Laser cooling of Earth's climate

[benswitala]

Hi,

I am worried about climate change. I want to cool the earth. Would it work to build solar panels to provide shade, and then to blast the captured light energy out into space via lasers? I think only certain frequencies will go through the ozone.

Could solar powered lasers help cool the earth?

Thanks
Ben

 

[Vanadium 50]

Some homework for you:

How much heat do you want to send off per unit time?
What is the largest laser? How much does it cost?
How many lasers do you need? How much will that cost?
Is this the most cost-effective alternative?

 

[berkeman]

Welcome to PF.

I am worried about climate change. I want to cool the earth. Would it work to build solar panels to provide shade, and then to blast the captured light energy out into space via lasers? I think only certain frequencies will go through the ozone.

Could solar powered lasers help cool the earth?

If your goal is to cool the Earth by returning solar insolation energy to space, the most efficient way to do that is with mirrors (or at least white things that reflect a lot of the insolation energy).

When you work through the efficiency numbers of your proposal, you will be able to send at most a few percent of the insolation energy back to space, compared to close to 100% with mirrors (for the parts of the Earth that you cover with mirrors). Good solar panels are maybe ~20% efficient, and good lasers are even less efficient. The lost energy goes into (Quiz Question -- What?).

 

[benswitala]

Let me see. I figure solar panels are about twenty percent efficient. Lasers are about fifty percent efficient. So the system would "reflect" about ten percent of the incoming energy of the sun per unit area (assuming the laser doesn't take up any area).

From YouTube I heard that the imbalance due to global warming is currently only about a tenth of a percent per unit area per unit energy per unit time. So the laser system is at ten percent. We need to get to a tenth of a percent. Based on these things, I would say one square meter of my solar-panel/laser system will account for the excess heat of about a hundred square meters.

The surface area of the earth in square meters is about 500 trillion. So we'd need about 5 trillion square meters of my system to cool the Earth. According to Quora, a square meter of solar panel costs $75. So 5 trillion times that will be $375 trillion dollars.

At this point, it seems ridiculous to continue, but solving global warming is worth it at any price.

So, let's continue. I can get a 60 kW laser from the Navy from $100 million. Each square meter of solar panel is about 1 kW. Short answer, the lasers cost about 8 million trillion dollars.

This is not cost effective. Oh well. Thanks for reading.

 

[berkeman]

Lasers are about fifty percent efficient.

No. You need to show me that laser.

https://perg.phys.ksu.edu/vqm/laserweb/ch-7/F7s0p11.htm

With the exception of diode lasers: https://www.laserfocusworld.com/las...gives-highpower-diode-lasers-new-capabilities

At this point, it seems ridiculous to continue

Correct. Mirrors are much, much more efficient in accomplishing your goal, and orders of magnitude less expensive.

This is not cost effective. Oh well. Thanks for reading.

Good conclusion. It s good to keep brainstorming new ideas -- that's what many of us do at our jobs and in our personal endeavors. It's good to always do a "reality check" or "existence proof" or "non-existence proof" early in that brainstorming, to help to limit the time we spend going down non-fruitful paths. That gives us more time to go down the fruitful paths...

Keep on learning, and keep brainstorming.

 

[Jarvis323]

There are proposals to cool the planet by reflecting sunlight, based on "stratospheric aerosol injection, marine cloud brightening and cirrus cloud thinning".

https://www.cnbc.com/2022/10/13/wha...g-sunlight-reflection-risks-and-benefits.html

 

[johnbbahm]

Warming the planet has some risks, and it could be argued if those risks are major or minor,
but cooling the planet has some very real major risks associated with it.
There may or may not be a warming tipping point, but there is almost certainty a cooling tipping point.
The ice core records show we are near the top of an inter glacial warm cycle, and the cold periods are much more common than the warm periods.
ice core records