Louis' Solar Power Strategy

louis · 2017-05-27 18:22:15

Yes, Mars is much harder than the Moon but technology - computers, electronics, life support, battery storage and so on - is anything from 10 to 10,000 times better. We have frightened ourselves with our own shadows I think.

I think that the effective cost of launches is now going to be so low with Space X (thanks to their cost control and innovative technology) that we will have much more leeway with landed tonnages. Technological developments in robotics and other branches mean that we can do much more with pre-landing scenario than simply dump stuff on the surface. We can clear the landing zone of rocks, stone and sand for one thing. We can automatically target the landing. We can get a lot of life support ready.

RobertDyck wrote:

louis wrote:
If you are saying there should be a food-producing farm unit as part of Mission One, I am with you on that. It just helps to define what you mean by that. I'd probably devote no more than 20 sq. metres to that and just focus on salad produce.
I agree with you on an Apollo style landing and leaving the ITV in Mars orbit. I would build in pre-landing of cargo, including food, so you can make the human lander really light in mass.
Not sure we need an unmanned test if we pre-landing supplies, as long as we do some extended testing with humans in Earth/Lunar orbit.
I was a pre-schooler through the Moon race, from the last 2 mission of Mercury through Apollo 11 and beyond. For me Apollo 11 was the summer between grade 1 and 2. Every Apollo mission had something go wrong, every mission except Apollo 17. Even Apollo missions to Skylab and Apollo-Soyuz had something go wrong. We have to be paranoid. As it was, Apollo 13 almost killed crew. Mars is harder than the Moon. A human mission will be the largest spacecraft to enter Mars atmosphere, and an affordable mission has to use aerocapture. That will have to be tested. First with a technology demonstrator, then one full-size unmanned test.
I keep thinking of Mars Direct. My mission plan is a modification of that. It included an inflatable greenhouse the same width as a double-car garage, and twice the length. That's between 80 and 100 square metres. Just for the inflatable transparent greenhouse. When Boris Yeltsin was president of Russia, many in the Mars Society argued to use the launch vehicle Energia. Robert Zubrin himself was the first to propose that in his book, published 1997 (one year before the founding of the Mars Society). Energia had roughly 2/3 lift capacity of Saturn V. Actually, Energia once lifted a 88 tonne satellite to 200km orbit, so more like 75% of Saturn V. Anyway, MD would take 3 launches. I had to make mine fit, so pre-land the MAV, and pre-land an inflatable laboratory with greenhouse and pressurized rover. If we use SLS block 2B, it breaks up differently. If we use Falcon Heavy, different again.
To make the greenhouse light-weight, use two layers of PCTFE film. For shape, hold-down straps secured with tent pegs. And I mean equivalent to pegs for an event tent (equivalent size). Light plastic soil trays, and a shovel. Mars regolith would be processed to form soil.

SpaceNut · 2017-05-28 17:32:07

Hopefully we can get back to solar as to whether we need to have it or not.

Solar with the extreems of costs, low performance or high performance is just one issue then there is the mass for the thin film versus the thick panels that while they are of higher efficiency does not alway make for the best choice as we still need to factorin the rest of the system and the delivery launcher/ lander as well. As its not just about wattage to mass density as we will need to figure in the volume of them as well for delivery to mars.

RobertDyck · 2017-05-28 18:23:46

Notice Mars Direct includes a nuclear reactor on the ERV, with an unmanned rover that drives the reactor away before the reactor is turned on. In order to keep mass practical, the reactor is unshielded. Uranium is safe enough to handle with just plastic gloves until it's put in a reactor. So the reactor will be safe until it's turned on. Then you get fission fragments, which are high level nuclear waste. That's the highly radioactive stuff. Mars Direct would have the reactor parked at the bottom of a crater before turning it on. So an astronaut in a spacesuit cannot walk close enough to the crater to even see the reactor. Line-of-sight means radiation could reach him/her. Must have Mars regolith of the crater wall or rim between the reactor and an astronaut. That also means if something goes wrong, you can't fix the reactor. You can't even get within sight of the reactor, so certainly can't get close enough to work on it. While solar is safe, you can work on it. Mars Direct used solar for the habitat. Solar arrays would be deployed in space for transit, folded-up for Mars atmospheric entry, then astronauts would remove the solar arrays by hand on Mars to deploy them on the surface. And if they get covered in dust, an astronaut with a broom could clean them.

kbd512 · 2017-05-28 22:11:43

There's a place for solar power on the Mars exploration missions, but it's a complementary technology. PV panels work best in space, not on the surface of a planet. The rapidly developing Graphene-based batteries and super capacitors, combined with permanent batteries and homopolar generator technologies will supplant solar, and to a lesser extent nuclear, for prime surface power in the near future. NASA may still elect to use the low-cost, lightweight fission reactors they're developing, but ultimately total system mass, service life, and reliability determine the direction of electrical power generation technologies.

While basic life support and communications technologies continue to become more power-efficient, total power requirements continue to trend upwards as a function of everything else we want to do. We want battery-operated power tools, exoskeletons to assist with rapid cargo transfers, rovers, scouting robots, ice mining, farming, and even propellant plants. All that stuff requires power and lots of it.

As permanent battery technology develops, we'll see power sources integrated with low-consumption applications like personal electronics and life support equipment. Even so, primary power will consist of electric generators connected to more powerful permanent batteries. In this use case, primary power actually functions as a backup power source that is ordinarily allocated to energy-intensive applications such as farming, mining, or manufacturing rocket propellants.

