Highly Transparent Aerogel/Getting more heat out of sunlight

Void · 2019-07-02 11:17:24

Well, I have been laying low, (As apparently all the other chickens are as well), plotting plots for the future.

But this item appears to have just too much potential to change things, that I will post it's link, and I will comment on it.

http://news.mit.edu/2019/aerogel-passiv … light-0702

Getting more heat out of sunlight
Material developed at MIT can passively capture solar heat for home heating or industrial applications.
David L. Chandler | MIT News Office
July 1, 2019
A newly developed material that is so perfectly transparent you can barely see it could unlock many new uses for solar heat. It generates much higher temperatures than conventional solar collectors do — enough to be used for home heating or for industrial processes that require heat of more than 200 degrees Celsius (392 degrees Fahrenheit).
The key to the process is a new kind of aerogel, a lightweight material that consists mostly of air, with a structure made of silica (which is also used to make glass). The material lets sunlight pass through easily but blocks solar heat from escaping. The findings are described in the journal ACS Nano, in a paper by Lin Zhao, an MIT graduate student; Evelyn Wang, professor and head of the Department of Mechanical Engineering; Gang Chen, the Carl Richard Soderberg Professor in Power Engineering; and five others.
The key to efficient collection of solar heat, Wang explains, is being able to keep something hot internally while remaining cold on the outside. One way of doing that is using a vacuum between a layer of glass and a dark, heat-absorbing material, which is the method used in many concentrating solar collectors but is relatively expensive to install and maintain. There has been great interest in finding a less expensive, passive system for collecting solar heat at the higher temperature levels needed for space heating, food processing, or many industrial processes.
Aerogels, a kind of foam-like material made of silica particles, have been developed for years as highly efficient and lightweight insulating materials, but they have generally had limited transparency to visible light, with around a 70 percent transmission level. Wang says developing a way of making aerogels that are transparent enough to work for solar heat collection was a long and difficult process involving several researchers for about four years. But the result is an aerogel that lets through over 95 percent of incoming sunlight while maintaining its highly insulating properties.
The key to making it work was in the precise ratios of the different materials used to create the aerogel, which are made by mixing a catalyst with grains of a silica-containing compound in a liquid solution, forming a kind of gel, and then drying it to get all the liquid out, leaving a matrix that is mostly air but retains the original mixture’s strength. Producing a mix that dries out much faster than those in conventional aerogels, they found, produced a gel with smaller pore spaces between its grains, and that therefore scattered the light much less.
In tests on a rooftop on the MIT campus, a passive device consisting of a heat-absorbing dark material covered with a layer of the new aerogel was able to reach and maintain a temperature of 220 C, in the middle of a Cambridge winter when the outside air was below 0 C.
Such high temperatures have previously only been practical by using concentrating systems, with mirrors to focus sunlight onto a central line or point, but this system requires no concentration, making it simpler and less costly. That could potentially make it useful for a wide variety of applications that require higher levels of heat.
For example, simple flat rooftop collectors are often used for domestic hot water, producing temperatures of around 80 C. But the higher temperatures enabled by the aerogel system could make such simple systems usable for home heating as well, and even for powering an air conditioning system. Large-scale versions could be used to provide heat for a wide variety of applications in chemical, food production, and manufacturing processes.
Zhao describes the basic function of the aerogel layer as “like a greenhouse effect. The material we use to increase the temperature acts like the Earth’s atmosphere does to provide insulation, but this is an extreme example of it.”
For most purposes, the passive heat collection system would be connected to pipes containing a liquid that could circulate to transfer the heat to wherever it’s needed. Alternatively, Wang suggests, for some uses the system could be connected to heat pipes, devices that can transfer heat over a distance without requiring pumps or any moving parts.
Because the principle is essentially the same, an aerogel-based solar heat collector could directly replace the vacuum-based collectors used in some existing applications, providing a lower-cost option. The materials used to make the aerogel are all abundant and inexpensive; the only costly part of the process is the drying, which requires a specialized device called a critical point dryer to allow for a very precise drying process that extracts the solvents from the gel while preserving its nanoscale structure.
Because that is a batch process rather than a continuous one that could be used in roll-to-roll manufacturing, it could limit the rate of production if the system is scaled up to industrial production levels. “The key to scaleup is how we can reduce the cost of that process,” Wang says. But even now, a preliminary economic analysis shows that the system can be economically viable for some uses, especially in comparison with vacuum-based systems.
The research team included research scientist Bikram Bhatia, postdoc Sungwoo Yang, graduate student Elise Strobach, instructor Lee Weinstein and postdoc Thomas Cooper. The work was primarily funded by the U.S. Department of Energy’s ARPA-E program.

I think us North people, (Spacenut), should have hopes for this one, here on Earth. Solar for all, or better chances of it, perhaps.

We have looked at the following previously, but I am thinking it could be very useful as used with the above Aerogel. Particularly in space and perhaps on Mars, and elsewhere.

