Going Solar...the best solution for Mars.

SpaceNut · 2018-06-19 19:49:23

filter dust can be removed by backward air flow from inside the chamber after the filter to knock the dust off simulat to a water tank that filters iron from the water you backflush the water back out of the input from internally switching direcxt of good water back out the inlet.

kbd512 · 2018-06-20 05:43:32

Thanks for the info on NASA's ISPP efforts. It's good to know that at least someone there is working on it.

Regarding the SoNick batteries, there's probably something that can kill just about any battery. Short of dunking the battery in sea water, the cells are well sealed, so I can't imagine any other conditions where those cells would pose a hazard to anyone. The batteries in the link I posted had third party testing that included an immersion test with punctured cells. They still passed.

PNNL came up with a SoNick cell technology that supposedly improved the energy density of the state-of-the-art by about 30% and lowered their operating temperature at the same time. A ~110Wh/kg SoNick pack would make an attractive indoor battery that could stay inside the habitat. There's no measurable cell degradation after 4,000 cycles and it's ability to handle transient current draws is pretty incredible. It's powerful enough for low power stationary applications where mass is not absolutely critical, but reliability and good cell behavior is. The low cost of the cells, relative to more energetic Li-Ion's, and simple construction is an added bonus.

louis · 2018-06-20 16:35:21

Plenty of insolation around to take a selfie during the "massive dust storm":

https://www.teslarati.com/tesla-model-3 … elon-musk/

And Curiosity is in Gale Crater aka "a dust bowl".

kbd512 · 2018-06-20 17:33:38

Louis,

Curiosity can take pictures at night, too. The camera has a LED flash integrated into it and more powerful cameras than Spirit and Opportunity were capable of supplying electricity to. That's what nuclear power enabled. The heat from the Plutonium keeps the electronics and batteries warm.

SpaceNut · 2018-06-20 20:30:32

Its the best reason to have the life support be nuclear while using the day time light to work with as there is little reason to be running 3 shifts of operations.
There has been not a peep from Nasa for the storms progress or diminishing in size or opacity.
http://www.foxnews.com/science/2018/06/ … -mars.html
a 3 day comparison image
https://marsprogram.jpl.nasa.gov/resour … ust-storm/

Todays date:
Martian Dust Storm Grows Global; Curiosity Captures Photos of Thickening Haze

The Martian dust storm has grown in size and is now officially a "planet-encircling" (or "global") dust event.
Though Curiosity is on the other side of Mars from Opportunity, dust has steadily increased over it, more than doubling over the weekend. The sunlight-blocking haze, called "tau," is now above 8.0 at Gale Crater -- the highest tau the mission has ever recorded. Tau was last measured near 11 over Opportunity, thick enough that accurate measurements are no longer possible for Mars' oldest active rover.

SpaceNut · 2018-06-27 18:25:00

http://www.thespacereview.com/article/3487/1

The key governing the design and sizing of a ground based solar cell power system is its performance on Mars. The performance is driven by the reduced radiant flux (compared to Earth or space-based) from to the added distance from the sun and Martian atmosphere.
Mars only receives a flux power of about 593 watts per square meter from the Sun. If we assume one megawatt as the needed power, the calculation to estimate how much power a given area of solar panels will output is:
E=AϵFrp
where E is the energy in watts, A is the size of the solar panel, ϵ is the efficiency, F is the flux received, and rp is the “performance ratio” of the solar panels (losses due to shading, dust, circuitry, etc.)
The blanket power density efficiency of thin-film solar panel arrays is about 684 watts per kilogram for low-cost advanced silicon cells on stainless steel foil. In 2016, Ascent Solar Technologies, Inc. announced it had achieved a major breakthrough in power-to-weight ratio for its superlight solar module, delivering over 1,700 watts of power per kilogram, operating in the space environment. However, the power density jumps to 2,440 watts per kilogram for 1 mil Kapton polymer for demonstrated higher cell efficiencies (10.7–12 percent.)
The MIT researchers also calculated it would take two astronauts 17 hours to construct such an array. Alternatively, they could get a robotic system, like that being developed by OffWorld, to do it. So adequate system deployment solutions exist and this should not be a design issue.
In this review of propellant production plant power options, it is assumed that the arrays are positioned at 25° north. If we assume that we have the highest solar array efficiency of 12.5 percent performance ratio, this equation can be solved to see the plant’s solar array area would be just over 56,200 square meters, or about 0.06 square kilometers. For comparison, a football field is about 5,000 square meters, so the ground based solar array would need to have a minimum starting total collection area equivalent to more than 11 football fields during the Martian day.
However for continuous day/night production, a power storage subsystem will be required. Power storage options include batteries and more exotic options, such as storage flywheels. For this review, rechargeable batteries are assumed for nighttime production due to their high maturity.
Batteries used during the night will need to be charged during the day. This means additional solar arrays that are dedicated to charging the batteries will also be needed. As an example of reasonably highly efficient rechargeable batteries, Tesla’s commercial power pack batteries each have an energy capacity of 210 kilowatt-hours (AC). These lithium ion battery packs also have a 100 percent depth of discharge and mass around 1,625 kilograms each.11
To transport and emplace just the propellant production solar arrays using the highest efficient power-to-mass ratio arrays (12 percent) would require transport of about 820 kilograms for the thin-film solar panel arrays to Mars. This is double the array capability for daytime operation to account for daily solar charging of batteries. It does not include the needed backup batteries, power conditioning and power support subsystems. If we add the mass of “Tesla Wall-equivalent” batteries for overnight operations, this increases the mass that will need to be transported and emplaced to just over eight metric tons. Even if this were again double, the power production system mass due to associated equipment, power conditioning, support equipment, and initial estimating errors, falls well within a single BFR Mars transport capability of 150 metric tons.

louis · 2018-06-28 05:29:04

Just a few comments:

1. Any PV array for propellant production also needs to compensate for a worst case dust scenario.

2. The need for night time power is often overstated I feel. During sol-light hours you can meet all your hot water and heating needs, slow cook meals, recycle water and process the oxygen and other gases you need to breathe. So what energy exactly is required at night time? Lighting and some pumps (to circulate air and water)... maybe your TV/video screen. Not much more I think.

