Going Solar...the best solution for Mars.

GW Johnson · 2021-04-14 12:32:44

When looking at solar PV on Mars, there is the lower radiation (by a bit over a factor of 2 relative to Earth) at the edge of the atmosphere. There is the obscuring dust during dust storms reducing transmissibility to as little as 5-10% in the average "bad" storm, and essentially zero during a Mariner-9-class event; this is the 20% that Louis talks about. And, there is the blocking effect of dust accumulations on the panel surfaces, which blocking seems to "equilibriate" in the 75%-blocked/25%-effective class.

Note simple math: 20% atmosphere transmission at midday, per Louis, times 25% effective at dust-covered panel = 5%, the VERY number that NASA says killed Opportunity. And that's NOT for the really bad storms, they are worse!

GW

GW Johnson · 2021-04-14 12:40:50

BTW don't forget that propellant production on Mars is not just methane. It's also the oxygen, which pound-for-pound is required to be some 3 to 4 times as much as methane. Depends on "r" for the engines that burn it. Spacex Raptors operate at about r = 3.7 maybe 3.8, last time I heard.

And for proposed chemical engines on Mars, the fuel energy value we customarily use here on Earth embodies the implicit assumption that oxygen-bearing air is free. That is NOT true on Mars. The 19,000-20,000 BTU/lb for gasoline here on Earth needs to be divided by a 1+r factor for whatever oxidant you must also store. You should be looking at BTU per total pounds of stored propellants. Not just the fuel, on Mars. That would be an r near 4 for gasoline plus oxygen, and r = nearly 15 for stored Earthly air. Gasoline (or diesel or kerosene) + LOX:
20,000 BTU/lb(fuel)/(1 + 4(for r)) = 4000 BTU/lb(fuel plus oxygen).

Fuel heating values just do not look near as energy-dense, when used under Martian conditions, where you must also store and supply the oxidant. I rarely see that taken into account.

GW

Last edited by GW Johnson (2021-04-14 12:43:46)

louis · 2021-04-14 13:11:30

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.

Oldfart1939 wrote:

Everyone needs to read the article linked by SpaceNut:
https://medium.com/swlh/solar-power-is- … fb221722b1

Calliban · 2021-04-14 13:36:40

louis wrote:

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.
Oldfart1939 wrote:
Everyone needs to read the article linked by SpaceNut:
https://medium.com/swlh/solar-power-is- … fb221722b1

Actually, it isn't unique to Mars. On Earth, non equatorial locations do indeed receive quite favourable insolation values in the summer months. This is why England and Northern France have some of the highest cereal crop yields in the world. It is those long, hot summer days, that do such a good job at ripening those rolling fields of wheat in East Anglia. The US, with the exception of Alaska is all much closer to the equator than Northern Europe. They have much more land, but don't get the same yield per acre as we do.

The flip side is that England is dark and chilly in the winter, with short days and light levels that never break out of twilight. The same will be true on Mars, except that the winters are twice as long and the winter cold will be colder than it ever gets on Earth. I pity the poor fool that has to endure a Martian winter whose only power supply is solar panels. Power output is at its lowest when you need it most.

I don't think there is any leg to stand on now for the whole 'solar is better than nuclear argument'. In terms of system mass, reliability and energy return on investment, it has been shown to be inferior to the point of being unworkable. If this is the case on Mars, it raises questions about it's sustainability on Earth as well. We are told that the energy is renewable. But when total system mass is orders of magnitude greater and only partly recyclable, just how renewable is solar power? From every angle I look at it, solar just doesn't make sense as an industrial energy source. The power density is just too low for it to be efficient unless we are much closer to the sun than Earth or Mars. We have analysed it to death and the same conclusion time and again.

Last edited by Calliban (2021-04-14 13:47:39)

louis · 2021-04-14 13:45:35

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?

Oldfart1939 wrote:

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.

louis · 2021-04-14 13:51:46

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.

Quaoar wrote:

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.

Oldfart1939 · 2021-04-14 14:44:54

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.

louis · 2021-04-14 15:41:03

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.

Oldfart1939 wrote:

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.

kbd512 · 2021-04-14 16:18:25

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.

Calliban · 2021-04-14 16:38:16

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.

Last edited by Calliban (2021-04-14 16:46:05)

SpaceNut · 2021-04-14 17:22:01

Elon is making none of the methane or oxygen here on earth to test his starship with, so no there is no working system being developed to do so with mars.

