … rs/597294/

The advantage this provides to the American economy is significant. These units paid off capital costs decades ago. Fuel costs are small. Only maintenance costs and operating proffit are applicable to the cost of power. By designing units that can last a century, the American pioneers of nuclear power ensured that their grand children enjoyed some of the cheapest electricity on Earth. They did this thanks to a design philosophy that focused on building things to last, to understand how they degrade with time and allow easy repairability. Even it cost a little more to design these reactors with that much attention to detail, the value of a 100 year operational lifespan to future (now current) generations, makes it immiediately worthwhile.

We need to apply that thinking to everything we do. Whatever we make should be designed to last as long as possible and it should be easily repairable when it breaks. This becomes more and more important as we enter a period of more expensive energy, in which demographic decline also undermines mass production. Everything becomes less affordable. If the things we buy are designed to last for a long time, it will certainly cushion the blow.

The use of renewable energy is considered a desirable outcome to our political elites and idealists. The problem is that low power density makes RE absurdly resource intensive. This undermines the energy return on energy invested (EROEI). This isn't such an issue innan era in which most naterials are mined and refined using cheap fossil fuels. But when those inputs are gone, the high materials requirements of renewables will be less sustainable. But this is less of an issue if we build long lived infrastructure, using recyclable materials. This is the main reason I keep advocating for traditional stone towered windmill technologies, with more optimised blades. These things were expensive to build, but have lasted for centuries. If an energy source has high upfront embodied energy, it can still provide a respectable EROEI if it lasts for a long time.

Last edited by Calliban (2024-06-05 14:45:49)

Calliban · 2024-09-26 03:36:20

The return of the public bath house? This is certainly a more sustainable way of keeping clean. And as the article makes clear, a public bath house is social and recreational in a way that a private bathroom is not. It is more energy efficient and more compatible with the need to store thermal energy for long periods.
https://solar.lowtechmagazine.com/2024/ … bathhouse/

The energy transition is being rolled out as a different way of powering our existing way of life. Few people seem capable of thinking laterally and realising that living on a different resource set means changing the way we live. Living on low power density, intermittent renewables, requires that we live in ways that combine greater energy efficiency with energy storage. That means public bath houses. Community based laundries. Communal kitchens. Communal food storage. District heating. Spending more time in larger buildings, that require less heating per unit of habitable volume. In short, the way of life that works well on intermittent renewables is completely different to the way of life we have now. The sort of insular lifestyle where everyone has individual facilities in their own home and lives far from other people, was only possible because of the cheap, storable and abundant energy provided by fossil fuels at the height of their abundance. Living well on low density, intermittent energy, means changing completely the way in which we live.

This restores the historic reality that led people to congregate into cities. Before fossil fuels, it was only possible for humans to achieve great things by pooling their resources into collective projects. Fossil fuels granted us a reprieve from that reality. Living on intermittent renewables will restore the historic driver to urbanisation with a vengeance. It will be even more important in the future than it was before. In pre-oil times, it was advantageous to collectivise facilities to achieve energy savings and economies of size. Living on intermittent renewables, it is going to be the only way of being able to achieve those facilities at all.

The way that we work will be different on intermittent renewables. Factories will run when nature provides the power that they need. The workforce will have to respond accordingly. When the wind is blowing strong, 12 hour shifts will be the norm. During low wind periods, you will be down to six hour shifts and you only be paid for six. This will be difficult for people to adjust to. Transportation will be slower and speed will fluctuate.

Many of those advocating for a future based on intermittent renewables, seem scarcely aware that a different energy paradigm necessitates a very different way of life. It won't be the way of life that they are accustomed to. And I don't think people will enjoy it on balance.

Last edited by Calliban (2024-09-26 05:24:18)

Terraformer · 2024-09-26 06:51:49

OTOH, there's still a fair bit of room for automation in a lot of work. Which will also necessitate a shift away from a 40hr work week for everyone model, but it does mean that there'll need to be far fewer people involved in energy intensive sectors that have to adjust working hours to match the weather.

