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• The thermal, rheological, and optical properties of ferrofluids and how they change with magnetic fields were discussed. • The utilization of ferrofluids in solar energy systems was detailed in a state-of-the-art analysis. • The recommendations aimed to optimize the use of ferrofluids and magnetic fields in energy systems to enhance performance. Solar energy technologies play a crucial role in the transition to sustainable energy sources; however, there is an ongoing challenge in optimizing their efficiency and performance. This review paper thoroughly exposes the potential for enhancing solar systems by incorporating ferrofluids and utilizing magnetic fields. It provides a comprehensive examination of the rheological, thermal, and optical properties of ferrofluids, as well as their behavior when exposed to magnetic fields. The paper emphasizes the ability of ferrofluids to improve heat transfer efficiency, adapt to changing conditions, and enable precise control in the conversion of solar energy. Furthermore, the review addresses the obstacles and limitations associated with integrating ferrofluids into solar technologies, proposing potential solutions and outlining future research directions. [ABSTRACT FROM AUTHOR]

[Display omitted] • PCM energy storage and PV/T coupled multi-source heat pump systems were combined. • The thermal performance, energy efficiency, and economy of the system were analyzed. • The performance of paraffin C17 and water as energy storage materials were compared. • The performance of six low-temperature PCMs applied to the system were analyzed. • Compared to the existing system, it saves 56 % of energy and 27.7 % of operating costs. To improve the application of renewable energy in the heating zone, as well as to address the limitations of air and water source heat pump. The study presents a PV/T (photovoltaic/thermal) coupled air–water source heat pump system integrated with phase change energy storage. A theoretical analytical model and TRNSYS simulation model of the system were developed to evaluate the thermal performance, energy efficiency and economics of the system. The performance of phase change energy storage was compared with that of water storage, and the effect of different phase change materials on the system characteristics. The results show that the coupled system achieves a seasonal performance factor of 2.3, a 56 % reduction in energy consumption, and a 27.7 % reduction in operating costs compared to a conventional gas boiler system. Comparative analysis with the water storage system showed that the system equipped with phase change materials performed well in terms of energy consumption, operating costs and heating stability. In addition, the density of the phase change material has a biased effect on the overall performance of the system. This paper can provide a reference value for the study of renewable energy heating systems in cold zone. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solar-hydrogen hybrid system integration proposed for oil & gas industry. • Techno-economic-environmental optimization using novel Fick's Law Algorithm. • System sizing using Fick's Law Algorithm show an optimization in efficiency and cost. • Study shows 45% solar, 35% fuel cell, 20% gas turbine power contribution. • Renewable energy integration in oil & gas cuts CO2 emissions, boosts sustainability. The global demand for sustainable energy solutions in the oil and gas industry has stimulated interest in the integration of renewable energy sources. This paper investigates the techno-economic and environmental aspects of incorporating a solar-hydrogen-based hybrid renewable energy system (SHRES) into oil and gas processing facilities. The proposed SHRES, comprising Solar PV modules, hydrogen production and storage systems, and a gas turbine generator (PV-FC-EL-Tank-GT), aims to enhance energy efficiency and reduce the carbon footprint of energy-intensive operations. The study utilises a multidisciplinary approach, encompassing engineering, economics, and environmental analysis. The techno-economic evaluation employs detailed modelling and optimisation using Fick's Law Algorithm, ensuring efficient energy production and cost-effectiveness. Ecological assessments quantify potential reductions in greenhouse gas emissions and other environmental impacts. The technical and economic evaluation identifies the electrolyser system as the most significant cost contributor (57%). The optimised system balances energy sources with 45% from PV modules, 35% from fuel cells, and 20% from gas turbines, showcasing substantial reliance on renewable energy while maintaining required power generation. Addressing the urgent need for sustainable energy solutions in the oil and gas industry, the study highlights the potential of SHRES integration. By employing Fick's Law Algorithm, alongside with 80 % of renewable energy integration, the research optimises system components to optimise the annualised cost to be $57,539.85, decrease to zero the Loss of Power Supply Probability (LPSP), and mitigate CO2 emissions to a lowest value of 0.147 gCO2eq/kWh (by 80 %). The electrolyser system's pivotal role and the distribution of power generation sources are emphasised. This study presents a novel approach to integrating solar-hydrogen systems into oil and gas processing facilities, aiming for sustainability. The findings underscore the significance of the electrolyser system and the distribution of power generation sources in optimising the SHRES. Recommendations for renewable energy integration and potential reductions in CO2 emissions and costs are discussed, providing valuable insights for future energy policies. [ABSTRACT FROM AUTHOR]

