The amount of water needed for a NASA base as planned may be extractable from all kinds of sources. However the amounts needed for a SpaceX architecture with MCT and a colony with many people is much higher. IMO it can only be effectively extracted from glaciers.
The regolith cover as determined by orbital radar is no more than 10m. That's not too much given there is a need for many thousands of tons of water. Removing a max amount of 10m of regolith may be a lot easier than mining the ice which is as hard as concrete at Mars temperatures. I don't see sublimation as a major problem as long as the ice is shaded from direct sunlight. Even sublimation needs the same energy as normal heating to liquid and then gaseous form. That's a lot of energy for much ice to sublimate and energy comes from sunlight.
My understanding of the findings is that they would not have any information about glaciers that have more than 10 meters of regolith coverage. I think there may be deeper ones, and that they could be drilled into directionally or horizontally to be harvested. However, there may also be boundaries between glacier and bedrock that could prove advantageous.
My understanding of the findings is that they would not have any information about glaciers that have more than 10 meters of regolith coverage. I think there may be deeper ones,
Trying to avoid this from becoming clogged with SpaceX fandom, but I knew it would be brought up sooner or later. My only statement for SpaceX along with Red Dragon, in regards to ISRU, is that it seems the obvious candidate for field testing ISRU; the trouble with standard probes is that you end up competing for payload space with scientists - MOXIE was lucky to get room on 2020. I suggest holding off on MCT talk until SpaceX declares what's needed in September.
10 meters is still over 32 feet deep...as in over five and a half times the height of an average man...as in hundreds and hundreds of pounds/kilos of material...some of which may also be as hard as concrete and in irregular chunks dropped by ancient Martian seas and glaciers. Moving all of that will drain batteries hard, more so if nuclear power is limited if allowed at all.
That's no idle work, and it is more conservative of energy to draw on easy-to-access regolith heavy in hydrogen, be it ice or gypsum.
That was a funny part of the NASA workshop about selecting landing sites. A glacier expert said, glacial ice is always very clean. Get a block of that ice into the habitat, let it melt and drink it.An expert on ECLSS was shocked. She said, get us a sample of that ice, give us 15 to 20 years development time and we will give you a space rated device that can make it drinkable.I guess the truth will be somewhere inbetween.
Of course, regarding ice, I'd hope for some testing before drinking it, but it sounds consistent with how I've heard frozen water can be surprisingly pure.
IMO, reading the M-WIP gave me the impression gypsum should be pursued. Aside from the mineral being water heavy, there is a very solid scientific motivation to seek it out: gypsum forms in seawater and hot springs. Wherever you find the stuff, odds are you will find many things related to the deep history of Mars prior to the dry Amazonian Era
A glacier expert said, glacial ice is always very clean.
Like glaciers on Earth, glaciers on Mars are not pure water ice. Many are thought to contain substantial proportions of debris, and a substantial number are probably better described as rock glaciers
Glaciers can contain rocks, true. The water is still very clean.It was said the glaciers on Mars they were talking about contain very little rocky material. It would show up as scatter in the signal. From lack of scatter they can safely assume very clean water.
The question is how did the glaciers form?
My understanding is that glaciers form by precipitation. So if they did not form from precipitation they are not glaciers. Given the discussion I assume they are glaciers and have been formed by precipitation. That would make it likely that they do include dust.Glaciers that contain rocky material have gathered it while flowing.Quite possible that my line of thought is too simplistic and wrong.
BTW, whenever there would be significant fuel production on Mars, there would be an excess of oxygen because rocket engines run fuel rich. CO2 extraction from the atmosphere would produce nitrogen, or rather a mix of nitrogen and argon, which is breathable. So a breathable atmosphere would be a welcome byproduct. Only CO2 removal should be necessary.
Quote from: guckyfan on 05/17/2016 04:53 amBTW, whenever there would be significant fuel production on Mars, there would be an excess of oxygen because rocket engines run fuel rich. CO2 extraction from the atmosphere would produce nitrogen, or rather a mix of nitrogen and argon, which is breathable. So a breathable atmosphere would be a welcome byproduct. Only CO2 removal should be necessary.Hmm... this is a semantics note, but I have a bit of a hiccup seeing the concept floated of just removing the CO2 from Mars' atmosphere and you have a useful atmosphere left.That's sort of like saying if you're looking to produce salt, all you need to do is remove the water from salt water, and you have useful salts. I would look at it a lot more as removing the salt from the water, not vice-versa.So, yeah -- what you describe, I would think of as purifying the CO2 in Mars' atmosphere by removing the less than 4% of trace gasses, which are almost entirely composed of nitrogen and argon. That tracks logically a lot better than looking at it as a "CO2 removal" operation...