3. Flisom who produce space rated PV panelling have 20% efficiency thin film flexible solar. I think it is reasonable to assume we can achieve 20% efficiency.

SpaceNut wrote:

http://www.thespacereview.com/article/3487/1
The key governing the design and sizing of a ground based solar cell power system is its performance on Mars. The performance is driven by the reduced radiant flux (compared to Earth or space-based) from to the added distance from the sun and Martian atmosphere.
Mars only receives a flux power of about 593 watts per square meter from the Sun. If we assume one megawatt as the needed power, the calculation to estimate how much power a given area of solar panels will output is:
E=AϵFrp
where E is the energy in watts, A is the size of the solar panel, ϵ is the efficiency, F is the flux received, and rp is the “performance ratio” of the solar panels (losses due to shading, dust, circuitry, etc.)
The blanket power density efficiency of thin-film solar panel arrays is about 684 watts per kilogram for low-cost advanced silicon cells on stainless steel foil. In 2016, Ascent Solar Technologies, Inc. announced it had achieved a major breakthrough in power-to-weight ratio for its superlight solar module, delivering over 1,700 watts of power per kilogram, operating in the space environment. However, the power density jumps to 2,440 watts per kilogram for 1 mil Kapton polymer for demonstrated higher cell efficiencies (10.7–12 percent.)
The MIT researchers also calculated it would take two astronauts 17 hours to construct such an array. Alternatively, they could get a robotic system, like that being developed by OffWorld, to do it. So adequate system deployment solutions exist and this should not be a design issue.
In this review of propellant production plant power options, it is assumed that the arrays are positioned at 25° north. If we assume that we have the highest solar array efficiency of 12.5 percent performance ratio, this equation can be solved to see the plant’s solar array area would be just over 56,200 square meters, or about 0.06 square kilometers. For comparison, a football field is about 5,000 square meters, so the ground based solar array would need to have a minimum starting total collection area equivalent to more than 11 football fields during the Martian day.
However for continuous day/night production, a power storage subsystem will be required. Power storage options include batteries and more exotic options, such as storage flywheels. For this review, rechargeable batteries are assumed for nighttime production due to their high maturity.
Batteries used during the night will need to be charged during the day. This means additional solar arrays that are dedicated to charging the batteries will also be needed. As an example of reasonably highly efficient rechargeable batteries, Tesla’s commercial power pack batteries each have an energy capacity of 210 kilowatt-hours (AC). These lithium ion battery packs also have a 100 percent depth of discharge and mass around 1,625 kilograms each.11
To transport and emplace just the propellant production solar arrays using the highest efficient power-to-mass ratio arrays (12 percent) would require transport of about 820 kilograms for the thin-film solar panel arrays to Mars. This is double the array capability for daytime operation to account for daily solar charging of batteries. It does not include the needed backup batteries, power conditioning and power support subsystems. If we add the mass of “Tesla Wall-equivalent” batteries for overnight operations, this increases the mass that will need to be transported and emplaced to just over eight metric tons. Even if this were again double, the power production system mass due to associated equipment, power conditioning, support equipment, and initial estimating errors, falls well within a single BFR Mars transport capability of 150 metric tons.

kbd512 · 2018-06-28 07:17:22

SpaceNut,

Ascent Solar's advertised space applications product actually achieves 1,125W/kg to 1,400W/kg in LEO. It's variable because they can vary the output voltage of the cell by adding more electrical connections, which is another major advantage their product delivers. Those figures come from actual equipment in LEO financed by JAXA. 1,700W/kg to 2,440W/kg may be possible, but the numbers I provided are for actual commercial products in production today, as sold to their customers (presently, NASA, JAXA, ESA, US DoD, Airbus Defense, and a variety of small satellite fabricators for use in cube sats). Their products are made in the US and China.

I said 1,000W/kg in my posts because I'm adding the mass of the protective ESD dust repulsion coating and the mass of the fabricated single axis Sun tracking truss structure on which to mount the array for applications on the surface of Mars. It's impractical from a storage density standpoint to use deployable arrays at the scale we're talking about. However, an extreme packaging density is achievable by fabricating the arrays on Mars. Tethers Unlimited Inc has demonstrated primary and secondary truss structure fabrication with low cost robots, but super grade robots from Boston Dynamics are required for this application. I don't know why everyone is commenting on how large the array is. They should be content to have the technology required to make this work.

