Power options for a Mars settlement

[guckyfan]

Anyone who'se found a draught in a house will now that a small airflow can suck out a lot of heat from a structure. 

When you have that kind of draught in a martian habitat you have a much bigger problem than heat loss.

[Vultur]

Yeah and one would think habitats would be insulated...

[john smith 19]

Yeah and one would think habitats would be insulated...

Personally I would think they'd be buried given the radiaton background level and low surface temperatures at night.

[sanman]

Came across this article about GE's supercritical CO2 turbine, which although small and lightweight, could be used to power a small city:

https://www.technologyreview.com/s/601218/desk-size-turbine-could-power-a-town/

So what would be the best scenario to use this thing for power conversion on Mars? Hook it up to a nuclear reactor? What about geothermal/areothermal?

Or given Mars' unique environment, is there something better than supercritical CO2 to run a turbine with?
I've only assumed that the more efficient size/weight package of this turbine, coupled with the abundance of atmsopheric CO2 on Mars, would make it a good candidate.

[john smith 19]

Came across this article about GE's supercritical CO2 turbine, which although small and lightweight, could be used to power a small city:

https://www.technologyreview.com/s/601218/desk-size-turbine-could-power-a-town/

So what would be the best scenario to use this thing for power conversion on Mars? Hook it up to a nuclear reactor? What about geothermal/areothermal?

Or given Mars' unique environment, is there something better than supercritical CO2 to run a turbine with?
I've only assumed that the more efficient size/weight package of this turbine, coupled with the abundance of atmsopheric CO2 on Mars, would make it a good candidate.

The unit shown in the picture GE Global Research have released is sized for 10MW, which would be adequate for about 166 people even with the worst case power estimate of 60Kw/person.

The British AGR did 40bar at 650c but CO2 goes supercritical at above 73.9bar. I don't think anyone's run a gas cooled reactor at that pressure.  Gas reactors also tend to be quite big for their power output. It's not clear to me if that's due to inherent physics or just very conservative design.

People keep talking about Fission Power Systems for Mars but no one is anywhere near the scale needed, unless you like the idea of Mars littered with large numbers of spent nuclear fuel cores. 

A key issue for all designs is what if the LV crashes and dumps it in the sea. Water is a good moderator, and moderator behavior is inversely proportional to temperature. It's a design requirement that a space nuclear system not go critical even if it's suddenly put into a much better moderating environment than air or vacuum (and that environment floods inside the reactor). This may explain the US fondness for fast or epithermal spectrum designs, despite their need for substantial enrichment.

[Robotbeat]

Spent nuclear fuel cores sounds like a great idea to help terraform the planet! Long-duration decay heat could help liberate volatiles from the soil.

[Kansan52]

Well, they continued to have power, otherwise they would have frozen.

The MERs have ²³⁸Pu-powered Radioisotope Heater Units (RHUs) to provide heating for precisely this reason.  So they could survive with zero power for some period of time and still not freeze because of the RHU power.

Sorry to come late to this discussion. The MERS were never expected to last the Martian winter due to dust build-up on the PVs. The RHUs could not keep them warm enough (Spirit). Then the dust devils unexpectedly cleared the PVs. Even then, only southern exposure gave enough sun light to survive. Once Spirit got stuck and could not park in 'winter mode', it froze up. So both are needed.

[Bob Shaw]

A key issue for all designs is what if the LV crashes and dumps it in the sea.

This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins. Unlike the Moon, Mars rotates in 24hrs, so no need to deal with 14 days of night. The Moon is a different matter.

[john smith 19]

A key issue for all designs is what if the LV crashes and dumps it in the sea.

This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins. Unlike the Moon, Mars rotates in 24hrs, so no need to deal with 14 days of night. The Moon is a different matter.

A fair point, but this still leaves the question of what happens in a prolonged dust storm.

I think some system to tap the temperature difference between Mars surface and sub surface temp (which cannot be stopped by dust) is the way to have a backup power system.

[sanman]

A fair point, but this still leaves the question of what happens in a prolonged dust storm.

I think some system to tap the temperature difference between Mars surface and sub surface temp (which cannot be stopped by dust) is the way to have a backup power system.

