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Renewable energy has become more popular since it is cost-effective and more efficient than conventional energy sources. Biomass-based renewable energy is primarily used in emerging economies to ensure environmental sustainability. This study examines the asymmetric correlation between biomass energy consumption and CO2 emissions in the top-10 biomass energy consumer countries (Brazil, Canada, Thailand, China, Italy, India, Germany, USA, UK, and Japan). A new approach "Quantile-onQuantile (QQ)" is employed by utilizing the data from 1991 to 2018. Biomass energy consumption, with the exception of Thailand, significantly mitigates CO2 emissions at various quantiles in selected countries. As a robustness check, we used the quantile regression test, whose findings are consistent with the outcomes from the quantile-on-quantile method. However, the degree of asymmetry in the biomass energy-CO2 nexus varies by country, necessitating extra attention and government vigilance when developing biomass energy and environmental policies.

Abstract The north wall of Chinese solar greenhouses (CSGs) plays an important role in maintaining their indoor thermal environment without additional heating during the wintertime. To enhance the heat storage/release capacity of the CSG wall and further improve the indoor thermal environment, an active-passive phase change thermal storage wall system has been developed in this study. The system was composed of 5 concentrating solar air collectors (CSACs), 6 tanks that were embedded in the north wall of the CSG and filled by phase change material (PCM), tubes linking the tanks and the CSACs and a centrifugal fan with variable-frequency drive (VFD). During the daytime, the solar energy was collected by the CSACs and stored in the tanks, whereas during the nighttime, the stored energy was released into the indoor environment of the CSG through a passive heat mode of the north wall or an active heat mode of the system. Then, a numerical model of the active-passive phase change thermal storage wall system has been developed. The simulation results were validated by the experimental data with the maximum relative error and average relative error being 5.6% and 3.9%, respectively. Furthermore, the heat release capacity characteristics in three cases with the air velocities of 2 m/s (Case A), 3 m/s (Case B) and 4 m/s (Case C) at indoor outlet for the active heat mode and a passive heating case (Case D) were chosen as the control groups for study. In the proposed wall, the heat release capacity of ventilation increased and that of inner surface of the wall declined with an increasing ventilation velocity. The total heat release capacities of the cases A, B and C were 38.12 MJ, 40.26 MJ, 42.00 MJ, respectively, higher than that of the case D (33.76 MJ). On the other hand, the calculated temperature distribution indicated that there was no thermal-stable layer within depth of the 360 mm in the wall due to an apparent temperature variation of the PCM layer by ventilation. These results suggested that the proposed system could effectively promote the heat storage/release capacity of the middle layer of the wall.

Abstract Climate responsive strategies contained in traditional native dwellings can provide theoretical basis for the development of sustainable buildings. This study focused on a quantitative analysis of cliff-side cave dwellings located in cold region of China. Field measurements in summer and winter were carried out. Based on the monitoring data, thermal environment of the cave dwelling and thermal characteristics of the adobe massive building envelope were evaluated. Results showed that the cliff-side cave dwelling was well adapted to local environment for its good ability of thermal insulation under the natural conditions. Furthermore, in order to assess the whole annual thermal performance and thermal comfort level, numerical simulations on the cliff-side cave dwelling models was also performed using the software Energyplus. Results showed that 52.50% time of the year was comfortable of the living room. Meanwhile, some technical strategies of making full use of solar energy and natural ventilation was proposed in the end of this paper, which can provide technical support for the regeneration design of traditional residential buildings.

Numerical simulations were performed for the effect of injection and ignition timings on combustion and the generation of formaldehyde and unburned methanol emissions in the cylinder of a stratified charge direct injection spark ignition (DISI) methanol engine during cold start using AVL-fire, coupling the methanol chemical and kinetic reaction mechanisms. A non-uniform spray-line distribution nozzle was used to form stratified charge methanol-air mixtures during cold start. The simulation shows that injection and ignition timings have a significant effect on the concentration distribution of the methanol-air mixture, and hence the affect combustion and generation of formaldehyde and unburned methanol emissions. Optimized injection and ignition timings form an ideal stratified charge distribution. Formaldehyde and unburned methanol emissions decrease with retarding of the injection timing, but increase with retarding of the ignition timing. Formaldehyde and unburned methanol emissions at injection timing 41°crank angle before top dead center (CABTDC) were 48% and 82% higher than for 57°CABTDC, and those at ignition timing 8°CABTDC were 125% and 900% higher than for 20°CABTDC, respectively. Optimal injection and ignition timings provide the best compromise between the maximum cylinder pressure, maximum heat release rate, maximum cylinder temperature, and formaldehyde and unburned methanol emissions. Injection timing 45°CABTDC and ignition timing 14°CABTDC obtained the best compromise on cold start performance.

The emission characteristics of particulate matters from a full-scale biomass-fired power plant equipped with bag filters were investigated. Results show that particle size distribution at the inlet of bag filter from the combustion of blended feedstocks is bimodal, while that of dry bark feedstocks is essentially unimodal with negligible emission of coarse particles with diameter in the range of 1.0–10 μm. The combustion of blended fuels generates higher yields of submicro particles than that of dry bark feedstocks. Elemental analysis shows that submicro particles in all cases mainly consist of potassium, chlorine, and sulfur. Higher chlorine but lower sulfur contents are observed in submicro particles from blended fuels compared with that from dry bark feedstocks. The vibrating operation of grate furnace reduces submicro particles emission as well as the sulfur content in all particles. Ion chromatography results show that sulfate ion and chloridion are the two most abundant water-soluble anions in particulate matters, while water-soluble cations are richest in potassium with considerable content of calcium, magnesium, sodium and ammonia. The contribution of organic and element carbon in particulate matters is in the range of 1–3%, indicating high combustion efficiencies and low organic and element carbon emissions of biomass-fired grate furnaces.

