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Pulp and paper industry is a water-intensive industry. This industry commonly produces considerable amount of effluent, especially from virgin raw materials processing. The effluent, namely pulp and paper mill effluent has the potential to adversely affect the receiving watercourses. However, the nutrients in the pulp and paper mill effluent could be reused as a substrate in biohydrogen production. In this study, photofermentative biohydrogen production was investigated using Rhodobacter sphaeroides and pulp and paper mill effluent as a substrate. An application of low power ultrasound on R. sphaeroides was predicted to increase photofermentative biohydrogen production but excessive ultrasound effects might inhibit the production due to possible cell disruption. Hence, various ultrasonication duration (5, 10 and 15 min) and amplitude (15%, 30% and 45%) were applied on the bacteria to determine the recommended ultrasonication conditions for improving biohydrogen production. The recommended conditions were operated at ultrasonication amplitude and duration of 30% and 10 min, respectively. A maximum biohydrogen yield of 9.62 mL bioH 2 /mL medium was obtained under this condition, which was 66.7% higher than the result obtained using R. sphaeroides without undergoing ultrasonication (control). The light efficiency and cell concentration were increased by 67% and 150%, respectively, using ultrasonication amplitude and duration of 30% and 10 min, respectively as compared to the control. The present results demonstrated that moderate power of ultrasonication applied on R. sphaeroides was an effective method for enhancing photofermentative biohydrogen production using raw pulp and paper mill effluent as a bioresource. [ABSTRACT FROM AUTHOR]

• A model predictive control-based energy management for an electro-thermal microgrid. • The strategy minimizes operating costs and pollution avoiding battery degradation. • Analyze the state of health of the battery system to reduce degradation. • A comparison with a Unit Commitment approach under different generation scenarios. Access to electricity is a fundamental key to developing countries' growth. Microgrids (MG) have become potential solutions to provide energy to isolated rural areas in a safe and environmentally friendly way. Therefore, proposals for alternative solutions to bridge the electrification gap in the Ecuadorian Amazon – which has the most significant percentage of its population without access to electricity – are of significant interest. Consequently, this paper presents the design of an Energy Management System (EMS) based on Model Predictive Control (MPC) for an isolated electro-thermal microgrid comprising a photovoltaic generator, a diesel generator, a lithium-ion battery Energy Storage System (ESS), electrical loads, and a domestic hot water system. The EMS aims to supply energy reliably and safely, minimize the MG's operation costs, and extend the ESS's useful life while satisfying the end users' comfort. This study includes an estimated degradation model for the ESS's State of Health (SOH), an essential parameter contributing to reducing the microgrid's operating costs in the long term. Simulation results using one-year data present the influence of the prediction horizon on the MG's scheduling. In addition, the benefits of the proposed EMS are highlighted by comparing it with the results achieved by a Unit Commitment approach, where it is demonstrated that the proposed EMS presents a reduction in MG operating costs and greenhouse gas emissions while maximizing the utilization of renewable energy and extending the lifespan of the ESS. Finally, an experimental validation, using a Typhoon Hardware-in-the-loop HIL-402 device in real-time operation, stands out the effectiveness and feasibility of the proposed MPC-based EMS. [ABSTRACT FROM AUTHOR]

