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There are now quite a few examples of PV power coming in lower than 2 cents per KwH.
https://www.forbes.com/sites/dominicdud … 0fca0b4772
There are many things that could destroy our economy but PV power is not among them in my view. The case for PV power is only going to get better with further technological innovations, improved recycling and price reductions.
There are other market distortions that are muddying the water and give misleading impressions of what will be sustainable in the future. For the past 12 years, interest rates have been less than zero when adjusted for inflation. This effectively means that capital costs are zero. That is the point of having low interest rates, it is supposed to stimulate investment and make investment more affordable. But it also destroys effective returns on investment. If pension funds are earning close to zero return, how big are those pensions going to be in 30 years time? And it tends to result in rapidly inflating debt. Why not borrow millions, if the effective interest rate is zero? That is exactly what many zombie companies have done. We are now in a situation where interest rates cannot rise without putting large parts of the economy into receivership. The problem is, the longer they remain low, the more we are stealing from the future.
You may notice that the renewable energy boom didn't start until 2008? First there was the spike in all energy prices due to the peaking of world conventional oil production. Oil prices remained over $100/barrel until 2014. You would expect that to stimulate interest in other sources of energy and it did. Then interest rates dropped to zero and have remained there since. Obviously, that makes highly capital intensive products like wind turbines very affordable, so long as interest rates don't rise above zero. The question is, what happens when they finally have to?
So to summarise, nuclear build capability died in the UK in the early 90s. It is now struggling to be reborn. With North Sea oil and gas essentially gone, its success in doing so will determine whether we have a future as an industrial nation. On the other side of things, zero interest rates are making wind and solar projects look a lot more affordable than they really are in the long term. When the monetary volume inflation and rising debt eventually threaten the value of fiat currencies (the pound in especially vulnerable) large rises in interest rates are inevitable. There will be a truly horrible recession at that point. A lot of people will lose everything. And the government will not be able to borrow very much to bail them out. We could end up in a situation of both high interest rates and high energy prices. That would mean stagflation. Something that we are arguably experiencing already.
This is why the EROI is invalid as the key analytical tool for the efficiency of energy systems
If you have two scenarios:
A. It takes 100 people using 10 units of energy to produce 100 units of energy. The EROI is an impressive 10 to 1.
B. It take 1 person using 10 units of energy to produce 12 units of energy. The EROI is a pathetic 1.2 to 1
But when you look at the amount of energy being produced per person you can see that with Scenario B 100 people can produce 1200 units of energy, way more than the 100 units produced by 100 people under Scenario A.
Now of course this is a very simplistic illustration but something like this is happening before our eyes today with Scenario A being fossil fuels and nuclear power and Scenario B being PV and wind power. We aren't quite seeing the full impact yet because PV and wind power energy input are very much up front and translate into a high initial investment. Furthermore, the absence of effective energy storage systems is suppressing investment in the technology. But we are getting closer all the time to effective energy storage.
It makes much more sense as to think of the economy as a labour and energy system, not just an energy system.
This was why in the 18th century Japan had arguably the most advanced economy in the world. It had a city with over 1 million people long before London. It had a highly complex economy with numerous specialised workshops. It was probably the most literate society on Earth. But it had no steam power. The energy systems were basically wood burning and animal power.
How did it manage to be so advanced? Well it had a very large food surplus thanks to improvements in rice production. This enabled Japan to free people from agricultural labour and direct them into industry and education. Of course, food is energy. But that just confirms, it's the interplay of labour and energy which are important.
Looking at Mars, I think for the first few decades labour is going to be in very short supply, given everything that needs to be done in building up the economy. So, advanced automation and robotics will be a necessary feature of the economy. Mars won't have many cooks, or waiters or cleaners or bus drivers or taxi drivers or indeed - in comparison with Earth - energy workers.
As an addendum to my previous post. There seems to be some confusion about labour productivity and what that actually means in a real economic system. Labour productivity is the monetary value attached to the amount of work that a human being can perform using the skills and tools at his disposal in one man-hour. There are many factors that will determine how productive any specific individual will be. But essentially, ever since human beings began using tools, productivity has been about using tools as a channel for work energy in the reworking of matter. Since the beginning of the industrial revolution, we started using artificial energy, to further magnify the amount of work that an individual can do, as improved scientific understanding allowed us to invest energy in new tools that allowed the channelling of artificial energy.
Let me illustrate the point with the example of a man whose job it is to dig holes. His productivity is measured by the volume of material he can dig out each day. Nature imposes ultimate limits on what is needed to shift dirt. We need to overcome friction when digging, we need to lift dirt out of the hole against Earth gravity and then overcome more friction carrying it to where we pile it up. So regardless of what technologies are at his disposal, there is going to be a minimum energy cost associated with digging. New and more efficient tools allow this limit to be approached but never exceeded.
Using no tools other than his own hands and scratching away at the dirt with his fingers, his productivity is clearly quite low. The energy at his disposal is limited to what his muscles can provide and without tools, the efficiency with which he can apply it to lifting dirt is limited. The first tool we can give him is a spade. This allows him to dig with reduced friction and allows more pressure to be applied per unit area. This dramatically improves the efficiency with which he can apply the limited power output of his muscles to shifting dirt. But the rate of work (I.e dirt shifted) is still limited by the power output of the man's muscles. We just provided a more efficient way of exerting that power, moving him closer in terms of efficiency to the physical limits of energy invested per tonne of dirt moved. Energy had to be invested in making that tool. Some will be invested in maintaining it and eventually in replacing it.
Now suppose we give that man a steam shovel. With it, the man can dig far more dirt per hour. The energy cost of shifting each tonne of dirt hasn't changed. But we have now leveraged the man's own work energy, using a tool that exploits artificial energy. The steam shovel burns coal to raise steam, which is then used to generate mechanical work. We invested artificial energy to make the steam shovel, to reduce iron ore into steel, to melt it, hot roll it and cut and press it into mechanical parts. We then used more labour and energy to build it from those parts. Using the shovel, our worker is able to transform the stored energy in the coal into work energy shovelling the dirt. If we gave him a steam shovel twice the size, he could shovel dirt at twice the rate, but would also burn coal at twice the rate. His productivity is what he can produce by using his own labour, magnified by artificial energy direct through tools.
Now suppose we assume that technology has improved. We now give the man a diesel powered digger. It is smaller than the steam shovel, yet can do the same amount of work per hour. It has lower embodied energy. Because it is lighter and powered by an IC engine, it is more efficient. The same amount of chemical energy can now be leveraged to do more work than before, because technology has allowed efficiency to improve. But note that there are physical limits here. The amount of dirt that can be dug per man hour is still a function of the power applied to the task multiplied the efficiency with which that power is applied.
