Smart self-cooling buildings in urban China

To cope with the heat, some buildings are equipped with smart glass that changes according to temperature or air ducts that take advantage of natural wind.

Nanchuan District, Chongqing City, southwest China, August 2. Photo: CFP

Many parts of China have been hit by heat waves this summer. The average temperature in July was 23.2 degrees Celsius, the highest since 1961, according to data from the China Meteorological Administration. The country is expected to see two more heat waves between now and mid-August. To cope with the high temperatures, experts say more preparation is needed in areas such as urban planning and architectural design to adapt to climate change, CGTN reported on August 3.

As one of the “furnace cities” with long summers in southwest China, Chongqing has many energy-saving buildings that apply advanced technologies such as shading, ventilation and heat dissipation. For example, a building covered with 10,000 square meters of smart glass in the city’s Bonded Port Zone is capable of responding to thermal signals. When the air temperature exceeds 35 degrees Celsius, the glass automatically becomes opaque, blocking sunlight and heat from entering the building, acting as a sunshade.

Smart glass building in Chongqing Bonded Port Zone. Photo: CMG

The smart glass contains a polymer nanogel whose molecules are evenly dispersed at low temperatures, reaching a transparent state and allowing sunlight to pass through, according to Zhong Xianqiang, head of construction projects at Chongqing Bonded Port Zone. "When the temperature rises, the molecules gather, which can refract and reflect light in different light bands. Combining this material with two glass panels to form smart glass can block external heat," Zhong explained.

In the Liangjiang New Area, the Chongqing House also boasts impressive self-cooling capabilities. Dozens of plants, including golden bamboo and ivy, are planted in all the outdoor gardens, covering almost the entire exterior wall of the building. From a distance, the building looks like it is wearing a summer green coat. The dense vegetation creates its own microclimate, helping to reduce the building's surface temperature.

An L-shaped air channel from the northwest corner to the northeast corner of the building also helps keep the space cooler, taking advantage of the wind from the nearby hillside, according to Chen Hangyi, the chief designer of Chongqing House. "With ventilation and rainwater recycling, it is estimated that the building can save 40% to 50% more energy per square meter than average energy-efficient buildings," Chen said.

Chongqing House in Liangjiang New Area is covered with greenery. Photo: CMG

In the southern Chinese city of Guangzhou, district cooling systems (DCS) are widely used. Compared with traditional air conditioning, the new system improves energy efficiency by using part of renewable energy and energy from waste.

At a new DCS station in the Guangzhou International Finance City, there is a 3,000 m3 ice tank. Every night, the station will start making and storing ice when electricity loads are low. The system reduces dependence on expensive and polluting thermal power during peak electricity consumption hours, while making the most of surplus energy such as solar and wind power during off-peak hours, thereby improving overall energy efficiency.

Meanwhile, central cooling systems can help reduce the use of large numbers of small air conditioners in cities, helping to cool down cities and mitigate the heat island effect.