The maturation of distributed energy resources (DER) has prompted the exploration of their deployment in commercial building applications due to their potential to supply energy at lower costs and emissions rates compared to centralized generation. While several software tools exist for evaluating the techno-economic potential of integrated renewable energy and combined heat and power (CHP) systems for distributed generation applications, many suffer from poor accuracy in capturing off-design (part load and changes in ambient air temperature and pressure) performance characteristics of microturbines, combustion turbines, or internal combustion engines. Thus, this paper presents a methodology for integrating these off-design characteristics in the mixed-integer linear program within REopt, a hybrid DER screening tool. The economic impact of the CHP off-design performance is observed through several application studies of various hybrid system configurations in different climates. Each study indicates how CHP off-design performance influences optimal sizing and dispatch decisions and therefore overall system economic value. We observe through case studies that modeling without the off-design effects, depending on the CHP prime mover and site, can result in Net Present Value predictions of hybrid systems that can be overoptimistic in frequently hot climates (up to 52 %), too conservative in frequently cold climates (up to 11 %), or unaffected (＋/−1 %) in temperate climates. Cases also highlight several advantages of hybrid systems relative to non-hybrid systems such as total economic value and the systems' ability to mitigate potentially negative consequences attributed to off-design performance. • A methodology for off-design performance as a function of load and ambient conditions is presented. • Scenarios where different application climates affect optimal sizing and dispatch are provided. • Not including off-design CHP modeling can result in overly optimistic or conservative economics. • Higher economic values for hybrid systems compared to either renewable energy or CHP-only systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • SAMA, a new open-source microgrid optimization software, was introduced an validated. • Validation compared SAMA's results with industry-standard, Homer Pro proved accuracy. • Results for different locations and climates, confirming SAMA's reliability and accuracy. • SAMA introduces unique emission optimization and top-down pricing methodology for first time. • SAMA is open-source and free, which ensures accessibility and fosters innovation. • SAMA is broadly applicable for renewable, off-grid, grid-tied, and backup power systems. Although there are many software tools for simulations of hybrid energy systems, Homer Pro and Homer Grid are the only tools offering optimal sizing of hybrid energy systems. Originally developed as open-source software, they have been closed, which limits user-developers abilities to adapt and improve the software. In addition, all current proprietary offering suffer from the following limitations: i) high costs that limit accessibility to low-resource labs and individuals, ii) incapable of conducting multi-objective optimization, iii) constrained on any new innovations in hybrid energy system design and operation, iv) difficulties for users to specifically define prices and costs in inputs, v) inability to model different electric utility billing structures, vi) complex pricing methodology, and vii) the absence of machine learning-based predictive modeling. To overcome these limitations, this paper introduces and validates SAMA (Solar Alone Multi-objective Advisor), an open-source microgrid optimization software program designed to optimize hybrid energy system sizes economically using metaheuristic algorithms based on specific load profiles and meteorological data. Through rigorous validation exercises, SAMA's outcomes are compared against those generated by the Homer Pro software across distinct climatic conditions and geographical locations (i.e., Sacramento, California in the marine west coast and New Bern in humid continental climate zones of U.S., respectively). The results demonstrate congruence between SAMA and Homer Pro. SAMA can be used for a diverse array of applications from renewable energy systems to off-grid and grid-tied configurations, and from policy formulation to feasibility assessment. Unique features of SAMA include multi-objective optimizer, levelized emission optimization, different pre-defined utility billing structures, and a top-down pricing methodology. These features further enhance SAMA's adaptability, allowing users to tailor the software to their specific needs and system configurations. Finally, the paper anticipates future advancements that could refine component modeling, accelerate optimization processes, and incorporate advanced data analysis techniques such as machine learning to predict energy demand and production patterns. [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] • Biodiesel's Generational Evolution: 2000–2022. • Progress in Sustainable Biodiesel Production Methods. • Influencing Factors Explored: Policies to Feedstocks. • Diverse Feedstock Sources Enabling Efficiency. • Reactor Technologies Shaping Biodiesel's Future. In response to the increasing demand for diesel fuel and its shortage, biodiesel has emerged as a potential alternative. This review thoroughly examines the physicochemical characteristics of biodiesel from several generations using a variety of feedstocks. The study reveals that biodiesel with low concentrations of polyunsaturated fatty acid methyl esters (FAME) and long-chain saturated FAME exhibits favorable characteristics, including improved performance, oxidation stability, and operability at low temperatures. Many technologies have been used to produce biodiesel, but the transesterification process has proven to be the most cost-effective and efficient approach, producing the maximum amount of biodiesel, making it the technique of choice for commercial bio-production. The paper presents an in-depth examination of biodiesel production methods, explaining production patterns influenced by elements such as reactant mass transfer restrictions, feasibility in upstream processes, and downstream processing ease. Furthermore, third generation feedstocks, especially algae-based sources, outperform their predecessors due to their higher energy content, significant oil content, and ecologically harmless characteristics. The article additionally covers a variety of catalysts, including ionic liquid catalysts, enzyme catalysts, nano catalysts, and heterogeneous and homogeneous acid/base catalysts. Following a detailed evaluation of various reactor designs, the research concludes that using a supercritical method has tremendous promise for biodiesel synthesis. This comprehensive overview not only examines the benefits and drawbacks of various biodiesel production methods, but it also contributes to a better understanding of the factors influencing biodiesel production trends, thereby encouraging the development of sustainable and efficient biodiesel technologies. [ABSTRACT FROM AUTHOR]

The concept of shared energy storage in power generation side has received significant interest due to its potential to enhance the flexibility of multiple renewable energy stations and optimize the use of energy storage resources. However, the lack of a well-set operational framework and a cost-sharing model has hindered its widespread implementation and large-scale development. This paper introduces three distinct cost-sharing methods, namely the uniform allocation method, the predictive weighted allocation method, and the dynamic weighted allocation method, which are laterly applied to develop a combined operational and cost distribution model. The objective is to improve the efficiency of the power generation system by incorporating shared energy storage assistance and allocating the associated costs based on the use of various renewable energy stations. Furthermore, the viability of the suggested operational framework for shared energy storage and the methods for allocating costs are confirmed through numerical simulation. The findings indicate that the uniform allocation method represents the most straightforward approach for distributing costs evenly. In contrast, the second model introduces a cost allocation method that addresses the issue of fairness by considering the predicted generation level of each renewable energy plant. However, the third model takes into account the actual generation level of the plants when determining their respective costs. Sensitivity analysis is further conducted to offer valuable insights into cost-saving policies for four representative regions in China. The proposed operation and cost-sharing model is anticipated to serve as a useful reference for the widespread implementation of shared energy storage in power generation side. • Design three cost-sharing methods to allocate costs among various entities. • Formulate a combined operational and cost allocation model. • Optimize operational and cost allocation strategies for various entities. • Reduce total costs by up to 36% through the dynamic weighted allocation method. [ABSTRACT FROM AUTHOR]

