Field Of Renewable Energy Research Articles

Role of Oleaginous Microorganisms in the Field of Renewable Energy

The world increasingly requires biodegradable and renewable products in all production fields, with the vast volume of emissions generated by the fuel sector presenting a difficult issue that needs to be addressed [...]

Hybrid optimization and modelling of CI engine performance and emission characteristics of novel hybrid biodiesel blends

Different meta-heuristic optimization algorithms have been used in a variety of fields due to their intelligent behavior and fast convergence. However, use of these algorithms in the engine behavior optimization is very-limited. The development of so-called hybrid optimization technique when these algorithms are combined with experimental design technique is an upcoming method in the field of renewable energy. Hence in this research, meta-heuristic optimization algorithms and experimental design methods were combined to optimize the engine behavior. Additionally, artificial neural networks (ANN) were employed to forecast the performance and emission behaviors of a CI engine running on a novel hybrid biodiesel blend of Cucurbita pepo. L (pumpkin) and Prosopis juliflora, mixed with a novel Elaeocarpus ganitrus (Rudraksha) additive. To assess the success of the ANN, four statistical benchmarks (R2, and MSE) were used. Experiments were designed according to Design of Experiments (DOE) rules with performance and emission parameters as outputs. Response surface methodology (RSM) was employed to find the effect of interaction factors. Single objective and multi-objective optimization using highly efficient hybrid RSM-particle swarm optimization (RPSO) and dragon fly algorithm (RMODA) were employed to optimize the response of the obtained RSM equations. The outcomes demonstrated that RSM and ANN were excellent modelling techniques for these kinds of situations, with good accuracy. In addition, ANN's prediction performance (R2 = 0.978 for BTE) was somewhat better than RSM's (R2 = 0.960 for BTE). On the other hand, the PJB20 blend with 5 mL additive increased BTE by 52.8% and reduced BSFC by 34.9% at maximum load. The smoke opacity was lowered by 7.1% when compared to pure diesel, without any engine modifications. CO2 emission was seen to be shortened by 19.14%. Finally, it can be concluded that this novel biodiesel can be possibly utilized in CI engines with no modification and the engine characteristics can be controlled by optimization and prediction models.

Enhanced catalytic activities of Fe anchored on graphene substrates for water splitting and hydrogen evolution

Water splitting on single Fe atom catalyst anchored on defective graphene surfaces by using first-principles density functional theory. The structure and electronic features of isolated Fe atom anchored on three graphene surfaces with single vacancy (SV), double vacancy (DV) and Stone-Wales structure (SW) defect were systematically explored. The three structures prove to be high activity and high stability on catalytic. The adsorption and the energy barrier of water splitting as well as hydrogen adsorption free energy ΔGH∗ on single-atom Fe were also studied. The sequence of promoted splitting activity is found to be Fe@SW > Fe@DV > Fe@SV. Furthermore, by hydrogen adsorption free energy ΔGH∗ analysis, we predict that the HER catalytic activity of graphene nanosheet can be improved by anchoring Fe atom on SV and DV structures, which are comparable to or even better than noble metals. It is found that the catalytic activity of water splitting and HER can be changed with the shift in d-band center with respect to Fermi-level. Detailed investigations on electronic structure of Fe@graphene catalytic systems disclose an obvious orbital hybridization coupling and charge transfer between atom Fe on carbon surfaces and water molecule. These results provide us with new insight into design of high performer and low-cost catalysts and may inspire potential applications in the fields of clean and renewable energy.