Why do they condemn atmospheric extraction of water? The method they propose, using compressors, on page 26, is not the most likely one, IMHO. Shouldn't it should be possible to use regeneration of zeolite beds, or another strongly adsorbent material, to extract the water, as in the joined paper? Or has that technology been disproven?
Similar methods can be used to extract the CO2 from the atmosphere as well.If we are making CH4 from atmosphere, we might have heat from the Sabatier reaction to use for regeneration.The power would still be fundamentally solar though, unless the Sabatier used hydrogen from Earth.
Matter of practicality not so much technology. The dry, thin air of Mars makes the Mohave Desert look like a rain forest. To the point, the dehumidifiers would have to run for hours...and hours...and likely weeks if not months to yield much. A shovel load dug from a gypsum deposit would give you the same amount of water in less time; weeks versus a single day, which is more economical?Carbon dioxide pretty much is the Martian atmosphere, with nitrogen and argon the only others with significance, and ubiquitous; hence why both fuel cells and Sabatier reactors are viable because their resource is everywhere. Water vapor sadly doesn't have this advantage, hence why it was turned down in the M-WIP study. If you want water on Mars, digging for it is the best option; I will say near the Martian poles (particularly the northern one) would be the region to consider this...but only if you don't have the means to mine the water literally under your feet there.
Still 45% change of insolation over a Martian year and blocking dust in the atmosphere varies too. Solar power is not so easy on Mars as I thought.
... effectively turning the mine into a radiation shelter and storage room, with the additional benefit of being refrigerated.
Why do they condemn atmospheric extraction of water? The method they propose, using compressors, on page 26, is not the most likely one, IMHO. Shouldn't it should be possible to use regeneration of zeolite beds, or another strongly adsorbent material, to extract the water, as in the joined paper? Or has that technology been disproven?I don't doubt there would be a lot of modifications required, but here is a catalog of commercial desiccant systems. 84 000 cfm is not that much in ventilation equipment terms. a big machine, but nothing extraordinary. And at the very low air densities, the fan power required should be tiny. The main power drain would be the regeneration heat.Similar methods can be used to extract the CO2 from the atmosphere as well.If we are making CH4 from atmosphere, we might have heat from the Sabatier reaction to use for regeneration.The power would still be fundamentally solar though, unless the Sabatier used hydrogen from Earth.
The best estimate of water concentration in the martian atmosphere in your reference is 10e-5 kg/m3, so to get the 16 tonnes of water recommended in the most recent studies for ISRU will need the processing of 1.6 km3 of atmosphere. That 2.7 million m3 per sol for 600 sols. Or 74 m3 a second for 10 hours per sol (when solar power can be used)
Quote from: lamontagne on 05/17/2016 07:41 pmWhy do they condemn atmospheric extraction of water? The method they propose, using compressors, on page 26, is not the most likely one, IMHO. Shouldn't it should be possible to use regeneration of zeolite beds, or another strongly adsorbent material, to extract the water, as in the joined paper? Or has that technology been disproven?I don't doubt there would be a lot of modifications required, but here is a catalog of commercial desiccant systems. 84 000 cfm is not that much in ventilation equipment terms. a big machine, but nothing extraordinary. And at the very low air densities, the fan power required should be tiny. The main power drain would be the regeneration heat.Similar methods can be used to extract the CO2 from the atmosphere as well.If we are making CH4 from atmosphere, we might have heat from the Sabatier reaction to use for regeneration.The power would still be fundamentally solar though, unless the Sabatier used hydrogen from Earth.The best estimate of water concentration in the martian atmosphere in your reference is 10e-5 kg/m3, so to get the 16 tonnes of water recommended in the most recent studies for ISRU will need the processing of 1.6 km3 of atmosphere. That 2.7 million m3 per sol for 600 sols. Or 74 m3 a second for 10 hours per sol (when solar power can be used)
Failure to even consider atmospheric water collection is a major over-site in the paper.
