Solar chimeys - Feasible?

louis · 2018-12-21 19:26:31

OK - why don't we get specific?

How much energy would be required to tow say one ton of frozen CO2 from the polar region to the temperate zone (I am guessing that's about 3500kms, given Mars's extreme "wobble" factor. I think a robot Mars rover truck could cover 500kms per sol...so that would be 7 sols's worth of travel. At 50 kws constant that would be about 8.5 MwHs of energy used in towing one ton that distance. I don't know whether you could do it for less than 50 Kws constant over the 7 sols.

But anyway that is perhaps a starting point and one might ask how much energy one ton of solid CO2 might release when put into the right pressure chamber with a turbine attached....

JoshNH4H wrote:

Hey Louis,
I briefly discussed the possibility of bringing CO2 from the poles to the temperate equatorial regions as fuel in this post
I wrote:
It's certainly conceivable that mining dry ice at the poles could be economical, but it's hard (for me) to imagine that it would actually make sense unless the end user is actually at the poles.
You used coal as an analogy, and it's a pretty decent one. However, rather than showing the potential value of CO2 mining I believe it shows why it probably won't be worthwhile.
I believe the appropriate comparison is the system we were discussing before: a refrigeration system that uses energy to freeze CO2 out of the atmosphere. Here are the costs and benefits of such a system:
Costs:
Requires industrial equipment
Consumes energy
System has not been designed fully yet
Benefits:
Generates ~1 kg per kWh of inert gas (primarily Nitrogen and Argon)
Works equally well anywhere on Mars
Now, by comparison, here are the costs and benefits of pole-mining:
Costs:
Requires an ongoing supply of human labor (All mining does)
Consumes energy
Requires shipment over thousands of kilometers
Requires industrial equipment
System for mining a substance that sublimes at 195 K has never been built and would require some tweaks to existing techniques
Benefits:
Will produce water as a byproduct
In my view, the question is: Is more labor and thousands of km of shipping worth saving yourself 150 kJ/kg? In my opinion, it is not. It's good to compare this to coal: Coal on Earth has an energy content of 30 MJ/kg, 200 times greater than the energy you save. Because the energy content is so high, it really is worth pulling out out of the ground and shipping it to the point of use (or at least it was in times past). I question whether mining CO2 from the poles would save any energy at all.

SpaceNut · 2018-12-21 20:05:13

Well a prolonged stay waiting to fill up a carrier will take energy even doing nothing just to keep it possible to be in a useable. Then you need the energy for the equipment to carve it out of the solid ice dirt fields. The equipment to move it into the carrier and those equipment will also need heating to keep it useable.

https://news.yahoo.com/moody-photo-mars … 37923.html

https://www.engadget.com/2018/12/21/mar … ev-crater/

SpaceNut · 2018-12-21 21:40:44

998da01195006d6597e5ea9d4dfc3c3d

Mars Express satellite captured images of the 50-mile wide Korolev crater filled with ice. Which has remained even in summer.

Its most likely frost mixed water....

louis · 2018-12-22 05:21:08

I just checked on Wikipedia and find this crater has 2200 cubic kms of WATER ice! I make that to be about 2.2 trillion tonnes of water!!! No wonder it doesn't all evaporate in summer!

SpaceNut wrote:

https://s.yimg.com/ny/api/res/1.2/Eafvu … 9d4dfc3c3d
Mars Express satellite captured images of the 50-mile wide Korolev crater filled with ice. Which has remained even in summer.

At 73 degrees north, it's not as near the pole as I expected. It's probably about 2000 kms or so away from some of the best insolation on Mars at around 30 degrees north. I suspect we can find better water sources in terms of location but if worse came to worse you could definitely have a constant chain of water extraction robot rovers travelling to the crater and returning, each laden with a couple of tonnes of water.

JoshNH4H · 2018-12-27 10:55:43

louis wrote:

OK - why don't we get specific?
How much energy would be required to tow say one ton of frozen CO2 from the polar region to the temperate zone (I am guessing that's about 3500kms, given Mars's extreme "wobble" factor. I think a robot Mars rover truck could cover 500kms per sol...so that would be 7 sols's worth of travel. At 50 kws constant that would be about 8.5 MwHs of energy used in towing one ton that distance. I don't know whether you could do it for less than 50 Kws constant over the 7 sols.
But anyway that is perhaps a starting point and one might ask how much energy one ton of solid CO2 might release when put into the right pressure chamber with a turbine attached....

