New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: We've recently made changes to our user database and have removed inactive and spam users. If you can not login, please re-register.

#101 2017-06-13 10:14:30

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 2,506
Website

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

I'm with Oldfart1939.  This set of threads has completely wrapped around the axle in irrelevant details and ideological arguments. 

I've said before:  you need both nuclear and solar.  The nuclear is sized by the base load at night and in reduced-insolation dust storm conditions.  The rest can be solar.  Whether you want more nuclear than that minimum is what the spreadsheet tradeoff is for.  It really is that simple.  And we amateurs do not have all the data to do that trade accurately. 

There is also incredible blurring of the difference between an exploration mission and a colonization mission.  I quite understand the desire to do everything at once,  but the school of hard knocks teaches a very bitter lesson:  do not bite off more than yo can chew.  Yet that does not proscribe biting off all that you can chew.

That first surface exploration needs to bring everything needed to survive,  explore,  and return.  It also needs to bring everything we can imagine for ISR,  for trials at small scale.  You simply cannot ethically bet their lives on experimental stuff during that first trip.  They set all these things up and run them.  Those that actually work get left running on automatic,  for the next crew.  That way you know FOR SURE what works well and what does not work,  at the selected site! 

It's the second crew that brings the selection of ISRU gear that works,  but in full scale.  They set up the initially-small base that could be permanently manned.  THAT is the kernel from which the colony eventually grows.  Going there is too expensive to experiment with unproven stuff at large scale.  Period.  Lab benchtop successes are NOT proven field equipment.  Period. 

There is NO other sure way to do that process without risking death of that first crew to a bad management decision.  Do THAT again,  and you kill colonization for at least a century.  Learn the lessons of Apollo 1,  Apollo 13,  shuttle Challenger,  shuttle Columbia,  Vladimir Komarov,  and the Salyut-1 crew. 

Harsh,  but simple,  and easily understood. 

GW

Last edited by GW Johnson (2017-06-13 10:15:56)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#102 2017-06-13 11:31:24

kbd512
Member
Registered: 2015-01-02
Posts: 1,056

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

Louis,

I'll try to answer your questions as best I can.

1. PV Panel Electrical Power Output:

UltraFlex is 150We/kg to 175We/kg at 1AU, in Earth orbit, where the flux from the Sun is 1,370W/m^2 (actual flight hardware)

MegaFlex is 250We/kg at 1AU, in Earth orbit, where the flux from the Sun is 1,370W/m^2 (in an advanced development state)

EDIT: That means that for every kilogram of PV panel array (does not include PMAD), the output is 250We at 1AU where the flux is 1,370W/m^2 when there's absolutely nothing in front of the panel but empty space and the panel is pointed directly at the Sun.

The inverse square law applies to solar irradiance (power received from the Sun, per unit of area).  Mercury is just 2/3 closer to the Sun than Earth is, but receives 9 times as much solar flux per square meter (m^2).  This is why PV panels for missions to Jupiter get huge.  Strictly speaking, the multiplier for Mars is 2.3, but to account for irradiance variances, the multiplier is roughly 2.74.

The peak or maximum solar irradiance received on the surface of Mars ranges from 493W/m^2 (aphelion) to 718W/m^2 (perihelion).  That figure is a total flux that includes direct beam power (direct sunlight) and indirect or diffuse (sunlight scattered by the atmosphere and dust in the atmosphere) solar insolation (amount of power from the Sun, incident on the surface of Mars).  Dependent upon the time of day, latitude, and surface weather conditions (dust storms), received power can be substantially less.

2. Power Transmission

In simple terms, if you run 2 electrical cords with different voltages through the same gauge wire, the system that runs at the higher voltage will transmit the power more efficiently and losses from resistance in the wire itself will be lower.  1 Volt is the electrical pressure required to push 1 Amp of current through a resistance of 1 Ohm.  The power loss is manifested as a voltage drop at the other end of the wire.

Example (2 wires, same gauge or diameter and same length, therefore both wires have the same internal resistance to the flow of current):

Electrical Power:

P = Power, in Watts; I = Current, in Amps; V = Voltage, in Volts

P = I * V or simply put, Watts = Amps * Volts

Electrical Power Loss:

E = Voltage Loss, in Volts; I = Current, in Amperes; R = Resistance, in Ohms

E = I * R or simply put, Voltage Loss = Amps * Resistance

Let's say both wires are 1000 feet of 4 gauge wire and internal resistance is .25.

Wire #1 transmits power at 120V and 5A (120V * 5A = 600We)

E = 5 * .25 * 1 (1 represents 1000 feet of wire, 2 would represent 2000 feet of wire, etc) * # of wires (generally 2 wires, but this is just an example so the calculations to show power loss below are based on 1 wire)

E = 5 * .25, E = 1.25 Volts

Power Lost in transmission = 120V - 1.25V = 118.75

118.75 * 5 = 593.75We actually transmitted to the receiving end 1000 feet away

Wire #2 transmits power at 240V and 2.5A (240V * 2.5A = 600We)

E = 2.5 * .25 = .625; 240V - .625V = 239.375V

239.375V * 2.5A = 598.4375We actually transmitted to the receiving end 1000 feet away

The R value is the same in both wires because both wires or electrical conductors have the same physical dimensions.  This is Ohm's Law in action.  Both wires transmit the exact same amount of power on the sending end, but to minimize power loss on the receiving end, then you want to minimize flow to the extent practical.  Increasing the physical dimensions of the conductor reduces resistance, but increases mass.  It's a balancing act.  How far do I need to transmit the power (less distance is better), how much conductor mass do I want (less is better, but means increased resistance), and what voltages will my equipment use (because there are also losses in power conversion and added mass for power transformation, by stepping up/down voltage using transformers).

A 4 gauge wire is huge and heavy, therefore it has very low (.25 Ohm per 1000 feet) resistance.  Resistance in higher gauges of wire are substantially higher, but the wires are substantially smaller and therefore lighter.  That's why the 200m power cable for the 10kWe fission reactor weighs 415kg.  Ampacity, which is just portmanteau for ampere capacity, is the ability of a wire to conduct a given flow of Amperes of current without destruction, and is a topic for another post.  The homopolar generators I work on in my free time run into ampacity or current carrying limitations that dictate the mass of the copper conductor used in the rotor assembly because voltage is really low and current is insanely high.

In practice, higher voltages are used to reduce wire gauge and therefore mass and cost.

