Going Solar...the best solution for Mars.

SpaceNut · 2021-05-20 17:14:21

What you are talking about is the depositing of the minerals to make the PV panel on a substrate. Real thin film is on a layer of flexible plastics....

louis · 2021-05-20 17:18:43

Flisom - proven technology: less than 2kgs per square metre.

https://www.flisom.com/wp-content/uploa … -BL_CH.pdf

You example is absurd.

There is no need for the early missions on Mars to have PV systems that last for 20 years.

I think we can probably get down to 0.5 Kgs per sq metre with current technology because we won't need to think of a long term system and because the weather on Mars is so clement. As long as the systems can deal with the temperature shift, then there is not much else to fear apart from dust deposit. However, I am happy to live with 2 kgs per sq metre for now and see what Musk comes up with...because he will have been working on this. Cost will not be important for the first few missions, so he can go with the most expensive solutions.

Calliban wrote:

The link below describes a real thin-film PV project.
https://www.power-technology.com/projec … rthinfilm/
The panels are a mere 8mm thick, which is impressive. They measure 2.2 x 2.6m and weigh 105kg each. That is 18.4kg.m-2 - about 9 times greater than the 2kg.m-2 that Louis described. And that is the mass of the panels, not including subsystems.

kbd512 · 2021-05-20 21:03:09

Calliban,

I'm the one who described using 2kg/m^2 panels by substituting traditional Aluminum backers / frames with 4 plies of high-modulus CFRP and Nomex honeycomb. The actual PV technology I'm talking about is very advanced stuff, and exclusively used aboard aircraft and spacecraft, so far as I know. I proposed a very thin Gorilla-glass-like cover panel to protect the PV (iPhone / iPad screen protector material), the advanced thin film PV that NASA paid to develop, and CFRP / Nomex honeycomb composite back board to provide enough stiffness to rigidly attach the panel or simply prop it up using a mound of regolith, which NASA recommended against because the dust accumulation from static electricity was so bad, but Louis was so enamored with. I'm counting on the PV itself weighing practically nothing, because even aerospace quality protective materials are not all that light in the quantities we're talking about.

Louis then countered with some commercial thin film panels that he posted links to, yet clearly didn't read the spec sheets on, which weighed around 12kg/m^2 for the bare panel. I'm the one who troubles himself to actually read the product spec sheets, performance data, review real world examples of commercial arrays that produce output in the ranges we're talking about, etc. It's a step beyond what most people are willing to spend their free time doing, but it's necessary to work out masses and volumes, output, relative efficiency, etc.

kbd512 · 2021-05-20 21:47:01

louis wrote:

Flisom - proven technology: less than 2kgs per square metre.
https://www.flisom.com/wp-content/uploa … -BL_CH.pdf
You example is absurd.
There is no need for the early missions on Mars to have PV systems that last for 20 years.
I think we can probably get down to 0.5 Kgs per sq metre with current technology because we won't need to think of a long term system and because the weather on Mars is so clement. As long as the systems can deal with the temperature shift, then there is not much else to fear apart from dust deposit. However, I am happy to live with 2 kgs per sq metre for now and see what Musk comes up with...because he will have been working on this. Cost will not be important for the first few missions, so he can go with the most expensive solutions.

Louis,

The panel you posted about is 1,021mm by 419mm and weighs 0.8kg without an adhesive backer.

1.021m Long * 0.411m Wide = 0.419631m^2

1m^2 / 0.419631m^2 = 2.383

0.8kg * 2.383 = 1.906kg <- Only just under 2kg/m^2, but power-to-weight is the figure of merit here

35W per panel * 2.383 = 83.4W/m^2

The nominal output wattage of that thin film panel is less than half of the space-rated PV that I proposed using, which explains why NASA doesn't use thin film panels on their solar powered rovers, because they'd have to more than double the panel surface area to achieve the same level of output, thus more than double the associated panel weight. There's no benefit to doing that.

louis · 2021-05-21 08:39:05

You're balancing a number of things here:

- Mass
- Output efficiency
- Tolerance of Mars conditions (temperature range and dust in particular)
- Reliability and lifetime
- Deployability
- Cost

I'm not qualified to come with an answer to all the issues, but clearly we can get below 2Kgs per sq metre.

Cost will be our friend on the first few Missions, in the sense that, in the context of a project that has cost tens of billions of dollars, spending say $500 million on the PV system is neither here nor there. So if money can buy improved performance against these critera, all the better. We might be able to get to 25% efficiency on 0.5 Kgs per sq metre of Mars-rated PV.

Deployability is a key issue and is why I favour flexible thin film that can be on a roll and simply laid out on the ground - some flat and some on hillsides.