I can do my best, but any number I give will necessarily be a very rough estimate.

The physical minimum amount of energy required to transport something 3500 km is 0 J/kg (for an object moving on a perfectly level surface in a frictionless vacuum). No real world transportation system is that good, naturally, so that's not good enough. This means that we're really trying to get a handle on what we could expect technologically which is sort of a difficult question.

I think the closest analogy would be the energy use per mile of 18-wheeler trucks. Some factors suggest that the gas mileage will be higher (basically no drag, lower speeds, and lower gravity) while others suggest it might be higher (I don't think Martian roads will be anywhere near a US interstate in quality for a long while). Based on this website the average 18-wheeler gets 4.5 mpg (52.3 L/100 km) and according to this page they can haul up to 80,000 lb (36 tonnes).

Gasoline contains roughly 40 MJ/kg of energy (excluding Oxygen, naturally) and has a density of roughly 0.9 kg/L. This means that these 18-wheeler trucks use ~500 J/kg-km. Over 3500 km that works out to 1.75 MJ/kg (0.5 kWh/kg).

I have low confidence in this number, but it's a start. A reasonable range would be from, say, 300 kJ/kg to 10 MJ/kg (0.1 kWh/kg to 3 kWh/kg). It's worth noting that it would be much less if you use train transportation but it would be a major project to build a railroad through such wild countryside, comparable to the American Transcontinental Railroad. It's also worth noting that internal combustion engines are not very efficient so that you might expect to use 3 times less energy with a battery electric system, but also that a battery-electric system will have some sort of range limitation (necessitating charging stations every 100 or 200 km, which is not crazy at all along a major shipping route) or else will be basically 100% batteries.

My supposition is that you are going to be in favor of batteries, so I won't get into the various aspects of an internal combustion system. For the purposes of this thread I will use a figure of 100 kJ/kg-3.5 MJ/kg (0.03 kWh/kg to 1 kWh/kg). For reference, I estimated in this post that it would take 150 kJ/kg to freeze CO2 out of the atmosphere. The former number ignores the energy required to mine the dry ice, which will be substantial; the latter ignores the inefficiency of refrigeration (50-80%), which is also substantial, but at a first pass it's unlikely that trucking dry ice from the north pole will save any energy at all.

Now, the question of how much energy you can get out likewise is a difficult one. Unlike many chemical fuels, dry ice contains no inherent energy. The answer for how much energy you can get out really depends on what your heating source is. At various points in the steam powered rover thread, which I have linked to, I estimated: 41 kJ/kg, 80 kJ/kg, 166 kJ/kg, and 320 kJ/kg.

In short, having looked at the numbers, I believe that my initial feeling has been confirmed: Mining dry ice from a polar cap to use in an energy generator is a marginal activity in general, but is extremely unlikely to be worthwhile if you are not physically located near a polar cap.

SpaceNut · 2018-12-27 12:24:04

I would agree that local mining plus use is a must early on and that without nuclear power at the poles is a no go....

CharlesAnigh · 2019-04-01 16:51:07

Just wonder if any home owners have a solar panel setup to save money on electricity?

SpaceNut · 2021-02-09 18:21:29

Nuclear talk about molten salt, solar concentrating and such reminded me of this topic.

Which brings me to size matters in why KRUSTY make sense for mars use not to much mass, steady 10kw electrical, plus a plausible 30kw of IR heat make use of and its already a molten salt unit.
Use an up draft chimney to heat compress Mar's Co2 and create power from the updraft.

SpaceNut · 2021-10-24 20:26:57

Some links on solar chimneys....

