NIST Industrial Impact

Company: SAGE Electrochromics, Inc., Faribault, Minn.
Business: Electrochromic materials and devices
Number of Employees: 12

Company: 3M Co. St. Paul, Minn.
Business: Materials technologies
Number of Employees: 70,000

Ephemeral in appearance but potentially monumental in impact, a stack of ceramic films less than 1/50th the thickness of a human hair may control how the world looks in the 21st century, as well as how much living in it costs. Developed by a New Jersey startup with a mere dozen employees, the new technology--a pacesetter in a research field that has attracted hundreds of patents in recent years--will, at the very least, help redefine the concept of a window.

At the push of a button, this innovative "smart window" glazing rapidly changes the transmission of light, heat, and near-infrared radiation through the window, reducing lighting and air-conditioning costs for homes or offices and--just as important to the folks inside--reducing glare. The concept long has intrigued scientists, especially those looking for the next big advance in energy efficiency; soon, consumers finally may be able to get it.

Thanks in large part to early support from NIST's Advanced Technology Program (ATP), SAGE Electrochromics, Inc., was able to join forces with an academic materials research center and a large corporation known for its processing expertise to develop safe, cost-effective materials and processes for making electrochromic (EC) windows. The nation could reap substantial benefits because:

• EC glass prices are expected to drop eventually to $10 per square foot wholesale, with the retail buyer's investment beyond conventional glass prices recoverable in just three years.
• Smart windows will dramatically reduce energy use in buildings by 30 to 40 percent or more in some situations), potentially saving the nation billions of dollars annually.
• Prototype windows performed well in independent tests, and retail sales are expected by the year 2001, with a projected market eventually exceeding $4 billion.

"SAGE's smart windows could usher in the next generation of architectural windows," says Russell Huffer, president and chief executive officer of Apogee Enterprises, Inc., a large Minnesota company that teamed up with SAGE in the scale-up and commercialization process. Apogee subsidiaries make window glass and coatings. Apogee officials say they chose SAGE's technology largely because it outperformed the other smart window technologies.

This assessment confirms the success of a project that, by bringing together the right collaborators to turn a great idea into a practical and economically valuable tool, exemplifies the purpose of the ATP program. SAGE started out with just the idea. Within several years of its 1990 founding by John Van Dine, a chemical engineer and solar energy expert, SAGE had patented and demonstrated the feasibility of its ceramic thin-film EC approach and basic processing method. But it was not clear why the EC system performed so well, and the largest device possible at the time was a 2-inch-square sample.

After SAGE's first ATP proposal was rejected, the company found partners. The 3M Co. also was interested in thin films, but for plastic substrates. With 3M contributing expertise in modules and coatings processing, the two companies joined forces to win a three-year ATP award to develop practical EC technologies for both glass and plastic. At that time, commercial EC devices had been made only on small pieces of glass, such as car mirrors. The Center for Ceramic Research at Rutgers University, a subcontractor, became a small shareholder in SAGE.

In the ATP project, which ended in 1997, the researchers designed and deposited EC materials in a way that balanced electrical, optical, and ionic properties. The result was a large-area glazing that regulates the transmission of light much like an integrated circuit regulates the flow of electrons. They also eliminated hazardous and expensive materials, switched to a lower cost processing method, and made several 1 x 1-foot demonstration windows. 3M now is developing plastic EC computer screens to enhance user comfort; SAGE is using follow-on grants from other sources and partnerships to commercialize windows for homes, offices, and transportation applications.

The SAGE technology consists of five layers of electro-optical thin films, deposited on glass in a proprietary process and fired at high temperature. The glass is mounted inside a conventional window frame and can be operated by remote control, rheostat, or the building's energy management system. When a switch is adjusted, a voltage is applied across the film, causing lithium ions to move from one layer to another, similar to what occurs in a battery. This reduces or increases the window tint, depending on the polarity of the voltage. The speed and optical range of the tinting, as well as the window colors, can be customized.

SAGE's prototype windows are robust, durable, and maintain a contrast ratio that meets Department of Energy (DOE) guidelines for energy-conserving windows, according to tests performed by DOE's National Renewable Energy Laboratory. The tests demonstrated that the windows are capable of tens of thousands of tint changes without degrading--equivalent to more than 15 years of harsh sunlight, enough for commercial warranties.

According to experts, EC window cost estimates range from roughly $10 to $100 per square foot. SAGE predicts that its windows will be sold initially for $40 per square foot wholesale, meeting a small market need for residential skylights and windows. Volume production will reduce the cost to $16 per square foot, enabling sales of vertical EC office windows. SAGE predicts that further design and yield improvements eventually will cut the wholesale price to $10 per square foot, low enough to capture almost 25 percent of the market for tinted and coated glass.

EC windows could save 30 to 40 percent of the energy used in some office buildings in hot climates, according to energy simulations performed by DOE's Lawrence Berkeley National Laboratory (LBNL). Although calculations of potential cost savings are highly complex and depend on market penetration and many other variables, one 1993 LBNL study estimated that the use of the latest energy-efficient windows in normal replacement and new construction in the residential sector alone could save 0.6 quads (energy units) annually by the year 2012, equivalent to roughly $5 billion.

Other studies project even greater benefits from EC technologies--a 70 percent savings on lighting, heating, and cooling costs, or $11.5 billion to $22.5 billion per year worldwide, according to a recent report by SRI Consulting. In any case, electrochromics promise to be "the next major advance in energy-efficient window technology," says Stephen Selkowitz, head of LBNL's Building Technologies program.

SAGE envisions many additional applications ranging from windows in aircraft and trains to highway signs and stadium scoreboards. Military applications could include night vision goggles and sensors for smart missiles.

May 1999