• Providing an inclusive, up-to-date, and organized review of the published research. • Taxonomy of microgrid based on control structures, specifications and components. • Energy management summation and classification based on several significant factors. • Discussing some of the skilled methodologies and techniques developed or adopted. • Taxonomy of the different modeling and handling methods of the uncertainty. Energy is one of the essential foundations for the sustainable development of human society, so its management is necessary. Energy management system (EMS) can be explained as the procedure of optimizing, planning, controlling, monitoring, and saving energy to maximize operations and efficiency and minimize consumption. Microgrid (MG) requires EMS as an efficient and optimal tool owing to the stochastic nature of electrical loads and renewable sources. Moreover, energy management system is responsible for operation of a MG in reliable, secure and economical manner in either states of grid-connected or disconnected. Many literatures have recently focused on the expansion of advanced strategies of the MG energy management for establishing a self-sustained MG in both industrial and academic research. Thus, a comparative research is needed for having a 360° viewpoint of the energy management domain in MGs. In this regard, this research investigates a comparative and critical analysis of the developed strategies of the energy management for the MGs from different views and aspects from 2009 to 2022. The review strategy systematically adopted by the author includes: (i) Extracting research papers relevant to energy management in MGs; (ii) Filtering the significant papers to prepare a database of related research papers (iii) Classifying the used methods for EMS based on the technique, control strategies, and structure; (iv) Discussing potential directions for future studies. In a wider outlook, this research provides a systematic and updated review of energy management strategies for MGs developed by different researchers. The author hopes that academicians and practitioners can use the suggested framework as well as the offers presented for further studies on this significant yet sophisticated issue. [ABSTRACT FROM AUTHOR]

• "Transition to sustainable multi-building energy systems can reduce greenhouse gas emissions by synergising the multiple renewable energy sources with specific structural characteristics and occupancy constraints of buildings." • "To ensuring energy flexibility and resilience, optimization strategies for multi-building energy systems vary significantly with the climatic context and potentials for integrating energy storage technologies, highlighting the necessity for adaptable designs considering future energy demands and the expansion of district-level systems." • "There is a pressing need for more user-friendly multi-building energy system simulation tools to facilitate effective long-term planning and to optimize the design and management of energy flows among multiple buildings, ensuring maximum efficiency and sustainability. The transition to clean and sustainable energy systems in the building sector is vital to reduce global greenhouse gas emissions. In this regard, shifting the focus from single buildings to clusters of buildings, such as at the district level, can provide more effective sustainable solutions. In this study, the term Multi Building Energy Systems (MBES) was introduced to represent various scales, from local communities to districts and larger urban areas. This approach reflects a more inclusive understanding of sustainability potentials for large-scale building blocks that goes beyond traditional boundaries. Such systems encompass the aggregated energy impacts of multiple buildings whether physically proximate or connected via smart grid technologies that enable two-way energy and information flows. This paper comprehensively reviewed case studies on MBES that have achieved zero-energy, nearly-zero-energy, and positive-energy performance. The literature review, facilitated by a combination of database searches and snowball search techniques, has yielded 67 relevant case studies. The findings revealed diverse pathways towards achieving optimal renewable energy production depending on the location and the climate. Integration of renewable energy sources and energy storage systems is pivotal in achieving economies of scale, reducing operational costs, and enhancing resilience and reliability of energy supply at the neighbourhood scale. Total energy use and emissions reduction could be achieved by considering the architectural features of the building stocks. The study highlighted the need for adaptive strategies in MBES implementation to address challenges such as power grid overloads and the complexities of spatial arrangement, to meet current demands, while ensuring long-term energy resilience and sustainability in evolving urban landscapes. The limited adoption of MBES simulation software suggests a need for accessible tailored software. Future research should focus on developing advanced personalised energy management and control strategies, while continuously assessing emerging technologies for improving MBES performance. [ABSTRACT FROM AUTHOR]

• A comparison method between energy-only and energy and reserve model. • Higher revenue for flexible technologies was achieved for joint model. • The down reserve proved to be more required in high RES systems. • The study showed significant difference in operation between two models. The requirements for ancillary services in energy systems are growing as the amount of renewable energy sources such as solar and wind increases. On the other hand, the system can benefit from extra sources of flexibility thanks to the increased digitalization that enables successful integration of demand response and energy storage. The majority of recent energy system analysis research did not consider the regulation markets. As a result, these investigations preclude the ability to fully evaluate the advantages of energy storage and flexible cooling loads. With the method outlined in this paper, it is possible to compare the two strategies and assess the advantages of energy storage and flexible cooling loads for each strategy. In addition to the energy storage systems, the case study in this paper focuses on flexible cooling loads as a significant consumer in the system. According to the findings, the system's operating costs increased by 19.4% when reserve limitations were placed. Furthermore, the findings demonstrated that when flexible assets were permitted to participate in the reserve market, they generated significantly higher incomes. According to the findings, mechanisms that will allow energy storage and demand response to provide reserve capacities as well as the growth of reserve markets are both necessary. [ABSTRACT FROM AUTHOR]

