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Renewable Portfolio Standards (RPS) and carbon emission trading (CET) system are the top-level system design of China's energy low-carbon transformation, which have great strategic significance for realizing the "carbon peak in 2030 and carbon neutrality in 2060". At present, China's tradable green certificates market and CET market are still in the initial stage. The implementation single system may have diverse trials and errors in its initial stage, and the market activity and transaction frequency are low. Therefore, this paper aims to explore whether the synergistic effect between the two systems can effectively promote China's energy low-carbon transformation. This paper establishes the system dynamic model of the synergistic effect between the RPS and CET in China's electricity market to reveal the influence mechanism and the synergistic effect. The results show that: (1) There is a positive synergistic effect between the RPS and CET, which will change with the institutional parameters. (2) The simultaneous implementation of the RPS and CET can effectively stimulate market vitality and promote the development of the renewable energy industry. (3) Higher quota and lower benchmark price can optimize power source structure, and improve social welfare and institutional performance. [ABSTRACT FROM AUTHOR]

Thermal stratification widely exists in large reservoirs, causing significant inflow-outflow temperature difference (IOTD), which goes against the downstream ecology. Reservoir optimal operation has recently been conducted to regulate the outflow temperature, while its effects for cascade reservoirs urgently needed to be illuminated. Taking the typical Xiluodu-Xiangjiaba cascade reservoirs (XXCR) as study case, this paper had built a multi-objective optimal operation model combing the non-dominated sorting genetic algorithm II (NSGA-II) and a hydrodynamic-temperature model, and the total power generation (TPG) and IOTD were simultaneously considered. The effects of different inflow discharge and global warming scenarios were analyzed. This paper showed the following: (1) The IOTD and TPG of XXCR showed a positively linear relationship with the water level of the superior Xiluodu Reservoir (XLD), instead of the inferior Xiangjiaba Reservoir (XJB). (2) The reservoir with larger water volume and depth (such as XLD) determined the thermal structure and hydropower generation in cascade reservoirs, compared with the inferior reservoir (such as XJB). (3) As the inflow discharge or air temperature increased, the slope between the IOTD and TPG in the Pareto front curve increased. The results of this paper could support the ecological operation for cascade reservoir to regulate the outflow temperature. [Display omitted] [ABSTRACT FROM AUTHOR]

In order to improve corn stalk conversion into total reducing sugar effectively, steam-assisted alkaline pretreatment and enzymatic hydrolysis was studied. This result showed that cellulose and hemicelluloses contents in corn stalk were decreased to 7.01% and 4.41% (P < 0.05), and total reducing sugar yield was increased to 335.09 mg/g biomass (P < 0.05), when corn stalk was pretreated with steam and alkali (0.8% NaOH + 1.2% CaO, W/V) for 1.0 h at a ratio of alkaline solution to corn stalk of 5:1 (V/W), followed by enzymatic hydrolysis at 22.5 FPU/g biomass cellulase for 48 h. The synthetical enzymatic hydrolysis conditions of pretreated corn stalk were pH 5.0, 50 °C, 60 filter paper unit (FPU)/g biomass and 48 h reaction time, in which total reducing sugar yield was 358.97 mg/g biomass (P < 0.05). The further response-surface methodology results showed that the total reducing sugar reached 493.74 mg/g biomass under the conditions of 52.39 FPU/g biomass cellulase, 6599.99 U/g biomass β-glucanase and 40 h reaction time. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and pore structure analyses indicated that steam-assisted alkaline pretreatment plus enzymatic hydrolysis were effective in breaking the crystal structure of corn stalk for increasing total reducing sugar yield. • Steam-assisted alkaline pretreatment broke down crystal structure of corn stalk. • Physiochemical pretreatment increased hemicellulose degradation rates. • Enzymatic hydrolysis conditions were optimized by central composite design. • Cellulose and hemicelluose contents were decreased by enzymolysis. • Reducing sugar yield was increased by physiochemical pretreatment plus enzymolysis. [ABSTRACT FROM AUTHOR]

The use of biomass in combined heat and power (CHP) plants with district heating and cooling is necessary for achieving decarbonization targets. While in traditional biomass plants steam temperature is below 520 °C, new developments can lead to ultra-supercritical (USC) designs with steam temperatures of 600 °C. The present study investigates the performance of such plants for covering the heat demands of the aluminum and pulp and paper industrial processes, while also producing district heating and cooling. Plant performance is assessed through sensitivity analyses covering a wide range of heat demand scenarios. In the electricity-only scenarios, the electric and exergetic electric efficiencies of the aluminum/pulp and paper plants are 43.45/44.22% and 38.93/39.62%, respectively. In the CHP scenario, when the heat demand is maximized, the electric, exergetic electric, CHP and exergetic CHP efficiencies of the aluminum/pulp and paper plants are 21.81%/34.32%, 19.54%/31.70%, 92.50%/86.76% and 39.43%/39.01%, respectively. With the integration of cooling, the electric and CCHP efficiencies of the aluminum plant are 21.60% and 89.23%, respectively. Most of the exergy is destroyed during the combustion and steam generation processes, corresponding to 67–70% and 13–16% of the total exergy destruction, respectively. • Development of supercritical CHP plant layouts featuring district heating and cooling. • Process heat integration scenarios for aluminum and pulp and paper processes. • Sensitivity analyses and mapping of plant performance for different heat demands. [ABSTRACT FROM AUTHOR]

The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing its oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil to biodiesel has led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol. [Display omitted] • Bio-additives from the base-catalysed depolymerisation of LignoBoost kraft lignin. • Effect of reaction variables on bio-oil yield and biodiesel oxidation stability. • Oxidation stability of biodiesel increased up to 340% by adding 1 wt% bio-additive. • An integrated biorefinery concept for valorising lignin and glycerol waste streams. [ABSTRACT FROM AUTHOR]

Membraneless microfluidic fuel cell (MMFC) has potential application prospects in micro-devices due to the characteristics of considerable output performance, superior cleanliness and easy miniaturization. Whereas, the performance of MMFC is restricted by the mass transfer of two-phase flow, which manifests as the inefficiency transportation in liquid phase and obstruction of gas phase. This paper proposes a novel sinusoidal corrugated channel (SCC) for MMFC though developing a three-dimensional two-phase model by coupling the multi-physics field to improve the cell performance in mass transfer, and further studies the two-phase flow characteristics of geometric parameters of SCC, including the amplitude A and angular frequency ω. Based on the optimal configuration in A of 0.5 mm and ω of 3 rad s−1, compared with the conventional straight channel, the increase ratios of maximum current density, power density, fuel utilization are 13.69%, 8.39% and 13.72%, respectively. Additionally, the gas volume fraction at the maximum power density decreases by 12.62%. This paper provides new insights and theoretical foundations for the study of MMFC flow field configurations, and furnishes references for the mass transfer intensification. [ABSTRACT FROM AUTHOR]

Global warming has focused attention on how the world produces the energy required to power the planet. It has driven a major need to move away from using fossil fuels for energy production toward cleaner and more sustainable methods of producing renewable energy. The development of offshore windfarms, which harness the power of the wind, is seen as a viable approach to creating renewable energy but they can be difficult to design efficiently. The complexity of their design can benefit significantly from the use of computational optimisation. The windfarm optimisation problem typically consists of two smaller optimisation problems: turbine placement and cable routing, which are generally solved separately. This paper aims to utilise selection hyper-heuristics to optimise both turbine placement and cable routing simultaneously within one optimisation problem. This paper identifies and confirms the feasibility of using selection hyper-heuristics within windfarm optimisation to consider both cabling and turbine positioning within the same single optimisation problem. Key results could not identify a conclusive advantage to combining this into one optimisation problem as opposed to considering both as two sequential optimisation problems. [ABSTRACT FROM AUTHOR]