[Display omitted] • Current approaches in CO 2 conversion and enhancing strategies for solar fuel generation via artificial photosynthesis. • Strategies for improving the photocatalytic activity in solar fuel generations. • Application of biochar-based photocatalysts (BSPs) in CO 2 conversion and H 2 production. • Investigating the Biochar's role in biochar-based photocatalysts. • Challenges and prospects for the future of biochar-based photocatalysts in environmental applications. The imperative of solar-driven methodologies, harnessing the virtually boundless power of sunlight, cannot be overstated in our battle against climate change and the imperative to propel clean fuel production. Photocatalytic innovation, which employs catalysts to initiate eco-friendly chemical reactions, stands out as one of these effective techniques. Biochar, a carbon-rich material derived from organic substances, enhances photocatalytic activity through its porous structure and functional groups. Using biochar as a photocatalyst support reduces electron-hole pair recombination rates, narrows band gaps, improves charge separation, and enhances electron transport. This study explores four main objectives: 1) Current approaches in CO 2 conversion and strategies, including the management perspective of light, the utilization of solar concentrators, and thermal methods for enhancing solar fuel generation via artificial photosynthesis. 2) Critical role of photocatalysis and analyzing the metals and nonmetals doping and the strategic deployment of carbon materials to increase the efficacy in solar fuel generation. 3) Methods and parameters that affect the synthesis of biochar. 4) The role of biochar as a support for improving photocatalytic activity in CO 2 conversion and H 2 production for solar fuel generation. This paper outlines a vision for advancing biochar-based photocatalysts, emphasizing the need to enhance their efficiency and stability. It also highlights the potential for innovative design concepts and the exploration of scalable production techniques. Ultimately, this vision aims to drive progress in solar fuel generation technology for practical applications. [ABSTRACT FROM AUTHOR]

• Electric vehicles charging and refueling with various renewable-based designs. • Globally applicable multi-design framework identifies the most sustainable design. • Uses a hybrid multicriteria decision method with a microgrid optimization tool. • Shows real-time case study with comparison of seven 100% renewable-based designs. • Optimal design avoids 2,455 tons of yearly carbon emissions compared with the grid. The rapid development of green charging and refueling stations is vital for the widespread adoption of fuel cell electric vehicles and battery electric vehicles. This paper investigates the challenge of selecting the most optimal autonomous station design among various 100 % renewable-based options, considering techno-economic and socio-political factors. A globally applicable systematic framework is presented, encompassing 14 performance criteria, a microgrid optimization tool, and a hybrid multicriteria decision method. Focusing on the pressing needs of Karachi, Pakistan, the study showcases the application of the framework to evaluate 7 renewable-based autonomous designs. Among these, the photovoltaic and biogas generator-powered station emerges as the most optimal option for Karachi, with a levelized cost of energy (LCOE) of 0.31 $/kWh, levelized cost of hydrogen (LCOH) of 4.281 $/kg and payback period of 8.3 years. The optimal design avoids 2,455 tonnes of carbon dioxide (CO 2)/year compared to the grid and 5,642 tonnes of CO 2 /year compared to diesel generators. When compared with the grid extension, the breakeven distance is found to be 4.6 km. Sensitivity analysis shows a 3.6 % decrease in LCOE and a 13.7 % decrease in LCOH with a 20 % increase in charging and refueling load, highlighting scalability benefits. This study contributes to various united nations' sustainability goals (7, 8, 9, 11, 12, 13), striving to provide a clear pathway for selecting optimal station designs. [ABSTRACT FROM AUTHOR]