"One big building" doesn't have to be an apartment block. Functionally, a block of terraced houses counts as a single building. And apartments can still have their own external entrances (e.g. cottage flats). A block of eight terraced houses could be insulated as one and have a shared heating system. Of course, as we've talked about many times, hot water should be pretty cheap... and electricity is expensive, but is only needed in fairly small quantities.

It's mechanical power that's the bottleneck here really. Well, and high grade heat as well. So we can still have baths, but brick manufacture is going to struggle. Freight transport can be buffered; passenger transport cannot. That said, for things that can be buffered we might be able to use them as dump loads to maintain a minimum level of service e.g. diverting power from bulk freight to passenger rail so that people can still get where they need to go. And we could even keep cars, and accept that some weeks we'll be leaving them at home and taking the train instead because there's not enough fuel...

I'm still very much in favour of building out universal basic infrastructure though, even if I don't think it should be primary, instead of a fallback position. It's good to have options, and if people aren't willing to build for intermittency before they're forced to it will be necessary to build it so society has something to fall back on when it finally hits them.

Calliban · 2024-09-26 08:29:23

We should look into brick, cement and steel manufacture as seperate items.

Centralised mechanical power can be provided quite cheaply, in the UK at least, from the wind. The problem is that it too is an intermittent resource. Maybe automation can help us work around the problems that creates. But in principle, a factory could be provided with mechanical power using a line shaft or hydraulic power transfer system that is directly powered by the wind. Electricity doesn't need to be part of the process, but it would be useful to retain some electrical inputs for actuation and computer control systems. But the main power inputs could be pure mechanical. Hydraulic drives make the routing of mechanical power relatively easy compared to line shafts. Factory layouts should be no more constrained using hydraulic power as they would be using electricity. The use of mechanical power simplifies things considerably, as mechanical drives are simpler. Hydraulically powered equipment should ultimately be cheaper to build.

As power levels drop, the computer controlling factory processes would have some processes running more slowly or would prioritise some processes over others. When wind is low, we take the opportunity to clean and repair equipment. When wind is producing more energy than peak demand, some can be stored as heat by using the excess power to drive a heat pump. I think it could work. A 1MW wind turbine on land, close to the coast, will produce about 300kW on average. That is sufficient for a small factory.

Last edited by Calliban (2024-09-26 08:34:04)

Terraformer · 2024-09-26 08:40:11

It will disappoint David Mitchell, but other countries have access to energy sources that will be perhaps less Intermittent, Australia with solar power say. Maybe we should let friendly countries that are better suited for it take care of energy intensive bulk materials processing, and ship refined products here.

Wrt building materials, cut stone has a far lower embodied energy than brick, and should be more amenable to intermittency than concrete production is. A scenario where we import cement mortar and build using cut stone is not really any worse than one where we manufacture and use concrete blocks.

kbd512 · 2024-09-26 11:47:20

Terraformer,

If you have real energy storage infrastructure, of the sort our green energy advocates studiously avoid building or explaining why they don't like to spend money on, unless it's laughably inconsequential electro-chemical batteries, then your power supply becomes a lot more reliable. All the money spent on electrical and electronic devices, which are very expensive per technology unit, is the reason why there's no money left for energy storage, which provides stability. It's not possible to "overbuild" intermittent generation sources to the point of not requiring massive amounts of energy storage, assuming the end goal does not include transforming large swaths of the Earth into a toxic electronics waste dump while killing large numbers of people during that process due to simple lack of energy to stay warm or grow food.

By all means, use more natural and lower energy input materials like stone whenever they're accessible, but that requires heavy industry. This is why building up energy stores are key to everything else. Outside of oil, gas, and coal, we basically don't have any, relative to our consumption volume and patterns. The store can be water, compressed air, heat stored in rock or salt, but it must be built before de-industrialization is possible without killing most people.