High temperature solar cells:
https://phys.org/news/2016-08-high-temp … solar.html
I am speculating that a combination of solar cells, and this Aerogel, might be more light weight than standard solar arrays, for the power output, in space. In LEO, more of the solar spectrum is available, so I am speculating that temperatures above 220 C will be available.
For Jupiter, maybe not the same solar cells, but it may be that something good could be created.

This could lead to a better solar propulsion option, potentially including ion, Steam(s), and Plasma propulsions, I think. That space environment being rather clean in general.

Mars, not so much, with dust, and I also am concerned about photolysis gumming up the Aerogel with products of CO2 and H20. But those are potential problems to overcome. CO2 snow in the wintertime, at high latitudes has to be adapted to as well.

But I think the potentials are vast.

For instance, if overcoming the above listed potential problems, and any others that show up, it is reasonable to speculate that for the polar ice caps, you could imagine a covering of this stuff, which in the summer renders heat, to melt the ice caps. You should know that I would expect ice covered reservoirs, in the beginning, but perhaps some open water after some terraforming of Mars.

Truth is, the ice of the ice caps down below, would tend to be unstable during melting, so it will be harder than that.

We still don't have a proper inventory of where water resources are available on Mars. Equator? Aquifers? Other?

But I can see an application where you could find a tolerance window, where you could have solar ponds in conjunction with an Aerogel "Dome or else covering". It is conceivable to pressurize the enclosure, but I would not go very far with that. Maybe just a bit above ambient. Would the solar pond have ice over it? Not sure. Depends of the solar flux, the amount of salt, and other factors.

Would it generally loose water to the atmosphere? I am thinking that it might even collect water from the atmosphere. You would be pressurizing it just a bit, that will help to inhibit vapors of water. Also a ice layer will also reduce evaporation due to it being able to be colder than the day, by having perhaps gathered some cold from the night. Again, a combination of structure and climate/time of year would make that a variable.

Water vapor permeability of Aerogels.
Here I have to speculate. From the reading I have encountered, I think it is variable.
https://www.sciencedirect.com/science/a … 1118306784

Memory and intuition tell me that there could be a potential to suck moisture out of the Martian atmosphere into the interior of an aerogel enclosure. Perhaps I will be proven wrong, but so what, at least I try.Well, I have been laying low, (As apparently all the other chickens are as well), plotting plots for the future.

But this item appears to have just too much potential to change things, that I will post it's link, and I will comment on it.

http://news.mit.edu/2019/aerogel-passiv … light-0702

This suggests chances. I will add at least two other processes to hope to achieve the desired results.
https://www.researchgate.net/publicatio … e_Aerogels

The Solar Still:
https://en.wikipedia.org/wiki/Solar_still
In this case, I am most interested in "Solar still built into a pit in the ground".
We will be upside down though. The condenser will be the pond or salts inside of the enclosure. Where in the solar still sunlight (U.V.) hits sand particles in the pit, and removes moisture from them with heat. The Aerogel dome will be heated on the inside. The moisture may flow from the colder and higher Relative Humidity outside. That of course will occur mostly in the cold of night. The thermal contrast could be quite high then, and during that time RH% may approach 70-100% on the outside surface.

Negative charge to direct positive water ions. Sigh.....
Well, I do recall that a method can be used, to make a soil wet on a plough blade, to lubricate it. It requires an electrical current, where the negative is attached to the plough, and I should presume the positive to the ground elsewhere. Supposedly moisture will flow through the ground towards the plough blade. The less likable version is to dry up ground so that tanks can pass through wet ground. Paranoia, suggests that this "Military Secret", has led to the lack of search results for what I said above. That method was used by the NAZI types in WWII. If my paranoia is true, I will assert that it is very annoying to have work impeded in this manner.

Here, my thinking is that the (-) charge could be imposed on the inside of an enclosure of somewhat permeable aerogel, and the (+) on the outside. If I understand correctly, then this electric "Force Field" should assist in the retention of moisture, and also may conduct moisture from the outside to the inside of the aerogel enclosure, particularly if the outside is at a ~RH% 70-100, and also assisting the presumed conduction of moisture by thermal effects, where the outside may be very cold, but the inside relatively higher.

But I am on thin ice on this, I am groping in a manner that makes sense to me, but we would need to find out what reality really provides.

I would be concerned that an electric field would attract dust to the aerogel. However I believe that electric effects can also keep solar panels cleaner from dust accumulations.

Something like this then:
https://www.researchgate.net/publicatio … lar_panels

That's about as far as I want to go with this, I have already speculated quite a lot.

But the Aerogel certainly seems to have potentials for some new adaptations.

Done.

Last edited by Void (2019-07-02 12:23:28)

Terraformer · 2019-07-02 14:54:14

220 degrees! At that point, I wonder if heat engines could become competitive with photovoltaics? Particularly if the heat can be stored and used to generate power on demand.

SpaceNut · 2019-07-02 17:55:25

When we talk temperature we are talking about solar evacuated tubes for the industry for roof top use and the upgrade to aerogel gives it a temperture boost due the higher insulative value of the aerogel versus glass vaccumn...which puts it into stream plant power generation of power....