3. Using Lighter Materials

Recall that all components have to survive launch from Earth and reentry at Mars and then must provide many years of reliable service.  Trying to design the absolute lightest system possible can be, and frequently is, counterproductive.

Last edited by kbd512 (2017-06-13 11:34:59)

Offline

#103 2017-06-14 06:05:59

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

That's an opinion rather than a fact GW...in my view solar plus methane/batteries, nuclear alone and nuclear plus solar can all deliver the required energy for Mission One.  This is a discussion about what is the best solution - and that must focus on (a) mass (b) failsafe qualities and (c) flexibility to meet Mission requirements (e.g. science experiments, ISRU experimentation and exploration). 

Mass should be a fairly objective comparator, but it does relate to (c) as well.  Failsafeness is a matter of subjective judgement to some degree, involving an assessment of risk factors and risk data. But (c) critically depends on your conception of the mission - is it a timid "land and be bland" concept with an EVA in imitation of Apollo or is it a "new civilisation" landing, beginning a permanent settlement that will rapidly become self-sufficient. Of course I favour the latter.

GW Johnson wrote:

I'm with Oldfart1939.  This set of threads has completely wrapped around the axle in irrelevant details and ideological arguments. 

I've said before:  you need both nuclear and solar.  The nuclear is sized by the base load at night and in reduced-insolation dust storm conditions.  The rest can be solar.  Whether you want more nuclear than that minimum is what the spreadsheet tradeoff is for.  It really is that simple.  And we amateurs do not have all the data to do that trade accurately. 

There is also incredible blurring of the difference between an exploration mission and a colonization mission.  I quite understand the desire to do everything at once,  but the school of hard knocks teaches a very bitter lesson:  do not bite off more than yo can chew.  Yet that does not proscribe biting off all that you can chew.

That first surface exploration needs to bring everything needed to survive,  explore,  and return.  It also needs to bring everything we can imagine for ISR,  for trials at small scale.  You simply cannot ethically bet their lives on experimental stuff during that first trip.  They set all these things up and run them.  Those that actually work get left running on automatic,  for the next crew.  That way you know FOR SURE what works well and what does not work,  at the selected site! 

It's the second crew that brings the selection of ISRU gear that works,  but in full scale.  They set up the initially-small base that could be permanently manned.  THAT is the kernel from which the colony eventually grows.  Going there is too expensive to experiment with unproven stuff at large scale.  Period.  Lab benchtop successes are NOT proven field equipment.  Period. 

There is NO other sure way to do that process without risking death of that first crew to a bad management decision.  Do THAT again,  and you kill colonization for at least a century.  Learn the lessons of Apollo 1,  Apollo 13,  shuttle Challenger,  shuttle Columbia,  Vladimir Komarov,  and the Salyut-1 crew. 

Harsh,  but simple,  and easily understood. 

GW


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#104 2017-06-14 06:27:22

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

Thanks kbd, I may not make a very good pupil when it comes to electrical wiring but I appreciate the tuition! 

I am still puzzled as to why a system described as "ultralight" has a mass of over 2 kgs per square metre (I base this on the only data I can find which allows you to work that out from the diameter of the two arrays, linked to below):

https://2.bp.blogspot.com/-VFpo6AoMFFI/ … gaflex.png

Over 2 kgs per square metre is not what I would call ultralight - something less than 500 grams per square metre probably deserves that accolade. 



kbd512 wrote:

Louis,

I'll try to answer your questions as best I can.

1. PV Panel Electrical Power Output:

UltraFlex is 150We/kg to 175We/kg at 1AU, in Earth orbit, where the flux from the Sun is 1,370W/m^2 (actual flight hardware)

MegaFlex is 250We/kg at 1AU, in Earth orbit, where the flux from the Sun is 1,370W/m^2 (in an advanced development state)

EDIT: That means that for every kilogram of PV panel array (does not include PMAD), the output is 250We at 1AU where the flux is 1,370W/m^2 when there's absolutely nothing in front of the panel but empty space and the panel is pointed directly at the Sun.

The inverse square law applies to solar irradiance (power received from the Sun, per unit of area).  Mercury is just 2/3 closer to the Sun than Earth is, but receives 9 times as much solar flux per square meter (m^2).  This is why PV panels for missions to Jupiter get huge.  Strictly speaking, the multiplier for Mars is 2.3, but to account for irradiance variances, the multiplier is roughly 2.74.

The peak or maximum solar irradiance received on the surface of Mars ranges from 493W/m^2 (aphelion) to 718W/m^2 (perihelion).  That figure is a total flux that includes direct beam power (direct sunlight) and indirect or diffuse (sunlight scattered by the atmosphere and dust in the atmosphere) solar insolation (amount of power from the Sun, incident on the surface of Mars).  Dependent upon the time of day, latitude, and surface weather conditions (dust storms), received power can be substantially less.

2. Power Transmission

In simple terms, if you run 2 electrical cords with different voltages through the same gauge wire, the system that runs at the higher voltage will transmit the power more efficiently and losses from resistance in the wire itself will be lower.  1 Volt is the electrical pressure required to push 1 Amp of current through a resistance of 1 Ohm.  The power loss is manifested as a voltage drop at the other end of the wire.

Example (2 wires, same gauge or diameter and same length, therefore both wires have the same internal resistance to the flow of current):

Electrical Power:

P = Power, in Watts; I = Current, in Amps; V = Voltage, in Volts

P = I * V or simply put, Watts = Amps * Volts

Electrical Power Loss:

E = Voltage Loss, in Volts; I = Current, in Amperes; R = Resistance, in Ohms

E = I * R or simply put, Voltage Loss = Amps * Resistance

Let's say both wires are 1000 feet of 4 gauge wire and internal resistance is .25.

