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Mention was made on a thread recently about the possiblity of using carbon monoxide as a fuel.
I haven't been able to find much info on this on the internet except that CO was burnt with hydrogen as part of old-fashioned "town gas" as it was called in the UK (manufactured from coal I believe).
There is also this Wikipedia reference:
Carbon monoxide/oxygen (CO/O2) engines have been suggested for early surface transportation use as both carbon monoxide and oxygen can be straightforwardly produced by zirconium dioxide electrolysis from the Martian atmosphere without requiring use of any of the Martian water resources to obtain hydrogen.
Anyway, we're told it's been suggested we can extract water vapour from the atmosphere with an 885 Kg machine, at 45 kgs per sol during summer. Water vapour is only 0.03% of the atmosphere.
Oxygen is found in a concentration some 4 times that of water vapour.
Carbon monoxide is two to three times that of water vapour.
So does that mean we could concentrate CO and oxygen at over 100 kgs per sol? Could we then burn CO to generate heat and drive steam or other turbines?
And is there an energy gain for the power we put in to concentrating the atmosphere over the power produced through combustion of CO?
Does anyone know how much energy in KwHs is in a Kg of CO? And how much oxygen is required to burn a Kg of CO?
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Fuel cell usually thought of as being Hydrogen and Oxygen but there are others for sure...
https://en.wikipedia.org/wiki/Fuel_cell
https://www.electrochem.org/dl/interfac … p41-44.pdf
https://en.wikipedia.org/wiki/Direct_carbon_fuel_cell
Selective CO oxidation over Pt/alumina catalysts for fuel cell applications
also
https://web.anl.gov/PCS/acsfuel/preprin … 2_0326.pdf
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The real question is whether it takes more energy to extract CO and O2 from the Martian atmosphere than is produced when they are burned together. They are extremely low in concentration and I don't know how that would be figured out.
Since a mole of O masses 16 grams and a mole of CO masses 16+12 = 28, you need 16 grams of oxygen to burn 28 grams of carbon monoxide. It's very easy to figure out.
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It's an important question, but not necessarily a killer question. The reason I say that is that if you can land manufacture machines before humans land, you could have several years of producing CO, and the energy for that production could come from a PV facility.
Just as a guesstimate I see you get 8 KwHs of energy from I kg of coal with combustion. So, if we could get 100 Kgs of CO in one sol, if it was half that energy, we would be getting 400 KwHs of energy in one sol. If you had your machine there for four Earth years, you would be gettting something like 560,000 KwHs of energy stored energy, ready and available on landing. Of course, I am not saying storage would be that easy. And you would have to convert the heat energy of combustion to electricity so there would be a major loss there. But if you had something like 300,000 KwE potentially available from your CO/oxygen store that would be a huge energy reserve, the equivalent of something like 4 months' full electric energy supply for a six person mission or 32 months' energy supply in basic survival mode.
The work has been done on water vapour extraction from a Mars atmosphere - and water vapour is at a lower concentration. So I am assuming that oxygen and CO extraction is possible at similar efficiencies. To get your 45 Kgs of water vapour, you had to expend 15 KwE constant.
So it's about 570 grams of oxygen required for every Kg of CO.
The real question is whether it takes more energy to extract CO and O2 from the Martian atmosphere than is produced when they are burned together. They are extremely low in concentration and I don't know how that would be figured out.
Since a mole of O masses 16 grams and a mole of CO masses 16+12 = 28, you need 16 grams of oxygen to burn 28 grams of carbon monoxide. It's very easy to figure out.
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I'd be more interested in using Carbon Monoxide for production of metal carbonyls; the oxidation of CO with O2 is a pretty low enthalpy output reaction, after considering the energy expended in it's manufacture, capture, and storage.
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I believe Antius did some calculations regarding this?
I wonder what the round trip efficiency of CO/O2 energy storage is. Probably fairly low, given the high temperatures needed to produce CO from CO2.
Use what is abundant and build to last
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Until someone puts the entire system to the calculations of energy expended to energy recovered, it could even be a negative number! The key words are "entire system."