Space X must have a team working on this. After the rockets, this is surely the next priority. Rockets, energy system, propellant plant.

kbd512 wrote:

louis wrote:
Flisom - proven technology: less than 2kgs per square metre.
https://www.flisom.com/wp-content/uploa … -BL_CH.pdf
You example is absurd.
There is no need for the early missions on Mars to have PV systems that last for 20 years.
I think we can probably get down to 0.5 Kgs per sq metre with current technology because we won't need to think of a long term system and because the weather on Mars is so clement. As long as the systems can deal with the temperature shift, then there is not much else to fear apart from dust deposit. However, I am happy to live with 2 kgs per sq metre for now and see what Musk comes up with...because he will have been working on this. Cost will not be important for the first few missions, so he can go with the most expensive solutions.
Louis,
The panel you posted about is 1,021mm by 419mm and weighs 0.8kg without an adhesive backer.
1.021m Long * 0.411m Wide = 0.419631m^2
1m^2 / 0.419631m^2 = 2.383
0.8kg * 2.383 = 1.906kg <- Only just under 2kg/m^2, but power-to-weight is the figure of merit here
35W per panel * 2.383 = 83.4W/m^2
The nominal output wattage of that thin film panel is less than half of the space-rated PV that I proposed using, which explains why NASA doesn't use thin film panels on their solar powered rovers, because they'd have to more than double the panel surface area to achieve the same level of output, thus more than double the associated panel weight. There's no benefit to doing that.

kbd512 · 2021-05-21 10:06:10

Louis,

When I talk about cost, I'm only looking at the cost of transporting whatever we're transporting to Mars. The cost of the equipment isn't even a consideration when compared to transport costs.

The thickness of the thin film product you linked to is 1.5mm, so I'm not sure where you're getting the idea that we're going to decrease its weight by a factor of 4. For that to happen, you're talking about a product that is literally thinner than human hair, which will affect durability and deployability.

The efficiency of thin film is mediocre compared to silicon wafers, and the output wattage of the panel you linked to only confirms that fact.

You wind up with something that's very similar in weight to what I proposed, but nowhere near the efficiency, so you end up doubling the associated panel weight as a result.

There's no magic in 1.9kg/m^2 vs about 2.25kg/m^2 for the solution I proposed. In short, there's no commercial technology that performs better than cutting edge aerospace photovoltaic technology. That was readily apparent to me from the beginning, which is why I proposed the most performant solution in terms of efficiency, durability, weight, and therefore transportation cost. The downside to my proposed solution is that production cost is much higher, but that's unavoidable given the performance requirements. Thin film is great for aircraft supplemental power, but not-so-great on every other performance metric. If the efficiency gets improved, then we can revisit this.

Despite choosing the most performant solution, I couldn't come up with a mass figure anywhere near that of a nuclear solution, which is why I stopped the exercise. There's no solar solution that isn't at least an order of magnitude heavier than an equivalent nuclear solution, using existing technology. For colonization to occur in the next 5 to 10 years, such a mission will use existing proven technology, not something that might one day become available. New solar technologies are being created with regularity, but very few of them see commercial production and that happens on time scales of 10+ years. NASA is just now deploying the next generation of MegaFlex, for example, as well as some new thin film technologies. The agency likes thin film for ease of deployment in microgravity environments, but none of the papers on the research indicate that the panels are more performant than competing silicon wafers in terms of power output per unit weight.

Anyway, this city of a million people won't be built using today's technology, because it's so wildly impractical, so I'm not too concerned with what the colonists will have to work with, which has yet to be defined.

louis · 2021-05-21 15:15:57

This guy on Reddit has a very good presentation:

https://www.reddit.com/r/spacex/comment … r_park_on/

He references Flisom's CIGS eFilm (60g/m2) and comes up with a Mars-appropriate bespoke system of 150 g/m2.

I think he's right about a bespoke system being created for Space X's mission.

His design would come in at 11 tons for the array. Add on maybe 30% for the connecting equipment, and I would still want to take 30 tons of dedicated energy system chemical batteries. So your total would be something like 45 tons

Of course, this discussion becomes irrelevant once you have a PV manufacturing facility on Mars that uses 95% plus Mars ISRU. The issue then is simply how much area of PV panel/film do you have to produce per additional person. It might be 20 sq metres, it might be 100 sq metres. If it's 100 sq metres, and you are producing at a rate of 100 sq metres per sol, that means in a Martian year you've got enough to support another 600 plus people to join the colony at the next landing window. Maybe you allocate 20 of the 600 to PV manufacture and you increase production to 200 sq metres per sol. That's how you expand.