Tesla battery packs are not space rated hardware, nor anything remotely resembling space rated hardware, so quoting mass figures for those battery packs is just being silly since nobody is ever putting one of those in space. Maybe the person who wrote that article imagined that there was an Earth-like environment on Mars that was particularly amenable to battery packs with a -30C to +50C rating, but there isn't. Between 2012 and 2015, Gale Crater's average high was -23C in March, the average low was -88C, and the record low was -114C. That rinky-dink little air-cooled enclosure for the batteries won't cut it. The battery pack is 1,622kg, but the inverter is 1,200kg. The pack's delivered energy rating was tested at 25C.

How can you calculate the array of the solar array correctly and then write total nonsense about the mass of the battery pack and how much energy it can actually store? Some of these articles are pretty amateurish. Alternatively, there's a lot of magical thinking going on. If the BFS explodes on impact, there goes your entire power storage capability. I really hope these people weren't thinking about putting people aboard the same BFS. A single faulty battery is all that's required to destroy the ship and kill everyone aboard. If these cells are the same cells in their Model S, then I think I'd pass.

louis · 2018-06-28 11:31:43

Kbd,

What is your estimate of average electrical power produced per sq. metre per sol in KwHs on the most efficient (let's say 20%) and yet practical lightweight PV panelling on the surface of Mars (equatorial region)?

kbd512 wrote:

SpaceNut,
Ascent Solar's advertised space applications product actually achieves 1,125W/kg to 1,400W/kg in LEO. It's variable because they can vary the output voltage of the cell by adding more electrical connections, which is another major advantage their product delivers. Those figures come from actual equipment in LEO financed by JAXA. 1,700W/kg to 2,440W/kg may be possible, but the numbers I provided are for actual commercial products in production today, as sold to their customers (presently, NASA, JAXA, ESA, US DoD, Airbus Defense, and a variety of small satellite fabricators for use in cube sats). Their products are made in the US and China.
I said 1,000W/kg in my posts because I'm adding the mass of the protective ESD dust repulsion coating and the mass of the fabricated single axis Sun tracking truss structure on which to mount the array for applications on the surface of Mars. It's impractical from a storage density standpoint to use deployable arrays at the scale we're talking about. However, an extreme packaging density is achievable by fabricating the arrays on Mars. Tethers Unlimited Inc has demonstrated primary and secondary truss structure fabrication with low cost robots, but super grade robots from Boston Dynamics are required for this application. I don't know why everyone is commenting on how large the array is. They should be content to have the technology required to make this work.
Tesla battery packs are not space rated hardware, nor anything remotely resembling space rated hardware, so quoting mass figures for those battery packs is just being silly since nobody is ever putting one of those in space. Maybe the person who wrote that article imagined that there was an Earth-like environment on Mars that was particularly amenable to battery packs with a -30C to +50C rating, but there isn't. Between 2012 and 2015, Gale Crater's average high was -23C in March, the average low was -88C, and the record low was -114C. That rinky-dink little air-cooled enclosure for the batteries won't cut it. The battery pack is 1,622kg, but the inverter is 1,200kg. The pack's delivered energy rating was tested at 25C.
How can you calculate the array of the solar array correctly and then write total nonsense about the mass of the battery pack and how much energy it can actually store? Some of these articles are pretty amateurish. Alternatively, there's a lot of magical thinking going on. If the BFS explodes on impact, there goes your entire power storage capability. I really hope these people weren't thinking about putting people aboard the same BFS. A single faulty battery is all that's required to destroy the ship and kill everyone aboard. If these cells are the same cells in their Model S, then I think I'd pass.

SpaceNut · 2018-06-28 17:04:53

Ascent Solar's advertised space applications product 2009 https://www.printedelectronicsworld.com … production

https://en.wikipedia.org/wiki/Ascent_Solar

CIGS panels currently allow for 85 watts/meter, and 48 watts/kg

https://www.businesswire.com/news/home/ … s-Selected

There are lots of selection of there page http://www.ascentsolar.com/

http://www.ascentsolar.com/downloads/ASTI_Space.pdf

kbd512 · 2018-06-29 04:17:27

Louis,

That can't be precisely calculated by hand. I'd have to write some software to do it or find a piece of software that does it. There are data that I don't have that are required input to perform the calculation. If I had the data, then I could write a program to calculate it. When I look at the feasibility of these concepts, I worry a lot more about power-to-weight ratio, packaging density, and other fundamental issues like the ability to withstand the thermal and radiation environment. The thin film solar technology, combined with lightweight truss structures, makes multi-megawatt scale solar power arrays on the surface of Mars very feasible and the only near-term practical method that I've seen.

You can simplify the equation "E=AϵFrp" shown above to show peak output achievable without resistance losses and so forth, but to determine time-averaged power output over the course of a day, you need to integrate the results of the calculation with measurements of the received solar flux.

"A" is the panel area square meters
"ϵ" is the conversion efficiency of Watts of input solar radiation into Watts of output electrical power
"F" is the solar radiation flux received in Watts
"rp" is the losses from electrical resistance (assume no shading; I've no idea how to calculate the diffuse input radiation component from dust and other atmospheric effects)

There is some information about the thin film cells I don't have regarding internal resistance and Ascent Solar's website does not provide that information. Let's look at Ascent Solar product "B-110-950-220". The PDF says it has a mass of 11g and area of 970cm^2, so 10 of these individual cells fit in 1m^2 and weigh 110g. Operating temperature range is -140C to 125C and excursion temperature range is -196C to 250C, so we're still good for operation on Mars. Pmax for that product is 9.5Watts, so 95W/m^2 and 855W/kg. That figure was provided for LEO, though, because the product is intended to provide electrical power for cube stats. LEO receives 1,361W/m^2, so 1,320.17W actually strike the cell surface area. If this product outputs 95W, then actual efficiency is ~7.2%. The temperature coefficients, part of the fine print regarding actual performance, must also be considered.

