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#1 2018-05-31 08:25:48

louis
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From: UK
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CO2 Sublimation Heat Engine

I meant to return to this subject, as it does seem very important.  It seems that we do have a readily energy source available on Mars:

https://www.extremetech.com/extreme/200 … tion-maybe

A CO2 Sublimation Heat Engine (SHE).  It appears a SHE could be used to power electricity generation turbines on Mars and even rockets to return to Earth.

Do people think this will work? 

I can't see many drawbacks...are there any?

What do we need to do to prove this technology?

How would it be deployed on Mars?


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#2 2018-05-31 19:54:58

SpaceNut
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Re: CO2 Sublimation Heat Engine

We have talked about this as an energy source in the past making use of the mars cycles on supercold during the night to freeze out co2 for making fuel via heating in a chamber via solar energy to allow it to expand to gaseous state.
Supplemental energy supplied to either enhance production of co2 or to cause a higher level of expansion.
Generator would as the image shows a fan/ prop system to turn the shaft of the generator as it changes states.

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#3 2018-06-01 05:56:15

louis
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Re: CO2 Sublimation Heat Engine

Yes, it's definitely been touched on before. I think it's very exciting because essentially it means we have a virtually limitless alternative energy source available on Mars. It could be especially useful during major dust storms when solar power might dip. 

I am not sure about the energy return if you apply say PV solar power to the CO2 to heat it up...would you still get a significant energy gain?  Presumably using natural heating by the sun  (possibly boosted by solar reflectors) would, I am guessing, limit energy more to sollight hours, although I can imagine that the gas might remain gaseous if you had some arrangement for insulation after sollight hours.

I think this certainly needs looking into some more.

Perhaps CO2 SHEs could be integrated into farm habs, so that release of the CO2 gas is useful,not a waste product.

There are many angles to this which need to be investigated. CO2 SHEs might also drive surface vehicles like rovers.

SpaceNut wrote:

We have talked about this as an energy source in the past making use of the mars cycles on supercold during the night to freeze out co2 for making fuel via heating in a chamber via solar energy to allow it to expand to gaseous state.
Supplemental energy supplied to either enhance production of co2 or to cause a higher level of expansion.
Generator would as the image shows a fan/ prop system to turn the shaft of the generator as it changes states.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#4 2018-06-01 14:14:54

louis
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Re: CO2 Sublimation Heat Engine

https://www.nature.com/articles/ncomms7390

From the above paper:

"...it has been recently suggested that, for deep space applications, locally available resources (ices of H2O, CO2 and CH4) on the surfaces of planetary bodies could be sources for use in sublimation9. The abundance of such resources is highlighted by recent reports of ‘linear gullies on Mars’ carved by slabs of solid CO2 sliding down inclines. Such a process is thought to occur as a consequence of seasonal variations in the environmental temperature, which drive the sublimation of dry-ice deposits10. This highlights that low pressures and high temperature differences naturally occurring in exotic environments could make energy harvesting and power generation based on alternative heat cycles, and using locally available ices, feasible."

A useful diagram:

https://www.nature.com/articles/ncomms7390/figures/1

It seems like they are heating the turbine to quite a high temperature...not sure how that relates to situation on Mars.


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#5 2018-06-01 16:31:04

louis
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Re: CO2 Sublimation Heat Engine

https://theconversation.com/how-energy- … mars-38250

More of an article for the lay person in the above link.

Perhaps I am being a bit slow but why do they have to resort to the Leidenfrost effect?

Why can't you (on Mars) just put a load of CO2 dry ice in a boiler, and then warm it up a few degrees to get the pressure release that will (as with a steam engine on Earth) drive a conventional turbine?


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#6 2018-06-01 22:03:36

SpaceNut
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Re: CO2 Sublimation Heat Engine

Yes solar thermal energy concentrated on the Dry Ice location in the chamber which is used to go rapid through the phase change of the triple point to get the most energy from near zero power input.