Like wise Nasa's Kilowatt reactor is waiting to be fully developed into a full working unit to be used and while the prototype did produce as predicted its still needs as calculated for a starship to be an issue as well but not for a starter mission several of them would do just fine with supplemental solar, and other forms of energy creation plus storage of what we create.

Remember the mars images are upside down for what is north and south as insight is now in winter not summer as the northern hemisphere would be seeing.

mars-global-context-viking.jpeg?__blob=normal&v=2__ifc1920w

summer for mars south pole October 2016

louis · 2021-04-14 17:41:56

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.

louis · 2021-04-14 18:00:47

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.

Calliban wrote:

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 · 2021-04-14 18:09:02

https://blog.voltaicsystems.com/solar-p … ouds-rain/

Clouds decrease solar panel power output significantly, ranging from about 50 to 100% reduction in power depending on the heaviness of the clouds

just like mars dust storms....

This is what happens to the cells output as light gets less
Characteristics_of_a_typical_Photovoltaic_Solar_Cell.gif

The backs of the solar panels have a black junction box with wires typically coming out of them and some have active circuitry with in them to DC condition a high switching frequency to off load damaging conditions that need to be isolated from the cells contacts. The this is followed by a summing connection box when using multiple panels. The box is smart in that its also got an input condition and isolating circuits to control how the balance of power comes in from all of the panels. The single output of this goes to the battery charging ciruits that watch to not over charge the battery and to limit current coming into them. The there is the user side of the system that takes and invertor to make the dc voltage into the useable AC that we all have become accustomed to.

typical solar panel power

how they get connected

louis · 2021-04-14 19:17:57

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!

kbd512 wrote:

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.

Last edited by louis (2021-04-14 19:20:34)

SpaceNut · 2021-04-14 19:41:56

putting the array of 300 mw on mars will give a yield of just (300 x .43) 129 mw and the batteries will be oversized for the system if you place it in the sweet spot......

Oldfart1939 · 2021-04-14 20:42:24

I found and am cutting and pasting this comment of mine in a conversation with Louis in 2016:

Louis-
I really didn't want this discussion to devolve into another solar power versus nuclear discussion, but I need to state now that your proposal for methane-oxygen as a substitute for nuclear is absurd. We don't need another experimental power supply to contend with, and any methane produced will be required facilitate the trips back to Earth. Re-read what GW has written in the section you quoted. You are violating one of Musk's basic rules by making things overly complicated. A small portable nuclear reactor as suggested by Dr. Zubrin is EXACTLY what is required for Mars Base Alpha. We're talking about human survival--the crew needs energy for all life support functions, and if a massive storm swamps the solar farm--everybody dies. Not if we have that Kilopower unit up and running.

I'm trying very hard to remain civil in our discussion.

kbd512 · 2021-04-14 21:13:26

Louis,

727,000,000,000Wh per year / 9,710,000m^2 = 74871.27Wh/m^2/year

74871.27 / 365 = 205.13W per day

Take the same array to Mars. It's going to make an average of 102.57 Watt-hours of power per day.

Link to the tech specs for the thin film Series 3 photovoltaic panels used in the Agua Caliente array below:

First Solar® FS Series 3TM Black PV Module

Weight is listed as 12kg per 600m by 1,200mm panel.

The Wiki page said that array consisted of 5,200,000 panels.

5,200,000 panels * 12kg per panel = 62,400,000kg

62,400t for 363.5GW on Mars

32,412,000,000,000Wh per year / 363,500,000,000Wh per year on Mars from Agua Caliente thin film panels = 89.166 Agua Calientes

89 * 62,400t = 5,553,600,000kg or 5,553,600t

I already presented a solution that was literally 1/5th of that weight.

516,400t for the Silicon
500,000t for the CFRP composite / Nomex honeycomb backer boards

You're not trying to make this hard, are you?

You're trying to make it utterly impossible.

Do you read any of the documentation on this stuff to understand what you're asking for?

Tech Note: You don't use a fill factor for a thin film array, Louis. It's not a bunch of silicon wafers arranged on a backer board. This is something you learn about by reading the documentation and learning about the technology. Seriously, start reading the documentation on the equipment you want to use. It's not that hard.