Therefore 1m^2 containing 10 of those cells would produce 42.7W/m^2 on Mars during hours of "Peak Sun", ignoring the resistance of the cell interconnections, temperature coefficients, and atmospheric effects. A 20% efficient panel would produce a stellar 118.6W/m^2. One of the remarkable aspects of thin film arrays is just how much more power they produce than traditional silicon-based cells in off-nominal conditions, which is to say without direct beam power received from the Sun. To achieve a peak array output power of 1MWe with these cells a 23,419m^2 array is required. That equates to 153m by 153m array. A NFL regulation football field is 109.728m by 48.768m for comparison purposes. An actual solar array would leave space between the panels to prevent shading and to allow access for repair, so double that area. After we do that, we're relatively close to what they estimated using the less efficient technology. More panels will have to be added to overcome issues with electrical resistance and then we're very near to what they estimated, with respect to array size. The panels would weigh 2,576kg using current technology. However, the 14% efficient lab products still under test are nearing completion. That would weigh about 1,165kg, thus my blanket general comment / assertion on ~.5MWe/t with the truss structure, tracking motors, wiring, and excess capacity required to meet the performance objective. If that 2,440W/kg product comes to market in the next few years, then a 1t/MWe array is well within the realm of feasibility.

The battery issue is a much tougher nut to crack. I've been trying to come up with "wind tunnel" cell geometries whereby compressed CO2 regulates battery pack temperature so that far less packaging and thermal insulation mass is required. Imagine you have a battery powered compressor / gas turbine with a tank of liquid CO2 on one end and a stack of cylindrical battery cells on the other that are mounted inside a tube. To remove waste heat, you push expanding CO2 from the storage tank through the tube surrounding the battery pack. The CO2 carries the waste heat away. To warm the pack, you push exhaust gas from the compressor / gas turbine outlet directly through the tube. Some sort of exhaust valve on the opposite end of the battery tube can regulate flow rate.

[CO2 storage tank]-[compressor]-[bypass valve]-[battery tube]-[power inverter]-[exhaust valve]

The bypass valve blows cold CO2 from the storage tank or hot CO2 from the compressor exhaust through the battery tube. The storage tank removes heat and the compressor exhaust adds heat, as required. The exhaust valve controls the flow rate. The battery and inverter stacks are modular "hockey pucks" that can form longer tubes to store more Amp-hours.

Put a fat magic marker inside an empty toilet paper roll. Imagine that the magic marker represents the battery and the toilet paper roll is the tube that temporarily contains gas from a CO2 tank that's pushed between the magic marker and toilet paper roll to regulate the temperature of the magic marker. Now stack another magic marker and toilet paper roll on top. That's the basic concept.

Edit:
Here's a link providing a picture from the Toyota Prius battery thermal management system to illustrate the basic concept:

A review of Battery Thermal Management System

In the end, this is just a forced air cooling system modified for use on Mars.

Edit #2:

If you wanted to use some form of liquid coolant run directly through holes or channels in the hockey pucks, then you could do that, too. That might work better for both space, the moon, and Mars. Feel free to take my ideas and develop them, call them your own, etc. There's nothing fundamentally new here and I don't claim to have actually come up with anything new. I just present novel modular packaging schemes for materials canisters, battery canisters, power inverter canisters, CO2 canisters, etc, that all have standardized dimensions to enable robotic materials handling, wherever possible.

Last edited by kbd512 (2018-06-29 04:45:13)

louis · 2018-06-29 05:24:58

I approached the problem from a different angle and I think got a similar result...

The tilted figure for this location in Arizona is 6.66 Kwhs per sq. metre. (I believe Arizona has one of the highest figures on the planet, and we would be looking for an equivalent location on Mars).

https://solarenergylocal.com/states/arizona/scottsdale/

Applying the average of 43% for Mars insolation (compared to Earth's) that gives an equivalent figure of 2.86 Kwhs. With an efficiency of 20% on your panels, that would produce 0.57 Kwhes per sq metre per sol.

So, in the absence of dust storms, a 100 x 100 metre facility would produce 10,000 x 0.57 = 5,700 Kwhes per sol. Probably the bulk of that would be produced over a five hour period. That would give an average of about 465 Kwes during sol-light, but with peaks around 1 Mw.

I think another thing to look at would be whether you could use reflectors to up output. In the right location these might be very effective. Given the clement weather on Mars, the reflectors could be very lightweight - reflective foil set up on aluminium frames .

This experiment in the field suggests reflectors could boost output by 30% with a range between 18% and 45% depending on tilt optimisation and the quality of the reflectors.

http://theconversation.com/can-mirrors- … iffs-90663

Might be worth looking at in a Mars mission context where mass and ease of deployment are more key factors than cost.