This paper examines the impact of green finance on environmental performance in developing countries. Using panel cointegration analysis and panel vector error correction model (VECM) to a sample of 76 developing economies from 2010 to 2019, this study confirms that carbon emissions (CO 2) is cointegrated with green finance, real gross domestic product, urbanization, and renewable energy under different specifications and therefore we estimate the long-run relationships among these variables. Specifically, both green finance and renewable energy are found to exert significant and inhibitory effects on CO 2 emissions, reaffirming the necessity to promote green finance and renewable energy. Results from the paper also document the existence of the Environmental Kuznets Curve and the increasing effects of urbanization on CO 2 emissions. Several policy implications and recommendations are drawn from this study. • We examine impact of green finance on environmental performance. • 76 developing economies from 2010 to 2019 are considered. • Green finance and renewable energy exert inhibitory effects on CO 2 emissions. • Results support the existence of the Environmental Kuznets Curve. [ABSTRACT FROM AUTHOR]

The short-term forecast of photovoltaic (PV) power is crucial for the security and economics of power system operations. However, the fluctuation characteristics of the PV power, which are closely related to the meteorological factors, introduce inaccuracies in its forecast. Towards this end, the paper studies the effects of clustering analysis at long time scale and data reconstruction technique at short time scale on capturing PV power fluctuation characteristics. A short-term PV power forecasts method based on multi-scale fluctuation characteristics extraction (MFCE), which employs a path analysis to identify the relevance of meteorological factors with PV power at long time scale and a phase space reconstruction to analyze PV power fluctuation characteristics at short time scale, is proposed in this paper. The proposed MFCE methodology deploys a widely-used extreme gradient boosting (XGBoost) model to output the forecasting results. Both the effectiveness and accuracy of the proposed methodology are verified by using the real data under the conditions of sunny and cloudy days of four seasons compared to traditional methodologies. • The multi-scale fluctuation characteristics are analyzed for PV power forecast. • Identify dominant meteorological factors affecting PV power by path analysis. • The hour-level fluctuation is reduced by using path analysis-based clustering. • The phase space reconstruction is used to reduce the minute-level fluctuation. [ABSTRACT FROM AUTHOR]

Energy process system positively contributes to the energy utilization efficiency, the energy complement, and the construction of a low-carbon sustainable energy system. The multiple energy subsystems are deep interdependent, therefore, significant operational risks exist in the energy process system. To avoid system risk and fulfill operation requirement, we propose the Safety-Index based model predictive control that coordinates the controller design and system safety in this work. The innovation of the method is to integrate the state-space model of process system with advanced controller design while accounting for system safety. Since the state-space model of the energy process system is described by coupled partial differential equations and ordinary differential equations, which leads to difficulties in modeling and solving, the main contribution of this work is to simplify the constrained optimization problem formed by model predictive controller. The paper addresses the compressed air energy storage system as case study. From the numerical simulations of the safety controller performance, it shows that the system safety can be guaranteed by control strategy which realizes the system operation target and reject the system external disturbances, which caused by environmental or operation change. • The paper addresses the modeling and dynamic safety control of compressed air energy storage system. • A control loop for safety operation that consists of controllers, system models, system constraints, and safety index is proposed. [ABSTRACT FROM AUTHOR]

To achieve the carbon peaking and carbon neutrality goals, China promoted county-wide photovoltaic projects (CWPVs) in 2021. A large number of distributed photovoltaic (DPV) installations have expanded the scale of prosumer. It also brings the inequity problem of prosumer, distribution network system operator (DSO) and consumer--DSO and consumer bear the costs such as access cost and depreciation of stock investment caused by DPV access. Combined with China's current electricity tariff system and the promotion of photovoltaic scale development, this paper proposes a standby fee model based on the principle of "beneficiary apportionment". In this model, the standby fee mechanism for self-owned power plants is applied to DPV to reduce the implementation cost of the mechanism, and the principle of "beneficiary apportionment" is adopted to ensure the profitability of DPV. This paper takes the CWPV in Hunan Province, China as an example, calculates the standby fee under various electricity metering methods, and determines the most appropriate standby fee by considering factors such as output uncertainty of DPV. Finally, the difficulties in the implementation of standby fee are sorted out. [ABSTRACT FROM AUTHOR]

The present paper analyses the evolution of renewable energy generation in the European Union through a decomposition analysis based on the Index Decomposition Analysis together with the Logarithmic Mean Divisia Index within the EU27 between 2000 and 2020. A four factors decomposition approach is considered for decomposing the total RES generation and a five factors model is employed to decompose the carbon emissions. Furthermore, a focus on wind and solar photovoltaic generation is introduced through a four factors decomposition calculated in the period 2010–2020. The most influential factors affecting the RES generation trend in the period 2000–2020 are the RES share and energy efficiency wich determined an increase of 1841 TWh and a decrease of 635 TWh respectively. Variations of carbon emissions are mostly affected by the energy intensity, namely the amount of energy necessary to produce one unit of GDP, which determined a reduction of 1040 Mt. Through the decomposition analysis, the paper successfully identifies the specific drivers supporting RES development and controlling carbon emissions, thus adequate policy measures can be designed to reach planned targets. • LMDI methodology is used to study decomposition of RES generation in EU. • Technical and socio-economic factors are highlighted by using 4 or 5 factors identity. • Technical factors have the main impact on the increase in RES generation. [ABSTRACT FROM AUTHOR]

With more and more micro-generation being connected to the low-voltage network, it becomes increasingly difficult for operators to anticipate the loading condition of their networks. Several facts concur with such difficulty, one being the frequent lack of knowledge about the generation component of the measured net load. The generation component is typically more volatile than the natural load and is impossible to predict without reliable information on the grid's renewable installed capacity. In this context, the objective of this paper is to propose a non-intrusive methodology to estimate distributed generation' installed capacity. Relying upon net-load historical data obtained at the secondary substation level and on historical meteorological data, the paper presents algorithms that proved effective in determining an approximation of the renewable embedded capacity. The accuracy and effectiveness of the proposed algorithms are illustrated in the paper with real data, for real use cases in the distribution systems. • New non-intrusive methodology to estimate PV capacity installed in LV distribution grids. • Disaggregation of net load profiles into demand and PV generation. • Use of disaggregated profiles for improved LV net-load forecast. [ABSTRACT FROM AUTHOR]

The development of clean energy has made the green finance market attractive to investors, but existing studies lack an analysis of the impact of uncertain environmental shocks on the volatility of green finance stocks. This paper focuses on the impact of major events on clean energy stock returns by using a mixed-frequency model. Specifically, to identify asymmetric effects and extreme information spillovers, we construct extreme positive returns/positive returns and extreme negative returns/negative returns, respectively. The in-sample findings suggest that asymmetric effects and extreme shocks contain valid information about future clean energy stock price volatility. The out-of-sample analysis shows that the extended model can successfully predict the volatility of clean energy stock markets. More importantly, the extended model can generate predictive gains from both statistical and economic aspects. This study can provide a reference for implementing and adjusting energy policies, which is important for optimizing the energy structure and developing the green energy industry. • This paper investigates the performance of the extended GARCH-MIDAS model. • Extreme shocks have different effects on the clean energy stock markets volatility. • The model with long and short-term extreme shocks has better predictive power. • The predictability of extreme shocks is robust by several robustness checks. [ABSTRACT FROM AUTHOR]

