Solar Heliostat System with Molten Salt Bath, and Liquid CO2 Method.

Void · 2017-02-12 21:15:28

You have to like this. It should work for Mars I would think. Maybe better than for Earth.

http://www.gereports.com/this-scientist … ectricity/

Who doesn't love a collection of solar heliostats and a solar tower picture?

This Scientist Has Turned The Tables On Greenhouse Gas, Using CO2 To Generate Electricity

Top image: A solar thermal power concentrates heat from the sun to boil water and use the steam to generate electricity. Image credit: Getty Images Above: A life-size prototype of GE’s “sunrotor” on a shelf at GRC. This 10 megawatt prototype is the basis for the full-scale system which stores 100 megawatt-hours and generates power at 33 megawatt, Sanborn says. Image credit: GE Global Research

Solar power is a great source of renewable energy, but as with many things in life, timing is everything. The sun doesn’t shine on long winter nights when people turn on their lights. On the other hand, a sunny Sunday afternoon can produce an ample electricity surplus that’s difficult to store.
“That’s the grand challenge,” says Stephen Sanborn, senior engineer and principal investigator at GE Global Research (GRC). “We need to make renewable energy available to the grid when it is needed.”
Sanborn and his team decided to solve this problem by storing some of the heat generated by thermal solar power plants in carbon dioxide. These power plants concentrate solar rays with vast fields of mirrors and use the heat to generate steam that spins a turbine. The carbon dioxide effectively works like a battery that can quickly release energy during peak demand.
The irony, of course, is that CO2 is the prime contributor to climate change, and the reason the world is switching to renewable energy in the first place.
The work is part of a research partnership between the GRC and the U.S. Department of Energy. Sanborn says the solution could revolutionize the solar power industry and also make natural-gas power plants more efficient.
Top image: A solar thermal power concentrates heat from the sun to boil water and use the steam to generate electricity. Image credit: Getty Images Above: A life-size prototype of GE’s “sunrotor” on a shelf at GRC. This 10 megawatt prototype is the basis for the full-scale system which stores 100 megawatt-hours and generates power at 33 megawatt, Sanborn says. Image credit: GE Global Research
Here’s how it works. The design has two main parts. The first one collects heat energy from the sun and stores it in a liquid of molten salt. “This is the hot side of the solution,” Sanborn says. The other component uses surplus electricity from the grid to cool a pool of liquid CO2 so that it becomes dry ice.
During power generation, the salt releases the heat to expand the cold CO2 into a supercritical fluid, a state of matter where it no longer has specific liquid and gas phases. It allows engineers to make the system more efficient.
The supercritical fluid will flow into an innovative CO2 turbine called the sunrotor, which is based on a GE steam turbine design. Although the turbine can fit on an office shelf (see image above) it can generate as much as 100 megawatts of “fast electricity” per installed unit—enough to power 100,000 U.S. homes.
Sanborn believes that a large-scale deployment of the design would be able to store “significant amounts” of power —— and deliver it back to the grid when needed. “We’re not talking about three car batteries here,” he says. “The result is a high-efficiency, high-performance renewable energy system that will reduce the use of fossil fuels for power generation.”
He says the system could be easily connected to a solar power system or a typical gas turbine. The tanks and generators could fit on trailers. His goal is to bring the cost to $100 per megawatt-hour, way down from the $250 it costs to produce the same amount in a gas-fired power plant. “It is so cheap because you are not making the energy, you are taking the energy from the sun or the turbine exhaust, storing it and transferring it,” says Sanborn.
The process is also highly efficient, Sanborn says, yielding as much as 68 percent of the stored energy back to the grid. The most efficient gas power plants yield 61 percent.
The team is now building a conceptual design, which Sanborn believes could take five to 10 years to get from concept to market.
GE is also looking at other commercial applications that could be made available sooner. One such utilizes the waste exhaust heat from a natural gas generator. Sanborn says the solution could make gas-fired power plants 25 to 50 percent more efficient. That, he says, would be a major environmental benefit, because it would significantly reduce the overall CO2 emissions per kW hour of electricity produced by gas-powered plants.
Sanborn’s included in his team turbine experts, thermal engineers who understand refrigeration, heat-transfer scientists, chemical engineers who know how CO2 behaves and energy-storage experts. “We call all this expertise we have at our fingertips the GE Store,” he says. “It would be very difficult for me to do everything that this research calls for without that deep expertise of people available at GE.”

It sounds like they are relatively sure of the outcome, but it is not a done deal yet. Since we have covered the topic of generating dry ice on Mars, and this concept uses it, I should think that this is an item to watch in the future.

*Note #1: If you have supercritical CO2, you can do some industrial processes with it.
-That can also extract some types of metals from ores. (You can look it up).