However, I was thinking of much larger reflectors perhaps deployed on hillsides around the array.

kbd512 wrote:

Louis,
That can't be precisely calculated by hand. I'd have to write some software to do it or find a piece of software that does it. There are data that I don't have that are required input to perform the calculation. If I had the data, then I could write a program to calculate it. When I look at the feasibility of these concepts, I worry a lot more about power-to-weight ratio, packaging density, and other fundamental issues like the ability to withstand the thermal and radiation environment. The thin film solar technology, combined with lightweight truss structures, makes multi-megawatt scale solar power arrays on the surface of Mars very feasible and the only near-term practical method that I've seen.
You can simplify the equation "E=AϵFrp" shown above to show peak output achievable without resistance losses and so forth, but to determine time-averaged power output over the course of a day, you need to integrate the results of the calculation with measurements of the received solar flux.
"A" is the panel area square meters
"ϵ" is the conversion efficiency of Watts of input solar radiation into Watts of output electrical power
"F" is the solar radiation flux received in Watts
"rp" is the losses from electrical resistance (assume no shading; I've no idea how to calculate the diffuse input radiation component from dust and other atmospheric effects)
There is some information about the thin film cells I don't have regarding internal resistance and Ascent Solar's website does not provide that information. Let's look at Ascent Solar product "B-110-950-220". The PDF says it has a mass of 11g and area of 970cm^2, so 10 of these individual cells fit in 1m^2 and weigh 110g. Operating temperature range is -140C to 125C and excursion temperature range is -196C to 250C, so we're still good for operation on Mars. Pmax for that product is 9.5Watts, so 95W/m^2 and 855W/kg. That figure was provided for LEO, though, because the product is intended to provide electrical power for cube stats. LEO receives 1,361W/m^2, so 1,320.17W actually strike the cell surface area. If this product outputs 95W, then actual efficiency is ~7.2%. The temperature coefficients, part of the fine print regarding actual performance, must also be considered.
Therefore 1m^2 containing 10 of those cells would produce 42.7W/m^2 on Mars during hours of "Peak Sun", ignoring the resistance of the cell interconnections, temperature coefficients, and atmospheric effects. A 20% efficient panel would produce a stellar 118.6W/m^2. One of the remarkable aspects of thin film arrays is just how much more power they produce than traditional silicon-based cells in off-nominal conditions, which is to say without direct beam power received from the Sun. To achieve a peak array output power of 1MWe with these cells a 23,419m^2 array is required. That equates to 153m by 153m array. A NFL regulation football field is 109.728m by 48.768m for comparison purposes. An actual solar array would leave space between the panels to prevent shading and to allow access for repair, so double that area. After we do that, we're relatively close to what they estimated using the less efficient technology. More panels will have to be added to overcome issues with electrical resistance and then we're very near to what they estimated, with respect to array size. The panels would weigh 2,576kg using current technology. However, the 14% efficient lab products still under test are nearing completion. That would weigh about 1,165kg, thus my blanket general comment / assertion on ~.5MWe/t with the truss structure, tracking motors, wiring, and excess capacity required to meet the performance objective. If that 2,440W/kg product comes to market in the next few years, then a 1t/MWe array is well within the realm of feasibility.

Last edited by louis (2018-06-29 05:25:27)

SpaceNut · 2018-06-29 10:28:31

Sure reflectors but they will become dust covered and the amount of what will be gained will be offset also by the dust in the air and on the solar panels as well. This is wieght versus gain again. The amount of solar gain also will vary day to day as well due to that dust such that the exact numbers will be off over time if we are looking for what you have calculated as the max number.

kbd512 · 2018-06-29 15:07:46

My added emphasis commentary on the array sizing problem is that epsilon is not a fixed value. It varies with temperature. Furthermore, the output of a thin film array in off-nominal conditions is more than for silicon-based panels. As always, the most output power is obtained by pointing the array directly into the beam. That's why single axis array steering is highly desirable, very near to a requirement for an array of the desired output level.

To calculate the "rp" of the array, the resistance of all the wiring for both cell interconnections, inverters, transformers, and output cabling must be determined. Resistance losses from the wiring, inverters, and transformers will be considerable. The desired output voltage and current rating for the wiring and any transformers between the array and point of use (specific electrical power application) should also be calculated. A lot of industrial equipment uses 440 3-phase AC here in the US, but for a wiring run of 5km+, a higher voltage should be used to reduce resistance losses and the mass of the wiring required. The voltage limitation for Ascent Solar's thin film technology is stated as 270V, so that should be taken into account when calculating the gauge of wiring for cell interconnections and the feeds to the inverter.

We should go through this exercise for arrays made from actual products and the lab products that will become available in the near term. I can see the 14% efficient product becoming available in the near term, but that 20% efficient product is a bit of a stretch, given prototypical rate of improvement on array efficiency. Recall how long it took NASA and Vanguard Aerospace (subsequently purchased by Ascent Solar) to complete initial development of the product. As better products become available, I'm sure they'll be incorporated. I would like to develop baselines using known equipment, rather than speculate on what might become available in another decade. Presently available and near term products indicate that this is a technically feasible project, rather than a science fiction idea.

louis · 2018-06-29 16:45:10

These reflectors can be maintained just like solar panelling can. There's no reason why robot rovers shouldn't patrol the reflectors and either blow dust off or get it to detach by pulling on guy ropes thus making the reflectors move. I have read that the rovers are able to shift a lot of dust from their panels simply by moving them. The good thing about reflectors is they don't require the additional PMAD.

On Earth setting up reflectors is a complex and resource-intensive business because of strong winds, rain, hail and all the rest. It should be a lot easier on Mars simply to unroll lightweight reflectors attached to aluminium or similar frames.

