How white is the whitest white? Scientists have discovered that ultra-white paint materials will alleviate the problem of global warming

  In order to curb global warming, scholars at Purdue University have created the whitest paint yet. The researchers said in the interview that applying this kind of paint on buildings may cool them down, thereby reducing the need for air conditioning.
  The research was led by Professor Ruan Xiulin from Purdue University in the United States. The paper related to the ultra-white paint developed by him became the cover paper of the current issue of “Applied Materials and Interface”.
  The paper described in detail that ultra-white paint will help save energy and implement carbon reduction. The whiteness of the paint invented by the research team has reached its limit. Not only is the paint whiter, it also keeps the surface cooler than the formula previously proven by the researchers.
  In a field test, ultra-white paint can cool the surface by 4.5 degrees Celsius at noon. In contrast, the white paint on the market increases the surface temperature by 6.8 degrees Celsius.
  Ruan Xiulin said that the effectiveness of white paint on the market to reflect sunlight is about 80% to 90%, which means that 10% to 20% of the remaining sunlight will be absorbed by the building. Moreover, the main component of white paint contains titanium dioxide, which absorbs ultraviolet rays from the sun and therefore radiates heat, so it cannot achieve a 100% heat dissipation effect.
  The ultra-white paint he developed has improved the shortcomings of the current white paint products on the market. It uses barium sulfate as the main component of the ultra-white paint to achieve the effect of not absorbing ultraviolet rays and reducing sunlight absorption. In addition, the paint particle concentration is increased to 60% during production, which can achieve a better reflection of sunlight.
  The coating of ultra-white paint contains a high concentration of barium sulfate, which is a compound often used in laboratories and industries. For example, it can be used to make photo paper to improve the whiteness and surface coverage. In the past, some people added barium sulfate to paint and In the paint, some of the higher-priced raw materials are replaced, and the viscosity, gloss and stability of the finished paint can be controlled.
  In addition, the size of the barium sulfate particles in the paint is different. The degree to which each particle scatters light depends on its size, so the size of different particles allows the paint to scatter more wavelengths of light in the spectrum, thereby obtaining high reflectivity.
  Ruan Xiulin predicted based on experimental data that if 1% of the earth is painted with ultra-white paint, it is very likely to stop the process of global warming.
  In residential and commercial applications, cooling is an important part of energy consumption. Passive radiant cooling can directly dissipate heat through the transparent spectral window of the atmosphere, thereby cooling the surface without consuming any energy.
  If the heat radiation through the surface of the sky window exceeds its absorption of sunlight, then the surface can be cooled below the ambient temperature under direct sunlight. Compared with traditional air conditioners, passive radiant cooling not only saves electricity, but also because of the direct loss of heat to deep space, it can also combat global warming.
  Ruan Xiulin said that if you use this coating to cover about 1,000 square feet of roof, it is estimated that you can get 10 kilowatts of cooling power, which is more powerful than the central air-conditioning used in most houses.
  Through experiments, the team proved the feasibility of using ultra-white paint for complete radiant cooling during the day, and achieved a high reflectivity of 97.6% during the study. Field tests show that the temperature of the ultra-white paint material is 4.5 degrees Celsius lower than the ambient temperature, and the average cooling power is 117W/㎡.
  In the field test, the ultra-white paint produced the same high cooling capacity as the commercial paint during use.
  It is reported that this white paint is the result of a six-year study. Researchers believe that this white may be the closest equivalent to the blackest black “Vantablack”, which can absorb 99.9% of visible light.
  The new white paint formula can reflect up to 98.1% of the sunlight, while the team’s previous ultra-white paint reflects only 95.5% of the sunlight, while also radiating infrared heat from the surface.
  Researchers said that the material of ultra-white paint, barium sulfate, is a bit cheaper than titanium dioxide, so the final cost is comparable to that of traditional white paint. After further testing, it is expected that it will be put into commercial use within two years.