So in summary: Labour productivity is a function of the amount of supplemental energy that a worker can access per hour, multiplied by the efficiency with which he can use it to perform a valued task, which involves the use of energy to rework matter. The efficiency and his ability to harness the available energy, depend upon the tools at his disposal and his knowledge in being able to use them. Nature sets limits in terms of how much work can be performed per unit energy that is used. Those limits can be approached, but never exceeded, by using better tools (technology) and by training the worker to use them.
This is why the economy is fundamentally an energy system. And the rate at which it can expand depends upon the rate at which it can expand its energy supply. This is in turn limited by the amount of surplus energy available and the energy cost of new energy equipment. New technology changes the tools at hand. It may be possible to reduce embodied energy required using new manufacturing techniques or boost energy return by improving the efficiency of the energy producing device. But nature imposes physical limits here as well. Those limits apply regardless of what technology we find at any point in the future.
I think false windscreens and false windows in Starships, Mars Habs and Rovers will be v. useful in the early stages of colonisation.
GW Johnson wrote:Quaoar:
I suppose the answer to your "windscreen necessity" question is "it depends".
It depends on what kind of craft and how you expect to fly it. If it is a manned spaceplane like space shuttle or Dreamchaser, the pilot really needs a way to see outside to land the thing like an airplane.
Automated landings are possible (see X-37B), but you'll notice the airlines do NOT choose to use that technology. Most of their passengers would not fly, if they ever thought the pilot couldn't see to fly the plane, or wasn't flying the plane because some idiot computer was flying it.
In the case of Spacex's passenger-carrying Starship, the landing is automated. The windows are for the entertainment and sanity of the passengers. Sightseeing out the windows really is psychologically important for passengers. Quite different from trained crew.
GW
But it would be possible to study some kind of solution like false windscreens that are plasma monitors connected to external cameras, or glass windscreen that are covered by PICA-X protected panels during the atmospheric entry, or a glass panoramic module for observation that is jettisoned before the entry.
I'm all for realism.
Let's look at Agua Caliente in Arizona.
https://en.wikipedia.org/wiki/Agua_Cali … ar_Project
The average output is:
300 MW·h/acre per annum
An acre is 4046.48 sq metres.
So that gives an outpute of 74.14 KwHs per sq metre per annum or 0.203 watts per sq metre. So that suggests the Indian solar array figures are about 13% less than Agua Caliente for whatever reason.
And as I indicated elsewhere Agua Caliente seems to have panels with efficiency of 17% or below.
Let's say the average is 16% and let's agree 25% is achievable for PV thin film on Mars. 25% is quite modest.
If so, then your calculation of a nominal 100 becomes 113 and then 176. So a 76% increase in total. Now you have a figure of 313Whs per sq metre. So we are bridging the gap between your fantasy stuff and the reality of a Mars Mission.
And of course I forgot the area is only 85% PV array on your calculation so 313 becomes 368Wh per sq metre. Pretty much bang on with the Wikipedia article!
Louis,
Let's add a little realism to that 360Wh/m^2 figure.
Bhadla actually produced 1.3TWh/yr on Earth and, if efficiency still held up with less insolation, 650GWh/yr on Mars.
650,000,000,000 / 365 = 1,780,821,917.8Wh/day
1,780,821,917.8Wh per day / 10,000,000m^2 of array area = 178.08Wh/m^2/day
360Wh/m^2 / 178.08 = 2.02 meters of array area OR panels that are at least twice as efficient
There are no 40%+ efficient commercial panels. NASA doesn't use panels that efficient. That's the stuff of laboratories.
56,200m^2 * 178.08 = 10,008,096Wh/day or 417kWe of time-averaged power over 24 hours.
56,200m^2 * 360 = 20,232,000Wh/day or 843kWe of time-averaged power over 24 hours.
Felix is back...
SpaceNut - I guess poor old slowhead Musk will never ever figure out he needs a system for removing dust from his PV panels on Mars and clearly as a result the whole mission will fail and the crew will die...
I think Kbd works off the Indian PV array figures.
Clearly economics is the key concern on Earth and so panels in these big arrays, especially those using thin film PV, tend to have poor efficiency. The huge installation at Agua Caliente in Arizona appears to have panels with efficiency of 17% or lower.
There is no physical barrier to achieving higher efficiencies with thin film - only cost barriers. I tend to settle on 25% efficiency but you could go higher. But if you get to 25% that would be nearly half again in output over Agua Caliente. So it's a significant gain.
I don't think there's any evidence from the Mars rovers of efficiency being hugely affected negatively over a 2 to 3 year period.
I was surprised looking at some figures for panels at how well modern panels maintain their output. Not sure why this would be much worse on Mars - there will be far less abrasion from wind effects.
Dust settling can largely be dealt with by robot rovers going up and down the arrays every sol and removing the dust.
I'm not sure how many times I have to repeat this but PV panels do NOT stop working during a dust storms. Even in the worst period of a dust storm which may last for 10-20 sols, there is still significant insolation as confirmed in the paper quoted by kdb and commented on by me. For most of a dust storm you are going to be getting at least 40% of your normal power.
Of course, fission powering of a human colony on Mars is a complete unknown. It should work, but we do know nuclear power stations on Earth suffer mechanical failures. For Mission One, nuclear power is very problematic. You can't load a 1Mw nuclear reactor on to a Starship. Your nuclear power is going to be in discrete units. How quickly can you be up and running? Can you robotise deployment in the way you can PV facility deployment?
But let's assume the propellant production or the launch fails, do the pioneers die? No. Not if you have been sensible in the supplies you have taken to Mars.
You should surely have enough power for life support. You should have enough food and enough water.
The pioneers would simply have to try and stay alive for another two years or thereabouts before rescue came with the next mission. That should not be too challenging, although of course we don't really know the effects of 0.38G over four years or more.
That works out at 306MJ/kg of methane - about 16% efficiency of conversion of electric energy into methane. That is about twice as efficient as what my previous research suggested.
The panels would need to be rolled out and staked to the ground. 56,000m2 is 14 acres. A significant effort, but as you say it may be doable. But Kbd512 figures appear to shown that roughly twice that area would be needed - 28 acres. That is getting to be rather a lot. 112,000m2 = 112m x 1km. How long would it take a team of astronauts to lay those roll out panels?
It would be a race against time. Making mission return propellant before dust contamination and the Martian UV environment reduce power output beneath viable levels for the plant. We face the question in this scenario: do we build a bigger propellant plant that only runs during peak daylight hours or do we add battery mass to try and extend the power supply to a smaller propellant plant?
If they get one of those several month long dust storms, then they are effectively done for. Propellant production shuts down for months, temperature plummets and life support may be compromised. A risky proposal to be sure. If it doesn't work, it will be more than just a robotic rover at stake.
SpaceNut -
We have no idea how far advanced Space X are with plans for propellant production.