Sigma Energy has performed its foremost prototype tests of a scaled wave energy converter (WEC) in a real sea environment. The prototype was a point absorber with a circular buoy, a mechanical power take-off (PTO) system and a counterweight, moored to the seabed as a tension leg platform with three equal tendons. In these extensive experiments, numerous device characteristics were measured and analysed. The paper presents these sea trials, focusing on the power and efficiency of the device. The power has been calculated from the data recorded at 6 locations along the PTO system. In that way, a decay of capture width ratio (CWR) from the one absorbed from the waves to the one delivered to the electrical network was found and analysed. Also, losses of the main elements of the PTO system were defined, calculated and ranked. Optimal sea and loading conditions were indicated, giving the maximal values of the efficiencies. These optimal conditions are physically explained, and the challenges in their prediction are discussed. In addition to the results of numerous 20-min tests, the paper presents the long-term average values of the efficiencies, covering all the tests performed, and accounting for the probabilities of different sea conditions. [ABSTRACT FROM AUTHOR]

Reliability of blades has a profound impact on both serviceability and safety of offshore wind turbines. Reliability estimation of wind turbine blade is a complex and time-consuming problem with multi-physics coupling and multi-failure modes correlation. Developing physics-of-failure modeling and reliability analysis methods with high efficiency and accuracy is a long-term challenge. In this work, a high availability and cost-effectiveness reliability estimation framework for offshore wind turbine blade by combining transfer learning (TL) and direct probability integral method (DPIM) is proposed. Extensive performance simulation of offshore wind turbine blade is a complex and necessary task, this paper develops a new adaptive sampling strategy to improve the validity of sample selection in the design space; On this basis, a physics-of-failure surrogate modeling approach is proposed by introducing TL method to fuse two kinds of multi-physics coupling analysis data, then the performance of all critical loads can be predicted efficiently in advance to provide a reliable design; Further, this paper provides an efficient reliability estimation method for offshore wind turbine blades by combining DPIM and surrogate model. Finally, the validity of the proposed approach is illustrated by numerical example and offshore wind turbine blade reliability estimation. The proposed framework provides a cost-effective alternative to higher loads simulation efforts and safety factors selection. • A new adaptive sampling strategy for multi-failure modeling is proposed. • A failure modeling method is developed for multi-physics coupling system. • A reliability estimation method is proposed based on Dirac delta function. [ABSTRACT FROM AUTHOR]

CO 2 sequestration is an effective technology for reducing greenhouse gas effect. To ensure the safety, assessment of well applicability should be conducted before CO 2 sequestration. However, current studies mainly focus on identifying which barrier has the highest risk of leakage rather than selecting a target well for injection in specific geological formation. To further investigate, this paper proposes well applicability assessment method combining reservoir and wellbore properties together for CO 2 sequestration. A novel assessment system combing Fuzzy comprehensive evaluation and Analytic hierarchy process has been established. Twenty-nine indexes subjected to seven categories (i.e., formation, well, cement sheath, cementing quality, casing, tubing, and wellhead properties) are taken into consideration. The weighting factors of these seven categories are 0.0673, 0.0552, 0.096, 0.1537, 0.2283, 0.2637 and 0.1369, respectively. Tubing and casing properties have the greatest influence on safety injection. Furthermore, the proposed system has been applied to S gas reservoir, China. Results show that Wells #P1 and #P2 are suitable for injection. Since more comprehensive indicators are considered comparing with previous studies, the results are more accuracy and objective. The findings of this paper could help efficiently and effectively evaluating well applicability for CO 2 sequestration and reducing the risk of CO 2 leakage. [ABSTRACT FROM AUTHOR]

Non-interconnected island systems around the globe present a great variety and substantial particularities regarding the methods applied in generation scheduling, primarily under high renewable energy sources penetration levels. Under such conditions, one of the main challenges in island systems is the coherent treatment of intermittent renewable generation and the implementation of robust unit commitment and economic dispatch methodologies, seeking to achieve high RES absorption rates, least cost scheduling, and system security. In this paper, an extensive and in-depth literature review is undertaken to identify the generation scheduling principles and methods applied in island systems experiencing high renewable penetrations. Principal features of electricity markets in islands are highlighted, state-of-the-art unit commitment and economic dispatch models suitable for such applications are identified, and their advantages and limitations are discussed. The effect of renewables uncertainty on the islands' scheduling is analyzed, especially regarding the classification and quantification of system operating reserves to enhance operational security and system stability. Given the isolated nature and limited inertia of islands, very high RES penetration targets may impact their ability to survive severe contingencies, a topic also addressed in this paper, extending the review to include literature on frequency-related dynamic phenomena for isolated systems. • An overview of generation scheduling principles for island systems is presented. • Techniques available to deal with intermittent RES uncertainty are discussed. • A taxonomy of operating reserves adopted in the literature is performed. • A survey on island systems dynamics under high RES penetrations has been conducted. [ABSTRACT FROM AUTHOR]

This paper probes the effectiveness of competitive industrial performance (CIP) and renewable energy in enhancing load capacity factor in top-10 CIP economies for the period 1990–2018. We run panel econometric techniques that address cross-sectional dependence, endogeneity and heterogeneity to provide policy recommendations with the applications of industry, innovation, and infrastructure (SDG 9), which is linked to affordable and clean energy (SDG 7) and climate action (SDG 13). In the empirical analysis, two different environmental quality indicators such as CO 2 emissions and load capacity factor are used. While cointegration between variables cannot be detected in the emissions model, evidence for the existence of cointegration is presented in the load capacity factor model. The findings in the paper suggest that economic growth and competitive industrial performance adversely impact environmental quality, while renewable energy consumption and human capital can improve load capacity factor. The result shows that human capital and renewable energy consumption can be strong tools for stimulating load capacity factor in top-10 CIP economies. Countries with high competitive industrial performance need to return to a green economy without losing their competitiveness. • SDG-based environmental policies was presented for the top-10 CIP economies. • A battery of second generations methods was employed. • Investigating the impacts of Competitive industrial performance on environmental quality. • Competitive industrial performance has a negative impact on environmental quality. [ABSTRACT FROM AUTHOR]

Tidal currents are renewable and predictable energy sources that could prove fundamental to decrease dependency from fossil fuels. Tidal currents, however, are highly unsteady and non uniform, resulting in undesirable load fluctuations on the blades and the drive train of turbines. A passive morphing blade concept capable to reduce the load fluctuations without affecting the mean loads has recently been formulated and demonstrated with numerical simulations (Pisetta et al., 2022). In this paper, we present the first demonstration of this morphing blade concept, through experimental tests on a 1.2-m diameter turbine. We show that fluctuations in the root-bending moment, thrust and torque are consistently reduced over a broad range of tip-speed ratios. This work also highlights some critical design aspects of morphing blades. For instance, it is showed that the friction resistance can substantially decrease the effectiveness of the system and thus must be minimised by design. Overall this paper demonstrates for the first time the effectiveness of morphing blades for tidal turbines, paving the way to the future development of this technology. • We test a model-scale tidal turbine equipped with a passively pitching blade. • The blade angle of attack decreases with an increase in instantaneous loads. • This does not affect the time-averaged power generated by the tidal turbine. • Torque and thrust fluctuations are reduced by at least 40% at on-design conditions. • Friction on the turbine shaft affects performance and must be minimised. [ABSTRACT FROM AUTHOR]