Incentivizing Start-Ups and Start-Up Ecosystems in European Project Funds – the Case of Grant “Performance and Excellence in the Field of Environment and Renewable Energy through Modern Cluster Entities”

Capital providers, such as shareholders on capital markets or European funding providers, are interested in the net present value of discounted cash flow and the risks or opportunities that may contribute to financial planning in a negative or positive way. In an uncertain environment however, the lean start-up movement means venture capital is used to finance business models. The lean start-up complements the business plan via discovery driven planning. These are holistic approaches to uncertainty management in all business aspects, with a designated methodology. This methodology will be the scholarly literature review in this article, whose goal is to elaborate the reference lean start-up methodologies and their relevance in empirical data analysis, European project funding calls. European projects demand uncertainty management. The article purposes to make European funds easy to understand as their requirements are explained and the most suitable scientific solution is sought. The methodology is a descriptive case study, with instrumental value. Findings are that funding authorities, be they capital markets or public funds, benefit highly in their decisions by lean start-up techniques. The research concerns the suitability of start-up ecosystems with European funds, and the conclusion is a high interest from the latter to the former.

저압직류차단기의 소전류 영역 차단특성과 성능향상을 위한 연구

A low voltage direct current(DC) circuit breaker is an electrical protection device that interrupts the abnormal fault currents which result from the over-loads or short-circuits in a low voltage(less than 1,500Vdc) power distribution line. Recently, as interests in renewable energy fields(such as photovoltaic and energy storage systems) have increased, research on DC circuit breakers for system protection is also being actively conducted. However, breaking the fault current in DC system is considerably difficult even small current region since the DC does not have current zero point such as in AC. When a short circuit occurs, a fault current flows between contacts of a DC circuit breaker even though they are separated by the protective control system. Arc voltage between contacts of the circuit breaker should generate as high as possible during breaking phase. High arc voltage could lead the fault current of the circuit to zero so that arc plasma is eliminated. Based on this behavior, arc extinction system of a DC circuit breaker should be designed to effectively increase the arc voltage during current interruption period. In this paper, the characteristics of DC breaking specially in small current region were confirmed through several types of current breaking experiments and result analysis, and a method to improve performance of DC breaking in small current region was presented, and experiments were carried out to verify the validity of the method.

ASSESSMENT OF SURPLUS CROP RESIDUE BIOMASS ENERGY SECTOR: INDIA

This paper deals with three issues related to surplus residues biomass energy: 1. the concept of surplus crop residues biomass energy, 2. institutional setup for residues biomass energy policy and planning, and 3. Its achievement at the national level. The choice of surplus crop residues biomass energy is dependent on the institutional framework that shaped its existence in the renewable energy sector. The current study is shaped by various alternative learning-based approaches used by academics and practitioners in the field of renewable energy. The approaches show similarities with Clean Development Management (CDM) goals and reflect the alternative and sustainable development context within which they were framed toward ecological-based energy capacity building. The institutional framework can encourage surplus crop residual biomass energy, and it is one of the few alternative energy resources in which individuals appear eager to invest. However, the surplus crop residues biomass energy initiative is slowly spreading across the country, wait and watch if the surplus crop residues biomass energy approach can prove its merits.

Antecedents of Creating Business Models in the Field of Renewable Energy Based on the Concept of the New Age of Innovation

The purpose of this paper is to identify the antecedence of business models for the renewable energy sector, characterise their concepts and structure, and assess the importance of innovation in the creation of value for the customer and for the business in the examined business models. According to the concept of K. Prahalad and M. S. Krishnan, an operational business model consists of three basic components. The first two are social architecture and technical architecture that represent specific resources. The third component comprises business processes. The operating business model according to the principles of the New Era of Innovation was used. The business models were presented as case studies of the following: a photovoltaic farm, a passive building and a local (communal) biogas plant. A desk research method was employed as well as triangulation of the research methods of non-participant observation, unstructured interview and business documentation review, in order to develop the case studies. The identification of antecedents for business models in renewable energy generation allows the argument that the business model can be treated as a system for the configuration of resources and interdependent activities, emphasising the role of the configuration of tangible and intangible elements. As the presented business models have been active for a relatively limited time, changes in competence and human capital attitudes, as well as social acceptance for those models, are not examined here. The absence of the upper and lower performance limit of the optimisation algorithm, or system variables, may be an interesting area for further research.

