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The increase of 1.09 °C in global temperature resulted in significant catastrophes because of the extreme climate. The climate change rate can be slowed down by reducing the levels of CH4 and CO2 in the atmosphere. The solar chimney power plant integrated with a honeycomb photocatalytic reactor (SCPP-HPCR) uses the photocatalytic technology to remove atmospheric CH4. In addition, CO2 emissions can be reduced from coal fired power plant due to the generating capacity of the system. In this paper, the influence of the geometric parameters of the reactor and turbine on the overall performance of the SCPP-HPCR is studied by numerical simulation. The obtained results showed that the flow resistance inside the system was mostly caused by the HPCR at low turbine speed, and primarily by the turbine at high turbine speed. Reducing the pore diameter of the reactor could improve the photocatalytic performance of the SCPP-HPCR more than increasing the turbine speed. The SCPP-HPCR having a pore diameter of 3 mm, porosity of 0.85, and constant turbine speed of 180 rpm, built in Qianyanzhou, China, could remove 2.38 kg of CH4 and reduce 375.52 kg of CO2 in one day.

Methane's global warming potential (GWP) is much larger than carbon dioxide and contributes significantly to global warming. Solar chimney power plant (SCPP) integrated with photocatalytic reactors can capture and remove atmospheric methane, and generate electrical power without fossil energy consumption simultaneously. In this paper, the performance of the flow characteristics, the CH4 removal, the CO2 emission reduction, and the power generation were analyzed for the SCPP integrated with different types of photocatalytic reactors under ambient crosswind (ACW). The results revealed that the SCPP integrated with a honeycomb reactor was more stable for the degradation of CH4 than that with a plate reactor. With an increase in ACW, the removal rate of atmospheric CH4 was reduced to a constant value of 0.41 g/s for the honeycomb reactor and 0.11 g/s for the plate reactor. The SCPP integrated with a honeycomb reactor achieved a maximum power generation of 88.31 kW, which was 1.63 times than that of the conventional SCPP when G = 857 W/m2 and ACW = 0 m/s. In addition, the improved SCPP could reduce CO2 emissions by 85.04 kg/h when G = 857 W/m2, ACW = 0 m/s, and △P = 320 Pa.

According to the latest report from the intergovernmental panel on climate change (IPCC), currently, global warming due to methane (CH4) alone is about 0.5°C while due to carbon dioxide (CO2) alone is about 0.75°C. As CH4 emissions will continue growing, in order to limit warming to 1.5˚C, some of the most effective strategies are rapidly reducing CH4 emissions and developing large scale CH4 removal methods. The aim of this review article is to summarise and propose possible methods for atmospheric CH4 removal, based on the hydroxyl radical (°OH), which is the principal natural sink of many gases in the atmosphere and on many water surfaces. Inspired by mechanisms of °OH generation in the atmosphere and observed or predicted enhancement of °OH by climate change and human activities, we proposed several methods to enhance the °OH sink by some physical means using water vapour and artificial UV radiation.

Pollutant distribution remains poorly understood when traffic tidal flows (TTFs) happen. By conducting computational fluid dynamic (CFD) simulations, the research efforts first focus on how different-side traffic-produced flow and turbulence (TPFT) affect in-canyon airflow and corresponding pollutant dispersion. Second, the composite effects of non-uniform traffic emission and TPFT are investigated. Finally, the influences of TTFs while varying different street canyon geometry and approaching wind condition is explored. The results demonstrate that the turbulent diffusion terms enhanced by the traffic movement contribute to the pollutant dispersion around traffic lanes. Besides, both-side TPFTs push leeward pollutants towards traffic flow “downstream” due to the unidirectional advection terms along the traffic direction. Simultaneously considering the non-uniform traffic emission and TPFT, either leeward- or windward-congested TTFs has a higher concentration at the pedestrian level close to the congested traffic lane. Besides, the TTF with windward congestion has a higher volume-average concentration of the whole street canyon. With varying building separation, street canyon aspect ratio, and incoming wind direction, the TTFs still result in a larger pollutant accumulation above the pedestrian level, which is nearby the congested traffic flow.