• HRES with PV-Wind and different types of energy storage systems. • Optimal size and efficient performance of HRES. • Bi-level mixed integer nonlinear programming optimization approach. • Real application of a stand-alone HRES in a real case study, Jordan. This paper aims to design and run a standalone hybrid renewable energy System (HRES) feeding residential building load. The suggested HRES encompasses photovoltaic panels and wind turbines as energy sources, combined with a hydrogen subsystem and a bank of batteries for energy storage. The meteorological input data includes irradiance, temperature, and wind speed for four seasonal weeks. These data sets are collected for a rural site situated in the town of Ras Munif, northern Jordan. The load profiles characterize a selected benchmark residential building. Consequently, a bi-level mixed integer nonlinear programming (BMINLP) problem is formulated to incorporate the designing problem with the energy management process. The upper level represents the sizing problem, while the lower level problem denotes the energy management strategy (EMS). Each problem has its independent objective function, constraints, and optimization variables. The EMS is an economic-based single objective optimization problem expressed as a mixed integer linear programming (MILP) problem. On the contrary, a mixed integer nonlinear programming (MINLP) approach frames the sizing problem to optimize a techno-economic-based multi-objective function. The interaction between the two problems is that the lower problem is an embedded constraint of the upper problem. Moreover, the candidate solutions from the upper problem are treated as fixed parameters in the lower problem. A multi-objective genetic algorithm is used to execute the overall problem by the MATLAB toolbox. The technical and economic performance parameters, including the investment cost, maintenance, operating costs, and others, are assessed based on the best findings. The key finding demonstrates that the summer week has the lowest total cost and energy loss factor, with around 132,000 $ and 0, respectively. Furthermore, the findings reveal that the entire system's energy loss factor for each sample period is less than 0.0009. This value is substantially less than the permitted limit of 0.01. [ABSTRACT FROM AUTHOR]

[Display omitted] • Feasibility of using organic wastewater as renewable energy source is verified. • ＞99% COD, TOC removal rate in the experimental platform. • Up to 78.75% of the energy recovery efficiency of the SCWO system. The degradation of high concentration organic wastewater and the recovery of energy using supercritical water oxidation (SCWO) technology have the potential to become viable in the future. High concentration organic wastewater contains a significant amount of energy. This paper focuses on utilizing high concentrated wastewater as a renewable energy source, from an energy system perspective, an experimental rig was designed to determine the optimal working conditions. The experiments were conducted with an oxidation coefficient of 1.1, a flow rate of high concentration organic wastewater of 9 ml/min, a heating temperature of 400 °C, and a reaction pressure of 25 MPa. Under these conditions, the COD and TOC removal rates of the high concentration organic wastewater were found to be 99.383 % and 99.876 % respectively. Additionally, the phenomenon of "Abnormalities in pressure sensitivity" observed during high concentration organic wastewater the experiment was further explained through additional experiments. Finally, by comparing the experimental energy recovery with the simulation results, an energy recovery efficiency of 78.95 % was achieved. The feasibility of the simulated energy recovery in practice was verified, confirming the potential to convert the previous energy-consuming wastewater treatment process into a productive one. This study provides a theoretical and experimental foundation for further related research. [ABSTRACT FROM AUTHOR]

• Province-level grid parity potential of wind and solar PV power plants in China. • Techno-economic feasibility of baseload supply in hybrid renewable energy system. • Correlation analysis of system cost and resource potential and complementarity. • Projected Grid parity potential of renewable energy system for baseload supply. To promote the large-scale deployment and grid integration of renewable-based power system, this paper investigates the province-level techno-economic feasibility of wind-photovoltaic-battery hybrid renewable energy system (HRES) for baseload supply application around China. Firstly, the power generation cost and grid parity potential of province-level standalone wind and photovoltaic power plants are assessed. Then, the optimal sizing of province-level HRESs aims to minimize the net present cost and meet the reliability constraint for baseload supply, which is solved by teaching and learning-based optimization. Finally, the techno-economic comparison between different system configurations, the correlation between HRES cost-effectiveness and resource potential as well as resources complementarity, and the grid parity potential of HRES for baseload supply are quantitatively analyzed. The results reveal that: (i) 84.4% of regions in China can achieve solar photovoltaic plant-side grid parity in 2022, while only 15.6% of regions can achieve wind power plant-side grid parity; (ii) HRESs in all regions are technically feasible but not cost-effective for baseload supply; (iii) wind-photovoltaic-battery HRES is the optimal configuration for most regions, indicating that the wind-solar hybridization is more reliable and cost-effective than standalone power plants; (iv) the economic performance of HRES depends mainly on the wind-solar joint resource potentials and the supply-demand relative deviation; (v) investment cost reduction and utilization of energy curtailment are promising to help HRES achieve plant-side grid parity for baseload supply. The findings of this paper can help policy-makers and investors optimally determine the national pathway of renewable energy transition. [ABSTRACT FROM AUTHOR]