COMPREHENSIVE REVIEW OF SOLAR PV POWER FORECASTING USING INTELLIGENT COMPUTING

The field of renewable energy offers answers to emerging nations' problems with sustainable energy. The electricity constraint in India is being addressed by the adoption of various renewable energy options. The market is promising for domestic organisations, distribution networks, and transmission networks, but the financial position is slow and considerable despite the recent significant growth in power generation. India has an installed capacity for wind power of 230,000 kilowatts and 450,000 kilowatts of hydroelectric power, however it has little to no potential for renewable energy. Although India presently occupies a strong position in this area, the goal is to increase installed renewable energy capacity from 37 GW to 1.75 million kilowatts by 2022 (excluding major hydropower). A significant component of the government's extension strategy is solar energy. For geography and structure, the solar PV system demonstration is quite beneficial. We require efficient design and forecasting tools for an efficient structure. A common tool for planning and optimising the design and construction of standalone photovoltaic solar systems that are connected to the grid is the PV system. The goal of this research is to provide the comparable design model of a solar photovoltaic power plant and to analyse the influence of power forecasting on solar photovoltaic system performance evaluation. PV and IV features of solar photovoltaic systems have been used to create the mathematical model of solar photovoltaic systems and analyse performance. For the best forecasting in the given situation of complex operating conditions, a modified prediction technique was put into place.

A dielectric spectroscopy study of deep eutectic mixtures of glycerol and hydroxyl ammonium chloride in liquid and glassy states

This paper reports the molecular dynamic study of ionic deep eutectic (DE) mixtures prepared by mixing glycerol (Gly) with hydroxyl ammonium chloride (HACL). Here, the dielectric relaxation spectroscopy over wide ranges of frequency (10−1-107 Hz) and temperature (193–323 K), was employed to access the dynamic observables in liquid and glassy states. Fourier-transform infrared spectroscopy (FTIR) revealed that HACL and Gly are associated via the formation of hydrogen bonds between their functional groups. Differential scanning calorimetry (DSC) results indicated that a glass transition temperature slightly changes compared to that of pure Gly. It is worth mentioning that, at low frequencies, where α-relaxation process occurs, electrode polarization and dc conductivity affect the dielectric spectra of both neat and binary DE mixtures. The shape and intensity of the α-process are highly affected, while it is completely masked at higher concentrations due to the predominance of dc conductivity. Further, the dc conductivity of Gly abruptly increased by about 3 orders of magnitude upon adding only 1.5 wt.% HACL due to an increase in both mobility and concentrations of the introduced free ions. With further increase of HACL, it increases at a relatively low rate. Interestingly, the excellent electrical properties of the binary mixture of 1.5 wt.% HACL make it promising candidate in potential applications in the renewable energy field and energy storage devices.

Selection of Microalgae Harvesting Technology for Bio-crude Oil Production

Energy consumption of fossil fuel which keeps increasing has led to the urgency of research and development on the field of renewable energy for the future. Microalgae are considered to be the most promising new source of biomass compared with first and second-generation feedstocks. A great challenge is a choice of an effective approach for microalgae harvesting. Additional challenges of microalgae harvesting come from the small size of microalgae cells (3-30µm) and the similarity of the density of the microalgae cells to the growth medium. This research is aimed to determine the appropriate microalgae harvesting technology for bio-crude oil production. Several potential microalgae harvesting technologies are centrifugation, filtration, inorganic flocculation, organic flocculation, bioflocculation, electrocoagulation, and flocculation-sedimentation. The method used in this research is Analytic Hierarchy Process (AHP). The results indicate that the parameters taken into consideration are energy need (0.339), cost (0.214), risk of contamination (0.098), efficiency (0.133), technology availability (0.066), microalgae strain flexibility (0.079), and production time (0.071). In a case study, the pairwise comparison of seven alternatives each for the harvesting and seven criteria are compared. The best alternative that can be recommended as a microalgae harvesting technology is flocculation-sedimentation with a weight of 0.202.

