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    Default Low powered stirling engines - what can they accomplish?

    Stirling engines are a closed cycle, can be operated by anyone capable of holding a flame, and works at lower pressures, necessitating that metallurgy be more concentrated on preventing horrible meltdowns and ensuring that there's a seal at all. Add to that a good source of things like a large forest or seams of coal near the surface.


    https://en.wikipedia.org/wiki/Stirli...ly_development

    So let's say a primitive civ obtains stirling engines. Mildly high pressure, made of brass/bronze/ iron, very few steel... what can they do with it? I know stirling engines can pump water, but just how much work can they do that would be useful for a civilization?

    A 2-horsepower (1.5 kW) engine, built in 1818 for pumping water at an Ayrshire quarry, continued to work for some time, until a careless attendant allowed the heater to become overheated.
    edit: Apologies for the lack in understanding. I mostly study biology and chemistry, and the last physics lessons I had was 7 years ago.
    Last edited by Accelerator; 2021-03-17 at 08:51 PM.

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    Default Re: Low powered stirling engines - what can they accomplish?

    The first thing that comes to mind is powering a lathe. Then use that lathe to make a better lathe. Use the better lathe to make better engines.

    After that, make whatever you want. :)
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    Default Re: Low powered stirling engines - what can they accomplish?

    Pumping water is about the most useful thing I can think of, to be honest. Specifically out of mines and such. Draining lakes/swamps. Typically if you want water pumped out of a river (for irrigation or normal water supply), you can use a waterwheel.

    Maybe if they managed to figure out the engineering to do so, they could also set up water supply in towns by pumping water out of the aquifer, essentially making an upgraded well.

    There's many things that could be done with stirling engines otherwise, but probably wouldn't be for the same reason a lot of things weren't automated until way later in history - human labor is cheaper and more flexible than setting up an expensive and maintenance-intensive machine. Like you could replace the stokers fueling a furnace, with a small stirling-engine mechanism that works off the heat of the furnace that is otherwise lost, driving a screw that feeds the furnace at a constant rate. But it wouldn't be as simple as just having people do it, it would still need regular maintenance (so more people, qualified technicians rather than the unskilled laborers that stokers could be), and it wouldn't actually create any improvement, you'd just replace people with a machine for no net benefit. Same with operating a forge bellows, etc.

    Stirling engines, if they appeared early enough and proven themselves well enough, could coexist very well with steam engines - they have the distinct advantage of not needing a water supply (except as coolant), and don't have the same "exploding boiler" danger, so smaller, lighter stirling-driven passenger trains - like small trams - could become a thing. Steam engines would still rise to prominence though, the sheer power they deliver was instrumental to the industrial revolution.

    A stirling engine could possibly be used to drive a sawmill or a grain mill, but I think you really don't want to have a furnace (required to power the stirling engine) anywhere near sawdust and flour. Windmills and waterwheels would be much safer for that.
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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by gomipile View Post
    The first thing that comes to mind is powering a lathe. Then use that lathe to make a better lathe. Use the better lathe to make better engines.

    After that, make whatever you want. :)
    A lathe is an entirely different sort of engineering challenge. "Powering" a primitive lathe can be done without any kind of engine, the problem is precision and material strength, for good bearings and useful cutting tools. A pottery wheel is basically a lathe already.
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    Default Re: Low powered stirling engines - what can they accomplish?

    Stirling engines are really only good at near-constant speed/power energy generation.

    So, for most purposes they will turn a shaft at one speed - and whilst you can gear up or down, you cannot increase the input speed or power very effectively. What this means is that you need applications where this is not a problem (and could be a benefit).

    Looking back across the middle ages and the early industrial revolution a huge amount of machinery began to be powered by waterwheels (and to a lesser extent windmills). Now water would probably still be better for these applications, but low-powered Stirling engines might be able to produce similar effects in really flat (or dry) areas where water power cannot be used. (Wind power might well be more reliable in such areas, but that doesn't mean that Stirling engines won't have a place - namely that of the constant energy supply given the ability to generate a heat differential.)

    One possible idea then, is a portable mill which is pulled around the farms at harvest time and used to mill the grain (possibly burning the waste straw from the harvest). If the time this would need is not practical, perhaps the tax/tithe portion is milled like this to make transporting it easier while the farmers keep grain to mill at the local mill through the year as needed.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Accelerator View Post
    So let's say a primitive civ obtains stirling engines. Mildly high pressure, made of brass/bronze/ iron, very few steel... what can they do with it? I know stirling engines can pump water, but just how much work can they do that would be useful for a civilization?
    Just about anything for which they need power, depending on whether the engineering to turn the engine power into usable power, plus the fuel cost, is less than the cost of powering it some other way (such as anything for which they did use windmills, waterwheels, draft animals, or those person-sized hamster wheels). Turn a mill wheel, make an automatic hammer for a blacksmith, pull stones up the wall of a being-constructed castle, plow a field (although in that case I would say you haven't invented the stirling engine, you've invented a stirling engine tractor, which I consider a second engineering marvel).