Wire #1 transmits power at 120V and 5A (120V * 5A = 600We)

E = 5 * .25 * 1 (1 represents 1000 feet of wire, 2 would represent 2000 feet of wire, etc) * # of wires (generally 2 wires, but this is just an example so the calculations to show power loss below are based on 1 wire)

E = 5 * .25, E = 1.25 Volts

Power Lost in transmission = 120V - 1.25V = 118.75

118.75 * 5 = 593.75We actually transmitted to the receiving end 1000 feet away

Wire #2 transmits power at 240V and 2.5A (240V * 2.5A = 600We)

E = 2.5 * .25 = .625; 240V - .625V = 239.375V

239.375V * 2.5A = 598.4375We actually transmitted to the receiving end 1000 feet away

The R value is the same in both wires because both wires or electrical conductors have the same physical dimensions.  This is Ohm's Law in action.  Both wires transmit the exact same amount of power on the sending end, but to minimize power loss on the receiving end, then you want to minimize flow to the extent practical.  Increasing the physical dimensions of the conductor reduces resistance, but increases mass.  It's a balancing act.  How far do I need to transmit the power (less distance is better), how much conductor mass do I want (less is better, but means increased resistance), and what voltages will my equipment use (because there are also losses in power conversion and added mass for power transformation, by stepping up/down voltage using transformers).

A 4 gauge wire is huge and heavy, therefore it has very low (.25 Ohm per 1000 feet) resistance.  Resistance in higher gauges of wire are substantially higher, but the wires are substantially smaller and therefore lighter.  That's why the 200m power cable for the 10kWe fission reactor weighs 415kg.  Ampacity, which is just portmanteau for ampere capacity, is the ability of a wire to conduct a given flow of Amperes of current without destruction, and is a topic for another post.  The homopolar generators I work on in my free time run into ampacity or current carrying limitations that dictate the mass of the copper conductor used in the rotor assembly because voltage is really low and current is insanely high.

In practice, higher voltages are used to reduce wire gauge and therefore mass and cost.

3. Using Lighter Materials

Recall that all components have to survive launch from Earth and reentry at Mars and then must provide many years of reliable service.  Trying to design the absolute lightest system possible can be, and frequently is, counterproductive.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#105 2017-06-14 06:42:00

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

Can I ask what you mean by "time-average power".  Do you mean while the solar panel is operational - producing power during the hours of light - or do you mean over the whole period of one sol i.e. around 24.6 hours? If it's the former, I think your figure is too low.


Antius wrote:

For ultraflex / megaflex, specific power is listed as 150W/kg at 1AU, according to this JPL link.

http://www.lpi.usra.edu/opag/meetings/a … uchamp.pdf.

At Mars, sunlight intensity is 0.43x what it is at 1AU.  If atmospheric transmittance is 0.7, and time averaged powr is (root-2)/4 times full sun intensity.  That gives a time-average power of 16W/kg.

I am assuming that the goal is to provide 24/7 power, as this is needed for life support and is highly desirable for all functions.  This requires that somewhere between 67-75% of power consumed is stored, as the sun is only above the horizon 50% of the time and solar irradiation will follow a sine function of intensity during daytime hours.  Lets be generous and assume only 67% of power needs to be stored.  If storage efficiency is 33%, then 14,675kg of cells are needed to supply a constant power of 100KWe.

The energy density of hydrogen-oxygen storage system is taken to be 250Wh/kg.  Some 1800KWh must be stored.  So storage system mass is 7200kg.  Total system mass is therefore 21,875kg.  That's a mass power density of 4.57W/kg.  That is a little less than one quarter of the mass power density of the SP-100 with stirling power conversion.  In this configuration, SP-100 is a less than optimal system as it must operate at part power.  Perhaps Louis would like to check my calculations?

On the subject of SP-100: SP-100 was cancelled largely because there was no foreseeable need for it in the late 90s, as NASA had no realistic humans to Mars or moon programme.  The Clinton administration were also keen to exterminate all of the US advanced nuclear projects for political reasons.  The integral fast reactor programme was eliminated by the same people.  It was close to commercialisation at that point.

If we needed such a reactor, the programme could presumably pick up where it was left off.  How much it would cost to develop is a subject of some debate.  That said, SP-100 was a thing of the 80s and 90s.  We could probably improve upon it today, as there have been some advancements since then.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#106 2017-06-14 08:44:18

Antius
Member
From: UK
Registered: 2007-05-22
Posts: 860

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

Hello Louis, I mean the later.  In my calculations I have assumed that any power system deployed on Mars will need to produce energy around the clock.  So if a solar panel is producing XkWh per day, then time averaged power is (X/24) kW.

Last edited by Antius (2017-06-14 08:44:56)

Offline

#107 2017-06-14 11:21:30

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 10,012

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

Another way of putting it is daily household energy use: How much electricity does an American home use?

Which brings you to what are you powering and when: Estimating Appliance and Home Electronic Energy Use

Which sort of then leads to how to cutback the amount you are using: Electric Usage Chart Tool

Offline

#108 2017-06-14 14:28:19

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

So if 250 W as opposed to 150 W is achieved with Megaflex (there are plenty of references to 250 W), then the 16W should become about 26.6 W.  For 3 tonnes of panels, that would give you about 1955 KWehs per sol as opposed to 2460 KWehs for a 100 Kwe nuclear reactor. Of course if the W/Kg figures include additional equipment, then my allowance of 4 tonnes  for panels plus equipment might be just enough - shame we can't get more detailed info on the Megaflx.

Anyway, on the evidence so far, it seems that Megaflex would be close to providing a solar energy solution in line with my proposal but not quite there.

Here's an alternative...The SLASR project seemed to be quite advanced.


http://citeseerx.ist.psu.edu/viewdoc/do … 1&type=pdf

It's UV protected and they were claiming 362 W/g.  If that were achieved then with 3 tonnes on Mars you would be producing something like 2830 KWehs per sol - in other words substantially more than the 100 Kw nuclear reactor.

I don't feel like this is an insoluble problem, just one that hasn't had a lot of resources thrown at it because there have been other priorities.






Antius wrote:

Hello Louis, I mean the later.  In my calculations I have assumed that any power system deployed on Mars will need to produce energy around the clock.  So if a solar panel is producing XkWh per day, then time averaged power is (X/24) kW.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#109 2017-06-17 20:25:21

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 10,012

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

Just thinking of how this https://www.nytimes.com/2017/01/30/busi … .html?_r=2 might be of use on mars.

Multiple article

396 refrigerator-size stacks of Tesla batteries, encased in white metal, capable of powering roughly 15,000 homes over four hours, is part of an emergency response to projected energy shortages stemming from a huge leak at a natural gas storage facility.

So far in Australia, Tesla has delivered Powerpack installations of 190kWh at Dream Factory in Footscray, Melbourne, and 95kWh at a school in Rockhampton, Queensland. 

