Search Results (2)

Building energy consumption is an essential source of greenhouse gas (GHG) and air pollution. Green roofs can directly absorb ambient CO₂ and remove air pollutants through their vegetation layers, but a limited number of studies have examined their effects on GHG and air pollutant reduction associated with building energy savings, especially in the context of climate change. This research examined the performance of green roofs on CO₂ and air pollutant reduction, including SO₂, PM_2.5, and NO_x, through building energy demand savings in Shanghai, China. Climate change mitigation effects were assessed based on the energy consumption of five types of buildings before and after the installation of green roofs under 2020 and 2050 climate conditions, respectively. EnergyPlus software 9.5.0 was applied to simulate hourly energy consumption for different building prototypes with and without green roofs. Green roofs on all building types exhibited positive energy savings on annual, monthly, and diurnal scales, and they can save more energy for most of the building types under the projected 2050 climate condition. Moreover, most of the building energy saved by green roofs came from the Heating, Ventilation, and Cooling (HVAC) systems. In addition, this study discovered that the energy-saving benefits of green roofs vary based on the type of building they were installed on. Green roofs were found to have the largest energy saving on the shopping mall, especially on extremely hot summer days. Finally, a Geographic Information System (GIS)-based approach was developed with the ability to quantify the amount of GHG and air pollutant reduction associated with building energy savings for existing buildings in the Huangpu District of Shanghai. This approach was also utilized to present the spatial distribution of buildings with different levels of suitability to install green roofs by considering their location attributes and air pollutant reduction potential together, which is the major innovation of this research. The purpose of this study is to provide valuable guidance to policy makers regarding the performance of green roofs in building energy-saving and air quality improvement in the urban environment when facing the challenge of climate change, which is essential for urban sustainability. Full article

The solar cavity heat absorber is the core component of a solar thermal power generation system; its structure and installation position directly affect the efficiency of the heat absorber. To study the influence of these factors on the performance of the heat absorber, in this paper, a numerical simulation of dish solar collector optics is constructed based on the Monte Carlo method, and the distribution characteristics of heat flux density under different heat absorber structures and installation positions are analyzed. The results show that the heat flux density on the inner wall surface of the absorber has a linear relationship with the solar radiation intensity; under the same cavity depth, the energy received by the cylindrical, dome, and inverted cone absorbers is easier to deposit on the top. The heat flux density on the top surface of the inner cavity presents an annular distribution law. As the position of the heat absorber moves away from the dish solar collector surface, the top energy is gradually transferred to the circumferential surface. When the heat absorber is in position B, the total power ratio of different heat absorber structures entering the cavity can reach 99%. At this time, the circular type of heat absorber is more conducive to the full heat absorption of the working medium. Full article