SpaceNut wrote:

Sure reflectors but they will become dust covered and the amount of what will be gained will be offset also by the dust in the air and on the solar panels as well. This is wieght versus gain again. The amount of solar gain also will vary day to day as well due to that dust such that the exact numbers will be off over time if we are looking for what you have calculated as the max number.

louis · 2018-06-29 16:52:27

I'd be surprised if wiring runs of more than 200 metres were required for Mission One.

I don't know whether this product can be space-rated but if it can we might already be there...

"On 17 January 2013, Empa announced that its CIGS flexible solar cells achieved 20.4% photovoltaic conversion efficiency – a world record for CIGS technology that equals the record efficiency of polycrystalline Si wafer solar cells."

https://flisom.com/industries/

kbd512 wrote:

My added emphasis commentary on the array sizing problem is that epsilon is not a fixed value. It varies with temperature. Furthermore, the output of a thin film array in off-nominal conditions is more than for silicon-based panels. As always, the most output power is obtained by pointing the array directly into the beam. That's why single axis array steering is highly desirable, very near to a requirement for an array of the desired output level.
To calculate the "rp" of the array, the resistance of all the wiring for both cell interconnections, inverters, transformers, and output cabling must be determined. Resistance losses from the wiring, inverters, and transformers will be considerable. The desired output voltage and current rating for the wiring and any transformers between the array and point of use (specific electrical power application) should also be calculated. A lot of industrial equipment uses 440 3-phase AC here in the US, but for a wiring run of 5km+, a higher voltage should be used to reduce resistance losses and the mass of the wiring required. The voltage limitation for Ascent Solar's thin film technology is stated as 270V, so that should be taken into account when calculating the gauge of wiring for cell interconnections and the feeds to the inverter.
We should go through this exercise for arrays made from actual products and the lab products that will become available in the near term. I can see the 14% efficient product becoming available in the near term, but that 20% efficient product is a bit of a stretch, given prototypical rate of improvement on array efficiency. Recall how long it took NASA and Vanguard Aerospace (subsequently purchased by Ascent Solar) to complete initial development of the product. As better products become available, I'm sure they'll be incorporated. I would like to develop baselines using known equipment, rather than speculate on what might become available in another decade. Presently available and near term products indicate that this is a technically feasible project, rather than a science fiction idea.

SpaceNut · 2018-06-29 17:23:44

The solar plan keeps changing with all sorts of wish list items that are eating up the BFR payload capacity and if a falcon is 70 meters tall which will be short for the BFR and where its best to leave the batteries then the cables will get long in a hurry as we are not building buildings for anything until several bfr missions are in the bag. With length so does the mass grow as to reduce loss the conductor size will increase or the number of parrellel wires will be required which is more mass. Large conductors are not flexible and under the cold will most likely crack the insulation as they are moved to support being connected to the solar array. What comes out of the array is DC voltage which the lower the voltage is and with high levels of current does change that loss over the length of the power wires hence means having a high voltage output.
Adding more robotics for automated up keeping or install to steady state running of the arrays increase complexity can in all likelyhood ride the risk of a unit or system failing.

louis · 2018-06-29 17:53:27

A 100 metre x 100 metre PV array might well be sufficient to serve a Space X Mission One. Difficult to know until we have a better fix on the energy-hungry propellant plant requirement.

I really can't see cabling and PMAD eating hugely into the tonnage allowance. Rovers can have multiple function. Keeping the array in good condition seems reasonable.

A PV array of 10,000 sq metres with ten 100 metre "alleys" would require a maintenance rover to travel a distance of a little over 1 Km. Pausing for say 5 seconds every metre to blow dust off, and 5 seconds to move along and reposition, that would take one Rover 27 hours to complete the task. So a team of 3 rovers could easily undertake that in one sol. In normal conditions probably a once a week visit would suffice. There might be quicker ways. If the PV panelling is held in position on taut wires, it might be sufficient to twang the wires to shake off dust.

SpaceNut wrote:

The solar plan keeps changing with all sorts of wish list items that are eating up the BFR payload capacity and if a falcon is 70 meters tall which will be short for the BFR and where its best to leave the batteries then the cables will get long in a hurry as we are not building buildings for anything until several bfr missions are in the bag. With length so does the mass grow as to reduce loss the conductor size will increase or the number of parrellel wires will be required which is more mass. Large conductors are not flexible and under the cold will most likely crack the insulation as they are moved to support being connected to the solar array. What comes out of the array is DC voltage which the lower the voltage is and with high levels of current does change that loss over the length of the power wires hence means having a high voltage output.
Adding more robotics for automated up keeping or install to steady state running of the arrays increase complexity can in all likelyhood ride the risk of a unit or system failing.

Last edited by louis (2018-06-30 07:52:11)

kbd512 · 2018-06-29 20:32:59

Louis,

There's no such thing as a solar array made of the lightest materials available located 1km away from a launch vehicle with a rocket that has 4 engines with RS-25 thrust levels. The rocket will literally blow the array away at that distance. Landing another BFS 1km away from the first is probably out of the question as well. People are just going to have to get used to the fact that everything is going to be a little heavier than they'd like it to be and separation distances between rockets will also be greater than they'd like. PMAD will be substantially heavier than the array, for example.

It's possible to build an array near a BFS that will never fly again that's merely used to store propellant in purpose built tanks (metal alloy versus composite header tanks) with the propellant plant built into the cargo area. A pair of purpose built propellant trucks could then carry the propellant to the BFS carrying the humans in batches. If the refueling probes are located on the tail of the BFS, then this is probably the best way to accomplish the refueling task. It also happens to be the way we do it on Earth. Tanker trucks load propellant into the storage tanks at KSC and elsewhere.