© 2021 Elsevier LtdDespite extensive research to address the impact of environmental reforms under the Paris Climate Agreement, current literature has failed to provide sufficient insights into Regional Comprehensive Economic Partnership (RCEP) countries. To this end, the current study attempts to address the impact of the economic complexity on environmental quality in the presence of renewable energy consumption, financial development, urbanization and energy innovation in RCEP countries from 1990 to 2019. Our empirical estimates confirm a significant association between environmental quality, economic complexity index, renewable energy consumption, financial development, urbanization and energy innovation in the short-run and long run. Based on extensive econometric analysis (CS-ARDL, AMG, PMG, FMOLS, and DOLS), we conclude that economic complexity, renewable energy, and energy innovation effectively mitigate environmental degradation. At the same time, financial development and urbanization have an adverse impact on the environment. These findings have extensive policy implications for policymakers and environmental stakeholders, who are aiming to achieve sustainable energy policy and economic growth to meet the environmental commitments under Paris Climate Agreement.

Abstract The world’s key renewable power markets are generally challenged by wind and solar power curtailment. Research on the influencing factors of curtailment improvement can provide a reference for the further penetration of renewable energy (RE) into the power system. Based on the logarithmic mean Divisia index (LMDI) method, this paper analyzes the factors influencing the wind and solar power consumption rate in China from 2015 to 2018, and four typical provinces are discussed in detail. By decomposing the consumption rate into six factors (transmission structure, generation proportion, power self-sufficiency, resource development, resource utilization, and power consumption), and focusing on the transmission structure factors, this paper further clarifies the contributions of local use, ultra-high-voltage (UHV) transmission, and conventional transmission to the improvement of curtailment. The results reveal the following. (1) At the national level, the power mixing effect and the resource development effect have played major roles in the change of the consumption rate, but the influences of these two effects have been decreasing. (2) The UHV power lines provide a robust resource for the inter-provincial deployment of renewable power (such as the RE power transfer in Inner Mongolia and Gansu), but the role of UHV transmission has not yet been fully utilized. (3) The impact of the electricity consumption effect on renewable power consumption is increasing year by year, but the local consumption capacity remains insufficient (both at the national level and in the four typical provinces analyzed), so it is necessary to further increase the share of renewable electricity in UHV power transmission and the local consumption capacity. (4) The expanding development of wind and solar power may be the reason for the curtailment in Shaanxi, and a reasonable renewable power development plan must be further formulated.

Abstract Hydrothermal liquefaction (HTL) of biomass into biocrude is attractive but the biocrude themselves are poor fuels, which need to be upgraded for further utilization. Compared with the traditional catalytic upgradation process, a non-catalytic method for biocrude upgrading in the aqueous waste (HTL-AW) derived from HTL of cornstalk was proposed. Optimal reaction conditions of upgradation process were obtained at 356 °C (temperature), 37 min (reaction time) and 19 mL/g (HTL-AW/biocrude) based on the response surface methodology. The biocrude was effectively upgraded in the HTL-AW and a high hydrogen to carbon effective (H/Ceff) ratio of 1.07 with a higher heating value of 36.94 MJ/kg was observed. The energy recovery of ∼80% from biocrude to upgraded biocrude was feasible. GC–MS analysis showed that the contents of phenols and ketones were decreased from 65.61% to 48.38% and 22.39%–16.78%, respectively, while the contents of nitrogen-containing compounds n-hexadecanoic acid were increased from 2.25% to 10.15% and 9.56%–22.23%, respectively. The high H/Ceff was attributed to the promoted deoxygenation by alkali and alkaline earth metals as well as H+ enriched in the HTL-AW. This study demonstrates the feasibility of improving the H/Ceff of biocrude in the HTL-AW under a relatively mild reaction condition.

Abstract The sale of value-added byproducts from hydrogen-generating reactions is a strategic approach to lower the costs of hydrogen fuel in order to realize a truly sustainable hydrogen economy. Metal hydrolysis is a chemical process that produces hydrogen together with a metal hydroxide species; however, this reaction is rarely observed without chemical additives or extreme reaction conditions. Previously, we demonstrated that hierarchical nanoporous aluminum can create hydrogen at standard conditions for temperature and pressure via hydrolysis without any additives. The advantage of this method is the co-production of pure aluminum hydroxide (Al(OH)3). Here we explore the transformation of this Al(OH)3 hydrolysis byproduct into valuable materials to elucidate strategies in reducing the overall cost of hydrogen generated. In particular, we demonstrate in this work that (i) the synthesis of hierarchical nanoporous aluminum is scalable to meet the needs of large-scale production for a hydrogen economy, and (ii) the Al(OH)3 hydrolysis byproduct can be transformed to create high surface-area “activated alumina” (Al2O3) as a commercially viable product.