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

http://www.aidic.it/cet/13/32/089.pdf

https://www.eng.ed.ac.uk/about/news/201 … -life-mars

https://phys.org/news/2015-03-breakthro … -life.html

https://newatlas.com/carbon-dioxide-eng … ars/36443/

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#7 2018-06-02 04:53:45

louis
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Re: CO2 Sublimation Heat Engine

Thanks SpaceNut...I am still mystified why harnessing the Leidenfrost effect is better than simply heating CO2 ice in a boiler. That last article seems confused on the subject, saying the Leidenfrost engine doesn't "burn" any fuel to capture the energy. Well you don't have to "burn" any fuel in CO2 boiler do you? -  no more than you "burn" water in a steam engine. You simply have to heat the CO2 (or the water in the case of a steam engine). How the heating is done is not especially relevant in principle. You can certainly used direct solar radiation either in its natural form or concentrated.

I think I am right in saying that CO2 sublimates at or above -53 degress celsius on Mars. So on the face of it , all you need to do is have a boiler system where CO2 ice is heated above that point. I am imagining something like  CO2 dry ice store that is kept out of the sun that is then fed into a boiler placed in the open which could be heated by solar reflectors, to then create vapour within the boiler which can be used to drive a turbine. With a condenser system, I presume you wouldn't need to replenish the CO2 much. This seems to fit in quite nicely with the sol-night cycle.

The Leidenfrost machine by contrast seems to require much more intense heating of the turbine...

SpaceNut wrote:

Yes solar thermal energy concentrated on the Dry Ice location in the chamber which is used to go rapid through the phase change of the triple point to get the most energy from near zero power input.

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

http://www.aidic.it/cet/13/32/089.pdf

https://www.eng.ed.ac.uk/about/news/201 … -life-mars

https://phys.org/news/2015-03-breakthro … -life.html

https://newatlas.com/carbon-dioxide-eng … ars/36443/


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#8 2018-06-02 09:39:33

SpaceNut
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Re: CO2 Sublimation Heat Engine

To get a prop or fan blades to turn you need a force to which in a chimney or boiler chamber is caused by expansion from solid to gaseous.

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#9 2018-06-03 03:59:26

elderflower
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Re: CO2 Sublimation Heat Engine

This will run intermittently if fed with solid CO2. For continuous operation the working fluid needs to be a liquid  ( or at least a slurry) so that it can be pumped continuously into the phase change device, which we might call a boiler. Alternatively one could cycle three chambers between atmospheric pressure when they would be charged, heating phase where the pressure would rise to working pressure and discharge to the turbine inlet. Then they would need to be vented back to atmospheric pressure.
By using an open cycle, where the working fluid is dumped to atmosphere you are reproducing the cycle used by steam locomotives on Earth. The locomotive cycle uses a little of the remaining energy in the working fluid to enhance the draft through the boiler as it is vented from the Low Pressure cylinder, but Mars boilers will not need this.
On Mars, due to the extremely low atmospheric pressure the expansion ratio between High pressure and exhaust will be much greater than applies on earth. Reciprocating engines are not going to be able to provide this expansion and turbines will have to be used, even for traction equipment.
The fluid will need to be reheated between stages, as is done in Earth power stations, but here it is done for thermodynamic reasons. On Mars there is a more important reason. Expanding cool CO2 will turn some of it's mass back into solid particles which will rapidly erode turbine nozzles and blades.

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#10 2018-06-03 17:13:31

louis
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Re: CO2 Sublimation Heat Engine

Perhaps the presumed advantage of the Leidenfrost engine is the lack of friction then? I still don't understand why it's better than a conventional boiler set up...and I am not sure you would be entirely right about having to have a fluid - couldn't you crush CO2 ice like we crush ice for drinks and continuously feed it in as crushed pieces?

elderflower wrote:

This will run intermittently if fed with solid CO2. For continuous operation the working fluid needs to be a liquid  ( or at least a slurry) so that it can be pumped continuously into the phase change device, which we might call a boiler. Alternatively one could cycle three chambers between atmospheric pressure when they would be charged, heating phase where the pressure would rise to working pressure and discharge to the turbine inlet. Then they would need to be vented back to atmospheric pressure.
By using an open cycle, where the working fluid is dumped to atmosphere you are reproducing the cycle used by steam locomotives on Earth. The locomotive cycle uses a little of the remaining energy in the working fluid to enhance the draft through the boiler as it is vented from the Low Pressure cylinder, but Mars boilers will not need this.
On Mars, due to the extremely low atmospheric pressure the expansion ratio between High pressure and exhaust will be much greater than applies on earth. Reciprocating engines are not going to be able to provide this expansion and turbines will have to be used, even for traction equipment.
The fluid will need to be reheated between stages, as is done in Earth power stations, but here it is done for thermodynamic reasons. On Mars there is a more important reason. Expanding cool CO2 will turn some of it's mass back into solid particles which will rapidly erode turbine nozzles and blades.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#11 2018-06-03 19:28:21

SpaceNut
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Re: CO2 Sublimation Heat Engine

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#12 2018-06-04 15:00:55

elderflower
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Re: CO2 Sublimation Heat Engine

Louis, the boiler must be at high pressure so that gas released from it can drive a turbine. It is difficult to push a solid into such a boiler against the pressure of the gas trying to escape, whilst avoiding large losses of gas. It is much easier to do it with liquid using a pump. It can be done using an airlock type of system, but there are still large losses involved as the lock is blown down to allow more solids to be loaded.

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#13 2018-12-09 18:10:07

SpaceNut
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Re: CO2 Sublimation Heat Engine

Its funny how we are going around topics again that we started not to long ago.

I a recent topic we were talking about using the sublimation of dry ice and solar heating to generate pressure.

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#14 2018-12-19 20:28:21

SpaceNut
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#15 2018-12-20 20:53:03

SpaceNut
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Re: CO2 Sublimation Heat Engine

The trouble with CO2 for mars is just how thin it is and how much energy is required to get it to a useful pressure and quantity

We know that we can get dry ice with a slight nugde during the night from a cryo chiller plate of chamber but is still a small quanty of dry ice and is dependant on how larget the surface area is.

Then it needs to be moved before day light to a chamber to allow solar heating to rise the pressure in this chamber to force it to that next level.

So could a solar chimney help to create that rise in pressure for making it easier to compres Add to that concentrating panels to force the heat level up makes this as good as it can be without using tons of power.

https://www.math.purdue.edu/~lucier/The … himney.pdf

https://www.designingbuildings.co.uk/wiki/Solar_chimney

386px-Solar_chimney.jpg

A single solar chimney with a suitably large glazed roof area and a high chimney can be designed to generate 100 to 200 MW continuously 24 h a day on earth and even if we only get 10% its way more than what we get without it. So what is the updraft volume of air that has gone up the chimney is what is important for mars as that a flow of co2 that we need..

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#16 2018-12-20 22:33:16

SpaceNut
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#17 2019-11-26 17:19:17

SpaceNut
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Re: CO2 Sublimation Heat Engine

Heat Engine Projects.
http://www.redrok.com/engine.htm

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#18 2019-11-27 19:01:32

SpaceNut
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Re: CO2 Sublimation Heat Engine

What if we had a long metal pipe running up a sun facing mountian or hill that has segments with values in the sections to which the length of the pipe is opened to allow CO2 to enter at Mars pressure. Just before sunrise the values all close and since the top of the mountian will see sun first we allow the first segment at the top to heat and if its got solar reflectors to concentrate the heat on that section, we then once pressure builds vent to the mars level pressure in the next section before closing the valve. That section will then be heated with the addition mars air in it to repeat for the next and so forth down the length of the pipeline until the exit is at a very high pressure and volume. If possible the first section could open to reload its volume and we could repeat for the entire day until night falls once more.
I think the venting from one section to the next if exiting through a turbine could create a bit of power for each downward thrust of force as caused via expansion of co2 by heating.