I guess I would ask you "Where has this guy gone wrong?"

kbd512 wrote:

Louis,
When I talk about cost, I'm only looking at the cost of transporting whatever we're transporting to Mars. The cost of the equipment isn't even a consideration when compared to transport costs.
The thickness of the thin film product you linked to is 1.5mm, so I'm not sure where you're getting the idea that we're going to decrease its weight by a factor of 4. For that to happen, you're talking about a product that is literally thinner than human hair, which will affect durability and deployability.
The efficiency of thin film is mediocre compared to silicon wafers, and the output wattage of the panel you linked to only confirms that fact.
You wind up with something that's very similar in weight to what I proposed, but nowhere near the efficiency, so you end up doubling the associated panel weight as a result.
There's no magic in 1.9kg/m^2 vs about 2.25kg/m^2 for the solution I proposed. In short, there's no commercial technology that performs better than cutting edge aerospace photovoltaic technology. That was readily apparent to me from the beginning, which is why I proposed the most performant solution in terms of efficiency, durability, weight, and therefore transportation cost. The downside to my proposed solution is that production cost is much higher, but that's unavoidable given the performance requirements. Thin film is great for aircraft supplemental power, but not-so-great on every other performance metric. If the efficiency gets improved, then we can revisit this.
Despite choosing the most performant solution, I couldn't come up with a mass figure anywhere near that of a nuclear solution, which is why I stopped the exercise. There's no solar solution that isn't at least an order of magnitude heavier than an equivalent nuclear solution, using existing technology. For colonization to occur in the next 5 to 10 years, such a mission will use existing proven technology, not something that might one day become available. New solar technologies are being created with regularity, but very few of them see commercial production and that happens on time scales of 10+ years. NASA is just now deploying the next generation of MegaFlex, for example, as well as some new thin film technologies. The agency likes thin film for ease of deployment in microgravity environments, but none of the papers on the research indicate that the panels are more performant than competing silicon wafers in terms of power output per unit weight.
Anyway, this city of a million people won't be built using today's technology, because it's so wildly impractical, so I'm not too concerned with what the colonists will have to work with, which has yet to be defined.

SpaceNut · 2021-05-21 17:08:58

45 N on mars is not the same as on earth for power levels to receive as its even lower.

A fixed tilt if not changed as mars goes through its seasons will be even lower.

14% as it's the highest claimed in the datasheet would not serve mars very well.

https://ocw.mit.edu/courses/aeronautics … _done2.pdf

https://www.sciencedirect.com/topics/ea … insolation

1-s2.0-S0074614202800171-gr8.jpg

there is an error in the plot for the northern as it should match the southern just upside down.

For Mars, the maximum irradiance varies by ∼224 W m^2 from aphelion to perihelion, at the equator.

louis · 2021-05-21 18:21:38

He's wrong on 45N (this was from a few years back I believe). The recommended landing sites from JPL passed to Space X are around the 31 degree north mark - just outside the optimal zone for PV which is between 25 and 29 north in the northern hemipshere (due to Mars's pronounced wobble).

SpaceNut wrote:

45 N on mars is not the same as on earth for power levels to receive as its even lower.
A fixed tilt if not changed as mars goes through its seasons will be even lower.
14% as it's the highest claimed in the datasheet would not serve mars very well.
https://ocw.mit.edu/courses/aeronautics … _done2.pdf
https://www.sciencedirect.com/topics/ea … insolation
https://ars.els-cdn.com/content/image/1 … 71-gr8.jpg
there is an error in the plot for the northern as it should match the southern just upside down.
For Mars, the maximum irradiance varies by ∼224 W m^2 from aphelion to perihelion, at the equator.

SpaceNut · 2021-05-21 19:23:08

Numbers Louis

https://medium.com/swlh/solar-power-is- … fb221722b1

If we look at a 2031 reference mission, departing on February 22, it arrives at Mars about nine months later on November 7th, 2031. The next departure date for Earth is February 5th, 2033, leaving only 456 days to generate the return fuel, assuming that we’re generating the fuel on-demand in real time). If we leave a fifty day safety zone, this means we must produce about 2,500kg of propellant per day. Pioneer Astronautics created a prototype ISPP (In-Situ Propellant Production) plant which produces 1kg/day of propellant using 700 watts of power. If we take that number and multiply it by 2500, we get 1.75 Megawatts of power
If we plug in our numbers:
Area = 1,750,000w / 593w / 35% / 20%
Area = ~42,000 sq meters (10 acres)
.

louis · 2021-05-22 07:08:16

That guy's thinking is all over the place.

For one thing - how many people live at Mawson? A lot more than would be on Mission One I would suggest.

Somehow, although opposing solar power, he's ended up with a v low sq metre figure.

BTW - I proposed some time ago that a Mars currency should be linked to the amount of electrical output on Mars as a way of securing the value of the currency. So with 1 MwH output you can issue 1 million currency units and with 100 MwHs output, 100 million units.