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For Mission One, the energy expended in getting the energy system to Mars is going to exceed the amount of energy produced by any energy system in the two years of the mission isn't it?
So nothing will meet your criterion.
The energy system on Mission One just has to be right - whether it's something we bring from Earth like nuclear power or a system that uses energy available on Mars, like solar power.
Until someone puts the entire system to the calculations of energy expended to energy recovered, it could even be a negative number! The key words are "entire system."
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Utilizing blow-off carbon monoxide from the moxie system could in principle, provide some energy back from oxygen production. But not, any at all since it also consumes oxygen, and overall is a loser. CO should be stored for other chemical synthetic uses. Burning CO for energy is an endeavor similar to kissing one's own sister.
Chemistry overall: 2CO2---------------> O2 + 2CO ; 2 CO + O2 --------------------> 2 CO2 + energy
Moxie System
Energy required
Last edited by Oldfart1939 (2017-05-16 15:01:09)
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Let's get a grip on reality. The single most efficient source of energy on the first few expeditions is NUCLEAR. Please quit being in denial about it! This isn't the Earth and we aren't trying to "save the planet from global warming." Using "green energy" just isn't justified. I have no reservations about using nuclear reactors for 25/7 power production, since there will be a 25/7 power requirement. I'd rather see more food and other scientific experiments brought along in place of bulky, heavy, and overall inefficient Lithium Ion batteries. Sorry, Louis!
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I was referring to a machine that would concentrate the free CO (and the free oxygen) in the Mars atmosphere, not a Moxie breaking down CO2. .
Utilizing blow-off carbon monoxide from the moxie system could in principle, provide some energy back from oxygen production. But not, any at all since it also consumes oxygen, and overall is a loser. CO should be stored for other chemical synthetic uses. Burning CO for energy is an endeavor similar to kissing one's own sister.
Chemistry overall: 2CO2---------------> O2 + 2CO ; 2 CO + O2 --------------------> 2 CO2 + energy
Moxie System
Energy required
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I don't know what you mean by "efficient" in this context. Do you mean in terms of power density? Or non-intermittent power? Do you not accept there are also crucial flexibility and fail-safe requirements? If we rely entirely on direct nuclear power electricity (no batteries and no gas) how are we going to explore successfully? And will your power density actually out-perform ultra lightweight PV panels?
I think there is every chance we can develop an energy architecture that provides sufficient, non-intermittent, fail-safe power from Sol One on Mars, and which is not nuclear. It will just be somewhat more complex. But it will be flexible which nuclear by itself is not. I am not anti-nuclear per se on Mars - and I would certainly like to see a couple of RTGs along for the ride as part of an overall energy mix.
Let's get a grip on reality. The single most efficient source of energy on the first few expeditions is NUCLEAR. Please quit being in denial about it! This isn't the Earth and we aren't trying to "save the planet from global warming." Using "green energy" just isn't justified. I have no reservations about using nuclear reactors for 25/7 power production, since there will be a 25/7 power requirement. I'd rather see more food and other scientific experiments brought along in place of bulky, heavy, and overall inefficient Lithium Ion batteries. Sorry, Louis!
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Louis-
It really doesn't matter, but the energy gained in such an endeavor is still going to be les than that expended collecting the gas in the first place. It has to be viewed as a thermodynamic system, and the energy spent will exceed that gained. What you're suggesting is a sort of perpetual motion machine, and that doesn't happen.
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There is an emerging technology that makes battery power competitive with radioisotope power, but further development is still required.
Silicon-Graphite crystal power cells last for many years with no appreciable output drop. 24V at 18A (432We) continuous for a module that weighs approximately two thirds of what a MMRTG weighs. Some of these devices have been tested for five years or more with no discernible drop in voltage or amperage or cell deterioration from being left outside on the ground. Voltage increases slightly, when heat is applied, to about 1.8V per cell (about 2V max at operating temperatures) from 1.5V per cell which has been tested to freezing temperatures. These cells have the benefit of being highly modular, light, extraordinarily energy-dense (but not power dense), extremely cheap to manufacture compared to Pu238 isotope, and there is no radiation of any kind produced.