Note #2: I see that the power tower seems to be incandescent.
If the Molten salt is also incandescent to the point of emitting Near Infrared, then perhaps a form of photosynthesis could be supported by the infrared photons. That being done without the use of a transparent glaze greenhouse which also holds back a differential pressure.
https://en.wikipedia.org/wiki/Chlorophyll_d

Chlorophyll d is a form of chlorophyll, identified by Harold Strain and Winston Manning in 1943.[1][2] It is present in marine red algae and cyanobacteria which use energy captured from sunlight for photosynthesis.[3] Chlorophyll d absorbs far-red light, at 710 nm wavelength, just outside the optical range.[4] An organism that contains chlorophyll d is adapted to an environment such as moderately deep water, where it can use far red light for photosynthesis,[5] although there is not a lot of visible light.[6]

Last edited by Void (2017-02-12 21:39:02)

Terraformer · 2017-02-13 04:54:51

Interesting. Given that on Mars land isn't going to be in short supply, I wonder if it could be simplified at the cost of lower efficiency?

elderflower · 2017-02-13 05:18:40

Prolonged dust storms are going to reduce output of solar energy collectors, of any type, for long periods.
Energy storage systems for earth use are designed for short period, high output, fast response to back up grid power. These enable a reduction in rolling or hot stand by capacity, which saves grid suppliers a lot of energy.
At Mars we will need diverse supplies, not only solar, and the only practical means of supplying large quantities of power will be nuclear fission (until someone gets fusion machines to work).
The ramp up time of fission reactors is fairly long, so a sudden demand would need to be met from a storage unit, maybe like the one described. For long term outages multiple reactors will be needed.
It might also be possible to find geothermal sources which could be developed, but that isn't likely in the short term as it takes a lot of drilling.
It would, maybe, be best to land reactors before peopling a base to ensure that the fission fuel rods/pellets are safely landed before the people arrive.

louis · 2017-02-13 08:21:19

Given a Mars Missions are going to cost billions of dollars, the cost of the energy system is really not a very significant factor. Continuity of supply is of course a major issue - but it might be easier to simply manufacture methane, which is very versatile (can be used for industrial process, rocket fuel and electricity generation).

However, this is certainly an interesting application on Earth. I am amazed a turbine so small can generate such a large amount of electricity.

Terraformer wrote:

Interesting. Given that on Mars land isn't going to be in short supply, I wonder if it could be simplified at the cost of lower efficiency?

Oldfart1939 · 2017-02-13 09:19:02

Solar power on Mars should be regarded as the backup to nuclear and in the future--geothermal. The original Mars direct scheme published in Zubrin's book called for a 100KWe nuclear plant, but in view of the weight reductions since then, we could suggest sending 2 of them at just a bit over 1 metric ton combined.

The 4 essentials for Mars: (1) Shelter, (2) air, (3) food & water, (4) adequate power.

Even the overly dramatic National Geographic "Mars" series had an episode based on a power shortage brought about by a massive dust storm--and yes, the nuke plant was "offline" due to another inconceivably stupid decision. Duh!

SpaceNut · 2017-02-13 12:42:40

solar heliostats efficiency
https://energy.gov/eere/energybasics/ar … wer-basics

http://www.practicalsolar.com/technology.html

The mirrors on Practical Solar heliostats have minimal reflection loss, so each heliostat reflects approximately its area in sunlight: about 1 kilowatt of heat per square meter. As a frame of reference, a typical electric space heater produces 1.5 kilowatts of heat. If one hundred Practical Solar heliostats, each with 2.2 square meters of mirror area, direct sunlight onto a single thermal receiver, the sunlight will be converted into 220 kilowatts of heat.

Each mirror must track the sun and reflect to the tower something simular to this...

Mars gets about 430 w/ m^2 on the surface which means a huge number of panels over an even greter area to create the same levels of power.

Void · 2017-02-13 13:30:44

It is a contender, something to watch.

Static solar cells vs heliostat tower. Answer is we don't know yet. It is unknowable at this point because we have not yet defined what Mars has to offer, or what technology will most implementable at the various points of Martian habitation progression.

I think Oldfart1939 was close to my thinking. I alter it a bit though in a speculative manner.

I see Thorium reactors as being the "Base" power supply. Multiple ones actually to assure that when things go wrong with the weather, you have survivable options. Then you might ask "Why can't you just use Thorium reactors?"

Well if they are the most cost effective, then indeed, why not?

But if a type of solar offers a lower cost, then it would need to be considered for integration into a power system.

Which brings the question "Why don't we just use fission nuclear on Earth?". Well, I presume the power companies are not stupid, the answer must be that other power sources are competitive.

The answer is I don't know if fission Nuclear should be the only power source.
https://www.iaea.org/newscenter/stateme … lts-europe

However I do know that it is far too early to be making decisions without as one of our members might put it "Ground Proof".

So, this option can be considered, and also criticized.

My own opinion is that the "LOAD" for Mars is virtually infinite at this time.

That is the demand for power.

Yes a frugal approach meters what your settlers will need. But what they will want will be far more.

From the original post, a link:

His goal is to bring the cost to $100 per megawatt-hour, way down from the $250 it costs to produce the same amount in a gas-fired power plant.

