New energy-saving building materials will likely replace air conditioners

The Massachusetts Institute of Technology's 'Technical Review' magazine recently reported that a building material that can absorb heat during the day and release heat at night, thereby reducing the use of air conditioning, will soon be available in the United States.

According to the introduction, gypsum board is currently used on the walls of most buildings. National Gypsum in North Carolina is testing a new type of gypsum board that contains a capsule material that can passively cool buildings by absorbing heat. These capsule substances are produced by the German chemical giant BASF (BASF) and can be added to many construction products. In Europe, this new type of capsule material has been used in some construction products.

This kind of capsule material contains phase change material, that is, the material that changes shape with temperature change and can provide latent heat. This makes the principle of cooling the house the same as the principle of cooling the beverage by absorbing heat when ice cubes melt. . Each polymer capsule contains paraffin wax that melts at room temperature, so that they can keep the room temperature basically constant during the day. Paraffin wax works best under cool weather conditions at night. After the temperature drops at night, the capsule can harden again to release the heat stored during the day.

Peter Schossig is an engineer at the Fraunhofer Institute in Munich, Germany. His research team developed this capsule in cooperation with BASF. He said that in some countries in southern Europe, this material can absorb enough heat during the day to save up to 20% of the electricity demand for air conditioning. In Northern Europe, where the night temperature is cooler, buildings using this material may not need air conditioning at all.

This new achievement helps promote the green trend in the construction industry to use green building materials that can maintain a comfortable indoor temperature without using electricity. According to data from the U.S. Energy Information Administration, in the United States, buildings consume approximately 70% of the country’s electricity generation, of which 8% is used for air conditioning in homes and offices. At present, lightweight construction materials are widely used in the United States, such as wooden frames and gypsum boards. They can make the building complete quickly, but these materials do not absorb much heat, so the room temperature fluctuates greatly throughout the day.

Leon Glicksman, professor of construction technology and mechanical engineering at MIT, said that phase change materials provide a way to add heat storage to lightweight construction materials. Since the 1950s, several companies have tried to develop passive cooling systems that can utilize the characteristics of phase change materials, but they have achieved limited results because it is difficult to add new materials to existing building materials.

BASF obtains microcapsules by rapidly stirring molten wax with hot water. Because wax and water repel each other, wax will form many tiny wax droplets in the water. When the researchers added acrylic precursors to the wax-water mixture, the repulsive force between the wax and water caused the acrylic precursors to coat the surface of the wax droplets. The resulting wet mixture can be added to the powder used to make gypsum board, or it can be added to other building materials such as cement and plaster after drying.

DuPont, another chemical giant, is also manufacturing phase change materials into capsules, and has added them to heat-absorbing plates for sale in Europe. BASF’s strategy is slightly different from DuPont: They sell the capsules to other companies to add to building materials, including ceilings, aerated concrete blocks, and gypsum boards. A study conducted by BASF estimates that, taking electricity prices and climate conditions in Germany as an example, if 360 grams of the phase change material (approximately US$4883) is added to the gypsum used in a residential house, the electricity bill can be saved within 5 years. cover the cost.