Using a source of heat under the shape will accelerate the draw and updraft.

https://peer.asee.org/student-project-t … -power.pdf

https://en.wikipedia.org/wiki/Solar_chimney
https://en.wikipedia.org/wiki/Solar_updraft_tower
https://www.solaripedia.com/13/371/5041 … ssion.html
https://www.solaripedia.com/files/972.pdf
https://architecture.mit.edu/sites/arch … roject.pdf
https://en.wikipedia.org/wiki/Concentrated_solar_power

solar power towers on mars - km-high vertical wind tunnel turbo-elec
Solar chimeys - Feasible?
Solar thermal power - Fathers Day gift
An Empirical Model of Thermal Updrafts

https://www.briangwilliams.us/power-gen … power.html

https://www.researchgate.net/post/Hi_I_ … ns_of_this

https://www.solarpaces.org/how-csp-works/

Was thinking of how to combine the two things such that you end up with a sort of parabolic shape dish made of troughs that has the chimney as the receiving element of the concentrated sun light.

Calliban · 2023-11-17 14:44:56

A closed heat-pipe solar chimney could work. The Martian atmosphere has too low density for the Earth based solar chimney to work on Mars. But a closed pressurised tube could work.

We place solar panels at ground level. Pressurised carbon dioxide flows through these panels, heating it to 20°C. The tower consists of an outer steel tube, with an inner tube running within it. Hot CO2 rises up the inner tube by convection. It exits the top of the inner tube and then flows down the gap between the two tubes. As it does so, it loses heat to the skin of the outer tube, which in turn loses heat by radiation. A turbine is placed at the base of the inner tube. This captures kinetic energy from the rising CO2.

Something like this:

The vertical tube appears much shorter than in reality. It would be hundreds of metres tall to provide the highest thermal driving head possible. The mound of rock and soil would function as a thermal cold store. At night, heat would conduct out of the mound into the outer tube. The CO2 in the outer tube would rise by convection and would the tube would radiate heat into the Martian night.

Last edited by Calliban (2023-11-17 16:13:27)

SpaceNut · 2023-11-17 18:39:50

I have been reading the information for the tower normal earth tube if you make it shorter the amount of air flow drops but increase it and it rises. I believe it's due to shape of the chimney becoming wider at the top versus the base with colder air at the top.

On can also use a working fluid to do the conversion in a closed loop as well since that will act like a heat pump ac unit in reverse.

SpaceNut · 2023-11-18 18:59:40

Windmill blade technology applies to this topic to turn a rotor that connects to a shaft for a generator.

https://en.wikipedia.org/wiki/Wind-turbine_aerodynamics

Many of the equation answers are part of the updraft as well.

https://www.windpowerengineering.com/bl … art-of-ge/

https://www.nmmesa.org/wp-content/uploa … Blades.pdf

https://energy5.com/blade-dynamics-deco … ine-rotors

https://www.dnv.com/Images/Bladed-Techn … 149133.pdf

SpaceNut · 2023-12-16 14:12:50

A simple, clever twist in solar tower design produces power 24/7

Researchers from Qatar University and Jordan’s Hussein Technical University have found a way to double the power produced from a type of solar tower. The “twin technology solar system” they report in the journal Energy Reports can produce energy all day and all night.
Solar panels, which absorb light and turn it into electricity using photovoltaic materials, are a conventional, well-known technology to harvest the sun’s energy. The concept behind the new solar tower system is very different. It relies on the fact that hot air rises.
https://www.sciencedirect.com/science/a … 4723015512
Such solar updraft towers are typically made from glass or other greenhouse materials that trap heat. The air is heated at ground level and as it rises up the tall tower, it spins a turbine to produce electricity. But the idea remains experimental. Costs of building the large, tall glass towers remains prohibitive for mainstream use.
The new twin-technology tower could bring down cost by producing over twice as much power as previous designs, say the researchers. Their design entails building a secondary tower around the inner tower.
The second tower is a cooling tower, in which air would be sent downward to spin another turbine. To accomplish this, the researchers propose spraying a fine mist of water into the hot air that reaches the top of the tower, making it cooler and sending it downward.
https://www.anthropocenemagazine.org/co … rgy-tower/
In the paper, the researchers present details of a model tower structure that is 200 meters tall, with an inner updraft heating tower that is 10 meters in diameter. The outer downdraft cooling tower’s diameter is 13.6 meters. The gap between the towers is separated into 10 channels, each serving as a cooling tower, with water misting systems at the top and turbines at the bottom.
Using simulations of the tower combined with local weather data, the team estimated that it would generate a total of about 753 megawatt-hours of energy annually. That is about 2.14 times the power of a traditional solar updraft tower. The external cooling towers would produce about 400 megawatt-hours, and the inner heating tower working better during the day under the hot sun to generate around 350 MWh.
The researchers found that seasonal variations in temperature and humidity affected the external tower more, so its output power swung widely throughout the year. Its performance decreases significantly in high humidity, they say, so it is best used in areas with hot and dry weather. They tested their simulation in Riyadh City, which is a hot, dry desert climate, and the results show that the system could be beneficial to deploy there.
“However, the system has limitations, such as access to water for the operation of the downdraft system,” the team writes. They plan to work on a deep techno-economic analysis of the proposed system and a take a closer look at its scalability.

