The envelope system is responsible for about 40% of the total energy consumption in a general building. Therefore, building envelope retrofit is an effective method to reduce the energy demand of buildings. In this paper, an optimization model for building envelope retrofit considering performance degradation is proposed to help decision makers to obtain an accurate optimal retrofit plan with a given budget, aiming at maximizing the energy savings and economic benefits. Specifically, the model determines the optimal retrofit options for the windows, walls, roof and a roof-top PV system from their alternatives. Considering that facilities will inevitably age over time, the performance degradation of the envelope components after retrofit is built into the model to ensure the accuracy of the optimal retrofit plan. A case study is carried out to demonstrate the feasibility and effectiveness of the proposed optimization model.
Building retrofit is one of the most effective ways to improve the energy efficiency of buildings. Many studies on building retrofit have been done in the literature. However, the methods provided in these studies are mostly specialized, which means they are suitable for professional building project decision makers and not for ordinary building owners. As we know, the main force to promote green buildings is ordinary building owners. Therefore, this paper studies the effects of retrofitting each individual facility in a building and simulations are done using EnergyPlus to ensure the accuracy of results, thereby, providing a simple and intuitive retrofit guide for ordinary building owners. Through this guideline, building owners can comprehensively understand the energy and economic benefits brought by the retrofit of each individual facility in the building. Based on this, building owners can easily make appropriate retrofit plans according to their buildings’ situation without paying for professional consultation.
China’s Belt and Road Initiative (BRI) provided itself with a stable foundation to deepen the gas cooperation with signatories in the global de-carbon trend. This paper explores the net policy effects of BRI in the aspects of environment, economy, politics, and culture, together with other impacts from the national traits, the governance mode, and the resource types. Results show there’s a significant BRI effect on signatories’ GHG emission deduction, GDP per capita and Projects’ net cash flow increment. But no significance in reducing the political & cultural distance between the host county and China. Gas, as vital low-carbon fossil energy, has its unique preference in the host country’s traits and governance mode. Meanwhile, gas does have brought changes quite differently from the traditional oil business. What’s more, value divergence exists between the official government & the masses even in the same country. Finally, Chinese oil & gas investment prefer “high risk, high return” and a host social hierarchy similar to its own.
With the development of Carbon Capture, Utilization and Storage (CCUS) technology, CO2 injection to improve tight oil recovery has become a new hot spot in the field of tight oil development. At present, horizontal well fracturing, CO2 huff and puff and other technical methods to develop tight oil are not ideal, so it is particularly important to explore new methods to improve tight oil development. In this paper, reservoir cores were selected from a tight oil reservoir in Xinjiang, and the self-developed experimental device of simultaneous well and asynchronous well huff and puff was used to simulate the development process of tight oil, CO2 injection and asynchronous huff and puff and development process under different recovery pressures and production pressures, and to evaluate the displacement characteristics and development effects of asynchronous huff and puff and development process under different CO2 injection. The research shows that the integrated experiment of “same well and different well asynchronous” can better simulate the seepage characteristics and development characteristics of single well and different well stimulation after depletion development. Compared with conventional single well huff and puff method, CO2-injection asynchronous huff and puff can increase recovery by 20%-40%. The key to achieving better development results is to establish a circulating “displacement-soaking-displacement” synergistic system of different wells through pressure recovery, soaking and production process alternately between different wells. The oil transportation distance becomes smaller, the oil saturation field is constantly redistributed, and the diffusion and sweep range of CO2 is expanded. With the increase of pressure difference between “recovery and production”, the harvest effect was significantly improved. The development process can effectively avoid the CO2 backflow process, improve the CO2 utilization rate, and realize the effective storage of CO2.
Electrolytic manganese anode mud is a promising low temperature SCR catalyst. In this study, the effect of Pb and K ion in EMAM on the low temperature was investigated via experimental and DFT method. Pb modification can improve the surface unsaturation so that the oxidation ability of MnO2 is improved. Therefore, ammonia is easily oxidated on the surface of Pb-MnO2. K ion can moderate the surface of MnO2 and lower the energy barrier of dehydrogenation for low temperature SCR process. However, Pb can inhibit N2O formation thereby improve the N2 selectivity.
