New thermal coating may help to improve floating habitats in Venus.

[AngelLestat]

Ok, the news is just about a new thermal coating that helps to building here on earth to reflect all sun radiating heat and dump inside heat due to radiation (which can not be absorbed by the atmospehre) to the space, using the space lack of heat as a heatsink.

Long time ago, I was stumbling with ways to improve the efficiency of a Venus floating habitat, to see if it may become at some point in the future into a sustainable economy.

The main issues was:

1- How to get water without spent much energy.

2- Depending habitat height (55km, 52km, 48km), how to deal with heat or the extra amount of lifting gas needed.

The water issue is hard to solve, small habitats would not have any problem, but if you want to produce things in a cheap way you always need water and sulfure acid as resource, sulfure acid is not a big problem there, but water it is.

The second issue depends on the habitat size, in the a relation between the surface envelope material needed vs the lifting gas volume needed.

The envelope is more expensive, but this only apply if the habitat is small.

You can see the ratio of volume vs surface.

For a small outpost:

33-1

Small city:

330-1

Big City:

3300-1

So to avoid lifting gas in a big city, you need to lower height, if you lower height the external temperature increase and you can not have passive cooling, you need to spent energy to deal with heat.

I did some graph about this before to see if there was a way deal with this problem in a efficient way.

http://forum.kerbalspaceprogram.com/threads/71519-Cloud-cities?p=1013460&viewfull=1#post1013460

http://forum.kerbalspaceprogram.com/threads/71519-Cloud-cities?p=1033925&viewfull=1#post1033925

But now this news tech may help a bit to deal with this.

http://news.stanford.edu/news/2014/november/radiative-cooling-mirror-112614.html

Also if you have a lot of these habitats in venus, you are helping to cool the atmosphere.

What are your thoghts? It may help? Maybe with some tweaks in the metamaterial to cross the different components from the venus atmosphere.

[rtxoff]

Very interesting technology also if deployed on sufficiently large scale it could significantly help to counter global warming by reducing/eliminating the need for air conditioning and reflecting sun rays before they have the chance to heat anything.

[AngelLestat]

If is deployed to "global scale" yes. It can counter global warming until certain point.

But I would love to read more details about how this technology really works from somebody with good thermodynamics knowledge, because I have some doubts.

There is an improving efficiency in radiate to the space or to the atmosphere from the radiation point of view? From what I understand if we use the formule P (watts)=emmisivity*constant*area(T^4 - Tc^4)

Then, if the source temperature is a lot higher than the destination body, then you have a good heat transfer efficiency.

In this case is the building temperature to the space temperature (3 kelvins).

And if this surface is good to radiate the heat in these frequencys, then is bad to absorb in different frequencies. So it reflects the heat radiated from other black bodies?

Yeah, I have the feeling that I am way wrong.

[Ralathon]

So they've essentially build a reverse greenhouse? Reflective in visible while transparent to IR instead of vica versa.

That's pretty cool, although I wonder how they'll implement it in buildings. You'd have to coat the entire sun facing side with the stuff, and the effect would never allow you to cool the building to temperatures lower than the ambient air. I have a hard time seeing that as a cost efficient method.

[Coldfinger008]

Well, how much Hafnium do we got?