AA1lur4x.img?w=400&h=250&m=6

Calliban · 2023-12-18 05:35:51

The taller the chimney, the greater the power output. On Mars, we have a different situation. The air is a thin gas dominated by CO2, with a temperature far beneath its critical point. It takes very little mechanical work to compress the gas. If we compress it at the top of the tower, we have a dense gas which should fall down the tube. We can heat it with a low grade heat source at the bottom and expand it through a turbine.

The attached link shows the properties of CO2 at a temperature of -50°C, between the pressure of 0.1 and 1.0MPa, in increments of 0.01MPa.
https://webbook.nist.gov/cgi/fluid.cgi? … fState=DEF

If we inject CO2 at a pressure of 0.1MPa (1atm) at the top of the tower, static pressure will result in a pressure gradient between the top and bottom of the tower. The density of the gas increases roughly proportional to static pressure until the gas reaches a pressure of 0.68MPa, at which point it phase transitions into a liquid. If the tower is tall enough, CO2 will actually turn to liquid before reaching the bottom. The liquid CO2 can then be allowed to drain by gravity into a boiler, where solar, geothermal or nuclear heat convert it into a high pressure gas that exhausts through a gas turbine.

Static pressure increases with the density of the gas above that point and density is a function of pressure. I used a spreadsheet to work out how tall the tower would need to be to reach a pressure sufficient to liquefy the CO2 for various injection pressures at the top. For an injection pressure of 0.1MPa, this works out to be 20.85km. If injection pressure is 0.2MPa, this declines to 13.16km. If injection pressure is 0.5MPa, minimum h is 3.24km. The density of liquid CO2 is 1155kg/m3. So every 10m of tower height beneath the liquidus point, increases pressure at the base by 43KPa.

The significance of this finding is that a nuclear reactor built on Mars, will not need a large radiator panel. We use the nuclear heat to boil the liquid CO2, expand it through a gas turbine and let the expanded gas carry away the waste heat as it exhausts into the atmosphere. We could even build reactors that pass the CO2 directly through the core, obviating the need for heat exchangers. The liquid CO2 in the tower will exert its own static pressure, also avoiding the need for feed pumps. However, the CO2 condensation tower is obviously not free. It would be cheaper to build if we could use a convenient mountain to provide the required elevation for the compressor. That way, instead of building a tower, we build a steel pipe running down the mountain. If we add an additional pipe length beneath the liquidus point, then the pressure at the bottom of the pipe can be tailored to provide any desired pressure input for tge reactor without need for an injection pump.

Last edited by Calliban (2023-12-18 07:15:03)

tahanson43206 · 2023-12-18 07:14:46

For Calliban ....
Re your reply in the Van Allen Belt topic ... thank you for finding a use for that otherwise mostly annoying natural phenomenon!

Regarding Post #39....

Picking up on your observation about possible value as a way to generate power from otherwise wasted low grade heat...

1) Can this concept be scaled down, or is there a minimal size below which it is less attractive?
2) Would this concept work with NASA's Krusty at only 10 KW?
3) Would this concept work on Earth?

Follow up question about the Van Allen Belt .... is there a way to capture some of that energy from the ions in the Van Allen Belt? You have shown that the ions there might contribute to slowing a space craft despite their small mass. I was surprised to learn that the total mass of the entire Belt is estimated to be so much less than a kilogram.

(th)

Calliban · 2023-12-18 07:45:52

TH, If we inject CO2 into the tower at its liquefaction pressure of 0.683MPa, then the tower can be scaled down. It all depends upon what pressure we want to inject CO2 into the boiler. The higher that pressure is, the higher the thermal efficiency of the plant and the more compact the turbine can be. Both are important economic drivers.