Hadn't realised Arthur C Clarke had got there before me.

SpaceNut wrote:

Numbers Louis
https://medium.com/swlh/solar-power-is- … fb221722b1
If we look at a 2031 reference mission, departing on February 22, it arrives at Mars about nine months later on November 7th, 2031. The next departure date for Earth is February 5th, 2033, leaving only 456 days to generate the return fuel, assuming that we’re generating the fuel on-demand in real time). If we leave a fifty day safety zone, this means we must produce about 2,500kg of propellant per day. Pioneer Astronautics created a prototype ISPP (In-Situ Propellant Production) plant which produces 1kg/day of propellant using 700 watts of power. If we take that number and multiply it by 2500, we get 1.75 Megawatts of power
If we plug in our numbers:
Area = 1,750,000w / 593w / 35% / 20%
Area = ~42,000 sq meters (10 acres)
.

kbd512 · 2021-05-22 08:49:57

Louis,

Are we still talking about Elon Musk's goal of building a city of a million people on Mars, or some alternative mission that you, personally, want to pursue?

louis · 2021-05-22 10:35:57

Well, I think a one million person city in 30 years powered by a PV system is technically possible. However, I think it is highly unfeasible in terms of social organisation and permanent migration.

My "alternative" mission is not so different. It would use Starships. I just envisage a slower path to a population of one million. I would aim for 100,000 as a potentiallly self-sufficient population. Growth beyond that sort of figure will probably require significant surplus human reproduction on the planet.

kbd512 wrote:

Louis,
Are we still talking about Elon Musk's goal of building a city of a million people on Mars, or some alternative mission that you, personally, want to pursue?

SpaceNut · 2021-05-22 10:50:00

The first landed mission on mars would be automated no crew and its got to be able to return or we risk man if it can not....

Louis the watt hours are even higher as its 700w x 25 hrs x 456 day = 7,980,000 watt hours....

of which 7,980,000 / 1,750,000 = 4.56 hr of sun light at full strength hitting the field of panels being stored and used every hour at a constant rate of 17,500 watts hrs daily meaning the array is storing 3,192 watts during the charging of the battery process to meet the need for power minimum.

42000 m^2 is approximate 205 m x 205 m

I have made a bit of an error in power as its only that level for 6 months then it slowly will decrease through fall towards winter in which you will drop even more before coming back up in spring.... of which each is a 6 month spell

Spring and fall will have the power drop to under the 430 w level and by winter it will be down to 280 watts

so the above calulations will not yield the watt Hours we need as the time for charge gets short as well during each of the periods of the seasons.

Depending on when you land for what season you are in you might not have the time to make enough fuel due to lower than expected power levels....

So how tight is the time in days to return home launch is the question as if its to tight we will need more powe....

kbd512 · 2021-05-22 11:21:06

Louis,

I want to see a city of a million people powered solely by photovoltaics and batteries here on Earth before we attempt to achieve the same thing on another planet receiving half as many photons from the Sun.

Given that the success of human reproduction is driven almost entirely by an abundance of energy, which Mars clearly lacks, do you not think that the problem is related to that lack of abundance?

We had lots of surplus human reproduction before energy was as abundant as it is today, but the problem was that so many of those children died before they reached reproductive age that until power generation technology, thus every other technology dependent upon readily available power, caught up to where it needed to be, the results were a foregone conclusion- life was short, bleak, and brutal. Housing with sanitation and electricity, food production, and medical technology advancements were all driven by surplus energy. If we're limited to the least energy-dense resource available, namely wind and solar power, then societal growth will continue to be stunted by a lack of energy. It doesn't matter in the least how "free" the resource is, because the technologies to use those "free" resources require copious quantities of power to actually implement. That's why China produces the most solar panels of any country- they primarily use the most energy dense resources available, no matter if it agrees with anyone's ideology or not.

louis · 2021-05-22 13:54:31

Presumably kbd you keep referring to the theme of energy density because you feel that's a slam dunk win but it's hardly a trump card. We could equally refer to the positives of solar e.g that the fuel, photons, is massless and delivered free to your door.

Remember, Kyoto in Japan was a million person city back in the 1700s with no fossil fuel input. That was based essentially on a huge food surplus from rice cultivation. There's more than one way to skin a rabbit, as the saying goes.

While our theoretical discussion has focussed on PV power, there are in truth other options. One would be geothermal- there may be some "hotspots" on Mars. More promising perhaps would be heat engines of various types. It does seem possible to run something like a sublimation engine on Mars, taking advantages of the huge diurnal temperature shifts (thus avoiding large energy imput to get the process going), in the same way we run steam engines on Earth, except we wouldn't have to dig out coal. Other heat engines of various types may be possible. We can also use solar reflectors to help heat and illuminate farm habs. The problem with heat engines and the like is that we need to get to Mars and set up a substantial settlement before we can "relax" and investigate all the possibilities.