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Khedrac View Post
    One possible idea then, is a portable mill which is pulled around the farms at harvest time and used to mill the grain (possibly burning the waste straw from the harvest).
    There's no waste straw from the harvest. You'd use that as eg bedding for people/animals, roof-cladding, even food for animals at a pinch.

    In the era concerned it is probably easier to move the sacks of grain and flour than the machine to do it. Fact is you tend to only make flour as you need it keeping your grain in grain form as long as possible. It keeps better and you can plant it again. Your suggestion means you either keep going around with that contraption every week or something like that or take an awful big risk with your future.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by snowblizz View Post
    There's no waste straw from the harvest. You'd use that as eg bedding for people/animals, roof-cladding, even food for animals at a pinch.
    That depends on local conditions - I agree that there are plenty of uses for it, but a given location might not have some or most of them and end up with excess. If you have an area that is 90+% arable they will have excess straw for pretty much all purposes. Also, I know that wheat straw is very useful for other purposes, but how about other grains?

    Quote Originally Posted by snowblizz View Post
    In the era concerned it is probably easier to move the sacks of grain and flour than the machine to do it. Fact is you tend to only make flour as you need it keeping your grain in grain form as long as possible. It keeps better and you can plant it again. Your suggestion means you either keep going around with that contraption every week or something like that or take an awful big risk with your future.
    Read my suggestion again - the only part you use the engines for is the bit you are sending away not for your use. I agree it will keep better as grain, but there's less volume (and mass) to transport milled.

    I agree my suggested example wasn't a very good one, but it was designed to be an example to get people think about what can be done not what cannot. Stirling engines are limited in their uses, yes, but that doesn't mean that there is not a lot you can do with them.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Probably the most important impact it would have is actually running them backwards. A stirling engine driven by a water wheel (or another stirling engine, or even draught animals) is a heat pump, and that gives much earlier access to refrigeration. Reliable ice production would let food travel much further without spoiling. Cities could then be far larger.

    Cryogenics would be utilised much earlier and more often as well. Engines which use liquid air as a cold end can end up quite powerful, potentially giving an entirely different direction than the internal combustion engine. Ease of access of liquid oxygen might even make rockets be the first attempts at powered flight!

    They could basically do anything the early steam engines could do. That mostly means mining, but some agricultural work too*, and pumping canals. They could power mills, but mills don't have to move and can be established where water wheels are possible so probably wouldn't. Boats and locomotives could use them. Other than that, not a lot different.

    *As traction engines, rather than tractors. Steam plowing involved a plow pulled back and forth across the field by cable, while the 2 engines only moved between rows.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Adding to this:

    1. How difficult is it to make a working steam engine (with high pressure) compared to a Stirling engine?

    2. How difficult would it to make a Stirling Engine pull itself or transport itself?

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Khedrac View Post
    Also, I know that wheat straw is very useful for other purposes, but how about other grains?
    If they're fibrous in the right ways, you can break them down and create plant-based clothing, coverings and carrying bags.

    You can use them as binders.

    It all depends on the plant, really. Rice plants, for example, aren't the same composition as corn stalks.
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    Default Re: Low powered stirling engines - what can they accomplish?

    First of all, I would like to thanks for creating this thread on stirling engine. I was Looking for this previously but didn't find one. I would like to add new on this topic.

    I have heard that Stirling engines are not in wide use because they have a low power-weight ratio. Why is this? It would seem to me that the Beta type stirling engine (with 1 cylinder) would be very efficient because it only has like 3 major moving parts....flywheel crankshaft and piston and only one cylinder to wear out. I can't seem to find info about the total power output of the original stirling engine designed in the 1800s...anyone know this?

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by agustin1987 View Post
    First of all, I would like to thanks for creating this thread on stirling engine. I was Looking for this previously but didn't find one. I would like to add new on this topic.

    I have heard that Stirling engines are not in wide use because they have a low power-weight ratio. Why is this? It would seem to me that the Beta type stirling engine (with 1 cylinder) would be very efficient because it only has like 3 major moving parts....flywheel crankshaft and piston and only one cylinder to wear out. I can't seem to find info about the total power output of the original stirling engine designed in the 1800s...anyone know this?
    Well, yes. Stirling Engines kinda suck.

    Original stirling engine IIRc had 2 horsepower

    https://en.wikipedia.org/wiki/Stirling_engine

    1. They require radiators. In other words, they need ways to massively dump heat away, because the constant cooling and heating is a requirement. Heatbuildup would cause the entire engine to stall (and it's a closed system for the air). Thus, you need a radiator. A big, large radiator that makes the entire thing heavy as hell.