On Earth, liquid air energy storage is being developed as a grid energy storage system. If we build the liquid air tank on top of a mountain, then the energy recovery plant can be located at the bottom of the mountain and can benefit from the gravitational potential energy of the liquid column. The downside is that the compressor plant is starting with air at a lower pressure due to the height. However, air temperature also falls as height increases, which makes compression more efficient. Maybe the two effects will balance out, leaving us with a net benefit.

Another possibility occurs to me as an application on Mars. What if we drill a deep well instead of building a tower? Liquid CO2 injection could be an interesting way of harvesting geothermal heat to produce power. The CO2 can turn back into gas at temperatures beneath 0°C. So we don't neccesarily need a lot of heat to make this work on Mars. At 0°C, CO2 saturation pressure is 35bar.
https://www.engineeringtoolbox.com/CO2- … _2017.html

So geothermal resources on Mars won't necessarily need to be hot in the way we tend to think of geothermal heat. Which is convenient given that the Martian geothermal gradient is much shallower than Earth.

Last edited by Calliban (2023-12-18 07:57:07)

tahanson43206 · 2023-12-18 08:00:13

For Calliban re #41

Thanks for taking up the question of use of your idea for a KRUSTY plant ....

It seems to me it ** might ** be possible to estimate the tradeoffs at work in this situation .... We are investing energy from our primary resource (fission) to try to recover energy from otherwise wasted low grade heat. What I cannot determine, but which might be something you can work out, is whether there is a net benefit to making the investment?

If it takes more of our primary energy than we can recover from our secondary process, then it is not worth while.

Is this something you can work out?

The KRUSTY is likely to take up residence on Mars in the next few decades.

Certainly a Chinese version of a low power reactor is likely to show up on Mars.

NASA is restricted in funding by US Congressional needs and conflicts, but a Chinese success might provide incentive to place KRUSTY on site sooner than would otherwise be the case.

What material might be used to make that long pipe?

What investment of energy is likely to be needed to make that pipe?

A lot of low grade heat is wasted on Earth because recovery just isn't worth the trouble.

That rule-of-thumb may apply on Mars as well.

(th)

Calliban · 2023-12-18 08:07:56

Looking at the geothermal case, Martian geothermal gradient is estimated to be one third of Earth's average, which is 25K/km. So that is 8.33K/km. The average surface temperature of Mars is -55°C. So to harvest heat at 0°C, we would need to drill down 6.6km, or about 21,500'. That is a non-trivial depth, even on Earth. It suggests to me that it is important to locate our base in an area with a locally high geothermal gradient.

However, one thing this estimate doesn't account for is the porosity of the Martian surface. The outer regolith is a loose layer and under the vacuum conditions on the surface of Mars, it provides about the same insulation value as rockwool. So temperature could increase more rapidly than 8.33K/km in the upper layers.

As to what we would make the tube out of, it would depend upon ground conditions. If the well is completely dry, then I would suggest low carbon steel. But it is entirely possible that we would encounter groundwater on Mars at that depth. If so, then plain carbon steel would suffer corrosion issues. Stainless is probably too expensive. We could try a segmented pipe made from drip galvanised steel or even cast basalt.

Last edited by Calliban (2023-12-18 08:16:05)

Calliban · 2023-12-18 08:34:07

On Earth, we would build a LAES plant wherever we happen to have a convenient source of low grade heat. Such a heat source greatly increases the efficiency of the expansion process. One resource that we could use is waste heat from thermal powerplants. A low pressure turbine typically exhausts steam at a pressure of 70mbar. This equates to a condenser temperature of 30°C. We could store this heat in a pond or within a rock mass, through which air evaporation pipework also runs.

There are two options. We can run the energy recovery plant and steam plant continuously, in which case we don't really need to store very much heat as we are using it immiediately. The air liquefaction plant would run intermittently when grid power was in excess. The second option is to store the heat in a thermal mass and only run the energy recovery plant intermittently. The first option eliminates the need for a large heat reservoir. But the reservoir is really just a pond or mass of rock. The second option requires a somewhat smaller liquid air tank. Without a proper engineering study I don't know which is the best option. But both would work.