In space, thin-film solar panels can provide primary power with permanent battery backups for life support. The fact that the panels are toast after six months is irrelevant when, in three to six months, our people will be on Mars (outbound from Earth) or Earth (inbound from Mars). The panels should be designed to fry during reentry at either end while still attached to the habitat module using something akin to magsafe power connector attachment points. This sort of solar panel disposal is driven by mass, manufacturing costs, and system complexity. It'll be far less costly to print thin-film panels, use them to provide power for the brief transits, and then discard them upon reentry compared to development of panels that last for many years and can be thermally protected and re-deployed on the surface. That's an unnecessary and costly engineering problem to solve.

The flexible thin-film panels are less sensitive to damage as a function of how they work and their expected service life. The fact that disposable panels can be more easily damaged is irrelevant in light of replacement costs, in comparison to the super-expensive hard panels that Orbital ATK manufactures for space stations and long duration deep space robotic missions. It may seem wasteful, but it's mass-efficient, cost-effective, and simple to do.

For colonies requiring tens to hundreds of megawatts of electrical and thermal power, nuclear fission still beats all competing technologies as a function of mass and volume required to produce a given level of output. Only time will tell as to whether or not cold or hot fusion will supplant fission for utility grade power. Presently, the answer is a rather firm "no".

louis · 2017-05-29 04:29:53

I think if you are going to start referencing mid term technological developments, then I can throw back solar power satellites and microwave or laser beam to surface (already proven to some extent by Japanese companies).

http://spectrum.ieee.org/energywise/gre … olar-farms

The Japanese intend to have a 200 MW power plant in operation by 2028. If they do achieve that, then this technology would even be available for an early Mars Mission.

Improved battery performance works just as well for solar as nuclear.

At what point exactly do you think that we will need hundreds of MWs on Mars? 3.2 MW will allow you to grow enough food for 100 people (with no use of direct sunlight). 0.2 MW will cover life support for the same number. 0.6 MW will probably cover use of 10 vehicles during the day. 2 MW will probably cover all industrial processes. I'm struggling to see how we would get to even 10MW constant with 100 people (which would be 100 Kw per person - hugely more than we use on Earth, where artificially lit farming is virtually unknown).

You seem to be putting the energy cart before the people horse.

Well before we get to 100 people, the Mars settlers can in any case begin producing their own energy technologies e.g. solar reflectors plus turbines, storage heaters, batteries, PV panels, geothermal, and possibly methane capture. Whereas you will still want to be bringing in nuclear reactors at tonnes per mission - at a huge money and tonnage cost, when you could be importing industrial machines to hasten the development of Mars self-sufficiency. It doesn't make sense.

kbd512 wrote:

There's a place for solar power on the Mars exploration missions, but it's a complementary technology. PV panels work best in space, not on the surface of a planet. The rapidly developing Graphene-based batteries and super capacitors, combined with permanent batteries and homopolar generator technologies will supplant solar, and to a lesser extent nuclear, for prime surface power in the near future. NASA may still elect to use the low-cost, lightweight fission reactors they're developing, but ultimately total system mass, service life, and reliability determine the direction of electrical power generation technologies.
While basic life support and communications technologies continue to become more power-efficient, total power requirements continue to trend upwards as a function of everything else we want to do. We want battery-operated power tools, exoskeletons to assist with rapid cargo transfers, rovers, scouting robots, ice mining, farming, and even propellant plants. All that stuff requires power and lots of it.
As permanent battery technology develops, we'll see power sources integrated with low-consumption applications like personal electronics and life support equipment. Even so, primary power will consist of electric generators connected to more powerful permanent batteries. In this use case, primary power actually functions as a backup power source that is ordinarily allocated to energy-intensive applications such as farming, mining, or manufacturing rocket propellants.
In space, thin-film solar panels can provide primary power with permanent battery backups for life support. The fact that the panels are toast after six months is irrelevant when, in three to six months, our people will be on Mars (outbound from Earth) or Earth (inbound from Mars). The panels should be designed to fry during reentry at either end while still attached to the habitat module using something akin to magsafe power connector attachment points. This sort of solar panel disposal is driven by mass, manufacturing costs, and system complexity. It'll be far less costly to print thin-film panels, use them to provide power for the brief transits, and then discard them upon reentry compared to development of panels that last for many years and can be thermally protected and re-deployed on the surface. That's an unnecessary and costly engineering problem to solve.
The flexible thin-film panels are less sensitive to damage as a function of how they work and their expected service life. The fact that disposable panels can be more easily damaged is irrelevant in light of replacement costs, in comparison to the super-expensive hard panels that Orbital ATK manufactures for space stations and long duration deep space robotic missions. It may seem wasteful, but it's mass-efficient, cost-effective, and simple to do.
For colonies requiring tens to hundreds of megawatts of electrical and thermal power, nuclear fission still beats all competing technologies as a function of mass and volume required to produce a given level of output. Only time will tell as to whether or not cold or hot fusion will supplant fission for utility grade power. Presently, the answer is a rather firm "no".

RobertDyck · 2017-05-29 12:52:20

louis wrote:

I think if you are going to start referencing mid term technological developments, then I can throw back solar power satellites and microwave or laser beam to surface (already proven to some extent by Japanese companies).

(scream like a little girl) No no no no no. I thought was dead and buried.