• A two-layer framework is proposed for building HVAC and associated multi-energy consumption optimization. • 100% renewable complementarities are proposed for building multi-energy supplies. • A R-C thermodynamic network is formulated to model the building HVAC. • AC slow charging and DC fast charging types of EVs are considered and managed via a novel real-time supply–demand pricing. Building heating, ventilation, and air conditioning (HVAC) and associated energy consumption make up the more and more important part of the world, whose reduction provides a cost-effective path to the "dual carbon" goal. This paper proposes a two-layer management of HVAC-based multi-energy buildings under proactive demand response of fast/slow-charging electric vehicles (EVs). In this paper, the building HVAC is mathematically formulated via a R-C thermodynamic model, which coordinates with multi-energy converters and storages to form a 100% renewable building. The building management is a challenging optimization problem due to its severe constraints and strong spatio-temporal couplings. In the first layer, a day-ahead multi-energy dispatch is formulated to economically optimize the electrical, heat, gas energy carriers. In the second layer, alternating current (AC) slow charging and direct current (DC) fast charging types of EVs are considered and managed via a novel real-time supply–demand pricing mechanism. After acquiring the economical dispatch references in the first layer, the second layer implements a model predictive control (MPC)-based real-time scheduling to handle the multi-energy supply–demand fluctuations. The original two-layer optimization is further handled via mixed-integer linear program (MILP) reformulation for high-efficient solving. Comparisons have shown the advantageous performances of the proposed two-layer optimization over economics and practicability. Simulations results show that the overall system operating cost can be reduced by at most 3.01% with a higher operational flexibility in building management. [ABSTRACT FROM AUTHOR]

District Heating (DH) systems will play an important role in future sustainable energy systems. Existing networks can be optimized by lowering primary return temperatures in order to improve the use of geothermal resources. This can be done by installing triple-pipe systems. This paper defines the concept of triple-pipe configurations as it is understood in France. The objective of this paper is to demonstrate the relevance of those configurations for optimizing geothermal DH system efficiency. A dynamic thermal-hydraulic model was developed using the programming language Modelica. A generic case study is modeled considering the extension of an existing network. It is shown that triple-pipe configurations offer lower return temperatures and gas consumption, while increasing of the renewable energy share in the network energy mix. [ABSTRACT FROM AUTHOR]

Predicting solar irradiance has proven to be a challenging task due to its inherently unpredictable and chaotic characteristics. Although machine learning and deep learning models have demonstrated considerable success in this field, the emergence of quantum computing brings a new layer of potential to this complex problem. This paper delves into these emerging methodologies, focusing specifically on their application in the domain of solar irradiance forecasting. This study investigates the integration of quantum layers into a conventional deep feedforward neural network (FFN) and the development of a fully connected quantum neural network (QNN). A bidirectional long short-term memory (BiLSTM) model is employed as a performance benchmark. Among the various models developed within this study, a few have demonstrated notable performance. For example, an FFN composed of five regular layers and two quantum layers (FFN5L2Q), having a total parameter count of 339, generated an error rate of 6.737%. Conversely, another FFN model, featuring eight regular layers and one quantum layer (FFN8L1Q) and having a total parameter count of 5551, exhibited superior performance with an error rate of 4.254%. When compared to the BiLSTM model, which has 49,666 parameters and an error rate of 3.875%, these quantum-enhanced FFNs display robust and competitive performance. This study, therefore, emphasizes the promising prospects of quantum-integrated techniques in augmenting the precision of solar irradiance prediction models. • Quantum computing boosts solar irradiance predictions. • Quantum layers in Feed-Forward Networks is promising. • Hybrid model with two quantum layers achieves 6.737% error. • 8-layer Hybrid model with one quantum layer hits 4.254% error. • Quantum-enhanced model architecture impacts effectiveness. [ABSTRACT FROM AUTHOR]

• Battery transport and logistics to increase renewable use and system flexibility. • Full train transport and carpooling to improve the economics of battery use. • Levelized cost of energy of battery transport & logistics is $0.045/kWh averagely. High share of variable renewable energy is challenging to the traditional power system technically and economically. This calls for a significant increase to the system flexibility, which might result in the costs associated with energy storage and costly upgrades to the traditional transmission and distribution system. This paper presents a multi-stage battery transportation and logistics optimization method to increase the renewable energy consumptions, economics, and mobilities of the battery utilization. A new approach is proposed in which the batteries are charged in the renewable power plants and transported back and forth by railways between the renewable power plants and cities. Based on the forecasts of battery supplies/demands, multiple optimization stages (full train transport and carpooling) are designed by the branch-and-bound algorithm and genetic algorithm respectively. The proposed battery transportation and logistics concept and model are performed using the Beijing-Tianjin-Hebei region in China as an example. The results show that the levelized cost of energy of the battery transportation and logistics model is $0.045/kWh averagely. Also, by the use of mobilized batteries, the proposed battery transportation and logistics model increases the system flexibilities and renewable energy deliveries to the end users without the reinforcement of transmission and distribution system and any constraint from a highly penetrated power system. [ABSTRACT FROM AUTHOR]