Put it this way, since Musk is still claiming he can get humans to Mars in 2026, I really can't see him having "forgotten" about this issue. As with us, it will be uppermost in their minds, after the rocket development. So I feel sure that they have consultants or inhouse people working on this issue. They may not have anything built yet but I am sure they must be at the design stage.
You make some reasonable points.
To reiterate, I am not a fan of the Musk Dream of a One Million City within 30 years or so (actually I read today he was saying this would be possible by 2060 but it probably is a 30 year project in reality, since for the first 4 to 6 years nothing much will be happening apart from basic survival).
But - running with the thought experiment - I agree, whatever energy system is used, this will highly challenging.
The issue I think is really in the first instance is which energy approach using ISRU offers the best prospects.
No surprise I favour solar, but it is certainly a fact that the PV panel production process is now highly automated and could be made even more so if we wish. I think this is critical in being able to supply the energy needs of the expanding city. We are all familiar with lengthy delays on building nuclear power stations on Earth, but PV panel production has been much more reliable.
So, that would be my basic approach, create a PV panel production process that stays ahead of energy demand.
People might not like the idea of a PV array 22 Km by 22 Kms but there is nothing intrinsically impossible about it.
On Mars making PV panels will probably have the same sort of resource investment that making automobiles on Earth does.
And of course that is the other point: I am sure there are lots of things we do on Earth that we won't be doing on Mars. Private automobile production up to 2060 will be very minimal or perhaps non-existent. We won't be building metalled roads, airports, seaports, or pylons. For 99% of transactions we won't be transporting goods (or people) thousands of miles. There won't be the need for huge amounts of street lighting. We won't be transporting gas or oil in huge pipelines.
All these things are huge energy consumers and on Mars we won't be consuming that energy. Balanced against that we will have to power life support and interplanetary transport.
Re heat, if you look at the ECLSS document, it's not one of the big energy drains. My understanding is that heat loss is very slow on Mars, owing to the near vacuum. But certainly it must be the case in a one million person city that (as we see in urban centres on Earth) the heat of the people, machines and processes in such a confined area creates a heat island that also heats people, so the per capita power requirement is much lower.
I was surprised reading the ECLSS document how significant were things like air lock usage - well that will be v minimal in the one million person city.
Unlike PV panels nuclear power stations actively absorb materials throughout their life. I don't know by how much but I would be unsurprised if an average nuclear power station absorb 2 tons a day over 30 years (not including things like water or other coolant).
Importing power supply equipment for a 1 million person city is a tall order, whatever system we use. Kilopower units are optimised for small power requirements. They would definitely be useful for early missions, but aren't something that anyone would even consider attempting to power a city with. Which is why I am looking at Aqueous Homogenous Reactors for meeting those GWatt scale power requirements for a city on Mars. Electric power consumption per capita in the US is 13,000KWh per year. That is equivalent to a constant power of 1.5KWe each. That is electricity- it doesn't cover heating, which is mainly natural gas, or transportation, which is petroleum products. So a 3.7KWe power requirement per capita on Mars may actually be optimistic, especially when you consider the amount of manufacturing that will be going on. I think a fair chunk of the power consumption in Kbd512's estimate is heat, which would be needed to makeup thermal losses in the Arctic temperatures prevalent on Mars. Guess what nuclear reactors produce in great abundance? Heat. Low grade heat at temperatures <100°C is a waste product of nuclear power generation and requires some sort of heat sink. Apparently, it will be useful on Mars.
You keep suggesting that building a power supply using PV panels on Mars is going to be a less labour intensive and easier process than building a nuclear reactor. That doesn't ring true to me. A PV array capable of generating average power of 3.7GW would cover an area of about 100 square kilometres on Mars (assuming no gaps between panels) and would weigh about 1million tonnes for the panels alone. Much of that mass is going to be high grade semiconductor material. Also, you are going to need silver for the panel conductors, large amounts of copper, inverters and transformers for each cluster of PV panels. You are going to need a large mass of batteries for night time energy storage. Storing 16 hours worth of power in lithium-ion batteries would require 250,000 tonnes of Li-ion batteries. Are we going to be making those on Mars as well? These are all materials that must be mined as ores and reduced using energy into metals.
I don't have a precise weight breakdown for what a nuclear reactor based solution would look like. For one thing, it will depend on system design. I could probably work it out if given enough time. But a pressurised water reactor has power density of 80MWth per cubic meter of core volume. That is extremely compact. This link gives an idea of the size of a reactor system needed to generate 1GWe power.
https://www.nuclear-power.net/nuclear-p … nt-system/Total primary circuit volume is 285m3. That is for the reactor vessel, pressuriser, pipework and steam generators. If we were to squeeze it into a compact cubic geometry, with the equipment occupying 50% of the volume say, it would fit onto a square 8.3m aside, 69m2. We need 4 of those units to generate 3.7GW. So that is 1140m3 of plant, occupying an area of 276m2. Let's assume that the primary circuit is made from solid steel. It obviously isn't, but it makes the sums a lot easier. The mass of 1140m3 of primary circuit would be 8,600 tonnes. I have not included here the mass of the secondary steam plant, which includes the steam turbine and condenser, which are both quite massive items. But even if we triple the total mass to account for that, we get 25,800 tonnes.
So that's 25,800 tonnes of mostly steel vs 1.25million tonnes of semiconductor grade silicon, copper, silver, steel, glass and Li-ion batteries. The difference in mass for both systems is a factor of 50. In terms of embodied energy, the difference will be even greater, because most of the mass of the nuclear plant is steel. These are crude calculations admittedly, but they don't lend much support to the idea that it will be easier and less labour intensive to build solar power plants on Mars instead of nuclear power plants. Just mining the required materials will be a severe challenge.
I've pointed out the fundamental flaw in this analysis before. PV panels are essentially closed systems. They don't require need regular supplies of material during their lifetime. This is entirely not the case with nuclear power stations which are complex open systems requiring not just regular material supplies but also direct human management.
So you're engaging in some creative accounting, by not accounting for the lifetime material input.
Price is your best guide to efficiency and material usage. There is no doubt new PV power on Earth in most places is far cheaper than new nuclear - probably by 40-50 cents per KwH. That's not to deny the intermittency problem.
This paper tells us that a 1970s vintage PWR uses about 40te of steel and 90m3 (180te) concrete per average MW of power generation.
https://fhr.nuc.berkeley.edu/wp-content … _input.pdfSteel has embodied energy of 30GJ/te. Concrete has embodied energy 1GJ/te. So that is 1380GJ of invested energy for electric power output of 1MJ/s. Energy payback time is 1,380,000 seconds, or 16 days. A 1GWe reactor needs about 30 tonnes of low enriched uranium each year, which will probably be imported from Earth. If we have to go down the route of using Martian natural uranium, then you can probably cut the whole system power density of the nuclear power plant by half, with an energy payback time of 32 days.