Methane (CH 4 ) is a potent greenhouse gas and the second highest contributor to global warming. CH 4 emissions are still growing at an alarmingly high pace. To limit global warming to 1.5 o C, one of the most effective strategies is to reduce rapidly the CH 4 emissions by developing large-scale methane removal methods. The purpose of this perspective paper is threefold. (1) To highlight the technology gap dealing with low concentration CH 4 (at many emission sources and in the atmosphere). (2) To analyze the challenges and prospects of solar-driven gas phase advanced oxidation processes for CH 4 removal. And (3) to propose some ideas, which may help to develop solar-driven gas phase advanced oxidation processes and make them deployable at a climate significant scale.

The greenhouse effect is exacerbated as greenhouse gas concentrations rise. Capturing and degrading methane in the atmosphere can effectively slow the trend of global temperature rise. The solar chimney power plant integrated with photocatalytic reactor (SCPP-PCR) is a promising concept for both clean electricity generation and large-scale atmospheric methane removal. In this paper, this concept was for the first time quantitatively verified by integrating a photocatalytic reactor in the collector of SCPP to realize the above two targets. A systematic numerical model was proposed to evaluate the performance of degradation of methane and the electricity generation of the SCPP-PCR. The results revealed that the methane purification rate decreased with increasing turbine rotational speed, but the photocatalytic efficiency improved. In this research, the start of the PCR was set at the entrance of the collector, and it was cost-effective to lay 40 m in the radial direction with an investment of $4587 (around 0.37% of the total investment of the system). The system could degrade 30 595.47 g of atmospheric methane and reduce CO 2 emissions by 245.38 kg in the daytime in Wuhan. It was revealed that SCPP-PCR could be crucial for reducing greenhouse gas and limiting climate change.

Dust accumulation is one of the reasons for the performance degradation of concentrating photovoltaic and thermal (CPV/T) systems due to the deposition of dust particles with different compositions, shapes, sizes, and masses. In this work, an optical model was developed to investigate the influence of the particle size, diameter, shape, and deposition density on the light concentration efficiency, using the Monte Carlo raytracing (MCRT) method in the Tracepro software. The triangular particles had a larger influence on the light ray deflection and energy flux degradation than the circular and square particles. An average increase in the dust density of 1 g/m2 decreased the light concentration efficiency of particles with sizes smaller than 50 µm and 60 µm by 3.31% and 3.26%, respectively. Furthermore, the effect of the incidence angle on the light concentration efficiency was considered at an angle less than 2°.

In this paper, the influences of the ambient wind speed and the height and width of a viaduct in a 2-dimensional street canyon on the diffusion of reactive pollutants emitted by motor vehicles were investigated using computational fluid dynamics (CFD) method. Pollutants were treated as reactive by including a NO-NO2-O3 photochemical reaction mechanism in the simulation. The Reynolds-averaged Navier-Stokes (RANS) k–e turbulence model and the discrete phase model were used to simulate the airflow movement and the concentration distribution, respectively, of the reactive pollutants in the street canyon. Three indices, i.e., the chemical reaction contribution of NO (CRCNO), the chemical reaction contribution of NO2 $$\left({{\rm{CR}}{{\rm{C}}_{{\rm{N}}{{\rm{O}}_2}}}} \right)$$ , and the O3 depletion rate, were used to evaluate the relative importance of the photochemical reactions. It was found that the presence of a viaduct changed the flow field structure in the street canyon. The CRCNO and $${\rm{CR}}{{\rm{C}}_{{\rm{N}}{{\rm{O}}_2}}}$$ decreased from the windward side to the leeward side of the canyon. The maximum values of the CRCNO and $${\rm{CR}}{{\rm{C}}_{{\rm{N}}{{\rm{O}}_2}}}$$ were observed at the pollution source (x = 245 m) due to the influence of a clockwise vortex in the street canyon. As the height and width of the viaduct increased, concentration of the ground pollutants and the O3 depletion rate increased. The O3 depletion rate was much higher on the leeward side (90%) than on the windward side. The pollutant concentrations after the reaction were twice as high with the viaduct as without the viaduct when the viaduct height was the same as the building height. The viaduct had a significantly larger influence on the concentration of the reactive pollutants than the chemical reactions. The O3 depletion rate in the canyon and the pollutant concentrations decreased as the ambient wind speed increased, whereas the $${\rm{CR}}{{\rm{C}}_{{\rm{N}}{{\rm{O}}_2}}}$$ increased.