Quote from: Impaler on 07/10/2016 08:48 amFailure to even consider atmospheric water collection is a major over-site in the paper. Ask yourself why isn't every desert settlement on earth littered with "atmospheric water collection" plants. The tech exists by the way, Fraunhofer and Simon Fraser university have active R&D programs for various methods of absorption and refrigeration.
Failure to even consider atmospheric water collection is a major over-site in the paper. It is clearly the source which is most widely distributed and most easily processed, the technical challenge is basically just a sufficient power supply which is something that needs to be cracked anyway.
1 kg water is contained in 250,000m3 of atmosphere
The air handling system implied by these calculations would be on the same order of magnitude as the largest air compressors known on Earth: ~600,000 CFM, requiring 65 megawatts to run, and roughly 5x5x10m in size.CONCLUSION: The mass, power, volume, and mechanical complexity of the system needed for this approach are far outside of what is practical for deployment to Mars.
Quote from: Impaler on 07/10/2016 08:48 amFailure to even consider atmospheric water collection is a major over-site in the paper. It is clearly the source which is most widely distributed and most easily processed, the technical challenge is basically just a sufficient power supply which is something that needs to be cracked anyway.Atmospheric extraction was considered and ruled out. See p26 of presentation.Quote1 kg water is contained in 250,000m3 of atmosphereQuoteThe air handling system implied by these calculations would be on the same order of magnitude as the largest air compressors known on Earth: ~600,000 CFM, requiring 65 megawatts to run, and roughly 5x5x10m in size.CONCLUSION: The mass, power, volume, and mechanical complexity of the system needed for this approach are far outside of what is practical for deployment to Mars.And here they didn't even include the power required to get water back out of the zeolite... which is far from trivial.
I believe the compression is needed to get sufficient flow rate through the zeolite beds to achieve the water extraction rate needed. Cannot just open a canister of desiccant and expect a significant capture rate by diffusion alone -- gotta pump 250,000cubic meters of Martian atmosphere through the beds to get one liter of captured water.
Quote from: AncientU on 10/17/2016 12:59 amI believe the compression is needed to get sufficient flow rate through the zeolite beds to achieve the water extraction rate needed. Cannot just open a canister of desiccant and expect a significant capture rate by diffusion alone -- gotta pump 250,000cubic meters of Martian atmosphere through the beds to get one liter of captured water.There may be ways to use natural flow to extract water from the atmosphere.In fact, you could mine gypsum, extract water from the gypsum, and dump the anhydrite back onto the surface where it will slowly reabsorb water from the atmosphere and become gypsum again. In fact, you could have sheets of something like gypsum or other hydrated minerals that you harvest periodically, dehydrate, then place back onto the Martian surface to reabsorb water. Perhaps arranged vertically along with the direction of the wind to maximize flow rates and areal density of plates.I bet that'd be more energy efficient.
It's really more like farming, isn't it? If you just had fields of these hydrating minerals, it'd be more efficient than raw regolith, since you have to heat up all the regolith, but only part of it yields water.
Of course somebody making maps is going to have to label the area Tatooine. It's practically mandatory.
Quote from: Chris_Pi on 10/18/2016 04:15 amOf course somebody making maps is going to have to label the area Tatooine. It's practically mandatory. Or Arrakis, Vulcan, Geonosis, Korhal...Desert planets are a surprisingly overdone theme in sci-fi I realize.
Propellants MR dp (kg/L) ve (m/s) Id (Ns/L)O2/CH4 3.6 0.8376 3656 3062O2/C2H4 2.7 0.9007 3678 3313
When liquid fuels such as ethanol and n-propanol were included, the total solar-to-fuel efficiency was 2.9%.
One thing I'd like to ask here. Fairly simple.If you only consider sites on Mars that are of relevance for exploration. Which I presume tends to limit things to under 20-25 degrees from the Equator.What do we actually know about the presence of water, how deep and in what form and quantity?In other words, given realistic landing sites, what are we dealing with and also how probable is it? In other words do we need to land a probe beforehand to be certain of the resource?It seems to me that ISRU for water on Mars comes on one of the following forms:1. Water vapour2. Hydrates and other forms of water bound to soil.3. Thin layers of ice of some reasonable purity of unpredictable depth and possibly localised scope near surface (1-2m at most)4. Thicker ice, but with some certainty and located deeper (up to about 30m).Lets consider those in turn.
