A team of scientists from the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is working on a new initiative to drastically reduce the amount of energy consumed by buildings and windows across the country, and they are working on a polymer heat-reflective coating that can be used to paint buildings.
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The background to this initiative lies in the fact that window performance consumes about 10% of all energy used by buildings across the nation, making building owners to pay up about $50 billion every year. Yet retrofitting or replacing windows for energy efficiency is very costly and price prohibitive.
Berkeley Lab scientist Raymond Weitekamp disclosed that home owners pay very large sums of money to hire contractors to either install or retrofit windows, but this problem could be solved where homeowners could walk into any local store to buy the coating and paint it themselves.
“The coating will selectively reflect the infrared solar energy back to the sky while allowing visible light to pass through, which will drastically improve the energy efficiency of windows, particularly in warm climates and southern climates, where a significant fraction of energy usage goes to air conditioning,” Weitekamp said.
With the Advanced Research Projects Agency-Energy (ARPA-E), the Department of Energy is funding the research by the Berkeley Lab scientists led by Garret Miyake of the University of Colorado, Boulder, and Caltech and Materia Inc.
It is true that retrofit window films that have spectral selectivity can now be purchased in the market, but expensive contractors would be required to install them, something many house-owners may not afford. With a low-cost alternative, an annual energy saving of 35 billion kilowatt-hours would be realized – reducing carbon-dioxide emissions by 24 kilograms per year, the equivalent of taking 5 million cars off the road.
For the ARPA-E award, Weitekamp is collaborating with Berkeley Lab’s Steve Selkowitz, a leading expert on building science and window technologies, and Arman Shehabi, an expert in analyzing energy use of buildings, to develop a cost-competitive and scalable product.
“ARPA-E invests in high-risk, high-reward projects,” Shehabi said. “The high reward in this project isn’t in the performance improvement. It’s transformative in how windows could be retrofitted—it’s something you can do yourself. The market need is very large, and there’s nothing low-cost out there that meets that need.”
The team is committed to making the coating available at one-tenth the market price for commercially installed energy-efficient retrofit window coatings, which is about $1.50 per square foot.
But the team is faced with the task of making the material highly efficient so that infrared light can reflect, while visible light remains clear and not scattered. With this, the coating will be able to reflect much of the sun while minimizing the heat entering into a building and still remaining very clear. The performance of coating will be analyzed by Selkowitz who will be using Berkeley Lab resources to achieve this.
“We have a well-equipped optics lab where we can do detailed optical measurements of any coating on any glass substrate, looking at the optical and spectral properties, which can provide feedback to the chemical synthesis process,” Selkowitz said.
“In the development phase, all that optical testing becomes a feedback loop to the chemistry. Additionally we can model and measure thermal comfort, which is important because what will motivate people to buy this coating is comfort in addition to energy savings,” he added.
Weitekamp noted that the team did not use expensive material and feedstock while research was going on in the lab, but they applied the knowledge of technoeconomics to make things work out. “This was originally an exploratory synthetic chemistry project, but having the deep windows and building expertise on the applied side here at Berkeley Lab, we thought, we can do this in a bigger and better way,” he explained.