The first installation of a 250 kilowatt, 500KW/h Powerpack will be at the City of Sydney's Alexandra Canal Works depot in the coming months. Transgrid awarded a contract to Tesla to supply Powerpacks to several sites last year, and plans to use the installation to trial the use of batteries in demand management.

A megawatt Powerpack installation, enough to run 750 homes for 4 hours, costs about $1.8 million.

2,000-kilowatt-hour battery enough to power about 375 homes for four hours.

The resort generates electricity via a 1-megawatt solar array powered by 20 Tesla Powerpacks.

Tesla installed 54,978 solar panels and 272 Powerpack batteries to power the island. The solar array has 13 megawatts of solar generation capacity.

This is an AC storage device but would still work for later.

https://www.tesla.com/powerpack

Overall System Specs

    AC Voltage     380 to 480V, 3 phases
    Energy Capacity     210 kWh (AC) per Powerpack
    Scalable Inverter Power from 50kVA to 625kVA (at 480V)

    Powerpack
    Length: 1,308 mm (51.5")
    Width: 822 mm (32.4")
    Height: 2,185 mm (86")
    Weight: 1622 kg (3575 lbs)

    Industrial Inverter
    Length: 1,014 mm (39.9")
    Width: 1254 mm (49.4")
    Height: 2192 mm (86.3")
    Weight: 1200 kg (2650 lbs)


https://www.tesla.com/powerwall

Offline

#110 2017-06-19 04:25:24

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

SpaceNut,

Yes I think Tesla approach is very relevant to Mars.  This is probably the nearest we have to what a system might look like on Mars:

https://www.youtube.com/watch?v=VZjEvwrDXn0

This system serves 600 people on the island.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#111 2017-06-19 05:51:13

kbd512
Member
Registered: 2015-01-02
Posts: 1,056

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

To give everyone an idea of how much of a weight difference there is between a Tesla PowerWall and an ORU, the PowerWall weighs 264lbs and has a 13.5kWh usable capacity.  Each ORU weighs 430lbs, or 518lbs with the heater plate, and have a capacity of around 14.8kWh.  None of these Tesla PowerWall or PowerPack batteries will ever be subjected to the kind of gravitational and vibrational loads that a space launch and reentry will produce, nor subjected to frigid Martian nights, so it's not a very good reference point.

Offline

#112 2017-06-19 11:04:37

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

There is no reason why the batteries can't be built on Mars. As for Martian nights, why would you have the batteries outside?  I presume they would be in a specially designed hab.


kbd512 wrote:

To give everyone an idea of how much of a weight difference there is between a Tesla PowerWall and an ORU, the PowerWall weighs 264lbs and has a 13.5kWh usable capacity.  Each ORU weighs 430lbs, or 518lbs with the heater plate, and have a capacity of around 14.8kWh.  None of these Tesla PowerWall or PowerPack batteries will ever be subjected to the kind of gravitational and vibrational loads that a space launch and reentry will produce, nor subjected to frigid Martian nights, so it's not a very good reference point.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#113 2017-06-19 18:14:27

Antius
Member
From: UK
Registered: 2007-05-22
Posts: 860

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

louis wrote:

There is no reason why the batteries can't be built on Mars. As for Martian nights, why would you have the batteries outside?  I presume they would be in a specially designed hab.


kbd512 wrote:

To give everyone an idea of how much of a weight difference there is between a Tesla PowerWall and an ORU, the PowerWall weighs 264lbs and has a 13.5kWh usable capacity.  Each ORU weighs 430lbs, or 518lbs with the heater plate, and have a capacity of around 14.8kWh.  None of these Tesla PowerWall or PowerPack batteries will ever be subjected to the kind of gravitational and vibrational loads that a space launch and reentry will produce, nor subjected to frigid Martian nights, so it's not a very good reference point.

If you are talking about using Mars built batteries to store energy from Mars built PV, then I would suggest that this is problematic and should be kept to a minimum.  The problem is Mars built PV would have long energy payback times before the embedded energy of the battery systems and storage losses are taken into account.  When those things are included, the balance could begin to go negative, I.e. you get less out than you put in - you do not recoup your energy investment before the lifetime of the systems is reached.

There are a lot of things that have to have reliable 24/7 power.  A lot of high temperature processes like aluminium or silicon manufacture would find it very difficult to cope with intermittent power because if feedstock solidifies in crucibles and electrolysis cells, it does a lot of damage.  In those cases, you need power around the clock and there is no escape from that.

In some cases 24/7 power is desirable but not essential.  Examples might be machine shops and computer terminals.  Running these things for 6 hours per day would be an inefficient use of expensive assets, but you will not damage them by using them in this way.  You could live like that if there were no choice.  It would mean accepting lower rates of return on capital equipment and lower industrial growth rates, but in principle it could be done.  Likewise with human living.  Some high energy loads such as washing clothes, heating water, cooking food, etc, might be programmed to switch on when power is available.  It is less efficient in some ways, but could be made to work.

There are some instances where energy end use can be genuinely flexible with only a small penalty.  Pumping water for example.  We might pump water into header tanks for a few hours a day, and it might not matter so much if power is not available continuously, as we can store a days worth of water in a tower.  Because it is easy to store heat in cheap energy dense materials, any end uses that require hot and cold can work on intermittent energy by adding thermal capacitance.  As always there are costs involved in doing this, but it can be made to work.

To reduce energy payback times on a PV system on Mars, it is important to use the power when it is available, in applications where this is at all possible.  That way, you minimise the need for energy expensive energy storage.  Also, it would make sense to try and match the voltage output of the panels to the devices that consume power.  That way you minimise energy losses due to power conversion.  Keep transmission distances short and try and run as much as you can on 12 or 24 volts DC.  For things like lighting and computing that is easy.  For high power applications, the current starts getting scary, you end up needing thick conductors (more invested energy) and local resistance generates a lot of heat, potentially causing fires.  But people have made this sort of solution work in the past and low voltage DC networks are not that uncommon.  The key thing is to keep transmission distances short and to size conductors for the intended current.  So basically, heavy loads need to be no more than 100 feet from the panels.

I designed a man cave outhouse to run entirely on 12v DC.  I got around the transmission problem by using the RSJs in the building structure to conduct the power.  These had such high cross-section area that internal resistance was small even at very high current levels.  It needs to be because a 1.2KW load draws 100 amps!  Because voltage is so low, a thin layer of paint and ordinary masonry has enough resistance to insulate the rsj against lea j age.  It should work, but it will be some time before I can build the thing and test it.