As on Earth, in order to enjoy the benefits of modern civilisation, we need to first ensure there is a sizeable food surplus. Initially we are going to be constrained to practise artificial-light farming plus techniques like hydroponics and that will be expensive in terms of energy.

However, within a few years we should be able to experiment with crop growing using natural light and soil. The best suggestions I have seen involve transparent plastic structures with CO2 pumped in to a pressure about 20% of Earth's atmosphere. Heating/heat retention for the farm habs could be achieved by use of mylar style reflector blinds that cover the structure me at night, solar reflectors beaming light on to the structures during the day, waste heat from industrial processes and growing crops alongside thermogenic plants that release heat at night. On the plus side, we should be able to avoid all the energy that goes into pesticides, drainage, dealing with adverse weather events such as drought, eliminating rodents and the like on Earth. Initially we will need to put a lot of energy into making soil, but soil can eventually become sustainable through organic style farming.

Mars's land area is the same as Earth's. Once we master the challenges of producing food on Mars with low energy input using natural light and soil, we will be able to generate huge food surpluses. The number of people involved directly in agriculture will be a small percentage, probably no more than 3% of the workforce as it will be highly automated. The other 97% will be free to undertake other work. There will be no problem supporting the food consumption of a city of one million people on a planet with the same land area and nearly half the solar energy of Earth.

kbd512 wrote:

Louis,
I want to see a city of a million people powered solely by photovoltaics and batteries here on Earth before we attempt to achieve the same thing on another planet receiving half as many photons from the Sun.
Given that the success of human reproduction is driven almost entirely by an abundance of energy, which Mars clearly lacks, do you not think that the problem is related to that lack of abundance?
We had lots of surplus human reproduction before energy was as abundant as it is today, but the problem was that so many of those children died before they reached reproductive age that until power generation technology, thus every other technology dependent upon readily available power, caught up to where it needed to be, the results were a foregone conclusion- life was short, bleak, and brutal. Housing with sanitation and electricity, food production, and medical technology advancements were all driven by surplus energy. If we're limited to the least energy-dense resource available, namely wind and solar power, then societal growth will continue to be stunted by a lack of energy. It doesn't matter in the least how "free" the resource is, because the technologies to use those "free" resources require copious quantities of power to actually implement. That's why China produces the most solar panels of any country- they primarily use the most energy dense resources available, no matter if it agrees with anyone's ideology or not.

tahanson43206 · 2021-05-22 17:08:17

For Louis re topic ...

https://www.yahoo.com/news/polish-firm- … 05470.html

Stanislaw WASZAK
Fri, May 21, 2021, 9:35 AM
In this article:
Olga Malinkiewicz
Polish physicist
A Polish company on Friday launched the world's first industrial production line of solar panels based on groundbreaking perovskite technology, which could revolutionise access to solar power.
Named after the Baltic goddess of the sun, Saule Technologies makes sheets of solar panels using a novel inkjet printing procedure invented by company founder Olga Malinkiewicz.
"We're scaling up, going from laboratory to production line," said Malinkiewicz, whose firm is based in the southern city of Wroclaw.
The cutting-edge technology has been in the works for close to a decade but the plant opening comes at a fortuitous time, as the EU member is experiencing a solar boom.

Also...

https://www.brown.edu/news/2021-05-06/perovskite

‘Molecular glue’ makes perovskite solar cells dramatically more reliable over time
In a study that could help to bring inexpensive, efficient perovskite solar cells one step closer to commercial use, researchers found a way to strengthen a key weak point in the cells, dramatically increasing their functional life.
Image of a solar cellResearchers have used self-assembled monolayer "molecular glue" totoughen interfaces in perovskite solar cells to make them more efficient,stable and reliable. Padture Lab/Brown University
PROVIDENCE, R.I. [Brown University] — A research team from Brown University has made a major step toward improving the long-term reliability of perovskite solar cells, an emerging clean energy technology. In a study published in the journal Science, the team demonstrates a “molecular glue” that keeps a key interface inside cells from degrading. The treatment dramatically increases cells’ stability and reliability over time, while also improving the efficiency with which they convert sunlight into electricity.

(th)

louis · 2021-05-22 17:31:19

I went to their website. An annoying lack of technical spec detail. Just vague claims like "have an impressive weight to power ratio".

Looks good in the photos but I've no idea what they are offering really and a production run of 42,000 sq metres doesn't sound that big.