During their rapid economic development and industrialization, megacities in the developing nations with high populations (especially in the east and south Asia) are plagued by severe air pollution problems (e.g., heavy haze), which impose a threat not only to public health but also to the sustainable development of society and the economy. To relieve the burden of air pollution for the general public, this article reviewed several geoengineering measures based on solar chimneys, which have the large-scale elimination ability on pollutants in the air, particularly for particulate matter. These geoengineering measures include driving the polluted air penetrate the planetary boundary layer into the troposphere to avoid the dramatic growth of concentrations of particulate matter, spraying water on the top of the solar chimney into the air to scavenge pollution, and intercepting fine particles in the air driven by the solar energy with large filters. Compared with traditional methods (e.g., giant spray trucks), those solar chimney geoengineering measures have the following advantages: 1) they can be operated 24 h a day, thus keeping the pollution removal function stable and continuous; 2) they are environment-friendly and can generate clean electricity to compensate for energy consumption; 3) they are also robust and operational with very low maintenance for a long period. Given the advantages of the solar chimney geoengineering measures and the economic and human health losses caused by air pollution, those geoengineering approaches deserve to be studied further and implemented in those countries that are suffering from heavy air pollution problems.

Vehicle emissions are an important factor in the deterioration of air quality in urban street canyons. To improve the air quality in urban street canyons, it is necessary to have a deep understanding of the mechanism of pollutant dispersion within the urban boundary layer. The transport process of pollutants in street canyons is essentially a convective mass transfer process. In this paper, a computational fluid dynamics (CFD) simulation is conducted to investigate the effects of wind speed, the setting of the viaduct, and the roof shapes of the street canyons on pollutant dispersion. According to the field synergy theory, Sherwood number and field synergy number are used to evaluate the three factors on the diffusion of pollutants in street canyons quantitatively. The results show that the Sherwood number decreases with increased viaduct construction height and decreased wind speed, which is compatible with the observed growth of pollutant fraction in the street canyon. When the pollution source on the viaduct is considered, a less substantial influence of construction height on pollutant diffusion is observed. Among the four types of roofs, upward pitched roofs resulted in the highest pollution, with a pollution concentration degree of 1.6–2.3 times that of flat roofs, followed by double pitched roofs, with a pollution concentration degree of 1.2–2 times that of a flat roof. By the method of analogy analysis and numerical simulation, the field synergy theory has been extended from applications in heat transfer in small-scale confined spaces to those in urban street canyon pollution simulation in large-scale open spaces.

Dust deposition causes a significant loss of performance of a high-concentration photovoltaic thermal (HCPV/T) system. In this paper, the influence of dust deposition on the output performance of a gallium arsenide cell HCPV/T with a Fresnel lens was investigated using a dust deposition test. The changes in the thermoelectric and exergy performance of the system were analyzed at different dust densities. The influence of the dust particle size on the relative overall efficiency was determined. The results showed that the thermal efficiency and electrical efficiency decreased by 2.65% and 1.29%, respectively, for a 1 g/m2 increase in the dust density. At the same dust density, the relative overall efficiency was lower for the smaller dust particle size. Model fitting and calculations indicated that the rate of decline in power output reached the maximum at a dust density of 9.84 g/m2. The results provide references for similar experiments.

Solar reflecting and heat collecting systems are generally operated outdoors year-round, and the optical performance of the reflector is reduced by dust accumulation on the surface. In this study, the dust accumulation on a linear Fresnel reflector was investigated. The relative reflectivity of the mirror before and after dust accumulation and the physical and chemical characteristics of the dust were measured using an ultraviolet spectrophotometer, scanning electron microscope, and X-ray diffractometer. The results showed that the dust density on the mirror increased, and the relative reflectivity decreased with an increase in the dust accumulation time. During 48 days of dust accumulation, the average relative reflectivity decreased 9.4% for a 1 g/m2 increase in the dust density. Additionally, the dust density on the mirror increased while the relative reflectivity decreased with a decrease in the mirror tilt angle. The rate of decrease of the relative reflectivity was higher for the aluminum mirror than that of the silver mirror after dust accumulation. The main component of the dust particles in the test area was SiO2, and the particle size range of the dust was 0.9 um to 87 µm. According to the physical and chemical properties of the dust and the shielding effect of the dust on the mirror, a model to predict the influence of natural dust accumulation on the relative reflectivity of the linear Fresnel reflector was proposed. The predicted results deviated about 1% from the test results.