There are no free lunches really.  If we try and use power without storage, the EROI of the solar power system may improve.  Unfortunately, the rate of return on other capital equipment goes down because you can only run it for perhaps a quarter of each day.  However, the wear and tear on equipment is usually linear to operating hours.  Although rate of return would be lower, total return should be the same over a longer time.  You just have to wait longer getting things done and people would need several jobs.  They do high energy tasks when it is available and low energy tasks when it is not.  The same with recreation.

Last edited by Antius (2017-06-19 19:04:44)

Offline

#114 2017-06-19 19:06:15

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

EROI is a totem to dance round rather than a serious analytical tool...which is why nuclear with its great EROI ends up being one of the most expensive energy options on Earth.

Your obvious EROI error on this occasion is to assume that the productive capability of the Mars population will be the same as the average Earth population. What you fail to understand is that EROI is a relative concept in reality, not an absolute one and the reason is that the most important constraint on energy production is labour input, not energy input. Think about it this way...In a primitive society, assuming you could explain the processes involved to its inhabitants, using solar panel energy would be a negative.  They would be using all their labour to try and build solar panel manufacturing plants in the first place. They would have to use labour intensive methods to do things like purify silicon and so on. Before they could build their first solar panel, they would run out of labour time, because they were still having to tend the fields and look after their crops. Mars ain't gonna be like that. It is going to hi-tech settlement from Sol One onwards. There will be high rates of automation for all processes.  The amount of labour time required to produce solar panels will be minimal, because the settlers will have access to automated machines that purify silicon, cut silicon wafers, and encapsulate the cells.

Forget EROI. The only real guide we have is price (which in broad terms reflects labour input). You could argue ad infinitum about the energy embedded within a battery through manufacture but price is known. All price  suggests is that solar plus battery is currently an expensive way to generate electricity, but sometimes less expensive than some other alternatives such as diesel on isolated islands. The only issue is whether you can afford it. Solar plus battery in the right area probably comes in around 20 cents per KwH. Expensive but in no way "negative" and there is a definitive payback point after which you are getting your electricity for "free" (bar annual maintenance). Since it's not negative, the really important thing to look at is the % of average income.  The wealthier the individual, the smaller a proportion of income is claimed by the energy cost.

The situation on Mars will be that individuals are on average incredibly productive. This will be because they will have been provided with a range of automated machines: robot rovers, 3D printers, CNC machines, industrial robots, power drills and so on that will boost their labour productivity well beyond average levels on Earth.  They will then be able to reproduce these machines on Mars and so maintain high productivity levels.  The cost of solar and battery production in terms of labour input will be well within the scope of their output. And remember all resources on Mars are effectively free. There are no rents, taxes or licence fees to pay. 

The Tesla solution does deliver 24/7 power so I am not sure what your comments about 24/7 are intended to convey. On Mars, it can be made even more failsafe by use of methane storage.

For Mars's development, the key issues is how quickly we can expand Mars ISRU energy generation. With the right equipment, I believe the community will have a huge energy surplus over and above basic needs, that can be used to cover the basic needs of the expanding settlement (the next wave of settlers as they arrive) and power general industrial expansion.


Antius wrote:
louis wrote:

There is no reason why the batteries can't be built on Mars. As for Martian nights, why would you have the batteries outside?  I presume they would be in a specially designed hab.


kbd512 wrote:

To give everyone an idea of how much of a weight difference there is between a Tesla PowerWall and an ORU, the PowerWall weighs 264lbs and has a 13.5kWh usable capacity.  Each ORU weighs 430lbs, or 518lbs with the heater plate, and have a capacity of around 14.8kWh.  None of these Tesla PowerWall or PowerPack batteries will ever be subjected to the kind of gravitational and vibrational loads that a space launch and reentry will produce, nor subjected to frigid Martian nights, so it's not a very good reference point.

If you are talking about using Mars built batteries to store energy from Mars built PV, then I would suggest that this is problematic.  The problem is Mars built PV would have long energy payback times before the embedded energy of the battery systems and storage losses are taken into account.  When those things are included, the balance could begin to go negative, I.e. you get less out than you put in - you do not recoup your energy investment before the lifetime of the systems is reached.

There are a lot of things that have to have reliable 24/7 power.  A lot of high temperature processes like aluminium or silicon manufacture would find it very difficult to cope with intermittent power because if feedstock solidifies in crucibles and electrolysis cells, it does a lot of damage.  In those cases, you need power around the clock and there is no escape from that.

In some cases 24/7 power is desirable but not essential.  Examples might be machine shops and computer terminals.  Running these things for 6 hours per day would be an inefficient use of expensive assets, but you will not damage them by using them in this way.

There are some instances where energy end use can be genuinely flexible with only a small penalty.  Pumping water for example.  We might pump water into header tanks for a few hours a day, and it might not matter so much if power is not available continuously, as we can store a days worth of water in a tower.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#115 2017-06-19 20:04:16

kbd512
Member
Registered: 2015-01-02
Posts: 1,056

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

louis wrote:

EROI is a totem to dance round rather than a serious analytical tool...which is why nuclear with its great EROI ends up being one of the most expensive energy options on Earth.

Stop throwing out your personal beliefs and start throwing out some numbers.

Table 8.4. Average Power Plant Operating Expenses for Major U.S. Investor-Owned Electric Utilities, 2005 through 2015 (Mills per Kilowatthour)

Offline

#116 2017-06-20 03:06:47

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

Operating costs are not whole life costs. You have to build your nuclear power station first and that requires a lot more expense than a gas turbine. I note the table does not show the operating costs of solar energy, which will be very minimal. Nearly all the cost of a solar plant is in the construction and deployment.

I was objecting to the unsubstantiated claim that solar energy could ever have a negative EROI on Mars. Any EROI for nuclear on Mars must include the large energy expenditure on getting the nuclear plant from Earth to Mars.

kbd512 wrote:
louis wrote:

EROI is a totem to dance round rather than a serious analytical tool...which is why nuclear with its great EROI ends up being one of the most expensive energy options on Earth.

Stop throwing out your personal beliefs and start throwing out some numbers.

