Tag Archives: thermochromic windows

‘Smart’ windows from Australia

My obsession with smart windows has been lying dormant until now. This February 25, 2018 RMIT University (Australia) press release on EurekAlert has reawkened it,

Researchers from RMIT University in Melbourne Australia have developed a new ultra-thin coating that responds to heat and cold, opening the door to “smart windows”.

The self-modifying coating, which is a thousand times thinner than a human hair, works by automatically letting in more heat when it’s cold and blocking the sun’s rays when it’s hot.

Smart windows have the ability to naturally regulate temperatures inside a building, leading to major environmental benefits and significant financial savings.

Lead investigator Associate Professor Madhu Bhaskaran said the breakthrough will help meet future energy needs and create temperature-responsive buildings.

“We are making it possible to manufacture smart windows that block heat during summer and retain heat inside when the weather cools,” Bhaskaran said.

“We lose most of our energy in buildings through windows. This makes maintaining buildings at a certain temperature a very wasteful and unavoidable process.

“Our technology will potentially cut the rising costs of air-conditioning and heating, as well as dramatically reduce the carbon footprint of buildings of all sizes.

“Solutions to our energy crisis do not come only from using renewables; smarter technology that eliminates energy waste is absolutely vital.”

Smart glass windows are about 70 per cent more energy efficient during summer and 45 per cent more efficient in the winter compared to standard dual-pane glass.

New York’s Empire State Building reported energy savings of US$2.4 million and cut carbon emissions by 4,000 metric tonnes after installing smart glass windows. This was using a less effective form of technology.

“The Empire State Building used glass that still required some energy to operate,” Bhaskaran said. “Our coating doesn’t require energy and responds directly to changes in temperature.”

Co-researcher and PhD student Mohammad Taha said that while the coating reacts to temperature it can also be overridden with a simple switch.

“This switch is similar to a dimmer and can be used to control the level of transparency on the window and therefore the intensity of lighting in a room,” Taha said. “This means users have total freedom to operate the smart windows on-demand.”

Windows aren’t the only clear winners when it comes to the new coating. The technology can also be used to control non-harmful radiation that can penetrate plastics and fabrics. This could be applied to medical imaging and security scans.

Bhaskaran said that the team was looking to roll the technology out as soon as possible.

“The materials and technology are readily scalable to large area surfaces, with the underlying technology filed as a patent in Australia and the US,” she said.

The research has been carried out at RMIT University’s state-of-the-art Micro Nano Research Facility with colleagues at the University of Adelaide and supported by the Australian Research Council.

How the coating works

The self-regulating coating is created using a material called vanadium dioxide. The coating is 50-150 nanometres in thickness.

At 67 degrees Celsius, vanadium dioxide transforms from being an insulator into a metal, allowing the coating to turn into a versatile optoelectronic material controlled by and sensitive to light.

The coating stays transparent and clear to the human eye but goes opaque to infra-red solar radiation, which humans cannot see and is what causes sun-induced heating.

Until now, it has been impossible to use vanadium dioxide on surfaces of various sizes because the placement of the coating requires the creation of specialised layers, or platforms.

The RMIT researchers have developed a way to create and deposit the ultra-thin coating without the need for these special platforms – meaning it can be directly applied to surfaces like glass windows.

Here’s a link to and a citation for the paper,

Insulator–metal transition in substrate-independent VO2 thin film for phase-change device by Mohammad Taha, Sumeet Walia, Taimur Ahmed, Daniel Headland, Withawat Withayachumnankul, Sharath Sriram, & Madhu Bhaskaran. Scientific Reportsvolume 7, Article number: 17899 (2017) doi:10.1038/s41598-017-17937-3 Published online: 20 December 2017

This paper is open access.

For anyone interested in more ‘smart’ windows, you can try that search term or ‘electrochromic’, ‘photochromic’, and ‘thermochromic’ , as well.

Liquid solar blocker from Ontario’s Hy-Power Nano

Hy-Power Nano, mentioned in my Aug. 15, 2012 posting, has announced its first nanotechnology-enabled product and it’s a coating product for windows. From the Sept. 3, 2012 news item by Will Soutter item on Azonano,

Hy-Power Nano, the subsidiary of South Ontario-based [Canada] Hy-Power Coatings, engaged in developing nanocoating products characterized by thermal insulation and a solar blocking capability has introduced its first product labeled the Hy-Power Clear Liquid Solar Blocker.

The launch of the solar blocker represents a significant milestone in the company’s endeavors towards the development of nanotechnology-based coating products. The product was demonstrated in Mississauga at the International Conference Centre to a group of customers. The product is the output of two-and-a-half years of labor initiated after Hy-Power Nano President and CEO, Joseph Grzyb, envisaged the potential of leveraging their 46 years of expertise in industrial coating in combination with nanotechnology.