If electrical energy density for a given mass is of utmost importance, then there's no contest between NASA's decades-old Seebeck technology and crystal power cells. These cells have never been tested in a high GCR environment, but the basic materials used in their construction have been used in fission reactors, so I expect no real issues there.
I don't know how to get around the thermal regulation requirements. Insulation and electrical heating are required. Some of that excess electrical output would be lost to electrical heating to increase the voltage. Even so, it's definitely a better deal if useful electrical output, mass, radiation concerns, and fabrication costs are considered. I estimate a cost of about $50K for a cell of the sort I described (24V at 18A; voltage will go up as heat is increased but I expect to sacrifice some of the total wattage for heating the cell). Keeping the temp at 100F would produce about 1.8V, so it's the same 28V system as the MMRTG.
The good news is that these things would cost tens of thousands of dollars vs tens of millions of dollars for the Plutonium alone. Nobody cares about launching more carbon and silicon into space since every spacecraft already has some in it. The overall manufacture process is not simple and laborious. Oldfart1939 might be able to figure out the best way to manufacture these cells.
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That's a bit silly. This is not a "perpetual motion machine".
On that argument, digging combustible coal out of the ground is a "perpetual motion machine".
All we are talking about here is "digging out" CO from the atmosphere and combusting it with oxygen. There will be an energy cost to doing that but I haven't seen a figure put on that yet. If the amount of combustible energy in CO is half or more of that of coal then I think there could quite possibly be an overall energy gain. However, that is not the key consideration. The key issue is whether you can use PV in the pre-landing phase to generate a sufficient amount of combustible gas.
Louis-
It really doesn't matter, but the energy gained in such an endeavor is still going to be les than that expended collecting the gas in the first place. It has to be viewed as a thermodynamic system, and the energy spent will exceed that gained. What you're suggesting is a sort of perpetual motion machine, and that doesn't happen.
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Thanks kbd - that's v. interesting. Some more on the technology:
http://gizmodo.com/this-graphene-coated … 1452245250
There is an emerging technology that makes battery power competitive with radioisotope power, but further development is still required.
Silicon-Graphite crystal power cells last for many years with no appreciable output drop. 24V at 18A (432We) continuous for a module that weighs approximately two thirds of what a MMRTG weighs. Some of these devices have been tested for five years or more with no discernible drop in voltage or amperage or cell deterioration from being left outside on the ground. Voltage increases slightly, when heat is applied, to about 1.8V per cell (about 2V max at operating temperatures) from 1.5V per cell which has been tested to freezing temperatures. These cells have the benefit of being highly modular, light, extraordinarily energy-dense (but not power dense), extremely cheap to manufacture compared to Pu238 isotope, and there is no radiation of any kind produced.
If electrical energy density for a given mass is of utmost importance, then there's no contest between NASA's decades-old Seebeck technology and crystal power cells. These cells have never been tested in a high GCR environment, but the basic materials used in their construction have been used in fission reactors, so I expect no real issues there.
I don't know how to get around the thermal regulation requirements. Insulation and electrical heating are required. Some of that excess electrical output would be lost to electrical heating to increase the voltage. Even so, it's definitely a better deal if useful electrical output, mass, radiation concerns, and fabrication costs are considered. I estimate a cost of about $50K for a cell of the sort I described (24V at 18A; voltage will go up as heat is increased but I expect to sacrifice some of the total wattage for heating the cell). Keeping the temp at 100F would produce about 1.8V, so it's the same 28V system as the MMRTG.
The good news is that these things would cost tens of thousands of dollars vs tens of millions of dollars for the Plutonium alone. Nobody cares about launching more carbon and silicon into space since every spacecraft already has some in it. The overall manufacture process is not simple and laborious. Oldfart1939 might be able to figure out the best way to manufacture these cells.
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That's a bit silly. This is not a "perpetual motion machine".