    2. No they're not efficient. In fact, they're noted to be inefficient. You can improve efficiency and power output by increasing pressure, temperate difference, etc.... but at the end of the day it's hit its goddamned limit. Very quickly outpaced by gasoline and conventional steam engines.

    Stirling has some advantages, though. They don't need superheated steam, making them far safer. Worse comes to worse it just melts down into slag, not explodes. And they run on temperature differentials. Inefficient, but hey, you can power these things with frackin' sunlight. Also, they act as heat pumps, letting you turn motion into ice and refrigeration.

    As for your question?

    Stirling came up with a first air engine in 1816.[8] The principle of the Stirling Air Engine differs from that of Sir George Cayley (1807), in which the air is forced through the furnace and exhausted, whereas in Stirling's engine the air works in a closed circuit. It was to it that the inventor devoted most of his attention.[citation needed]

    A 2-horsepower (1.5 kW) engine, built in 1818 for pumping water at an Ayrshire quarry, continued to work for some time, until a careless attendant allowed the heater to become overheated.
    I don't have enough understanding to check the veracity of the claim, but wikipedia says this.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by agustin1987 View Post
    I have heard that Stirling engines are not in wide use because they have a low power-weight ratio. Why is this?
    Because they simply aren't able to output a lot of power. They have low specific power. Or to make up an example to illustrate the point, if you want to drive the Titanic on Sterling engines you need an engine several times larger than the ship itself.

    Quote Originally Posted by agustin1987 View Post
    It would seem to me that the Beta type stirling engine (with 1 cylinder) would be very efficient because it only has like 3 major moving parts....flywheel crankshaft and piston and only one cylinder to wear out. I can't seem to find info about the total power output of the original stirling engine designed in the 1800s...anyone know this?
    Efficiency is about more than moving parts. It's about how much of the input energy you get out of it in workable output and usually at what size of a machine. And here Sterling engines clearly are outperformed, now, by most other types.

    https://en.wikipedia.org/wiki/Stirling_engine

    https://en.wikipedia.org/wiki/Engine...y#Steam_engine

    Quote Originally Posted by Accelerator View Post
    I don't have enough understanding to check the veracity of the claim, but wikipedia says this.
    The wiki page on steam engine efficiency notes it's very difficult to accurately gauge the efficiency of early steam machines due to insufficient data.
    Last edited by snowblizz; 2021-03-20 at 06:20 AM.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Accelerator View Post
    Well, yes. Stirling Engines kinda suck.

    1. They require radiators. In other words, they need ways to massively dump heat away, because the constant cooling and heating is a requirement. Heatbuildup would cause the entire engine to stall (and it's a closed system for the air). Thus, you need a radiator. A big, large radiator that makes the entire thing heavy as hell.
    Depends on what your cold sink is. On a boat or if you are pumping water it is actually really easy. The requirements are the same as for a closed cycle steam engine anyway. One of the weirder applications of stirling engines is putting them between a hot process and it's radiator, extracting energy from the differential. The weird part about it is that removing energy as useful work means it doesn't go into the cold side, meaning you need a smaller radiator.
    2. No they're not efficient. In fact, they're noted to be inefficient. You can improve efficiency and power output by increasing pressure, temperate difference, etc.... but at the end of the day it's hit its goddamned limit. Very quickly outpaced by gasoline and conventional steam engines.
    Well, those kind of suck too to be honest. Internal combustion engines at least have the potential for using higher fluid temperatures than your materials can cope with (external will be limited by heat exchanger limits), but running it through a heat engine at all loses you at least 40%. Fuel cells can access the energy directly not limited by thermodynamics in the same way.
    Quote Originally Posted by snowblizz View Post
    Because they simply aren't able to output a lot of power. They have low specific power. Or to make up an example to illustrate the point, if you want to drive the Titanic on Sterling engines you need an engine several times larger than the ship itself.
    This isn't really true. Practical efficiency is limited by the fact you repeatedly have to push gas through a regenerator, and this is quite lossy if you try to do it very quickly. You can get the same power more efficiently by building things bigger, but that doesn't mean they are not capable of high powers in small volumes. They are built as large as practical where they are built, which gives them this reputation for lower power to weight than is justified. Where they do find use is when you actively want a system that can operate efficiently at low power levels, such as a cruising submarine (though that is mostly for noise reasons).

    The biggest thing going for them is the ability to operate at low powers on a moderate heat difference over a wide variety of conditions. They are not going to fit in well with our fossil fuel based MOAR POWER mentality, but that is only really applicable on earth, and will not last long. Gas turbines will always beat them out when conditions are extreme and will be stable (A lava lake on Io, for example), but the vast majority of the universe is not like that. On a Martian colony, for example, they are not going to be able to manufacture solar panels for a long time, leaving low grade solar thermal being the only domestically produced energy supplies. You can run a stirling engine on hot and cold sand, potentially letting you exploit a huge area for solar power quite easily. Low efficiency doesn't matter if it scales cheaply, and piles of sand are both transportable and storable. Being able to harness even 1% of the energy absorbed by 1km2 of ground would give you megawatts of power.