• Solar photovoltaics stored by using cheap and abundant materials. • The Calcium-Looping process is integrated as electricity stored system (40% efficiency) • Electric-to-electric performance of the whole system reaches 57%. • A notable cost reduction could be achieved as alternative to batteries. Solar photovoltaic plants are today a competitive alternative to power plants based on fossil fuels. Cost reduction in photovoltaics modules, scalability and ease of installation of these plants are enabling a rapid worldwide expansion of the technology. Nevertheless, dispatchability still remains as the major challenge to overcome due the intrinsic variability of solar energy. Most of the current solar photovoltaic facilities at large scale lack energy storage while those with storage systems rely on expensive batteries. Batteries are based on elements such as nickel, lithium or cadmium whose scarcity hinder their sustainability for storing energy in the large scale. This manuscript presents a novel concept to integrate thermochemical energy storage in photovoltaic plants. Furthermore, the concept is also directly adaptable to wind power plants to store surplus energy. The paper analyses the suitability of the Calcium-Looping process as thermochemical energy storage system in solar photovoltaics plants. The system works as follows: part of the power produced in the solar plant provides electricity to the grid while the rest is used to supply heat for calcination of calcium carbonate. After calcination, the products of the reaction – calcium oxide and carbon dioxide- are stored separately. When power production is required, the stored products are brought together in a carbonation reactor wherein the exothermic reaction releases energy for power production. The overall system is simulated to estimate the process behaviour and results show that storage efficiencies of ∼40% can be achieved. Moreover, an economic analysis is developed to compare the proposed system with batteries. Due to the low price of natural calcium oxide precursors, such as limestone, and the expected longer lifetime of equipment as compared to batteries, the Calcium-Looping process can be considered as a potential alternative for improving dispatchability in solar photovoltaic plants. [ABSTRACT FROM AUTHOR]

Solar pond undoubtedly has been a reliable source of low grade heat supply by acting as both collector and storage for the incoming solar radiation. The thermal efficiency of the solar ponds is between 15 and 25% of the incoming horizontal solar radiation. Meanwhile, the thermoelectric technology enables the conversion of heat into electricity using thermoelectric modules. In this paper, the feasibility of the system by combining solar pond and thermoelectric modules is presented. This system can be achieved by using a thermoelectric modules-embedded heat exchanger module that will able to extract the heat available from the lower convective zone of the solar pond. The analysis in this paper was conducted by investigating the solar ponds operating in different climate conditions, which are Group A (Kuala Lumpur), Group B (Riyadh) and Group C (Melbourne and Granada) base on Köppen climate classification. The theoretical feasibility draws the limit on the performance and cost of the solar pond-thermoelectric system under commercially available thermoelectric technology at the present state. Later, the result was contrasted against the performance of the power generation units operate under realisable operating condition with solar pond. The result in this study revealed that, under ideal condition, the system is at least 10 times costly compared to other renewable energy sources like off-grid solar photovoltaic system with storage. Meanwhile, at its best operating climate, this system will be able to achieve annual carbon dioxide reduction of 2.38 kg/m 2 -year in a practical case. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lifecycle assessment of coal plus wood and paper waste co-firing with CO 2 capture. • Combustion modelling used to predict direct CO 2 and trace emissions. • Increasing co-firing ratio without CO 2 capture decreases CO 2 emissions slightly. • Lower global warming potential due to CO 2 capture drives a lower endpoint score. • Negative emissions achievable at more than 30 % waste co-firing with CO 2 capture. Bio-Energy with Carbon Capture and Storage (BECCS) is an emerging energy conversion technology with the potential to deliver 'negative emissions', a net removal of CO 2 from the atmosphere that may be necessary to achieve the net-zero targets adopted in the Glasgow Climate Pact at COP26. This paper uses Life Cycle Assessment (LCA) to investigate the environmental impacts of co-firing dry waste biomass (wood and paper waste) while implementing CCS technology (i.e., BECCS) in a conventional black coal-fired power plant. The LCA covers CO 2 emissions and trace contaminants, determined via combustion modelling coupled with chemical-equilibrium-based ash-forming element and trace element calculations. As a case study, the context of New South Wales, Australia, is analysed to assesses the viability and discuss policy implications of waste co-firing BECCS as a future energy source for coal-reliant regions. An increase in co-firing ratio is found to decrease emission intensity. At current typical efficiencies, BECCS with a 10 % co-firing ratio can reduce emission intensity from 938 to 181 kgCO 2 /MWh. At 20 % to 25 % co-firing, the emission intensity of BECCS is comparable with other renewable technologies, and negative emissions are achievable above 30 %, although waste availability in NSW is insufficient to achieve these levels. Moreover, BECCS increases environmental impact in all categories except for global warming potential (GWP), land use, and terrestrial acidification. Nonetheless, when aggregating all impacts, the large reduction in GWP drives an endpoint score reduction, indicating that co-fired BECCS may be preferred over sub-critical black (bituminous) coal-fired power without or with CCS, or other higher emission intensity coal-fired power generation. Therefore, policy makers should consider incentivising waste co-firing BECCS as part of future energy policies towards achieving the net-zero targets, weighing its benefits against other environmental impacts, waste availability and competition with recycling initiatives. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cradle-to-grave LCA framework for geothermal and solar-powered MD systems. • Scenarios of different MD technologies and power sources combinations are analyzed. • Electricity and heat source construction material contribute to most of the impacts. • Disposal of metal materials brings notable environmental burden in FETP and METP. • Temperatures of the feed and brine are crucial to the environmental performance. Membrane distillation (MD) is an emerging seawater desalination technology capable of utilizing low-grade heat. Many studies have been dedicated to MD systems design; however, few have offered comprehensive life cycle assessment (LCA). This paper develops a cradle-to-grave LCA framework for MD systems to shed some light on the environmental performance of MD technology. The MD systems consist of direct contact/air gap MD modules, heat exchangers, pumps, pipelines, and other equipment of heat sources. The MD modules comprise membrane, housing, condenser, and spacer. The heat sources are geothermal and solar energy, with auxiliary power from the grid and renewable energy sources. Life cycle inventories of the major components of the systems are established for the assessment. The ReCiPe 2016 method is chosen in this paper, including 18 midpoint indicators and three endpoint damage indicators. Results suggest that the major environmental impacts of renewable energy-driven MD desalination plants arise from the construction materials for the heat sources and the auxiliary power consumption in the operation stage. The environmental impacts can be reduced by 24.57%-70.79% when the auxiliary electricity supply from the grid is switched to renewable energy sources. [ABSTRACT FROM AUTHOR]

