This article is taken from the May/June issue of Renewable Energy Focus magazine. To register to receive a digital copy click here.
While completely self-sustainable cities is a noble goal for the future, there are many things that can be done today to increase efficient use of resources. Conserving energy and heat is a step in that direction, and one that can be attained globally right now. One company offering this solution is SAGE Electrochromics, Inc.
Now a wholly owned subsidiary of Saint-Gobain (France), SAGE held fast to the sole purpose of developing and commercialising energy efficient glass since 1989. Since Saint-Gobain is well known as one of the foremost glass companies, worldwide, the fact that the company saw more potential in investing in SAGE rather than develop its own energy efficient line is rather remarkable. SAGE headquarters are now based in Minnesota, USA, which is known as the “Silicon Valley” of the window industry.
Dr. Helen Sanders, VP of technical business development says, In the big picture, dynamic solar control, which means the ability to change the heat gain of the glass within any building envelope, is one of the three key façade technologies on the Department of Energy roadmap for energy efficient buildings.
Smart solar solution
In a nutshell, the goal of “smart” solar windows, or “dynamic lighting” is the need to be able to capture heat when needed to and block it at other times, when cooling. Also, the ability to do this automatically, captures energy savings needed to create truly energy efficient buildings.
“The glass we provide gives the user the ability to change the visible light transmission and the heat gain transmission, at the touch of a button. You can partially tint or clear the glass to basically tune the amount of heat and light that comes into any room,” Sanders says. “Because you can always see through the glass, regardless of the transmission, you always maintain that view and connection with the outside.”
SageGlass provides dynamic control that is part of the glass itself. The coatings are put onto the glass using the same method that is used to coat Low-e glass – sputtering. Also, like Low-e coatings it is protected from the environment inside an insulating glass unit. The carbon footprint is always smaller than other solutions. The patented process starts by coating float glass with nano-layers of metal oxides using a sputter deposition system. It's a process similar to that used to make millions of square feet of Low-e glass each year. SageGlass is then fabricated into an insulating glass unit (IGU) with another piece of glass using a stainless steel spacer.
“The difference is that in a static Low-e product there is one visible light transmission and one solar heat gain coefficient for the life of the building, always trading solar light transmission for heat gain with a compromise mid-range visible light transmission of 35% to 40% and a solar heat gain coefficient of 0.25 to 0.35%. It is never right all the time,” Sanders says.
“If there is strong direct sunlight, blinds still need to be closed to control glare and block direct heat. On a cold, gloomy day, not enough heat/light will come in. Of course, when shades are used to keep out the sun's light/heat, lights need to be turned on inside to be able to work. Also, on a gloomy day, the coating will not let in enough solar heat so heating systems need to be turned up higher. Dynamic glass windows allow multiple tuning of multiple types of glass in one panel.”
The control of each window can be individual by pane or groups of panes, and is changed by applying a very low DC voltage (3–4 volts) to the interior coating. SAGE supplies the control system, but according to Sanders, building occupants can interface with the system in many ways: completely automated, based on pre-programmed seasons, building occupancy and type of outside weather-cloudy or sunny. It can be controlled by an internal building automation system, provide standalone automation or be manually controlled.
“Normally, it is some type of mixture of all three. It is very flexible in control. At any time, any specific room may need special consideration. If you are doing a presentation and you need the room darker than if you were just at a desk working, a manual override would solve that specific situation,” she says.
New on the Market
“In terms of what's new, one of the things we are bringing out is the ability to control smaller segments independently within a main pane. This way individual sections can be controlled, such as in a floor-to-ceiling window with a hot glare in only one area. This allows a workspace to use daylight rather than artificial lighting, but hold down glare at the same time, making a comfortable work space and still using less energy,” Sanders says.
“Other newly available options add aesthetic flexibility for architects and building designers with tint coloring options for controllable glass. We fit into any framing system on the market.”
The global market is growing rapidly for SageGlass dynamic windows and will surely see a jump when the newest product is introduced soon. This will have all the capabilities of the current products, but will be completely off-grid powered and wirelessly controlled.