That's a goal not an achievement. But if achieved, then I have to suppose that since it is a greatly reduced price, it also is significantly below the price of nuclear fission. We can't be sure about that though. Maybe nuclear fission will be cheaper on Mars.

Anyway not having all your eggs in one basket (Avoiding specialization) is typically a good philosophy.

So at this point not having more information, I include the following possible contenders.
-Nuclear Fission
-Solar Cells
-Solar Thermal (Heliostats)
-Possible methods to tap into the Martian atmosphere (CO + O2) (Highly speculative).

Now as for this "LOAD".

That includes:
-Continuity based survival needs.
-Material goods desires.
-Created and stored survival resources.
-Terraforming.

With the first three of the list, the "LOAD" is very big.
With the last included (Terraforming), the "LOAD" is virtually infinite until Mars is Terraformed.

So although I am in favor of fission Nuclear. I do not have confidence that it will be sufficient to address an infinite energy "Load" desire.

We don't have sufficient information at this time. Therefore we should not be killing 3 out of 4 children based on first impressions.

Last edited by Void (2017-02-13 13:51:29)

louis · 2017-02-13 14:55:46

I don't agree. We've had several very successful solar powered rover missions.

Solar is very flexible - you can split it up if you need an auxillary supply at a mining operation say. The Rovers never stopped generating electricity due to dust storms incidentally. I think about 20% of (seasonal) standard input is the lowest they go.

PV panels can be pre-delivered to the base site and used to manufacture methane, which can be used as power booster in the event of dust storms.

Oldfart1939 wrote:

Solar power on Mars should be regarded as the backup to nuclear and in the future--geothermal. The original Mars direct scheme published in Zubrin's book called for a 100KWe nuclear plant, but in view of the weight reductions since then, we could suggest sending 2 of them at just a bit over 1 metric ton combined.
The 4 essentials for Mars: (1) Shelter, (2) air, (3) food & water, (4) adequate power.
Even the overly dramatic National Geographic "Mars" series had an episode based on a power shortage brought about by a massive dust storm--and yes, the nuke plant was "offline" due to another inconceivably stupid decision. Duh!

SpaceNut · 2017-02-13 16:18:41

One could always lay out the panels to create shelter areas but it does take planning as to align them before trying to frame a stationary location for best recieving energy levels.

The energy deficit which starts for mars distance is roughly 600 w /m^2 at the planets orbital cycle when compared to earths.
Nuclear for that reason would be top on my insitu list to develope with the Thorium which seems available. Supplementing any energy source is also a plus whether this be by solar of any type or via geo thermal but if we struggle to get to the magma domes here on earth mars will not be any easier.
We recently did drill near Iceland about 3 miles for a thermal pocket to create energy with.

Void · 2017-02-13 18:21:07

Alright I return with more patience.

Yes I took a look at the current comparative values of Solar Power Towers and that of Solar Panels.

As spoken above here on Earth at this time the Solar Panels may be a bit more cost effective. This leads me to wonder why anyone bothered to build a solar power tower in Morocco.
https://en.wikipedia.org/wiki/Solar_power_in_Morocco

I guess I will give you the benefit of doubt and suppose that the people who built it were stupid, or unaware, or Solar Panels have subsequently become less costly.

Quote:

Mars gets about 430 w/ m^2 on the surface which means a huge number of panels over an even greter area to create the same levels of power.

Important information, but it applies to all solar devices on Mars equally I might think.

U.V. Light Spectrum, there is some on Earth, much more on Mars:
Now not as obvious is the spectrum of light on Mars, and how a solar collection device can use it.
https://en.wikipedia.org/wiki/Solar_cel … olar_cells
Quote:

UV solar cells[edit]
Japan's National Institute of Advanced Industrial Science and Technology (AIST) has succeeded in developing a transparent solar cell that uses ultraviolet (UV) light to generate electricity but allows visible light to pass through it. Most conventional solar cells use visible and infrared light to generate electricity. Used to replace conventional window glass, the installation surface area could be large, leading to potential uses that take advantage of the combined functions of power generation, lighting and temperature control.
This transparent, UV-absorbing system was achieved by using an organic-inorganic heterostructure made of the p-type semiconducting polymer PEDOT:PSS film deposited on a Nb-doped strontium titanate substrate. PEDOT:PSS is easily fabricated into thin films due to its stability in air and its solubility in water. These solar cells are only activated in the UV region and result in a relatively high quantum yield of 16% electron/photon. Future work in this technology involves replacing the strontium titanate substrate with a strontium titanate film deposited on a glass substrate in order to achieve a low-cost, large-area manufacture.[16]
Since then, other methods have been discovered to include the UV wavelengths in solar cell power generation. Some companies report using nano-phosphors as a transparent coating to turn UV light into visible light.[17] Others have reported extending the absorption range of single-junction photovoltaic cells by doping a wide band gap transparent semiconductor such as GaN with a transition metal such as manganese.[18]

OK so there is some work on using UV wavelengths in a special solar cell type. But...
That would be for the UV wavelengths that get past our Ozone. How would it work for the UV spectrum of Mars? Don't know. Probably not tuned for it. Maybe I lack information here. Perhaps NASA has full spectrum solar cells. But then they would likely not be at the same cost level as normal ones. Maybe transport cost from Earth to Mars is all that matters at first, so you don't care.