    I suppose a civilisation that had access to large numbers of hot springs might develop stirling engines extensively. Burning things for them doesn't make much sense, but if low grade heat is available it might get commonly used. The difficulty is producing them if you don't have cheap coal available for metalworking. Unlikely, but possible.

    I take slight issue with saying they "suck", because it implies the only good engines are ones that run on burning chemicals, and we absolutely need to get away from that way of thinking. It screws with our environment and limits our thinking. Stirling engines are truly awesome, because they can run without burning stuff. If you are determined to burn something then they aren't for you, but for pretty much everything else you want a stirling engine. They are going to be around long after internal combustion engines are antiques.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Fat Rooster View Post

    The biggest thing going for them is the ability to operate at low powers on a moderate heat difference over a wide variety of conditions. They are not going to fit in well with our fossil fuel based MOAR POWER mentality, but that is only really applicable on earth, and will not last long. Gas turbines will always beat them out when conditions are extreme and will be stable (A lava lake on Io, for example), but the vast majority of the universe is not like that. On a Martian colony, for example, they are not going to be able to manufacture solar panels for a long time, leaving low grade solar thermal being the only domestically produced energy supplies. You can run a stirling engine on hot and cold sand, potentially letting you exploit a huge area for solar power quite easily. Low efficiency doesn't matter if it scales cheaply, and piles of sand are both transportable and storable. Being able to harness even 1% of the energy absorbed by 1km2 of ground would give you megawatts of power.
    A 1km2 installation of solar panels will be way more efficient than this. The Solar panels will start generating as soon as the sun is up while your plan would have to wait until the sun warms the sand enough to get going. Mars is also very cold so I am not sure the sun ever warms the sand enough for this to work.

    Plus, Solar Panels have no moving parts so that greatly reduces maintenance costs. Remember that any kind of maintenance requires a person in a space suit so a system based on lots of moving parts is inherently dangerous.

    I don't think that building solar panels on Mars will be any more difficult than building Sterling engines. In fact, I think solar panels will be way easier to build and install. To get the most out of a Sterling Engine you need gases like Helium and a lot of exotic materials.


    I take slight issue with saying they "suck", because it implies the only good engines are ones that run on burning chemicals, and we absolutely need to get away from that way of thinking. It screws with our environment and limits our thinking. Stirling engines are truly awesome, because they can run without burning stuff. If you are determined to burn something then they aren't for you, but for pretty much everything else you want a stirling engine. They are going to be around long after internal combustion engines are antiques.
    Sterling Engines at a small temperature differential suck at generating electricity due to their low power density. Lots of alternative power sources out perform them. Hydrogen fuel cells, wind turbines, solar, tidal, etc. If there is a high temperature differential, a triple expansion steam system will out perform a Sterling.
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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Trafalgar View Post
    Sterling Engines at a small temperature differential suck at generating electricity due to their low power density. Lots of alternative power sources out perform them. Hydrogen fuel cells, wind turbines, solar, tidal, etc. If there is a high temperature differential, a triple expansion steam system will out perform a Sterling.
    Curiously, Stirling engines were considered as a replacement for typical RTGs on spacecraft, specifically because with an advanced design they could outperform a traditional RTG for the same size and mass, and offer same performance with just a quarter of the radioactive material amount. The project stalled because... well, because it's NASA, and it has far less money than it has things to spend it on.

    Also very pertinent to space, and in contrast to any other power source, Stirling engines will work with a negative temperature differential just as well. If you're sitting on some dark rock where the sun don't shine, using the cold outside to drive a Stirling generator can give you some power for the heat lost. Same applies to some locations on Earth, where temperatures are far below freezing for the whole year, and just the fuel you expend to heat your living space to tolerable levels will give you enough power to also have light and communications, with no need to separately fuel a generator.
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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Trafalgar View Post
    A 1km2 installation of solar panels will be way more efficient than this. The Solar panels will start generating as soon as the sun is up while your plan would have to wait until the sun warms the sand enough to get going. Mars is also very cold so I am not sure the sun ever warms the sand enough for this to work.
    If you have 1km2 of solar panels (and the requisite cables to transfer that much power those sort of distances) then yes, obviously. The concept is not designed to be space efficient, it is designed to be simple and require no advanced industry. If you have ever been to a beach near the equator you would know that the top layer of sand gets extremely hot extremely fast. Skim that off to expose the next and it will also heat up fast. Mars also has very little atmosphere, so at night the sand gets extremely cold. The system is doing useful work at all times.