I keep saying that a series of Cygnus / HIAD landers could deliver everything to Mars using Falcon Heavy because that's the most realistic way to do this. All the technology requires testing and fabrication ahead of a human mission. F9H is available right now, as is the solar panel technology, and the robots could be available in the near term with adequate funding and prioritization.

I intended for the construction spider bots to also have the ability to mount CO2 tanks to blow the dust off of arrays. I want all the canisters to be the same size for manipulation using the front two appendages.

Here's a YouTube video demonstrating one of the ways in which the robot could propel itself:

Festo – BionicWheelBot (English/Deutsch)

Here's a YouTube video talking about the Tethers Unlimited Spider Fab robot:

NASA Designs 3D Printing Spider

Here's a YouTube video showing the "trusselator" technology intended to be included with the Spider Fab robot deploying a thin film solar panel:

NASA 360 Talks - Building in Space

Quaoar · 2018-06-30 04:54:25

kbd512 wrote:

There's no such thing as a solar array made of the lightest materials available located 1km away from a launch vehicle with a rocket that has 4 engines with RS-25 thrust levels. The rocket will literally blow the array away at that distance. Landing another BFS 1km away from the first is probably out of the question as well. People are just going to have to get used to the fact that everything is going to be a little heavier than they'd like it to be and separation distances between rockets will also be greater than they'd like. PMAD will be substantially heavier than the array, for example.

How many km is the safe BFS-landing range on Mars?

Last edited by Quaoar (2018-06-30 04:55:25)

louis · 2018-06-30 07:58:21

I had always assumed the BFS would be landed well away from where you would locate your hab and array. Although in theory the Mission One array could be disposable, I think we want to make continued use of it for Mission Two. So, yes, I don't see any problem with locating the array 1 Km away from the BFS. Obviously there would be a lot of pre-planning to make sure. 1km away at say 5 Kmph (in a rover going over rocks and boulders) is only a 12 minute ride. It would take only a few trips to get the hab up and running and install an initial array...perhaps 20 metres by 20. A few sols later you can create a faster road trail back to the BFS by removing boulders and rocks using a "cow catcher" rover working methodically.

kbd512 wrote:

Louis,
There's no such thing as a solar array made of the lightest materials available located 1km away from a launch vehicle with a rocket that has 4 engines with RS-25 thrust levels. The rocket will literally blow the array away at that distance. Landing another BFS 1km away from the first is probably out of the question as well. People are just going to have to get used to the fact that everything is going to be a little heavier than they'd like it to be and separation distances between rockets will also be greater than they'd like. PMAD will be substantially heavier than the array, for example.
It's possible to build an array near a BFS that will never fly again that's merely used to store propellant in purpose built tanks (metal alloy versus composite header tanks) with the propellant plant built into the cargo area. A pair of purpose built propellant trucks could then carry the propellant to the BFS carrying the humans in batches. If the refueling probes are located on the tail of the BFS, then this is probably the best way to accomplish the refueling task. It also happens to be the way we do it on Earth. Tanker trucks load propellant into the storage tanks at KSC and elsewhere.
I keep saying that a series of Cygnus / HIAD landers could deliver everything to Mars using Falcon Heavy because that's the most realistic way to do this. All the technology requires testing and fabrication ahead of a human mission. F9H is available right now, as is the solar panel technology, and the robots could be available in the near term with adequate funding and prioritization.
I intended for the construction spider bots to also have the ability to mount CO2 tanks to blow the dust off of arrays. I want all the canisters to be the same size for manipulation using the front two appendages.
Here's a YouTube video demonstrating one of the ways in which the robot could propel itself:
Festo – BionicWheelBot (English/Deutsch)
Here's a YouTube video talking about the Tethers Unlimited Spider Fab robot:
NASA Designs 3D Printing Spider
Here's a YouTube video showing the "trusselator" technology intended to be included with the Spider Fab robot deploying a thin film solar panel:
NASA 360 Talks - Building in Space

SpaceNut · 2018-06-30 08:48:14

Here are a few links with regards to wire/power lose for conductor size for a given distance AC or DC and a calculator.

https://www.altestore.com/howto/wire-si … tems-a106/

https://www.southwire.com/support/volta … ulator.htm

https://www.solar-electric.com/learning … ables.html

The long and short of cable wire size to distance is Mass increase for the wire to allow the power created to arrive at the useage point.

RobertDyck · 2018-06-30 11:01:56

One trick that Manitoba Hydro uses for long distance power transmission is high voltage DC. Most long distance power lines are 300,000 volt AC, but that loses power to EM. DC has no loss to EM, but you have to convert. Power loss for DC is directly related to current, so they use 900,000 volts (Bipole 1) or 1 million volts (Bipole 2) with relatively lower current (max 3,600 amps). That voltage is one conductor to the other, single conductor to ground is half that. The catch is some power loss due to switching power converter. Manitoba Hydro built power dams in northern Manitoba, most power used in southern Manitoba, primarily Winnipeg, so power lines are long: 895km (Bipole 1), or 937km (Bipole 2). Conductor is 4cm diameter stranded aluminum cable. (reference)