Even in the second case, if we invest 10% of all generated power into expanding the energy supply, then we can double our nuclear power generating capacity every year. It is over simplistic to look at the situation as a pure net energy machine. But starting with 1MWe at year zero and doubling every year, we get to 3700MW after 11.85 years. So, if the Martian colony is given free reign to develop its own nuclear power supply without political interference from Earth, it is possible to achieve a 1 million person city on Mars within fifty years. Maybe even less time than that.
Given what we have discussed regarding the embodied energy of solar PV power generation, it is clear that it is not possible to use solar power on Mars to manufacture a 3.7GWe power plant sufficient to support a 1million person colony within 50 years. It will take the solar power plant at least 100 times longer (3200 days) to repay its initial energy investment. If 10% of its power is invested in building another solar power power plant, then doubling time is 32,000days, or 88 years. Given the rate at which these things wear out due to radiation damage, it begins to look physically impossible using solar. If the power plant wears out in 30 years, say, then about 1/3rd of the output of the solar plant must be used simply to build it's own replacement before it wears out.
This is the best description I could find of what Space X might be planning:
"The first temporary habitats will be their own crewed Starships, as it is planned for them to have life-support systems.However, the robotic Starship cargo flights will be refueled for their return trip to Earth whenever possible. For a sustainable base, it is proposed that the landing zone be located at less than 40° latitude for best solar power production, relatively warm temperature, and critically: it must be near a massive sub-surface water ice deposit.The quantity and purity of the water ice must be appropriate. A preliminary study by SpaceX estimates the propellant plant is required to mine water ice and filter its impurities at a rate of 1 ton per day.The overall unit conversion rate expected, based on a 2011 prototype test operation, is one metric ton of O2/CH4 propellant per 17 megawatt-hours energy input from solar power. The total projected power needed to produce a single full load of propellant for a SpaceX Starship is in the neighborhood of 16 gigawatt-hours (58 TJ) of locally Martian-produced power.To produce the power for one load in 26 months would require just under one megawatt of continuous electric power. A ground-based array of thin-film solar panels to produce sufficient power would have an estimated area of just over 56,200 square meters (605,000 sq ft); with related equipment, the required mass is estimated to fall well within a single Starship Mars transport capability of between 100–150 metric tons (220,000–330,000 lb).
https://en.wikipedia.org/wiki/SpaceX_Mars_program
The panels themselves would cover an area of 56,200 square metres. It's challenging but not crazily so - 236 metres by 236 metres. Probably the equivalent of an athletics track and field. If it came in at 125 tons that would be 2.2 kgs per square metre (with additional equipment mass). If the thin film PV is on rolls it can be laid out automatically by robot rovers according to transponder settings and the appropriate software (in the same way farm robots harvest crops by similar methods). If it needs to be angled (it might not if laid out on a hillside) I am sure approprate systems can be put in place e.g. hanging if on wires or resting it on self-inflatable supports.
The output per sq metre is 0.36 KwH per sol, somewhat less than my ballpark figure of 0.5 KwHes per square metre.
None of the above appears an impossible call. Even if the figures are out by a margin of 50% you could still successfully mount the operation given this is a 500 ton mission.
However, I doubt the figures are going to be that much out. From another post it appears that Space X might be intending to take a hydrogen feedstock, that could certainly reduce the power demand when it comes to manufacturing rocket fuel and that might go some way to explaining Space X's confidence.
I think I'd trust this guy - Mr Wooster (he has that Vulcan quality):
https://www.youtube.com/watch?v=C1Cz6vF4ONE
If you want to get to Mars before 2030 this is the only game in town.
Louis--
I really don't care about "whose plan it is;" use it and yer gonna die. I'm a GREAT fan and supporter of Elon Musk, but he's not infallible. He probably hasn't "done the math" yet.
I would trust Robert Zubrin a lot more when it comes to dealing with energy consumption and how to obtain that which is necessary.
Hi Quaoar,
I've stated before I don't have any fundamental objection to nuclear power on Mars (or indeed for interplanetary transport).
I think there are pragmatic reasons why nuclear power won't be pursued on Mars. Remember firstly there are NO nuclear power facilities designed for Mars that are going to be available for Space X to use on their timeline. Nothing. The nearest is Kilopower - offering a tiny 10Kws for 1.5 tons or thereabouts .But that is still in the testing phase. You would need to deploy 100 on Mars. How long will that take?
It's not impossible nuclear power might come into play on Mars. But it won't be in the first ten years for sure.
Louis,
I may understand your aversion for nuclear on Earth, where an accident can contaminate a region and make a lot of damage like in Fukushima, but on Mars, where there is no air to pollute there is no problem: you just need to put your reactor far from the habitat and the buried glacier you use as a source of water.
If you want to colonize the space, we cannot go too far with chemical rockets: we need NTRs and we need to evolve them from the solid core to the more advanced gas core, so in a future we can go to the asteroid belt and the moons of Jupiter.
Well if it's my plan it's also Musk's and Space X's. Take it up with them. According to you, they are spendings tens of billions on developing a rocket that will take humans to Mars but haven't worked out how to deploy PV power to make the fuel for the return trip. Drop your ideological objections and ask yourself: is that at all likely?
louis wrote:Kbd,
A solar powered base can easily ride out even this worst case dust storm. However, the Starships won't be landing in areas with large dust accumulations.Louis-I'm getting really tired of this BS. I'm a retired Physical Chemist and specialized--once upon a time--in Thermodynamics, and Molecular Photochemistry. You are simply grasping at straws now, trying to discredit the careful calculations and research of some professionals. OK, Solar Power is YOUR RELIGION. It isn't mine and it isn't kdb512's, nor is it GW's.
My bottom line is that if there isn't a strong nuclear system in place as the primary power source--I AIN'T GOIN'! I never argued that is should be the only power source, as I'm too eclectic to make that sort of demand.
If we follow your plan--people DIE.
Why should I take seriously an analyst who claims:
"The sun doesn’t shine at night, it doesn’t shine the same at 4PM as it does at noon, and it doesn’t shine as brightly way up north or south as it does at the equator. This number is a guess without knowing precisely where the landing site is, but 20% is a number commonly used for Earthbound panels used in northern European latitudes."
This shows the guy's ignorance. The optimal PV insolation zone on Mars is 25-29 degrees north (for the northern hemisphere). This, I believe is because of Mars's "wobble" which means the equator is not the best location for PV facilties.
We've a pretty good idea where Space X are going to land - on the boundary of Amazonis and Arcadia about one degree outside the most optimal zone.
Everyone needs to read the article linked by SpaceNut:
The nuclear option is problematic
Remember Kbd claims the Million Person City on Mars will need continuous power of something like 3.7 million Kws (constant).
So, for the 10 Kw Kiopower Units weighing in at 1.5 tons IIRC, that would mean you need 370,000 Kilopower Units at 555,000 tons or 5,550 Starship cargo loads. That's without cabling and other equipment.