Air report in article not for liquids which are different https://www.sciencedirect.com/science/a … 0413004780

https://www.sciencedirect.com/topics/en … -collector

evacuated tube liquid
3-s2.0-B9780081003015000047-f04-13-9780081003015.jpg?_

working fluids can be water gylcol mix, methanol or ethanol or propane, amonia, freon like compounds....which go through a heat exchange for use which is where the heat loss is occuring to the tank.

solar concentration can be done with reflection
3-s2.0-B9780081003015000047-f04-15-9780081003015.jpg?_

By the way thanks for the topic links as I still am reading them.

high temperature solar cells are using a heatsink to remove heat that would otherwise destroy the cell materials as well as lower the output voltage that they could create under load. One could add liquid cooled piping within the heatsink to allow for even higher levels of solar energy to be applied to the high temp units.

Void · 2019-07-02 20:32:16

I share the enthusiasm. And I see that indeed as you imply, a potential exists to make good machines, that use the aerogel as a component.

For Mars, I will make an alternate reach. An enclosure similar to that in my previous post, but in this case with a lower air pressure than Martian ambient. This will conflict to a degree with the maintenance of a liquid or more likely ice surface to a body of water. But games might be possible. For instance, if the ice is cold enough, then evaporation can be kept in bounds tolerable to a process. For instance, if the pond is indeed a saline stratified solar pond, and yet you want fresh water, the same vacuum you maintain to keep the enclosure at less than ambient pressure can evaporate ice, and condense it into fresh water. The ice is then helped to be cool by the evaporation at a low pressure.

Further, (now I may not understand plasma windows, and electron beams), but I hope to paint the interior surface of the enclosure of aerogel with electrons in a manner similar to how a vacuum tube television would have an electron beam to paint a television picture. I intend that the electrons would be drawn from a ground (Actually the ground). In this manner the interior surface of the aerogel would be more (-) than the exterior, and yet it would be hoped that the exterior of the aerogel enclosure would have a somewhat lesser (-) charge.
I hope then that in addition to the imposition of a differential atmospheric pressure, (Outside ambient pressure > interior pressure, also in favor of migration of moisture would be the fact that the interior would be hotter than the exterior. So waters vapor pressure would provide a pull to draw, (water ions), into the enclosure through the aerogel. And yet electrical pressure would also pull (+ water ions) into the enclosure.

None of this is proven. It is based on what I think could be done, based on what I think I know.

For Earth also though, I am very interested in what you could do with other solar devices in conjunction with the use of the aerogel.

Nice breakthrough by those people I feel.

I will clean up my first post later. Looks like I pasted repetition there.

Done

SpaceNut · 2019-07-02 21:09:17

The electron in the old TV's were high voltage and would strike a point of phosphorus which would make it glow.

Aerogel chambers filled wirh co2 would expand as it warmed inside the layers and if the acking happened to e dark the heat would go up evenmore. Circulate co2 inside would create as vented a draw on the inlet to make it re-equalize its internal pressure. Make the inlets and outlets oneway values as it cycles for the mars day and we have a means to pressurize mars co2 with no energy being used.

Void · 2019-07-03 17:20:14

You may well be correct on the electron beam. Perhaps for the purpose, something like an ionized wind machine, and a very low wavelength heat lamp might do for the purpose at night.

I sort of agree with the rest of you post. That would be an option to try.

I also am interested, in the vague potential to perhaps slightly pressurize during the day, and draw air at night. The hope would be that if we could get very fancy, it might be possible to make the porosity such that CO2 would be blocked from entering during the night, but allow moisture, and perhaps also other smaller sized molecules such as Nitrogen and Argon.

But this is not likely to be one type of machine. I am betting that there could be many variations depending on intentions and results possible.

I do think that the Aerogel as advertised should be quite good for collecting solar heat, and holding it in at night.

Where there might be a solar pond, I am thinking that although a hot very briny layer would be at the bottom, a more clement higher layer should be possible, one also less salty, and one that might support microbial life. This of course would require a method to deal with U.V.

While collecting heat from U.V. we would then want to attenuate it if some good method can be found. An another alternative is to try to wake up ancient methods for tolerance to U.V. if they did exist and can be retrieved. Theory has it that life on early Earth had to be tolerant to high levels of U.V.

Done

louis · 2019-07-03 18:20:55

Very interesting, Void!

I can see why we should maybe get excited about this if we could melt the ice caps on Mars.

I don't think heat in habs is a major issue, as (from what others have said) I understand that heat loss in a near vaccuum is pretty slow in any case.

But I can see how any process requiring intense heat build up could benefit from this.

SpaceNut · 2019-07-03 18:43:39

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

The first aerogels were produced from silica gels. Kistler's later work involved aerogels based on alumina, chromia and tin dioxide. Carbon aerogels were first developed in the late 1980s

https://www.nasa.gov/topics/technology/ … ogels.html

Since their invention, aerogels have primarily been made of silica. The silica is combined with a solvent to create a gel. This gel is then subjected to supercritical fluid extraction. This supercritical fluid extraction involves introducing liquid carbon dioxide into the gel. The carbon dioxide surpasses its super critical point, where it can be either a gas or a liquid, and then is vented out. This exchange is performed multiple times to ensure that all liquids are removed from the gel. The resulting material is aerogel.