    As for solar panels generating as soon as the sun comes up, they also stop generating as soon as the sun goes down. They need to have a separate energy storage solution to function well. Collecting hot sand during the day, and cold sand during the night gives you two piles of sand that the temperature differential of can give you energy all the time. Somewhere like the moon things are even worse. There you would require 14 days of energy storage if you relied on panels. With a regolith system you just end up with much bigger piles.
    Plus, Solar Panels have no moving parts so that greatly reduces maintenance costs. Remember that any kind of maintenance requires a person in a space suit so a system based on lots of moving parts is inherently dangerous.
    Small rover drones can go to the maintainer, meaning the majority of the maintenance can be performed in a pressurised hanger. Colony construction would require a lot of EVA activity anyway, so I wouldn't be worried about it. Mechanical heavy setups are good when only primitive industry is available, because it can do mechanical. Semiconductors are much harder. While cheaper on earth, without the industry backing it up electronic components are vastly more expensive.
    I don't think that building solar panels on Mars will be any more difficult than building Sterling engines. In fact, I think solar panels will be way easier to build and install. To get the most out of a Sterling Engine you need gases like Helium and a lot of exotic materials.
    Do you have a basis for that assertion? A stirling engine is literally pipes and pistons. It requires nothing exotic, and hydrogen works great as a working fluid (not exactly rare, and not dangerous in an inert atmosphere). We don't need to get the most out of it, we just need it to work. Mechanical parts can be manufactured locally out of whatever material is easiest. Any viable colony would need a workshop of some description. Meanwhile solar panels need high purity silicon, and that is extremely hard to produce and very specialised. A Martian colony would be entirely dependent on earth manufactured solar panels for energy until they set that up. I'm not saying it is easy, just that early dependence on solar panels will put a hard bottleneck on colony growth, and any solution that avoids it is better.
    Sterling Engines at a small temperature differential suck at generating electricity due to their low power density. Lots of alternative power sources out perform them. Hydrogen fuel cells, wind turbines, solar, tidal, etc. If there is a high temperature differential, a triple expansion steam system will out perform a Sterling.
    There is almost 100K temperature difference between day and night on Mars, more than enough to get good performance. Hydrogen fuel cells work great if you have hydrogen lying around, wind works great if there is wind, tidal works great if there is an ocean, solar works great if you can produce it, as well as the storage required for it. None of these work to supply energy to a starting out colony.

    I think you are underestimating the difficulty of getting power without fossil fuels or a fully fledged semiconductor industry. What I am suggesting is vastly inefficient, but if you cover enough ground you end up with useful quantities of energy anyway, and covering a lot of ground is quite easy. There is literally nothing else to do with the land. You are not going to be covering it all in solar panels any time soon. You might as well farm sand, inefficient as it is.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by snowblizz View Post
    The wiki page on steam engine efficiency notes it's very difficult to accurately gauge the efficiency of early steam machines due to insufficient data.
    Early steam engines:

    Archimedes' toy. Almost 0% efficiency. A great proof of concept, but nobody who knew about it was interested in building steam engines. Steam engines happen when it is steam engine time, that is to say you have the infrastructure for steam engines (which is kind of the point of the question).

    Savory engine: I'd claim that Savory invented vaporware, not a steam engine. *Maybe* possible to construct, but the efficiency couldn't have been there (don't forget all the coal needed to forge the parts to make it before it explodes).

    Newcomen engine: had enough efficiency to be worth feeding coal into, that's pretty much proven. On the other hand it was bound to grind to a halt and require cooling before restarting, so your efficiency depends on size (the bigger the better) and downtime (how long and often you let it cool).

    Watt engine: solves the "grind to a halt" problem of the Newcomen engine, also redesigned to do more than pump water. I'd strongly suspect that Watt cared more about power output than efficiency, and that the coal was still pretty close to the surface in Newcastle, meaning his customers similarly didn't care about efficiency. That probably wouldn't come until steamships could deliver much more coal with greater efficiency.

    Early need for such engines: you'd have to make your engine outperform a watermill, otherwise you'd simply keep building watermills until you ran out of lumber. Yes, lumber not rivers. England was building watermills increasingly from before the Conquest (they are mentioned in the Domesday book) to the black plague. Industrialization nearly ground to a halt, but the trees were able to recover due to lack of harvesting during the black plague. Watermill construction resumed, and eventually there was a strong market for non-water engines. Unfortunately, I doubt a sterling engine was powerful enough for a "waterlessmill".

    PS: the information for that last paragraph came from a book "The Medieval Industrial Revolution". Unfortunately, I lost that book (not a common practice, I assure you). I remember reading other works about how milling grain was "women's work" (apparently hated by anyone stuck doing it) and realized just how many resources were spent automating "women's work" that it seemed to break a lot of assumptions I had. But I just couldn't find the book to check.