Modelling Nucleation during Electrodeposition By MODEL Method. Parametric Identification Considering Agitation By Rde or Ultrasound

Nowadays, 40% of the world wide used energy is provided by electric power and this share should reach about 60% by 2040. For environmental reasons, it is crucial to ensure low dissipation loss in power electronic devices by optimizing energy conversion. In the field of renewable energies and automotive electronics, possible energy savings are estimated to be between 20 and 35%. For that purpose, innovative power components and modules are required, with a growing interest for fast and simple joining processes in their fabrication management, in the case for example of the assembly of large-size double-side cooled modules. Several options are possible, including free sintering of metallic pastes or electroforming welding. In all cases, this requires a great control of both surfaces to be joined, mostly prepared by electrodeposition (microstructure, porosity, alloy composition). But the final properties of electrodeposited coatings are strongly dependent of the first nucleation steps, which influence the whole layer structure. In this frame, the modelling of a nucleation process followed by diffusion limited three dimensional growth is an area of promising interest. The study of potentiostatic current transients is a relevant methodology, allowing the determination of several parameters such as nucleation rate, nucleus density, and number of active sites. Different competing models are available, such as Scharifker and Hills [1] and Scharifker and Mostany [2]. By using the model method i.e. the identification of the model parameters by error minimization, it is possible to reach an accurate description of the first layer growth in the case of different metals such as silver and copper. Nevertheless, little attention have been paid to changes in hydrodynamic conditions, for example in the study of current response under forced convection [3]. The present work describes the extension of the model method to the modelling of the first steps of nucleation growth in the case of a sample exposed to an ultrasonic irradiation, which was compared to forced convection induced by a rotating disc electrode at the very same agitation level (equivalent velocity [4,5]. Eventually, the case of electrodeposited alloys was examined, as a function of their Brenner classifications (anomalous and normal codeposition [6]). The limitation of the data processing by the numerical approach are also discussed.[1] Scharifker, B. & Hills, G. Theoretical and experimental studies of multiple nucleation. Electrochimica Acta 28, 879–889 (1983).[2] Scharifker, B. R. & Mostany, J. Three-dimensional nucleation with diffusion controlled growth. J. Electroanal. Chem. Interfacial Electrochem. 177, 13–23 (1984).[3] Hyde, M. E. & Compton, R. G. Theoretical and experimental aspects of electrodeposition under hydrodynamic conditions. J. Electroanal. Chem. 581, 224–230 (2005).[4] Pollet B.G., Hihn J.-Y., Doche M.L, Mandroyan A., Lorimer J.P., Mason T.J “Transport limited currents close to an ultrasonic horn: equivalent flow velocity determination”, Journal of Electrochemistry Society, 154(10), E131-E138, (2007)[5] A. Nevers, L. Hallez, F. Touyeras, J.-Y. Hihn, Effect of ultrasound on silver electrodeposition: Crystalline structure modification, Ultrason. Sonochem. 40 (2018)[6] Brenner, A. Electrodeposition of alloys. Principles and practice Volume II, (1963).

Investigation and Design of Soybean-Derived Carbon Anode Materials for Potassium-Ion Battery Applications

Lithium-ion battery (LIBs) system is one the most widely used energy storage systems in today’s renewable energy field. However, with the dramatically increased demand over the past decades and limited core material storage, concerns arise regarding its sustainability and large-scale applications. While trying to make more efficient LIBs, the studies of alternative battery systems also appear to be more and more critical. Among many newly studied battery systems, Potassium-ion batteries (PIBs) have caught our attention. With the advantage of high abundance of Potassium (K) and low redox potential of K/K+ (2.93 V vs. standard hydrogen electrode), it appears to be a perfect candidate for substituting many of the current LIBs applications. However, the absence of a suitable carbon anode has hindered the development of PIBs. Herein, we used low-cost and abundant soybean as base material and developed a high-performance hard carbon anode for PIBs. Hard carbon, produced with 500 degrees process, exhibited the highest discharge capacity of 225 mA h g-1, long lifetime of 900 cycles, and good rate capability. Benefited from low activation temperature, the soybean-derived carbon has a medium surface area, large interplanar spacing graphene layers and low degree of graphitization, which are favored by the adsorption-dominated K-ion storage mechanism. To further improve the anode efficiency, a thin layer of Al2O3 coating (~ 2 nm) was applied on the hard carbon by Atomic Layer Deposition (ALD) to function as artificial solid electrolyte interphase and increased the Coulombic efficiency from 99.0% to 99.6%. After investigating the relationship among electrochemical performance, material interface, structural design, and mechanism of potassium-ion storage, we provided new insights for the design and synthesis of carbonaceous materials with improved storage capacity and efficiency for future developments of PIBs.