Void · 2019-07-04 09:57:53

While appreciating other comments I note that;
Terraformer said:

220 degrees! At that point, I wonder if heat engines could become competitive with photovoltaics? Particularly if the heat can be stored and used to generate power on demand.

,
And Louis said:

I can see why we should maybe get excited about this if we could melt the ice caps on Mars.
I don't think heat in habs is a major issue, as (from what others have said) I understand that heat loss in a near vaccuum is pretty slow in any case.
But I can see how any process requiring intense heat build up could benefit from this.

This method does indeed suggest new chances to bend established reality. The inventors note that it is a troublesome process to generate the material, but then as society progresses into greater automation and robotics, that may suggest how to get the trouble and costs down.

As I understand it there is a sort of law for solar, observable at this time, that for every doubling of production the costs go down ~20%. So, as solar methods become more used so, also the cost of solar goes down.

……

One thing I am really interested in in space for this is some kind of coupling of the aerogel with a specially tuned type of solar cell. I am guessing that in the vacuum of space, with a better flux of photons, more U.V. and such, a higher performance of temperature achieved will be natural. The aerogel would be in vacuum, which implies more insulating qualities while retaining the passage of 95% of the photons, available. I do note that it is likely that if the aerogel holds in infrared, the it is likely to block the infrared from the suns spectrum. So, I expect a higher temperature than 220 C to be achievable in Earth/Moon orbits, and on the surface of the Moon as well, NEO's ~likely as well.

As I recall, the Danish solar cells can use 300 nm to 1750 nm to generate electricity. I also presume that any wavelengths shorter, could be converted into >300 nm wavelengths.

And others have been talking about joining two longer wavelength photons into a shorter wavelength photon, so that it could be used as well. I also read that for shorter wavelengths, there is work to split such into two excitons, which might allow the use of shorter wavelengths for photo cell energy. Probably just converting to a longer infrared would do perfectly fine.

The point would be that solar energy in orbit, might be achieved with much less inertia in the solar panels, and I presume this could make solar driven propulsion more useful. The aerogel adds more mass, but not that much compared to the presumed potential upgrade of performance vs. mass.

SpaceX prefers chemical propulsion, and they have their reasons. We can also speculate on nuclear propulsions, fission, and fusion eventually, particularly for human transfers, but for slower movements of bulk, I think that the suggestion of a upgrade in the performance of solar methods, could be very important.

Electrical usage that comes to mind, are ion, boiling, plasma, and mass drivers.

Others will more competently speak of ion and plasma, I am sure.

As for boiling and mass drivers, I will speak out of turn, because I suppose for those as well, there are those better than me for it. But I will take a stab at it anyway. Preaching to those better at it I suppose.

While mass drivers could shoot packets of rocks out, I prefer substances that will vaporize after ejection. Water, Dry Ice, Oxygen as potential examples. Here and there commonly available in space Insitu.

I have a tendency to fixate on Oxygen, because it is quite available even from the Moon. Water and Dry Ice are easier for obtaining and handling however.

For boiling, of course those three are good candidates. In some cases very easy to store up until use in most places in interplanetary and Earth/Moon space. I suppose we really want to jazz up things and go full on "Buck Rogers" with plasma propulsion, but to move bulk materials, over longer periods of time, perhaps using other effects like gravity boosts, I think boiling should well be considered. Less inertia in the propulsion system, perhaps less prone to break downs, and more stable in a un-crewed situation.

Done

Last edited by Void (2019-07-04 10:24:22)

Void · 2019-07-15 12:29:41

Well, this converges nicely with several things members here might favor.
https://phys.org/news/2019-07-silica-ae … table.html
Quote:

Silica aerogel could make Mars habitable...………….
The researchers suggest that regions of the Martian surface could be made habitable with a material—silica aerogel—that mimics Earth's atmospheric greenhouse effect. Through modeling and experiments, the researchers show that a two to three-centimeter-thick shield of silica aerogel could transmit enough visible light for photosynthesis, block hazardous ultraviolet radiation, and raise temperatures underneath permanently above the melting point of water, all without the need for any internal heat source.
The paper is published in Nature Astronomy.
"This regional approach to making Mars habitable is much more achievable than global atmospheric modification," said Robin Wordsworth, Assistant Professor of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Department of Earth and Planetary Science. "Unlike the previous ideas to make Mars habitable, this is something that can be developed and tested systematically with materials and technology we already have...………………."

Years ago, I recall someone called "Fogg" or something like that, probably British, on another web site suggesting, that vast doming of Mar could be done, to create pressurized space. Not a bad line of thought. Of course I am shy about such structures being trustable long term, per leaks.

Yet, the above does give a part of what is wanted. With a cold Mars, we can probably deal with any chance of overheating to generate power. And as any here know, I almost always default to using hydrostatic pressurization to achieve most of the needs. If you can melt water, then you can have hydrostatic pressurization. Then you need a way to keep the water from boiling beyond your ability to manage the evaporation. I typically default to an ice layer, but that is not a mandated limitation, it is just a convenient method, among some other methods.