The recalcitrance towards accepting the requirement for energy stores is baffling to me. There are no walkable cities, there are no supermarkets, and there is no health care without on-demand energy access. It's not flashy or sexy, much like sewage management, but running water and sewage management is the only reason large modern cities can exist. A wind powered / water pressure driven transport pipeline or railway can become the new shipping and trucking, bamboo / flax / hemp / stone can become the new-old housing materials, and we can do more walking when distances are reduced, but all that energy storage infrastructure to enable that has yet to be built.

Calliban · 2024-09-26 15:10:52

I find it puzzling that so little importance is placed upon reliable energy infrastructure. I can only summise that this is due to the cluelessness of the people in government who make decisions on these problems. They tend to be educated in law, history, economics, finance, politics and public relations.

As time has gone on, technical aptitude has disappeared from central government. No one in government now has any understanding of physics or engineering. These people are clueless about the physical systems that keep the world's nations working. They think economies are financial systems that run on money. Somehow our leaders have lost touch with the reality that the economy is a collection of physical processes that make the physical goods and services that people need. It takes real resources to do those things. Money is merely the medium of exchange involved in buying and selling. It is not a resource in any way, it is merely a contract that people pass between themselves. In reality, the economy is a thermodynamic machine that uses energy to rework matter into goods and services.

As simple as that should be to understand, it is not understood at all by the people that run western governments. It was better understood fifty years ago than it is now. This is why these people make naive and disastrous decisions on energy policy, which is in reality as important to the health of the economy as food is to human life.

Last edited by Calliban (2024-09-26 15:28:30)

kbd512 · 2024-09-26 22:21:12

Calliban,

Politicians are not technical people by their very nature, because they're supposed to be managers. I can accept their lack of understanding. I do not understand the treason of our intellectuals, those who ought to know, but refuse to speak truth to power. The behavior of our academics and technocrats is what I find so inexcusable. Of all people, they must be truthful with themselves. If it means whatever they find aesthetically or ideologically pleasing must be sworn off in favor of workable alternatives to otherwise unsolvable problems, then so be it. Lack of pervasive and affordable on-demand energy is a true existential threat to human civilization when we do not have it. The temperature can go up or down 2 or 5 or 10 or even 20 degrees, as it already does every single day. As long as we have abundant energy, we can work around that. There is no workaround for sustaining cities of millions of people without sufficient energy. If the energy isn't there, when and as required, only bad things happen shortly thereafter.

Calliban · 2024-09-27 06:55:37

kbd512 wrote:

The recalcitrance towards accepting the requirement for energy stores is baffling to me. There are no walkable cities, there are no supermarkets, and there is no health care without on-demand energy access. It's not flashy or sexy, much like sewage management, but running water and sewage management is the only reason large modern cities can exist. A wind powered / water pressure driven transport pipeline or railway can become the new shipping and trucking, bamboo / flax / hemp / stone can become the new-old housing materials, and we can do more walking when distances are reduced, but all that energy storage infrastructure to enable that has yet to be built.

Starting in the early 1990s, the UK went on a mass building spree of combined cycle, gas turbine powerplants. Until the turn of the century, the UK north sea was able to provide a growing supply of natural gas. Natural gas largely displaced coal. By 2022, the UKs few remaining coal burning powerplants had switched to biomass. Even after the peak of the UK north sea, Norway and Russia were able to supply enough piped gas to keep up with demand, albeit at a higher price. Wind and solar capacity had built up to the point where they were meeting sizeable portions of UK electricity demand after about 2010. Today, about 40% of UK electricity comes from the wind. This has been done with very little storage, because CCGT have been able to serve as backup powerplants, albeit at the expense of their own market share.

