Good Thinking

Water-filled windows could both heat and cool buildings

Water-filled windows could both heat and cool buildings
The WFG technology is being tested on prototype buildings located in Taiwan (pictured) and Hungary
The WFG technology is being tested on prototype buildings located in Taiwan (pictured) and Hungary
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The university is presently working on commercializing the technology
The university is presently working on commercializing the technology
The WFG technology is being tested on prototype buildings located in Taiwan (pictured) and Hungary
The WFG technology is being tested on prototype buildings located in Taiwan (pictured) and Hungary

When it comes to keeping buildings energy efficient, windows certainly pose a challenge. It was with this quandary in mind that a British scientist has created a new type of window – one that's filled with water.

There are two main problems with conventional windows. For one thing, most of them allow heat to escape during cold weather, causing the building's furnace to run more frequently. For another, they allow sunlight to stream in during hot weather, creating heat that causes the air conditioning to kick in.

Dr. Matyas Gutai, a lecturer in architecture at Loughborough University, believes that his "water-filled glass" (WFG) windows may address these limitations.

Each window contains a vertical sheet of water, sealed between two sheets of glass. As sunlight passes through the glass, it heats the water, thus keeping the room itself from getting as hot as it would otherwise.

Once it reaches a high enough temperature, that sun-warmed water is pumped out of the window, travelling through pipes in the wall to a storage tank elsewhere in the building. Cooler water is simultaneously pumped into the WFG, to replace that which was pumped out.

When the outdoor temperature drops later on, the stored warm water is pumped back out of the tank and into the pipes, warming the room by radiating heat through the walls. Alternatively, that warm water can also be used in the building's taps, reducing the need to run the water heater.

Although some electricity is required to pump the water back and forth, Gutai claims that his setup still uses substantially less energy than the heating systems and air conditioners that would be required to maintain the same room temperatures under the same conditions.

In fact, based on computer simulations, it is estimated that a WFG-equipped building (utilizing a heat pump within the system), would use up to 72 percent less energy than a similar building equipped with double-glass windows and traditional heating systems. That figure drops to a still-impressive 61 percent for a building with triple-glass windows.

The university is presently working on commercializing the technology
The university is presently working on commercializing the technology

Gutai tells us that in sub-zero winter climates, the water could be kept from freezing by adding an extra sheet of glass with an insulating layer of argon gas sealed inside. He adds that sunlight and heat from the room should also help keep the water from freezing, although if all else failed, an automated system could pump all the water out of the window if temperatures got too low.

Additionally, because the sealed system doesn't allow oxygen or micro-organisms to enter, algae shouldn't grow on the glass. And as an added benefit, unlike other solar-heat-reduction systems, WFG doesn't require external shades such as louvres, nor do the windows need to be tinted. What's more, the water-filled glass is reportedly very good at blocking sound.

"Glass is currently a liability in buildings as it compromises energy consumption, thermal comfort, acoustics and other aspects," says Gutai. "WFG changes this paradigm and turns glass into an opportunity for sustainable construction. It shows us that thinking holistically about buildings and building components leads to a more efficient and sustainable built environment."

A paper on his latest study – which was conducted in collaboration with Dr. Abolfazl Kheybari of Germany's University of Kaiserslautern – was recently published in the Energy and Buildings Journal.

Source: Loughborough University

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.
Baker Steve
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.
Bob Stuart
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?
Brian M
@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.
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