Only one problem with using Kilopower units - none has yet been tested and approved in space conditions. It's not even designed for the Mars surface, being designed for use with deep space missions.
As for building a nuclear power station - I am sure it can be done but it will be a big project involving a lot of labour time and then contiued monitoring and maintenance involving substantial human resources. The alternative of manufacturing PV panels on Mars using largely automative processes and ISRU (including robot mining of silica and other materials), coupled with battery production, continued manufacture of methane and oxygen (needed for Starship refuelling in any cases) and manufacture of methane electricity generators, is much more straightforward in my view and will be far less labour-intensive.
Kilopower units are able to produce 1-10KWe and would presumably be available to SpaceX. The base power supply is likely to consist of a mixture of solar power and small baseboard nuclear units. I am researching an alternative if Kilopower is for some reason unavailable to SpaceX or if base power requirements outgrow what Kilopower is able to provide.
The technically easiest nuclear reactor to develop would be an aqueous homogenous reactor. This is a reactor in which uranium sulphate or nitrate salts are dissolved in water or heavy water. These were the first reactors considered for bulk power generation, with the first experimental units operating in the 1940s. Benefits include excellent neutron economy, self-controlling reactivity characteristics, design simplicity and high power rating - I.e. power produced per kg of uranium. This reactor type has the lowest critical mass of all reactors, allowing for the production of extremely compact nuclear cores with high thermal power density. The principle disadvantage is low operating temperature due to the need to reduce corrosion rates in an acidic environment. This places limits on efficiency of conversion of thermal energy into mechanical and electric power. Below is a link to an early text on the topic, dating 1958.
https://fluidfueledreactors.com/I am investigating the possibility of building an aqueous homogenous reactor plant on Mars that can be assembled from native resources. The specifics of the design depend on the answer to a number of questions: (1) Can we access enriched uranium (a) from Earth or (b) make it on Mars? (2) Can we access pure heavy water (a) From Earth; or (b) Make it on Mars? If enriched uranium can be sourced from Earth, then building a nuclear power plant on Mars, becomes far simpler. If it isn't, but we can source deuterium from Earth, then a heavy water based AHR can use Martian natural uranium as fuel.
If neither enriched uranium nor heavy water can be sourced, the only option is to build graphite moderated reactors using Mars sourced natural uranium. A graphite moderated AHR would probably be a pebble bed, with pebbles consisting of graphite produced through methane pyrolysis. The space between pebbles would be filled with a natural uranium sulphate water solution. The majority of moderation would be provided by the graphite, so it may be possible to produce a critical assembly even if the solute is ordinary light water. I need to run the four factor formula to check this. Voiding in the core would not result in power surges. Whilst the water is a better neutron absorber than graphite, it also carries the dissolved fuel. So voiding would remove fuel from high flux regions of the core in addition to water. Radiolysis in the core would generate free oxygen radicals that would corrode the hell out of the graphite. A pebble bed design allows graphite moderator balls to be removed before corrosion becomes too extensive. I would anticipate that the reactor would run at about 100°C in order to keep corrosion at tolerable levels. The reactor vessel would be a cylindrical tank made from, or clad with, stainless steel or nickel alloy.
Operating the reactor at 100°C and rejecting heat at 0°C, implies a Carnot efficiency of 26.8%. Steam cycle efficiency is usually about 2/3 carnot efficiency, so generation efficiency can be expected to be in the region of 18%. A combined heat and power mode is possible. Direct nuclear heat could be used to heat habitats using water as the heat transfer fluid. Or the cycle could dump waste heat at a temperature of 20°C for greenhouse heating.
Early designs of AHRs envisaged using a natural uranium sulphate heavy water solution in the core. This has the best neutron economy of any known reactor. One plan was to surround the core with thorium oxide conversion blankets, which would absorb leakage neutrons and transmute into fissile 233U. A second generation AHR would use 233U sulphate salts as fuel and could function as a net breeder. Alternatively, plutonium produced in the natural uranium fuel salts could be used to fuel sodium cooled fast breeder reactors. Using tube-in-duct fuel, these reactors have a breeding ratio of up to 1.8. Hence, nuclear capacity can be increased very rapidly even if uranium is relatively rare on Mars.
Kbd,
I've never queried the figures for the Indian array output, just the way you've read across to Mars in terms of power output, material usage and so on.
Many of these large arrays on Earth are relatively low power - the big one at Aqua Caliente in Arizona seems to be at 17% or lower efficiency. I think the Mars arrays will be more efficient (probably around 25%) because that is a money problem and money will not be a problem on Mars!
Maybe the array will cost $100 billion. That's $3.3 billion per annum over 30 years. Space X and Tesla will be earning many multiples of that and companies or individuals would be contributing to covering the costs as well. If, for instance, a university wants to set up a campus on Mars, they will no doubt be required to pay the full amount to cover the cost of PV installation.
I have queried your application of the Mars One ECLSS report to a one million person community. There is simply no way you can read across from an analysis looking at 4 pioneers living in tin cans (I never liked the model in any case) to a million strong city. There are many points of departure - air lock losses, water loss, no oxygen production from plants or other organisms.
The comparison with Antarctica is also unhelpful. Having seen video of the station I don't think minimising energy usage is top of their priority list. I was surprised to see people going in and out of isolated huts, cold air coming in each time. More importantly everything I have read suggests heat loss on Mars is a much slower process than in Antarctica.
tahanson43206,
We argued about how much power an actual solar array, the world's largest to date, recorded during a year of operations after construction was completed. Does that seem reasonable to you? The people in all of the solar power websites were basically bragging about how much power it produced, and they have a right to do so, because it objectively made a LOT of power.
If we move that same array 50% further from the Sun, if all other factors remain equal or roughly equal, then it objectively makes 50% less power. The only practical way to overcome that energy density problem is to double the cell efficiency of the array. I don't see what would be the least bit controversial about that fact of life. From an engineering perspective there's no controversy. I've been told as much from people who hold electrical engineering degrees who also design home solar arrays for a living. Why would they lie to anyone about something like that? It certainly wouldn't help their business if they did.
We could do zero ISRU replenishment of consumables by having a perfectly closed loop, despite the functional impossibility of doing that with current technology, but we're still talking about a solar array 20 (19.93 if we need to get really precise) TIMES larger than anything that exists on Earth, just to keep everyone breathing fresh air (CAMRAS and IWP only, nothing else). Does anyone here truly believe that that's practical?
Unfortunately, the energy requirements for living on Mars are incredibly extreme, as in McMurdo Station in Antarctica in the winter extreme. They use 32MWh of power per person in the winter time. It's unreasonable to think that LESS power would be required in a place that's even more extreme, where you have to make all of the air and water and food you need from raw feedstocks that require massive quantities of energy to transform into anything usable. The entire premise of that argument is antithetical to basic logic and math.