    Quote Originally Posted by Fat Rooster View Post
    Do you have a basis for that assertion? A stirling engine is literally pipes and pistons. It requires nothing exotic, and hydrogen works great as a working fluid (not exactly rare, and not dangerous in an inert atmosphere). We don't need to get the most out of it, we just need it to work. Mechanical parts can be manufactured locally out of whatever material is easiest. Any viable colony would need a workshop of some description. Meanwhile solar panels need high purity silicon, and that is extremely hard to produce and very specialised. A Martian colony would be entirely dependent on earth manufactured solar panels for energy until they set that up. I'm not saying it is easy, just that early dependence on solar panels will put a hard bottleneck on colony growth, and any solution that avoids it is better.
    This still seems like an excuse to use a sterling engine. While Mars has "sandstorms", the martian atmosphere is so thin as those are unlikely to be anything like an Earth sandstorm. So I'd assume that you could simply stretch a mylar reflector as far as you want and concentrate the sunlight so you can use a turbine instead of a sterling engine. Why use such an inefficient and low power engine anyway?
    Last edited by wumpus; 2021-03-20 at 03:31 PM. Reason: commenting on Fat Rooster's assertion

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Fat Rooster View Post
    If you have 1km2 of solar panels (and the requisite cables to transfer that much power those sort of distances) then yes, obviously. The concept is not designed to be space efficient, it is designed to be simple and require no advanced industry. If you have ever been to a beach near the equator you would know that the top layer of sand gets extremely hot extremely fast. Skim that off to expose the next and it will also heat up fast. Mars also has very little atmosphere, so at night the sand gets extremely cold. The system is doing useful work at all times.

    As for solar panels generating as soon as the sun comes up, they also stop generating as soon as the sun goes down. They need to have a separate energy storage solution to function well. Collecting hot sand during the day, and cold sand during the night gives you two piles of sand that the temperature differential of can give you energy all the time. Somewhere like the moon things are even worse. There you would require 14 days of energy storage if you relied on panels. With a regolith system you just end up with much bigger piles.
    So you are are talking about collecting 1km2 of hot sand during the day and 1km2 of cold sand at night. I don't work construction but you are talking about using bulldozers... lots of bulldozers running all day all night. I don't know why you think this won't require advanced industry. I imagine some kind of robotic bulldozer designed to collect tons of sand on Mars would require lots of advanced industry. Plus, the amount of energy expended would sure cut into anything being produced.

    Sure, solar panels don't work at night. But batteries do. And the advantage of Solar Panels is that, they require so little maintenance after you install them. Just blow the dust off periodically. Since land is not at a premium on Mars, you can just keep adding more panels as needed.

    Small rover drones can go to the maintainer, meaning the majority of the maintenance can be performed in a pressurised hanger. Colony construction would require a lot of EVA activity anyway, so I wouldn't be worried about it. Mechanical heavy setups are good when only primitive industry is available, because it can do mechanical. Semiconductors are much harder. While cheaper on earth, without the industry backing it up electronic components are vastly more expensive.
    Small rover drones, EVA suits, pressurized hangers all require advanced industry. Mechanical Heavy setups that can work on Mars require advanced industry.

    Do you have a basis for that assertion? A stirling engine is literally pipes and pistons. It requires nothing exotic, and hydrogen works great as a working fluid (not exactly rare, and not dangerous in an inert atmosphere). We don't need to get the most out of it, we just need it to work. Mechanical parts can be manufactured locally out of whatever material is easiest. Any viable colony would need a workshop of some description. Meanwhile solar panels need high purity silicon, and that is extremely hard to produce and very specialised.
    Hydrogen is rare on Mars. You could get it through the electrolysis of water ice deposits. And the easiest source of power for that electrolysis is a solar panel...

    I also imagine that any colonist could find a better use for those water ice deposits than making hydrogen for a stirling.

    Pipes and pistons require iron or aluminum which must be mined, smelted, forged, cast, etc before it is usable. Iron and Aluminum is common on Mars but so is Silicon.

    You are also talking about gas tight pipes and pistons. You are talking about bearings to reduce friction. You are talking about things like O rings, gaskets, lubricants, etc and all built without a petroleum industry. Nothing easy about any of that.

    A Martian colony would be entirely dependent on earth manufactured solar panels for energy until they set that up. I'm not saying it is easy, just that early dependence on solar panels will put a hard bottleneck on colony growth, and any solution that avoids it is better.
    ANY Mars Colony is going to be completely dependent on Earth. I don't see how anything your describing changes that.
    Last edited by Trafalgar; 2021-03-20 at 03:39 PM.
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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Trafalgar View Post
    So you are are talking about collecting 1km2 of hot sand during the day and 1km2 of cold sand at night. I don't work construction but you are talking about using bulldozers... lots of bulldozers running all day all night. I don't know why you think this won't require advanced industry. I imagine some kind of robotic bulldozer designed to collect tons of sand on Mars would require lots of advanced industry. Plus, the amount of energy expended would sure cut into anything being produced.
    More like a miniature combine harvester, but I'm glad you brought up bulldozers. Lets say you got your wish and a solar panel factory was built. It would need material, which would also require bulldozers. No matter what industry develops they are going to need heavy equipment production. You don't need a solar panel factory instead of a machine shop, you need it in addition.

