• Energy Research
• 2021-2025close
• CN close
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• Tsinghua University close

The greatest sustainability challenge facing humanity today is the greenhouse gas emissions and the global climate change with fossil fuels led by coal, natural gas and oil contributing 61.3% of global electricity generation in the year 2020. The cumulative effect of the Stockholm, Rio, and Johannesburg conferences identified sustainable energy development (SED) as a very important factor in the sustainable global development. This study reviews energy transition strategies and proposes a roadmap for sustainable energy transition for sustainable electricity generation and supply in line with commitments of the Paris Agreement aimed at reducing greenhouse gas emissions and limiting the rise in global average temperature to 1.5°C above the preindustrial level. The sustainable transition strategies typically consist of three major technological changes namely, energy savings on the demand side, generation efficiency at production level and fossil fuel substitution by various renewable energy sources and low carbon nuclear. For the transition remain technically and economically feasible and beneficial, policy initiatives are necessary to steer the global electricity transition towards a sustainable energy and electricity system. Large-scale renewable energy adoption should include measures to improve efficiency of existing nonrenewable sources which still have an important cost reduction and stabilization role. A resilient grid with advanced energy storage for storage and absorption of variable renewables should also be part of the transition strategies. From this study, it was noted that whereas sustainable development has social, economic, and environmental pillars, energy sustainability is best analysed by five-dimensional approach consisting of environmental, economic, social, technical, and institutional/political sustainability to determine resource sustainability. The energy transition requires new technology for maximum use of the abundant but intermittent renewable sources a sustainable mix with limited nonrenewable sources optimized to minimize cost and environmental impact but maintained quality, stability, and flexibility of an electricity supply system. Technologies needed for the transition are those that use conventional mitigation, negative emissions technologies which capture and sequester carbon emissions and finally technologies which alter the global atmospheric radiative energy budget to stabilize and reduce global average temperature. A sustainable electricity system needs facilitating technology, policy, strategies and infrastructure like smart grids, and models with an appropriate mix of both renewable and low carbon energy sources.

In recent years, subsynchronous control interaction (SSCI) has frequently taken place in renewable-connected power systems. To counter this issue, utilities have been seeking tools for fast and accurate identification of SSCI events. The main challenges of SSCI monitoring are the time-varying nature and uncertain modes of SSCI events. Accordingly, this paper presents a simple but effective method that takes advantage of intrinsic time-scale decomposition (ITD). The main purpose is to improve the accuracy and robustness of ITD by incorporating the least-squares method. Results show that the proposed method strikes a good balance between dynamic performance and estimation accuracy. More importantly, the method does not require any prior information, and its performance is therefore not affected by the frequency constitution of the SSCI. Comprehensive comparative studies are conducted to demonstrate the usefulness of the method through synthetic signals, electromagnetic temporary program (EMTP) simulations, and field-recorded SSCI data. Finally, real-time simulation tests are conducted to show the feasibility of the method for real-time monitoring.

Malus hupehensis (M. hupehensis), an edible and medicinal plant with significant antioxidant and hypoglycemic activity, has been applied to new resource foods. However, the structural characterization and biological effects of its polysaccharides (MHP) are less known. The optimum extraction parameters to achieve the highest extraction efficiency (47.63%), the yield (1.68%) and purity of MHP (89.6%) by ultrasonic-assisted aqueous two-phase system (ATPS) were obtained under the liquid-to-solid ratio of 23 g/mL, ultrasonic power of 65 W, and ultrasonic time of 33 min. According to the analysis results, MHP was composed of Man, GlcA, Rha, GalA, Glc, Gal, Xyl, Ara, and Fuc, in which Ara and Gal were the main components, and the content of GlcA was the lowest. In in vitro activity analysis, MHP showed a significant antioxidant capacity, and an inhibition activity of α-glucosidase and the advanced glycation end products (AGEs) formation in the BSA/Glc reaction model. MHP interacted with α-glucosidase and changed the internal microenvironment of the enzyme, and inhibited the AGEs formation, which provides more evidence for the antihyperglycemic mechanism of MHP. The results suggest that ATPS is an efficient and environmentally friendly solvent system, and M. hupehensis has broad application prospects in functional foods, healthcare products, and pharmaceuticals.

In recent years, the increased application of inverter-based resources in power grids, along with the gradual replacement of synchronous generators, has made the grid support capability of inverters essential for maintaining system stability under large disturbances. Critical clearing time provides a quantitative measure of fault severity and system stability, and its sensitivity can help guide parameter adjustments to enhance the grid support capability of inverters. Building on previous researches, this paper proposes a method for calculating critical clearing time sensitivity in power systems with a high proportion of power electronic devices, accounting for the new dynamic characteristics introduced by these devices. The current limit and switching control of inverter-based resources are considered, and the critical clearing time sensitivity under controlling periodic orbits is derived. The proposed critical clearing time sensitivity calculation method is then validated using a double generator single load system and a modified 39-bus system.

Abstract TRISO coated particle fuel exhibits statistical variations and large uncertainties in physical configurations and material properties from particle to particle. Besides, the dependence of mechanical behavior and failure mechanism of the coating layer on multiple variables (such as density, porosity, anisotropy, fluence and temperature) further increase the complexity of TRISO fuel performance analysis. Consequently, the particle failure probability would change in a relatively wide range. In this paper, we evaluate the effect of input data uncertainties on particle failure probability. First, uncertainty ranges of input data are determined based on literature review and irradiation conditions. Second, a perturbation study on dimensional parameters and material properties is performed. Finally, variation ranges of failure probability upon different input parameters are determined. Results show that the failure rate is sensitive to kernel diameter, SiC thickness and irradiation-induced material properties.