• An innovative hybrid solar-biomass system in a multi-family building was studied. • Deep reinforcement learning was applied to improve the control of the system. • Energy consumption was reduced by 35% in winter compared to a standard control. • No significant energy savings were obtained in summer despite innovative elements. Concerns related to climate change put renewable energy at the centre of most of the policies aimed at achieving a deep decarbonisation of the building sector. The combined use of two or more renewable energy sources in the same energy system can lead to an increase in the total share of renewable energy and in the flexibility of the system. In this direction, the SolBio-Rev project aims to develop an innovative system that uses solar thermal collectors and a biomass boiler to meet energy demand in buildings in different climatic regions. An advanced control that used deep reinforcement learning techniques was considered in this paper to find an optimal control strategy for a specific SolBio-Rev system installed in a standard multi-family residential building located in Madrid. The advanced control was developed to minimize the total cost of operation of the system. The results indicated that the advanced control strategy achieved a cost reduction of 35% in winter, compared to a standard rule-based control strategy. However, the improved control was not able to produce a significant cost reduction in summer. [ABSTRACT FROM AUTHOR]

• Optimal solution to harness the unexploited potential renewable energy sources. • Heuristic optimization with dragonfly algorithm for renewable system sizing. • Economic assessment to achieve low net present value with higher reliability. Globally, most solar and wind power systems can produce power cheaper than fossil fuel-powered systems under certain circumstances according to the international renewable energy agency (IRENA). Despite that, the penetration rate of renewable energy has slowed down recently due to its non-availability and reliability in providing an uninterruptible power supply. A hybrid renewable energy system (HRES) with the conventional grid to counter the intermittency challenges without battery storage is a way forward for a greener solution. In this paper, unutilized rooftop space and underutilized potential locations of an educational institution are customized for renewable Solar-Wind power generation together with the conventional grid for effective and cost-optimal power solutions. A modified dragonfly algorithm (MDA) was adopted for mathematical modeling to reduce the power systems' net present value (NPV) over its lifespan. The model reckons various scenarios and found that the HRES with grid interaction is the best case to significantly improve the reliability economically. The result is encouraging to promote HRES in potential institutions to boost the growth of renewable energy, economically to achieve the net zero emission goal of IRENA by 2050. [ABSTRACT FROM AUTHOR]

• Use the P-graph approach to provide optimal and near-optimal solutions. • Integrate battery storage and hydrogen into renewable energy systems. • Hydrogen storage reduces energy system costs by 21.5% and battery storage by 5.3%. • Provide environmental cost of CO 2eq emission from the island energy system. • Sensitivity analysis can be used to support practical applications. Renewable energy systems play an important role in alleviating environmental pollution, and their characteristics, including low emissions and recyclability, are highly favourable. At present renewable energy can be costly and renewable energy systems have room for optimization, particularly systems which cater to remote and island areas. This paper develops a P-graph-based multi-period energy model, using hydrogen for energy storage to satisfy the fluctuating electrical and thermal energy demand of an island. Hydrogen can be generated from renewable energy sources during off-peak periods and can be used to serve as an energy carrier. An economic and carbon footprint analysis of the system is performed, which compares a pure renewable energy system, with hydrogen storage, and with battery storage. Within the same scenario, the results show that the renewable energy systems with hydrogen storage and battery storage are 21.5 % and 5.3 % cheaper than the renewable energy system without energy storage, with CO 2eq emissions of 1,717 t/y and 1,680 t/y. These findings show that the inclusion of energy storage systems has great potential to reduce costs within renewable energy systems. Changes in the supply of biomass were investigated (which had the greatest impact in the study area), as well as changes in the cost of hydrogen storage. In addition to the optimal solution, near-optimal solutions were also suggested to provide well-rounded guidance for implementation. [ABSTRACT FROM AUTHOR]