That's some fascinating info but some of it will need modification, you can't separate out the CO2 in an exchanger bed, it's a major component. Russel's subseaquent post seems to be congruent with what you posted but could benefit from a critique that was more specific to what was sketched out.
Quote from: Lar on 02/04/2018 06:07 pmThat's some fascinating info but some of it will need modification, you can't separate out the CO2 in an exchanger bed, it's a major component. Russel's subseaquent post seems to be congruent with what you posted but could benefit from a critique that was more specific to what was sketched out.Carbon Dioxide has a significantly higher triple point than the other gasses. Is there some way of turning it into snow that falls into a container whilst filtering off the gasses?
Separating N2/Ar from O2 would be easy if not for the fraction of CO. These have close melting/boiling points and its unclear to me if ordinary fractionation can reduce the concentration of CO sufficiently. The answer may lie in separation/freezing at different pressures. But its a non trivial problem.
Separating N2 from O2 on Earth is relatively easy because you're not interested in absolute purity. CO on the other hand you need to get below a very low percentage not to be poisonous.
It should be possible to remove any impurities catalytic. Oxidize the CO to CO2. As a last step so not much of the O2 is lost.
Quote from: Russel on 02/08/2018 03:50 amSeparating N2 from O2 on Earth is relatively easy because you're not interested in absolute purity. CO on the other hand you need to get below a very low percentage not to be poisonous.It should be possible to remove any impurities catalytic. Oxidize the CO to CO2. As a last step so not much of the O2 is lost.
What about LOX-only ISRU on Mars?
What about the idea of bringing seed hydrogen for fuel production? That's 180 tonnes of methane + oxygen (enough to refuel the BFS) for every 10 tonnes of Hydrogen, no?
I'm puzzled by the 180 tonne figure just used for the BFS.
I'm puzzled by the 180 tonne figure just used for the BFS. I'd have thought it required a lot, lot more. Back to the reality of initial scientific/exploratory missions. Its easiest to import hydrogen in the form of liquid methane and simply ISRU the oxygen.Another portable (and non cryogenic) form of hydrogen is common ammonia which is 17% hydrogen by mass and has a room temperature density of 0.73 tonne per m3.In terms of density, liquid methane is 105Kg of hydrogen per m3 and ammonia is 129Kg of hydrogen per m3. Plus it is a source of nitrogen.
The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.
Quote from: sghill on 02/19/2018 01:49 pmThe necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.If, and only if, ISRU seems a cheaper, or more reliable way of doing it for a given mission, including development costs. Methane and oxygen also exist in earths atmosphere, nobody ISRUs, because you can get them in better ways. (Buy them) A lot of the posts in this thread are at best theoretical concepts with regrettably few ties to $ and W.
If the choice were between..A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.And..B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.I choose A.
As you mentioned BFR, I chose C. Human operated ISRU.
Quote from: guckyfan on 02/23/2018 05:53 amAs you mentioned BFR, I chose C. Human operated ISRU.To get those humans there to do the ISRU you need to get them there and back and thus you go back to option A first.
Quote from: Russel on 02/23/2018 03:54 amIf the choice were between..A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.And..B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.I choose A.We could have done Option A back in the 1990s when it was suggested, but nobody wants to pay for it. Not an option.SpaceX is working on Option B. Probably will be done within 10 years, if it works at all. This is the only option being funded and it's cheaper.There is no "If the choice were between" for Mars exploration. SpaceX may not be able to pull it off, but it's the only game in town.
Quote from: Russel on 04/01/2018 05:22 pmQuote from: guckyfan on 02/23/2018 05:53 amAs you mentioned BFR, I chose C. Human operated ISRU.To get those humans there to do the ISRU you need to get them there and back and thus you go back to option A first.How so? They go there, get ISRU going and fly home. No option A with hydrogen needed.
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?
Quote from: Slarty1080 on 04/01/2018 05:48 pmAre "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?They certainly make it a lot harder to just dive in with the sort of mining needed for colonisation scale ISRU.
Quote from: Russel on 04/01/2018 05:52 pmQuote from: Slarty1080 on 04/01/2018 05:48 pmAre "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?They certainly make it a lot harder to just dive in with the sort of mining needed for colonisation scale ISRU.Perhaps this issue alone would make it "easier" to make use of hydrated minerals as a source of water and steer away from ice (at least initialy)?
Quote from: Slarty1080 on 04/01/2018 05:48 pmAre "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?No. If planetary protection protocols effectively stop human missions to Mars then the protocols will be changed.