MnO2-Modified 3D-Printed Lattice Photo-Bioelectrode for Photosynthetic Energy Conversion from Spinach Thylakoids

Photosynthetic bio-solar energy conversion has been widely investigated as a promising potential in the field of renewable energy due to its high internal quantum efficiency. Thylakoid membranes (TMs) are organelles in chloroplasts where photosynthesis occurs. Once photosynthesis begins photosynthetic electrons (PEs) were generated, and they were transferred via proteins embedded in TMs by sequential redox reactions. To efficiently collect PEs, several approaches were reported to improve electrical connections such as carbon nanotube modified electrode [1], graphene oxide (GO)/TMs composites [2], or ruthenium oxide (RuO2) modified electrode [3]. As another approach, TM-alginate films were electrosprayed on SU-8 micro-pillar electrode to enlarge the electrochemical surface area between TMs and electrode [4]. However, the previous works were still limited in using two-dimensional electrodes with a marginal increase of electrode surface area.In this study, we aimed to maximize the electrochemically-active surface of TM-decorated bioelectrodes using 3D-printed polymeric lattices. We designed an octet-truss lattice structure with a high specific surface area. For the large surface area of the electrode with a high volume fraction, a strut diameter of the lattice was set to be 0.4 mm in the unit cell of an octet-truss lattice with a total length of 2.5 mm. To maximize light transmission, the octet-truss lattice was 3D-printed with a clear resin using stereolithography (SLA). To grant electrical conductivity on the hydrophobic nature of poly(urethane dimethacrylate) resin, poly(dopamine) (PDA) was polymerized as a binder on SLA-printed lattices followed by immersion in the 1.3 wt% of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution for 30 min. After immersion in PEDOT:PSS solution, PEDOT:PSS coated lattice was gently dried to remove the remaining solution with N2 gun and annealed in a vacuum oven at 120 ℃ for 15 min. On the other hand, the intrinsic electrical conductivity of PEDOT:PSS is lower than 1 S/cm. Therefore, to enhance the conductivity of annealed PEDOT:PSS layer, PEDOT:PSS coated lattice was immersed 5 wt% of ethylene glycol (EG) solution. Then, EG-treated PEDOT:PSS coated lattice was annealed in a vacuum oven as above described. Due to the removal of surplus insulating PSS chains and reorientation of PEDOT chains, the resistance of EG-treated PEDOT:PSS coated lattice was measured thousands of times lower than no treated lattice. A manganese oxide (MnO2) was electrochemically deposited for improved attachment to TMs at 0.5 V vs Ag/AgCl for 2 min. Then, TMs of 1 mg chl/ml were drop-cast on MnO2/PEDOT:PSS/PDA octet-truss lattice electrode. Each intermediate product was carefully analyzed using SEM, optical microscopy, and fluorescence spectroscopy. The PE currents from TM/MnO2/PEDOT:PSS/PDA octet-truss lattice electrode were measured and compared to a flat electrode and with different layers of lattice structures. With 2 layers of TM/MnO2/PEDOT:PSS/PDA octet-truss lattice electrode, the PE currents were increased 4 times compared to PE currents of the flat electrode. Acknowledgement This work was supported by the National Research Foundation of Korea(NRF) Grant funded by the Korean Government(MSIT) (No. 2020R1A2C3013158), and the Human Resources Development program (No.20204030200110) of the Korea Institute of Energy Technology Evaluation and Planning(KETEP) grant funded by the Korea government Ministry of Trade, Industry and Energy.