Again, the best power transmission ever achieved is 30%, and the last work in the US only achieved that over a few miles. Transmitting power from space will require much greater distance. And it means a multi-megawatt power beam close to a city. You want to cook residents with microwaves? Even if aim isn't an issue, if an aircraft flies through the beam it will get cooked. And if you ignore all that, then look at cost:benefit ratio. Satellites are useful because sunlight is 24/7, while sunlight on Earth is only during the day. And sunlight on the surface is occluded by clouds and haze. Overall sunlight on the surface is only 30%. But power transmission from a solar array on Earth's surface is via power cable, so 100%. That means solar power satellites get 100% sun but 30% transmission, while solar panels on the ground get 30% sun and 100% transmission. That means the same power to the customer for an array of the same size. But solar power satellites require a launch vehicle to deliver to space that costs millions of dollars, while deployment on the ground requires a truck. Repair or maintenance in space requires a spacecraft and an astronaut in a spacesuit. And we don't even have Shuttle anymore. Repair or maintenance on the ground requires a pickup truck, and a technician in jeans and a shirt. Cost difference is extreme!

kbd512 · 2017-05-29 13:35:05

Louis,

Permanent batteries aren't really mid-term technological developments, it's a commercial product you can purchase. Scientists have known about these materials for decades, but until recently current output was rather low. However, these types of technologies are known to produce output, even when severely damaged internally. That said, these types of batteries produce virtually the same output for decades at a time. It's just materials science in action.

The Japanese scientists in the article you provided a link to managed to deliver a kew kilowatts of power over a few hundred meters. The solar collector alone for their 1GWe operational unit is expected to weigh 10,000t. The losses are huge. 100kWe to 200MWe in 7 years? Get real. That kind of mass transfer to Mars is also pure fantasy, even ten years from now, even using ITS. A set of molten salt reactors that produce 1GWe won't weigh 10,000t. On top of that, Mars is 1.5AU from the Sun, not 1AU.

A 650MWt (300MWe) LFTR is smaller in diameter than a VW Beetle and a little less than twice as long. It's the type of thing we can ship to Mars using existing rockets. The reactor vessel would be shipped completely empty (no moderator) and assembled / fueled on Mars. Small nuclear reactors don't require rockets that don't exist or technology development that's still science fiction, which is what beamed power truly is. This beamed power solar array would require 20 ITS flights to deliver it to Mars to produce half the output it would in Earth orbit.

The complete 400MWt (200MWe) IMSR core, less fuel, would weigh 170t. This is for a core using steam instead of CO2. If CO2 is the working fluid and the core has the graphite moderator removed, then mass can be reduced to something that Falcon Heavy can actually orbit. It's also the sort of thing that a semi-tractor trailer truck can actually deliver to the cape for launch. Concrete simply has to be locally sourced from Mars, but the reactor components have to come from Earth until metals production is firmly established on Mars. There are approximately 500t worth of reactor components for each 300MWe reactor that have to be delivered to Mars from Earth and it will take a decade or so to do that. Even with advanced fission reactor designs, producing 1GWe on Mars is a monumental task.

It's true that 10,500kg of solar panels can produce 1GWe on Mars, that's only peak power output for 4 hours per day. For the other 8 hours, you get substantially less. Then you get nothing for 12 hours per day. If you want more continuous output, then we're talking about radically scaling up the total system mass with more panels and unheard of battery capacity. I've said it before, but maybe I should repeat it. If the energy density of batteries is radically improved, then my objections to using solar go away.

To store 1kWh of electricity, and ignoring electrical heating requirements, then you need 5kg of the best Lithium-ion batteries we have. To store 1MWh of electricity, you need 5,000kg of batteries. To store 1GWh of electricity, you need 5,000,000kg of batteries. Multiply that by 12 to get a sense of what storage capacity is required to continuously output 1GWe. Divide 60,000,000kg (60,000t for a 12GWh capacity) by 4 to get a sense of what the mass of bleeding edge Graphene-based batteries weigh (15,000,000kg or 15,000t).

It's not that difficult to do the math on what this stuff weighs. If we could afford to send battleships to Mars, then it wouldn't matter what the power solution weighs, but we can't, so mass matters. We need to get back to reality as it pertains to solar power.

Last edited by kbd512 (2017-05-29 13:36:57)

louis · 2017-05-29 15:04:25

Well you are completely ignoring the points I am making which are:

1. We don't need anything like 300 MWe constant as we grow a settlement to 100 people. What could you possibly be using all that electricity for?

2. The Mars ISRU solution to energy - specifically (in the first place) concentrated solar plus turbine will have a mass penalty of approaching zero. Any importation of energy systems from Earth involves a mass penalty and prevents the settlement from importing much needed industrial machines and nutrients for agriculture.

3. Solar power does not require huge amounts of chemical batteries. Storage through production of methane/oxygen fuel is a much better option for general "failsafe" energy.

4. That said I think your chemical battery figures are wrong.

http://www.allaboutbatteries.com/Battery-Energy.html

Lithium ion batteries store 128 Whs per Kg. So for 5,000,000 kgs of batteries the figure is 128x 5million = 640 GWhs - not 1GWh!

But the reality is that as the settlement grows to 100 people, we'll probably need no more than about 5 tonnes of batteries.

Some of that tonnage can be produced on Mars as the settlement develops its industrial infrastructure.

kbd512 wrote:

Louis,
Permanent batteries aren't really mid-term technological developments, it's a commercial product you can purchase. Scientists have known about these materials for decades, but until recently current output was rather low. However, these types of technologies are known to produce output, even when severely damaged internally. That said, these types of batteries produce virtually the same output for decades at a time. It's just materials science in action.
The Japanese scientists in the article you provided a link to managed to deliver a kew kilowatts of power over a few hundred meters. The solar collector alone for their 1GWe operational unit is expected to weigh 10,000t. The losses are huge. 100kWe to 200MWe in 7 years? Get real. That kind of mass transfer to Mars is also pure fantasy, even ten years from now, even using ITS. A set of molten salt reactors that produce 1GWe won't weigh 10,000t. On top of that, Mars is 1.5AU from the Sun, not 1AU.
A 650MWt (300MWe) LFTR is smaller in diameter than a VW Beetle and a little less than twice as long. It's the type of thing we can ship to Mars using existing rockets. The reactor vessel would be shipped completely empty (no moderator) and assembled / fueled on Mars. Small nuclear reactors don't require rockets that don't exist or technology development that's still science fiction, which is what beamed power truly is. This beamed power solar array would require 20 ITS flights to deliver it to Mars to produce half the output it would in Earth orbit.
The complete 400MWt (200MWe) IMSR core, less fuel, would weigh 170t. This is for a core using steam instead of CO2. If CO2 is the working fluid and the core has the graphite moderator removed, then mass can be reduced to something that Falcon Heavy can actually orbit. It's also the sort of thing that a semi-tractor trailer truck can actually deliver to the cape for launch. Concrete simply has to be locally sourced from Mars, but the reactor components have to come from Earth until metals production is firmly established on Mars. There are approximately 500t worth of reactor components for each 300MWe reactor that have to be delivered to Mars from Earth and it will take a decade or so to do that. Even with advanced fission reactor designs, producing 1GWe on Mars is a monumental task.
It's true that 10,500kg of solar panels can produce 1GWe on Mars, that's only peak power output for 4 hours per day. For the other 8 hours, you get substantially less. Then you get nothing for 12 hours per day. If you want more continuous output, then we're talking about radically scaling up the total system mass with more panels and unheard of battery capacity. I've said it before, but maybe I should repeat it. If the energy density of batteries is radically improved, then my objections to using solar go away.
To store 1kWh of electricity, and ignoring electrical heating requirements, then you need 5kg of the best Lithium-ion batteries we have. To store 1MWh of electricity, you need 5,000kg of batteries. To store 1GWh of electricity, you need 5,000,000kg of batteries. Multiply that by 12 to get a sense of what storage capacity is required to continuously output 1GWe. Divide 60,000,000kg (60,000t for a 12GWh capacity) by 4 to get a sense of what the mass of bleeding edge Graphene-based batteries weigh (15,000,000kg or 15,000t).
It's not that difficult to do the math on what this stuff weighs. If we could afford to send battleships to Mars, then it wouldn't matter what the power solution weighs, but we can't, so mass matters. We need to get back to reality as it pertains to solar power.

SpaceNut · 2017-05-29 17:05:02

While I agree that solar has its places such as the journeys to and from earth to mars I am wondering about the effects of artifical gravity spin and even tumble for keeping the tracking assembly from wearing out. The ISS had premature wear out of I believe the bearing assembles that keep the panels tracking. So unless we have something better by now for this I think we need to make sure.

kbd512 · 2017-05-29 19:20:20

louis wrote:

Well you are completely ignoring the points I am making which are:
1. We don't need anything like 300 MWe constant as we grow a settlement to 100 people. What could you possibly be using all that electricity for?

1. Food for more colonists
2. More colonists
3. Mining
4. Rocket fuel (a relatively minor requirement since most people are staying on Mars)

louis wrote:

2. The Mars ISRU solution to energy - specifically (in the first place) concentrated solar plus turbine will have a mass penalty of approaching zero. Any importation of energy systems from Earth involves a mass penalty and prevents the settlement from importing much needed industrial machines and nutrients for agriculture.

A 1MW gas turbine plant uses hundreds of kilograms of fuel, per hour of operation, and requires hundreds of kilograms of oxygen, per hour of operation.

louis wrote:

3. Solar power does not require huge amounts of chemical batteries. Storage through production of methane/oxygen fuel is a much better option for general "failsafe" energy.

See above.

louis wrote:

4. That said I think your chemical battery figures are wrong.

I wish they were, but they're not.

louis wrote:

Lithium ion batteries store 128 Whs per Kg. So for 5,000,000 kgs of batteries the figure is 128x 5million = 640 GWhs - not 1GWh!
But the reality is that as the settlement grows to 100 people, we'll probably need no more than about 5 tonnes of batteries.

I'll try my best to explain this to you.

128Wh/kg * 5,000,000kg = 640,000,000Wh

640,000,000Wh = 640MWh

640,000,000,000Wh = 640GWh

The formula shown below is how you can determine how many kilograms of batteries are required to store a given amount of electrical power.

[Storage Requirement in Watt-hours] / [Watt-Hours per kilogram] = [kilograms of batteries needed to meet storage requirement]

1,000,000,000 (1GWh) / 128 (Wh/kg) = 7,812,500kg or 7,812.5t (metric tons)

For comparison purposes, a Flight I Arleigh-Burke class guided missile destroyer weighs 8,315t fully loaded. If we're using batteries, then we're talking about sending batteries that weigh approximately as much as an Arleigh-Burke class destroyer to Mars for every gigawatt-hour of electrical power storage available and roughly the same number of destroyers assigned to any of the seven fleets that the US operates to provide one gigawatt of continuous electrical power for 12 hours.

1 metric ton = 1,000kg

1,000 metric tons = 1,000,000kg

1 kilo-Watt hour = 1kWh = 1,000Wh = 5kg of Panasonic / Tesla 20700 cells

1 Mega-Watt hour = 1MWh = 1,000,000Wh = 5,000kg (5t) of Panasonic / Tesla 20700 cells

1 Giga-Watt hour = 1GWh = 1,000,000,000Wh = 5,000,000kg (5,000t) of Panasonic / Tesla 20700 cells

Here is how I arrived at those figures:

The best current mass-manufactured Lithium-ion batteries store 250 Watt-hours (Wh) of electrical power per kilogram (kg). These cells are known as the Panasonic / Tesla 20700 cells. 1kWh at 80% Depth-of-Discharge (DoD) requires 5kg of 20700 cells.

