geoengineering with sterling engines

[FleshJeb]

I was on the team that construction-staked this: 

The panels are on a part of the quarry that’s been tapped out and remediated. The power generated offsets 100% of their electrical needs for the year (which are substantial). They had to dig their electrical trenches with Primacord (I was there, and the explosions were awesome.) It’s running just fine and has paid for itself and then some in the 12 years since it went online.

So, quit the whining and crying, and keep your fantasies about how the world works to yourselves.

[farmerben]

There are vast amounts of solar and wind energy available where nobody lives, and no crops or trees grow.  Is it possible to use this energy in place for a beneficial result?

[FleshJeb]

2 hours ago, farmerben said:

There are vast amounts of solar and wind energy available where nobody lives, and no crops or trees grow.  Is it possible to use this energy in place for a beneficial result?

https://en.m.wikipedia.org/wiki/Floating_solar#

[FleshJeb]

One of the additional benefits of renewable energy is that it’s viable at multiple scales in ways that nuclear and fossil fuel power are not. (I’m still pro-nuclear, especially the small modular reactors.) A big topic in civil engineering is decentralization of necessary resources like electricity, water, and wastewater. Smaller, more local systems can be controlled by the people that actually use them. You don’t quite get the economies of scale of larger systems, but you get increased accountability and responsiveness. They’re also more resilient in the face of disasters, because fewer people are affected if a community-scale system goes offline, and this makes them easier to help.

I have a lot of real-world examples showing the dangers of over-centralization, but the most stark one is from Dune. Paul is able to take control of the galaxy because he controls the single source of the Spice that enables interstellar travel. This is an example of what’s known historically as a Hydraulic Empire.

 

[Terwin]

It sounds like the 'cooling LEDs' might be a viable option for rejecting heat to space if:

1) do the wavelengths where cooling LEDs work match those wavelengths where the atmosphere is most transparent (otherwise we are not getting any heat out to space)

2) the solar panel efficiency* led cooling efficiency * atmospheric transparency at cooling wavelengths > 50% (otherwise we are generating more heat than we reject with this project)

 

Has anyone looked at those numbers to see if this is even feasible?

[farmerben]

 

 

The CO2 absorption bands are roughly the same as that radiated by the surface of the Earth.  Going hotter or colder could make the radiation escaping to space more efficient.

[AckSed]

36 minutes ago, Terwin said:

Has anyone looked at those numbers to see if this is even feasible?

Bear in mind, all this is speculative, and I couldn't give you hard numbers to save my life. I'm going to do the internet equivalent of pulling books off the shelf and seeing if anything lines up.

The proposed ultra-efficient cooling LEDs and normal IR LEDs use the gallium arsenide/gallium indium phosphide semiconductor as a base, and only that uses electrical energy to generate more light instead of heat: https://en.wikipedia.org/wiki/Light-emitting_diode_physics

Quote

As indirect band gap materials the electrons dissipate energy in the form of heat within the crystalline silicon and germanium diodes, but in gallium arsenide phosphide (GaAsP) and gallium phosphide (GaP) semiconductors, the electrons dissipate energy by emitting photons.

The atmospheric window is in the upper parts of mid-to-long-wave infrared (5500-8000 nanometres (1 micron = 1000 nanometres) ), with smaller windows in 2800 and 1400 nanometres:

Spoiler

Sadly, most IR LEDs produce their light in a band of near-infra-red (880-1000 nanometres), output peaking at 940. I cannot find any reference to LEDs that emit at such low wavelengths either. There are more semiconductors than the ones typically used in LEDs, so maybe there's one that's uniquely suited to this application? But that's for future research. We would like to build this here and now. The ultra-efficient LEDs proposed seem to be towards visible red/nearIR, though I could not see a single reference in the paper to the actual frequency of light emitted so... that's out. Welp.

(Ironically, part of how greenhouse gasses work is by absorbing the radiation coming in or radiating out as it already does, and blocking this IR window.)

