My point above was that it is a system. Nowhere for the liquid to expand to = bad. No antifreeze = bad.
In severe cold, these windows appear to be self-clogging…
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So long as your heat doesn’t go out, I suspect that freezing won’t be THAT much of a problem. After all one side of this window is bordering a heated space, so it isn’t supposed to get THAT cold. I’ve gotten ice on the windows often enough to realize that it will get below freezing, but probably not THAT far below freezing, at least in much of the continental US. The thing that gets me is that while water IS a good way of transferring energy it isn’t all that great at absorbing solar radiation. After all it is transparent. It seems to me that a Trombe wall would would absorb a bunch more heat. And I HAVE seen designs using water barrels as elements in a Trombe wall
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[Minnesota has entered the chat]
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it’ll all work until the day after the warranty expires
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I can just about guarantee that water would freeze in Alberta, Saskatchewan, or Manitoba in January unless steps were taken to prevent it. Any condensation on the inside of our current double-pane windows forms ice dams, and it’s inside the house, on the warm side of a vacuum barrier. Those windows get effing cold when one side of them is -30.
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Can vodka be used instead of water? Asking for a friend. 
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What did we learn in physics class about water when it freezes?
That’s right! It expands.
And when it does, the glass will crack.
So it would be interesting to see how they mitigate this.
I would probably find a liquid that doesn’t expand when it freezes, and that has a much lower freeze point temperature than water in the first place, and continue experimenting from there.
But…
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Yes, when reading all the stuff about how “novel” this solution is, my head went right to, “so, a Trombe wall with some ‘smart’ pigments and a pump?”
It’s interesting, for sure. But I wish that we’d deploy some of the technologies we already know to work at reducing energy load, while improving comfort and passive survivability. 
And, we have way better modeling data for those things than for this. Setting the other three facades as adiabetic…? Certainly makes one wonder.
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I don’t know how practical this is or isn’t, but some of the concerns people are expressing here are not problems that haven’t already been dealt with. Closed water systems have been used for heating and cooling large commercial buildings for probably 100 years. The only difference here is using solar energy from windows as a heat source instead of a boiler. Solar panels have been used in this way for decades. I would think solar panels as windows would be more practical, but who knows. I don’t think there are any massive technological hurdles to these water filled window systems.
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I prefer the window solar panels idea, too.
I think a lot of the concerns raised come from issues with traditional windows, past experiences with water winding up in unplanned places, and concerns about maintenance. I also wondered about the difference in weight, and how the designs would account for that. I’m still trying to get over seeing styrofoam used in the walls of new houses, though. 
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I don’t think “technologically impossible” was on anyone’s list of concerns. The list so far is approximately:
- These are gonna leak sooner or later because all windows do
- When they leak, that water is gonna go very bad places for a house
- That water is gonna freeze in many parts of the world unless you wanna have glycol-green tinted windows
- It’s an enormous amount of complexity (and thus cost and maintenance issues) for what seems like minimal efficiency gain.
Nobody here is questioning that it can be done. Closed loop liquid cooling is everywhere in our world. Possibly in your PC right now, even. They’re questioning this specific implementation.
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No one has ever successfully dealt with water, except temporarily.
Solar panels would be better IMO. I’ll leave the closed loop water system in the foundation block. My current dwelling has one, but it’s not in use now. Last house we lived in had one in active use, it was cool (warm) and all but did take forever to adjust. Plus it kept the house toasty for a long time after the power would go out, these windows would have a decidedly different outcome.
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Except for the part where those water systems are very explicitly insulated from any potential freezing outside temperatures due to the risk for leaks and damage, which simply isn’t possible when the water is literally in your window panes. Even if there’s a layer of vacuum insulation outside of that, this is still a very major difference compared to either in-wall piping +radiators (insulated by the wall, small surface area for heat transfer) or in-floor heating systems (insulated by being embedded in an indoor structure, typically concrete). And of course all that water is heated by a boiler of some sort in winter which keeps it well above freezing, while the heat source here is supposed to be the sun - meaning it needs exposure to freezing outside temperatures even in winter, and adding a boiler would be terribly inefficient as half the heat (if not more) would be dumped outside of your house.
And of course there’s the fact that the water in such systems tends to be gunky and black from corrosion and the like (part of their low maintenance nature is not needing frequent fluid changes), while this needs to be kept pristine unless you want your windows to clog up with dirt.
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A potential compromise solution: window shutters made from translucent solar panels, especially if those can be designed to absorb IR/heat as well (which they no doubt can, though you’d want some sort of cooling for the panels in summer - but outside, at least). You get the option for full exposure if/when you want it, you get solar energy, and you get partial sunlight and heat blockage through the (relatively inert) heat shield being outside of the house.
If the panels were water cooled (which isn’t uncommon for roof mounted solar panels) that would increase their efficiency and allow for heat energy capture through plumbing that coolant into a heat exchanger linked to the building’s central heating - keeping the heated fluid away from the inside of the house (mostly), and optionally vented elsewhere if needed, or even run though some kind of thermal electric generator for a small further efficiency boost. And with these being shutters you’d lose the need for them to look perfectly clear and transparent, making both coolant choice and maintenance a lot easier.
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Yeah I didn’t say people were saying it’s impossible. All I’m saying is that the concerns people are expressing are not, in my opinion, particularly difficult problems to overcome. Regardless, I doubt whether this will prove to be practical or cost effective, so I think we all basically agree. We just maybe have some differences in why we agree.
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The physics of flat pane windows are the fundamental problem. Large, flat, and brittle are characteristics unsuited to holding fluids at any kind of pressure or under expansion. It’s the worst possible form factor for containing liquids. We haven’t even gotten to the bit about uneven flow and dead flow spaces in the rectangular design.
The only way to make that whole thing worse is to use water as the liquid, due to it’s extremely forceful expansion when freezing.
So, from an engineering perspective, it’s not that it’s impossible or even impractical to make this work under ideal conditions, temporarily; it’s that it’s a terrible idea as soon as we consider implementation in less than ideal conditions for more than a year or so, at best.
The frosting on the cake is that there are better technologies to accomplish the stated goal readily available.
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I so thought this was going to say, “the frosting in the windows…”
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