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#19 2019-11-27 20:32:49

Calliban
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From: Northern England, UK
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Re: CO2 Sublimation Heat Engine

SpaceNut wrote:

What if we had a long metal pipe running up a sun facing mountian or hill that has segments with values in the sections to which the length of the pipe is opened to allow CO2 to enter at Mars pressure. Just before sunrise the values all close and since the top of the mountian will see sun first we allow the first segment at the top to heat and if its got solar reflectors to concentrate the heat on that section, we then once pressure builds vent to the mars level pressure in the next section before closing the valve. That section will then be heated with the addition mars air in it to repeat for the next and so forth down the length of the pipeline until the exit is at a very high pressure and volume. If possible the first section could open to reload its volume and we could repeat for the entire day until night falls once more.
I think the venting from one section to the next if exiting through a turbine could create a bit of power for each downward thrust of force as caused via expansion of co2 by heating.

It would work.  You would need to cool the CO2 as it passed from one stage to the next.  You are basically relying on gas expansion in one section to compress the gas in the next section.  The length of each subsequent pipe section would be shorter than the one before it, with a progressive reduction in volume and increase in pressure.  The valves could be solenoid valves, opening in a timed sequence, maybe driven by internal thermostats.  I don't know what the efficiency would be.  But the greater the temperature difference between the hot and cold sections of gas, the fewer stages needed.

Here is another interesting concept: the hydraulic air compressor.  Bubbles are carried down a pipe by the momentum of the water and are compressed by the increasing hydrostatic pressure.  The compression takes place at constant temperature, making this the most efficient compressor known to man.  But it is large and bulky, requiring a head height of about 100m to produce air of sufficient pressure for air tools.  Traditionally, high head trompes have been fed by flowing rivers and have been used in deep mining applications, where high volumes of compressed air are needed to power tools and provide ventilation.  It has no moving parts.

https://en.m.wikipedia.org/wiki/Trompe

Something like this could be used on Mars, in a closed cycle starting with slightly compressed CO2.  The only problem is that CO2 is highly soluble in cold water.  To release the compressed CO2, it may be necessary to heat the water or pass it through a restriction leading to local pressure drop.

Water from the low pond would be returned to the high pond using a solar powered pump.  Given that CO2 is stored in a chamber under pressure, this system could function as compressed air energy storage.

Last edited by Calliban (2019-11-27 20:48:52)


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#20 2019-11-27 21:15:15

SpaceNut
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Re: CO2 Sublimation Heat Engine

For cooling we can use the cold of mars thats captured by amonia or other suitable working fluid to save the cold into under ground storage to insolate it from the solar energy of the day. After the co2 is heated the inlet could pass between a set of cold plates that have a heat exchanger built into them which is fed from the under ground cooling stores. The inlet to refill the segment that has just been exhausted during the day could be precooled by the same stores of cold stores save from the evening.
Aside from the electronics and the most had to make parts we could make this from insitu materials from recycled ship parts.

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#21 2019-11-28 08:14:37

Calliban
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Re: CO2 Sublimation Heat Engine

SpaceNut wrote:

For cooling we can use the cold of mars thats captured by amonia or other suitable working fluid to save the cold into under ground storage to insolate it from the solar energy of the day. After the co2 is heated the inlet could pass between a set of cold plates that have a heat exchanger built into them which is fed from the under ground cooling stores. The inlet to refill the segment that has just been exhausted during the day could be precooled by the same stores of cold stores save from the evening.
Aside from the electronics and the most had to make parts we could make this from insitu materials from recycled ship parts.

Ammonia has some excellent characteristics as a heat transfer fluid.  High specific heat; high thermal conductivity and a vapour pressure that is400KPa at 0C and 1.77KPa at -63C.  It would make a good liquid phase heat transfer fluid and an equally good vapour cycle fluid between these temperature limits as well.  At Martian pressures and temperatures, ammonia will evaporate from any exposed contaminated surface, which should reduce issues of toxicity during maintenance.  On the downside, we would need to manufacture it user the Haber process on Mars.  But we would probably do that anyone for fertiliser production.