Table 8.4. Average Power Plant Operating Expenses for Major U.S. Investor-Owned Electric Utilities, 2005 through 2015 (Mills per Kilowatthour)


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#117 2017-06-20 07:14:06

Antius
Member
From: UK
Registered: 2007-05-22
Posts: 860

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

Louis is dodging the facts again, hoping he can 'argue' solar into a better position…ha ha ha!  Maybe god will smile on his efforts here and change the laws of physics to make it so :-)  Life has an unkind way of stamping all over pet ideologies.

The EROI of an energy system on Mars would be less than 1, i.e. negative energy balance, if the energy produced by the plant over its lifetime, after losses in transmission and storage, is less than the energy invested in creating and maintaining it.  In reality, if EROI is less than about 3, an energy source cannot be economically viable because of losses in end use and the need to reinvest energy to maintain the energy system.  There is nothing insubstantial or theoretical about it, it really can and does happen and it is well reflected in poor economic performance of some energy sources.  It is why corn ethanol will never supplant petroleum without subsidies.

Energy economics is a fairly good proxy for determining the real economic performance of an energy source.  But EROI on its own is not the whole story.  Just as important are ‘energy payback time’ and ‘energy rate of return’.  Some energy sources can do relatively badly on EROI (within limits), but will still float economically if ‘energy rate of return’ is good.  Natural gas projects are a good example of this, as build times can be very short.  Even though fractured shale wells have monstrously high depletion rates and poor EROI, they can be profitable, because they deliver huge energy return during the first year.  This can be where big nuclear projects fall down, because in the present regulatory climate it can be 10 years or more between first work on a project and electricity reaching the busbars.  EROI can be excellent over the life of the plant, but rate of return could be mediocre over the investment timeframe of 20 years, because the first 10 years produce nothing.  The French have had a successful nuclear programme largely because build times were kept to within 5 years, as they focused on developing a common design, often with multiple units on a single site, which benefited from a learning curve and regulators were happy to do their jobs without halting the project.

Reducing build times is why most countries in the know are now developing smaller modular reactors that can be built in factories and assembled in weeks or months.  It is no accident that some of the first reactors to be built in the western world were also relatively cheap.  Of course on Mars, reactors will be imported at first, will be very compact and modular and will be operating within days of delivery.

In a reusable transport system, the energy cost of delivery is going to be small beer, because of the overwhelming energy density of nuclear fuel.  If a multi-megawatt reactor core provides 200W/kg and it costs 100MJ/Kg to push it to Earth escape and TMI, it will repay that delivery cost in a little less than six days.  If the real energy cost is ten times greater, the energy delivery cost is repaid in about 8 weeks.  Compare that to a core life that could be 5-30 years, depending on design.

Remember that there is nothing ‘green’, ‘friendly’, ‘pure’ or ‘morally good’ about any energy source that man has ever developed.  They all rape the natural world in one way or another and through their action, allow man to harness nature’s capital for his needs.  Some are worse than others, but there is nothing inherently good about any of them.  In fact ultimately, the only green thing any human being can do is die.  Isn't that a depressing thought.

Last edited by Antius (2017-06-20 07:25:00)

Offline

#118 2017-06-20 08:02:45

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

"In reality, if EROI is less than about 3, an energy source cannot be economically viable because of losses in end use and the need to reinvest energy to maintain the energy system. "   This is completely wrong. The real reason it's not sustainable is because, on Planet Earth, a large number of people have low or no productivity - children, old people, disabled or long term sick people, unemployed and women at home. EROI has to be large in order to generate the energy surplus which is then spread around the non-productive population.

The early Mars colony will be different in two ways.  Firstly there will be no children, no old people, no women engaged exclusively in household work, no long term disabled or sick people,   and no unemployed.  Any energy surplus above and beyond basic needs is available for ploughing back into energy systems.  Secondly, EROI is as I say a relative concept (relative both to labour input and population number). To reduce it to an absurdum, if we had one person producing 1 MW at an EROI of 3, that one person would have put in 333 Kws of power into their energy and got back 1MW, a surplus of 666 KWs of power available to that one person. If a population of 1000 did the same, then per person, each person would only have 0.66 of a Kw of power available to them. See the idea?  The key here is there being a surplus. The point is that the small population on Mars in the early settlement will be generating huge amounts of pp surplus energy available for a wide range of industrial and agricultural applications.

Finally and most  importantly why are you trying to suggest, rather subtly,  an EROI of 3 for solar? The truth is, it is more like 10-15.

http://rameznaam.com/2015/06/04/whats-t … -of-solar/

The tree-hugger nonsense is entirely in your imagination. I have always maintained all energy systems cause environmental damage. It is just a question of how much and what the risk profile is. 




Antius wrote:

Louis is dodging the facts again, hoping he can 'argue' solar into a better position…ha ha ha!  Maybe god will smile on his efforts here and change the laws of physics to make it so :-)  Life has an unkind way of stamping all over pet ideologies.

The EROI of an energy system on Mars would be less than 1, i.e. negative energy balance, if the energy produced by the plant over its lifetime, after losses in transmission and storage, is less than the energy invested in creating and maintaining it.  In reality, if EROI is less than about 3, an energy source cannot be economically viable because of losses in end use and the need to reinvest energy to maintain the energy system.  There is nothing insubstantial or theoretical about it, it really can and does happen and it is well reflected in poor economic performance of some energy sources.  It is why corn ethanol will never supplant petroleum without subsidies.

Energy economics is a fairly good proxy for determining the real economic performance of an energy source.  But EROI on its own is not the whole story.  Just as important are ‘energy payback time’ and ‘energy rate of return’.  Some energy sources can do relatively badly on EROI (within limits), but will still float economically if ‘energy rate of return’ is good.  Natural gas projects are a good example of this, as build times can be very short.  Even though fractured shale wells have monstrously high depletion rates and poor EROI, they can be profitable, because they deliver huge energy return during the first year.  This can be where big nuclear projects fall down, because in the present regulatory climate it can be 10 years or more between first work on a project and electricity reaching the busbars.  EROI can be excellent over the life of the plant, but rate of return could be mediocre over the investment timeframe of 20 years, because the first 10 years produce nothing.  The French have had a successful nuclear programme largely because build times were kept to within 5 years, as they focused on developing a common design, often with multiple units on a single site, which benefited from a learning curve and regulators were happy to do their jobs without halting the project.

Reducing build times is why most countries in the know are now developing smaller modular reactors that can be built in factories and assembled in weeks or months.  It is no accident that some of the first reactors to be built in the western world were also relatively cheap.  Of course on Mars, reactors will be imported at first, will be very compact and modular and will be operating within days of delivery.