You mean some sort of ground loop heating?

Even in spite of Mars' thin atmosphere, could there be some way to harness wind power on Mars during a dust storm - maybe using a very large and lightweight wind turbine?

[CuddlyRocket]

Even in spite of Mars' thin atmosphere, could there be some way to harness wind power on Mars during a dust storm - maybe using a very large and lightweight wind turbine?

'Very large' and 'lightweight' tends to be inconsistent! I suspect that for the mass required you'd get more power by adding more solar and storage.

There are a number of potential back-up power systems to replace solar during prolonged dust storms (nuclear wouldn't be much affected, of course), the most obvious being batteries and ICE generators or fuel cells utilising stored ISRU methalox. Then there's the strategy of turning off non-essential power-using activities. Finally, a dust storm wouldn't reduce the output of solar to zero - it seems the MERs worst reduction was ~80% - and such a storm wouldn't prevent base personnel cleaning the solar cells manually.

[inonepiece]

A key issue for all designs is what if the LV crashes and dumps it in the sea.

This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins.

What do you both imagine might happen if it dumps in the sea?

[sewebster]

What do you both imagine might happen if it dumps in the sea?

[Okie_Steve]

The up and coming new solar cell tech is lead halide perovskite which is cheap and easy to manufacture as an aqueous solution. In just a few years they've already hit 20% with no real end in site. Certainly not viable yet but it will be a few days before they need them on mars. One of the big problem right now is degradation due to atmospheric water, probably not much of an issue on mars. Early indications are that they are well suited to space applications with low temperatures and high radiation flux, exhibiting little degradation compares to silicon or gallium cells. If there is Thorium on mars then there is probably lead at too. Now if SpaceX could just find someone in the solar power industry to look into it ... Definitely something to keep and eye on for the future.

[inonepiece]

Ha.  I assume you are joking sewebster, but there are always people who won't realize it...

[sewebster]

Ha.  I assume you are joking sewebster, but there are always people who won't realize it...

Probably a good rule of thumb to always assume I am joking...

[john smith 19]

You mean some sort of ground loop heating?

No I was thinking of a low BP liquid used to drive a turbine. On Earth such systems have generated 500Kw/ borehole.  However just raw temperature management is likely to be an issue on Mars. The day/night temperature swing seems quite high and being able to manage that with relatively passive systems sounds like a good idea.

Even in spite of Mars' thin atmosphere, could there be some way to harness wind power on Mars during a dust storm - maybe using a very large and lightweight wind turbine?

I think Robobeat referenced a NASA report earlier in the thread. The fact remains the density is about 1% of Earth's density means even if you get an average higher speed you still need a lot of collection area to collect enough power.

[alexterrell]

A key issue for all designs is what if the LV crashes and dumps it in the sea.

This is indeed the key issue, and is the reason why PV for Mars wins, wins, and wins.

What do you both imagine might happen if it dumps in the sea?

It would disintegrate into sub critical parts - once the range safety officer presses the trigger, or upon a high speed impact - and spread some low enriched Uranium around on the sea bed.

As long as the reactor hasn't been operating, there would be no fission products and hence no radioactive danger.

There'd be less concern than there would be for a large Plutonium RTG.

[john smith 19]

It would disintegrate into sub critical parts - once the range safety officer presses the trigger, or upon a high speed impact - and spread some low enriched Uranium around on the sea bed.

You might like to check the enrichment levels in space nuclear systems.

The ones that have been fielded or study are well into the HEU range IE 20%+, usually around 90%+ U235

As long as the reactor hasn't been operating, there would be no fission products and hence no radioactive danger.

Uranium and Plutonium are highly toxic without being radioactive.

The NASA estimate for SNR development on one slide was $19Bn.

I hope that's wrong, but it's their estimate. 

[enzo]

No mention yet of solar + flywheel. For storage during long dust storms, seems like a high-reliability, high-density, overall easy option compared to large quantities of batteries, stored heat or stored fuel. No risk of leaks, fires, hopefully little chance of RUD. Additionally it could provide bursts of high current for things like welding, hot water, ovens, without causing a brownout.