...we're not quite done yet. Checking the wiki for Passive Daytime Radiative Cooling:

Quote

Currently the Earth is absorbing ~1 W/m2 more than it is emitting, which leads to an overall warming of the climate. By covering a small fraction of the Earth with thermally emitting materials, the heat flow away from the Earth can be increased, and the net radiative flux can be reduced to zero (or even made negative), thus stabilizing (or cooling) the Earth (...) If only 1%–2% of the Earth’s surface were instead made to radiate at this rate rather than its current average value, the total heat fluxes into and away from the entire Earth would be balanced and warming would cease.

[Munday, Jeremy (2019). "Tackling Climate Change through Radiative Cooling"]

Here's the bottom line: we would need to shade 5,000,000,000,000 square metres, or about half of the Sahara Desert, with this. The cost would be $1.25-2.50 per m2, or $1.25-2.50 trillion. (We don't want to do it all in one area, though, as that could get... unpredictable.)

It works best in desert climates with minimal cloud-cover (you'll note that the window is right where water absorbs it), but temperate climates with urban and industrialised zones also work. That means covering your roof tiles with the coating and reducing your AC bill. It means producing solar panels with radiative cooling films that work better because they're cooler in the middle of the day. It means warehouses that don't require AC. It means no heat islands in cities.

So that's the answer to the OP's question. You don't need solar panels, but you could use the empty spaces of the world to cool the planet. You just need the right materials and several gigatons of money and effort.

[darthgently]

8 minutes ago, AckSed said:

Bear in mind, all this is speculative, and I couldn't give you hard numbers to save my life. I'm going to do the internet equivalent of pulling books off the shelf and seeing if anything lines up.

The proposed ultra-efficient cooling LEDs and normal IR LEDs use the gallium arsenide/gallium indium phosphide semiconductor as a base, and only that uses electrical energy to generate more light instead of heat: https://en.wikipedia.org/wiki/Light-emitting_diode_physics

The atmospheric window is in the upper parts of mid-to-long-wave infrared (5500-8000 nanometres (1 micron = 1000 nanometres) ), with smaller windows in 2800 and 1400 nanometres:

  Reveal hidden contents

Sadly, most IR LEDs produce their light in a band of near-infra-red (880-1000 nanometres), output peaking at 940. I cannot find any reference to LEDs that emit at such low wavelengths either. There are more semiconductors than the ones typically used in LEDs, so maybe there's one that's uniquely suited to this application? But that's for future research. We would like to build this here and now. The ultra-efficient LEDs proposed seem to be towards visible red/nearIR, though I could not see a single reference in the paper to the actual frequency of light emitted so... that's out. Welp.

(Ironically, part of how greenhouse gasses work is by absorbing the radiation coming in or radiating out as it already does, and blocking this IR window.)

...we're not quite done yet. Checking the wiki for Passive Daytime Radiative Cooling:

Here's the bottom line: we would need to shade 5,000,000,000,000 square metres, or about half of the Sahara Desert, with this. The cost would be $1.25-2.50 per m2, or $1.25-2.50 trillion. (We don't want to do it all in one area, though, as that could get... unpredictable.)

It works best in desert climates with minimal cloud-cover (you'll note that the window is right where water absorbs it), but temperate climates with urban and industrialised zones also work. That means covering your roof tiles with the coating and reducing your AC bill. It means producing solar panels with radiative cooling films that work better because they're cooler in the middle of the day. It means warehouses that don't require AC. It means no heat islands in cities.

So that's the answer to the OP's question. You don't need solar panels, but you could use the empty spaces of the world to cool the planet. You just need the right materials and several gigatons of money and effort.

You don't need active LEDs.  The right paint will do an ok job.  In the vid I posted a fairly reputable guy made some himself.  If was tedious, but not beyond garage science tinkerer level.  There is another vid out there where the ideal micro sphere size in the paint is narrowed down experimentally.  Cool stuff!

... Here it is: 

 

 

Edited May 9 by darthgently

[AckSed]

23 hours ago, darthgently said:

You don't need active LEDs.  The right paint will do an ok job.  In the vid I posted a fairly reputable guy made some himself.  If was tedious, but not beyond garage science tinkerer level.  There is another vid out there where the ideal micro sphere size in the paint is narrowed down experimentally.  Cool stuff!

On one hand it is cool stuff. On the other hand I spent the entire day watching his other videos! Shame on you. :p