https://www.engineeringtoolbox.com/ammo … _2013.html

Two things make compressed CO2 energy storage very practical on Mars.  (1) Ambient temperatures are far beneath CO2 critical point and at night they are actually beneath triple point.  This should mean that very little compressor work is actually needed to compress CO2, especially if intercooling is used.  (2) At Martian temperatures, CO2 can be stored as liquid under modest compression.  This greatly improves energy density, as vaporisation energy can be stored as low quality heat in practically any bulk material.  Whereas compressed air at 10bar @20C has density of about 12kg/m3, compressed CO2 at the same pressure at -43C would have about the same density as water – about 80 times greater than compressed air at the same pressure.

https://en.wikipedia.org/wiki/File:Carb … iagram.svg

Getting back to the original topic - the sublimation heat engine.  Assuming we find solid CO2 in accessible locations on Mars, it can be converted into a liquid with modest amounts of heating at pressure.  The liquid can then be injected into a boiler, evaporated at high pressure and used to generate mechanical power.

Last edited by Calliban (2019-11-28 08:17:51)


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#22 2019-11-28 10:05:42

SpaceNut
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Re: CO2 Sublimation Heat Engine

The pontential issue for the dry ice is how to get a sealed chamber that will be able to take the pressure build up as its melted to a vapor since the ice will be at mars pressure when frozen.

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#23 2019-11-28 10:43:43

Calliban
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Re: CO2 Sublimation Heat Engine

SpaceNut wrote:

The pontential issue for the dry ice is how to get a sealed chamber that will be able to take the pressure build up as its melted to a vapor since the ice will be at mars pressure when frozen.

I would propose a steel pressure vessel, with a door on the top and bottom and heating elements in the jacket.  You shovel the dry ice in the top and seal the top door.  Apply heat and the CO2 will melt and the chamber will pressurise to its vapour pressure.  The vapour pressure itself will be enough to force the liquid into a secondary boiler, which would then be isolated by valve.  You then purge the remaining pressure, open the bottom door and scrape out any contaminants.

A robust locking feature would be needed on both doors, as the pressure within the vessel will rise upwards of 5bars during the melting phase.  I would imagine that interlocks or some other safety feature would be needed.

Last edited by Calliban (2019-11-28 10:46:03)


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#24 2019-11-28 13:29:52

SpaceNut
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Re: CO2 Sublimation Heat Engine

So far we are putting energy in but we may have what is required after a few times of capture and processing such that we can make the eventual engine to drive a generator system to create power.

The Dry Ice Engine - an Alternative Energy Source for Mars Colonies

High School Students Construct Dry Ice Engine To Power Colonies on Mars a project these young scientists entered into the TIME 4 Real Science Program -- a student-led independent research and scientific discovery program in North Carolina begun in 2006 by teachers Jennifer Williams and Mary Arnaudin.

http://time4realscience.org/

Looks like the dry ice is broken and enters the value which is closed after its put in to what appears to be an air tank in which they assembled their engine using a simple Arksen pressure vessel, an air hose, and an air grinder that was attached attached to a small generator.
Dry_Ice_Engine.png

There is nothing new about pressure engines. They use the energy stored in fossil fuels to turn water into useful mechanical or electrical energy through heat transfer, and are therefore also called heat engines -- the most common type being the steam engine.

Basically, in a steam engine, fuel is used to vaporize the water into steam. The steam is collected and contained in a pressure vessel which, once an appropriate pressure is reached, releases that steam to power a turbine (for electrical energy) or pistons (for mechanical energy)

South Polar Cap alone contains somewhere between 9,500 and 12,500 cubic kilometers of dry ice -- enough to double the entire planet's atmospheric pressure if it were ever released.

sublimate, or change directly from a solid to a gas at only ­-78℃.

Dry ice was crushed and added into the pressure vessel by way of a ball valve and allowed to sublimate until a pressure of 90 psi was achieved.

Engine_Operation.png

Missing details from the 262 gram of dry ice experiment is the temperature, whether it was allowed to continue to climb and how long did the output of 90 psi last to turn the turbine before dropping off if temperature was not continued to be increased. The next was the wattage power created at what RPM for the generator component.

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