• Levelized cost metrics and costing methods for combined heat-and-power plants. • (Near) zero-marginal cost renewable energy sources are considered. • Concepts levelized cost of exergy & net present value based on exergy are proposed. • Novel concepts account for two products and temperature levels (usefulness of heat). • Application to a low-temperature geothermal combined heat-and-power plant. In this paper, several cost metrics for application to a combined heat-and-power plant fueled by a zero-marginal cost energy source are studied. The mature levelized cost concepts are extended with some novel metrics such as the levelized cost of exergy. The results are given for a geothermal combined heat-and-power plant, connected to two different types of district heating systems and for two scenarios for the heat and electricity prices (high and low). For a low price scenario, the conventional costing method based on two separate prices for electrical and thermal energy is the most appropriate. Also for a high price scenario, the conventional costing method is the most appropriate for heat demands at low temperature. However, for higher-temperature heat demands, the exergy costing method results in the highest revenues for the combined heat-and-power plant. The authors recommend the use of the novel levelized cost of exergy metric as different types of energy are priced with a single value. Depending on the amount of energy and the usefulness of the energy type, an appropriate cost can be allocated to each product of a multi-energy system. [ABSTRACT FROM AUTHOR]

Highlights • The complex EH model can be divided into several simple EH models. • The complex MES is highly decoupled. • The nonlinearity of a complex EH model caused dispatch factors can be eliminated. • The energy storage, demand respond and renewable energy are all integrated in the coupling matrix of EH model. Abstract The integration energy and information technology has prompted the development of the multi-carrier energy system. Energy hub model is widely used in the multi-carrier energy system study. However, it is the difficult to formulate coupling matrix and optimize operation state of complex energy hub model. This paper proposes an efficient standardized multi-step modelling method and linearized optimization method for the energy hub model. Firstly, a complex energy hub model is separated into several simple energy hub models based on nodes arrangement and virtual nodes insertion methods; then the coupling matrix of each simple energy hub model can be easily modelled; the coupling matrix of the complex energy hub model can be obtained by multiplying the coupling matrix of each simple energy hub model. In addition, energy storage, demand response and renewable energy are considered and integrated in the energy hub model. Further, the nonlinear optimal operation model of energy hub is reformulated to a linear programming problem by using variable substitution in each simple energy hub model. Cases study is performed on a resident district in a city of China on a typical summer day with the energy storage devices, demand response and renewable energy considered. Compared with the traditional calculation method, the computational burden is significantly reduced based on the proposed calculation method, which can guarantee the global optimal operation decision. [ABSTRACT FROM AUTHOR]

Highlights • Modified Savonius turbines can become a feasible solution for powering off-grid. • Most of the proposed configurations surpassed the conventional Savonius rotor by applying specific modifications. • Not complex simulated modifications to the classic Savonius rotor can increase turbine performance. • At least three novel rotor configurations stand out from the rest with performance enhancements close to 18%. Abstract It is a priority to generate affordable and reliable energy with higher participation of renewable energy technologies into the global energy mix to provide efficient sustainable energy services for everyone, highlighting the need to focus on vulnerable communities in developing countries with limited or no access to electricity. Vertical axis wind turbines (VAWT) are widely used for renewable electricity generation. In that order, Savonius rotor, being a VAWT, is commonly used because of its numerous advantages for small scale generation. Thus, wind energy research on a modified Savonius rotor might be a feasible solution for powering vulnerable communities with no access to the grid. Hence, this paper shows how to improve the performance of a conventional Savonius blade by introducing a novel configuration without expensive and complex modifications on the geometry. For that purpose, a C m and C p coefficients comparison between 13 proposed scenarios against the conventional configuration to define a novel one, with better performance is carried out through a 2D computational fluid dynamic analysis by using Ansys Fluent 18.0. The SST k-ω model is selected as the turbulent model. As a result, a higher performance Savonius novel rotor configuration is identified with 17.81% improvement over the conventional configuration. [ABSTRACT FROM AUTHOR]

