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Comment by bgroat | Hacker News Reader

Can you expand on this?

I get that to store a calorie in a potato I need to supply a calorie of energy from somewhere else.

But why is fusion power required instead of better UV lamps in my vertical farm? (Assuming I had enough electricity to run them)

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What powers the UV lamps?

Sun + water is cheap and plentiful. Small scale farms can sell potatoes at $0.50/lb or less. Amish farms with oxen can go a little less.

Capital and operational costs for vertical farms don’t seem to make sense, unless there’s some disaster in the Colorado watershed or a trade war that makes hothouse winter produce a viable business again.

This is totally unrelated, but I saw people plowing fields with oxen in Cuba. A scathing indictment of socialism if ever there was one[1]. It's easy to forget at times how large parts of the rest of the world live.

[1] Don't get me wrong, it's a spectrum and some socialism is a very good thing. But not like in Cuba or the old USSR.

>But why is fusion power required instead of better UV lamps in my vertical farm?

Because of the second law of thermodynamics. Your UV lamp is not going to produce light that contains more energy than the electricity you used as input. That energy needs to be produced via solar panels if you want maximum efficiency. If we ignore nuclear or fusion all energy on earth is derived from sunlight.

And geothermal.

I think the suggestion is that fusion power here is a stand-in for electricity that is too cheap to meter -- basically free power.

Yes, that's exactly what I mean, sorry for skipping a step in my logic.

The total amount of electricity to power those UV lamps should be on par with what the Sun sends to the potatoes fields. Maybe that's the reason for fusion. It didn't do the math.

Actually no not really. Plants only absorb two wavelengths of light. It's currently more efficient to convert sun into solar power via panels and then to light LEDs supplying only the wavelengths that plants use. Despite the seeming inefficiency here, the fact is that plants are even more inefficient at absorbing light not at the right wavelengths than solar panels.

Could one imagine a material that would absorb solar spectrum and emit the preferred frequencies? Something like a polymer one could stretch over fields to get more from the suns rays.

>> "Actually no not really. Plants only absorb two wavelengths of light. It's currently more efficient to convert sun into solar power via panels and then to light LEDs supplying only the wavelengths that plants use. Despite the seeming inefficiency here, the fact is that plants are even more inefficient at absorbing light not at the right wavelengths than solar panels."

> Could one imagine a material that would absorb solar spectrum and emit the preferred frequencies? Something like a polymer one could stretch over fields to get more from the suns rays.

Would you call that a "solar transmitter"?

https://en.wikipedia.org/wiki/Transmitter :

> Generators of radio waves for heating or industrial purposes, such as microwave ovens or diathermy equipment, are not usually called transmitters, even though they often have similar circuits.

Would "absorption spectroscopy" specialists have insight into whether this is possible without solar cells, energy storage, and UV LEDs? https://en.wikipedia.org/wiki/Absorption_spectroscopy

(edit) The thermal energy from sunlight (from the FREE radiation from the nuclear reaction at the center of our solar system) is also useful to and necessary for plants. There's probably a passive heat pipe / solar panel cooling solution that could harvest such heat for colder seasons and climates.

Also, UV-C is useful for sanitizing (UVGI) but not really for plant growth. https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradia... :

> UVGI can be coupled with a filtration system to sanitize air and water.

Is that necessary or desirable for plants?

https://www.lumigrow.com/learning-center/blogs/the-definitiv... :

> The light that plants predominately use for photosynthesis ranges from 400–700 nm. This range is referred to as Photosynthetically Active Radiation (PAR) and includes red, blue and green wavebands. Photomorphogenesis occurs in a wider range from approximately 260–780 nm and includes UV and far-red radiation.

Photomorphogenesis: https://en.wikipedia.org/wiki/Photomorphogenesis

PAR: Photosynthetically active radiation: https://en.wikipedia.org/wiki/Photosynthetically_active_radi...

Grow light: https://en.wikipedia.org/wiki/Grow_light

Are there bioluminescent e.g. algae which emit PAR and/or UV? Algae can feed off of waste industrial gases.

Bioluminescence > Light production: https://en.wikipedia.org/wiki/Bioluminescence#Light_producti...

Biophoton: https://en.wikipedia.org/wiki/Biophoton

Chemiluminescence: https://en.wikipedia.org/wiki/Chemiluminescence

Electrochemiluminescence: https://en.wikipedia.org/wiki/Electrochemiluminescence

Quantum dot display / "QLED": https://en.wikipedia.org/wiki/Quantum_dot_display

Could be possible? Analyzing the inputs and outputs is useful in natural systems, as well.

Even if artificial lighting and natural lighting were equally efficient you would still have to cover the same number of acres in either solar panels or plants. In other words, the denser your vertical farm the more land it consumes. Clearly vertical farming is meant for some really exotic situations in which you might have access to electricity but are in an environment in which you can't grow the plants you want. That situation would probably be a mars colony or a fallout shelter.

Well, it's more efficient (I forget by which factor). So, if the factor were 2, you would need 1 acre of solar panel for every 2 acre-equivalents of planting space. Since you're okay with going vertical, the acre-equivalent could be much less than an acre. So yeah... electricity being much easier to transport than produce, it would actually make more sense to cover a large part of unpopulated area with solar panels, and then farm in very very small portions of the earth.

From an environmental perspective, this is certainly a 'win'. Reducing the amount of land needed for agriculture is a win to both consumers and the environmentalists and the farmers.

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