Two things have changed since 2020.
(1) RE capacity has now reached the point where supply during high wind conditions is exceeding grid demand with increasing frequency. When that occurs, the only option at present is to curtail production by shutting turbines down. That is clearly very wasteful as it forces down the effective capacity factor of the turbines.
(2) Russian gas supply to Europe has declined sharply. What remains is a mixture of much reduced imported Norwegian production, LNG mostly from Qatar, and the what remains of the UK north sea, which the UK government seems determined to kill as quickly as possible. This has pushed natural gas prices much higher than they were in the previous decade.

So the old strategy of using CCGT as backup is failing. RE supply is exceeding grid capacity to absorb it and the backup powerplants are essentially running out of fuel. So we need energy storage to replace backup. Probably the easiest way to do this would be to continue building wind turbines, onshore and offshore, and build end use thermal energy storage to absorb increasing proportions of the output of the RE. That means developing systems that allow a portion of grid demand to be controlled. If that demand is a multi-MW heat pump supplying a district heating network, that is easier to do than millions of household heat pumps and water heaters. So district heating with above ground or underground thermal energy storage, is one of the best energy storage strategies we could have. This is the sort of storage infrastructure that the UK should be investing in first. The UK is well suited to this kind of project, because most of our population lives in densely population towns in terrace houses, flats or semi-detached houses. Ground temperatures are a temperate 10°C year round. Simple systems that distribute warm water at 30°C could meet most of our space heating and half of our domestic water heating needs.

On a slightly longer timescale, pumped storage and CAES can both help smooth out peaks and troughs in RE generation. Eventually, thermal powerplants will only be needed for occasional lulls in generation capacity. We can replace those CCGTs with open cycle GTs burning some kind of storable liquid fuel. So there are ways forward that can work on a RE base for the UK at least. It just won't be very cheap energy when all of the costs are added up.

For places like Germany, Belgium and central European countries, wind resources are nowhere near as good. Those places really need nuclear reactors to meet their energy needs. It isn't optional for them. The UK seems to be incapable of successfully implimenting a nuclear power solution. How we can spend so many tens of billions of pounds building two uranium heated water boilers at Hinkley is beyond me. Lightwater reactors are quite simple and compact devices. The nuclear steam supply system isn't that much bigger than a house and is really just a collection of steel vessels. They should be cheap to build by this point. It should be possible to build a LWR powerplant in about 12 months for a cost of £1000/kWe. We are running at over 10 times that, both in cost and timescale. In a sane world in which we could actually build these things as well as we could in the 1970s, no one would bother building offshore wind turbines to supply their grid with expensive intermittent power. We have gone badly wrong somewhere along the line.

Last edited by Calliban (2024-09-27 07:46:44)

Calliban · 2024-09-27 17:30:37

This site provides graphs of average monthly sea water temperature for hundreds of locations around the UK coast.
https://seatemperatures.net/europe/united-kingdom/

In most locations south of Scotland, seawater temperature exceeds 15°C for at least a couple of months per year. In the south of England, temperatures exceed 17°C during summer and early autumn. This heat can be captured by pumping sea water through heat exchangers that transfer heat via water into boreholes 100+ metres deep. During winter, this heat can then be extracted and used as the heat source for multi-MW heat pumps, supplying district heat to entire towns.

Larger heat pumps have improved COP, as compression suffers fewer irreversibilities and can make use of steady flow axial compressors. Hydrocarbons like butane can also allow improved COP over a narrowly defined temperature range. Pressure ratios are lower and the dense fluid is easier to pump into evaporators. So town sized heat pumps, using stored solar heat can provide impressive COP. For a temperature rise of 20°C, from 13 to 33°C, a COP of 10 is realistic for large hydrocarbon based heat pumps supplying MWs of heat.

Warm water at 30°C could be stored in tanks. This would allow district heating systems to serve as a dump load for excess power within the grid. When grid power supply exceeds demand, the heat pumps are activated, filling the tanks. We could store days of heat in this way, which could then be released into the district heat network gradually.