I hope we can nail down what they are offering.

tahanson43206 wrote:

For Louis re topic ...
https://www.yahoo.com/news/polish-firm- … 05470.html
Stanislaw WASZAK
Fri, May 21, 2021, 9:35 AM
In this article:
Olga Malinkiewicz
Polish physicist
A Polish company on Friday launched the world's first industrial production line of solar panels based on groundbreaking perovskite technology, which could revolutionise access to solar power.
Named after the Baltic goddess of the sun, Saule Technologies makes sheets of solar panels using a novel inkjet printing procedure invented by company founder Olga Malinkiewicz.
"We're scaling up, going from laboratory to production line," said Malinkiewicz, whose firm is based in the southern city of Wroclaw.
The cutting-edge technology has been in the works for close to a decade but the plant opening comes at a fortuitous time, as the EU member is experiencing a solar boom.
Also...
https://www.brown.edu/news/2021-05-06/perovskite
‘Molecular glue’ makes perovskite solar cells dramatically more reliable over time
In a study that could help to bring inexpensive, efficient perovskite solar cells one step closer to commercial use, researchers found a way to strengthen a key weak point in the cells, dramatically increasing their functional life.
Image of a solar cellResearchers have used self-assembled monolayer "molecular glue" totoughen interfaces in perovskite solar cells to make them more efficient,stable and reliable. Padture Lab/Brown University
PROVIDENCE, R.I. [Brown University] — A research team from Brown University has made a major step toward improving the long-term reliability of perovskite solar cells, an emerging clean energy technology. In a study published in the journal Science, the team demonstrates a “molecular glue” that keeps a key interface inside cells from degrading. The treatment dramatically increases cells’ stability and reliability over time, while also improving the efficiency with which they convert sunlight into electricity.
(th)

SpaceNut · 2021-05-22 19:05:13

Real data for the perovskite solar cells

Notice where the types follow
NREL%20Cell%20Efficiencies%20Chart.png?itok=mJws2Y-m

SpaceNut · 2021-05-22 19:41:09

reply to louis 491 post where if we were to find a volcanic heat source we would be able to just send a coil of molten salt to the sterling power section of the Krusty alternator and get a non nuclear power quality that can give what we need.

Small Stirling Technology

This is the section that produces the 10kw for the Krustry
temperature that would be required

kbd512 · 2021-05-23 11:48:40

Louis,

Isn't it funny how engineers are always focused on thermodynamics, energy density, power-to-weight ratio, and structural integrity? It's almost as if those were the scientific principles that made all combustion engines and nuclear reactors and solar panels work, that made aircraft fly, that made wind turbines generate power from aerodynamic lift, that took the first humans to the moon... You keep trying to apply belief and ideology to this power generation problem because you're enamored with the idea, I think because photovoltaics are a "shiny new object of affection", as if one could "will away" the basic physics that govern how well any power generating solution actually works. I keep focusing on the implementation of the idea, because that determines whether or not people live or die. For the record, I'm very happy about the fact that the photons are delivered free to my door. I have no complaints about that part of the energy equation. It's the quantity that is delivered and the conversion efficiency that needs to improve. We can't do much about the former, but we can use those scientific principles to improve the latter.

I get the feeling that you keep "throwing stuff at the wall", to see if anything sticks, as part of a concerted effort to ignore what's so obvious, because you don't like what it means. Amongst others here, I keep trying to drive home the fundamental "maths" that govern how well the solution works, because that is what "makes it go", no matter what solution is ultimately used. Why else do you suppose I keep harping on the same basic points? I have more of my own money invested into solar power than I do in any other form of power except combustion engines, so it wouldn't be congruent to suggest that I don't like both technologies. However, I also accept current limitations. Have you even considered the possibility that I understand enough about the basic design principles behind the available technologies involved to know what is and what isn't a practical solution?

Japan in general was already a high-growth place by the 1700s, but the Tenmei Famine in the 1780s reduced the population of a Japan by around a million people. The weather turned cold and since they lacked an abundance of that master resource and all the associated technologies that stemmed from it, entire towns and villages of people died as a result.

All human life will cease to exist in less than 15 minutes pretty much anywhere else besides Earth, if there's ever a problem with the energy supply. Nobody has to get sick, crops don't have to fail, and no war need be started. A single faulty microchip that cuts the flow of electricity for much longer than a few minutes is all it would take without extensive backups and preparations to ensure that that never happens. Much like living on a planet that is not naturally habitable for humans, nuclear power is a double-edged sword. It can give or take life rather quickly. However, a heat engine is also so simple and reliable that it will literally last a human lifetime. Nuclear reactors have been in continuous operation for longer than thin film or triple junction photovoltaics have existed. In point of fact, more than a few of these reactors were generating power before mass production of semiconductors of any kind. All these decades later, they're still operating. No photovoltaic anything has lasted so long in service.