In a reusable transport system, the energy cost of delivery is going to be small beer, because of the overwhelming energy density of nuclear fuel.  If a multi-megawatt reactor core provides 200W/kg and it costs 100MJ/Kg to push it to Earth escape and TMI, it will repay that delivery cost in a little less than six days.  If the real energy cost is ten times greater, the energy delivery cost is repaid in about 8 weeks.  Compare that to a core life that could be 5-30 years, depending on design.

Remember that there is nothing ‘green’, ‘friendly’, ‘pure’ or ‘morally good’ about any energy source that man has ever developed.  They all rape the natural world in one way or another and through their action, allow man to harness nature’s capital for his needs.  Some are worse than others, but there is nothing inherently good about any of them.  In fact ultimately, the only green thing any human being can do is die.  Isn't that a depressing thought.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#119 2017-06-20 16:43:31

kbd512
Member
Registered: 2015-01-02
Posts: 1,056

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

Antius,

NASA and DOE won't design anything nuclear to have an operational life of less than a decade.  KiloPower's operational design life is a minimum of 15 years.  Core life can be extended by running at less than full rated output.

Louis,

You're arguing your point with someone who thoroughly enjoys working with batteries, solar panels and electric generators, and electronics in general.  I do basic math on what things weigh, what they cost, and have a reasonably good idea of how well things work from past recorded performance or personal experience.  So far, I haven't seen anything that looks any better than a nuclear reactor for providing a tens of kilowatts of continuous power 50% further from the Sun than we are.  PV and batteries are just starting to become truly competitive with small scale fossil fuel applications, in terms of performance, and most are things that are still in labs.

If I even thought we might get PV arrays and batteries to provide actual performance in the same ballpark as a fission reactor in the next decade, I'd take no issue whatsoever with using technologies that are inherently less dangerous than a fission reactor.  Unfortunately, current reality is that no such better system exists.  If someone comes up with a better PV panel or battery, I'll happily concede the point.  We can "what-if" PV panel and battery performance to death, but all I've seen over my entire life has been slow but steady incremental performance improvement of existing basic power technologies.  I have no doubt that one day we'll get comparable performance to nuclear options, up to a certain output level.  How long do you want to wait for that to happen because the cost to ship anything to Mars is literally out of this world and all purported price reductions have yet to occur?  It took 17 years for space power applications photovoltaic cells to go from 20% efficiency to 33% efficiency.  Breakthroughs are always possible, but seldom come to fruition without a staggering amount of effort and capitalization.

Offline

#120 2017-06-21 02:20:37

louis
Member
From: UK
Registered: 2008-03-24
Posts: 2,275

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

We don't require any further improvement in solar panel performance on Mars for them to be viable.  The EROI on Mars is going to be less than on Earth, maybe more like 4-7 than 10-15, but as explained above, unlike on Earth the energy surplus doesn't have to be applied to an unproductive population or a population with low productivity.  It will be applied purely to activities based on high labour productivity thanks to advanced automated technologies being deployed. Furthermore, there is no additiional price burden  on Mars - no land rent, no licence fees, no interaction with regulatory bodies and no grid interface. The fact that we can begin PV panel manufacture at an early stage on Mars is for me the clincher. I would judge that we could begin PV panel manufacture as early as 6 years into settlement, say Mission 3.

kbd512 wrote:

Antius,

NASA and DOE won't design anything nuclear to have an operational life of less than a decade.  KiloPower's operational design life is a minimum of 15 years.  Core life can be extended by running at less than full rated output.

Louis,

You're arguing your point with someone who thoroughly enjoys working with batteries, solar panels and electric generators, and electronics in general.  I do basic math on what things weigh, what they cost, and have a reasonably good idea of how well things work from past recorded performance or personal experience.  So far, I haven't seen anything that looks any better than a nuclear reactor for providing a tens of kilowatts of continuous power 50% further from the Sun than we are.  PV and batteries are just starting to become truly competitive with small scale fossil fuel applications, in terms of performance, and most are things that are still in labs.

If I even thought we might get PV arrays and batteries to provide actual performance in the same ballpark as a fission reactor in the next decade, I'd take no issue whatsoever with using technologies that are inherently less dangerous than a fission reactor.  Unfortunately, current reality is that no such better system exists.  If someone comes up with a better PV panel or battery, I'll happily concede the point.  We can "what-if" PV panel and battery performance to death, but all I've seen over my entire life has been slow but steady incremental performance improvement of existing basic power technologies.  I have no doubt that one day we'll get comparable performance to nuclear options, up to a certain output level.  How long do you want to wait for that to happen because the cost to ship anything to Mars is literally out of this world and all purported price reductions have yet to occur?  It took 17 years for space power applications photovoltaic cells to go from 20% efficiency to 33% efficiency.  Breakthroughs are always possible, but seldom come to fruition without a staggering amount of effort and capitalization.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#121 2017-06-21 11:25:28

kbd512
Member
Registered: 2015-01-02
Posts: 1,056

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

louis wrote:

We don't require any further improvement in solar panel performance on Mars for them to be viable.  The EROI on Mars is going to be less than on Earth, maybe more like 4-7 than 10-15, but as explained above, unlike on Earth the energy surplus doesn't have to be applied to an unproductive population or a population with low productivity.  It will be applied purely to activities based on high labour productivity thanks to advanced automated technologies being deployed. Furthermore, there is no additiional price burden  on Mars - no land rent, no licence fees, no interaction with regulatory bodies and no grid interface. The fact that we can begin PV panel manufacture at an early stage on Mars is for me the clincher. I would judge that we could begin PV panel manufacture as early as 6 years into settlement, say Mission 3.

A few quick points to hand-wave (if no amount of math matters, then surely none of this matters, either, but here it is):

1. Since nobody knows if humans can live on Mars for any substantial length of time and development programs for human space flight systems will precede any actual mission hardware deployment by at least a decade, so either the associated development program may never produce usable mission hardware if we discover in the interim that humans really can't live on Mars permanently because they require 1g or we'll have to wait ten years from whatever point we discover that .38g has no serious health effects.

2. There are no mines or ore refining plants on Mars, so we'd have to ship all materials from Earth, which kinda defeats the purpose of development of these manufacturing plants for Mars until mines and material refinement plants exist.  It's one thing to do limited scale repair of existing equipment, which is what Dook and I argued about endlessly because he was fixated on industrial scale manufacturing, but an industrial scale operation is a different animal entirely.