Last edited by Calliban (2024-09-27 17:37:12)

Terraformer · 2024-09-28 07:37:24

Of course, if we have a heatpump available, and a seawater main, it might make a lot of sense to run it on solar power during sunny summer days... essentially we're using the surface of the sea as a vast free solar thermal collector, then concrentrating that heat some more to get a higher borehole temperature.

Quite a few coastal towns that would be good places to trial this, combining location by the sea with terraced streets and back alleys. A lot of them are also quite poor, so cheap heat will be perhaps more enticing. I think Lancaster are still talking about it at least.

tahanson43206 · 2024-09-28 07:50:32

For Terraformer ....

It will take leadership to bring about any of the interesting ideas that appear in the NewMars archive.

Leadership is not for the faint of heart, and it means taking significant personal risk. Not everyone is suited to play that role.

Calliban has suggested that thermal energy in sea water (from the nearby ocean) might be concentrated in vertical stores of some kind. If such an idea is practical it should have been tried somewhere.

Perhaps the economic conditions to give this idea some running room have not existed in the past, but perhaps there might be a combination of circumstances that would allow it today.

However, it will take leadership to move beyond theory to practice.

(th)

Calliban · 2024-10-01 04:54:43

I have done a bit more work on the design of a Carnforth district heating system. The system is intended to supply district heat to the entirety of the town, which includes approximately 8000 inhabitants living in some 3400 dwellings. Peak winter heat demand is estimated to be ~3kW per dwelling or 10MWth in total. Water will be distributed at 33°C, with water returning to the district heat plant at 21°C. This is sufficient to meet 100% of space heating needs and some 75% of domestic hot water heating requirements, with the remaining heat being provided by resistance heating. My assumption is that the system is active early September to the end of May, with the system recharging during the three months of summer.

I would like to thank the National Institute of Standards (NIST) for making fluid data freely available through online database.
https://webbook.nist.gov/chemistry/fluid/

My assumption is that the heat pump will be supplied with warm water at an average temperature of 15.5°C from deep boreholes located outside of town. Average sea temperature in Morcambe bay exceeds 15°C for 3.5 months of the year, reaching a high of 17.5°C towards the end of July.
https://seatemperatures.net/europe/unit … morecambe/

This heat can be used to reheat the boreholes during summer months. Temperatures could be further increased by passing the sea water through buried pipes beneath carparks or grazing land. My starting assumption is that borehole temperatures reach a low of 14°C at end of spring and a high of 17°C at end of summer.

The heat pump will use butane as working fluid. At 15°C, the saturation pressure of butane is 176.44KPa(a). This is the pressure at which butane boils when temperature is 15°C. At 33°C, the saturation pressure is 310.23KPa. Stored (geothermal) heat is used to boil butane within a boiler. A dryer sits atop the boiler. The dry vapour leaving the dryer, has temperature 15°C and a density of 4.5562kg/m3. The vapour enters the axial compressor, where its pressure increases to 310.23KPa; its temperature 33°C and density 7.78kg/m3. The compressed vapour flows out of the compressor into the condenser. This consists of a counterflow heat exchanger, which water enters at 21°C and leaves at 33°C.

Butane is well suited as the working fluid for this application. It has relatively low vapour pressure at both hot and cold temperatures applicable here. This has a number of important advantages.

1. The peak absolute system pressure is low at 3.1bar(a) or 2.09bar(g). The low pressure makes pressurised components easy to construct.

2. The fluid condenses at peak system temperature at a modest 3.1bar(a) pressure. This allows the return phase to use liquid condensate, which avoids energy losses associated with recompression of the fluid for injection into the heater.

3. The pressure difference between inlet and outlet of the compressor is small at 134KPa. This obviates the need for both extraction pump from the condenser and a feed pump for the boiler. The density of butane at 21°C, 3bar(a) is 577.53kg/m3. The pressure difference between the outlet of the boiler and outlet of the turbine is 134KPa, which corresponds to a head height of 23.2m liquid butane. If the top of the liquid level in the boiler is 23.2m above the liquid level in the condenser, the compressor back pressure will be sufficient to push condensed fluid into the riser tube entering the boiler. This eliminates two potentially costly components - condensate extraction pumps and feed pumps.