• A mixed-integer nonlinear programming optimal siting and sizing energy stations and networks model is proposed. • The multi-objective synergy planning minimizes total annual costs and total electricity abandonment rate. • NSGA-II and TOPSIS can be used to solve the Pareto solution set and best compromise solution. • Three scenarios are carried out for synergy planning in terms of energy interaction and equipment selection. • Potential benefits of the proposed method are visualized, discussed and analyzed. Regional integrated energy system (RIES) contains multiple energy coupling equipment and differential energy demand, which demonstrates that establishing a complete source-grid-load-storage energy supply chain is conducive to renewable energy consumption, and improves RIES economy and energy utilization efficiency. This paper proposes a synergy planning approach for RIES energy stations (ESs) and pipeline networks (PNs) with energy interaction and equipment selection. First, this paper analyzes a RIES structure involving equipment selection and energy interaction, and describes the problem to be addressed in this paper. Secondly, ten equipment output models are built based on energy coupling methods, and a RIES synergy planning model is further developed to minimize the annual total costs (ATCs) and the total electricity abandonment rate (TEAR) with various constraints. Subsequently, Elitist Non-Dominated Sorting Genetic Algorithm (NSGA-II) and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) are applied to solve the Pareto solution set and best compromise solution (BCS) of this mixed-integer nonlinear model (MINLP), respectively. Finally, optimal planning combinations are selected in three scenarios so as to verify the feasibility and validity of the proposed models and method. Innovations as well as further extensions of the proposed methods, are also discussed. Optimal equipment selection and output strategy help reduce 52.42% ATCs and 19.81% TEAR. Moreover, with considerations for energy interactions, RIES synergy planning achieves higher excess electricity consumption efficiency and further 1.40 M$ savings. [ABSTRACT FROM AUTHOR]

• Methodology for the simultaneous optimization of the design and operation of MESs. • Multi-objective optimization based on life cycle energy and economic assessment. • Life cycle energy saving of 17%, compared to a conventional plant. • Total cost reduction of about 18%, compared to a conventional plant. • The proposed methodology significantly reduces the computational time. Multi-generation energy systems could mitigate global energy consumption, carbon emissions and economic costs. The promising energy, environmental and economic advantages of these systems are greatly dependent on their design and operational strategy. Consequently, methods and guidelines for the optimal design and operation of such systems, also taking into consideration their life cycle, are needed to fully exploit their potential. This paper proposes a general methodology for the simultaneous optimization of the design and operation of multi-generation energy systems by considering life cycle energy and economic assessment. The design optimization problem is solved by means of surrogate modeling and the operation optimization problem by means of dynamic programming. The multi-generation energy system considered in this paper comprises renewable energy systems, fossil fuel energy systems and energy storage technologies. Different multi-objective optimizations were performed by considering the minimization of fossil cumulative energy demand, and total investment and operational costs. The validity of the proposed methodology is demonstrated by using the campus of the University of Parma (Italy) as a case study. Compared to a conventional plant, the optimal solution allows a life cycle energy saving of about 17% and total cost reduction of about 18%. Moreover, compared to an optimization method based on particle swarm optimization and dynamic programming, the proposed methodology provides comparable results, but the computation time is 78% lower. The proposed methodology outperforms commonly used optimization algorithms and provides an effective and flexible framework for the optimal design and operation of multi-generation energy systems. [ABSTRACT FROM AUTHOR]