In order to reveal the role moisture content in the dense molding process of Salix psammophila, a discrete element model was established by PFC3D. Under the conditions of temperature of 100 °C and pressure of 0–180 kN, three groups of uniaxial compression simulation with different moisture content were done, and experiments are used to prove the feasibility of using discrete element to simulate the influence of moisture content on the dense molding of Salix psammophila. The significance of this paper on the influence of moisture content on the densification of salix psammophila is as follows: There are abundant shrub resources in northwest China. Effective control of moisture content is conducive to utilization of shrub biomass resources and improvement of product quality; Many scholars have studied the influence of moisture content on forming fuel from the same perspective, but this paper expounds the influence of moisture content on the dense forming of Salix psammophila from the perspectives of force, fracture, energy, etc., providing a reference for the study of the role of moisture content. [ABSTRACT FROM AUTHOR]

The growing carbon crisis threatens sustainable development. This paper verifies that the rise of green finance contributes to overcoming this challenge. The benchmark results show that green finance can directly drive decarbonization of the economy. High-level openness, government support, human capital and urbanization are prerequisites of this effect, and green finance is more effective in promoting decarbonization in areas with high carbon intensity. Moreover, green finance drives economic decarbonization by promoting economic growth, technical innovation, industrial upgrading, and renewable energy transition. Internet availability, financial level and higher education have moderating roles in boosting this effect. Furthermore, the implementation of green finance policy also contributes to decarbonization. The robustness of the basic result is proven with several methods, thus strengthening the reliability of the basic conclusion in this paper. Based on the above main findings, targeted policy recommendations concerning how to further develop green finance are proposed in this paper. • Green finance can directly drive economic decarbonization. • Some high-level external circumstances are the prerequisite of that effect. • Green finance can drive economic decarbonization through mediating paths. • Moderating paths are Internet availability, financial level and education. • Green finance policy makes contributions to the economic decarbonization. [ABSTRACT FROM AUTHOR]

The primary purpose of this paper is to investigate the effects of two variables, trade openness and the issuance of green bonds, on the consumption of renewable energy in Southeast Asian countries. Quarterly data throughout 2016–2021 in the framework of the panel data method were used for the case of 6 selected countries (Indonesia, Malaysia, Philippines, Singapore, Thailand, and Vietnam). The results confirmed that the issuance of green bonds is an effective green financing tool in the implementation of the development policy of the deployment of renewable energy in the countries of the Southeast Asian region. The degree of trade openness has a driving effect on increasing renewable energy consumption due to the increased possibility of transferring green technologies and increasing interactions with leading countries in the field of sustainable development. The typical standard of green bonds, green scientific network (GSN), the development of e-commerce, and the publication of digital green papers are the recommended practical policies of this research. • Green bond is an effective tool to increase of deployment of renewable energy. • Trade liberalism increases the deployment of renewable energy. • Green R&D is a leading factor in the field of clean energy consumption. [ABSTRACT FROM AUTHOR]

In this paper, a three inputs six-phase Interleaved Boost Converter (IBC) is proposed and designed for Fuel Cell (FC) systems, where the different Polymer Electrolyte Membrane Fuel Cells (PEMFC) systems are employed to validate. Considering that the selected converter is composed of three two-phase IBCs connecting in parallel, it shows many superiorities in topology, such as simple structure, high scalability/flexibility, easy maintenance and good fault-tolerant ability. The whole design process containing the selection of phase numbers, parameters design of the converter's components and steady-state operations analysis is focused in this paper. To further validate the correctness of the designed converter, a test bench is established based on dSPACE1104 , where the issue of the implementation of six-PWM signals from dSPACE1104 is analyzed and a feasible solution is proposed. Last, experimental results are shown by performing the load disturbance rejection, the variable reference voltage and the PEMFC system's failure based on the designed Double-Loop Super-Twisting Sliding Mode (DL-STSM) controller. • Three inputs six-phase interleaved boost converter is designed for fuel cell systems. • The designed converter shows high scalability and good fault-tolerant ability. • A solution is proposed to address the achievement of six-PWM signals in dSPACE1104. • Experimental verification of the designed converter with different fuel cell systems. • Load disturbance rejection, variable reference voltage and FC failure are validated. [ABSTRACT FROM AUTHOR]

This paper collects monthly data for the United States from January 2005 to April 2021 and develops a time-varying parameter vector autoregressive model with stochastic volatility (TVP-SV-VAR) model to investigate the time-varying relationship between climate policy uncertainty, oil prices, and renewable energy consumption. In addition, this paper discusses the dynamic impact of climate policy uncertainty on five types of renewable energy consumption. Our results show that the relationship between them is time-varying. In most periods, climate policy uncertainty positively affects oil prices in the short and medium term, and positively affects total renewable energy consumption in the short and long term. In addition, the impact of climate policy uncertainty on the consumption of the five types of renewable energy is heterogeneous. The results of the robustness tests indicate that our results are robust and our study has important implications for the development of relevant policies. [ABSTRACT FROM AUTHOR]

A relatively simple, optimal, and robust nonlinear Sliding Mode Control (SMC) is developed in this paper for a novel nonlinear Wave Energy Converter (WEC). Giving that deriving an optimal control for a complex system is very cumbersome or nearly impossible, an SMC (purely switching only) is thus implemented with the sliding surface defined in an optimal sense. Despite it is simple, the optimality of this control is proved by using a new equivalent control analysis mathematically and also demonstrated numerically. In addition, the robustness of the control is shown mathematically with Lyapunov analysis and by simulations with uncertainties. The main contributions of this paper are: (1) a novel Sliding Mode Control is developed which is simple, optimal, and robust;(2) the robustness and optimality of the proposed control are both proved mathematically and verified numerically; (3) a weakly nonlinear model is developed for a nonlinear WEC which is utilized to validate the performance of the proposed nonlinear control. The numerical simulations are then conducted on a weakly nonlinear model developed for the nonlinear WEC. The results show the robustness and optimality of the proposed control (compared with a nonlinear damping control) subject to uncertainties and nonlinearities. [ABSTRACT FROM AUTHOR]

