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#26 2023-03-22 19:06:46

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,483

Re: Permenance Movement

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)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#27 2023-03-23 19:56:31

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,044

Re: Permenance Movement

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

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#28 2023-04-03 13:37:47

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,483

Re: Permenance Movement

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.


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#29 2023-12-01 13:33:22

Mars_B4_Moon
Member
Registered: 2006-03-23
Posts: 9,501

Re: Permenance Movement

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

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#30 2023-12-13 10:42:42

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,483

Re: Permenance Movement

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)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#31 2024-03-30 14:59:55

Mars_B4_Moon
Member
Registered: 2006-03-23
Posts: 9,501

Re: Permenance Movement

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

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

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#32 2024-03-30 15:17:00

Terraformer
Member
From: Ceres
Registered: 2007-08-27
Posts: 3,821
Website

Re: Permenance Movement

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...


"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony

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#33 2024-03-30 20:41:33

kbd512
Administrator
Registered: 2015-01-02
Posts: 7,468

Re: Permenance Movement

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

diagram.jpg

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.

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#34 2024-03-31 15:59:12

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,483

Re: Permenance Movement

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)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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