This looks very interesting. One step production of carbon dioxide (CO2) and water (H2O) into ethylene (C2H4) and oxygen (O2).CO2 + H2O → 0.5C2H4 + 1.5O2http://pubs.acs.org/doi/abs/10.1021/acssuschemeng.7b02110Compare this trying to make methane (CH4):CO2 + 4H2 → CH4 + 2H2O (Sabatier)4H2O → 4H2 + 2O2 (electrolysis)Overall reaction isCO2 + 2H2O → CH4 + 2O2That is, making methane requires twice as much water as ethylene as well as having a lower density and Isp compared to ethylene!Propellants MR dp (kg/L) ve (m/s) Id (Ns/L)O2/CH4 3.6 0.8376 3656 3062O2/C2H4 2.7 0.9007 3678 3313
Quote from: Russel on 02/19/2018 12:53 pmI'm puzzled by the 180 tonne figure just used for the BFS. I'd have thought it required a lot, lot more. Back to the reality of initial scientific/exploratory missions. Its easiest to import hydrogen in the form of liquid methane and simply ISRU the oxygen.Another portable (and non cryogenic) form of hydrogen is common ammonia which is 17% hydrogen by mass and has a room temperature density of 0.73 tonne per m3.In terms of density, liquid methane is 105Kg of hydrogen per m3 and ammonia is 129Kg of hydrogen per m3. Plus it is a source of nitrogen.I'm sorry, I just don't see or support the argument for importing ammonia or liquid methane to the martian surface. This discussion is a distraction, IMHO.Yes, you can transport various gases there in stable forms. And if you do, you are taking many trips to the surface all the way from Earth to collect the necessary ingredients to return once. Until you send up ISRU equipment, you are stuck in this unsustainable and uneconomical paradigm.The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.
Quote from: sghill on 02/19/2018 01:49 pmQuote from: Russel on 02/19/2018 12:53 pmI'm puzzled by the 180 tonne figure just used for the BFS. I'd have thought it required a lot, lot more. Back to the reality of initial scientific/exploratory missions. Its easiest to import hydrogen in the form of liquid methane and simply ISRU the oxygen.Another portable (and non cryogenic) form of hydrogen is common ammonia which is 17% hydrogen by mass and has a room temperature density of 0.73 tonne per m3.In terms of density, liquid methane is 105Kg of hydrogen per m3 and ammonia is 129Kg of hydrogen per m3. Plus it is a source of nitrogen.I'm sorry, I just don't see or support the argument for importing ammonia or liquid methane to the martian surface. This discussion is a distraction, IMHO.Yes, you can transport various gases there in stable forms. And if you do, you are taking many trips to the surface all the way from Earth to collect the necessary ingredients to return once. Until you send up ISRU equipment, you are stuck in this unsustainable and uneconomical paradigm.The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.Curiously your illustration is of MOXIE, which creates Oxygen only. It doesn't generate Hydrogen. Getting ISRU Hydrogen is going to be costly (imported machinery, energy requirements etc) and I've yet to be convince that this really, actually is easier than simply importing Hydrogen.
Quote from: Russel on 07/24/2018 10:48 amQuote from: sghill on 02/19/2018 01:49 pmQuote from: Russel on 02/19/2018 12:53 pmI'm puzzled by the 180 tonne figure just used for the BFS. I'd have thought it required a lot, lot more. Back to the reality of initial scientific/exploratory missions. Its easiest to import hydrogen in the form of liquid methane and simply ISRU the oxygen.Another portable (and non cryogenic) form of hydrogen is common ammonia which is 17% hydrogen by mass and has a room temperature density of 0.73 tonne per m3.In terms of density, liquid methane is 105Kg of hydrogen per m3 and ammonia is 129Kg of hydrogen per m3. Plus it is a source of nitrogen.I'm sorry, I just don't see or support the argument for importing ammonia or liquid methane to the martian surface. This discussion is a distraction, IMHO.Yes, you can transport various gases there in stable forms. And if you do, you are taking many trips to the surface all the way from Earth to collect the necessary ingredients to return once. Until you send up ISRU equipment, you are stuck in this unsustainable and uneconomical paradigm.The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.Curiously your illustration is of MOXIE, which creates Oxygen only. It doesn't generate Hydrogen. Getting ISRU Hydrogen is going to be costly (imported machinery, energy requirements etc) and I've yet to be convince that this really, actually is easier than simply importing Hydrogen.What are you talking about? The hydrogen comes from electrolysis of water. If the colonists have access to water, electricity, and a high school chemistry set, they can make as much hydrogen as they want.
