Solar-powered monster charging stations?

Question

Lets assume we have a super advanced intelligent, possibly magical, Entity that wants to enroll Earth in a fun episode of monster invasion by making a bunch of demons and releasing them on Earth. The details of that is kinda irrelevant except how to "power" the monsters.

To power the monsters, the Entity decides to harness the power of the sun in huge structures that stand tall, breaching the clouds. They store the power they gather and reach out with some sort of arm-tentacle things to connect to the "monsters" to feed and recharge them.

Our rules are simple.

• We will be following the laws of science without any magic. We can imagine more advanced biological engineering or possible biology. We are not sticking to Earth biology or what we know or see in geological record. Just has to be possible.
• Practically or impractically is not an issue. I just want that image in my story. Also those things work as a fail safe since the monsters have no way to keep themselves powered without those stations. Thought if you want to suggest a different way I won't mind. But we gotta put some rules.
• I imagine the stations as huge constructions with heights between 2-30 Kilometer, yes I wrote that correctly.
• The stations are made of repurposed materials stuff like: Stones, rocks, metals, whole buildings, biological materials...etc.
• The tentacle things, just called arms, provide the creatures with food in the form of a goo. Kinda like an MRE. Bet it tastes better though.
• The stations use both the power of the sun as well as laying deep roots in the ground. So. Basically they are gigantic mutated, not really, trees that can produce a nutritious goo to other creatures. I mean trees do it. But not sure if they can create the required nutritious goo.
• The goo provides a full nutritious package to the creatures. Proteins and fibers...etc

Question:

1. Is this possible? What are the expected difficulties?

2. What exact scientific process happens in the station that can create this goo?

Answer 1

1. Towers are space elevators.

2. Towers have wells under them and pump water up.

3. Towers have photosynthesizers on them that convert sunlight and CO2 and water to sugar. The towers pump water up to keep the photosynthesizers watered.

4. The photosynthesizers are maple trees. The goo is maple syrup. But they are bioengineered to drip it from their branches where the monsters suckle. Otherwise regular trees.

5. There are also avocado trees because some of the monsters like guacamole and those monsters need love too.

Answer 2

You asked for science-based, right? Let's do a bit of hard-science here.

• I imagine the stations as huge constructions with heights between 2-30 Kilometer, yes I wrote that correctly.

Is this possible? What are the expected difficulties?

Major difficulty: height and weight of the structure. 2km is achievable with common materials. 30km height? How deep is your pocket?

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Compressive strength - σ - compressive pressure at which a material fails (and usually crumbles). So, what the maximum height on which the base of a column, made from a certain material, fails under its own weight?

$$\sigma = \frac{\rho \cdot (A \cdot h_{max}) \cdot g}{A} = \rho \cdot g \cdot h_{max}$$ $$h_{max} = \frac{\sigma}{\rho \cdot g}$$

• Portland cement aged - $\rho = 1.44\cdot10^3 kg/m^3$, $\sigma = 21\cdot10^6 Pa$, $h_{max} = 1488 m$
• Basalt (trap rock) - $\rho = 2.9\cdot10^3 kg/m^3$, $\sigma = 140\cdot10^6 Pa$, $h_{max} = 4926 m$
• Tasmanian oak - $\rho = 0.7\cdot10^3 kg/m^3$, $\sigma = 70\cdot10^6 Pa$ (PDF warning), $h_{max} = 10204 m$
• Bubinga wood - $\rho = 0.71\cdot10^3 kg/m^3$, $\sigma = 72.4\cdot10^6 Pa$, $h_{max} = 10405 m$ - yes, surprise, some woods may be better choices for tall structures than rock
• Porcelain - $\rho = 2.3\cdot10^3 kg/m^3$, $\sigma = 500\cdot10^6 Pa$, $h_{max} = 22182 m$ - nice white tower you have there, wizard, still a wee short of 30km
• Monocrystalline diamond - $\rho = 3.53\cdot10^3 kg/m^3$, $\sigma = 60\cdot10^9 Pa$, $h_{max} = 1734404m = 1734.4 km$

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Then you have the problem of the soil the structure sits on. I'd look for some numbers were I to have time now, maybe I'll come back to it later, but...

How much would you like recovering your 30km high monocrystalline diamond tower from the Earth's upper mantle?

Answer 3

It's not possible, and scientifically it's silly.

The tallest mountain on earth is about 9000 meters, which is about the limit on earth because of gravity making large structures collapse. You want a structure substantially larger than that. The energy to build such a structure would be orders of magnitude larger than the energy you'd get from the sun- why not just have giant tentacles that feed people with the inbuilt reserves?

Also, the sun doesn't notably increase in intensity as you go up. You're building a massive amount of material to not get more sunlight. If you built the same structure out broad you could get far more.

Dig down instead.

Have the tentacles dig miles down into the earth to sap at the core of the planet. The rich heat of the earth's core can fuel them with heat pumps, and they can process the vast mineral wealth of the earth.

They already have deep roots. Make them deeper, and have them rely on the earth as a power source. An extremely advanced species could likely tap geothermal power much more easily than we could, and gain vast amounts of energy.