New 'smart window' system with unprecedented performance

Sep 21, 2011

A new "smart" window system has the unprecedented ability to inexpensively change from summer to winter modes, darkening to save air conditioning costs on scorching days and returning to crystal clarity in the winter to capture free heat from the sun, scientists are reporting. Their study appears in the journal ACS Nano.

Ho Sun Lim, Jeong Ho Cho, Jooyong Kim and Chang Hwan Lee point out that the drive for has fostered efforts to develop new types of window glass for everything from skylights and windows in houses to conference room walls in offices. "Smart" windows that reflect sunlight away from buildings in summer and switch back to full transparency in winter already are available. But they have many drawbacks, including high cost, rapid deterioration in performance, and that involve potentially . So, the researchers set out to develop a smart window that overcomes these drawbacks.

They discovered that using a polymer, so-called "counterions" and a solvent such as was an inexpensive and less harsh way to make a stable, robust smart window. It has the added advantage of being extremely tunable — quickly and easily switching from 100% opaque to almost completely clear in seconds. "To our knowledge, such extreme optical switching behavior is unprecedented among established smart windows," the authors state. "This type of light control system may provide a new option for saving on heating, cooling and lighting costs through managing the light transmitted into the interior of a house."

Explore further: Thinnest feasible nano-membrane produced

More information: Counterion-Induced Reversibly Switchable Transparency in Smart Windows, ACS Nano, Article ASAP. DOI: 10.1021/nn202328y

Abstract
Smart windows that can reversibly alternate between extreme optical characteristics via clicking counteranions of different hydration energies were developed on glass substrates through the facile spray-casting of poly[2-(methacryloyloxy)ethyltrimethylammonium chloride-co-3-(trimethoxysilyl)propyl methacrylate]. The optical transmittance was either 90.9% or 0% over the whole spectral range when alternately immersed in solutions containing thiocyanate (SCN–) or bis(trifluoromethane)sulfonimide (TFSI–) ions, respectively. The extreme optical transitions were attributed to formation of microporous structures via the molecular aggregation of polyelectrolyte chains bearing TFSI– ions in methanol. Because the smart windows were either highly transparent toward or completely blocking of incident light upon direct counterion exchange, this kind of nanotechnology may provide a new platform for efficiently conserving on energy usage in the interior of buildings.

Related Stories

Smart Windows: Energy Efficiency with a View

Jan 25, 2010

(PhysOrg.com) -- Buildings consume 40 percent of our nation's energy. NREL is testing and researching electrochromic windows that could knock that back significantly.

Tunable Windows To Keep Office Secrets

Dec 13, 2004

Secrets that zip across offices through wireless computing networks all too easily also zip through office windows into the hands of competitors – now researchers at the University of Warwick have devised a method of producing ...

Opening a new window on daylight

Jul 31, 2009

A new approach to windows that could let in more light and cut indoor lighting needs by up to 99% in buildings in Tropical regions without losing the cooling effect of shades. Details are reported in the International Jo ...

Recommended for you

Thinnest feasible nano-membrane produced

22 hours ago

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Apr 17, 2014

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 0

More news stories

'Exotic' material is like a switch when super thin

(Phys.org) —Ever-shrinking electronic devices could get down to atomic dimensions with the help of transition metal oxides, a class of materials that seems to have it all: superconductivity, magnetoresistance ...

Innovative strategy to facilitate organ repair

A significant breakthrough could revolutionize surgical practice and regenerative medicine. A team led by Ludwik Leibler from the Laboratoire Matière Molle et Chimie (CNRS/ESPCI Paris Tech) and Didier Letourneur ...

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Continents may be a key feature of Super-Earths

Huge Earth-like planets that have both continents and oceans may be better at harboring extraterrestrial life than those that are water-only worlds. A new study gives hope for the possibility that many super-Earth ...

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...