Thermochemical processes to convert bio-wastes into valuable products and bioenergy have been extensively studied in the literature. Experimental and, to a lesser extent, rigorous simulation papers concerning these processes have been widely considered and discussed in the literature. Nonetheless, there is still a gap to fill in providing a fast and reliable simulation scheme. In this paper, an efficient simulation strategy, combining the free-software COCO simulator for the bio-waste slow pyrolysis coupled with commercial SimaPro code to carry out the Life Cycle Assessment (LCA), was applied. The pyrolysis product yields at 673, 773, and 873 K were well predicted using mass and energy balances and a proposed reaction scheme from the literature. Simulations were validated using experimental data previously reported. The highest yield was 53.7% for biochar (673 K – stalk of white grape), 32% for bio-oil (773 K - marc of red grape), and 56.3% for gas (873 K - marc of white grape). The results from LCA and cumulative exergy demand (CExD) were useful to detect and reduce environmental impacts in previous stages of the process. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, nano hexagonal boron nitride grafted with silane coupling agent (APTES-hBN) is selected to modify the natural ester, conducts thermal aging tests on the modified natural ester insulating oil and explores the mechanism of the nanoparticles on the improvement of natural ester properties from a microscopic perspective combining with molecular dynamics. The experimental results show that the addition of Nano APTES-hBN inhibited the production of acids in oil-paper insulating, leading to a corresponding decrease in the number of polar molecules in the oil. Compared with crude oil, the acid value and dielectric loss factor in the modified oil are reduced by 8.4% and 43.8%, respectively at the end of aging, and the rate of increase is smaller. Through its mechanism study, it is found that the addition of Nano APTES-hBN results in a tighter interfacial bonding between oil and paper insulation, and the adsorption energy of modified natural ester insulating oil to H 3 O+ is greater. The addition of Nano APTES-hBN introduced a large number of electron traps, providing a medium for the transition of valence electrons. At the same time, there are hydroxyl groups with strong electrostatic potential on Nano APTES-hBN, which have strong adsorption effect on charged particles. In addition, the Nano APTES-hBN is able to form hydrogen bonds with acids, which slows down the promotion of hydrolysis of ester molecules by acids, and thus improves the thermal stability of the modified natural ester insulating oil. [ABSTRACT FROM AUTHOR]

In building integrated PV/T applications, the utilization of linear Fresnel micro-concentrators could promote solar energy harvesting efficiency. For the consideration of low wind load and building aesthetics, the height of the concentrator is invariably kept in a small range, resulting in severe optical blocking between mirrors. In this paper, two offset-axis mirror models are introduced to promote the optical efficiency of the micro-concentrator. The rotating axis of the mirror in the former model is not located on the symmetrical axis of the mirror but is offset to one side of the mirror. The later model is a rod offset-axis mirror with the axis offset to the outside of the mirror by a rod. These offset-axis mirrors allow the mirrors farther away from the receiver to possess a higher position for larger angular rotation, thus reducing the blocking between mirrors. Thereafter, mathematical models were established to obtain the key parameters of each mirror at different axis positions, and the influence of the axis position on the optical performance of the micro-concentrator was analyzed. The results revealed that both kinds of offset-axis mirrors could significantly improve the ground utilization ratio of the micro-concentrator and realize a more compact micro-concentrator design. In comparison with the layout scheme with the conventional central-axis mirrors, the ground utilization ratio of micro-concentrator with a hybrid layout of side-axis mirrors and rod offset-axis mirrors was improved by 28%. The optical simulations based on the Monte Carlo method revealed that a micro-concentrator with a hybrid layout of side-axis mirrors and rod offset-axis mirrors could promote the solar harvesting efficiency by 56.8% compared to the conventional central-axis mirror layout, regardless of direct normal sunlight or large angle inclined sunlight. The concept and calculation methodology of offset-axis mirror presented in this paper could reduce the thickness of linear Fresnel micro-concentrators in the design and improve their concentrating efficiency, which would lay the solid foundation for the wide application of micro-concentrators in the building domain. [ABSTRACT FROM AUTHOR]

In recent decades, the role of green energy in realizing green transition and addressing environmental degradation needs to be brought into full play. To promote green energy development in China, this paper examines the relationship among green economic growth, green finance, and green energy (3G) between 2011 and 2019. The heterogeneous, asymmetric, and mediation impact relationship that exists in the 3G nexus is also explored in this study. Accordingly, the results suggest that: (1) Green economic growth and green finance are positively associated with green energy, and the impact is heterogeneous on different types of green energy and in different regions; (2) the impact of green economic growth on green energy are asymmetric, while that of green finance is consistent; and (3) green innovative technology is an effective mediator between green economic growth and green energy, while the investment effect is not significant. This paper contributes to formulating several reasonable policies for improving the green energy industry and achieving sustainable development. It is essential to give full play to the transformation of green achievements to enhance the role of green economic growth in promoting the green energy industry. • This study explores 3G nexus (green economic growth, finance, and energy (GRE)) in China. • The heterogeneity, asymmetry, and mediating mechanism are further analyzed. • Green economic growth and green finance can significantly promote GRE. • The impacts of green economic growth and green finance on GRE are heterogeneous. • Green technological innovation is an effective mediator in the 3G nexus. [ABSTRACT FROM AUTHOR]

Strengthening environmental regulation (Reg) is an important measure to solve energy and environmental problems, then to realize the profit sustainable growth (Gro). Taking 116 listed renewable energy enterprises in China from 2010 to 2019 as samples, this paper uses FE and SYS-GMM models to examine the moderating effect of three types of Reg in the relationship of factor market distortions (Dist) and the Gro. The conclusions are as follows: For the direct impact, capital and labor market distortions (DistK and DistL) hinder the Gro. Specifically, the absolute value of the coefficient of DistK in state-owned enterprises (SOEs) is greater than that of the DistL, which indicates that the inhibitory effect of DistK in SOEs is more significant. For the indirect impact, the coefficients of economic and supervised environmental regulation (RegE and RegS) are positive and significant, and promote the Gro of SOEs and non-SOEs, while legal environmental regulation (RegL) is the opposite, which shows that Reg has significant "cost effect" and "rebound effect". Moreover, Reg has a positive moderating effect, which is mainly reflected in SOEs, and alleviates the inhibitory effect of DistK and DistL on Gro to a certain extent. Finally, this paper puts forward some targeted policy suggestions. [ABSTRACT FROM AUTHOR]

The integrated phase change materials (PCM) solar wall can store solar energy effectively, which has a broad application prospect. However, the integrated PCM solar wall cannot completely release heat at night. In this paper, the evaporator of the heat pump system is embedded in the integrated PCM solar wall, which can realize the combination of active and passive utilization of solar energy. A numerical study on the thermal storage/release characteristics of the integrated PCM solar wall with an embedded evaporator was carried out in this paper considering its two-dimensional heat transfer. The effect of the thermal release mode, the thermophysical parameters of PCM and the solar radiation intensity on the thermal storage/release characteristics was studied. The simulation results showed that the active thermal release mode increased the released heat by 33.33 kJ/kg, and the proportion of the released heat to the stored heat increases by 30.12%, compared with the passive thermal release mode. Moreover, the increase of the phase transition temperature and the thermal conductivity of PCM can increase the stored heat and released heat, and the latent heat of PCM will increase the stored heat and decrease the released heat. The conclusion can provide a theoretical basis for the research of active and passive solar systems. [ABSTRACT FROM AUTHOR]

Without any assistance, the energy matching between air conditioner load demand and PV generation of PV direct driven Air Conditioners (PVACs) is inflexible. Phase Change Materials (PCMs) and building load flexibility can improve the real-time Zero Energy Probability (ZEP). In this paper, a coupling system consisting of PVACs, PCMs, and load flexibility was proposed for an office building. Sensitive analysis were conducted for different PCMs coupled with PVACs and load flexibility to improve the real-time ZEP with considering the PV capacity Factors (PVF), PCM type, and PCM thickness. According to the influence on the ZEP, the key parameters of the coupling system were ranked as follows: PVF > PCM melting temperature > PCM thickness. PCMs can reduce the PVF by 26.67% and assist the system achieving a 90% real-time ZEP in summer. The recommended PVF for the Hot-summer and Warm-winter and the Hot-summer and Cold-winter zone are 1.3 and 1.0, respectively, while the optimized PCM melting temperature are 27 °C and 26 °C, respectively. In summary, a complete evaluation method, a universal design route and different optimization schemes for PVACs coupled with PCMs and load flexibility were proposed in this paper, and it is conducive to the improvement of the real-time ZEP. [ABSTRACT FROM AUTHOR]

