Purdue researchers create world’s whitest white paint


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WEST LAFAYETTE, Ind. – A new paint developed by researchers at Purdue University is the coolest – literally.

When Xiulin Ruan, a mechanical engineering teacher at the school, and his graduate students started working on this project seven years ago, they had no intention of inventing a new paint color. Instead, they wanted to find a way to conserve energy and fight climate change. But what they found was that paint could do just that.

This is how Ruan and her team created the whitest paint in the world – a title she recently won in the Guinness Book of World Records, a status never before achieved.

This painting, however, can do more than break world records. It is seen as a breakthrough in sustainability, which could reduce or even eliminate the need for air conditioning, and therefore the energy required to power it.

“The impact of this painting is good for trying to mitigate global warming, the urban heat island effect and the electricity crisis,” said Xiangyu Li, postdoctoral researcher at the Massachusetts Institute of Technology who worked on this project as a doctoral student. . student in Ruan’s lab. “But what I love the most is that it could have a direct impact on people’s electricity bills, and it’s something everyone can relate to.”

Developing the formula for this paint was not easy. The multi-year study builds on efforts to create a refreshing paint as an alternative to traditional air conditioning that dates back to the 1970s.

The researchers looked at over 100 different materials and narrowed their options down to 10. From there, the lab tested about 50 different formulations for each material.

“I started to look at all the white materials in my daily life,” Li said.

It was then that they found barium sulfate. The paint is based on two key characteristics: the concentration and size of the barium sulfate compound.

The paint has a very high concentration of the compound, which is also used to make photo paper and white cosmetics. It also contains barium sulfate particles of different sizes in the paint.

Most white paints have a single particle size that reflects the visible part of the solar spectrum, but they absorb more ultraviolet and infrared light, according to Joseph Peoples, a doctoral student. candidate for Purdue School of Mechanical Engineering who also worked in Ruan’s lab.

“The ‘biggest challenge was to make the paint as reflective as possible across the entire solar spectrum,” Peoples said.

The amount of light that each barium sulfate particle diffuses depends on its size, Peoples said. Thus, having a wider range of particle sizes allows the paint to diffuse more of the light spectrum.

Researchers believe this whitest white paint is probably the closest equivalent of Vantablack, the blackest black paint that absorbs up to 99.9% of visible light. The painting Ruan’s lab landed on reflects up to 98.1 percent of sunlight, the research shows. This compares to other highly reflective paints on the market which reflect between 80-90% of the light.

Because Ruan’s painting reflects almost all of the incoming sunlight, it does not consume any energy. Then it goes even further, emitting thermal energy into space beyond Earth’s atmosphere, which means it sends out more heat than it absorbs.

“Let’s say it’s a dry, sunny day outside and the temperature is 85 degrees Fahrenheit,” a surface covered in Purdue paint “will be around 75 degrees Fahrenheit,” Peoples said. “The paint cools below room temperature, creating free refrigeration, without any input of electricity. “

By lowering the surface temperatures of buildings painted with this white paint, the interior temperatures of said buildings are also lowered. If buildings do not heat up because of the sun, it either reduces the need to turn on their air conditioning this high or eliminates it altogether.

“If you were to use this paint to cover a roof area of ​​about 1,000 square feet, we estimate that you could get 10 kilowatts of cooling power,” Ruan said in a statement. “It’s more powerful than the central air conditioners used by most homes. “

Ruan is working to bring the paint to market and therefore his schedule did not allow him to speak with IndyStar.

Although the 98% to 90% difference may not seem large, Li said that before, a building absorbed 10% of sunlight and now only absorbs 2%. advantages.’

When most people think of reducing carbon emissions, they think of the transportation sector and industry. However, buildings generate nearly 40% of the world’s annual energy-related CO2 emissions, according to the United Nations climate report. In Indianapolis, 66% of community-wide greenhouse gas emissions come from buildings, the city said. The majority of these emissions are the result of building operations such as cooling and heating.

Therefore, reducing cooling means using less energy produced by fossil fuels such as coal and natural gas, which could lead to reduced carbon emissions that cause climate change.

“I think the discovery of white paint has potentially significant long-term implications,” said Jeff Dukes, executive director of the Purdue Climate Change Research Center. “In many parts of the world where we want to cool our buildings for most or all of the year for comfortable spaces, this could mean significant energy savings potential.”

The whitest paint can also help reduce the urban heat island effect, according to Peoples. Urban heat islands are the result of cities replacing natural land cover with pavements, buildings and other materials that absorb and retain heat. This increases energy needs, pollution levels and heat-related illnesses.

Climate change is causing more frequent and severe heat waves. According to research conducted at the Dukes center, Indiana could see up to 30 more days above 95 degrees by mid-century.

The recent UN climate change report issued a “code red for humanity” regarding the climate crisis, and stressed the importance of taking swift action to reduce emissions. This paint might just be a tool in that toolbox, Dukes said.

For the everyday American, the paint could also make a big difference to their pockets, Li said, because it essentially creates free air conditioning.

For a one-story house of about 1,000 square feet, paint could save about a dollar a day that would have been spent on air conditioning. This comes down to about $ 30 per month or nearly $ 360 per year in electricity savings.

“Painting has the advantage of saving on electricity bills and at the same time helping to save the earth,” Li said, “it connects with everyone.”

This paint could be used in multiple ways, according to the researchers. Most evident is on commercial and residential buildings, both on their roofs, which face direct sunlight, and on side walls.

But the researchers add that it could even go so far as to be applied to roads or cars to help cool the earth’s surface on an even larger scale.

The team has applied for a patent for the paint and is currently undergoing the necessary tests to bring it to market on a large scale. Ruan and his lab are working with a trading company to ensure the paint meets the reliability requirements for exterior paints and is able to withstand the elements.

There is no timeline for when the paint will hit store shelves, Li said, but it will likely be a few years before customers can purchase it at their local hardware store. Purdue’s paint should be competitive with other exterior paints, he added, and use a similar manufacturing process so that it isn’t difficult to produce.

“Our goal is that if we can bring it to market, it will be like buying any other white paint,” Li said. “The most important way to get the most out of scientific innovation in this field is to ensure that more and more people can use it. “

That’s why Ruan and his graduate students loved the idea of ​​a painting: it’s accessible and easy.

Nonetheless, they recognize that it will be difficult to get people to adopt and use white paint. Especially from a residential perspective, many homeowners might not be used to seeing white walls or they might want their home to stand out from the crowd on their street.

“People aren’t already using white paint everywhere to try to keep buildings cool,” Dukes said, “so the question is, how many people are going to use it? “

The city of Indianapolis said it had ideas on how to increase adoption of such practices. The sustainability office is always looking to make better use of the incentives it can harness and encourage residents to use these types of materials, office executive director Morgan Mickelson said.

City officials also recently enacted a Benchmarking and Transparency Ordinance to help improve the energy and water efficiency of buildings in Indianapolis. Building owners participating in the program are required to measure their buildings’ water and energy use annually and report annually. With that data, they can then work with the city to find ways to make reductions.

Mickelson said she believes this painting, when available, could be a key way to achieve this.

“Our built environment offers one of the greatest opportunities for significantly reducing greenhouse gas emissions,” she said, adding that the city will try to find ways to use this paint on its own buildings. when it becomes available.

“Having the whitest white paint from Purdue University is so exciting,” Mickelson added, “especially to be an institution in Indiana leading this type of work.”

Source: The Indianapolis Star

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