Preparation And Application Research On The MgO Radiative Cooling Paint

The energy crisis is one of the most important challenges in the 21st century.Cooling systems account for～15%of the world’s total electricity consumption and～10%of greenhouse gases.Moreover,Due to greenhouse gas emissions and global warming,the demand for cooling in lower and middle latitudes is further increasing,creating a vicious cycle that accelerates primary energy consumption.It is quite crucial to study a new refrigeration method in order to reduce the energy consumption of existing steam compression refrigeration.Radiative cooling technology is a new passive cooling technology that emits infrared heat to the outer space（～3K）through the atmospheric window（8μm-13μm）,simultaneously reflecting most of the sunlight.In the way,radiative cooling materials are required to have high reflectivity in the solar band（R>90%）,and has a high emissivity in the atmospheric window（E>90%）.Therefore,preparing radiative cooling materials with properties of scalable,high-efficiency,simple and construction-friendly is the focus and difficulty for popularizing the new cooling technology.Inspired by the low UV absorption and high infrared emission characteristics,the MgO radiative cooling paint was prepared here.The prepared paint has 95%solar reflectivityand 93%infrared emissivity,which are significantly better than those of commercial Ti O₂white coating（R:80%,E:90%）.In order to characterize the cooling performance of the MgO radiative cooling paint,cooling tests were carried out.In the experiments with wind cover,the MgO coating can achieve a temperature drop of 2.2℃ under the solar radiation intensity of～893 W/m².And an improvement effect of 5.2℃ was achieved compared with the commercial paint under the solar radiation of～907 W/m².In the experiments without wind cover,the MgO paint can achievea temperature drop of 3.5℃ under the solar radiation intensity of～868W/m².And an average daytime radiative cooling power of～61.2 W/m²and a maximum nightime radiative cooling power of 78.8 W/m²were measured.In addition,a further radiative cooling model was conducted here.The simulation results showed that MgO paint can achieve a net radiative cooling power of 79.4 W/m²and a maximum temperature drop of 11.3℃ even with a solar radiation intensity of 1000 W/m²when the weather was a sunny and warm（TWC:500ATM-cm,ambient temperature:25℃,wind speed:2 m/s）.In order to study the real energy-saving effect of the radiative coolingpaint,the cooling experiments with building model and outdoor communication cabinet were carried out.In the building cooling experiment,the MgO paint achieved a maximum indoor temperature drop of 2.1℃（756 W/m²solar radiation）and an average temperature drop of 1.6℃.In the cooling experiment of cabinet model,the MgO paint achieved a maximum indoor temperature drop of 13.2℃（673 W/m²solar radiation）.In addition,the energy saving potentials of building/cabinet with MgO coating were further illustrated by Energy Plus.For abv-ambient cooling,the communication base station and communication cabinet saved the electricity power of43.0 k Wh/（a·m²）and 134.8 KWh/a,respectively.For sub-ambientcooling,such as individual retail shopping mall,the cooling energy consumption per unit area can be saved up to～10 k Wh/（a·m²）.The simulation also demonstrated that the applicability of the MgO in most cities in China.