• A comprehensive review has been done for solar assisted air source heat pump. • Solar collectors, thermal energy storage and defrosting methods are briefly reviewed. • The performance data of different type heat pumps are compiled and compared. • Evolutions require new-generation energy efficiency and green refrigerants. Solar assisted air source heat pump shows great potential as a promising energy-saving heating technology, which integrates solar collector and air source heat pump. It is widely considered for supplying hot water, space heating and/or space cooling in the domestic sector. The performance of solar assisted air source heat pumps can be evaluated in system level by parameters such as coefficient of performance, seasonal performance factor, energy consumption, solar fraction as well as initial and operating costs, and in component level by parameters such as efficiencies of solar collection and thermal energy storage. Their performances are affected by many factors such as system configuration, components size, working fluid, working conditions and weather conditions. This paper presents a comprehensive review on the recent advances in solar assisted air source heat pump for the domestic sector in terms of system configuration, solar collectors, thermal energy storage, defrosting method and the perspective areas of further investigations. The results of this review confirm that research is still required to improve the performance of such a combined system and reduce initial cost compared with existing heating systems based on hydrocarbon combustion. The information presented in this paper is beneficial to the researchers, small and medium-sized enterprises suppling renewable energy system technologies, heating engineers and service workers, energy policy and decision makers, environmental activists and communities. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel system for production and storage of H 2 with net-zero carbon emissions is developed. • High-temperature fuel cells and biogas upgrading unit are efficiently integrated. • Waste heat of the fuel cells is recovered in the Cu-Cl unit for hydrogen production. • Integrated process can generate 108 kmol/h liquid hydrogen and 18.88 MW power. • A hybrid method of the GA and artificial intelligence tools is applied for optimization. Global energy consumption has been exponentially increasing, leading to the depletion of conventional energy sources and a considerable increase in greenhouse gas emissions. The exploitation of sustainable energy sources and the development of innovative methods for mitigation of CO 2 emissions is necessary. Hydrogen (H 2) as a versatile and green fuel can be produced and stored in liquid form using sustainable energy sources through innovative methods. In this paper, a novel optimal hybrid structure is proposed for hydrogen production and storage with net-zero CO 2 emissions. A high-temperature fuel cell is utilized to reduce CO 2 emissions and supply the heat and power needed to produce and liquefy hydrogen. The hybrid configuration employs an electro-thermochemical unit for hydrogen production, molten carbonate fuel cells, a hydrogen liquefaction process, and a biogas upgrading by water scrubbing. A robust combination of meta-heuristic algorithms and artificial intelligence is developed to optimize the investment return period and energy/exergy efficiencies. The fuzzy Bellman-Zadeh, LINMAP, and TOPSIS techniques are also used to make decisions in multi-objective optimization. This innovative configuration generates 108 kmol/h liquid hydrogen, 18.88 MW power, 54 kmol/h oxygen, and 3258 kmol/h hot water. Pinch, sensitivity, exergy, and economic assessments are implemented to evaluate the performance of the hybrid structure. The thermal and exergy efficiencies of the proposed configuration are obtained to be 78.21 % and 64.83 %, respectively. The greatest portions of destructed exergy are resulted from the fuel cells-gas turbine hybrid system (63.63 %), electro-thermochemical unit (25.96 %), and biogas upgrading technology (6.23 %). The returns period on investment, the prime price of electricity, and the net benefit are computed as 4.854 years, 0.0420 US$/kWh, and 15.73 million US$/years, respectively, based on the energy potentials of Newfoundland and Labrador, Canada. [ABSTRACT FROM AUTHOR]

• Synergistic between renewable energy and cogeneration is an ideal transition path. • Imported and exported power could reduce the CO₂ emissions of the heating system. • Investment costs mainly affect the economy of the future heating systems. • Taken Beijing as a case study, the proposed method can be applied to other regions. In response to climate change, China has set the target to achieve carbon neutrality by 2060. The large-scale development of renewable energy and the decarbonization transition of the heating system are crucial for achieving this target. Is there a synergistic effect between the heating system's decarbonization transition and the use of large-scale renewable energy sources? What effect does this synergistic development have on the CO₂ emissions and the economic costs of an energy system? This paper conducts a case study of Beijing, China, and designs three technical path scenarios for heating system decarbonization transition in the future, namely, business as usual scenario where existing policies and regulations are applied, the electricity substitution scenario where the traditional fossil fuel heating system is replaced by electric heat pump, and the synergistic development scenario where the existing thermal power units are retrofitted to replace the consumption of fossil fuels with renewable energy sources. Using the EnergyPLAN model, the hourly operation of Beijing's power and heating systems under the three scenarios are simulated. The research results are: Firstly, the proportion of local renewable energy will be over 70% in all three scenarios, and in the synergistic development scenario, the electricity and heating demand can be met by 100% renewable energy, reducing CO₂ emissions resulted from fossil fuel combustion; secondly, in view of the real-time match of power supply and demand in the power system, at times renewable energy supply would exceed demand. The rational use of the surplus renewable energy can promote further the synergistic development of decarbonization transition of heating system and renewable energy, reducing the primary energy consumption and CO₂ emissions by over 16% and 28% respectively in the future heating system; Thirdly to improve the economic benefit of a synergistic electric power and heating system, focus should be on the reduction of infrastructure construction cost rather than the reduction of fuel consumption. The proposed method can be extended to regional energy systems with more energy sectors, and can be used to formulate decarbonization transition schemes for industry, agriculture, etc. [ABSTRACT FROM AUTHOR]