I guess I will simplify the argument and leave the burden of proof to you guys that solar panels can be obtained for transport from Earth to Mars at a reasonable cost, that will use all the available spectrum. So for the case of imported solar panels perhaps it is the way to go. Particularly because a solar power tower has to be designed to a total size....#of Heliostats, size of tower.

I believe that a solar power tower would likely make use of the spectrums from infrared through visible into far U.V. And the far U.V. is the most energy intensive. That's why it is so lethal to life.

U.V. Summary:
Although the light on Mars is attenuated relative to that of Earth due to a greater distance from the sun, on Mars the sunlight offers more U.V. which may compensate, if your collector can collect as much of the suns delivered spectrum as possible. So this is another contentest between Solar Panels and Solar Power Towers.

Building additional power capacity:
*Although the argument for initial solar panel import may be quite valid, building additional power production capacity raises issues in my mind.
Building solar cells with 3D printing? Maybe.
Building Heliostats with 3D printing? Maybe some parts.
So, it is a Maybe on which is easier to build, it will depend on your available materials, and your technological skills.

But an issue comes up "Copper or Aluminum conductors?".
I believe that the heliostats can be constructed to run on liquid CO2 motors. They will need WiFi communications, or we might want them to have it, but they will not need Copper or Aluminum.

I see you have posted Spacenut, so I will start another post. Thanks for replying.

Last edited by Void (2017-02-13 18:49:10)

SpaceNut · 2017-02-13 18:44:11

The thermal uses near Infrared wave lengths in the light spectrum for the concentrators but it sure would be nice if we could harness the UV legnth on Mars as I thinks these are more intense.

This is also related to solar chinmey talked of here and other such concentrating efforts.

Void · 2017-02-13 18:52:45

Thanks Spacenut.

I will point to another issue. The cold of the Martian night. I recall some members, particularly Antius and perhaps GW Johnson and others discussing this.

Granted this also segways into energy storage devices, so there will be a cost.

If we can generate Dry Ice by a method on Mars, then we can take advantage of the system described in the original post. I will re-acquire that reference.

http://www.gereports.com/this-scientist … ectricity/
Quote:

Here’s how it works. The design has two main parts. The first one collects heat energy from the sun and stores it in a liquid of molten salt. “This is the hot side of the solution,” Sanborn says. The other component uses surplus electricity from the grid to cool a pool of liquid CO2 so that it becomes dry ice.

The Martian Case:
On the hot side we hope for an advantage, using U.V. along with visible and infrared.
On the cold side we are expecting a massive advantage due the deep cold of the night.

And in the system we have two methods of storing energy.
1) Hot Salts.
2) CO2 Condensate, (Dry Ice preferred).

***If we are going to store energy for solar panels, we must include that as an extra cost of solar panels.

I really am actually with most or all of you in that for startup, we must want to consider solar panels as the primary method.
But then the method of this article looks very attractive to me as an in-situ method to generate massive amounts of energy, and to have some energy storage capacity.

A very nice addition to that system would be Thorium Reactors. Otherwise if Thorium Reactors are cost effective, and there is enough capacity from Thorium to support all the human wants and needs, then forget any solar.

But, I think that likely Thorium Reactors should be the base energy supply, and some type of solar to supplement it. I think this system looks pretty good, as both the solar power tower and Thorium Reactors may likely work with salts, and another plus, is that you might want to incorporate the dry ice cold side into your Thorium Reactor method as well.

So, you have the suns heat, including U.V. and all the way down to the very cold of the Martian night.
And you can link this to Thorium Reactors both through electrical grid, and hot and cold processes.

Quite an opportunity I think.

Last edited by Void (2017-02-13 19:07:14)

SpaceNut · 2017-02-13 20:18:44

Liquified pool of C02...means quite a bit of pulling in of the atmosphere before we can use the systems heat and cooling to create power at or above the 60% level as indicated in the initial post. The cooled Co2 is like storing the energy as if its the battery allowing it to heat and push the turbines blade as the solid goes into the gaseous phase under pressure increase.

http://nvlpubs.nist.gov/nistpubs/jres/1 … 81_A2b.pdf

Void · 2017-02-14 07:26:49

Well, they mention a liquid pool of CO2, and a phase change to dry ice in it.

I have to speculate that what they do is quench the output of the turbine into the liquid, and the liquid in turn converts some of the dry ice into more liquid CO2. So, it is a "Closed Loop". You would not be venting to the atmosphere. Yes you would have to gather a sufficient quantity of liquid CO2 system fill before you could use it properly. But as it happens, most of the atmosphere of Mars is CO2, and what is left over after the collection process will be useful as well, Nitrogen, Argon, and perhaps some other things.