Bhadla Note: Bhadla is an extremely dusty environment. Dust drastically reduces output; as much as 10% per month from what I've read. The lower edge of the panels in the Bhadla array stop around 12" to 18" above the ground. The lower edge of the Agua Caliente panels appear to stop about 36" from the ground. That might have an effect on the efficiency. It's almost as if JPL knows what they're talking about when they admonish their aerospace engineers to keep the solar panels at least a meter off the ground.

Power Inverter Note: The Wikipedia article says Agua Caliente used 500 SMA 630CP power inverters, as shown in the link below:

SMA Sunny Central 630CP Inverter

Each 630CP power inverter can accept 713kW of input DC power (550V at 1,350A max) and convert it to 700kVA (315V at 1,283A max)

Weight: 3968.3lbs / 1,800.5kg

1,800kg * 500 = 900,250kg per Agua Caliente or 80,122,250kg (80,122t for 89 Agua Calientes)

Max operating altitude above MSL: 2,000m <- How well does it perform at 40,000m (Mars sea level atmospheric pressure)?

Fresh air consumption: 3,000m^3/hour <- This might be a small problem on Mars

Last edited by kbd512 (2021-04-14 21:54:18)

SpaceNut · 2021-05-09 17:14:16

repost

louis wrote:

Assuming a Space X mission, I don't foresee any difficulties. You'll have at least 4 cargo Starships in the vicinity. Each of those will have their own solar power and battery systems. Your human lander will be continuing to generate power from its substantial solar power arrays. If as I suggested you have robot rovers deployed at the surface (from lower storage points) if there is an issue with power, the robot rovers can deliver battery power to neighbouring Starships. I have also recommend you would arrive with perhaps 30 tons of charged batteries on board - so 9000 KwHes immediately available on arrival (exlcuding the Starship's internal battery array). ATK solar arrays could be deployed by robot rovers before humans move off the Starship.
I envisage the pioneers disembarking via pressurised rover. The rover, or a robot rover, could then tow the first hab, a Bigelow style inflatable hab, to the desired location, where it would be inflated. The first hab would be small and provide temporary or emergency accommodation. Maybe not all the crew would be living there. Maybe it would just be a 4 person hab. Some would stay on the Starship. The purpose of the first hab would be provide an operational base, from which construction of the solar power facilitiy and the second, much larger hab with double air locks could be undertaken.

SpaceNut wrote:
I agree with oldfart1939's assessment in post #42 that power upon landing is the primary system that must be started immediately as the onboard batteries will begin to empty quite quickly.

SpaceNut · 2021-05-09 17:49:12

Not again as space x can only control a mission that they are buying for its own destination.... They for the most part are going to be a rocket supplier and there for not in control....

first missions will not land starship without a test landing and if its with people be glad if a test vehicle is all you lose and not 4 of them full of just solar panels and batteries....

Why would elon for space x buy solar panels when they provide them to there ships so not ATK now Northrup Gruman for these or you are going to pay through the nose for them...

1 MW solar power plant installation, the solar farm land requirements would be around 4 acres, when using a crystalline technology with rough estimate as space can also be influenced by the efficiency of the panels and technology.

Crystalline solar panels have around 18% of efficiency level while the thin-film technology offers approximately 12% efficiency.

here is a video of a solar farm being constructed

https://www.absolutesolarandwind.co.uk/ … s-mackies/

This is a 1.8 mega watt system....

louis · 2021-05-09 19:27:41

I think Space X will be pretty much in total control, at least for the first decade of colonisation. They will decide what goes on their rockets. It's not going to be nuclear reactors.

Starship is going to be tested many times before they go to Mars. Look at the rate of production and launches. I think there will be many more tests than preceded the Apollo moon landings - probably more like 30 langinds including landings on Mars. Most important of all, humans don't follow to Mars unless the cargo Starships make a good landing.

When it comes to Mars I think Musk will run with what works. Tesla or Solar City don't do "umbrella" space rated solar panels. He will go to those firms that can provide what is required.

