Heart of Glass

Issue 54 Apr / May 2010

Dr. Russell Binions is currently working as a Royal Society, Dorothy Hodgkin, Research Fellow in the Chemistry Department at University College London, researching techniques for production of and the energy savings potential of thermochromic glass. Henrietta Lynch investigates.

Thermochromic thin films are a new development in smart glass technology that is currently receiving considerable attention because of the potential it has to reduce energy use in buildings, particularly those located in warmer climates.

Thermochromic glass is a new innovation that functions to control solar gain entering a building whilst optimising daylight transmission. The glass works due to a thin surface coating of vanadium dioxide, combined with gold nano-particles that reflect certain parts of the electro-magnetic spectrum away, and absorb others thus controlling thermal penetration into a building through the glass.

According to Binions: “Theoretically thermochromic glazing has the potential to reduce energy consumption in buildings by allowing visible light in for day-lighting whilst reducing solar gain during the cooling season, and allowing useful solar gain in during the heating season.”
The thin film of vanadium dioxide and gold particles that is deposited on the surface of the glass, act as an intelligent window coating. Significant changes in the electrical conductivity and optical properties of the coating are apparent depending on the temperature of the glass. This is different from current ‘static’ approaches to smart glazing such as heat mirror glass, absorbing or low ‘e’ glass where their optical properties are fixed. Thermochromic glass reacts and changes specifically to different parts of the solar spectrum throughout the year. Not only does this glass change its solar gain properties but it also changes its colour in relation to temperature of the glass surface, thus the researchers often refer to it as ‘chameleon’ glass, since it reacts in a similar way to the once fashionable t-shirts that changed colour as a reaction to body heat and external temperature.

Computer test simulations modelled using EnergyPlus software which was developed by the Lawrence Berkeley National Laboratory and the US Department of Energy, suggest that such thermochromic coatings applied to glass are capable of providing an additional energy saving benefit above and beyond those of traditional glass types, especially when used in warmer climates. Thus they have the potential to help reduce the large energy loads needed for air-conditioning.

Thermochromic glass technology is currently still in development and further research is required to produce final products. It does however have the potential to be a real market product within the foreseeable future and to be one that can work to reduce energy use.

The current research that has been undertaken has been supported by the Royal Society, the EPSRC (Engineering and Physical Sciences Research Council) in the UK and the European Union project TERMOGLAZE. The glass manufacturer Pilkington – NSG also provided glass substrates and commercial glass for the experiments.

Contact - Dr. Russell Binions, M.Sci (Hons) CSci CChem, MRSC AFHEA – Royal Society Dorothy Hodgkin Fellow, Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London WC1H 0AJ - r.binions@ucl.ac.uk