As a strategy, it makes lots of sense to me. However I do not feel compelled to provide specific proven tactics at this point for a device specific to use on Mars. I would like to know more about the device they are proposing to use on Earth.

I will speculate on tactics however. I am inclined to suppose that some form of refrigeration would present a gas heated by pressurization to radiators on the Martian surface. Heat would be lost through the radiators. The return would then be used to convert liquid CO2 into Dry Ice.

Exactly when this would be effective? The night I presume. And I would not rule out it's use during the day, if your radiators can be shaded from the sunlight, and particularly if you are at a higher latitude.

Obviously this will be an active process, not some simple passive cooling of liquid CO2.

Last edited by Void (2017-02-14 07:32:38)

SpaceNut · 2017-02-14 20:25:45

The nightly mars cooling loop to make the tank liquify would not be all that much as that is a radiator exposed to the night air and then circulated into the tank to prelower the internal temperature, making for less energy from the solar convertor to make it to a frozen state.

Earth does not have that natural nightly temperature drop to prelower the liquid temperature so it requires more energy to achieve the stored energy battery effect the article discribes..

Void · 2017-02-15 11:37:21

Its at a strategic planning point I would think, and if it has value, then technological methods that work best on Mars will be worth looking into, as I think you have suggested.

SpaceNut · 2019-07-14 16:45:34

Repost of making reflective panels.

SpaceNut wrote:

The things that we could do with a slightly used heat shield seems to come to mind with your posts Void so as to turn them into a solar concentrator if the ship (BFR) is never going to return home.
The pica parts could be cut and reshaped into a focal point for such a device. Coat the surface with anything to produce as shiny as you need to reflect the solar. Sort of reminds me of the helistatic furnace hot salts which you have meantioned quite often sp as tpo create power.
I agree that if its not going to return home that we do reuse the engines, tanks and anything else for other purposes....

SpaceNut · 2019-07-14 16:48:18

Repost of process that makes a reflective surface.

Void wrote:

We have seen this before, but I know some members want to have real footing with things that are perhaps emerging as relatively new.
https://www.space.com/nasa-spacecraft-m … dings.html
I am pretty much interested in the shape.
And I have read the recent posts, so I am aware that much of what I might say has already been mentioned in some manner. That could be a good thing, as in this case my level of speculation, may be considered reduced from the normal.
Vapor deposition, and 3D printing methods are attractive I think, perhaps to make big heat shields, (not inflatable), in orbit or on the Moon.
I am tempted to hope that perhaps these could have so much surface area, as to reduce the dire stresses placed upon the heat shields.
I guess, at the start, I would wish for a large stainless steel make. Just because SpaceX is using stainless steel. It's the in thing to start with.
But I suppose that after you had a durable structure, there would be nothing wrong with thinking of coating it with a ceramic ablative material. I know that Josh and others have discussed such elsewhere (I couldn't find that section).
I would think that if you did have a method to do it in orbit, it might be OK to get your main structural materials from Earth, at least for some time, but then perhaps in conjunction with extracting Oxygen from Lunar materials, you could add the ablatives as from the Moon materials.
…..
I am thinking about the reusability emphasis that SpaceX has, but contrasting it with disposable, and I hope re-purposed structures, these for Mars.
I got the impression that GW indicated that these types of heat shield structure might top out at some upper size. I don't know how big that would be.
At this time my impression is that NASA is just trying to do it at all with inflatables. And that is good. In that case I believe a one time use, and then throw away, because it would be charred.
I like the NASA layout. It implies that you can put a knock off of the Starship behind it. That Starship would then not require a heatshield on the ship for all cases. I presume you could dispose of some of the air braking mechanisms as well. Legs for landing I suppose are an issue, but that would be figured out after you were sure what you wanted to have for a total structure.
I guess what I would want to justify such a process, would be that you could get useful gain by re-purposing the heat shields on Mars. Scrap metal would be an option if nothing else. However I would be much nicer if you could in some cases re-work the structure into something useful.
One possibility, I suppose would be a solar tracking device. Either solar panels inside the cone, or actually doing something to capture energy in other manners. For instance, it is not the proper shape for a solar concentrating mirror, but perhaps working in that direction.
Else, maybe just blacken the inner surface, and put a glaze over it, something that can put up with U.V.
I don't know if the heat shield could be in the shape of a parabolic circular mirror, but if it could that might be useful.
The outer edge might function like a wheel, and roll on a properly made base surface. Of course you would have to include mechanisms to drive it, but it could follow the sun to some degree. It might need a tilt capability to aim at the suns position above the horizon, in addition to being able to roll.
Maybe scrap metal would be the only real use, but whatever the use, then I might think that such an option can be considered as to how it might help a Mars civilization grow.
I do understand why SpaceX wants Starship to be multi-capable, but I also think that there could be a good use for a one-way-piping of materials to Mars. Of course, I have presumed that a variation of Starship could launch back to orbit without the heat shield, and I guess to be used again for Mars it then needs a new heat shield that I suppose would be appropriated in Mars orbit. They could be stockpiled in orbit I am thinking. As for a return trip to Earth, then I suppose you would need a version suitable for that as well. There are always trade offs I guess. However, most mass should be going to Mars, not to Earth.
Talk is cheep.
Done.

