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Having read previous literature about vortex pump, we noticed that mechanisms of circulating flow and its relationship with energy transition remain unclear yet. However, this mechanism, which should be clarified, significantly influences the pump’s efficiency. To comply with the aim of investigating it, the 150WX-200-20 type pump is selected as study object in our present work.

Numerical simulation is conducted to formulate interactions between flow rate and geometric parameters of circulating flow with certain types of blade while experiments on inner flow are served as a witness to provide experimental confirmation of numerical results. Based on these, we coupled some parameters with the pump’s external performance to study their internal connections.

It is concluded that separatrix between circulating flow and other turbulent forms is not that clear under low flow rate. With flow increases, hydraulic losses coming of it will be dominant within the front chamber. Besides, we analogized circulating flow to vortices so as to make a quantitative analysis on its progressive evolution with changing flow, and vortices speaking for circulating flow can be divided into two groups. One is called main circulating flow vortex (hereinafter referred to as MCFV), which occurs all the time while subsidiary circulating flow vortices (hereinafter referred to as SCFV) appear in certain conditions. This context discusses the primary phase of our work with intent to follow up further with circulating flow characterized by vortices (hereinafter referred to as CFV). We confirmed that MCFV Vortex 1 (Vor1) directly influences the efficiency while SCFVs only play helping. As the flow goes to the given working condition, fluids in this pump tend to be steady with the size of CFVs getting larger and their shape being regular. Meanwhile, for MCFV Vor2 and Vor4, their geometric parameters are the key factors for efficiency. When CFVs become steady, they absorb other vortices nearby, as they have higher viscosity with the efficiency reaching its maximum.

The research results explore a new way to measure the circulating flow and help work out the causation of this flow pattern, which may be used to improve the vortex pump’s efficiency.

Global climate change is a serious threat to the survival and development of mankind. Reducing carbon emissions and achieving carbon neutrality are the keys to reducing greenhouse gas emissions and promoting sustainable human development. For many countries, taking China as an example, the electric power sector is the main contributor to the country’s carbon emissions, as well as a key sector for reducing carbon emissions and achieving carbon neutrality. The low-carbon transition of the power sector is of great significance to the long-term low-carbon development of the economy. Therefore, on the one hand, it is necessary to improve the energy supply structure on the supply side and increase the proportion of new energy in the total power supply. On the other hand, it is necessary to improve energy utilization efficiency on the demand side and control the total primary energy consumption by improving energy efficiency, which is the most direct and effective way to reduce emissions. Improving the utilization efficiency of electric energy and realizing the low-carbon transition of the electric power industry requires synergies between the government and the market. The purpose of this study is to investigate the individual and synergistic effects of China’s low-carbon policy and the opening of urban high-speed railways (HSRs) on the urban electricity consumption efficiency, measured as electricity consumption per unit of gross domestic product (GDP).

This study uses a panel of 289 Chinese prefecture-level cities from the years 1999–2019 as the sample and uses the time-varying difference-in-difference method to test the relationship between HSR, low-carbon pilot cities and urban electricity consumption efficiency. In addition, the instrumental variable method is adopted to make a robustness check.

Empirical results show that the low-carbon pilot policy and the HSR operation in cities would reduce the energy consumption per unit of GDP, and synergies occur in both HSR operated and low-carbon pilot cities.

This study has limitations that would provide possible starting points for future studies. The first limitation is the choice of the proxy variable of government and market factors. The second limitation is that the existing data is only about whether the high-speed rail is opened or not and whether it is a low-carbon pilot city, and there is no more informative data to combine the two aspects.

The findings of this study can inform policymakers and regulators about the effects of low-carbon pilot city policies. In addition, the government should consider market-level factors in addition to policy factors. Only by combining various influencing factors can the efficient use of energy be more effectively achieved so as to achieve the goal of carbon neutrality.

From the social perspective, the findings indicate that improving energy utilization is dependent on the joint efforts of the government and market.

The study provides quantitative evidence to assess the synergic effect between government and the market in the low-carbon transition of the electric power industry. Particularly, to the best of the authors’ knowledge, it is the first to comprehend the role of the city low-carbon pilot policy and the construction of HSR in improving electricity efficiency.

