4 ms·

>The bigger problem is how practical is it to use PV at all on much of the moon. I think part of the solution will involve using "regular stuff" (which can be

>The bigger problem is how practical is it to use PV at all on much of the moon. I think part of the solution will involve using "regular stuff" (which can be sourced from lunar atoms) like batteries. Don't use lithium batteries to continuously power an oxygen generator. Instead, have an enlarged oxygen generator and store half the flow for use at night. Don't use lithium batteries to power a heater at night, instead "pre-charge" heat in a dirt thermal mass during the day. Don't use lithium batteries to power a continuous CO2 scrubber, instead use a liquid amine scrubber and recharge the fluid tanks during the day. Etc etc Obviously you need to do in-depth tradeoff math for each case, but my napkins say "the system is the battery" wins in many cases.

paranoidrobot 4y ago
Lunar night being about 14 days might make that a bit more difficult for any permanent settlement. Storing 14+ days worth of <everything> is going to mean massive amounts of storage.
- mlyle 4y ago
  Yup. Nuclear seems likely to be part of the solution.
- schiffern 4y ago
  >Storing 14+ days... is... massive ...which is why you want to be extra careful in how mass-efficient you are storing it. A tank of liquid oxygen masses only a few percent of its contents, and its contents store more chemical energy per mass than a lithium battery. Later on, insulated tanks are vastly easier to produce from lunar materials vs batteries. These are all nice leverage multipliers. MEA amine solution is made of 80% lunar-abundant elements, and stores 22% its mass in CO2.[0] Importing the amine, tanks, and extra equipment requires under 3 kg/person for energy storage, vs 34 kWh[1] of batteries. Nuclear is a popular notion, but the real-world economics don't seem to favor it. Effectiveness beats elegance,[2] apparently. [0] https://en.wikipedia.org/wiki/Amine_gas_treating https://en.wikipedia.org/wiki/Amine_gas_treating [1] https://www.nasa.gov/sites/default/files/files/Gellett_SolidStateAirPurification.pdf https://www.nasa.gov/sites/default/files/files/Gellett_Solid... [2] https://spacecraft.ssl.umd.edu/akins_laws.html https://spacecraft.ssl.umd.edu/akins_laws.html
  - mlyle 4y ago
    > A tank of liquid oxygen masses only a few percent of its contents, and its contents store more chemical energy per mass than a lithium battery. Making liquid oxygen (as opposed to gaseous oxygen) is not a terribly efficient process.
    - schiffern 4y ago
      Naturally, there's a trade between LOX and pressurized oxygen gas. Reused propellant tanks of one Starship at 6 bar would hold ~14 metric tons of oxygen, enabling a continuous lunar population of over 1,000 people. The energy for compression or liquefaction isn't necessarily a show-stopper, it just works into the total energy efficiency of the storage system. Compression is nice because practical isothermal compressors are now being demonstrated.[0] Both liquefaction and compression require cooling. I do think it probably makes sense to do the thermal storage trick in reverse also, storing up a bank of "cold" at night to be used during the day. The thermal radiator panels still provide (derated) cooling in the day, but the thermal storage pool time-shifts the natural oversupply of cooling power at night. [0] https://newatlas.com/good-thinking/carnot-centrifugal-air-compressor/ https://newatlas.com/good-thinking/carnot-centrifugal-air-co...
- tomrod 4y ago
  Is setting up shop at the poles feasible?
AlphaSite 4y ago
I suspect there are some great solutions to power storage on the moon, eg why not store power in molten metals/substances? The lack of an atmosphere would help massively reduce thermal loss, and as you already have a refinery much of the infrastructure for this already exists.
- thworp 4y ago
  > The lack of an atmosphere would help massively reduce thermal loss Care to elaborate? As an interested layperson I always thought the major factor for losses in open air was radiation into space. As such an atmosphere's thermal mass would be benfitial, no?

paranoidrobot 4y ago

Lunar night being about 14 days might make that a bit more difficult for any permanent settlement. Storing 14+ days worth of <everything> is going to mean massive amounts of storage.

mlyle 4y ago
Yup. Nuclear seems likely to be part of the solution.
schiffern 4y ago
>Storing 14+ days... is... massive ...which is why you want to be extra careful in how mass-efficient you are storing it. A tank of liquid oxygen masses only a few percent of its contents, and its contents store more chemical energy per mass than a lithium battery. Later on, insulated tanks are vastly easier to produce from lunar materials vs batteries. These are all nice leverage multipliers. MEA amine solution is made of 80% lunar-abundant elements, and stores 22% its mass in CO2.[0] Importing the amine, tanks, and extra equipment requires under 3 kg/person for energy storage, vs 34 kWh[1] of batteries. Nuclear is a popular notion, but the real-world economics don't seem to favor it. Effectiveness beats elegance,[2] apparently. [0] https://en.wikipedia.org/wiki/Amine_gas_treating https://en.wikipedia.org/wiki/Amine_gas_treating [1] https://www.nasa.gov/sites/default/files/files/Gellett_SolidStateAirPurification.pdf https://www.nasa.gov/sites/default/files/files/Gellett_Solid... [2] https://spacecraft.ssl.umd.edu/akins_laws.html https://spacecraft.ssl.umd.edu/akins_laws.html
- mlyle 4y ago
  > A tank of liquid oxygen masses only a few percent of its contents, and its contents store more chemical energy per mass than a lithium battery. Making liquid oxygen (as opposed to gaseous oxygen) is not a terribly efficient process.
  - schiffern 4y ago
    Naturally, there's a trade between LOX and pressurized oxygen gas. Reused propellant tanks of one Starship at 6 bar would hold ~14 metric tons of oxygen, enabling a continuous lunar population of over 1,000 people. The energy for compression or liquefaction isn't necessarily a show-stopper, it just works into the total energy efficiency of the storage system. Compression is nice because practical isothermal compressors are now being demonstrated.[0] Both liquefaction and compression require cooling. I do think it probably makes sense to do the thermal storage trick in reverse also, storing up a bank of "cold" at night to be used during the day. The thermal radiator panels still provide (derated) cooling in the day, but the thermal storage pool time-shifts the natural oversupply of cooling power at night. [0] https://newatlas.com/good-thinking/carnot-centrifugal-air-compressor/ https://newatlas.com/good-thinking/carnot-centrifugal-air-co...
tomrod 4y ago
Is setting up shop at the poles feasible?

AlphaSite 4y ago

I suspect there are some great solutions to power storage on the moon, eg why not store power in molten metals/substances? The lack of an atmosphere would help massively reduce thermal loss, and as you already have a refinery much of the infrastructure for this already exists.

thworp 4y ago
> The lack of an atmosphere would help massively reduce thermal loss Care to elaborate? As an interested layperson I always thought the major factor for losses in open air was radiation into space. As such an atmosphere's thermal mass would be benfitial, no?