I believe that solar power has tremendous potential, if even some of the fundamental problems are solved, but concerted worldwide effort spanning decades has yet to produce commercial products with the technical characteristics required. As such, we either need more effort focused on solving those problems (power output per unit weight over unit time, performance under LILT conditions, cell degradation / service lifespan improvement) or we need an alternative technology that continues to produce power with or without sunlight, with or without temperature fluctuations, etc. For example, if we had solar cells that lasted for, say 50 years, that would drastically improve the value proposition of using something like thin film, even at the expense of performance. Until then, I'm proposing other realistic alternatives that do not impose such a long string of "IFs" into the power generating solution. Both nuclear thermal and solar thermal appear to be better alternatives.

louis · 2021-05-23 16:10:40

kbd512 wrote:

Louis,
Isn't it funny how engineers are always focused on thermodynamics, energy density, power-to-weight ratio, and structural integrity? It's almost as if those were the scientific principles that made all combustion engines and nuclear reactors and solar panels work, that made aircraft fly, that made wind turbines generate power from aerodynamic lift, that took the first humans to the moon...

The one society that tried to achieve everything through engineering was the Soviet Union. Bridges, dams and canals galore. A world leader in rocket design and space exploration.

And a very poorly functioning economy.

There is more to successful economic development than just engineering.

You keep trying to apply belief and ideology to this power generation problem because you're enamored with the idea, I think because photovoltaics are a "shiny new object of affection", as if one could "will away" the basic physics that govern how well any power generating solution actually works. I keep focusing on the implementation of the idea, because that determines whether or not people live or die. For the record, I'm very happy about the fact that the photons are delivered free to my door. I have no complaints about that part of the energy equation. It's the quantity that is delivered and the conversion efficiency that needs to improve. We can't do much about the former, but we can use those scientific principles to improve the latter.

I don't mind admitting that I am enthused by the idea of solar energy. However, if there were coal and freely available oxygen on Mars I would say burn it. Any pollution would not harm humans, confined to indoors and it would help terraform the planet a little bit.

I get the feeling that you keep "throwing stuff at the wall", to see if anything sticks, as part of a concerted effort to ignore what's so obvious, because you don't like what it means. Amongst others here, I keep trying to drive home the fundamental "maths" that govern how well the solution works, because that is what "makes it go", no matter what solution is ultimately used. Why else do you suppose I keep harping on the same basic points? I have more of my own money invested into solar power than I do in any other form of power except combustion engines, so it wouldn't be congruent to suggest that I don't like both technologies. However, I also accept current limitations. Have you even considered the possibility that I understand enough about the basic design principles behind the available technologies involved to know what is and what isn't a practical solution?

Throwing stuff at the wall is not a bad idea when faced with novel and demanding challenges. That approach is what initially made PV energy a contender. We are faced with novel and demanding challenges on Mars.

You haven't commented on the suggestion of using commercially available Flisom CIGS e-film as the starting point for a Mars based system. Flisom indicate it is suitable for space applications. Blake at Reddit put forward proposals for encapsulation and deployment giving a figure of 150 grams per square metre. If feasible that drastically reduces the mass requirement

https://flisom.com/wp-content/uploads/2 … terial.pdf

Japan in general was already a high-growth place by the 1700s, but the Tenmei Famine in the 1780s reduced the population of a Japan by around a million people. The weather turned cold and since they lacked an abundance of that master resource and all the associated technologies that stemmed from it, entire towns and villages of people died as a result.

Whatever, they had a million person city without fossil fuels or nuclear power.

All human life will cease to exist in less than 15 minutes pretty much anywhere else besides Earth, if there's ever a problem with the energy supply. Nobody has to get sick, crops don't have to fail, and no war need be started. A single faulty microchip that cuts the flow of electricity for much longer than a few minutes is all it would take without extensive backups and preparations to ensure that that never happens. Much like living on a planet that is not naturally habitable for humans, nuclear power is a double-edged sword. It can give or take life rather quickly. However, a heat engine is also so simple and reliable that it will literally last a human lifetime. Nuclear reactors have been in continuous operation for longer than thin film or triple junction photovoltaics have existed. In point of fact, more than a few of these reactors were generating power before mass production of semiconductors of any kind. All these decades later, they're still operating. No photovoltaic anything has lasted so long in service.

Sublimation engines have been demonstrated on Earth in the lab. I think that is definitely a route that will be investigated on Mars.

https://www.extremetech.com/extreme/200 … tion-maybe

I believe that solar power has tremendous potential, if even some of the fundamental problems are solved, but concerted worldwide effort spanning decades has yet to produce commercial products with the technical characteristics required. As such, we either need more effort focused on solving those problems (power output per unit weight over unit time, performance under LILT conditions, cell degradation / service lifespan improvement) or we need an alternative technology that continues to produce power with or without sunlight, with or without temperature fluctuations, etc. For example, if we had solar cells that lasted for, say 50 years, that would drastically improve the value proposition of using something like thin film, even at the expense of performance. Until then, I'm proposing other realistic alternatives that do not impose such a long string of "IFs" into the power generating solution. Both nuclear thermal and solar thermal appear to be better alternatives.