The purpose of this paper is to explore the nature of rural energy transition in cooking options in India. Although India is aiming to achieve a double-digit economic growth, a large share of rural households still rely on firewood for cooking which not only has serious repercussions of increasing indoor pollution but also has a concomitant adverse effect on women and child morbidity and mortality. However, transition to clean energy options like improved cookstoves for these households may not be necessarily linear. It is often driven or resisted by latent factors such as caste, trust, social capital, information flow, social positioning of clusters that are deeply embedded in the social and cultural norms and values specific to local rural contexts. This has been shown in the present case study that pertains to eight villages in the remote and deprived Purnea district of Bihar and the need for internalizing them in the macro energy policymaking has been established in the paper.

The paper applies a macro foundation research that is complemented by micro foundation tools of fuzzy cognitive mapping-based mental model framework to achieve the purpose of the study. Focused-group discussions and interviews are also conducted to establish the narrative of the paper.

Caste, socio-political position, asset structure, remoteness, culture and technology access affect rural households’ decision making capability that is related to shifting from using the traditionalmeans of firewood and biomass based traditional cookstoves for cooking to adopting improved clean cooking stoves which will enable the transition toward the use of clean rural energy in the eight villages in Bihar chosen for this study.

The findings of the paper have larger implications for the broader macro energy policymaking in the country by taking into account the non-linear, latent factors of village contexts.

The research will help energy policymakers in decision-making and will guide the implementation process of national- and state-level policies on rural energy transition in India.

The findings of the paper will help the smoother implementation of national- and state-level rural energy transition policies for cooking, creating developmental dividends for rural Indian households.

The research is new with regard to the application of non-deterministic fuzzy cognitive mapping-based mental model approach to contribute to the country’s national- and state-level rural energy transition policies.

This paper aims to look at the dilemma of promoting sustainable energy transition in post-socialist countries while containing social and economic implications, focusing on the case of Serbia. The aim is to analyse Serbian energy status taking into account historical factors, to analyse barriers that are hindering transition and to identify leapfrogging potential for the sustainable energy development of the country.

Energy transition and leapfrogging potential have been qualified and quantified by indicators, the own calculations and policy analysis to identify barriers to sustainable energy.

The country has vast potential for leapfrogging in energy transition, yet continues the gradualist approach based on several policy barriers to the process. The analysis shows six barriers related to low energy price, high energy intensity, prioritization of energy security, inadequacy of utilization of renewable sources, lack of policy coherence and dependency on external funding. However, these barriers could be overcome with an energy policy emphasizing leapfrogging potential. As is pointed out in the conclusion, this should be based on the difference between EU-28 average indicators, discrepancy between use and availability of renewable energy, potential for regional cooperation in the energy sector and under-used skills and participation.

The paper discusses energy transition in its historical context, arguing that it has to be considered as comprehensively with societal implications and effects, thus creating useful knowledge for other post-socialist countries in current and future transitions.

This paper discusses logistics service providers' (LSPs’) energy efficiency initiatives for sustainable development, both from an evolutionary perspective and based on a framework consisting of actions, processes (i.e. at the operations interface) and services (i.e. at the customer interface).

Following a qualitative research design, semi-structured interviews were conducted with sustainability managers at LSPs and the data were analysed via inductive coding. Based on the results and the literature, the authors developed a maturity model for LSPs' transitions to environmental sustainability.

LSPs' sustainable development occurs via operational processes, services at the customer interface, and actions that support those processes and services. Energy efficiency efforts are characterised by process depth that helps LSPs to align with their customers' energy efficiency improvement processes. While services related to energy efficiency connect LSPs and their customers, actions in support vary depending on the logistics activities in which LSPs participate.

Further research is needed to test and verify the maturity model and to clarify the interdependency of its three dimensions.

By categorising energy efficiency initiatives and proposing a maturity model for LSPs' sustainable development via energy efficiency, the authors have developed a tool for logistics actors to assess their progress towards improved sustainability.

The paper contributes to the literature by providing a three-pillar framework to understand the sustainability transitions of LSPs through energy efficiency. Developing a maturity model using this framework also contributes to the literature with an approach to assess sustainability advancement in the logistics industry.