    Also, those numbers are in the megawatt range. Enough for thousands of people, or significant industry. Yes it ends up quite impressive at that scale, and requires considerable maintenance. For comparison you would need ~250 tons of solar panels, (plus cabling, fixings, etc), plus batteries. You could send actual combine harvesters at that point and still have a weight saving.
    Sure, solar panels don't work at night. But batteries do. And the advantage of Solar Panels is that, they require so little maintenance after you install them. Just blow the dust off periodically. Since land is not at a premium on Mars, you can just keep adding more panels as needed.



    Small rover drones, EVA suits, pressurized hangers all require advanced industry. Mechanical Heavy setups that can work on Mars require advanced industry.
    They require heavy industry, not advanced, and the precisions required are easily achieved.
    Hydrogen is rare on Mars. You could get it through the electrolysis of water ice deposits. And the easiest source of power for that electrolysis is a solar panel...

    I also imagine that any colonist could find a better use for those water ice deposits than making hydrogen for a stirling.
    Rare but not unavailable, and required in quantity for any colony anyway, never mind the fact that most proposals require enough to manufacture rocket fuel from. The amount required for a stirling engine barely even registers, and is not consumed. On top of that, all hydrogen does is boost efficiency, it is not actually required to make it work. It works just fine with any gas.
    Pipes and pistons require iron or aluminum which must be mined, smelted, forged, cast, etc before it is usable. Iron and Aluminum is common on Mars but so is Silicon.

    You are also talking about gas tight pipes and pistons. You are talking about bearings to reduce friction. You are talking about things like O rings, gaskets, lubricants, etc and all built without a petroleum industry. Nothing easy about any of that.
    If a colony can feed itself it can produce plant based lubricants, and the chemistry involved in producing many basic polymers is quite simple. It can be done very little equipment, none of which is specialised. Any methane based return system requires a basic chemical setup anyway. The important point is basic. There are people on youtube of have set up systems more than capable in their back yard. 99% purities is fine for everything in that list, but you need at least 3 more 9s in order to make any semiconductor stuff work.
    ANY Mars Colony is going to be completely dependent on Earth. I don't see how anything your describing changes that.
    This is where we fundamentally disagree. I see no unsurmountable problems with a Martian colony, and if it is entirely dependent on Earth I would call it an outpost, not a colony. It will import microprocessors for a very long time, but everything else is either not needed or can be manufactured locally to be good enough. A machine shop capable of producing pressure vessels and moving parts is absolutely required for a growing colony, so is a given. A basic chemistry setup, and plant production on a scale that can feed people are also required. The same equipment that can produce methane for rocket fuel can also produce polymers, so that stuff is basically free.

    By far the largest hurdle is energy production, and it is the only one relevant to this thread. Of the list of things that you produced that were 'better' than stirling engines, none work except solar, and photovoltaics cannot be produced locally by a minimal setup. That basically leaves solar thermal. High grade concentrated solar thermal is possible, but requires even more moving parts and still requires energy storage. Direct heating/cooling of a working medium is very inefficient, but if you use sand as your working medium you have limitless supplies with no processing. Sure, pretty much anything else works 'better', but the scale and simplicity of the system beats any other I have seen.

    Edit: Almost forgot, how do you deal with cooling if you are using solar panels? It becomes a substantial problem if you are operating in the megawatt range, and runs into intermittency issues without some thermal storage solution (only the opposite of your solar panels. You either have energy, or good cooling, never both). Building radiators isn't hard (in comparison to the other problems), but it is another piece of infrastucture that solar requires that cannot be ignored. Thermal sand is a solution for energy production, storage, and cooling.
    Last edited by Fat Rooster; 2021-03-21 at 12:29 PM.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Where are you getting hot sand from on Mars? Mars is cold.
    Would cold sand and colder sand work for your magic stirling engines?
    Last edited by GeoffWatson; 2021-03-30 at 03:50 PM.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by GeoffWatson View Post
    Where are you getting hot sand from on Mars? Mars is cold.
    Would cold sand and colder sand work for your magic stirling engines?
    Fat Rooster said from "low grade solar thermal" upthread.

    I assume they meant something like nonimaging concentrators. Such as mirrored troughs which concentrate sunlight to a strip in the base of the trough.
    Quote Originally Posted by Harnel View Post
    where is the atropal? and does it have a listed LA?