Another quote from the previously posted link:

In 2018, a pair of NASA-funded researchers from the University of Colorado, Boulder and Northern Arizona University found that processing all the sources available on Mars would only increase atmospheric pressure to about 7 percent that of Earth—far short of what is needed to make the planet habitable.
Terraforming Mars, it seemed, was an unfulfillable dream.
Now, researchers from the Harvard University, NASA's Jet Propulsion Lab, and the University of Edinburgh, have a new idea. Rather than trying to change the whole planet, what if you took a more regional approach?
The researchers suggest that regions of the Martian surface could be made habitable with a material—silica aerogel—that mimics Earth's atmospheric greenhouse effect. Through modeling and experiments, the researchers show that a two to three-centimeter-thick shield of silica aerogel could transmit enough visible light for photosynthesis, block hazardous ultraviolet radiation, and raise temperatures underneath permanently above the melting point of water, all without the need for any internal heat source.
The paper is published in Nature Astronomy.

Some interpretation is required for the above. 7% would be 70 mb, which is probably quite enough for a functioning open air biosphere, if other requirements are satisfied such as U.V. flux. And they obviously do not include the eventual production of extra O2 from water, which is a long term potential, the import of more water is not entirely out of question as well, very long term.

And if "we" could be careful not to flood the low spots of the planet, then those low spots might have substantially higher "air" pressures.

I could blab so much more, but don't want to bore members too much.

Done.

Last edited by Void (2019-07-15 12:46:08)

Void · 2019-07-15 19:57:19

Well this is much the same thing, but apparently from NASA.
https://mars.jpl.nasa.gov/news/8459/wan … ould-help/

They cover several important points.

I will make a point now based on past posting and information provided in discussions and readings (Including the above).

The debate about solar cells vs. nuclear is probably moot long term. Granted, in the startup and until proven on the ground, this method might well be preceded by the use of solar cells and/or nuclear. However, if this concept works to make a pool of water on Mars generated by solar energy, then that is truly the way to go big time.

Be sure that I am not in anyway claiming other peoples works. I do admire them.

But I have been harping on ice covered pools of water for ages, on this site, and actually I believe on others as well. Some that are now defunct.

This aerogel is fragile, and in the article, they address that fact. I do not dispute that air pressurized greenhouses could eventually be constructed with aerogel as a component. Probably a good idea to move towards such a set of inventive technologies.

But if you read the article, the aerogel takes care of the U.V. apparently, and that is a really big thing I have searched for. And of course according to them it has very significant greenhouse effect properties.

A quote gives these estimated (Probably very accurate) capabilities on that line:

In an experiment conducted by lead author Robin Wordsworth of Harvard, 2-3 centimeters of silica aerogel allowed light from a lamp tuned to simulate Martian sunlight to heat the surface beneath it by up to 150 degrees Fahrenheit (65 degrees Celsius) — enough to raise temperatures on the Martian surface and melt water ice.

They appear to have their eyes on the Mid Latitudes to initiate this activity:

In a new paper in Nature Astronomy, researchers propose that a material called aerogel might help humans one day build greenhouses and other habitats at Mars' mid-latitudes, where near-surface water ice has been identified. The study was funded by Harvard University's Faculty of Arts and Sciences.

They mention the deepness of the Martian cold sink, at those latitudes, and of course it is at it's deepest in the winter:

The experiment explored a similar process with aerogel. The paper details how both a solid piece of aerogel as well as chunks of crushed aerogel can be used to heat the surface below. The researchers used varying levels illumination produced by Martian seasons. The results suggest aerogel could even provide a heating effect in the bitter Martian winter. In the mid-latitudes, winter nighttime temperatures can be as cold as minus 130 degrees Fahrenheit (minus 90 degrees Celsius).

Obviously then, instead of the winter being a famine of energy, this should be favorable to energy supplies year around at mid latitudes.

It does make a lot of sense to store your collected energy as heat, rather than to generate electricity, and then store it in batteries.
Instead, generate electricity 24/7, (Even in global dust storms), from passing heat from the reservoir into the surface heat sink.

Of course the aerogel is likely to be on top, since it gives the U.V. protection. Then you may put down a glaze, perhaps of some non-fluorine including plastic sheeting. This may yellow over time, but perhaps can be replaced after many years.

Then your next layer is a slab of ice. In the ice, you put tubing. This is a heat exchanger. There can also be heat exchangers in the air above, that minimize the blockage of sunshine, by their nature and positioning. And there can be higher temperature heat storage methods in the water under the ice.

Having the reservoir heat trap, you can generate water as warm as 39 F, without it turning over, the water under the ice would be -32 F.

(3.88888889 to 0 C).