On Mars, we could actually do something similar, but using L-CO2 instead of L-Air. The tower used to store the L-CO2, could be made from steel. It could also be made from a ceramic like brick or concrete. Although the CO2 is pressurised, the weight of the tower would result in compressive forces which would allow a concrete tower to resist the outward pressure exerted by the liquid CO2. This is how compressive concrete water towers work here on Earth. They don't explode because the net forces on each element remain compressive. It is also how we are able to build dams out of stabilised earth, even though it has pitiful tensile strength. So we could build towers out of materials like adobe or bonded stone, provided there were a leak resistant lining and enough loading to keep net forces compressive. Building the liquefaction plant on top of the tower provides some of the weight loading needed to resist the internal pressure.

Last edited by Calliban (2023-12-18 08:59:02)

tahanson43206 · 2023-12-18 08:51:21

For Calliban ... at the risk of taking this topic wildly off course, I'm following up on what I understand to be the general flow of your presentations on capture of useful energy from low grade heat .... The Earth provides substantial quantities of low grade heat at thermal vents in the deep ocean.

A problem humans face is heating of the oceans.

If I understand the process you are describing correctly, low grade thermal energy could be removed from the ocean, if a plant were deployed at a location where that makes sense.

If we need a new topic to consider this question, please create one.

(th)

SpaceNut · 2023-12-18 10:09:24

Most of the experimental towers have greenhouses under the canopy of water as well as possibly sand but the issue here is we are not controlling the input of air to the rise of the thermal change only the amount of heat reflection or absorption to cause the lift effect to happen.

Those were greeat numbers for a mar's version Calliban and using the KRSTY reactors surplus heat as the means to generate lift is of course something that I did suggest as well. for power and collecting of co2,

SpaceNut · 2024-05-26 10:13:47

Even a small solar chimney can be used to create cooling for a building occupant.

rPSIscAoNLoALG-ZMdu8SGctHj5_bt0sQMkYRlCtSQvv0e2zaLPJfdMgaI2cuxre5Bqq3_DUzgWBpyeBg7mIaB2eH9JCuoBJY1z1evowlmQO0ubemCFxL-A5zopLjO9WSqIHX8FMonYRQAD9dA

https://theconstructor.org/building/sol … rk/564685/

https://www.pinterest.com/pin/726698089842292947/

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#26 2018-12-21 19:26:31

Re: Solar chimeys - Feasible?

#27 2018-12-21 20:05:13

Re: Solar chimeys - Feasible?

#28 2018-12-21 21:40:44

Re: Solar chimeys - Feasible?

#29 2018-12-22 05:21:08

Re: Solar chimeys - Feasible?

#30 2018-12-27 10:55:43

Re: Solar chimeys - Feasible?

#31 2018-12-27 12:24:04

Re: Solar chimeys - Feasible?

#32 2019-04-01 16:51:07

Re: Solar chimeys - Feasible?

#33 2021-02-09 18:21:29

Re: Solar chimeys - Feasible?

#34 2021-10-24 20:26:57

Re: Solar chimeys - Feasible?

#35 2023-11-17 14:44:56

Re: Solar chimeys - Feasible?

#36 2023-11-17 18:39:50

Re: Solar chimeys - Feasible?

#37 2023-11-18 18:59:40

Re: Solar chimeys - Feasible?

#38 2023-12-16 14:12:50

Re: Solar chimeys - Feasible?

#39 2023-12-18 05:35:51

Re: Solar chimeys - Feasible?

#40 2023-12-18 07:14:46

Re: Solar chimeys - Feasible?

#41 2023-12-18 07:45:52

Re: Solar chimeys - Feasible?

#42 2023-12-18 08:00:13

Re: Solar chimeys - Feasible?

#43 2023-12-18 08:07:56

Re: Solar chimeys - Feasible?

#44 2023-12-18 08:34:07

Re: Solar chimeys - Feasible?

#45 2023-12-18 08:51:21

Re: Solar chimeys - Feasible?

#46 2023-12-18 10:09:24

Re: Solar chimeys - Feasible?

#47 2024-05-26 10:13:47

Re: Solar chimeys - Feasible?

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