Highlights • Modeling the variability of the fuel costs over long term. • Modeling the Multi-Source System taking into account changes in fuel costs. • Limiting the number of starts of the diesel generator to increase its lifecycle. • Increasing the fuel cost can lead to an increase of 18% in the design cost. • Optimization algorithm favors the introduction of renewable sources. Abstract Multi-Source Systems combining renewable energy sources with diesel generators have been widely adopted in isolated sites. The economic and ecological aspects are very important for analyzing and evaluating such systems. In this paper, an optimization approach that includes the former aspects has been proposed. This approach takes into account the changes in the fuel cost over a lifecycle and the minimization of the greenhouse gas emission. The proposed method is based on three main steps. At first, a fuel cost progression model over a period of 40 years has been developed. Second, due to the complexity of such systems and in order to simplify the modeling, meta-models have been extracted by using the Design of Experiments technique. Finally, Single-Objective and Multi-Objective Optimization of the system based on economic and ecological criteria have been performed. The obtained results show that, changes in fuel costs have a significant influence on the sizing of the system. Indeed, the increase in fuel cost can lead to an increase of 18% in the design cost. The best solution on Pareto's curve was found with a reduction rate in the fuel consumption between 30 and 35%. Furthermore, the optimization algorithm favors the introduction of renewable sources. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Use of solar chimney can reduce the semi-transparent PV temperature by up to 38 °C. • Use of solar chimney results enhances the PV generated power by around 30%. • There is an optimum packing factor that maximizes the power generation. • There is an optimal chimney height at which the best cooling effect is achieved. Abstract Semi-transparent photovoltaic (STPV) system’s performance strongly depends on its surface temperature. To provide a mechanism that decrease the temperature of STPV can improve the power generation significantly. This cooling mechanism will be more interesting if it needs no additional energy. In this paper a novel solar chimney system is proposed to cool a STPV system. The STPV is employed as a roof for the solar chimney and an air flow generated by the solar chimney cools the STPV. Based on the energy balance for three main components: STPV, air and ground, a theoretical model is developed for the proposed system. Convection heat transfer coefficients are calculated precisely for the heat transfers taking place in the system and the obtained results for the solar chimney are compared with the existing experimental data in literature. Results of proposed model have a good agreement with the previous data. It’s shown that there is an optimum packing factor that maximizes the generated power for each radiation intensity. It is observed that the proposed system effectiveness depends on the radiation intensity as well as on the structural parameters. The proposed system can reduce the average temperature of the STPV up to 15 °C. It is concluded that, by cooling the STPV power plant with the solar chimney for a solar radiation of 500 W/m2, an enhancement of about 29% in power generation is gained. [ABSTRACT FROM AUTHOR]

Highlights • Micro Gas Turbine as a valid alternative to Stirling Engine in Solar Dish Applications. • Simulation Tool for concentrated solar power plant optimal operations. • Solar to Power Efficiency up to 10% for 5 kWe net generated power. • Concentred Solar Power and Brayton Cycle Gas Turbine for distributed generation. • Genetic Algorithms and Quadratic Programming for robust and fast computations. Abstract In the scenario of the small scale 3–35 kWe concentrated solar power plant based on point receiver technologies, the dish-Stirling configuration is one of the most commonly adopted one. New and clean efficiency of these Stirling engines is typically of 30–40%. Yearly average efficiency, during the system operations, is significantly reduced to 10–15% due to the Stirling engines high maintenance costs and poor reliability issues. These drawbacks limit the small scale dish-Stirling engines market attractiveness. The adoption of cheap, reliable and widely available engines, such as micro gas turbines is a promising solution for substituting Stirling engines since it ensures constant performance over time. Since micro gas turbines for concentrated solar power plants equipped with dish concentrator have not been widely deployed, the development of a plant simulator is helpful for predicting the overall concentrated solar power plant performance and for optimizing the plant operations under different boundary conditions. The plant simulator is aimed to demonstrate the economic viability and the technical feasibility of dish-micro gas turbine systems. The paper includes the methods for developing a simulation tool for solar dish – micro gas turbine applications. The solar concentrator, receiver/absorber, micro gas turbine, high speed generator and power electronic systems have been modelled and the plant simulator has been set-up by means of a quadratic programming technique. The simulator has been used to perform steady state simulations for predicting the performance and for ensuring a safe and reliable power plant operation when the direct normal irradiation changes. The results for a net generated power of about 6 kWe have shown a nominal peak efficiency of about 10%, making this micro gas turbine solar plant layout market attractive. [ABSTRACT FROM AUTHOR]