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by wumpus View Post
    PS: the information for that last paragraph came from a book "The Medieval Industrial Revolution". Unfortunately, I lost that book (not a common practice, I assure you). I remember reading other works about how milling grain was "women's work" (apparently hated by anyone stuck doing it) and realized just how many resources were spent automating "women's work" that it seemed to break a lot of assumptions I had.
    I wouldn't underestimate the importace of women as a group throughout history. Nor the importace of their labor. IMO women have always been a shaping society as a treasured group and as teachers for the young generations. As workers, their labor isn't really less valuable than a mans.
    The power of automation is immense. I heared in some talk that the singlemost revolutionary invention was the washing machine, freeing more hours of (female) labor than any other invention.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by wumpus View Post
    PS: the information for that last paragraph came from a book "The Medieval Industrial Revolution". Unfortunately, I lost that book (not a common practice, I assure you). I remember reading other works about how milling grain was "women's work" (apparently hated by anyone stuck doing it) and realized just how many resources were spent automating "women's work" that it seemed to break a lot of assumptions I had. But I just couldn't find the book to check.
    Can't find a book by that title, do you mean "The Medieval Machine: The Industrial Revolution of the Middle Ages" by Jean Gimpel? I think it a great book, but the copy I read is my brother's.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Rydiro View Post
    I wouldn't underestimate the importace of women as a group throughout history. Nor the importace of their labor. IMO women have always been a shaping society as a treasured group and as teachers for the young generations. As workers, their labor isn't really less valuable than a mans.
    The power of automation is immense. I heared in some talk that the singlemost revolutionary invention was the washing machine, freeing more hours of (female) labor than any other invention.
    I wasn't underestimating women's labor. I was surprised that the medieval powers that were wouldn't underestimate them (probably including the female gentry).

    Quote Originally Posted by Khedrac View Post
    Can't find a book by that title, do you mean "The Medieval Machine: The Industrial Revolution of the Middle Ages" by Jean Gimpel? I think it a great book, but the copy I read is my brother's.
    Could be. A quick image search couldn't match any covers, so it may be that what I read is lost to history.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Rydiro View Post
    I wouldn't underestimate the importace of women as a group throughout history. Nor the importace of their labor. IMO women have always been a shaping society as a treasured group and as teachers for the young generations. As workers, their labor isn't really less valuable than a mans.
    The power of automation is immense. I heared in some talk that the singlemost revolutionary invention was the washing machine, freeing more hours of (female) labor than any other invention.
    The only thing I can think of competing with it would be the tractor and artificial fertilization. In the 1800s, approximately 90% of the population lived on farms because of the vast need for human labor on them. Today, it's around 1%.

    Of course, this supports your point that the power of automation is truly immense.

    If you're going for a remote colony, automation basically makes it possible. There's simply a great deal of work that needs doing, and the more of that you can automate and power, well, the more viable it gets. I'm not sure if a colony today would be fully independent, but the more automation we can offer them, the better we are likely to do.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by wumpus View Post
    I remember reading other works about how milling grain was "women's work" (apparently hated by anyone stuck doing it) and realized just how many resources were spent automating "women's work" that it seemed to break a lot of assumptions I had.
    So much so that milling was normally considered slave's work. Hard, monotonous and neverending. In iron age Scandinavia this was one of the first things your thrall's ended up doing if you had any.

    We shouldn't forget that work is work. If you can automate some away, well your women are now more able to do more valuable work, like e.g. spinning and weaving.

    The pre-industrial age never had a shortage of work so any automation would usually end up a net benefit whether it was men, women or slaves tasks. Especially if it meant you didn't have to pay anyone. It also was the case that work was often considered beneath people. It's why the earliest stratification was between those who pray, those who fight and those who work. Effectively effort made you less holy. On the other hand some did see labour as essentially holy. You could do "god's work" quite literally.

    It's no surprise monasteries were big proponents of e.g. watermills. They needed less lay staff to work for them. They could make money allowing (forcing, surprisingly common) people to use the mill. And they had the economic means to invest in a mill and could expect to be benefiting from one for years to come.
    Last edited by snowblizz; 2021-04-14 at 05:04 PM.

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by snowblizz View Post
    The pre-industrial age never had a shortage of work so any automation would usually end up a net benefit whether it was men, women or slaves tasks.
    This depends on the culture. I have heard that in some pre-industrial cultures they actively supressed innovation to avoid freeing up the populace (which might lead to things like social unrest).

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    Default Re: Low powered stirling engines - what can they accomplish?

    Quote Originally Posted by Khedrac View Post
    This depends on the culture. I have heard that in some pre-industrial cultures they actively supressed innovation to avoid freeing up the populace (which might lead to things like social unrest).
    There are always those who resist change, sure. I'm not sure that it's specific to any one culture, but generally speaking, inventions that greatly reduce work tend to catch on regardless. Even if only a few adopt them initially, they tend to be fairly successful, and then they get copied a lot. If it means maybe being rich, well, lots of people will reconsider their views on stuff.

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