A Review and Case Analysis on Biaxial Synchronous Loading Technology and Fast Moment-Matching Methods for Fatigue Tests of Wind Turbine Blades

Wind power utilization is attracting worldwide attention in the renewable energy field, and as wind power develops from land to sea, the size of the blades is becoming incredibly larger. The fatigue test, especially the biaxial synchronous fatigue test for the blades, is becoming an indispensable step to ensure the blade’s quality before mass production, which means the biaxial independent test presently used may have difficulty reproducing the real damage for large-sized blades that oscillate simultaneously in flap-wise and edgewise directions in service conditions. The main point of the fatigue test is to carry out accelerated and reinforced oscillations on blades in the experimental plan. The target moments of critical blade sections are reached or not during the test are treated as one significant evaluation criterion. For independent tests, it is not hard to realize moment matching using additional masses fixed on certain critical blade sections, which may be not easy to put into effect for biaxial synchronous tests, since the mechanical properties and target moments in the flap-wise and edgewise directions are widely varied. To realize the mechanical decoupling for loading force or additional mass inertia force in two directions is becoming one of the key issues for blade biaxial synchronous fatigue testing. For this problem, the present paper proposed one mechanical decoupling design concept after a related literature review. After that, the blade moment design and target matching approach are also proposed, using the Transfer Matrix Method (TMM) for moment quick calculation and Particle Swarm Optimization (PSO) for case optimization.

Preface: International Conference on Alternative Fuels and Electric Vehicles 2021 (ICAFEV 2021)

International Conference on Alternative Fuels and Electric Vehicles 2021 (ICAFEV 2021) was hosted by the Alard College of Engineering and Management, Pune, India in association with Technology Research and Innovation Centre, Pune, India and Accra Technical University, Accra, Ghana on 09-10 December 2021 and conducted in virtual mode. This international meeting provided a platform to various worldwide researchers, and academicians engaged in the field of alternative fuels, electric vehicles and renewable energy with the motive of exploring the research to drive the World towards a sustainable future. ICAFEV 2021 received papers from authors of eleven countries such as Cameroon, Chile, Ghana, India, Malaysia, Mexico, Thailand, Turkey, Ukraine, Australia and United Kingdom.This volume is a compilation of research papers presented in three tracks, 1) Alternative Fuels, 2) Electric Vehicles and 3) Renewable Energy. We feel, these papers will provide a valuable contribution in the field and readers will receive this content for their future research activities.The conference organizers and associate organizers are thankful to all authors, technical committee members, advisory committee members and organizing committee members for contributing actively and whole heartily in successful completion of the conference throughout the various stages. We also express out gratitude towards the IOP publishing for providing support to publish the ICAFEV 2021 papers in IOP Conference Series: Earth and Environmental Science.List of ICAFEV 2021 Committees are available in this pdf.

Strandberg-type polyoxometalate deriving O,P co-doped NiMoS/CC catalyst for highly efficient hydrogen evolution electrocatalysis

Hydrogen production from electrolytic water is an indispensable component in the field of renewable energy. The preparation of electrocatalysts with low price and high performance is essential for hydrogen evolution reaction (HER). Herein, Strandberg-type polyoxometalate was used as pre-assembled molecular platforms to construct and regulate NiMoS active sites at the atomic level. O,P doping was performed to boost the number of active sites using controllable sulfidation method. O,P–NiMoS nanoparticles supported on highly conductive carbon cloth exhibit significant activity for HER. The overpotential are only 39 and 30 mV at a current density of 10 mA cm−2 in both acidic and alkaline solutions, respectively. This excellent performance can be attributed to the finely tailored NiMoS active sites, increase of S-unsaturated species and the synergistic effect between carbon cloth and O,P–NiMoS. Therefore, this study provides a feasible strategy for rational design of efficient electrocatalysts for renewable energy applications.

Carbon Nanotube-Coupled Seaweed-like Cobalt Sulfide as a Dual-Functional Catalyst for Overall Water Splitting.