The pumped hydro energy storage station flexibility is perceived as a promising way for integrating more intermittent wind and solar energy into the power grid. However, this flexible operation mode challenges the stable and highly-efficient operation of the pump-turbine units. Therefore, this paper focuses on stability and efficiency performance of pumped hydro energy storage system (PHESS) under the various flexibility scenarios. First, a nonlinear model of PHESS coupling the hydraulic loss, mechanical loss and electrical loss of pump-turbine is established to study its stability and efficiency characteristics. Second, six flexibility scenarios including four transient processes and two steady processes are extracted based on the historical power output of a pump-turbine unit. Parameter responses indicate that the stability performance of PHESS got worse when the range of load-variation increased. Parameters response in the first 10s is steeper than that in the later 30s. Rotation speed and water head in part-load fluctuates periodically in a range of from −0.0024 to 0.01. In other words, 10 times more compared to the range response under the rated-load. Efficiency analysis suggests that the friction loss in scroll case is the dominated loss type in the transient processes, except for the FL condition. The responses of friction loss in straight pipe, impact loss in scroll case and volume loss are characterized by the corresponding discharge laws. The response curve of winding loss is similar with the response feature of rotation speed. This paper provides the stability and efficiency perspective when the operator exploits the flexibility potential of pumped hydro energy storage station. [ABSTRACT FROM AUTHOR]

As the penetration of renewable energy sources continues to increase, the stability of the grid is being challenged. Solutions are needed to curb fluctuations in renewable energy generation and ensure a stable electricity supply. As a clean and efficient secondary energy source, hydrogen energy plays an important role in the power system. However, the development of hydrogen energy storage systems is currently limited by technology and costs, making it difficult to scale up. How to invest to make hydrogen storage economical is worth studying. This paper constructs a regional microgrid system, considering the economics of investment by renewable energy generators (REGs) and integrated energy operators (IEOs), and the sensitivity of the payback period under conditions of market adjustment and technological progress. A combination of the Gurobi and Particle Swarm Optimization (PSO) algorithm is used to solve the investment optimization model, and Shapley is used to allocate multi-intelligence benefits. The results show that: (1) the investment returns and payback periods of REG are within a reasonable range; (2) IEO is hardly economical in the presence of market price changes and technological advances. On this basis, this paper constructs a win-win investment model for REG and IEO and explores the distribution of benefits under their cooperation model. The results show an increase in return on investment of 0.34% for REG and 1% for IEO following investments by REG in partnership with IEO. [ABSTRACT FROM AUTHOR]

Carnot batteries enable novel perspectives for decarbonizing the energy sector as an emerging technology for electrical energy storage. A power-to-heat process stores excess electrical energy as thermal energy which is transferred back to electrical energy on demand by a power cycle. This paper focuses on Carnot batteries by means of heat pumps and organic Rankine cycles (HP-ORC systems) as these systems combine the advantages of technically mature components, effective integration of heat sources and low-cost scalable storage. In combination with low-enthalpy geothermal heat, Carnot batteries offer an efficient synthesis of electrical energy storage and upgrading of low-enthalpy geothermal energy. Previous works highlighted that two-phase expansion can enhance the efficiency of heat recovery cycles. The present paper discusses partial evaporation and flash evaporation in Carnot batteries based on organic Rankine cycles and organic flash cycles (OFC) with volumetric machines as they enable two-phase expansion processes. The three investigated cycles ORC, OFC and OFC with two-phase expander are systematically analyzed in three steps. First, the potential cycle performances are identified without restrictions of volumetric machines. Afterwards, the effects of under- and over-expansion due to fixed built-in volume ratios are taken into account. Finally, a validated screw expander model is utilized to determine the performance of the three cycles in off-design conditions. The results show that the vapor quality of the partially evaporated ORC as well as the flash pressure ratio of the OFC both indicate a specific optimum depending on the storage temperature. The fixed built-in volume ratio of volumetric machines limits the efficiency of partial evaporation in the ORC due to strong under-expansion. Notably, the built-in volume ratio does not affect the optimal flash pressure ratio in the OFC. Partial evaporation increases the power output at the cost of efficiency which can be utilized during temporary peak loads. The ORC yields higher efficiencies than the basic OFC in all operating conditions due to the throttling losses of the OFC. Contrarily, the OFC with two-phase expander increasingly outperforms the ORC with rising storage temperature spread. This advantage increases in part load conditions as the OFC becomes less sensitive to the flash pressure ratio. Hence, this facilitates the control of flash pressure ratio and enables advantageous efficiencies. Thus, partial evaporation and flash evaporation can enhance the performance of Carnot batteries throughout a wide operational range. • Simulative study of partial evaporation and flash evaporation in Carnot batteries. • Introduction of the optimization problem "Carnot battery trilemma". • Evaluation of optimal built-in volume ratio for partial and flash evaporation. • Application of a validated twin-screw expander model for off-design simulation. • Performance maps provided as a basis for effective control strategies. [ABSTRACT FROM AUTHOR]

Vertical axis wind turbines of troposkein architecture are among the most attractive technologies for harvesting wind energy off-shore. In this paper, a high-fidelity Computational Fluid-Dynamics model of the flow around troposkein rotors is presented, experimentally validated, and applied to analyze the complex aerodynamics of this machine considering both operation and design aspects. At first, a set of two-dimensional simulations of the machine equatorial section was carried out to compare multiple spatial resolutions and three eddy-viscosity turbulence models, including Spalart–Allmaras, k- ω SST, and k- ω SST in low-Reynolds formulation, using as reference wind-tunnel experimental data. Then, the results of fully three-dimensional simulations for peak power and high TSR conditions are discussed, to further assess the models against experiments and to investigate the turbine aerodynamics and its spanwise variability, the flow around and downstream of the rotor, with particular emphasis on the peculiar character of troposkein rotor wake and the related tip vortices. Finally, the paper proposes an analysis about the impact of blade design on the machine aerodynamics, showing that rotors obtained with the simplest and most economic blade bending procedure outperforms configurations obtained by manufacturing the blades with plane airfoil sections along the troposkein curve. • Modeling issues for high-fidelity CFD of troposkein vertical axis wind turbines. • 3D-URANS analysis of a troposkein VAWT operating at peak power condition and a high TSR. • Assessment of performance and near-wake predictions against wind-tunnel experiments. • Investigation on the impact of different stacking lines for troposkein blade design. [ABSTRACT FROM AUTHOR]

Evaluation of the maximum connected solar photovoltaic (PV) capacity without violating stipulated network voltage limits is essential in managing the voltage rise in low-voltage (LV) networks under increasing solar penetration levels. In this regard, this paper reviews recent investigations completed in relation to solar PV hosting capacity (HC) assessment work in LV networks. A feeder based approach developed for evaluating solar PV HC constrained by over-voltage conditions in LV networks is summarised. Further, a novel nomographic tool developed for HC calculation based on the influential factors on HC as identified by solar PV location, feeder length/loading levels, conductor type and stipulated voltage limits, is reviewed. In addition, a three-stage solar PV connection criteria which was developed based on the rigorous outcomes of nomogram and the feeder based evaluation approach is presented in the paper. The HC assessment and solar PV connection criteria presented in this paper would be a contribution to further improvement of the available utility guidelines/standards on solar PV installations in LV networks. • Concept of feeder level solar PV HC — influential factors and limits. • Deterministic approach for evaluation of solar PV HC subjected to over-voltage curtailment in LV networks. • Nomographic tool for feeder based solar PV HC assessment in LV networks. • Three stage solar PV connection criteria for LV distribution networks. [ABSTRACT FROM AUTHOR]