1,250Wh * .8 (80% DoD) = 1kWh

1,250Wh / 250Wh/kg = 5kg/kWh when the batteries store 250Wh or .25kWh per kg.

1,000,000 (1MWh) / 1,000 = 1,000 = 5,000kg of batteries

1,000,000,000 (1GWH) / 1,000 = 1,000,000 = 5,000,000kg of batteries

louis wrote:

Some of that tonnage can be produced on Mars as the settlement develops its industrial infrastructure.

Sure. Right after we get the electrical power to feed our colonists.

louis · 2017-05-30 09:50:00

1. Whilst there is merit in a food store for future use, we can't store food indefinitely and there is a mass and energy cost to storing it (especially on Mars). So if say you have 50 people, I doubt they will want to be producing food for more than 100 people. And if you are in a Musk-style scenario, with an ITS bringing in cargo at 450 tonnes a time, that sort of approach is pretty redundant as well.

More colonists, in due course, OK. But you aren't going to overshooting the runway by ridiculous amounts are you? Yes, you need to prepare accommodation habs, farm habs and life support. But would we be more than doubling the population every two years - I doubt it, Musk's plans not withstanding.

Mining - well I think that is taken into account in my and most people's estimates of energy requirements. Again, if you have 100 people, you won't be talking about mining tens of thousands of tonnes of stuff - probably just a few tonnes or tens of tonnes each year, unless you are looking to make things difficult for yourself.

Rocket fuel will be helpful in due course, but it depends how you configure your mission architecture. I favour a low mass Apollo style lander and ascender which won't require hundreds of tonnes of fuel and propellant.

2. I am talking about a solar powered turbine (as well as methane powered turbines). The power source is solar radiation. There is no combustion. Water is required but that can be condensed out and recycled.

3. It's true that as a form of storage, you will need substantial amounts of methane and oxygen, but that is not problematic. All the ingredients are readily available through Mars atmosphere and water. All you need really is an energy input, and that can come from PV.

4. Mea culpa. Maxima stupida. I did get my megas and gigas confused...

I think however that my point stands - that you are vastly inflating energy needs on Mars.

To get an idea of what 1 GWh is if you take average annual UK usage of 400 TWhs...

http://www.hi-energy.org.uk/Renewables/ … the-UK.htm

400 TWhs = 400,000 GWhs per annum - that's about 1095 GWhs a day. With a population of 60 million, I make that 18.25 KwHs per capita per day. It's true we use a lot of natural gas (methane) and petroleum (gasoline) to meet our energy needs. So let's increase that by a factor of six to 109 Kwhs per capita for Mars. For a population of 100 people that would mean a requirement of 10900 KwHs or 454 Kws constant. If we add in the farming requirement with artificial light, that would be an additional 33 KWs constant per person or 3300 Kws for 100 people. So 3754 KWs i.e. 3.745 Mw constant - the equivalent of one big wind turbine on Earth.

I think it is unhelpful to be talking about much larger energy requirements just in order to big up nuclear power. We should establish realistic energy budgets. Even that figure of 3.745 Mw for 100 people is probably way over the top because we can gradually begin to introduce more direct light farming as the settlement grows and we find ways of doing natural light agriculture on Mars.

The idea we will be need 5000 tonnes worth (1GwH) of batteries any time soon is just absurd. For a settlement of 100, I think probably no more than 10 tonnes of batteries would be needed and for most of the time they would be serving vehicles. Ten tonnes will give you 20,000 KwHs of storage allowing the settlement to function on emergency power for several days. Generally speaking I would expect night time power requirements to be met through methane/oxygen powered generators and heat storage. The chemical batteries would only come into play where you had a series of catastrophes which destroyed your PV panels, and your methane storage. Only a large meteorite strike could create that sort of scenario I think or possibly some sort of explosive event.

But of course, by the time your settlement is 100 strong, you will have all sorts of back up. I would expect there to be safely stored PV back up which would be brought into play after such a (remote chance) meteorite strike as well as below ground storage of methane and oxygen. We may well have developed iron nano fuel as well, which can be stored more conveniently than methane.

kbd512 wrote:

louis wrote:
Well you are completely ignoring the points I am making which are:
1. We don't need anything like 300 MWe constant as we grow a settlement to 100 people. What could you possibly be using all that electricity for?
1. Food for more colonists
2. More colonists
3. Mining
4. Rocket fuel (a relatively minor requirement since most people are staying on Mars)
louis wrote:
2. The Mars ISRU solution to energy - specifically (in the first place) concentrated solar plus turbine will have a mass penalty of approaching zero. Any importation of energy systems from Earth involves a mass penalty and prevents the settlement from importing much needed industrial machines and nutrients for agriculture.
A 1MW gas turbine plant uses hundreds of kilograms of fuel, per hour of operation, and requires hundreds of kilograms of oxygen, per hour of operation.
louis wrote:
3. Solar power does not require huge amounts of chemical batteries. Storage through production of methane/oxygen fuel is a much better option for general "failsafe" energy.
See above.
louis wrote:
4. That said I think your chemical battery figures are wrong.
I wish they were, but they're not.
louis wrote:
Lithium ion batteries store 128 Whs per Kg. So for 5,000,000 kgs of batteries the figure is 128x 5million = 640 GWhs - not 1GWh!
But the reality is that as the settlement grows to 100 people, we'll probably need no more than about 5 tonnes of batteries.
I'll try my best to explain this to you.
128Wh/kg * 5,000,000kg = 640,000,000Wh
640,000,000Wh = 640MWh
640,000,000,000Wh = 640GWh
The formula shown below is how you can determine how many kilograms of batteries are required to store a given amount of electrical power.
[Storage Requirement in Watt-hours] / [Watt-Hours per kilogram] = [kilograms of batteries needed to meet storage requirement]
1,000,000,000 (1GWh) / 128 (Wh/kg) = 7,812,500kg or 7,812.5t (metric tons)
For comparison purposes, a Flight I Arleigh-Burke class guided missile destroyer weighs 8,315t fully loaded. If we're using batteries, then we're talking about sending batteries that weigh approximately as much as an Arleigh-Burke class destroyer to Mars for every gigawatt-hour of electrical power storage available and roughly the same number of destroyers assigned to any of the seven fleets that the US operates to provide one gigawatt of continuous electrical power for 12 hours.
1 metric ton = 1,000kg
1,000 metric tons = 1,000,000kg
1 kilo-Watt hour = 1kWh = 1,000Wh = 5kg of Panasonic / Tesla 20700 cells
1 Mega-Watt hour = 1MWh = 1,000,000Wh = 5,000kg (5t) of Panasonic / Tesla 20700 cells
1 Giga-Watt hour = 1GWh = 1,000,000,000Wh = 5,000,000kg (5,000t) of Panasonic / Tesla 20700 cells
Here is how I arrived at those figures:
The best current mass-manufactured Lithium-ion batteries store 250 Watt-hours (Wh) of electrical power per kilogram (kg). These cells are known as the Panasonic / Tesla 20700 cells. 1kWh at 80% Depth-of-Discharge (DoD) requires 5kg of 20700 cells.
1,250Wh * .8 (80% DoD) = 1kWh
1,250Wh / 250Wh/kg = 5kg/kWh when the batteries store 250Wh or .25kWh per kg.
1,000,000 (1MWh) / 1,000 = 1,000 = 5,000kg of batteries
1,000,000,000 (1GWH) / 1,000 = 1,000,000 = 5,000,000kg of batteries
louis wrote:
Some of that tonnage can be produced on Mars as the settlement develops its industrial infrastructure.
Sure. Right after we get the electrical power to feed our colonists.

SpaceNut · 2017-06-02 20:29:20

I am going to put out there that going to mars with a crew will use based on the ISS about the same levels of energy which is created by the 16 arrays that are grouped together to form 8 rotating wings as they are grouped in pairs. https://www.nasa.gov/mission_pages/stat … TISlzVIosY

Each wing is 115 feet long by 38 feet wide. Two blankets of solar cells make up a solar array wing, Each solar array wing weighs more than 2,400 pounds and uses 32,800 solar array cells. Altogether, the four sets of arrays can generate 84 to 120 kilowatts of electricity -- enough to provide power to more than 40 homes. When the station is in sunlight, about 60 percent of the electricity that the solar arrays generate is used to charge the station's batteries.

Keep in mind thats with 1300 watts hitting the panels and not the 430 watts on mars surface. So if we used the same panels on mars we will need to 3 times as many to do the same job. That said we would use panels cells that are much higher efficencies of course in order to keep the amount of them lower.

https://en.wikipedia.org/wiki/Solar_pan … spacecraft

But thats not all as the mass continues to mount up as we need more stuff to support the power. We will up grade to a higher density battery type but this is what it will take to make it work. With panels that move as stationary panels will output 30% less when compared to those that move.

https://en.wikipedia.org/wiki/Electrica … ce_Station

http://www.solaripedia.com/13/128/1174/ … taics.html.

rechargeable nickel-hydrogen batteries to provide continuous power during the "eclipse" part of the orbit (35 minutes of every 90 minute orbit).

So 84 to 120 kilowatts for 60% recharge into 55 minutes for recharging leave 12K watts up to 48K watts for life support depending on shadow on the panels and 35 minutes in the dark to discharge them.

3 times the ISS arrays on Mars would be 140M^2 but batteries are a different problem as to get the same ratio for the day night cycle means we need to compare the day which is most likely 9 hours max of useable light for the array with 15 being to dark to be used for charging. This means we will need even more batteries as the duration for night time is not shorter than the day period but longer. So will will need even more charge currents from the day to compensate for the longer night which is even more panels....

louis · 2017-06-03 07:02:35

The calculations may be right but the scenario is wrong. The authors here quote (page 882) a 1850 sq. metre array weighing in at 1.67 tons and being the equivalent of a 100 Kw nuclear reactor:

http://www.uapress.arizona.edu/onlinebk … rces30.pdf

Why are you quoting chemical batteries for primary storage when we can store the energy as (surface ISRU) methane/oxygen?

SpaceNut wrote:

I am going to put out there that going to mars with a crew will use based on the ISS about the same levels of energy which is created by the 16 arrays that are grouped together to form 8 rotating wings as they are grouped in pairs. https://www.nasa.gov/mission_pages/stat … TISlzVIosY
http://www.nasa.gov/images/content/3610 … s-xltn.jpg
Each wing is 115 feet long by 38 feet wide. Two blankets of solar cells make up a solar array wing, Each solar array wing weighs more than 2,400 pounds and uses 32,800 solar array cells. Altogether, the four sets of arrays can generate 84 to 120 kilowatts of electricity -- enough to provide power to more than 40 homes. When the station is in sunlight, about 60 percent of the electricity that the solar arrays generate is used to charge the station's batteries.
Keep in mind thats with 1300 watts hitting the panels and not the 430 watts on mars surface. So if we used the same panels on mars we will need to 3 times as many to do the same job. That said we would use panels cells that are much higher efficencies of course in order to keep the amount of them lower.
https://en.wikipedia.org/wiki/Solar_pan … spacecraft
But thats not all as the mass continues to mount up as we need more stuff to support the power. We will up grade to a higher density battery type but this is what it will take to make it work. With panels that move as stationary panels will output 30% less when compared to those that move.
https://en.wikipedia.org/wiki/Electrica … ce_Station
http://www.solaripedia.com/13/128/1174/ … taics.html.
rechargeable nickel-hydrogen batteries to provide continuous power during the "eclipse" part of the orbit (35 minutes of every 90 minute orbit).
So 84 to 120 kilowatts for 60% recharge into 55 minutes for recharging leave 12K watts up to 48K watts for life support depending on shadow on the panels and 35 minutes in the dark to discharge them.
3 times the ISS arrays on Mars would be 140M^2 but batteries are a different problem as to get the same ratio for the day night cycle means we need to compare the day which is most likely 9 hours max of useable light for the array with 15 being to dark to be used for charging. This means we will need even more batteries as the duration for night time is not shorter than the day period but longer. So will will need even more charge currents from the day to compensate for the longer night which is even more panels....