[Display omitted] • A comprehensive study on renewable energy resources in North America is conducted. • A detailed evaluation of renewable energy potentials is provided. • Important steps for better use of renewable energy resources are summarized. • Emerging technologies for development and management of renewable energy are addressed. • Theoretical and practical challenges in development of renewable energies are highlighted. Energy is an important drive for the economic development and social growth. The energy demand has remarkably escalated due to the technological developments in various governmental, industrial, and municipal activities. The fast growing rate of the energy demand as well as the fuel prices, along with the necessity to control the greenhouse gas emissions are the leading driving forces for effective exploitation of the renewable energy resources. In fact, satisfying the growing global energy demands and mitigating the climate change are of the utmost importance in the modern days. In this review paper, a detailed overview of the development and evolution of the renewable and sustainable energy sources is provided in terms of their types, characteristics, applications, production processes, advantages and disadvantages. Moreover, we discuss the impacts of the renewable energies on health and environment, along with the relevant policies and regulations. Further, the emerging technologies and theoretical and practical challenges in the development of the renewable energies are analyzed. Particularly, this review provides information on renewable and sustainable energies' status and prospects in North America. Central large-scale technology and distributed configurations of the renewable energies might be improved in the North American countries to effectively utilize the renewable energies for producing electricity, biomass-based fuels, and heating in both local/rural and industrial divisions. In addition to employment opportunities stemmed from manufacturing of the renewable energies, its significant impact on the economic development can be enhanced in the US, Canada, and Mexico through development of the renewable energy sources. [ABSTRACT FROM AUTHOR]

• State of the art of the Power-to-X options is discussed. • Power-to-X definitions and options are discussed. • Particular attention is given to Power-to-X options in Germany. • Multicriteria evaluation of the Power-to-X options is conducted. Hydrogen is a versatile energy carrier studied and considered to substitute fossil fuels since the seventies after the first energy crisis. Later, a second hydrogen wave due to another crisis occurred. Currently, the world is discussing the third hydrogen wave, for which, unlike the other two waves, its driving force is not the lack of fossil fuels but the imminent climate change. The hydrogen economy is expected to answer the energy storage challenges created by fluctuating electricity generation from renewable energy sources and provide a solution for the decarbonization of high energy demand sectors and the synthesis of many chemicals. Today, governments around the globe are committed to scale-up the hydrogen economy; more than 30 nations have launched a National Hydrogen Plan or Strategy. The hydrogen economy functions with a Power-to-X (PtX) versatile system. Power-to-X ("X" as an energy carrier) refers to hydrogen produced via a carbon-free process and the further storage of this element either as pure hydrogen or converted to an energy carrier that can easily be stored, transported, and used, such as ammonia, methanol and other liquid organic hydrogen carriers. This paper conducts a literature review of the political commitment regarding the hydrogen economy, the status of PtX technologies, and development worldwide. It also compares four different scenarios for green hydrogen storage using various criteria. Power-to-Ammonia, Power-to-Methanol, Power-to-Hydrogen blended with natural gas, and Power-to-Liquid hydrogen are evaluated. Conclusively, the four concepts have their advantages and disadvantages, depending on the specific application and related scenario. Germany sponsors most of the research associated with PtX and is the country with the most advanced PtX projects. Therefore, Germany was chosen as a study case for multicriteria evaluation of PtX technologies. Power-to-Ammonia appears to be the best solution. [ABSTRACT FROM AUTHOR]

• A comparison between energy communities modelled as aggregation of prosumers. • A multi-objective optimization of the design and operation of energy communities. • Demand Side Management as a powerful tool for improving the energy community design. • Reduction in the cost of energy and CO 2 emissions of 14% and 24%, respectively. • Community demand management enhances the exploitation of renewable energy sources. This paper focuses on three different configurations of energy communities (ECs) modelled as aggregations of local prosumers of renewable electric and thermal energy. The goal consists in improving the economic performance of the ECs while contributing to address the issue of climate change and fulfilling the existing energy demands or demands modified with smart strategies. Accordingly, type and size of the energy conversion and storage units of the prosumers included into ECs (design) and their operation are optimized with a bi-objective approach, considering investment and operation costs, and greenhouse gas emissions, both direct due to fuel burning, and indirect due to life cycle, as objectives to minimize. Moreover, two strategies of demand side management (DSM) are considered: a price-based demand response program applied downstream of the design optimization, and a new DSM model, which adapts the electricity demand to the renewable energy sources locally available, applied upstream of the design optimization. It results that the proposed DSM can ensure a better balancing between generation and demand profiles, thereby decreasing the stress on the electricity grid. Globally, ECs can reduce their energy expenditure of 14% and the overall CO 2 -equivalent emissions of 24% compared to the reference case of the simple consumers. [ABSTRACT FROM AUTHOR]