Renewable energy is regarded as an effective method to alleviate environmental pollution and accelerate the green transition in China. This paper systematically investigates the impact of financial inclusion on renewable energy demand by using S-GMM model based on provincial data in the green finance era. This paper also analyzes the asymmetry, heterogeneity, and mediating mechanism in the nexus between financial inclusion and renewable energy demand, and highlights the following findings: (1) Improved financial inclusion can promote renewable energy development in China and present the characteristics of green finance; (2) the impact of financial inclusion on renewable energy demand is asymmetric and heterogeneous; specifically, this impact is much higher in northern China and the regions with higher renewable energy development; and (3) wind and photovoltaic power generation are effective mediators between financial inclusion and renewable energy industry, while the mediation effects of hydropower and nuclear power are not significant. New evidence in this study is presented for the achievement of green transition in China, as well as practical policy implications for improving financial inclusion and increasing renewable energy consumption. For instance, fiscal and tax incentives and green investment subsidies in the renewable energy sector need to be further improved. • This study explores the impact of financial inclusion (FI) on renewable energy demand (RED) in China. • Asymmetry, heterogeneity, and the mediating mechanism are further discussed. • Increased FI can promote RED , which presents the characteristics of green finance. • The impact of FI on RED is asymmetric and heterogeneous. • Wind and photovoltaic power are effective mediators between FI and RED. [ABSTRACT FROM AUTHOR]

Raytracing-based methods are widely used for quantifying irradiation on building surfaces. Urban 3D surface models are necessary input for raytracing simulations, which can be generated from open-source point cloud data with the help of surface reconstruction algorithms. In research and engineering practice, various algorithms are being used for this purpose; each leading to different mesh topologies and corresponding performance. This paper compares the impacts of four different reconstruction algorithms by investigating their performance using DAYSIM raytracing simulations. The analysis is carried out for five configurations with various urban morphologies. Results show that the reconstructed models consistently underestimate the shading influence due to geometrical shrinkages that emerge from the various model generation procedures. The explicit algorithms, with Generic Delaunay a notable example, have better performance with less embedded error than the implicit algorithms in both daily and annual simulations. Results also show that diffuse irradiance is responsible for larger contributions to the overall error than direct components. This effect becomes more prominent when modeling reflected irradiation in urban environments. Additionally, the work shows that solar elevation and shading geometry types also affect the error magnitude. The paper concludes by providing reconstruction algorithm selection criteria for photovoltaic practitioners and urban energy planners. [ABSTRACT FROM AUTHOR]

The USA is confronted with three epic-size problems: (1) the need for production of energy on a scale that meets the current and future needs of the nation, (2) the need to confront the climate crisis head-on by only producing renewable, green energy, that is 100% emission-free, and (3) the need to forever forestall the eruption of the Yellowstone Supervolcano. This paper offers both a provable practical, novel solution, and a thought experiment, to simultaneously solve all of the above stated problems. Through a new copper-based engineering approach on an unprecedented scale, this paper proposes a safe means to draw up the mighty energy reserve of the Yellowstone Supervolcano from within the Earth, to superheat steam for spinning turbines at sufficient speed and on a sufficient scale, in order to power the entire USA. The proposed, single, multi-redundant facility utilizes the star topology in a grid array pattern to accomplish this. Over time, bleed-off of sufficient energy could potentially forestall this Supervolcano from ever erupting again. With obvious importance to our planet and the research community alike, COMSOL simulation demonstrates and proves the solution proposed herein, to bring vast amounts of green, emission-free energy to the planet's surface for utilization. Well over 11 Quadrillion Watt hours of electrical energy generated over the course of one full year, to meet the current and future needs of the USA is shown to be practical. Going beyond other current and past research efforts, this methodology offers tremendous benefits, potentially on a planetary scale. • New and revolutionary engineering approach to clean energy production is proposed. • Scalable energy is produced using copper cylinders and computer science techniques. • Energy production from the Yellowstone Supervolcano prevents its future eruption. [ABSTRACT FROM AUTHOR]

Linear transverse flux permanent magnet machines (LTFPMs) are categorized as high force density topologies, which are suitable candidates for direct drive and low-speed applications. This paper introduces a novel LTFPM topology, which also proposes advantages of the flux-switching machines. This proposed linear transverse flux switching PM machine (LTFSPM) has two long passive translators located at the armature's top and bottom sides. The topology offers a high value of force density, and also, it is a cost-effective topology due to its double-sided passive translator. Furthermore, the PMs are fully utilized in the magnetic circuit, the end winding length is negligible, and the iron cores can be laminated easily. In this paper, the operation principle of the topology is explained and its magnetic circuit is discussed. To reduce the computational time of optimization procedure, a double-layer method is adopted, which provides high robustness, low computational time, and high precision. Results of the finite element method indicate that the proposed machine can be considered a potential candidate for linear motion applications especially direct drive wave energy conversion systems, which require high force density values. [ABSTRACT FROM AUTHOR]

Concentrated Solar Power plants (CSP) have the energy storage capability to generate electricity when sunlight is scarce. However, due to the highly non-linear dynamics of these systems, a simple linear controller will not be able to overcome the variable dynamics and multiple disturbance sources affecting it. In this paper, a deep Model Predictive Control (MPC) based on the Koopman operator is proposed and applied to control the Heat Transfer Fluid (HTF) temperature of a distributed-parameter model of the ACUREX solar collector field located at Almería, Spain. The Koopman operator is an infinite-dimensional linear operator that fully captures a system's non-linear dynamics through the linear evolution of functions of the state-space. However, one of the major problems is identifying a Koopman linear model for a non-linear system. Koopman eigenfunctions are involved in converting a non-linear model to a Koopman-based linear model. In this paper, a deep Long Short-Term Memory (LSTM) autoencoder is designed to calculate Koopman eigenfunctions of the solar collector field. The Koopman linear model is then used to design a linear MPC with terminal components to ensure closed-loop stability guarantees. Simulation results are utilized to show the satisfactory tracking performance of the proposed approach. [ABSTRACT FROM AUTHOR]

CO 2 pipeline can be applied to Enhanced Oil Recovery (EOR) projects and CO 2 geological storage projects, and has high engineering application value. However, pipeline transportation of CO 2 is a high-risk link in CO 2 storage projects. The phase state commonly used to transport CO 2 is a supercritical state with both gaseous and liquid characteristics, and there are also great challenges in the field of pipeline transportation. The existing researches have carried out a lot of exploration and application development in the heat transfer, phase change, transient and special conditions of supercritical CO 2 pipeline operation. In this paper, the modeling and exploration of the commissioning process before the formal operation of the supercritical CO 2 pipeline are carried out, and the boost path of the supercritical CO 2 pipeline in the phase diagram under different working conditions is obtained. The model developed in this paper is based on the sensitivity analysis of the effects of variables such as ground temperature, filling pressure speed, and whether to perform pressure-stabilizing leak detection operations. The step-up path in the phase diagram of the CO 2 pipeline commissioning process and the adjustment control method are obtained. And the critical temperature of each working condition that cannot avoid phase transition, thus contributing to the existing knowledge system in this field. [ABSTRACT FROM AUTHOR]