SpaceNut · 2019-07-14 16:51:12

Void wrote:

I guess I made a mistake and left this out of my post #36. Was in a hurry to shut down my computer, as it was behaving very slow, constipated, and strange. Not the first time when I have been posting on NewMars where that happens. Does not happen for me anywhere else.
This apparently is the source for this:
https://www.permanent.com/index.html
https://www.permanent.com/space-industr … ition.html
Quote:
§ 4.7.1 Vapor and Droplet Deposition in Vacuum
Vacuum vapor deposition in space utilizes an electron beam to vaporize a metal sheet, billot or ingot target, and the vapor sputters off onto a mold, or is manipulated by a magnetic field to paint a mold. Parts of any shape can be made with great ease, speed and purity, using electron and particle beams. This will work much better in the vacuum and zero gravity of space.
Aluminum sheet and steel sheet have been commercially produced on Earth by vapor deposition despite the costs of creating a special environment to minimize oxygen embrittlement. (Of course, in the vacuum of space, there's no problem with oxygen embrittlement.) Electron beam guns have also been used to coat millions of square feet of architectural glass each year. "Extensive work has been done on developing high rate physical vapor deposition of metals and alloys and evaluating the mechanical properties of metals so deposited. ... [R]esearchers [have] determined that the mechanical properties of vapor deposited metals and alloys can be comparable to those of the same metals made by casting, rolling and annealing." (General Dynamics report) Thus, many standard Earth processes for deforming material by application of large mechanical forces can be replaced by vapor deposition in space.
Droplet deposition is a relatively new technique on Earth used to make unique parts, as opposed to mass produced parts, without using a mold, by adding small increments of material to an existing structure, slowly building it up into any shape desired. Machines are already available which do this by programming, using plastics, and are used to make prototypes for product development. Indeed, they have opened up a whole new industry called "rapid prototyping". It has been pointed out that there are advantages to doing this in zero gravity and without air. As of 1992, commercial droplet deposition was using only plastic, but a number of companies were working to develop rapid prototyping machines able to make metal and ceramic prototype products. This process is related to "shape welding" or "shape melting" whereby layers of weld material are fed and built up. This method has been used to make vessels up to many tons in mass.
The energy for all these processes to melt or vaporize the metal can be direct solar oven heating or electrical heating (induction, resistance, or electron beam).
Droplet deposition is slow, whereas vapor and spray deposition is fast. The process used depends upon whether the product is mass produced (justifying a mold) or unique. Droplet deposition lends itself to computerized design so that producing a new product just means reprogramming the computer to move the droplet depositor in a different sequence. Droplet deposition requires less power and lends itself to simple, flexible robots sent out to perform tasks without being in a great hurry.
One such company, Incre, Inc., has produced products by incremental droplet deposition using aluminum and other metals, presented a paper on the technique at the 1993 SSI/AIAA Princeton conference, and mentioned plans to do work with nickel and steel alloys such as is found in asteroidal metal.
So, where I am going with this, is yes because of needing to get through the troposphere in a small package, an inflatable is the beginning.
But I can see where Starship, and this technology of a wide heat shield can move in a progression.
As soon as Starship is up and running smoothly, I see no reason why the equipment and raw materials for it's use, cannot be put into orbit.
A block of metal will also have a compact character, like an inflatable needs to. So, you then build your heat shields in orbit. While I did suggest a variation of Starship to be coupled with such a heat shield, of course some other propulsion system could be used, perhaps.
I really do think I understand why SpaceX is focused on being able to make the generic Starship that can do it all. But of course that is already not true. They are already specializing plans for a sub-orbital people mover.
Others have pointed out that Starship, is an atmospheric transit device, which by refueling, can be made into a civilization transfer device. (GW, I believe for one, Dr. Zubrin for another). As such it makes the most sense to move loads to orbit, couple them to heat shields, and provide an interplanetary propulsion, and landing propulsion. If it is a variant of Starship, then it could make a number of passes to Martian orbit, without a heat shield, to pick up loads.
The idea of reusable hardware, has great value, but I think it is best suited to well developed infrastructure situations. Of course because we would not want to discard the "Raptor?" engines with one use, then we want to get them back into orbit, to bring down another load. But if the heat shields can be manufactured so as to serve their purpose, and also then serve a purpose on the surface of Mars, then why lift them back up, through the gravity well, and atmosphere?
So, then the notion here moves to what useful purposes could you use. How could they be useful structure.
And so I sort of deviated from the cone, and hoped for (Edited)>a convex heat shield with an opposite side concave mirror, as a possible repurpose of the heat shields.
Other things would be to reuse the metals themselves.
And the chalk board is open for other notions on what to do with heat shield structures.
Of course our hopes are that some day, all necessary metal processing can be done on Mars, including sourcing the metals from ore, but there is going to be a progression. And if you feed the right materials into the growing infrastructure at the right time, then you facilitate greater chances of economic success.
More:
https://en.wikipedia.org/wiki/Electron- … deposition
https://www.researchgate.net/publicatio … vaporation
So, for such heat shields, the asperation would be to start by using metal stocks from Earth, as I anticipate, that it will a fair time before they could be sourced from the Moon.
But I think that after you had a metal shell, it may be that a ceramic like material could be deposited over it. My hope is that in fact some types of Lunar material could be deposited, and just maybe also Oxygen could be released in the process. Oxygen to put into Starship(s) of various types, Oxygen sourced from the Moon materials.
Obviously I am a novice at all of this. But if you could get Oxygen from the ion beam process, and also deposit something of a refractory nature onto the heat shield, that would of course be going in the direction desired.
Done

