Power options for a Mars settlement

[lamontagne]

Greenhouses would reduce this by some significant fraction,

Only if there aren't additional energy costs elsewhere, due to thermal issues (for example). Or additional infrastructure costs to solve those issues (such as day/night counter-cycling heat-sinks, deployable insulating night covers, etc) that add to the ISRU-materials and energy-of-production demands on the early settlement.

Given the alien environment, and lack of reasonable analogies on Earth, IMO people should take the numbers from fully artificial grow-rooms (as you did) and assume that's the minimum for any ag on Mars. (The reasoning being, as I said earlier, if your numbers don't work without assuming near-free agriculture, then your margins are too slim for the unexpected realities of Mars.)

Grow rooms with staged growing patterns might allow for a nearly constant demand

You'll almost certainly need supplemental lighting in greenhouses -- even if you're not trying to maximise productivity, you will still need to mimic natural seasonal variation to trigger key stages of growth (such as flowering/fruiting). In which case, you can have staged growing in greenhouses just as you can in grow-rooms. It's not a "trade" between the two.

Should have added, ' if greenhouses are built at all, they will need to provide food for less energy overall'
As for the trade in growing times, I agree, however some grow rooms could operate all night, leveling out demand for a nuclear reactor.  Otherwise you would need to have a number of reactors idle at night.

[lamontagne]

If somebody was serious about nuclear power on Mars and in space, but did not have access to nuclear materials, could they build 'the rest' of the reactor to test our components and add in the actual core at the end?  I believe Kilopower did something like that, using a core simulator in some of their testing?
You could have a 5 MW electrical heater element, at 1200°C, for example, mimicking a core for a 2 MWe reactor?
Or are the nuclear elements of a design more important that purely thermal loads?
Perhaps the electrical conductors might significantly alter the geometry of the core?

[Vultur]

Taking LMTs numbers in the image 100 kWh/day for 2500 kg per day feeds about 2.5 persons per day if they eat only wheat.  100 kWh/day divided by 2.5 = an average power of 40 kW per person.
Most foods hold less power than wheat. 

Maybe calorie density per pound of food, but per growing area wheat is actually rather poor as staple crops go.

There's a reason Andy Weir picked potatoes...

[lamontagne]

Taking LMTs numbers in the image 100 kWh/day for 2500 kg per day feeds about 2.5 persons per day if they eat only wheat.  100 kWh/day divided by 2.5 = an average power of 40 kW per person.
Most foods hold less power than wheat. 

Maybe calorie density per pound of food, but per growing area wheat is actually rather poor as staple crops go.

There's a reason Andy Weir picked potatoes...

All here: https://marspedia.org/Food
It tends to average out but potatoes are 80% edible, rather than 50% for wheat.
Winners are beans and bananas, but potatoes are very good.

[LMT]

...per growing area wheat is actually rather poor as staple crops go.

There's a reason Andy Weir picked potatoes...

All here: https://marspedia.org/Food

The values are high but remain below record yields...

Your table actually states the record yield for wheat, from Bugbee & Salisbury.  That's not "theoretical" or "below record", but the achieved record, with calorie density an order of magnitude beyond potatoes, in your table.

Most foods hold less power than wheat.  However, there are biological reactors that have higher yields.

Calories = energy.  Do any reactors truly have higher yields?  What are the facts?  They should be in your article.

[lamontagne]

...per growing area wheat is actually rather poor as staple crops go.

There's a reason Andy Weir picked potatoes...

All here: https://marspedia.org/Food

The values are high but remain below record yields...

Your table actually states the record yield for wheat, from Bugbee & Salisbury.  That's not "theoretical" or "below record", but the achieved record, with calorie density an order of magnitude beyond potatoes, in your table.

Most foods hold less power than wheat.  However, there are biological reactors that have higher yields.

Calories = energy.  Do any reactors truly have higher yields?  What are the facts?  They should be in your article.

The article doesn't actually cover bioreactors much.  They have a separate entry.  The reactors seems to be able to use thermal energy to produce food, so they are quite efficient.  I have the paper but I haven't used it for a few years.

Yes, they achieved those numbers with a lot of lighting and multiple trays.  the tables are mostly for single layer growth, unless otherwise stated.
The correlation between lighting and growth seems pretty direct. Energy to energy with the conversion efficiency of photosynthesis.  More light =more food.

Density is important in a space ship or a space station, somewhat less in a surface installation, IMHO, and useless at more than one layer for natural lighting due to shadowing.

[LMT]

All here: https://marspedia.org/Food

The values are high but remain below record yields...

Your table actually states the record yield for wheat, from Bugbee & Salisbury.  That's not "theoretical" or "below record", but the achieved record, with calorie density an order of magnitude beyond potatoes, in your table.

Most foods hold less power than wheat.  However, there are biological reactors that have higher yields.

Calories = energy.  Do any reactors truly have higher yields?  What are the facts?  They should be in your article.

they achieved those numbers with a lot of lighting and multiple trays.  the tables are mostly for single layer growth, unless otherwise stated...

No, their single-layer plots are plain in Fig. 1, with guard areas marked and excluded for accuracy.

The reactors seems to be able to use thermal energy to produce food, so they are quite efficient.  I have the paper but I haven't used it for a few years.

Those aren't the yield facts.  OT now.

[LMT]

A perovskite (methylammonium lead iodide perovskite) thin film solar cell has been validated after 10 months in space:

"A lot of people doubted that these materials could ever be strong enough to deal with the harsh environment of space," McMillon-Brown said. "Not only do they survive, but in some ways, they thrived. I love thinking of the applications of our research and that we're going to be able to meet the power needs of missions that are not feasible with current solar technologies."

This result would seem to open the door for commercial space applications of roll-to-roll printed perovskite PV.

With perovskite thin films rated at 10-30 kW/kg, and this particular perovskite offering over 20% conversion efficiency (Hoye et al. 2020), the prospective numbers for a space-rated R2R printed perovskite PV system are looking very good.

Refs.

Li, Y., Hoye, R.L., Gao, H.H., Yan, L., Zhang, X., Zhou, Y., MacManus-Driscoll, J.L. and Gan, J., 2020. Over 20% efficiency in methylammonium lead iodide perovskite solar cells with enhanced stability via "in situ solidification" of the TiO2 compact layer. ACS applied materials & interfaces, 12(6), pp.7135-7143.
 

[Twark_Main]

The reactors seems to be able to use thermal energy to produce food, so they are quite efficient.

Holy thermodynamics, Batman!!

Obviously a biological system can't exceed the efficiency of a Carnot engine, so presumably you're talking about some temperature difference between hot and cold. Or are they actually claiming to turn Brownian motion into usable energy?

Can we see the paper?

[Lampyridae]

Nature article just dropped:

Assessment of the technological viability of photoelectrochemical devices for oxygen and fuel production on Moon and Mars

https://www.nature.com/articles/s41467-023-38676-2