After industrialization and informatization, the world economy is moving toward “decarbonization”. As two carbon-free fuels, hydrogen and ammonia are attracting increasingly widespread interest around the world. And ammonia and hydrogen are promising and practical alternative energy sources for internal combustion (IC) engines, which may be used to power the next generation of engines due to their zero-carbon footprint. However, the combustion of ammonia produces large amounts of nitrogen oxides (NOx), which pollute the environment. Therefore, it is very significant to control nitrogen oxides (NOx) emissions from spark-ignition (SI) engines. Machine learning (ML) approaches are an alternative analytical tool to three-dimensional (3D) simulations, in-depth experiments and empirical phenomenon models that can accelerate the development of IC engines. The objective of this study was to assess the applicability of ML models in predicting NOx emissions. A calibrated spark-ignition engine fueled with gasoline operating under different conditions was used to provide sufficient data for model training, validation, and testing. The results indicated that the artificial neural network (ANN) and support vector regression (SVR) have good prediction performance and high accuracy, and the prediction accuracy of the RF model is acceptable. In general, ANN and SVR have comparable performance and both models are recommended to predict NOx emissions from ammonia/hydrogen fueled engines. And the prediction performance of the RF model will be less accurate compared to the other two ML models.
The design and preparation of highly effective semiconductor-based photocatalysts for water splitting is an important issue. To accomplish this, a novel Z-Scheme heterojunction for efficient carrier separation and transition is developed. ZnIn2S4/CoSx composite photocatalyst with high photoactivity under visible light irradiation is designed. The ZnIn2S4 exhibits a 3D flower-like microsphere structure, and ZIF-67-derived dodecahedral CoSx nanospheres are tightly embedded in the ZnIn2S4 petals’ gaps. This design allows for fast charge separation and transfer improving the hydrogen generation reaction efficiency considerably. This ZnIn2S4/CoSx composite heterostructures demonstrate outstanding activity with a hydrogen-producing rate of more than 8 mmol g-1 h-1, which is about 6-fold of the pristine ZnIn2S4.
Using China’s smart city construction as a quasi-natural experiment, by matching the data of the Chinese Industrial Enterprises Database, Chinese Enterprises Pollution Emission Database and prefecture-level city data from 2008-2014, this paper evaluates the impact of smart city construction on enterprise pollution emissions using the difference-in-difference method (DID) and propensity score matching DID method (PSM-DID). The empirical results show that smart cities construction effectively promotes the pollution reduction of enterprises, and the estimation results based on the PSM-DID method show robust. The mechanism investigation shows that smart city construction can achieve effective suppression of enterprise pollution emissions through the output effect, technology effect and scale effect.
Due to outstanding properties, the lead perovskites exhibit great potentials in optoelectronic applications, while still facing serious issues due to its high toxicity and instability. This necessitates the development of environmental-friendly lead-free double perovskites nanocrystals with low toxicity and tunable desired properties via size-control. In this review, we present the synthesis routines of lead-free perovskite nanocrystals, followed by detailed discussion of common characterization techniques and potential applications. This work is aimed for providing more insights in the property-tuning and synthesis of high-quality nano-size lead-free perovskites.
The two-step solar thermochemical cycle for hydrogen production is one of the promising ways to alleviate current energy and environmental issues, and achieve carbon neutrality prospects in the future. Traditional graphical analysis methods investigate thermochemical cycles using temperature-entropy and temperature-enthalpy diagrams, without demonstrating the irreversibility of energy conversion processes in the looping of oxygen carriers. To solve this problem, a novel graphical exergy analysis method is proposed for two-step solar thermochemical cycles by illustrating material state in the looping of oxygen carriers and the exergy destruction quantitatively. The analysis process for describing the material state and exergy destruction with a diagram is introduced. The proposed graphical exergy analysis method is used to investigate a typical case of a solar ZnO/Zn two-step thermochemical cycle. The results show that the use of the inert sweeping gas during reduction to reduce the partial pressure of oxygen product to obtain a lower reduction temperature causes serious irreversibility. The proposed graphical exergy analysis method provides a useful tool for analyzing solar thermochemical cycles.