A new white paint formula allows us to have the whitest white so far. All the light it reflects is jaw-dropping, falling to 98.1% of the jaw-dropping level. Even in full sunlight, it is still much cooler than the ambient temperature.
Its inventor said that if the paint is used in buildings, the paint can reduce dependence on electric air conditioners, thereby helping to fight against global warming, a habit that worsens the climate crisis.
“If you want to use this paint to cover about 1,000 square feet of roof area, [92.9 square meters], We estimate that you can get 10 kW of cooling power. Said Ruan Xiulin, a mechanical engineer at Purdue University.
“This is more powerful than the central air conditioning used in most houses.”
The team’s work is based on the paint they developed last year, which achieved a record-breaking 95.5% reflectivity. The research team said the new formula brings it closer to its true counterpart, Vantablack, which is a black pigment that can absorb up to 99.995% of visible light.
The left side of the picture below is optical light, and the right side is infrared light, which shows how much cooler the painted surface is than the surrounding surface.
Vantablack has its own application, but engineers and material scientists have been pursuing super-reflective white paint because of its potential cooling capacity. Reflective cooling coatings are already available on the market, such as titanium dioxide coatings, but they cannot achieve a temperature lower than the ambient temperature.
In order to develop new coatings, researchers looked for white materials with high reflectivity. Their previous paint was made with calcium carbonate particles, which are compounds found in chalk, limestone and marble, suspended in an acrylic paint medium.
For their new formulation, they turned to barium sulfate, which is a natural mineral barite, commonly used as a pigment in white paint.
Li Xiangyu, a mechanical engineer at the Massachusetts Institute of Technology, said: “We have studied various commercial products, which are basically white.”
“We found that using barium sulfate, in theory, you can make objects truly reflective, which means they do have a true white color.”
The trick lies in the size and concentration of the particles. A series of different barium sulfate particle sizes can make the paint scatter the maximum amount of light, of course, the more barium sulfate, the more light it can reflect. However, there is one area where too much barium sulfate can damage the integrity of the coating, making it dry and brittle.
The researchers found that the best place is that the concentration of barium sulfate in the acrylic medium is about 60%.
In the field test, the research team found that their painted surface can always be kept at least 4.5 degrees Celsius lower than the ambient temperature, so as to achieve an average cooling power of 117 watts per square meter. It even maintained this state in the cold winter.
For comparison, the team’s calcium carbonate coating has a surface temperature of more than 1.7 degrees Celsius lower than the ambient temperature at noon, and a cooling power of 37 watts per square meter-so there are few additional percentages in the barium sulfate coating that produce significant reflectivity difference.
Due to material limitations, barium sulfate paint may not get too much more Reflect, but the achievements of the team can actually make the world a better place.
Air conditioners inject heat into the earth’s atmosphere in a variety of ways, including pushing hot air out of buildings, the heat from running machines, and the electrical energy usually generated by fossil fuels, which makes them run, leading to carbon dioxide emissions.
Since the 1970s, scientists have been looking for a method of passive radiant cooling. This barium sulfate coating is effective, reliable, and can be easily produced commercially. The team has applied for a patent and hopes that this coating will soon enter the state of universal use.
then? Maybe we should license it to all artists except one artist.
The research has been published in ACS applied materials and interfaces.