3. There are no robotic PV panel or battery plants here on Earth, so you're either talking about devoting a good number of people to make PV panels and batteries on Mars or development of a major design automation project that most definitely won't be cheap.  Any sort of automation automatically increases electrical power requirements, too, which further increases construction costs.  It'd be pretty cool to finally make anything in space on an industrial scale, though.

4. The power to run a metals mine or manufacturing plant doesn't exist on Mars and you've selected the technology with the poorest mass-to-output ratio to try to achieve that unless you want to ship all the raw materials from Earth.  Actual output from initial operations will likely be poor, to put it mildly.  About 50% of the PV cells from SolAero are rejected by NASA's QC process from plants where mass, cost, and available labor are not major obstacles to production, a major reason why these highly efficient PV arrays are so expensive.  There have been 150 missions that have a combined output far less than what would be required for a Mars colony and SolAero (formerly EMCORE) has bragged about delivering over a million cells over the course of a couple decades.

5. Given the track record of all the prognostications about what sort of technology we'd have or what we'd be doing ten or twenty years from the present, it seems a little humorous that you think any of this will happen in the span of a few years.  Short of some sort of Manhattan Project to colonize Mars, I'll consider everything to be going great if we just manage to get a dozen people to Mars over the next two decades.

In any event, I wish everyone best of luck with the fantastic future colonies on Mars.  If we can even set up a starter colony on Mars, I'll consider the mission accomplished and really don't care what powers it so long as it is reliable and reasonably affordable.

Offline

#122 2017-06-21 13:38:31

Antius
Member
From: UK
Registered: 2007-05-22
Posts: 860

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

The annual insolation at the Martian equator is 1400kWh/m2.  Thats about the same as southern France or Northern Italy.  Substantially more than the UK which averages about 850.  In fact, England during winter has about rhe same insolation as the moons of Jupiter.  The estimate for Mars doesn't account for dust storms.  I have subsequently revised upward my estimate of atmospheric transmittance to 84%.  But it varies substantially from place to place and season to season.

I have completed an EROI analysis for thin film amorphous silicon cells manufactured and installed at the Martian equator.  It's actually better than I expected.  Without storage, EROI is about 10.  With storage in Li-ion batteries, total EROI works out at 7 over a 25 year life.  For storage in methane-oxygen and backup energy generation with combined cycle gas turbine, it works out at just over 3.  This is largely due to the poor efficiency of energy storage in this way, which is about 18% efficient.  So this is not a good option for storage of excess solar energy unless you really do need a portable liquid fuel.

I will provide more details on workings and references tomorrow if time allows.  For now, here are a few caveats:

1. The EROI analysis applies to the equator.  The further away from the equator the plant is located, the worse the EROI, because annual insolation goes down and the array must be sized to provide sufficient power over winter, which increases its size.

2. I have assumed annual degradation rates of 1% which is typical for thin film in sunny parts of the Earth.  However, the ultraviolet environment on Mars is a lot harsher and temperatures can swing by as much as 100 Celsius in 12 hours.  There is also substantial charged particle background radiation, although the effects of UV will probably be more significant.

3. I have assumed that all modules are fit for purpose, without rejections and that none of the panels require replacement or deep maintenance in 25 years.

4. I have assumed that panels can be made on Mars with the same efficiency, the same quality control and the same embodied energy as here on Earth.

5. I missed out the embodied energy within the sabatier plant and storage tanks in the methane-oxygen scenario.  So actual EROI may be less than calculated, although I suspect embodied energy is dominated by the panels.

My overall impression is that it could be made to work with an efficient Li-ion battery solution, assuming these can also be made on Mars to the same lifetime energy investment, longevity and efficiency as those on Earth.  This is quite important, because the EROI of PV is weak before storage.  The storage solution must have low embodied energy and high efficiency to keep EROI within workable limits.  Likewise, the conclusion depends on the other caveats above working out the right way.

Louis makes the point that high EROI is less important on Mars because colonists will be working age and without dependants.  That is partially true.  What low EROI actually translates into is expensive and less abundant energy, lower labour productivity, higher prices paid for goods - in short, less wealth.  He is correct that that situation is easier to tolerate if you don't have to support a family and if things like invalid and prison populations are small in proportion.  However, it is difficult to see that situation being sustainable for very long.  It is also difficult to see how a weak energy economy is going to be a small matter for a growing population on a harsh planet.  These people need to grow their infrastructure into something that new people would want to move to and they need to scratch out a living in an environment that doesn't provide for free a lot of things that are free on Earth.  No one would want to live like that if it means living in poverty on a desert planet.  For Mars to become the New World that America was in its golden age, it needs high rates of economic growth and better living standards that the ones that people can find on Earth.  It needs to be more than Siberia with a red sky.

It is noteworthy that manufacturing PV on Mars only makes sense if the plant can make at least its own weight in power systems in a reasonable investment window (20 years?).  Otherwise you may as well import your power source from Earth.

Last edited by Antius (2017-06-21 14:50:50)

Offline

#123 2017-06-21 14:48:04

Terraformer
Member
From: Atlantis
Registered: 2007-08-27
Posts: 2,388
Website

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

Why would colonists be manufacturing Li-Ion batteries? We mainly use them on Terra for purposes where a high power-weight ratio is needed, such as vehicles and portable electronics. How would it look if they used NiMH, or Nickel-Iron?


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

Offline

#124 2017-06-21 15:13:32

Antius
Member
From: UK
Registered: 2007-05-22
Posts: 860

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

Terraformer wrote:

Why would colonists be manufacturing Li-Ion batteries? We mainly use them on Terra for purposes where a high power-weight ratio is needed, such as vehicles and portable electronics. How would it look if they used NiMH, or Nickel-Iron?

Possibly.  On Earth deep cycle batteries tend to be lead acid.  They have lower cycle efficiency and lower mass energy density than Li-ion.  But they are obviously more cost-effective none the less.  Not sure how they compare on an embodied energy basis.

Offline

#125 2017-06-21 15:54:55

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 10,012

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

Why do we even care about Energy returned on energy invested since no one is paying anything for its insitu use or creation. Nothing is being returned to the payer of the equipment sent to mars to be able to create the insitu source....
This is the dream of the future mars....
City-on-Mars.jpg

Offline

Board footer

Powered by FluxBB