On that argument, digging combustible coal out of the ground is a "perpetual motion machine".
Not really; the ease by which a large quantity of coal may be removed contrasted to the energy output makes this a real "winner."
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The lifes blood of mars Co2 production leads to the left over from a MOXIE unit with another useful gas that I hope we will not just release back into mars atmosphere.
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It looks as those for a ton of co2 processed to co we are in the 60kw power source to be able to draw it from the mars atmospher, cool, condense or compress and then to divide it by electrolysis...redit bfr reference.
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His team, partnered with Southwest Research Institute and Gas Technology Institute, has since submitted the design to the U.S. Department of Energy and won an $80 million award to build the 10 MW turbine. The turbine features a rotor that is 4.5 feet long, 7 inches in diameter, and only weighs 150 pounds. The engineers are now completing a scaled-down, 1 MW version of the machine and will test it in July at the Southwest Research Institute.
Hofer’s design uses a small amount of CO2 in a closed loop. “It’s important to remember that this is not a CO2 capture or sequestration technology,” he says. Hofer says that the technology, which is being developed as part of GE’s Ecomagination program, could one day start replacing steam turbines. “It’s on the multigenerational roadmap for steam-powered systems,” he says.
Sounds to good to be true and plausible for mars use.
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For SpaceNut re #20
Thanks for this interesting link! I read it carefully, and note that while the article does report the potential to use non-fossil thermal input, it also makes the point that this improved turbine design could improve the efficiency of coal plants significantly.
Hofer says that the steam power plant technology “has been on a continuous march” to increase efficiency and steam temperature, but once it tops 700 degrees Celsius, “the CO2 cycle becomes more efficient than the steam cycle.” Hofer’s turbine and casing are made from a nickel-based superalloy because it can handle temperatures as high as 715 degrees Celsius and pressures approaching 3,600 pounds per square inch. “You need a high-strength material for a design like this,” he says.
For Mars, this design looks to me like a good candidate to be matched with a fission plant. 10 MW would go a long way toward meeting the needs of a first stage base, because it would support the residents in some comfort while providing support for production of fuel and other needed materials from local resources.
The NASA Stirling engine design is planned to deliver 10 Kw.
I note that the topic started out considering Carbon Monoxide, so this new link is a branch from the original.
(th)
Last edited by tahanson43206 (2020-01-21 23:09:43)
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The temperatures and pressures would change for co but it will still work. Of course small mass quantity to mars is a good thing to go with the heat source of the kilowatt reactors which are throughing away 30kws to produce the 10kw of electrical that we are setting it up for.
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For SpaceNut re #22
Do you have a reference for the research showing that CO would work in this application?
Would the chemistry of CO cause erosion of the metals in the device?
A way forward might be to move the discussion about CO2 compact turbine design to another topic.
(th)
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For earth Gaseous Emissions from Thermal Power Plants Carbon Monoxide – CO CO is a poisonous gas and is harmful to life. Carbon monoxide is formed due to the incomplete combustion fuels such as coal but for Mars its the output from the taking of oxygen from the co2 of mars atmospher. Since that is done at pressure why would we not want to make use of the co as we have already expended energy to gather it. A quick look shows the metal oxides would be able to react with co at temperature and atmospher but we will not be having any metals for tanks or tubing as an oxide form.
Both co and co2 become liquid under pressure and cooling just at different points.
Liquid carbon dioxide is the liquid state of carbon dioxide, which cannot occur under atmospheric pressure. It can only exist at a pressure above 5.1 atm, under 31.1 °C (temperature of critical point) and above -56.6 °C (temperature of triple point). At atmospheric pressure, carbon monoxide will condense at -195°C and freeze at -205°C.
http://www.airproducts.com/products/Gas … oxide.aspx
http://www.airproducts.com/Products/Gas … oxide.aspx
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Carbon monoxide liquid is a cryogen similar to LOX. CO can be burned with oxygen to generate heat, drive a heat engine (maybe a gas turbine) or even to power a rocket. It isn't great rocket fuel but it is relatively easy to make and store.
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