Preparation of high-efficiency dual-functional catalysts remains the bottleneck for electrochemical water splitting. To prepare a non-precious metal catalyst with high activity and stability, here, we present a seaweed-like structure consisting of transition-metal sulfide nanoplates self-assembled on carbon nanotube sponge networks (SW-CoS@CNT). By adjusting the key parameters during synthesis (e.g., the loading amount and ratio of Co and S precursors), the microstructure can be tailored in a wide range, and sulfur defects can be introduced into the nanoplates by thermal annealing. The resulting SW-CoS@CNT serves as a freestanding dual-functional catalytic electrode, showing low overpotentials of 105 and 218 mV for the hydrogen evolution reaction and the oxygen evolution reaction, respectively, which are superior to most reported transition-metal-sulfide-based catalysts in alkaline solution. Rational design of this hierarchical biomimetic structure may be useful in developing high-performance electrochemical catalysts in renewable energy and environmental fields.

Bibliometric Studies on Renewable Energy—Poland Compared to Other EU Countries

The necessity to use renewable energy sources (RES), especially in EU countries, is becoming more and more urgent in the face of environmental degradation. It is reflected not only in technological solutions for obtaining energy from renewable sources, but also in scientific research supporting RES technology development. There are an increasing number of papers on renewable energy. The aim of the study was to compare research areas concerning renewable energy in Poland and other EU countries by analyzing scientific works. A selected collection of publications available in the Scopus scientific databases was selected as the subject of the study. After cleaning the data and elaborating the thesaurus, the analysis of the article content was conducted applying text processing methods. Conceptual maps of keywords and keyword co-occurrences were created, which enables arranging and classifying knowledge from the subject area. Research hotspots and the directions of science development in the field of renewable energy were identified. The computer program VOSviewer was used in the investigation. Lorenz curves and Gini coefficients were used to identify quite a strong concentration of RES articles in leading journals on the publication market.

Does an environmental policy bring to green innovation in renewable energy?

This research examines the effect of environmental policy stringency on green innovation in renewable energy technology and whether the green innovation response differs with varying degrees of environmental policy. Based on panel data of 33 countries over the period 1990–2015, we show that a stringent environmental policy does encourage green innovation in renewable energy technology, and this impact is more pronounced in OECD countries and high-income countries. More specifically, a stringent non-market-based environmental policy induces more patents in renewable energy generation. The findings also show that a stringent environmental policy yields green innovation for geothermal energy, hydro energy, and marine energy, but not for wind energy and solar energy. Heterogeneity analysis suggests that innovation capacity and environmental pressure enhance the impact of environmental policy stringency on green innovation in the renewable energy field. Finally, the paper presents that clean energy investment plays the role of a mechanism through which environmental policy stringency spurs green innovation in the renewable energy field, offering insights into the influence of environmental policy stringency on green innovation.

ZIF-67-derived ultrathin Co-Ni layered double hydroxides wrapped on 3D g-C3N4 with enhanced visible-light photocatalytic performance for greenhouse gas CO2 reduction

CO2 photoreduction into high value-added chemicals shows great application prospects in the fields of environmental protection and renewable energy. However, the design and preparation of new heterogeneous photocatalysts with efficient CO2 photoreduction activity remains a challenge. Here, hierarchical cobalt-nickel layered double hydroxides (CNLDH) were confined on the surface of 3D g­C3N4 (NCN) to construct the CNLDH-NCN hybrids for photocatalytic reduction of CO2. The fabrication involves NaCl-template-assisted calcination, in-situ growth and in-situ etching. The CNLDH-NCN hybrids show a well-defined hierarchical and multi-hole structure, which promote the light-harvesting, charge separation and the adsorption of CO2. The optimal hybrids show high photocatalytic performance of CO2 to CO (27.67 μmol∙g-1∙h-1), which is 6.0-fold and 3.6-fold of NCN and CNLDH, respectively. The novel strategy successfully integrates hierarchical CNLDHs and NCN into a spatial conductive network frame with homogeneous and intimate interfacial contacts, boosting the photocatalytic performance. Meanwhile, it provides a new insight for the construction of a promising catalyst for solar energy conversion.