Last edited by RobertDyck (2018-06-30 17:17:03)

kbd512 · 2018-06-30 12:09:10

Quaoar,

The distance between the pads at KSC is 2,657m. I'm doubling that distance for Mars because I don't want a giant cloud of dust burying the solar power plant. I also want traffic patterns established so that BFS doesn't overfly the power plant or propellant plant. The extra 2.5km is "fudge factor" for off-nominal landings, thus 5km is a minimal prudent separation distance. 5km / 3 miles is walking distance. The viewing location at KSC is 5.8km / 3.6 miles from 39A. NASA doesn't allow anyone anywhere near the SpaceX rocket landing area and for good reason. Consider the speed at which BFS travels at just prior to landing. The BFS that contains the propellant plant can be closer to the power plant, say 2.5km, provided that it stays on Mars and arrives with the materials to build the array. An explosion at the propellant plant would likely throw debris at least that far. Remember that old saying the astronauts have? No problem is so bad that you can't make it worse. I think it applies here.

I would prefer stainless steel header tanks for storing the propellants. The surrounding composite tanks would function as a vacuum jacket for the inner header tanks to minimize heat transfer such that modest cryocooler input power can remove what little heat transfer occurs to permit indefinite storage. The propellant would be transferred to the passenger carrying BFS in batches using tanker trucks and loaded through the fueling lines located at the base of the vehicle.

Louis,

I can't think of any reason why rovers can't travel at a slow walker's pace on flat and level ground. If 5kph is as fast as a rover can manage, then you're better off bunny hopping along in .38g. I think 20kph is a more reasonable travel speed for a human operated rover. If the ground really is that littered with debris, such that it would impede a rover traveling at parking lot speeds, then you're not landing BFS there.

Anything that requires the level of effort associated with the construction of the solar power array is not a sacrificial tool. The BFS integrated propellant plant may not see service as a rocket afterwards, but it performs a vital function for crew return and serves as a source of spare engine parts for the passenger carrying BFS.

kbd512 · 2018-06-30 12:42:43

If the habitats and batteries are emplaced in vertical bore holes and co-located with their own power array, that drastically cuts down on the tonnage of wiring required for permanent subsurface habitation. If the special stainless steel propellant tanks aboard the cargo BFS were substituted for direct propellant loading into a set of propellant trucks using aluminum alloy tanks with MLI wrappers, then no changes to BFS are required. A containment structure around the propellant plant built into its cargo hold would direct the force of any explosion that may occur away from the power array, so the BFS propellant plant could be co-located with the power array. That gets rid of most of the transmission wiring from the array to the propellant plant. If the PMAD was co-located with the propellant plant, then that gets rid of anything really heavy that has to be transported to the surface. The propellant trucks would not be powered, just tanks on wheels that the battery operated regolith rovers would tow to the passenger carrying BFS for refueling. If the passengers stay in temporary Cygnus surface shelters that the regolith rovers partially bury, then that takes care of the radiation shielding issue and no humans are anywhere near BFS during propellant loading. The trucks will stay on the other side of BFS during loading using a berm between BFS and the truck.

I think we have a winner here. It makes BFS design changes unnecessary, minimizes wiring runs, co-locates PMAD with the point of use, prevents explosions from batteries or the propellant plant or propellant trucks from destroying everything else, and keeps humans away from the entire operation.

Thoughts?

New Mars Forums

Announcement

#276 2018-06-19 19:49:23

Re: Going Solar...the best solution for Mars.

#277 2018-06-20 05:43:32

Re: Going Solar...the best solution for Mars.

#278 2018-06-20 16:35:21

Re: Going Solar...the best solution for Mars.

#279 2018-06-20 17:33:38

Re: Going Solar...the best solution for Mars.

#280 2018-06-20 20:30:32

Re: Going Solar...the best solution for Mars.

#281 2018-06-27 18:25:00

Re: Going Solar...the best solution for Mars.

#282 2018-06-28 05:29:04

Re: Going Solar...the best solution for Mars.

#283 2018-06-28 07:17:22

Re: Going Solar...the best solution for Mars.

#284 2018-06-28 11:31:43

Re: Going Solar...the best solution for Mars.

#285 2018-06-28 17:04:53

Re: Going Solar...the best solution for Mars.

#286 2018-06-29 04:17:27

Re: Going Solar...the best solution for Mars.

#287 2018-06-29 05:24:58

Re: Going Solar...the best solution for Mars.

#288 2018-06-29 10:28:31

Re: Going Solar...the best solution for Mars.

#289 2018-06-29 15:07:46

Re: Going Solar...the best solution for Mars.

#290 2018-06-29 16:45:10

Re: Going Solar...the best solution for Mars.

#291 2018-06-29 16:52:27

Re: Going Solar...the best solution for Mars.

#292 2018-06-29 17:23:44

Re: Going Solar...the best solution for Mars.

#293 2018-06-29 17:53:27

Re: Going Solar...the best solution for Mars.

#294 2018-06-29 20:32:59

Re: Going Solar...the best solution for Mars.

#295 2018-06-30 04:54:25

Re: Going Solar...the best solution for Mars.

#296 2018-06-30 07:58:21

Re: Going Solar...the best solution for Mars.

#297 2018-06-30 08:48:14

Re: Going Solar...the best solution for Mars.

#298 2018-06-30 11:01:56

Re: Going Solar...the best solution for Mars.

#299 2018-06-30 12:09:10

Re: Going Solar...the best solution for Mars.

#300 2018-06-30 12:42:43

Re: Going Solar...the best solution for Mars.

Board footer