SpaceNut · 2017-06-03 08:05:47

http://nsl.caltech.edu/home/solar-fuels/

The chemical bonds found in fuels are the most dense way to store energy outside of an atomic nucleus. For example, the energy density of gasoline is 60 times that of the best battery. In other words, 60 tons of batteries would be needed to store the energy of 1 ton of gasoline.

Problem is this is not accounting for the oxydiser needed to release the energy.

https://www.technologyreview.com/s/4019 … t-so-soon/

Even in its densest form (liquid), hydrogen has only one-third as much energy per liter as gasoline. If stored as compressed gas at 300 atmospheres (a more practical option), it delivers less than one-fifth the energy per volume as gasoline.

I recall another hydrogen fuel cell economy work from MIT that did use the solar cell to split hydrogen to store in large Liquid propane tanks which would then be used for fuel cells.

http://www.infinite-energy.com/images/p … conomy.pdf

louis · 2017-06-03 09:11:19

Yes, oxygen is required to burn the methane but only four times as much. So that would make it the equivalent of 12 tons of batteries rather than 60 if I've got that right. Not as good, but still way more efficient (actaully methane has more energy per kg than gasoline). So that is what I see as the primary form of energy storage from solar on Mars. I don't think we need more than a couple of tonnes of chemical batteries for Mission One. The initial methane and oxygen production can take place during the pre-human landing phase with automated machines storing oxygen from CO2 and from water concentrated out of the atmosphere and making methane with the carbon, oxygen and hydrogen derived from the water and atmosphere. The power for that will come from a PV array. By the time humans arrive they will already have access to thousands of KWHs of power even before they roll out the PV they have brought with them from Earth.

SpaceNut wrote:

http://nsl.caltech.edu/home/solar-fuels/
The chemical bonds found in fuels are the most dense way to store energy outside of an atomic nucleus. For example, the energy density of gasoline is 60 times that of the best battery. In other words, 60 tons of batteries would be needed to store the energy of 1 ton of gasoline.
Problem is this is not accounting for the oxydiser needed to release the energy.
https://www.technologyreview.com/s/4019 … t-so-soon/
Even in its densest form (liquid), hydrogen has only one-third as much energy per liter as gasoline. If stored as compressed gas at 300 atmospheres (a more practical option), it delivers less than one-fifth the energy per volume as gasoline.
I recall another hydrogen fuel cell economy work from MIT that did use the solar cell to split hydrogen to store in large Liquid propane tanks which would then be used for fuel cells.
http://www.infinite-energy.com/images/p … conomy.pdf

SpaceNut · 2017-06-03 13:15:10

The house that I remember is meantioned in the article:
http://www.nytimes.com/2007/05/20/magaz … lar-t.html

Does a Hydrogen Economy Make Sense?

Direct solar to batteries is somewhere 90% and up for what gets put into the system for storage and returned out from it when needed.

Solar conversion to storage in methane and oxygen is even lower for efficiency as the first loss is in converting water in electrolysis (1st Loss), the next is in pumping co2 into the electrolysis sytem to create Co for use in the Sabatier reactor and additonal Oxygen (2nd loss), then there is the reactors energy needs to get it started and maintained for converting Co + H into merthane and water (3rd loss). Stores of this methane and oxygen when burn do not covert again to effeicinet energy (4th Loss) for use with if we have a closed loop for the exhaust for recapture of some unburn methane + Co2 + water to have recycled back into the process (5th Loss).

Its the totals that add up which make it only viable when we use insitu resource to hold and make it all happen which allows for it to come into its own as we get to use the fuel saved for more than just making night time power.

SpaceNut · 2017-06-03 13:23:27

Found the house running on solar hydrogen:
https://www.scientificamerican.com/arti … gen-house/
http://hydrogenhouseproject.org/
http://hydrogenhouseproject.org/press-releases.html
http://hydrogenhouseproject.org/the-hydrogen-house.html

Back on the burning of methane andwith oxygen I think using a fuel cell would be a better choice and here is an article on it.
https://www.technologyreview.com/s/5185 … generator/

SpaceNut · 2017-06-03 19:17:07

nickel-hydrogen batteries of the ISS are designed to operate at a 35% depth of discharge (DOD) maximum during normal operation. At present, the International Space Station hosts 48 Nickel-Hydrogen batteries installed in four locations known as the Integrated Equipment Assemblies (IEA) which reside on the four truss segments that have Solar Arrays attached to them with each IEA holding power conditioning & switching equipment for two of the Station’s eight power channels.

http://ac.els-cdn.com/S1876610214010297 … c62b0eb17c

The new Lion batteries each host three banks of ten cells and comply with the battery ORU form factor of 104 x 94 x 48 centimeters with a total mass of 197 Kilograms. The new batteries have an end of life capacity of 48 Amp-hours and are good for at least 60,000 charge-discharge cycles, equivalent to ten years of ISS operations.