In the past I have proposed the obvious notion of having a solar salt pond, working like an Antarctic Dry Valley lake.
https://en.wikipedia.org/wiki/Solar_pond
Quote:

Efficiency[edit]
The energy obtained is in the form of low-grade heat of 70 to 80 °C compared to an assumed 20 °C ambient temperature. According to the second law of thermodynamics (see Carnot-cycle), the maximum theoretical efficiency of a cycle that uses heat from a high temperature reservoir at 80 °C and has a lower temperature of 20 °C is 1−(273+20)/(273+80)=17%. By comparison, a power plant's heat engine delivering high-grade heat at 800 °C would have a maximum theoretical limit of 73% for converting heat into useful work (and thus would be forced to divest as little as 27% in waste heat to the cold temperature reservoir at 20 °C). The low efficiency of solar ponds is usually justified with the argument that the 'collector', being just a plastic-lined pond, might potentially result in a large-scale system that is of lower overall levelised energy cost than a solar concentrating system.

I would say that those heat values 70 to 80 °C, are well worth a look at on Mars. The warmer lakes in Antarctica get to about room temperature, even though the sunlight travels through thick ice, and overlying water.

I do not propose that all melted water should be treated that way. The amount of water ice is huge.
https://www.space.com/30502-mars-giant- … y-mro.html
Quote:

The ice the scientists found measures 130 feet (40 m) thick and lies just beneath the dirt, or regolith, or Mars.

And that one is said to be the size of Texas and California combined.

There is overburden to remove and use, and that will have salts in it.

The overburden can be relocated into the formed bodies of water, to make berms, the salt obviously to make solar ponds.
Yes there can be cold fresh water polders as well.

But has anyone tried underwater aerogel?

Some questions for that, would it endure? Would it be filled with water or air? Would it exist in the water in conjunction with other materials? What could it be good for?

Well, I don't know enough yet, but if something like that can be made functional, then you could make solar enclosures underwater. The easiest plan is to fill the enclosures with water. Filling with air, causes differential pressures, and then you must build with participating materials that may be expensive and might block the light.

Another version is that if you have your slab of ice over the polder with aerogel + other materials above it, you might put underwater aerogel + materials at the bottom of the ice. The ice slab would be pinned between the two. It would be preferred I expect to keep that ice slab nicely frozen. I did mention heat exchanger tubes in the ice slab, so now you know what that can be for.

Now you have an upper aerogel blocking U.V. and translucent, allowing solar flux in, and holding heat in. The ice itself is rather a good insulator, and also will if properly "Manufactured" allow the passage of light. And you have yet another layer of aerogel under the ice that is also translucent. So some light will get into the polder. And unless released heat will build up. You must then arrange to moderate the heat. One method would be to shade the surface, but why do that? Instead dump heat to the outside, and generate electricity. I am rather sure that such a polder could be at a comfy temperature for humans in minimal protective equipment. Maybe just swimming trunks.

Of course you want the ice to be not too thick, so it would be potentially deadly to swim up to the lower aerogel layer, without more significant protection.

Curious....What would happen if you added a solar pond to this setup? How hot might the bottom waters get, if you keep the water at the top of the polder at higher temperatures. Of course there would be limits, the higher the top water temperature, the harder to keep the ice frozen. But you could thicken the aerogel under the ice for more insulation, but of course then you may limit the passage of light into the water. So, experimentation will be in order.

So, I think we have power collection and storage figured out, and we also have figured out how to have electricity ~24/7, at our fingertips.

What about agriculture? Aquiculture of course is the easiest.

Air filled chambers for dry land plants will be harder. Glass I understand is rather weak when wet. So, I shy away from glass.

But we have.....

http://www.nemosgarden.com/

Essentially a diving bell, transparent greenhouse. And with temperate water, then you could swim to each one. No spacesuit required. Weights on your body though. Don't want to float up where the water pressure is low.

I will not say there will be no complications. For instance, if your slab of ice is perhaps 2 feet thick, (0.6096 Meters), then by Henry's laws, you have the problem that air from your diving bells will dissolve into the water, and then precipitate at the lower pressure "Water upper limits". So the bubbles. Interesting. Can bubbles be used as yet another translucent and thermally insulating device in this situation?

But you would have to arrange to limit the quantity. That is, you would need to vacuum the bubbles off and push them back into the diving bells. And the diving bells would be a reservoir(s) of breathable air, if you were on the ball. In a global dust storm, you would need to take measures to remove organic matter to a freezer, so that it would not rot and make the air useless.

I think that that is plenty for now.

Done.

Last edited by Void (2019-07-15 20:52:21)

Void · 2019-07-16 10:24:07

I have had some looking at https://en.wikipedia.org/wiki/Hydrophobic_silica

I would say, it is something to continue for consideration, in wet situations. However, it is possible that other items would serve well enough with less bother.

Bubble wrap for instance, but not just for cushion. A version with a smooth undersurface and yet air cells inside might do nicely for the under ice application. Once you have a water reservoir under this that has temperate water, then many other things could be done.

Biofilms might be a problem under the bubble wrap. That to solve either robotically, chemically, or with the assistance of predators of the biofilm. It would be good if they could actually breath air bubbles under the biofilm, precipitated out of the water. Don't know what sort of a rugged biofilm consumer could be found and tuned for such an environment, but this as well is worth a look.

Done.

SpaceNut · 2019-07-16 17:38:37

The three most common types of aerogels are silica, carbon and metal oxides, but it's silica that is most often used experimentally and in practical applications. When people talk about aerogels, chances are they're talking about the silica type. Aerogels are nanostructured, open porous solids made via sol-gel technology.