SpaceNut wrote:

Not again as space x can only control a mission that they are buying for its own destination.... They for the most part are going to be a rocket supplier and there for not in control....
first missions will not land starship without a test landing and if its with people be glad if a test vehicle is all you lose and not 4 of them full of just solar panels and batteries....
Why would elon for space x buy solar panels when they provide them to there ships so not ATK now Northrup Gruman for these or you are going to pay through the nose for them...
1 MW solar power plant installation, the solar farm land requirements would be around 4 acres, when using a crystalline technology with rough estimate as space can also be influenced by the efficiency of the panels and technology.
Crystalline solar panels have around 18% of efficiency level while the thin-film technology offers approximately 12% efficiency.

here is a video of a solar farm being constructed
https://www.absolutesolarandwind.co.uk/ … s-mackies/
This is a 1.8 mega watt system....

kbd512 · 2021-05-09 21:54:31

Louis,

Physics dictates what goes in a SpaceX rockets, not you, not NASA, not even SpaceX. SpaceX can assert we can go to Mars using Aluminum rocket engines, but heat of combustion is going to melt those engines like butter every single time, which is why nobody uses them. All the solar panels and batteries you proposed using are much heavier as compared to the smallest and most inefficient nuclear reactors available. The mass allocation for power production only gets worse as you try to scale up to the amount of power actually required.

There are no commercial solar panels and batteries in existence that achieve the mass and power output required. We keep going through this same exercise over and over again. The end result is the same, over and over again. If objective reality doesn't align with your ideas about what will or won't work, then objective reality is not the problem. Making more claims that don't square with objective reality won't change objective reality, not for you, not for me, not for SpaceX, not for anyone else.

Is SpaceX sending people to Mars to build giant solar arrays, or to colonize the planet?

If they're going to colonize it, then they're going to need nuclear power, because physics won't be overcome by any amount of magical thinking.

Ideology is a major reason why we haven't gone anywhere since the Apollo program ended. Machines run by adhering to good design and engineering principles, not ideology.

Calliban · 2021-05-10 09:25:05

Here are some real world li-ion battery weight statistics for Tesla vehicles.
https://enrg.io/tesla-battery-weight-ov … ll-models/

The 200kWh Tesla roadster battery weighs 1836lb, giving it a mass energy density of 0.86MJ/kg. That means that 9000kWh of batteries will weigh 37.7 tonnes, minus inverters, transformers, cabling, etc.

Whether Musk chooses to bring solar panels with batteries or a nuclear reactor for early missions is his choice, as it is his money to burn. And burn it will. I have already shown his plans for a million person human society on Mars has zero prospects based on solar only energy. Solar PV just doesn't generate a high enough net energy return to make this level of industrial development possible on Mars. So far as long term energy needs are concerned, solar power is a dead end on Mars.

This sort of thing isn't possible on Earth, either. Since the global financial crisis, interest rates have dropped beneath inflation. Those solar and wind capital costs, that looked so unaffordable before 2008, have now magically disappeared.
The same thing happened to those previously unaffordable shale oil capital costs. This has given a lot of people some very misleading impressions about what is going to be possible long term, when interest rates rise into positive numbers again, as eventually they must. It will be a very uncomfortable realisation for renewable energy enthusiasts. For anyone expecting shale oil to be a long-term solution as well.

Last edited by Calliban (2021-05-10 09:30:15)

louis · 2021-05-10 14:20:22

Calliban wrote:

Here are some real world li-ion battery weight statistics for Tesla vehicles.
https://enrg.io/tesla-battery-weight-ov … ll-models/
The 200kWh Tesla roadster battery weighs 1836lb, giving it a mass energy density of 0.86MJ/kg. That means that 9000kWh of batteries will weigh 37.7 tonnes, minus inverters, transformers, cabling, etc.

"The Battery Day announcements are largely in keeping with our forecast developments on EV batteries. Should Tesla fulfil all its ambitions on this front, it may catalyse faster uptake of EVs – both passenger and commercial vehicles. Success could spill over into adjacent transport sectors. For example, on the assumption of success on all fronts, Tesla will also more than achieve the critical battery density for short range electric airplanes – namely 400 Wh/kg with high cycle life. Indeed, Elon Musk recently stated this could happen within three to four years."

https://www.dnv.com/feature/tesla-batte … ition.html

Tesla state they are looking to increase battery output per weight by over 50% within 2 to 3 years.

So I am thinking that 300 Whes per Kg is definitely achievable by the time of the first human flight to Mars - no earlier than 2026. It's a reasonable supposition I think, especially as cost will not be an issue for Mission One.

Once a base is established on Mars, the "energy on arrival" issue becomes of little importance, so it's really just a Mission One problem...maybe Mission 2 to some extent as well.

