City University of Hong Kong Department Name



Solar glazing


  Highly glazed buildings have become a world-wide design trend in modern architecture. This nevertheless has given much pressure on the global environmental issues like energy wastage and global warming deterioration. To cope with the sustainability and conservation needs, window glazing has been given revised identities and a wide range of design options. One new concept is the ventilated solar screen window system. The system consists of a reversible window frame holding two glazing components: a transparent glazing that provides a weatherproof seal, and an absorptive glazing having top and bottom vent openings for airflow. While the airflow may be natural or mechanically-driven, the window frame can be rotated so that the absorptive glazing is either on the interior (for space heating in winter) or on the exterior (for reducing unwanted-heat in summer).

  We studied the performance of the solar-screen ventilated glazing in Hong Kong. The results showed that for places within the warm climate zone, the window reverse mechanism is not required and the absorptive pane should always set to face outward.

  When the window system is integrated with photovoltaics (PV), an additional function of electricity generation can be achieved. In a working environment, the use of semi-transparent a-Si glazing is deemed better than the one with non-transparent c-Si solar cells. Our results indicate that the innovative natural- ventilated PV double-glazing technology could significantly cut down the air-conditioning power consumption by 28%, as compared to the conventional single absorptive glazing system.



          Working principle of a ventilated solar screen window


    Comparison of daily variation of overall heat transmission through different glazing types

 Comparatively, the heat extraction capability of flowing water is much better than flowing air. The initial investment and operating costs of a water-flow window system is low and the incremental costs can be comparable to solar water-heating installations. Such window system as a hot-water pre-heating device is deemed to have very good application potential in residences, elderly homes, health clubs, sport centers, swimming pools, hotels and any domestic-commercial complex with a stable demand of hot water. Water cleanliness at the window cavity can be maintained by means of a closed-loop buoyant flow of distilled water in association with a heat exchanger.


Energy flow paths at water-flow double-pane window


Related publications :


Keynote speeches:

Chow TT. Sustainable building design with water-flow window, SOLARIS 2012, International Conference on Energy Security, Global Warming and Sustainable Climate, Varanasi, India, 7-9 February 2012.

Chow Tin-tai. New roles of window glazing in achieving sustainable built environment, RSETE 2012, the 2nd International Conference on Remote Sensing, Environment and Transportation Engineering, Nanjing, China, 1-3 June 2012.

Journal articles:

Chow TT, Lin Z, He W, Chan ALS, Fong KF. Use of ventilated solar screen window in warm climate. Applied Thermal Engineering, 26(16), 2006, 1910-1918.

Chow TT, Fong KF, He W, Lin Z, Chan ALS. Performance evaluation of a PV ventilated window applying to office building of Hong Kong, Energy and Buildings, 39(6), 2007, 643-650.

Chow TT, Pei G, Chan LS, Lin Z, Fong KF. A comparative study of PV glazing performance in warm climate. Indoor and Built Environment, 18(1), 2009, 32-40.

Chow Tin-tai, Qiu Zhongzhu, Li Chunying. Potential application of ˇ°see-throughˇ± solar cells in ventilated glazing in Hong Kong. Solar Energy Materials and Solar Cells, 93, 2009, 230-238.

Chow TT, Li C, Lin Z, Fong KF, Chan LS, Pei G. Experimental evaluation of ventilated glazing performance in Hong Kong. International Journal of Energy Research, 33(5), 2009, 526-537.

Chow Tin-tai, Lin Zhang, Fong Kwong-fai, Chan Lok-shun, He Miao-miao. Thermal performance of natural airflow window in subtropical and temperate climate zones ¨C a comparative study. Energy Conversion and Management, 50(8), 2009, 1884-1890.

Chan ALS, Chow TT, Fong KF, Lin Z. Investigation on energy performance of double skin facade in Hong Kong. Energy and Buildings, 41(11), 2009, 1135-1142.

Chow Tin-Tai, Li Chunying, Lin Zhang. Innovative solar windows for cooling demand climate. Solar Energy Materials and Solar Cells, 94(2), 2010, 212-220.

Chow Tin-Tai, Li Chunying, Lin Zhang. Thermal characteristics of water-flow double-pane window. International Journal of Thermal Science, 50(2): 140-148, 2011.

Chow Tin-Tai, Li Chunying, Lin Zhang. The function of solar absorbing window as water-heating device. Building and Environment, 46(4), 2011, 955-960.

Chow Tin-Tai, Li Chunying. Liquid-filled solar glazing design for buoyant water-flow. Building and Environment, 60, 2013, 45-55.

Conference papers:

Chan ALS, Chow TT, Fong KF, Lin Z. Energy Conservation in World-class City Buildings - Application of Window Glazing. The 7th Annual Power Symposium 2008, Power and Energy Section of The IET Hong Kong, June 2008, pp.41-45.

Chow TT, Chan ALS, Lin Z, Fong KF, Pei G. Test of energy performance of photovoltaic/airflow windows in subtropical Hong Kong. Proceedings of SOLARIS 2008, the 4th International Conference on Solar Radiation and Daylighting, Hong Kong SAR, China, December 2008, pp.44-51.

Qiu ZZ, Li P, Chow TT. Simulation of solar power system of building vertical photovoltaic glazing. Proceedings of 2009 Asia-Pacific Power and Energy Engineering Conference, Wuhan, China, March 2009, pp.668-671.

Qiu ZZ, Chow TT, Li P. Performance evaluation of the photovoltaic double-skin facade used in office building. Proceedings of Building Simulation 2009, the 11th IBPSA International Conference, Glasgow, UK, July 2009. (CD-ROM)

Chow Tin-tai, Qiu Zhongzhu, Li Chunying. Performance evaluation of PV ventilated glazing. Proceedings of Building Simulation 2009, the 11th IBPSA International Conference, Glasgow, UK, July 2009. (CD-ROM)

Chow Tin-tai, Li Chunying, Lin Zhang. Warm climate application of innovative water-filled double-pane window. Proceedings of CLIMA 2010, Antalya, Turkey, May 2010. (CD-ROM)

Chow Tin-tai, Li Chunying, Clarke JA. Numerical prediction of water-flow glazing performance with reflective coating. Proceedings of Building Simulation 2011, the 12th IBPSA International Conference, Sydney, Australia, November 2011. (CD-ROM)

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