Kbd,
Regarding the document -
https://agupubs.onlinelibrary.wiley.com … 19JE005985
There are a number of things to say about this:
1. Gale Crater is a dust bowl. Whatever else is going to happen, no Starship is going to land with humans in a dustbowl. One of the criteria used by NASA/JPL in choosing the landing zone is to find somewhere with relatively low dust levels. So, Gale Crater is very much a worst case scenario.
2. This paper does not state that insolation drops by 95% "during the dust storm" as you claim. It states that during the "highly dusty phase" of the storm values drop by more than 90%. However two important points:
(a) the "highly dusty" phase lasts for a mere 15 sols.
(b) after the peak period there was a dramatic recovery:
"However, after the peak, then values dropped to 60% of pre storm level but these were in keeping with the seasonal trend:
the UV ABC‐channel increased its signal from <10% (during the highly dusty phase) to ~60% of the values measured prior to onset. These irradiances are in fact only slightly below typical values for this time of year (see Figure 2), and given that Mastcam reported typical seasonal values by this point..."
So the insolation was "only slightly below" the norm for most of this dust storm.
My claim of getting around 40% of normal power during a dust storm appears very cautious if anything.
3. There is something opaque itself about the paper Firstly, there's this:
"...it is likely that the increase in dust deposition on the sensor photodiodes during the storm (Figure 1) attenuated the UV signal in its aftermath, rather than higher‐than‐normal atmospheric dust loading continuing to exist. "
And there's this:
"As stated above, the apparent attenuation observed during the highly dusty phase was 95% (Table 2), although additional dust deposition on the photodiodes (Figure 1) during the storm may also have slightly affected this value. "
Not sure what to make of that. One interpretation is that the 90-95% figures are over-inflated. They are certainly the highest I have ever seen quoted.
4. So, overall, this is really the worst of the worst: a dust bowl measurement during one of the worst dust storms on record and with the insolaton values further reduced by dust accumulation.
But let's assume we had an average 92.5% reduction over 15 sols (the paper indicates it was between 90 and 95%) - what then? That would mean if the Mission One base would on average be producing 1Mwe constant, we would be reduced to 75 KwHes constant during those 15 sols. That is probably more than enough to keep the base running. But if not you might look to your chemical battery reserve. I've recommended taking at least 30 tons of batteries. Some of these will of course be found in vehicles. Anyway, with 30,000 Kgs at 250 Whs per Kg that would give you 7,500 KwHes allowing you an additional 20Kwhes constant - so taking you up to 95 KwHes. Still not enough? Well then you starting using your methane and oxygen supply. If it's some way into the mission you will awash with it. Even on arrival there will be plenty sloshing around in the Starship tanks and you can bring with you a dedicated supply. 10 tons of methane could produce 13600 KwHs of energy converting to maybe 7480 KwEs or another 20KwHes constant - so taking you up to 115 KwHes constant . If you still feel that doesn't cut the mustard, then take more methane and more batteries.
A solar powered base can easily ride out even this worst case dust storm. However, the Starships won't be landing in areas with large dust accumulations.
Environmental Control and Life Support System
Kbd,
I've taken a fairly detailed look at the ECLSS document.
https://www.mars-one.com/images/uploads … ssment.pdf
While it's very thorough, I'm not sure how it relates to a city of one million.
Take for instance the reference to loss of nitrogen and argon (Table 4, page 42). Airlock losses account for over half the loss. And this is on the assumption of four airlock operations every day. So in their calculations they are using one airlock per four persons and four airlock movements per day. That is clearly totally irrelevant to a city of 1 million people.
The One Million City might have, say, 20 airlocks to the outside to allow for buses to run to the Spaceport for instance, and maybe to industrial, science and farm habs or nearby mining locations. 20 per million ie one per 50,000 people not 1 per 4 people. Airlock movement of one per person will also become a tiny fraction of that - maybe 100 airlock movements a day so 1 movement per 100,000 people. In a Mars city most people will not leave the city for weeks or months on end. There will be pressurised access to recreational areas where people can exercise in Earth-like surroundings, go swimming and observation towers so they an see their surroundings. [I would think with 100 airlock movements a day you could allow for the exit and return of 10,000 per day if necessary. People would I think go on short breaks to remote "hotel" locations from which they could go exploring in pressurised rovers or undertake some EVA activity. These would be big airlocks able to accommodate a couple of large buses carrying maybe 50 people each.]
Clearly,on a proportional basis, the energy requirement for replacing lost nitrogen and argon will be a tiny fraction of the per person figure given in the ECLSS document.
There are many examples throughout the document where you can query the scaling up. Would we really need to replace 2.25 million kgs of water per annum, when again a large amount of that is lost to airlock cycling. And if we did, would we need to use such an intensive regolith processing system as set out in the paper? Clearly not. We know there fresh water glaciers on Mars. Once we access those with 95% plus purity, processing will be much less energy-intensive. In fact you could probably have the equivalent of a solar tower to melt the ice, just using mylar reflectors.
How much could we use oxygen production from trees and plants, including crops, to mitigate the need for oxygen production?
Odd isn't it?...you can post doctored photos and all sorts of flim flam but you can't post any verifiable evidence that insolation at the surface on Mars ever dips below 20% in a dust storm.
What you're doing here SpaceNut is "creating a narrative". It's not science.
As for telling me "less sunlight means less energy created" that's actually not a new thought for me!
We have PV facilities in sandy deserts and we have dust storms on Earth. It's all a lot more manageable than you want to think.
last dust storm seen by the nuclear rover curiosity june 2018 ....How often are global dust storms in 1971, 1977, 1982, 1994, 2001 and 2007 2018, 2019 https://agupubs.onlinelibrary.wiley.com … 17JE005255 https://www.nature.com/articles/s41467-020-14510-x
Once every three Mars years (about 5 ½ Earth years), on average, normal storms grow into planet-encircling dust stormsThis dust is an especially big problem for solar panels. Even dust devils of only a few feet across -- which are much smaller than traditional storms -- can move enough dust to cover the equipment and decrease the amount of sunlight hitting the panels. Less sunlight means less energy created.
https://solarsystem.nasa.gov/system/int … _Mars..gif
Looking at the sun after the first 2 segments its not producing anything out of a panel
https://solarsystem.nasa.gov/internal_resources/1169/Forecasting Dust Storms on Mars
DUST STORM IMPACTS ON HUMAN MARS MISSION EQUIPMENT AND OPERATIONS
I have been clear: 25% efficiency is a reasonable assumption for a Mars Mission led by Space X. All my calculations are based on 25%. So, as far as my proposals go, what you say about systems with efficiency in excess of 25% are irrelevant.
It's ludicrous to think you've won some sort of argument by working on Earth assumptions then applying Mars constraints and pointing out the difference. We all know Mars receive 43% or thereabouts insolation compared with Earth. I might point out, since you never do, that Mars's insolation - excepting dust storm periods - is much more reliable on a day-to-day basis and the seasonal variation in mid latitudes is far less, which is helpful.