Whether Musk chooses to bring solar panels with batteries or a nuclear reactor for early missions is his choice, as it is his money to burn. And burn it will. I have already shown his plans for a million person human society on Mars has zero prospects based on solar only energy. Solar PV just doesn't generate a high enough net energy return to make this level of industrial development possible on Mars. So far as long term energy needs are concerned, solar power is a dead end on Mars.

Two 1MW nuclear reactors going into orbit would be subject to much more regulatory control. It could take years to get permission and there could be worlwide protests. So it's not just a decision for Musk to make. And I don't think you showed any such thing!

This sort of thing isn't possible on Earth, either. Since the global financial crisis, interest rates have dropped beneath inflation. Those solar and wind capital costs, that looked so unaffordable before 2008, have now magically disappeared.
The same thing happened to those previously unaffordable shale oil capital costs. This has given a lot of people some very misleading impressions about what is going to be possible long term, when interest rates rise into positive numbers again, as eventually they must. It will be a very uncomfortable realisation for renewable energy enthusiasts. For anyone expecting shale oil to be a long-term solution as well.

As I have responded before - with evidence - these low below inflation rates are only available to governments. Any business wishing to borrow will be paying well above the national interest rate and above the inflation rate. I think the current standard borrowing rate for business is around 6%.

The reduction in solar and wind energy costs has been on a pretty steady downward path bar a couple of blips. It had been falling steadily for decades before 2008.

kbd512 · 2021-05-11 16:12:20

Louis,

400Wh/kg is for the battery cell itself, which does not include any of the other packaging required to turn it into a functional battery pack / energy storage solution. Rolls Royce used 250Wh/kg Tesla-manufactured Lithium-ion batteries in their electric aircraft by stripping away nearly all of the battery pack packaging from existing Tesla battery packs, and arrived at an energy density of 186Wh/kg, IIRC. That's 74.4% of the battery energy density figure. Using 75% as the pack-level energy density, we arrive at 300Wh/kg for this new battery, which is an improvement of 50Wh/kg over the smaller cells. That gravimetric energy density improvement was arrived at by applying the same cell technology to a much larger "jelly roll" to provide that extra 50Wh/kg of gravimetric energy density improvement. The underlying electrochemical technology itself hasn't improved in energy density.

What difference do you think that makes?

Some more simple math:

9,000,000Wh / 240Wh/kg = 37,500kg <- 2021 Tesla Roadster pack-level energy density (240Wh/kg)
9,000,000Wh / 300Wh/kg = 30,000kg <- This is where you are with 400Wh/kg batteries that are 75% battery by weight, at the pack level
9,000,000Wh / 2,500Wh/kg = 3,600kg <- This is where you need to be
9,000,000Wh / 8,340Wh/kg = 1,079kg <- This is where the 60% efficient Mercedes-Benz hybrid internal combustion engine is, in terms of fuel weight
9,000,000Wh / 22,394,000Wh/kg = 0.4kg <- This is where U235 is

36 years <- This is how long it took Lithium-ion batteries to achieve 400Wh/kg at the cell level

2,500Wh/kg / 400Wh/kg = 6.25 <- this is your gravimetric cell energy density multiplier (how long it actually took to achieve 400Wh/kg), relative to the length of time required to achieve
6.25 * 36 years = 225 years <- Unless magic happens, this is how long it will take for production-ready Lithium-ion batteries to compete with 18% efficient internal combustion engines. Every attempt to apply chintzy mathematics tricks won't change how long it actually took to go from prototype to 400Wh/kg.

Maybe you still can't figure this one out, but any mathematics teacher worth his or her salt would have to, in order to make a city on Mars feasible in any sense.

If the battery can last through 5,000 cycles, then 2,009kg of U235 is required to supply 45,000,000,000Wh worth of energy, which is 15 times lower than a battery that supplies the same amount of energy through 5,000 charge / discharge cycles. Since current practical batteries supply about 1,000 cycles at 80% depth-of-discharge, you need around 150,000kg of batteries, which is around 75 times more weight devoted to batteries. If you scale up the power requirement, battery capacity scales linearly with weight. Reactor output power does not scale linearly with weight. 2,009kg of Uranium occupies a volume of around 1/10th of a cubic meter, so storage dimensions for Uranium metal are incredibly compact. A single light vehicle could feasibly move 763kg on Mars. 57,000kg is the weight a medium-class main battle tank here on Earth.

If batteries had approximately the same energy density as gasoline, then I would be here helping to make your argument for you. I can't do anything about the fact that they don't.

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