One of the main features on a building are its windows – in fact they play a great role in its energy efficiency. Sustainable architecture not only deals with the positioning of walls for catching the most sunlight and heat, but special smart windows can also enhance energy efficiency and save money on lighting, heating or even cooling.
You might have heard about windows that can change their colour but there are actually several different technologies behind it. Some become opaque, others change their colours, which can be triggered by various conditions: a change in the temperature or irradiation, or even artificially – by humans or pre-programmed systems.
The windows can capture the heat to make it warmer inside in cold months, or reflect the heat for cooling purposes in the summer. They can even collect the sun’s energy and turn it into electricity.
Fundamental technologies are based on various physical processes, classed as thermotropics, photocromatics, liquid crystals, suspended particle displays, electrochromics, or reflective hydrides [1].
Thermotropics windows react to heat, while the photocromatics technology is already used in prescription glasses that become tinted in the sunshine [1]. Suspended particle displays and liquid crystal windows work in a similar way, by re-arranging particles and crystals depending on the electricity fed into the panel, either letting the light through or not. [2] [3]. In electrochromic windows a chemical reaction is prompted by a certain level of voltage. [4]
However besides the obvious benefits, there are some disadvantages, too. Some of these technologies are slow, meaning the transition between states could take several minutes. Also, electronic solutions need a constant supply of electricity, which could lower efficiency. [5]
Some examples
A recent example from South Korea is a new type of smart window that can change transparency within seconds, depending on the outside temperature. It is managed by electric currents thanks to the charged particles between the glass sheets, and it is claimed to be cheaper and with a lower health risks than other, already available types. [6]
The company Pleotint offers an ‘interlayer’, which darkens in direct sunlight without any electronic application, and so it’s sustainable on a long term, but ‘colour change’ can take about 20-30 minutes. [7]
SWITCH Materials [8] has developed a smart window photochromic-electrochromic film technology, enabling the tinting of windows in direct sunlight, which can also be induced manually.
SageGlass manufactures electronically tintable glass, available in various colours, which can be controlled manually as well as automatically, too. [9]
Overall
Whatever the technology, such windows can save money on heating, cooling or lighting both at home or in the offices. What’s more, they can also become the blinds of the future.
[1] http://home.howstuffworks.com/home-improvement/construction/green/smart-window1.htm
[2] http://home.howstuffworks.com/home-improvement/construction/green/smart-window2.htm
[3] http://home.howstuffworks.com/home-improvement/construction/green/smart-window3.htm
[4] http://home.howstuffworks.com/home-improvement/construction/green/smart-window4.htm
[5] http://www.ecofriend.com/good-bad-ugly-smart-glass.html
[6] http://www.bbc.co.uk/news/technology-15076773
[7] http://www.pleotint.com/content.asp?id=6&act=a#Q2