SpaceNut · 2019-11-26 23:02:17

The tower works on solar concentration by multiple mirrors or reflective surfaces so if you can not build big how about something smaller that still can produce a media that can be used later...

DIY linear Fresnel reflector array collects and transforms solar energy into steam up to 250º Celcius

http://topdiysolarpanels.com/fresnel-so … tt-system/
Fresnel Solar Power – Six Kilowatt System

This is going to make solar affordable for everyone.
This is a very standard prototypes solar furnace made of lens for all recycled big screen television.
I placed it in little bit frame, near the focus here we have a heat collector and a heat exchanger we can run water through to generate high pressure steam.
We can generate approximately 1.2 kilo watts of heat energy for this lens. This is about 60 inches (1.52 meter) in diameter using nothing but sunlight. This is a basic solar thermal generator I have come up with.
We are getting about 60% of electrical conversion efficiency and hot water is a free bonus, something you can’t get from Solar Panels, or you will need to get a Solar Tracker device to boost it up.

http://www.redrok.com/NewtonSolarSteamManuscript.pdf

SpaceNut · 2020-11-17 18:28:47

kbd512 wrote:

Terraformer,
Alternatively, we use solar thermal with abundant molten salt or molten Silicon and SCCO2 gas turbines. That way, we don't need ridiculous quantities of batteries that rapidly degrade over time and have to be continually refurbished or replaced. Given that the molten Silicon is in the 500Wh/kg range, that seems far more practical than 100Wh/kg batteries that require asteroid mining to obtain the necessary materials. I still think we should go there to retrieve those metals for other uses, but energy production should use cheap / readily available / easily recyclable materials like high temperature ceramics, high grade steels, salt / sand / CO2 for heat storage / power transfer, etc. We're never going to run out of that stuff, on Earth or most other places, for that matter.

I was surprised at the temperature and pressures that molten salt occurs at in typical use.

https://www.asminternational.org/docume … 35a0aa3627

Molten salt is an ideal medium for interrupted quenching processes. Nitrate-based salt, the most widely used, blankets the quench temperature range of 150 to 595 degrees C (300 to 1100 degrees F).

https://techxplore.com/news/2020-11-mol … alves.html

http://moltensalt.org/references/static … sities.pdf

Earlier I read that efficiency was only in the 40% for creation of electricity from the heat levels.

kbd512 · 2020-11-18 14:47:28

SpaceNut,

Virtually all commercial photovoltaics have efficiencies "stuck" between 20% and 25%. Space-rated photovoltaics cost millions of dollars per kW of output, so they remain hopelessly impractical at a global scale on cost alone. Since photovoltaics do not store any electrical power, an entirely separate energy storage mechanism is required. All types of batteries are every bit as impractical as photovoltaics for reasons related to cost, physical footprint, degradation of the active materials, and our inability to recycle thoroughly mixed chemical compounds with chemical or physical properties that make them highly resistant to recycling.

A solar thermal power plant is an integrated power production and power storage facility that uses truly abundant / cheap / recyclable materials that do not appreciably degrade over time. Properly built solar thermal power plants can last every bit as long as nuclear power plants with routine maintenance. There is no engineering reason why a well built solar thermal power plant can't last 100 years.

Even if solar thermal is only 40% efficient, that's still twice as efficient as photoelectric and batteries. However, NREL has a real SCCO2 gas turbine running at a pilot plant that's 50% efficient. A molten Silicon or Boron thermal energy storage system combined with thermophotovoltaic (TPV) power conversion is between 70% and 80% efficient, or 35% to 40% efficient overall. A photovoltaic cell would need to be at least 50% efficient, when combined with 90% efficient Lithium-ion batteries, to provide a 5% efficiency improvement over a solar thermal system.