See my other posts re methox production.
I very much doubt we will actually need to resort to Mars ISRU methox production for electric power. Chemical batteries will be able to store enough energy to see the pioneers through the worst period of a major dust storm. Insolation never approaches zero in even the worst dust storm and over weeks your production is unlikely to fall below 40% of normal. So all we are really talking about is scaling back on methox propellant production while the dust storm is doing its worst .
Someone should take a look at the cost of manufacturing 30% efficient solar cells and then ask why it is that nobody uses them here on Earth when they can produce 10% more power. 45% efficient panels are still the stuff of university labs. They exist, which is to say someone can make them, but they're not mass manufactured the way 15% to 30% efficient panels are, and virtually all of the cells used in space applications are around 30% efficient, some slightly less and some slightly more (+/- 5%).
Hyundai's new Sonata Hybrid has a solar panel roof. They claim their 22.8% efficient roof-mounted panel can provide a 60% charge on the vehicle's 1.56kWh battery pack in a sunny locale over the course of a day. If you do the math, 1.56kWh * 0.60 = 0.936kWh, but let's round up to 1kWh for easy math. If we have a 3.7GWe constant power requirement, that works out to 59.2GWh over the course of 16 hours of darkness. That means we need a bare minimum of 59,200,000m^2 / 59.2km^2 of solar panel area to recharge that battery pack on Mars using 45.6% efficient panels, under ideal conditions, to produce the same amount of Watt-hours of power on Mars. The actual array size would be larger still, around 63.25km^2, not taking into account any electrical efficiency losses from thousands of kilometers of wiring or battery efficiency losses or less than ideal atmospheric conditions (dust and normal planetary cycles such as time of year, if the city isn't located on the equator, and Mars' eccentric orbit) that cause the panels to produce less power.
In terms of actual output per year, if you double the efficiency of the Bhadla array, you get Earth-equivalent performance on Mars, which means 25 Bhadlas to supply the power over the course of a year, still equivalent to covering the City of Houston in solar panels. Anyone who thinks they're going to build a photovoltaic array on Mars, 25 times larger than the largest solar array on Earth, for less or even comparable weight to a nuclear reactor, is basically pretending that empirically measured power output and simple multiplication don't exist. In short, they're denying basic math.
If we invoke the use of Lithium-ion batteries that achieve 150Wh/kg at the pack level with 70% DoD (this is what Rolls Royce achieved for their battery powered aircraft, which used Tesla battery cells with most of the packaging and pack protection features stripped away to reduce weight), in order to have any kind of acceptable cell life, we're talking about a truly enormous battery. That's 566,666,666kg, but we'll call it 567,000t. If you invoke the use of O2/CH4 SOXE fuel cells, at 3kW/kg (power density), then you can reduce the "battery" weight to 1,233,333t, and we'll call that 1234t, but that's just for the fuel cell itself. At 70% efficiency, daily Methane consumption for 16 hours of power at night is 6,084,275kg (13.9Wh/kg * 0.7 = 9.73Wh/kg; 59,200,000,000 / 9,730 = 6,084,275kg of Methane alone, which works out to 12,863m^3 if it's stored as LNG, at 473kg/m^3, so the storage vessel is about 23.43m per side if it had a cubic shape). That's enough LNG to refuel 3 Starships and their boosters, but that is what you have to produce EVERY SINGLE DAY to keep all the fans and pumps and electrical heating elements supplied with power.
There's another problem with this method, though, and that's the amount of power you need to make 6,084t of LNG and 21,801t of LOX to react it with. You'd be absolutely overjoyed if your complete process was 50% efficient, which means you need to supply a LOT more power. P2G efficiency sits around 45% to 55% in practical implementations, but that's just the power to make the Methane and compress it to 80 bar or so, but any more compression or liquefaction to save space and we're talking about even lower overall efficiency. If you capture the waste CO2 and H2O as part of a regenerative process, the overall efficiency is better for subsequent cycles but the mass requirement goes up accordingly.
The PV silicon itself is very nearly as heavy as the batteries, whereas the wiring and power transformation equipment could be substantially heavier. At peak power output, the array is producing considerably more power than nuclear reactors running at constant output, so more utility scale power transformers are required. These will be heavier than Earth-bound models, for either power source, because they need massive radiators to remove heat. The more of them you need to contend with power fluctuations, the worse your overall electrical efficiency. The quantity and variety of power inverters and transformers and wiring of the Bhadla array was a real eye-opener, all driven by the fact that output wildly overshoots constant power requirements. If we're being honest about it, the fewer of these massive power transformers that we require for normal operations, the better. It's possible that lighter wiring technology could reduce the weight considerably, but the containment is steel or cast resin, the cores are iron, they're filled with oil, and the conductors are very healthy chunks of Aluminum or Copper.
This is one of the best single resources I've found on the net for our power transformers and load switching equipment:
Power Transformer Dimensions, Weights, and Efficiency Ratings
I'm not sure anyone here ever reads my posts!
I have stated clearly that with a solar power energy system you have to budget for a larger propellant production facility than would otherwise be the case on the "make hay while the sun shines" principle. But nukie fanatics also have to allow for potential downtime, depending on their solution.
I have done all the calculations before and came up with a figure of something like 120-150 tons for a system based on solar power (including emergency methox supply, methox generators, chemical batteries, inverters, cabling and so on). That's a failsafe system. The only failing would be if the sun stopped shining and that's a lot less likely than a nuclear power station going into meltdown.
I suggest you research dust storms on Mars and then I think you might realise they are not the terrifying beastie of your nightmare imagination. They are just periods of low insolation. Big deal. It's like a cloudy day in Kansas.
So the production rate which can barely fill one starship to go home if consumed due to dust storm must out live the storm since all the panels take up the size of 5 payloads which we already calculated. You are counting that the amount of fuel is a full ship and what happens if its not? You are counting on the unknown of how long did you get to make fuel to go home in hopes that the storm does not out last the fuel consumed to keep you alive....
Sorry, SpaceNut, if that's the quality of your argument, there's no point in arguing with me. Take it up with Musk who is already well advanced with his solar-chemical battery-methox mission to Mars.
Louis I bought a cheap solar flower from dollar tree and it works fine outside but the moment you reduce the amount of light such as bring it inside a home within 3 ft of a window that allows light in it no longer works.....so they stop producing the quantity for designed use and you are now dead as that is what a dust storm will do....
As for inflation-corrected prices, the reason for the higher price jump 50 years ago was the formation of the OPEC cartel. If it wasn't for them, the inflation-adjusted price for oil would be nearer what it was 60-70 years ago. Which is far lower.
Well all you are doing there is showing that Calliban's price chart has nothing to do with the intrinsic value of energy.