Reading the thread I can't quite shake the idea people seem to think they are building a well by handIIRC in several parts of the US people get their water from individual boreholes. Pulling some numbers off the web gives figures around a 200-600 feet with an 8 inch diameter. Such boreholes can be drilled in less than 10 days. A quick check on eBay suggests these run 16HpThis suggests a borehole of < 32 feet is well within the SoA. Building a drilling rig that can do this would be a high energy task by space probe power levels, around 12Kw. You're also looking at quite a heavy package once the drill pipe is included. Obviously the shorter length helps and lowering the drill rate should reduce the Hp requirements. But that's the easy part
Are you saying here that BFS needs an external radiator when parked on the Martian surface?
I found an interesting thing on Exxon's website that might be a consideration for ISRU production of rocket fuel. Last year they announce a breakthrough in a strain of algae with some DNA mods that doubled bio fuel production. The details are outline here:https://news.exxonmobil.com/press-release/exxonmobil-and-synthetic-genomics-report-breakthrough-algae-biofuel-researchUsing sunlight and CO2, both of which are available on Mars, the have doubled the oil production algae can produce. The oil can be run through a traditional refinery. This might open the production of RP-1 on Mars creating another option for ISRU propellant production.From the article: “The major inputs for phototropic algae production are sunlight and carbon dioxide, two resources that are abundant, sustainable and free,” said Oliver Fetzer, Ph.D., chief executive officer at Synthetic Genomics.Exxon is ready to start scaling this technology up to 10,000 barrels a day: https://news.exxonmobil.com/press-release/exxonmobil-and-synthetic-genomics-algae-biofuels-program-targets-10000-barrels-day-202
<snip of algae greenhouse>No, not efficient enough. Pressurized windows are actually more expensive than solar panels.
Algae-based oil might be more valuable as a feedstock for plastics than as fuel, especially given that most rockets proposed for Mars are methalox-based.
Quote from: Robotbeat on 08/23/2018 02:48 pm<snip of algae greenhouse>No, not efficient enough. Pressurized windows are actually more expensive than solar panels.I have next to me a pressurised window that cost me $10/m^2, and is good for several years at >50PSI. It is a 2l cheap lemonade bottle.You might want to lay a UV protective/greenhouse layer of film over the top of this, but pressurised windows, while they can be expensive, can also be inexpensive.
Quote from: speedevil on 08/23/2018 04:04 pmYou might want to lay a UV protective/greenhouse layer of film over the top of this, but pressurised windows, while they can be expensive, can also be inexpensive.Photovoltaics are STILL cheaper. Solar cells, about 20-25% efficient (versus like 1 to 5% for photosynthesis), are about 10.5 cents per watt right now on the spot market. So that's $25 per square meter, or normalized to the efficiency of your PET bottle photosynthesis, about $1-5 per square meter. (solar cells also need a thin protective film and mounting, but comparable to yours... and still simpler since maintenance is about zero.).
You might want to lay a UV protective/greenhouse layer of film over the top of this, but pressurised windows, while they can be expensive, can also be inexpensive.
Quote from: Robotbeat on 08/25/2018 05:21 amQuote from: speedevil on 08/23/2018 04:04 pmYou might want to lay a UV protective/greenhouse layer of film over the top of this, but pressurised windows, while they can be expensive, can also be inexpensive.Photovoltaics are STILL cheaper. Solar cells, about 20-25% efficient (versus like 1 to 5% for photosynthesis), are about 10.5 cents per watt right now on the spot market. So that's $25 per square meter, or normalized to the efficiency of your PET bottle photosynthesis, about $1-5 per square meter. (solar cells also need a thin protective film and mounting, but comparable to yours... and still simpler since maintenance is about zero.).You can only normalise to the efficiency of PV vs photosynthesis, if you are not going to use that power for a greenhouse, and are not growing some sort of edible algae. In principle, biosythetic oil could be part of the diet.But interesting if you're not using it for this.
Much more efficient to convert the electricity into methane (and ammonia, using hydrogen and nitrogen) and then feeding that to single-celled bacteria to produce protein.