Increasing traffic emission presents a high risk of exposure to residents in near-road buildings. Traffic tidal flow (TTF) has gradually become one of the most important components of urban traffic congestion. By computational fluid dynamics simulation, the present study examines the airflow, spatial distribution of pollutant concentration, and personal intake fraction (IF_p) of CO in five street canyon structures (shallow, regular, deep, step-up, and step-down street canyons), with non-uniform TTF-induced traffic emission considered. Optimal urban design devices (wind catchers) are subsequently introduced to reduce IF_p. The results suggest that leeward IF_p is far higher in concentration than the windward wall in the shallow, regular, step-up, and step-down street canyons but lower than the windward side in the deep street canyon under different TTF conditions. Moreover, the TTF condition SL (leeward source)/SW (windward source)=3/1 leads to a higher leeward IF_p in the shallow, regular, deep, and step-up street canyons, compared with SL/SW=1/3; however, no significant difference in windward IF_p is found under the different TTF conditions. The highest IF_p and lowest IF_p for both TTF configurations occur in the step-down and shallow street canyons, respectively. Finally, the effect of wind catchers (WCs) varies between the street canyon structures under different TTF conditions. WCs can lead to at least 30.6% reduction in leeward overall average IF_p ( ) in the shallow, regular, step-up, and step-down street canyons, as well as 12.8%–78.4% decrease in windward 〈IF_p〉 owing to the WCs in the regular, deep, step-up, and step-down street canyons.

Solar reflectors are exposed to outdoor environments where dust accumulation is a primary degrading factor on optical performance. In this study, the effect of dust accumulation on reflectivity at different positions on the reflector of a parabolic trough solar thermal power plant in Hohhot, China was investigated and analyzed. The physical and chemical properties of dust accumulation were tested using a combination of spectrophotometer, scanning electron microscopy, and X-ray diffraction. The results showed that dust accumulation on the bottom edge of the reflector caused the largest decrease in reflectivity compared to dust on the center and top edge. In addition, dust particles at Hohhot were dominated by quartz (SiO2, 53.5%), followed by calcium oxide (CaCO3, 25.4%), and some minor feldspar minerals (NaAlSi3O8, 21.1%). However, some characteristics of the dust could not be determined by experimental measurements. To address this gap, a physical model was proposed to predict the impact of dust accumulation on light reflectivity of the reflector. Different physical parameters of the model are discussed, such as the size of the particles, diaphaneity, the incidence light angle, and tilt angle. The maximum relative deviation between the mathematical model and the experimental results was only 1%.

This study reports the optimal solar thermal performance of two innovative configurations of air-vacuum layered triple glazed window or Integrated Vacuum Window (IVW). These are when the vacuum layer of IVW is facing the warm or indoor side, i.e. IVWwarm, and when the vacuum layer of IVW is facing the cold or outdoor side, i.e. IVWcold, positions at dynamic solar insolation under winter and summer EN-ISO standard ambient conditions. A theoretically and experimentally validated finite element model is employed. The results show that in winter conditions, although the U-value of IVWwarm of 0.33 Wm−2K−1 is lower than that of IVWcold of 0.49 Wm−2K−1, the IVWcold has a higher solar heat gain. In sunny winter conditions, IVWcold provides higher energy efficiency while in winter night, IVWwarm provides higher energy efficiency than IVWcold. The results show that in summer conditions the U-value of IVWwarm and IVWcold are 0.34 Wm−2K−1 and 0.51 Wm−2K−1 respectively, while IVWwarm provides lower cooling-load and higher energy-efficiency compared to IVWcold. It is concluded that setting the vacuum gap at the indoor side position provides lower cooling-load and higher energy-efficiency compared to setting the vacuum cavity at the outdoor side position in summer ambient conditions.

In order to attain an efficient path into the enhancement of the sustainable conservation and management of energy resources in the buildings and residential sections, efforts by all relevant institutions in the area of energy are essential and primitive. Hence, the development of the energy supply model in the building and the provision of fundamental solutions in this area is rudimentary. The key to any program related to this matter is to boost and extend energy efficiency and energy resource management. According to the global statistics and processed data, the residential sector accounts for 34 percent of the total energy consumption in Iran, which is the highest energy consumption compared to all existing sectors; therefore, immeasurable research has been done on optimizing energy usage in the building sector. One of the most efficient energy optimization methods can be achieved by using energy storage materials in the outer walls of the buildings. In this project, a research‐based residential building is considered as a case to investigate for energy optimization. In the first stage, the building is simulated and the energy consumption of the building is measured. Afterward, with actual measurements, real consumption is approximated and compared with the results of the software. After verifying the software data, the insulation is simulated in the software and the outcomes of using this insulator are investigated to reduce energy consumption. Energy storage materials are considered as a type of phase‐change material. These materials have the same characteristics which is having a different melting point and, by capturing and losing heat at design temperatures, they can help maintain energy inside the building that is how they can be considered as an insulator. Within the appropriate software which is Design‐Builder, miscellaneous types of these materials are available with various features. The final results point out that the use of this material saves up to 30% of the heating energy and about 8% in the cooling load of the building.