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

Since these are porous they are not meant for structural support...

https://www.graphene-info.com/graphene-aerogel

Aerogel is created by combining a polymer with a solvent to form a gel, and then removing the liquid from the gel and replacing it with gas (usually air). The high air content (99.98% air by volume) makes it one of the world's lightest solid material. Aerogels can be made from a variety of chemical compounds, and are a diverse class of materials with unique properties. They are known as excellent insulators, and usually have low density and low thermal conductivity.

So where would a battery designed with Graphene fit into an existing topic?

Terraformer · 2019-07-17 02:41:04

If they block UV, then we have more flexibility in the plastic we use on the inward size. Perhaps we could have a thin layer of glass on top to stop dust getting trapped, and then plastic on the bottom, with the aerogel sandwiched between. I would add the pressure layer separately, which would be basically a pressurised polytunnel, so if something goes wrong with that we can take it down without having to replace the entire structure.

We don't need much pressure for aquaculture, though.

Void · 2019-07-17 11:17:43

This seems to open many doors Spacenut and Terraformer.

Time to rant.

Um.....It seems to be said that the concept that they have would both block 60% of U.V. and 99.5 % of the U.V.-C believe. They then expect the potential under the aerogel, to be above freezing. In their view I guess this would be enough to grow unspecified plants.

Not so sure anymore if that level of protection will protect some plastics long term.

So, many factors to consider.

I had a lot to post, but my internet connection seems to keep dropping out. Perhaps I need more service to my situation, or perhaps their could be an intrusion factor. But I will choose to end it here.

Done.

Last edited by Void (2019-07-17 11:40:39)

Void · 2019-07-17 20:48:43

I seem to be back.

While I do like their work with aerogels, as it shows so much promise, I think that they constrain themselves, so far, more than they need to.

To grow a photo-organism, among the things beneficial are moisture, nutrients, beneficial light, and reasonable protection from harmful radiation, and toxins. They seem to have made some consideration a lot of that.

I would like to consider lichen, because it has been tested in partially Mars like environments. Also I think it can demonstrate where some of the loopholes and considerations can be for certain life forms, given some protections from the raw Martian environment.

Keep in mind that I am not serious about farming lichen on Mars any time soon. But I will suggest why it might be a pathway far down the road. And this example will help define some methods that can be used.

I believe that I have read recently that lichen is thought to have colonized land quite some time ago, and perhaps was the dominant photo-biological system for some time. So, it was very likely adapted to many very harsh conditions. We likely do not have all of the genetics available for those ancient versions, but it may be possible to get them back some day.

For Mars, the photo organisms that have a chance in the raw Martian environment now are certain lichens from Antarctica, and perhaps some Cyanobacteria.

So, technically that means certain Fungi, Algae, and Cyanobacteria.

But they are very limited as to where they might grow as demonstrated by the experiments. And I don't think that the experiments include a negative factor, which is toxic dust, or a potentially positive factor, which is the tiny amounts of O2 and CO. In the Martian atmosphere.

In the experiments they could not survive in direct sunlight, but could appear to do OK and even adapt and grow in cracks in rocks.

I think I know why. Beyond the fact that the U.V. was attenuated to 1/40th of surface flux, which is mentioned in some of the descriptions of the experiments.

Presumably they also got 1/40th of the amount of the amount of favorable photons. But the Lichen tested probably do not need that many useful photons. I presume that that is sufficient for their slow growth. Their slow growth is also limited, I think by access to nutrients, and also moisture. And so, it appears that on the budget they had, they could protect from U.V. at 1/40th the Martian surface flux, and could also repair any damage incurred.

So, if something like aerogel is used to provided an enhanced environment, depending on the "Crop", you would tune it for.
Passage of Good Photons, and Bad Photons. A plant can only use a certain amount of the good photons, so you can use attenuation to reduce the amount of good photons to needs. That will then equally reduce a similar amount of bad photons.

But the aerogel can also be modified, it seems, to block 60% of U.V. (Bad Photons), and included in that is 99.5% of U.V.-C, the most damaging photons.

So, you can use the filter process in conjunction with attenuation to reduce bad photons as much as is possible, while still passing enough good photons for the photo-organism to have optimal lighting conditions. (Within the limits of filtering and attenuation).

One thing I see that the experimenters with aerogel greenhouses seem to be fixated on is getting temperatures up, while filtering out some of the bad U.V. They believe that plants could be grown in the produced environment at that point.

But I feel that aerogels should be used for other purposes as well, specialized in their purpose. You could make an aerogel that passes U.V., to create maximum warming in a machine-greenhouse, and then because that subpart could provide extra heat, you could tune a photon filtering-attenuating aerogel to provide a much improved photo environment.

Back to Lichens. I think that a simple dome of aerogel could be placed over them that does filter and attenuate photons properly for the Lichens comfort. Spacenut has said that it is not a good building material, which is likely true.

A dome of aerogel could be given a strengthening by coating it with glass, I think.