In this paper, the role of a Battery Energy Storage System (BESS) in the United Kingdom (UK) electricity market is investigated. Such device is selected since research works related to the topic demonstrate that BESSs help facing challenges caused by renewable energy sources increasing penetration in the power systems' field. Indeed, in the next future, BESSs will assume a relevant role thanks to their fast response time. In the present paper, an optimization model is implemented to encode the UK market rules and output the optimal set of offers on day-ahead and intraday markets, dynamic frequency response services and imbalance settlement. The market rules are formalised in a mathematical model considering market temporal sequencing and BESS technical limitations. The tool also models the state of energy management, necessary since BESSs are energy limited assets. Objective function and constraints are linearized to define a Mixed Integer Linear Programming problem to reduce the computational burden and to integrate the model in the Energy Management System previously developed at University of Genoa. Specific tests are performed including and excluding ancillary services to evaluate the related advantages. The obtained outcomes reveal that ancillary services are the most convenient options within all the implemented scenarios. [ABSTRACT FROM AUTHOR]

Concept-bottleneck models (CBMs) are a new paradigm to construct interpretable classifiers. The CBM architecture can be regarded as a neural network with a single hidden layer whose neurons are replaced by binary classifiers. Each of these binary classifiers implements a concept, that is, it attempts to answer a meaningful yes/no question: the presence or absence of a concept in the observation presented to the network. The output layer is usually implemented as a linear stage that combines the concepts into final decisions. This paper presents an application of the CBM paradigm to a problem of Extreme Wind Speed prediction, such that the forecasting properties of the system can be interpreted in terms of different concepts considered for this problem. A significant contribution of this paper is the proposal of an automated concept generation method, with controlled sparsity, in which the concepts are automatically extracted from the branches of decision trees fitted with informative features that capture the dynamics of the wind speed time series. The final forecasting system is able to predict extreme wind speed values in wind farms with good accuracy and interpretable results, as experiments over real wind speed data from a wind farm in Spain show. • Application of Concept Bottleneck Models for Extreme Wind Speed prediction. • Features capturing the dynamics of the wind speed borrowed from finance analysis. • Concepts are automatically extracted from the branches of decision trees. • Results in real data from a Spanish wind farm are discussed. [ABSTRACT FROM AUTHOR]

The global energy sector is currently undergoing a fundamental transformation as it shifts away from fossil fuels towards renewable energy sources. Green hydrogen is one of the most promising energy carriers of the future in the worldwide effort to reduce the carbon footprint of energy systems. The advancement and uptake of green hydrogen technologies depend on various technological, environmental, and economic factors. In this paper, a comprehensive review of recent studies in green hydrogen energy systems (GHES) is conducted, highlighting technoeconomic aspects from the component to the technology and broader system level. Firstly, the technological principles and recent progress of different green hydrogen generation, storage, and utilization technologies are summarized. Subsequently, an in-depth analysis of various technoeconomic modeling and experimental activities focused on integrated GHES is undertaken. By examining applications in the stationary and transport sectors, this review paper offers an assessment of the current state-of-the-art in terms of development and integration options. The technical challenges, key factors, and future research directions of green hydrogen technologies and systems are outlined, demonstrating that an effective, intelligent, and innovative integration of GHES with other technologies will encourage a more efficient use of resources and enhanced energy system flexibility, resilience, and energy security. • Characteristics, components and configurations of green hydrogen systems are presented. • Technoeconomic studies are collected in tabulated form and exhaustively analyzed. • State-of-the-art applications in stationary and transport sectors are discussed. • A critical review is provided to assess green hydrogen economic viability potential. • Challenges and prospects are evaluated, and future research directions are suggested. [ABSTRACT FROM AUTHOR]

Renewable energy communities with members which own electric vehicles (EVs) can benefit financially from the flexibility that EVs provide to distributed energy resources, such as photovoltaic generators. However, in residential environments, this benefit is often lost because during working hours, most EVs are not plugged in at the premises of the community. In this paper, we hypothesize that such communities can regain some of this lost benefit by offering membership to outside EV owners which are interested in charging their vehicles using the community's charging stations during these periods. This paper introduces an optimization model for energy communities consisting of prosumers, electric vehicles, and EV chargers. The model aims to evaluate the potential advantages of integrating external EV owners into an energy community. A hypothetical community representing a multi-apartment building is analyzed, considering scenarios both with and without external members. The analysis focuses on assessing the technical and economic benefits. The findings indicate that the economic benefits for the examined community are relatively small. However, a notable increase in these benefits is observed when the community is incentivized to share energy among members in the form of a flat network charge reduction for shared energy. [ABSTRACT FROM AUTHOR]

Hydropower has played an important role in Europe in recent decades, offering a unique combination of safe, low-cost, and clean power generation. Today, it is still one of the largest renewable energy sources (RES), accounting for about 35 % of RES electricity generation. However, grid stability is threatened by the increasing amount of undispatchable RES. Flexibility and dynamics such as energy storage and rapid response are urgently needed to achieve EU policy goals. In such a context, hydropower can play a key role, not only as a provider of regulated renewable energy but also due to its ability to balance a renewable energy system in the short term and the medium/long term by pumped storage technology. All these aspects underline the new role of hydropower, which aims to strengthen grid stability and power supply resilience and to enable higher penetration of volatile RES. In this context, the aim of this paper is to demonstrate the role of hydropower at the European level as well as the needs and opportunities of modernization to fully exploit its potential. In particular, this study provides, the assessment of the today flexibility offered by hydropower to the power system at the European level by leveraging a database of information collected through the participants to the working groups of the COST Action Pen@Hydropower which includes stakeholders in the hydropower sector of 34 European countries. The study confirms the key role of hydropower in future energy scenarios with 30 % of the flexibility demand at all time scales met by hydropower. Furthermore, the paper presents a review of the digitalization solutions and innovative technologies that support the growth of a new generation of sustainable hydropower together with the modernization opportunities for existing hydropower plants. The results of this work have practical implications for stakeholders in the hydropower sector and policymakers as it provides evidence at the European scale of the role of hydropower technology in balancing the power system and the need to have supportive frameworks and adequate markets to fully exploit the European hydropower potential to achieve the energy transition goals. [ABSTRACT FROM AUTHOR]

This paper presents a dual condensers heat pipe PV/T system with multiple operating modes, including hot water, space heating, and dual-function. To exploiting the system's potential of energy supply, this paper proposes a dynamic model of the system in dual-function mode on the basis of the verified dynamic heat transfer model and condenser distributed parameter model. Several effect factors on the system performance have been analyzed, including water tank capacity, air-cooled condenser area and the dual condensers installation height difference. The simulated results show that the above parameters have little effect on the system's total thermal efficiency but a significant effect on single condenser heat gain distribution. When the water tank capacity increases from 100 L to 200 L, the thermal efficiency of the water-cooled condenser increases from 10.68 % to 17.82 %, while the air-cooled condenser's decreases from 48.12 % to 40.72 %. As the air-cooled condenser area is changed from model 1 to 4, the total efficiency increase from 58.13 % to 71.41 %. The system's thermal efficiency falls from 58.66 % to 47.50 % and its overall efficiency falls from 71.41 % to 60.40 % when the height difference rises from 0 m to 0.7 m. [ABSTRACT FROM AUTHOR]