Global Warming will probably modify air circulation patterns and increase the severity of droughts, heat waves, heavy precipitation, and floods across the world. A device called ‘aerological accelerator’ (AeAc) is proposed in this paper to harvest water from the air using a very high tower where the warm and humid air enters from the bottom and rises till the top driven by buoyancy force. This AeAc device is similar in operation principle to a solar chimney power plant (SCPP) with additional features. A mathematical model was developed to calculate the potential energy and water that can be generated in various environments. The calculation results show that clouds are generated within and out of the chimney and the latent heat released by the vapor can noticeably increase the power output of the modified SCPP. With a proper water collecting method, the system can supply water and carbon-free renewable energy for residential and agricultural use. The present study opens the perspective that with minor improvements, significant energy and freshwater production might be possible using these tall engineering structures, whose high chimney can be built thanks to fabric balloons filled with gases lighter than air.

An increasing number of research highlight the fact that in order to have some chances to stay below the 2°C global average warming target fixed at the Paris agreement on the climate, greenhouse gas removal from atmosphere will be absolutely necessary in the coming decades. Methane is the second most harmful greenhouse gas accounting for 25% of radiative forcing and its concentration is increasing rapidly. Our previous study reviewed the potential of heterogeneous photocatalytic reactions to destroy a large quantity of methane from air. It was proposed to incorporating photocatalysis with solar updraft Towers (SUT) to remove methane from the air at a planetary scale. In this study, we present a review and deep analysis by calculating the potential of methane removal in relation to the dimensions and configuration of SUT using different photocatalysts. The analysis shows that the methane removal rate increases with the SUT dimensions and can be enhanced by changing the configuration design. More importantly, the low methane removal rate on conventional TiO2 photocatalyst can be significantly improved to, for example,42.5% on a more effective Ag-doped ZnO photocatalyst in a 200 MW SUT while the photocatalytic reaction is the rate limiting step. The factors that may further affect the removal of methane, such as more efficient photocatalysts, night operation and reaction zone are discussed as possible solutions to further improve the system.

With the rapid increasing heat fluxes released from micro electronic devices, thermal management of electric components faces huge challenge. High working temperature generated by the chip will directly affect its performance. It is essential to develop advanced model to enhance heat transfer. In this study, a new microchannel heat sinks with impinging jets and dimples (MHSIJD) model with side outlets was proposed. Computational fluid dynamics simulation methodology with RNG k–e turbulence model was used to investigate the performance of MHSIJD with side outlets. Valuation indices including thermal capability, pump consumption and overall performance were analyzed. Three models were compared with basic model (MHSIJD without side outlets): the cross section of the side outlet was set as 0.2 × 0.2 mm (Case 1), 0.4 × 0.4 mm (Case 2), and 0.6 × 0.6 mm (Case 3). The results showed that: (1) the MHSIJD with side outlets performs better heat transfer characteristic due to the alleviation of drift phenomenon. The heat transfer capacity can be increased by up to 17.51%; (2) the MHSIJD with side outlets exhibits a lower pressure drop, which can be reduced up to 22.39%; and (3) the overall performance of MHSIJD with side outlets is better due to its higher cooling efficiency and lower pump consumption.

The engineering of building envelope aims is to achieve building energy efficiency which uses shading device to increase the shaded area. Also, to reduce heat gain by the building from solar radiation, this will reduce the energy load on the building. This paper aim to focuses on the deepening of technology of building envelope elements, and how the building envelope can control the thermal comfort as part of the indoor environment in a building that carries sustainability architecture. In conclusion, finally, reveal that the principles of passive design on building envelope have a great influence on the comfort level in the building. It is not possible to create a design that meets the thermal comfort requirements by emphasizing the design of building envelopes. The goal to be achieved in sustainable design is to minimize the use of the current design that takes much energy (almost14% world energy consumption) to address the issue of energy crisis lately.