48 x 197 Kg = 9,456 kg or 9.5 mT for batteries that only see use for 35 minutes and charging for 55 minutes.

Here is the structure of what was replaced with the new ION battery boxes... https://ntrs.nasa.gov/archive/nasa/casi … 012048.pdf

The box is made up of 30 cells in series at 3.7v nominal with a 134 a/hr rating which is 111 v bus.

from pg 15 they are limiting the charge current to 30 amps while the discharge is set at 45 amps to control internal heating under use.

A full voltage charge for LION is 4.1V with fully discharged set as 2.7V for the 35%. at the end of just 35 minutes of drain current.

So what is the ration of solar cell power to that to which satifies that battery night time drain with some charge still remaining?

https://www.nrel.gov/tech_deployment/st … rgy-ratios

http://euanmearns.com/how-much-battery- … stem-need/

http://princetonpower.com/images/pdfsne … ct2016.pdf

louis · 2017-06-03 19:39:13

If you can do it, it's not a loss. I think you are confusing ongoing energy efficiency with the demands of Mission One. Remember - you are using a hell of a lot of energy just to get to Mars. Using a little bit more to make some methane is really no more than an afterthought.

SpaceNut wrote:

The house that I remember is meantioned in the article:
http://www.nytimes.com/2007/05/20/magaz … lar-t.html
Does a Hydrogen Economy Make Sense?
Direct solar to batteries is somewhere 90% and up for what gets put into the system for storage and returned out from it when needed.
Solar conversion to storage in methane and oxygen is even lower for efficiency as the first loss is in converting water in electrolysis (1st Loss), the next is in pumping co2 into the electrolysis sytem to create Co for use in the Sabatier reactor and additonal Oxygen (2nd loss), then there is the reactors energy needs to get it started and maintained for converting Co + H into merthane and water (3rd loss). Stores of this methane and oxygen when burn do not covert again to effeicinet energy (4th Loss) for use with if we have a closed loop for the exhaust for recapture of some unburn methane + Co2 + water to have recycled back into the process (5th Loss).
Its the totals that add up which make it only viable when we use insitu resource to hold and make it all happen which allows for it to come into its own as we get to use the fuel saved for more than just making night time power.

SpaceNut · 2017-06-04 08:42:10

Here is the complexitity of solar and batteries for all the stuff that is reqired to support it.

The battery charge/discharge units (BCDUs) regulate the amount of charge put into the battery. Each BCDU can regulate discharge current from two battery ORUs (Orbital Replacement Unit, a series-connected pack of 38 Ni-H2 cells), and can provide up to 6.6 kW to the Space Station. Which are now the newer LION packs meantioned above for battery mass.

During insolation, the BCDU provides charge current to the batteries and controls the amount of battery overcharge. Each day, the BCDU and batteries undergo sixteen charge/discharge cycles. The Space Station has 24 BCDUs, each weighing 100 kg.

24 x 6.6 Kwatt = 158.4 K watt

That said the battery box is 3.3 kWatts each at 111v output which means 30 Amp delivery or sinces nearly used for just shy of an hour the same a/hr would be close enough. Which is 12K watts up to 48K watts for life support and daily activity.

louis · 2017-06-04 11:05:36

Nuclear reactors are much simpler- that's why you can knock them up in your back yard.

SpaceNut wrote:

Here is the complexitity of solar and batteries for all the stuff that is reqired to support it.
https://upload.wikimedia.org/wikipedia/ … bution.png
The battery charge/discharge units (BCDUs) regulate the amount of charge put into the battery. Each BCDU can regulate discharge current from two battery ORUs (Orbital Replacement Unit, a series-connected pack of 38 Ni-H2 cells), and can provide up to 6.6 kW to the Space Station. Which are now the newer LION packs meantioned above for battery mass.
During insolation, the BCDU provides charge current to the batteries and controls the amount of battery overcharge. Each day, the BCDU and batteries undergo sixteen charge/discharge cycles. The Space Station has 24 BCDUs, each weighing 100 kg.
24 x 6.6 Kwatt = 158.4 K watt
That said the battery box is 3.3 kWatts each at 111v output which means 30 Amp delivery or sinces nearly used for just shy of an hour the same a/hr would be close enough. Which is 12K watts up to 48K watts for life support and daily activity.

kbd512 · 2017-06-04 12:47:09

louis wrote:

Nuclear reactors are much simpler- that's why you can knock them up in your back yard.

The Kilopower nuclear reactor is pretty simple. There's one moving control rod that controls reactivity. That's pretty hard to mess up.

Last edited by kbd512 (2017-06-04 12:51:16)

SpaceNut · 2017-10-08 15:11:33

Sumerized discusion:

Oldfart1939 indicated that SAFE-400 fission reactors, would be no problem in rapidly getting those online.
GW Johnson said that the government monopoly on all things nuclear means they wouldn't give Musk any SAFE-400 and that soal would be how Musk would go to mars which would be much to the enjoyment of Lious.
kbd512 said that NASA and DOE are investing in KiloPower. With my echo that I did no feel that anyone other than a Nasa mission would get them. While kbd512 feels that they can since corporate entities have nuclear power plants.

So bump goes the topic to bring it back into focus if we are not getting any nuclear power for a mars mission that is not Nasa Sponsered...

SpaceNut · 2018-12-08 21:13:58

Bump looking for the 31 degree isolation for mars numbers

SpaceNut · 2019-07-14 16:00:05

Bumping for technology developement is also another good topic to have put the link within

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