I nominate vacuum deposition for that purpose. I just read an article about strengthening glass by 5 times by adding Nano-Particles.
They believe they can make it clear.

So, 5 times the strength of existing glass sounds good to me. And so these relatively small "Domes" could be placed over the Martian surface. They would not need pressurization. They very well may act like solar stills.

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

Moisture is believed to move into and out of the Martian soil in the night/day cycle. So, the dome being warm in the day should suck moisture out of the soil during the day. Some experimenting would be needed to find out how to generate 70%-100% Relative Humidity at some time of the day. That apparently is sufficient for Lichen to get their water.

…..

In the far future, I will hope that Lichen can be created that has significant nutrition, and can take nutrients from nutrients supplied by humans, and a Lichen with a much more speeded up metabolism so that it can grow fast. That is not so far fetched, because vascular plants have symbiosis with Fungi in the soil. Plants could not get their nutrients without help from Fungi, nearly as well. And as it happens one part of Lichen is a Fungi. So, I don't think it is beyond thinking about. Reindeer Lichen is marginally a food now. It could not make it unprotected anywhere on Mars now I would think, but with the dreaded GM, we might hope to make a crop out of Lichens some day that can be grown with the assistance of the domes I have suggested.

Ideally the new type of Lichen could also Breath O2 from the atmosphere, and Eat CO from the atmosphere to assist it's metabolism. Fungi are good at breaking down organic matter, and I suspect that early Fungi on the land did just that on the Earlier Earth, if their was a lesser Ozone layer, and lots of CO2 in the atmosphere. Photolysis may have driven the life cycle of some Fungi just under the surface on Earth a long time ago.

……

Now away from Lichen.

For "Polders" in the ice sheets bounded by regolith berms, and with some covering including aerogel, we can choose several photo pathways.

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

Polder Type #1
If you want to capture heat, then a thin aerogel with no U.V. protection. Likely this is only for collecting heat. To retain the heat in winter, then you might prefer to make the aerogel thicker, and tolerate some attenuation.

Polder Type #2
If you want to grow photo-organisms, then you make sufficient filtering-attenuation, to promote those plants. But for that polder, you may have a hard time melting it sufficiently. However if you can extract heat from Polder #1 and import it to Polder #2, you can have your cake and eat it too.

If we want to, we could make Polder #1's very salty to make them into solar ponds. That would be fine, as the U.V. would penetrate quite far down, and give it's energy to the water as vibrations, as so would the "Visible" light.

For Polder #2's, something else may be done.

This task splitting would allow the method to go to higher latitudes, I think, as Polder #1's are specifically maximized for heating.

I think that's enough for tonight.

Done.

Last edited by Void (2019-07-17 21:38:52)

kbd512 · 2019-07-17 21:14:04

Void,

What if we used this technology to supply some of the astronauts' food requirements both on Mars, and in-transit, with flavored powdered shakes that infuse Spirulina grown in space?

Even if we only replaced 1 meal per day, say a protein / energy smoothie for breakfast after your daily workout, that would be an enormous mass / energy / cost saver. Making energy is important, but we already have lots of well-developed technology for that. Even so, improved energy production would be really important. Never running out of fresh food would be a true game-changer, though. If we could grow proteins, fibers, and nutrient rich microorganisms at the scale required, then we could live in space indefinitely with artificial gravity.

Void · 2019-07-17 21:18:25

I certainly agree with you kbd512. Aerogel should be super insulating in space, and so light.

I like it a whole lot

Done.

Last edited by Void (2019-07-17 21:39:19)

tahanson43206 · 2019-08-25 14:01:16

In reply to void re post #1 of this topic ...

A (surprising to me) report appeared in today's local paper. I had to hand transcribe it. The quote will be given below.

The report appears to show that a way has been found to use simple sunlight and to separate water from sea water for drinking. While the intended application appears to be needy persons on Earth, I'm wondering if the technique would be useful for thirsty persons in space vehicles, or on planets other than Earth.

It DOES appear (as I read the report) that gravity is a factor in the design, but whether it contributes to the success or detracts from it is not clear (to me).

From Tribune Media Services
Author: Steve Newman
Published Sunday 2019/08/25
Section: Earthweek
Segment: Water to Drink

A team of Chinese and international researchers say they have developed an inexpensive solar-powered “tree” to remove enough salt from the sea’s water to provide clean drinking water for at least three people per ‘leaf.”
The scientists say the tree “roots” are made of cotton fibers. They soak up water and send it up a metal stem, where leaves made of blackcarbon paper convert sunlight into heat. After the water is heated by the leaves to nearly 122 degrees Fahrenheit, the resulting water vapor is cooled and condensed back to fresh water. The technology could be deployed in small communities to ease water shortages.

(th)

SpaceNut · 2019-08-25 15:30:32

Solar driven heat evaporation while its sliding down a cooler surface to be collected as fresh water. Another flavor of a solar stil with a contaminant filter.

Back to aerogel in that its mass is due to it being porous which in an atmosphere of bubble within make the transfer of energy through it less than a solid version of the same materials.

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Highly Transparent Aerogel/Getting more heat out of sunlight

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