4. Finally, butane has high vapour density at the temperatures and pressures applicable to the compression cycle. This permits a relatively compact compressor per unit energy extracted.

A system diagram is shown below.

The work input from the compressor, is equal to the enthalpy at 2, minus enthalpy at 1.

W(in) = h2 - h1

The heat extracted from the condenser is equal to enthalpy at 2, minus enthalpy at 3.

Q(out) = h2 - h3

The ideal COP is given by:

COP(i) = Q(out)/W(in) = (h2 - h3)/(h2 - h1)
COP(i) = (632.4 - 249.91)/(632.4 - 606.74) =14.91

The reader will notice that the temperature of the return condensate in the condenser is 21°C, which is greater than the boiler heat exchanger (15°C). This means that condensate will start boiling before it enters the boiler and the fluid entering the boiler will be two-phase flow. This makes relatively little difference to COP, because the difference in enthalpy between liquid butane at 15°C (235.1KJ/kg) and 21°C (249.91KJ/kg) is small. However, if the return water from the town were used to heat greenhouses, say, to 15°C, then the overall COP will be slightly higher (ideal COP 15.48)and the greenhouse heat would be cheap.

The actual COP will be reduced by a number of parasitic energy losses.

1. The electric motor efficiency n_em. For a large squirrel cage motor operating at close to full load, this value can be taken to be 97%.

2. The axial compressor efficiency (n_c) will depend upon friction in bearings and drag and vortex shedding at the blade tips. I am going to assume that the compressor is multi-staged with a relatively small 1.05 pressure ratio across each stage. This reduces vorticity at the blade tips. The top end of isentropic efficiency for an axial compressor is 95%. A total 12 stages are needed to achieve a 1.34 bar pressure rise. Another important reason to keep pressure ratio across each stage as low as possible is the relative wetness of the vapour being compressed, despite the use of a dryer. A low pressure ratio allows for a reduced tip speed, extending the life of the blades.

3. The butane flows through pipes and a number of obstacles introduce pressure drops within the system. Of these, the vapour dryer dominates as the fluid must be forced through swirl vanes to seperate suspended liquid droplets. I am going to assume that turbine work is 1% greater than ideal to account for this loss. Friction in the liquid parts of the system is negligible as flow velocity is small. So n_dp is 99%.

4. I am making no assumptions at present about the energy cost of pumping the water around the town. Water flow must have sufficient head pressure to overcome friction and the account for changes in elevation.

Accounting for the system inefficiencies, the overall system COP can be calculated:

Real COP = (14.91 > 15.48) x 0.97 x 0.95 x 0.99 = 13.60 > 14.13

For a nominal system peak heat demand of 10MW, we would need 735kWe motor to drive the compressor at an inlet temperature of 15.5°C. However towards the end of spring when borehole temperature drops to 14°C, the difference in pressure across the compressor will be greater, requuring more power. Additionally, we have spoken about using the district heating system to absorb intermittent energy from the grid, with heat stored in phase change material. For this to be achieved, the system must be oversized, producing more heat during its operational periods in order to maintain an average 10MW heat supply.

This system could be replicated wherever we have a relatively densely populated urban area that needs heating. But every location is unique and the system would be modified to account for local conditions. In the North of Scotland, summer time sea temperatures barely exceed 14°C, which will reduce effective COP. Some localities may benefit from supplemental heat from industry or shallow geothermal resources. Nuclear powerplants produce thousands of MW of waste heat at a temperature of 30°C. This could heat entire cities, with only modest a modest temperature rise required by a heat pump. Inland locations with lack access to the thermal energy of seawater. In these places, capital costs will be higher as investment must be made in heat harvesting systems from the soil and paved areas.

Last edited by Calliban (2024-10-01 06:00:43)

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