I assume calculations have been made to allow for the weight of the water - I wonder if retrofitting existing windows would be possible (between water weight and having to install all those pipes and pumps)

I'm assuming all's great until one of those panes cracks.

The possibility of a broken window would have to be provided for - pressure sensors and fast closing valves would do it. What really concerns me is the ability to see through the window. One of the reasons we put windows in houses is so we can see the environment outside the house.

If it's made of 3d clear plastic it won't break as it will still have electric conduction and heat/cool here. Heck I could even see this for cpu cooling in the future if they even make a cpu or gpu chip out of plastic glass.

Despite what the article says, I'd still consider algae a serious issue.

He may be a scientist, but he obviously has never worked with Central Heating systems. Over time, they get full of crap!
Water reacts with the components of the system, and contamination gradually builds up. The windows would become less and less effective as windows. As for reducing heating within the building, glass with reflective coatings already does that, and in any-case, any light that passes through the window, will still get converted to heat. In addition, in normal habitable dwellings, glass is a small % of the total wall area, so the costs for manufacturing, connecting, and maintaining a glass radiator system, would be unlikely to be cost effective.

Certain microscopic material could be introduced to the water to accomplish many benefits. This concept has a future with assisting energy conservation.

Water is quite clear to visible light. Which wavelengths does it absorb? Does this require better glass to resist the pressure at the bottom of a tall section?

@Baker Steve:
Yes - There is also the possibility of anaerobic organisms, anything that clouded the water would defeat the whole purpose of the window. Difficult to imagine that micro organism would not get into the system one way or another. There is also the difficulty if you want opening windows or doors.

Yeah, "sealed systems" still grow algae all the time.