But what it does show is that the greatest uplift in people's real incomes across the world took place during a period when real oil prices were much higher than in the period of cheap oil. That rubbishes his whole theory that cheap oil = general uplift in wealth.
Of course what happened between the 70s and now was that there was a huge increase in agricultural production, which always allows people to be allocated to other tasks e.g. manufacturing goods and there were huge advances in automative processes in mining and factories, alllowing for huge increases in output per person. There have been lots of other significant technical advances e.g. containerisation of shipping cargoes, introduction of fast motorways (freeways), general road improvements etc which have all tended to reduce the real price of goods and so raise people's incomes.
Oil prices respond far more to collusive manipulation than they do actual supply-and-demand. The reason dwindling reserves did not force them higher yet is that the recent advent of fracking made far more reserves reachable and recoverable.
The only downside to fracking is geology-related. If you free gas from the rock pores (which is what fracking does), it WILL find a way to surface. In relatively unfractured sedimentary geology, the easy path to the surface IS the well. In the heavily-fractured, contorted geology around mountain belts, the easiest path to the surface may be the fractured rock instead of the well.
Gas that follows fractures and comes up away from the well often dissolves into groundwater very much like carbonation. Which causes sink faucets to burst into flame, or even explode.
A lot of the known gas reserves are in such fractured geology, in the Appalachian or Rocky Mountains. The vast sums of money involved make producers very resistant to the notion that there could be problems associated with their extraction efforts. But there really are problems, in that type of geology.
GW
Some little (unexpected) earthquakes have slowed down fracking in the UK. Don't think it's really going to happen here. We are a v crowded country. You need big open spaces.
Although OPEC were artificially raising the price of oil, you have to realise there was an upside. The Arabs of the time didn't really have anywhere much to put the money in their own countries (it's different now of course) and so they had to invest the sudden wealth in Western funds. So there was an investment boom that followed the oil price shock and probably paved the way for the 80s economic boom, in conjunction with the harnessing cheap labour of hundreds of millions of Chinese peasants moving to work in urban centres.
You don't seem to have read my post.
I would be recommending taking 30 tons of methox = 6 tons of methane so more like 250 sols of basic survival under your analysis.
But much more important than that - PV panels do NOT stop producing electricity during a dust storm. I'd be interested to see any evidence to contradict that statement. The best you will be able to come up with is a couple of small NASA rovers closing down to protect themselves when their power reduces to a certain minimum level.
You are never going to have a situation where PV power is below 20% of normal - and it will be only at the very low end for a very few sols. Even in the worst case dust storms the power production is probably something like 40% of normal.
Given a Mission One programme will be looking to produce something like the equivalent of 1Mw constant average, that would equate to 400 KwHe constant average - a huge amount of power.
No one's going to die - the worst that will happen is propellant production slows down.
Louis--
" A few tons of methane and oxygen" will NOT suffice. We're talking about success or failure, not a fanciful dream of a society based on Mars without adequate backup. The energy consumption for even a small frontier style outpost is huge. It's beyond chemical storage to meet the needs. We need to keep people warm, generate electricity for Oxygen production and Methane synthesis, grow crops, do useful WORK. Explore.
Let's use metric tonnes: 1000 kg per metric tonne. Methane has a molecular weight of 16, and Oxygen a diatomic molecule is 32.
Two tonnes of Methane is 125,000 moles.
Reaction: CH4 + 2 O2 ----> CO2 + 2 H2O.
This reaction requires 250,000 moles of O2; 32x250,000 = 8 Tonnes of Oxygen, and all the associated storage to keep it from evaporating.
The heat of combustion is -890.3 k Joules/mole. The sign is minus because heat is liberated or produced.
125,000 x -890.3 = 111,287,500 k Joules.
A Joule is a small unit of energy and it takes 1060 Joules to equal a BTU, which is what most heating contractors will sell you with the furnace you want to install in your house to heat it. We're talking about 104,988,208 BTUs in that "couple of Tonnes of Methane." Sounds like a lot until you realize how much natural gas is consumed to heat the average home. The average home furnace is a 100,000 BTU unit, and that's require to heat a 1,500 square foot residence in a northern Midwestern climate--not on the surface of Mars where nighttime temperatures are -50 C. This is a natural gas consumption of approximately 24,000 BTU per hour for comfort in that midwestern residence on Earth, so let's simply state that it will take double that amount of natural gas for a Mars Sol. For mere survival and not comfort. Since a Sol is 25 hours, we'll round up to a 50,000 BTU Methane consumption per hour = 1,250,000 BTU per Sol for Habitat alone--no power generation or anything else like melting ice for water.
I calculate that doing nothing, and just staying barely alive, the 2 Tonnes might last 84 days. Probably a lot less because I'm probably grossly underestimating the usage for heating the hab. If CH4 is used to generate electricity and thaw drinking water and make Oxygen by electrolysis--the crew might make it to only 45 days--cursing the dependence on Solar power the entire time before they die.
Horrible! lol You mean like half of half maybe - 20-25% of initial power. Doesn't matter for the following reasons:
1. Dust storms do NOT prevent you generating PV electricity. They simply diminish the amount of power.
2. Because of 1, the likelihood of you actually needing to produce methane or oxygen to generate electric power is vanishingly small. I am struggling to think of a scenario where this might be required but I can't.
You have to remember that the solar solution is really three way:
A. PV Panelling (not just for surface deployment but also on your Starships available for use after landing)
B. Chemical batteries (including operational ones on your Starships, available for use after landing).
C. Methox electricity generation from methane and oxygen supplies.
In a very extreme dust storm, you might need to deploy your chemical batteries to help out.
Musk has been tweeting about Tesla having a 400KwH battery available within 3-4 years. But even assuming the current top standard of 250 Watt Hes per kg, 60 tons of batteries across six Starships, say, could deliver 15 MwHs. At 150 KwHes per sol, that would supply with you power for 100 sols. That's just from the batteries alone. That would cover your essential functions.
The emergency methane-oxygen supply would only be relevant in the most extreme circumstances, probably not yet encountered on Mars. It's a failsafe. If you lose 75% or even 90% of your PV power in converting that to methane and oxygen, it's really not an issue. That would assume in any case you had lost the 30 tons of methox you bring with you. These are extreme scenarios very unlikely to happen - almost impossible to happen but you plan for extreme scenarios when going somewhere like Mars for the first time.
What would happen in dust storm is that you would scale back on (not cease) production of propellant because that is the monster eating up your energy production.
For the solar solution this implies your plant is a little larger than would otherwise be the case perhaps (although I am not sure the nuclear option can assume no downtime ever either, so maybe nukists need to plan for periods of increased production as well). In previous discussions I've factored in those increased requirements and the mass requirements for PV and nuclear are very evenly matched (remember - the nuclear option also needs PV and batteries).
calliban ran the numbers for lose of energy for running anything off from methane and it was horrible what you start with to what you get later.....