This is a bit like saying "It will be impossible to set up the large industrial factories we have on Earth to make things. Therefore it will be impossible to make things." Mars colonisation calls for new approaches. The most obvious is using 3D printers and industrial robots so we can create a scaled down industrial infrastructure. This won't be as efficient as producing items by the million in dedicated factories but it will meet the challenge of living on Mars.

Likewise with the energy system. PV energy will be less efficient on Mars but it will be capable of meeting our needs. To a certain extent, the absence of adverse weather on Mars and the ability to use higher efficiency panels will compensate for being further from the Sun.

Our material needs will be greater in some respects (life support and pressurisation) but far less in others: no need to produce paper, private vehicles, metalled roads, all that road signage, railways, ports, bridges, ocean going ships, aeroplanes or military weapons, no need to sink huge resources into welfare and care for large numbers sick people (at least for the first few decades) and no need to support a vast governmental bureaucracy. I've never done a proper calculation before but I wouldn't be surprised if what I've just listed amounts to over 50% of your average advanced economy.

SpaceNut · 2021-05-23 18:57:32

It takes 2 sections of the panels to give you 70 watts that covers a 2 m x 1 m area (2,ooo w) giving you an efficiency less than 4% or less even by there own specs which is horrible on earth let alone getting power out of them for the pair on mars that is going to be less than 30 watts.

louis · 2021-05-24 04:37:16

Blake at Reddit took 14% on the basis of the higher figure for nominal power.

The data factsheet claims "Nominal power[W / m2]100-140" .

https://flisom.com/wp-content/uploads/2 … terial.pdf

It clearly states Watts per Square Metre so I've no idea where you get your 70 watts per square metre figure from.

I think it's reasonable to use 14% on the basis that there is money to throw at this. But even if it were only 10%, the whole system would still be very viable.

Even if the lower, 10% figure was applicable, the total mass of the PV system (without electrical connectors and packaging) would rise from a mere 14 tons to 19.6 tons (that's using rolls - lower tonnage if using tilted panels that would be more difficult to deploy).

kbd512 · 2021-05-24 10:15:44

Louis,

1. The nominal Watts per square meter figure corresponds to a fixed Earth TSI value of 1,000W/m^2.

2. 14% of 1,000W/m^2 would generate an output of 140W/m^2. 10% of 1,000W/m^2 would generate an output of 100W/m^2.

3. SpaceNut short-changed you a few Watts, because he simply divided the figure by 2, in order to account for the fact that Mars is roughly twice as far from the Sun as the Earth is.

500W/m^2 * 0.14 = 70W/m^2 <- The figure SpaceNut came up with.

It should be as follows:

593W/m^2 (on average), or 59.3% of the Earth-relative TSI value incident to the surface of Mars. It ranges between 480W/m^2 and 700W/m^2, as Blake noted.

593W/m^2 * 0.14 = 83.02W/m^2 <- average peak power output, assuming the 14% efficiency figure holds under Mars insolation conditions.

83.02W/m^2 is the maximum number of Watts of power, on average, that 1m^2 of Flisom's thin film panel could generate. If the TSI is 480W/m^2, then it's 67.2W/m^2 and if it's 700W/m^2, then it's 98W/m^2. That's peak power at high noon and assumes that sunlight directly strikes the face of the panel.

For the position on Mars that Blake selected, I don't believe the W/m^2 figures hold.

4. You're going to have to read and understand what these documents mean, whether you want to or not. Basic science provided the equations, NASA provided the data, and industry has provided the engineering analysis tools. It's up to you to start using them.

Solar Radiation on Mars

Solar Radiation on Mars: Stationary Photovoltaic Array

Solar Radiation on Mars: Tracking Photovoltaic Array

For the wiring and power inverter mass estimates, you need more information from Flisom to determine what kind of voltage is achievable before running into the dielectric breakdown strength of the active material. Max / transient voltage and amperage info is provided for the triple junction silicon used in spacecraft solar arrays. I have no idea how Blake determined that he could string together 72m^2 of their product without knowing that information. 720 grams for electrical connectors and wiring to carry 1kWe is a very low estimate at a practical working voltage and amperage, even if we invoke advanced materials like CNT / BNNT, and not achievable using conventional Aluminum or Copper wiring at that weight target. Higher voltage is generally preferable to higher amperage, but there's a practical limit to the voltage achievable before arcing occurs on the panel itself. Either the panel itself or some combination of panels and wiring has to deliver the power to the power inverter.

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