• A new PV sizing optimization methodology based on a period-ahead operating-scheduling algorithm is proposed. • The influence of the period ahead on the performance of the PV-diesel HPGS is assessed. • PV system integration leads to the enhancement of the Diesel Gensets operating conditions. • Tinelkoum diesel-only PGS hybridization is cost-effective with an optimal PV capacity ranging between 650 kWp and 750 kWp. • The findings of the present work will helpfully serve as a guideline for similar cases worldwide. With the increasing threats caused by fossil fuels consumption, Hybrid Power Generation Systems (HPGS), which combine Renewable Energy Sources (RES) and conventional ones, are gaining an increasing interest as they ensure a sustainable and cost-effective way to electrify rural and remote areas namely via mini-grids. However, a detailed assessment of the technical challenges and economic factors involved by such integration is essential to optimally size those HPGS. This study aims to determine the optimal storage-less PV system capacity to retrofit, at low penetration level, existing large-scale multiunit diesel-based Power Generation System (PGS) regarding the lowest Levelized Cost of Electricity (LCOE). Since excessive cycling of large-size Diesel Gensets (DGs) is fuel-intensive and increases maintenance expenses, the proposed methodology is based on a period ahead DGs operating-scheduling algorithm. The paper assesses, thereby, the effect of this period ahead length on the annual values of cumulative number of DGs operating hours, DGs loading factor, number of DGs starts as well as total fuel consumption for both diesel-only and PV-diesel systems. These operational outputs are then introduced into the system economic modeling to calculate its LCOE for each value of the PV system capacity. Simulation results of the developed optimization methodology, using data of the existing diesel-based PGS supplying Tinelkoum village in the Great Algerian South and its realistic hourly load profile recorded during the whole year of 2019, reveal that the choice of the operating-scheduling period ahead is a trade-off between the fuel consumption and the total number of DGs starts. Also, technical constraint of minimum DGs loading factor is observed to be better met when the PV system is integrated. According to the present study, Tinelkoum diesel-only PGS can host an optimal storage-less PV capacity of 650 kW p to 750 kW p depending on the period ahead. The optimal PV system will, thus, share for 1 h, 4 h and 8 h periods ahead respectively 19.94%, 19.54% and 19.10% of the resulting PV-diesel HPGS annual energy balance allowing a cost-saving, compared to diesel-only system, of 13.32% (0.275 $/kWh vs. 0.317 $/kWh), 12.53% (0.282 $/kWh vs. 0.323 $/kWh) and 11.91% (0.288 $/kWh vs. 0.327 $/kWh) for the three periods ahead respectively. Finally, the influence of fuel price and PV investment cost on the optimal PV capacity and, thus, the LCOE of the resulting HPGS has been analyzed. As it highlights the propitious opportunities of harnessing the solar PV potential endowing the Great Algerian South localities, the present work will helpfully serve as a guideline for the ongoing hybridization projects of their exiting fossil fuels-based PGS and eventually similar cases elsewhere. [ABSTRACT FROM AUTHOR]

[Display omitted] • Liquefaction is promising approach for long distance H 2 storage and transportation. • Commercial H 2 liquefaction plants have specific energy consumption of 10–12. kWh / kg LH 2 . • Increased number of ortho-to-para converters increases the process complexity. • Mixed refrigerant cascaded process with only two catalytic converters is proposed. • Hydrogen is liquefied at the expense of 6.45 kWh / kg LH 2 with 47.2% exergy efficiency. To reduce CO 2 emissions and address climate change concerns, most futuristic studies investigating 100% renewable energy sources and subsequent power-to-gas/fuel/liquid/X technological developments have been based on hydrogen (H 2). The long-term storage and transportation of H 2 over long distances restrict its feasibility as an energy vector, mainly due to its low energy density. Liquefaction is a promising approach for overcoming these issues. However, it requires a large amount of energy, and if H 2 itself is used to provide this energy, then 25% to 35% of the initial quantity of H 2 is consumed. The existing H 2 liquefaction plants have specific energy consumption values in the range of 10–12 kWh / kg LH 2 and exergy efficiencies in the range of 20%–30% with complicated configurations. Therefore, a thermodynamically efficient and compact design is required to facilitate a roadmap to H 2 economy. This paper proposes a simple, energy-efficient, and cost-effective process for H 2 liquefaction. Three refrigeration cycles with optimal mixed-refrigerant compositions are used, which makes the proposed process energy-efficient. Additionally, two-stage ortho-to-para conversion makes the process compact. The proposed process is unique in terms of its configuration and mixed-refrigerant combination. The modified coordinate descent approach was adopted to identify the optimal design variables for the proposed H 2 liquefaction process. The proposed process consumes an energy of 6.45 kWh / kg LH 2 , which is 36.5% and 16.1% lower than that consumed by the base design of the proposed process and a published base case, respectively. Additionally, the exergy efficiency of the proposed process is 47.2%. This study will help process engineers achieve a sustainable green economy by improving the competitiveness of H 2 storage and transportation over long distances. [ABSTRACT FROM AUTHOR]