Higher economic growth accompanied by rising energy demand poses severe challenges to the long-term environmental sustainability of E7 economies, including Brazil, China, India, Indonesia, Mexico, Russia and Turkey. Thus, this paper explores the influence of foreign direct investment (FDI) inflows on energy diversification for E7 economies.

The dataset is panel data for emerging seven (E7) economies, covering the period 1992–2017. The empirical investigation relies on econometric techniques: panel cointegration test and panel autoregressive distributed lag model.

The findings reveal that energy diversification and FDI inflows are cointegrated. In the long run, higher FDI inflows encourage energy diversification, but energy efficiency improvements discourage energy diversification. In the short run, the effects of FDI inflows on energy diversification vary across E7 economies, highlighting the role of country-specific factors in determining the short-run influence of FDI inflows on energy diversification.

The findings suggested that FDI policies should encourage the adoption of nonconventional energy resources to stimulate energy diversification in E7 economies. Besides, better coordination between energy diversification and energy efficiency policies is required in the long run for a successful transition towards low-carbon economy goals.

This study is a unique empirical exercise that uncovers a cointegrating relationship between energy diversification and FDI inflows for E7 economies. Moreover, the analysis provides homogenous long-run and heterogeneous (country-specific) short-run coefficient estimates for the effect of FDI inflows on energy diversification.

From the 1990s to the present, decision-makers around the world have sought to identify the most appropriate legal framework to support the energy transition. This research aims to analyze the institutional dynamics of renewable energy promotion, focusing on regulatory aspects at the European and national level and emphasizing the case of Romania through several comparative approaches. In the context of the conflict in Ukraine, we focused on the issue of coal, which was reconsidered given the dependence of some European countries on this resource. The main research methods used in this study are comparative analysis and analysis of chronological information in a historical context, with correlations being made. The study was structured in three stages, the first from the 1990s until the European Energy Union formation, the second during the COVID-19 pandemic, and the third from the emergence of the conflict in Ukraine, which determined the recalibration of previously adopted measures. Starting from the hypotheses formulated and considering the regulatory scenario conducive to the transfer of public funds to achieve climate neutrality, the results of the study show the fact that, at this stage of the research, the states of the European continent are determined to fight for zero carbon by 2050. One result we found interesting is that almost a year after the outbreak of the conflict in Ukraine, less than a quarter of European states have moved past their assumed deadline for phasing out coal in the national mix.

Optimization of energy planning for growth and sustainable development has become very important in the context of climate change mitigation imperatives in developing countries. Existing models do not capture developing country realities adequately. The purpose of this paper is to conceptualizes a framework for energy strategy optimization of the Indian energy sector, which can be applied in all emerging economies.

Hierarchical multi‐objective policy optimization methodology adopts a policy‐centric approach and groups the energy strategies into multi‐level portfolios based on convergence of objectives appropriate to each level. This arrangement facilitates application of the optimality principle of dynamic programming. Synchronised optimization of strategies with respect to the common objectives at each level results in optimal policy portfolios.

The reductionist policy‐centric approach to complex energy economy modelling, facilitated by the dynamic programming methodology, is most suitable for policy optimization in the context of a developing country. Barriers to project implementation and cost risks are critical features of developing countries which are captured in the framework in the form of a comprehensive risk barrier index. Genetic algorithms are suitable for optimization of the first level objectives, while the efficiency approach, using restricted weight stochastic data envelopment analysis, is appropriate for higher levels of the objective hierarchy.

The methodology has been designed for application to the energy sector planning for India's 12th Five Year Plan for which the objectives of faster growth, better inclusion, energy security and sustainability have been identified. The conceptual framework combines, within the policy domain, the bottom‐up and top‐down processes to form a hybrid modelling approach yielding optimal outcomes, transparent and convincing to the policy makers. The research findings have substantial implications for transition management to a sustainable energy framework.

The methodology is general in nature and can be employed in all sectors of the economy. It is especially suited to policy design in developing countries with the ground realities factored into the model as project barriers. It offers modularity and flexibility in implementation and can accommodate all the key strategies from diverse sectors along with multiple objectives in the policy optimization process. It enables adoption of an evidence‐based and transparent approach to policy making. The research findings have substantial value for transition management to a sustainable energy framework in developing countries.