A simplified thermal power storage system that uses all input concentrated solar power to keep a tank of Silicon or Boron thermal power storage medium molten, and a TPV-based power conversion system to produce all electrical power, could be up to 80% efficient if it produced electrical power directly from its TPVs, instead of operating as a night cycle power storage and production subsystem as part of a combined cycle plant that switches over to SCCO2 gas turbines during daylight hours. Despite the lower overall efficiency, a combined cycle plant has more ability to do load-following than a pure TPV-based power conversion system, though it's conceivable that a series of smaller TPVs could achieve a substantially similar effect by either dumping some of the generated power into the ground or simply allowing the molten thermal power storage medium to cool during periods of disuse. The key takeaway is that power output of a pure TPV system would fall between a very narrow band, whereas a gas turbine has the ability to ramp up and down by transferring thermal power from the molten metal to the CO2, as demanded by the grid.

I know that explanation wasn't very good, so think about it this way:

Any kind of photoelectric or thermophotoelectric cell can only ever be "on" or "off", even though output varies by input. All of them are obviously constrained by available input power, but since you're "draining" thermal energy at night by converting the photons given off by the molten storage medium into electrons, do you really want to "produce" 1GW if only 250MW is demanded by current consumption, or do you want to "throttle" the rate of discharge using a thermal transfer medium, a hot flowing gas like CO2, even if that power conversion cycle using a SCCO2 gas turbine will only be 50% efficient, whereas it can be up to 80% efficient for the TPV. Either way, you're going to "waste" some power, but it could be a far more power that gets "wasted" using pure TPV. It makes more sense after you see the sine-wave-like power consumption curve, and the extreme delta between the highest and lowest demand, associated with normal human energy demand / consumption over the course of a given 24 hour time period. The net net is that you "give up" a lot less of the stored thermal power when your power output is not an "all or nothing" proposition the way it is with a TPV operating over a very narrow temperature range. The molten salt used by the Ivanpah CSP power plant has a temperature swing that varies by less than 1 degree between day and night, for example.

Anyway... The total charge / discharge efficiency of a Lithium-ion battery ranges between 80% and 90%, so even if the photovoltaics are 25% efficient and the batteries are 90% efficient, the overall efficiency is still stuck at 22.5%. That efficiency only goes down as the photovoltaics and batteries degrade over time. No matter how many times you slightly increase / decrease the temperature of molten Silicon by transferring its stored thermal power to a SCCO2 working fluid or doing a direct conversion using TPVs, neither Silicon nor CO2 degrade over time because they're stable elemental or chemical compounds that retain their intrinsic properties into perpetuity. A high grade steel or ceramic will not rust in any meaningful period of time, so concentrated solar power is a truly sustainable energy source. A lightning storm won't do anything to the plant and dust can be sprayed or washed off the polished steel concentrator arrays. If they ever get scratched, they can be re-polished.

The most significant overarching problem with photovoltaics and batteries is that they're not readily recyclable and rely upon significant quantities of scarce or toxic elements, so they're simply not sustainable into perpetuity. No amount of "green spin" will ever change that inconvenient little fact. For solar thermal, there's no shortage of concrete / steel / salt or Silicon or Boron / CO2- truly cheap and abundant resources we're never going to run out of here on Earth or most other planets we could actually colonize.

In closing, is the point of this renewable energy effort to nerd-out over the details or cheerlead fanciful technology, or is it to identify what makes something the cleanest and most practical "forever power source" and then devise the most efficient and cost effective engineering methods to achieve the desired result, foregoing every other possible but ultimately impractical solution in favor of something that actually works well enough to be globally scaled out?

If photovoltaics and wind turbines and batteries were the most technologically feasible and economically practical solution, then the infrastructure would've already been built by now and we wouldn't still be having this conversation. It's not working. It's time to face facts and move on to something that stands a better chance of working at a global scale.

SpaceNut · 2020-11-18 18:14:42

That was quite good for the explanation Kbd512 and while its what I would favor building the amount of concentration is the issue for the northern states, was as the new Mexico area benefits quite nicely to solving the power needs with this power plant style.

I need to study the SCCO2 as to what it does for the auxiliary turbine system.

edit:
Supercritical CO 2 = ScCO2

kbd512 · 2020-11-18 18:51:46

SpaceNut,

All aircraft and heavy vehicles require an energy dense power source, which tends to exclude batteries of every description. Fuel cells are a viable alternative to combustion engines for certain applications, but would also require wholesale technology replacement to have any meaningful impact on emissions. However, the heat and pressure that a purpose built solar thermal system could produce is sufficient to make synthetic kerosene or diesel fuels from atmospheric CO2 and desalinated water, which CSP could also produce by flash evaporation. If we had an efficient way to synthesize Propane, the CO2 emissions from Propane are very comparable to Methane and Propane is storable at semi truck tire pressures at high ambient atmospheric temperatures.

tahanson43206 · 2020-11-18 19:14:34

For kbd512 ...thanks for another memorable (and memory worthy) post!

http://newmars.com/forums/viewtopic.php … 73#p174073

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SearchTerm:Thermal Solar Thermal Power

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#21 2020-11-17 18:28:47

Re: Solar Heliostat System with Molten Salt Bath, and Liquid CO2 Method.

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Re: Solar Heliostat System with Molten Salt Bath, and Liquid CO2 Method.

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