Wednesday, August 25, 2004
Good news from the air-conditioning front
I have posted several times on this blog on how important air-conditioning is to productivity, especially in tropical countries where temperatures can reach highs that make working (at any level of efficiency) pretty darn impossible. The downside, obviously, is whether developing countries can handle the load extensive air-conditioning will place on their power grid, a predicament Shanghai faced as recently as last month. Part of the solution lies in building more energy efficient, green buildings. In that context, researchers at University College in London may have come up with an excellent solution.
A new coating for glass that can keep the heat from the sun out, saving on air-conditioning costs, has been developed by scientists in London. The glass has a microscopic coating that allows glazing to keep heat out of buildings while allowing light to pass through. The key is a thin coating of vanadium dioxide, around the thickness of a human hair, that is placed on normal window glass.
"This coating can actually be used for modifying the properties of the glass," said Ivan Parkin, of the team at University College London that has developed the coating. "When put onto a window, it will let in only a certain fraction of the sunlight. When the window gets hot, it becomes more reflective. But it only becomes more reflective of the heat portion of the sunlight, not in the visible portion."
The UCL team have also found a way to choose at which temperature the glass begins to prevent heat coming in, by putting tungsten into the vanadium dioxide coating. "By controlling the amount of tungsten dopent we introduce, we can change the temperature at which it will reject the heat," Dr Parkin explained. "We can actually tune our system from anywhere between 70 degrees, which is the pure vanadium dioxide switching temperature, all the way down to zero degrees, if we wanted to."
However, currently the amount of glass they can cover at one time is around 10cm square. The scientists are currently in negotiations with companies to look at scaling up the process. Dr Parkin explained there were a number of problems that needed to be overcome to make it a full-scale commercial enterprise. One is that the coating is a yellow colour that makes the window look dirty. The team are currently looking at a way of modifying this."Also there are issues when you scale up the chemistry. Sometimes the chemistry doesn't behave on a three metre-wide piece of glass as it does on a piece 10 centimetres wide," Dr Parkin said.
A new coating for glass that can keep the heat from the sun out, saving on air-conditioning costs, has been developed by scientists in London. The glass has a microscopic coating that allows glazing to keep heat out of buildings while allowing light to pass through. The key is a thin coating of vanadium dioxide, around the thickness of a human hair, that is placed on normal window glass.
"This coating can actually be used for modifying the properties of the glass," said Ivan Parkin, of the team at University College London that has developed the coating. "When put onto a window, it will let in only a certain fraction of the sunlight. When the window gets hot, it becomes more reflective. But it only becomes more reflective of the heat portion of the sunlight, not in the visible portion."
The UCL team have also found a way to choose at which temperature the glass begins to prevent heat coming in, by putting tungsten into the vanadium dioxide coating. "By controlling the amount of tungsten dopent we introduce, we can change the temperature at which it will reject the heat," Dr Parkin explained. "We can actually tune our system from anywhere between 70 degrees, which is the pure vanadium dioxide switching temperature, all the way down to zero degrees, if we wanted to."
However, currently the amount of glass they can cover at one time is around 10cm square. The scientists are currently in negotiations with companies to look at scaling up the process. Dr Parkin explained there were a number of problems that needed to be overcome to make it a full-scale commercial enterprise. One is that the coating is a yellow colour that makes the window look dirty. The team are currently looking at a way of modifying this."Also there are issues when you scale up the chemistry. Sometimes the chemistry doesn't behave on a three metre-wide piece of glass as it does on a piece 10 centimetres wide," Dr Parkin said.