Hy-Power Nano’s Aug. 31, 2012 product announcement offers this comment from the company’s president, Joseph Grzyb,

“While we all love sunlight, ultraviolet (UV) rays can be damaging and infrared (IR) rays are a source of energy costs,” says Joseph Grzyb, President and CEO of Hy-Power Nano. “Our Clear Liquid Solar Blocker is so clear you can’t see it on glass, yet it blocks 99.99 per cent of UV and 40 per cent of infrared rays. Since the product is liquid-based, it can be applied on a variety of glass surfaces and geometries.”

“There are many applications for this product. For example, for retailers, that means products in windows won’t fade from sunlight while allowing customers a completely unobstructed view of the goods in the window. Skylights coated with our product allow people to enjoy the comfort and natural light without any negative impacts. There are actually quite a range of needs addressed by this product,” adds Grzyb.

There’s a lot of research interest in windows these days and it’s not just in Canada. This Aug. 27, 2012 Nanowerk Spotlight essay by Michael Berger offers an overview of some of the latest work,

Buildings and other man-made structures consume as much as 30-40% of the primary energy in the world, mainly for heating, cooling, ventilation, and lighting. In particular, air conditioners are responsible for a large proportion of the energy usage in the US: 13% in 2006 and 10% in 2020 (projected) of the total primary energy. Air conditioning in China is 40-60% of a building’s energy consumption (the exact figure depends on the area of the building), and overall, accounts for 30% of the total primary energy available. These figures will grow very rapidly with urbanization development.

“Smart window” is a term that refers to a glass window that allows intelligent control of the amount of light and heat passing though. This control is made possible by an external stimulus such as electrical field (electrochromic), temperature (thermochromic), ultraviolet irradiation (photochromic) and reductive or oxidizing gases (gasochromic). These technologies save energy, address CO2 concerns, improve comfort levels, and have economic benefits.

One of these days I’d like to see a study or two about the occupational health and safety issues for people who produce and apply coatings such as this one from Hy-Power.

Smart wall or smart window? Ravenbrick brings one to the market in 2013

Alex Davies posted a July 10, 2012 article on the Treehugger website about a smart window/wall system from RavenBrick. From the article (Note: I have removed links),

The RavenWindow from RavenBrick changes its tint in response to temperature, so it blocks sunlight entering a building after a set temperature has been reached. Combine it with a layer of insulating materials that store heat during the day and release it at night, and you’ve got the RavenSkin Smart Wall System.

Here’s a little more about the RavenWindow from the company’s Project Portfolio page,

RavenBrick has installed their RavenWindow product at the [US] Department of Energy’s National Renewable Energy Lab in Golden Colorado. This LEED platinum building was designed to use the most energy efficient products available. This installation, on the executive floor, is the first of three installations that will be done at NREL.

RavenWindow at NREL in the clear state viewed from the inside (from the RavenBrick website)


RavenWindow at NREL in the tinted state viewed from the inside (from the RavenBrick website)

Then, here is the view of the tinted windows from the outside,

RavenWindow at NREL in the tinted state viewed from outside (from the RavenBrick website)

They do give a fairly simple explanation of the technology, from the company’s The Technology page,

RavenBrick’s smart window systems are changing the rules of energy efficent design by doing something that previous generations of building materials simply couldn’t: letting the sun’s heat into the building when you need it, and keeping it out when you don’t.

Our thermochromic filters utilize advances in nanotechnology, pioneered and patented by RavenBrick, to transition from a transparent to a reflective state in response to changes in the outside temperature. This transition allows a building to use the sun as a source of free heat on cold days and block solar heat effectively on hot days.

RavenBrick’s technology diagram (from the RavenBrick website)

Davies’ Treehugger article offers some figures regarding savings (and another illustration),

The RavenSkin Smart Wall System promises to cut energy bills by as much as 30 percent, so it’s sure to offset the costs of installation (not listed on the RavenBrick website). The “infrared power system” doesn’t involve electricity, moving parts or wires, so it’s low maintenance, [sic]

I would have liked a little more detail. How did they derive the savings number, i.e.,  “by as much as 30%”? Also, is there any data from the US Dept. of Energy? At any rate, this product is due to reach the marketplace sometime in 2013.

I last mentioned RavenBrick and their windows in my Aug. 5, 2009 posting. In my Sept. 7, 2011 posting about the US Dept. of Energy, I focussed on smart window research being done at their Lawrence Berkeley National Laboratory (Berkeley Lab).