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Re:Blue Origin manufactured solar cell prototype from lunar ... by schiffern on Tuesday February 14, 2023 @09:28PM (#34799262)
>Storing 14+ days... is... massive

...which is why you want to be extra careful in how mass-efficiently you're 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.

Nuclear is a popular notion, but the real-world economics don't favor it. Effectiveness beats elegance.[0]

[0] https://spacecraft.ssl.umd.edu/akins_laws.html

Re:Blue Origin manufactured solar cell prototype from lunar ... by mlyle on Wednesday February 15, 2023 @12:44AM (#34800529)
> 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.

Re:Blue Origin manufactured solar cell prototype from lunar ... by schiffern on Wednesday February 15, 2023 @02:03AM (#34800914)
Thanks, yes I meant to mention liquefaction but then ADD.

You have to do the trade between liquefaction and storing oxygen as a pressurized gas. Reusing a single Starship's propellant tanks, for example, at 6 bar would hold ~14 metric tons of oxygen, enabling a continuous lunar population of over 1,000 people.

The compression or liquefaction energy isn't a show-stopper necessarily, 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-co...