This paper presents a grid-connected hybrid renewable energy integrated with a reverse osmosis desalination plant to provide fresh water for a residential community. The hybrid energy system comprises a photovoltaic module and wind turbine as the main source of energy, and battery storage systems or hydrogen storage systems are used as an energy storage system, while a diesel generator is used as a backup energy source. A new multi-objective hybrid Particle Swarm Optimization – Grey Wolf Optimizer (PSO–GWO) optimization method is used to obtain the optimal size of the different system components to minimize both the total cost of fresh water production and, at the same time, CO 2 emissions, for a period of 20 years. Moreover, a comparison is done between the PSO–GWO optimization method and the use of PSO alone and the use of GWO alone. The solar radiation, temperature and wind speed of the residential community are measured using the weather station system. A comparison between different hybrid system configurations using three different optimization methods is presented. The complete model for energy management strategies and the optimization models for this study are programmed using MATLAB software. The results show that the proposed PSO–GWO hybrid performs better at determining the optimization parameters than either of the same optimization methods used in isolation. The optimization results indicate that a battery storage system is more economical than a hydrogen storage system. Further reduction in cost can be achieved by incorporating a diesel generator into the hybrid system. Finally, sensitivity analyses are performed to show how varying certain parameters affects total investment cost. Such analyses have shown that the variation in annual solar irradiance has a greater impact on the total investment cost than wind speed variation. [ABSTRACT FROM AUTHOR]

The increasing number of elderly people (over 65 years of age), long-term home care policies and the generally higher energy demand of houses inhabited by elderly people will pose an energy challenge for the built environment. The paper analyses the benefits of poly-generation technologies, focusing on the case of hard to heat homes in Northern Ireland. The energy consumption of a test house that is representative of 28% of Northern Ireland housing stock and of a house with elderly inhabitants has been monitored without any intervention. An optimization procedure has been developed to identify the optimal mix of poly-generation technologies. The technologies considered are micro-combined heat and power, heat pump and photovoltaic systems with possible integration of thermal energy storage systems. Six scenarios based on different energy tariffs and technology incentives have been presented. In the best case scenario, the combination of photovoltaic, heat pump and thermal energy storage provides 26% reduction in carbon dioxide emissions and 80% savings in the energy bill compared to standard energy generation. The investment required would be in the order of £11,000. In Northern Ireland, 307,000 households (79.1% more than in 2012) will have elderly inhabitants by 2037. The adoption of poly-generation technologies in the older housing stock could lead to 8% reduction of carbon dioxide emissions of the entire residential sector, with 150 GWh increase in the electricity generation from renewable energy without affecting the electricity distribution network. [ABSTRACT FROM AUTHOR]

PV panels power conversion are strongly depending on chopper structure and maximum power point tracker algorithm, such as perturb and observe or increment conductance. In certain operating conditions these algorithms become inaccurate. The aim of this paper is the PV panel operation under partial shading. Until now it is solved by intelligent techniques (ANN, Fuzzy logic …) where the result cannot be explained and inaccurate under desert climate. It is proposed a new global maximum power point tracking based on detection and analyzing partial shading phenomena affecting PV panels characteristics behavior. The proposed DA-GMPPT permits a partial shading detection, once it appears and the location of the other maximum power points. Using this proposal the whole PV power system works at its optimal power point for any type of partial shading, even under aging effect. [ABSTRACT FROM AUTHOR]

This paper presents the geological resource potential of the compressed air energy storage (CAES) technology worldwide by overlaying suitable geological formations, salt deposits and aquifers. For this study, the world is divided into 145 regions, which are aggregated to 9 major regions. The potential of CAES in each region is assessed and a relevant map is provided. Three constraints have been implemented, allowing for 1%, 5% and 10% of the selected area to be considered for CAES. Among all major regions, in the most conservative constraint (1% of the total area), North America is the leader with 0.26% suitability of its total area, followed by Sub-Saharan Africa and South America at 0.20% and 0.19%, respectively. A sensitivity analysis is implemented to evaluate the validity and reliability of the results. Three scenarios are considered: Optimistic, Moderate and Pessimistic. Underground natural gas storage data for the US is used due to freely and publicly available data. The natural gas storage site is assumed to have the same structure as CAES. The sensitivity analysis shows that the accuracy of the findings lie in the range of 66–85% and 63–82%, depending on the scenarios and reservoir types. The results clearly reveal that CAES is a promising energy storage technology for electricity supply in most of the regions. This research presents the groundwork to identify the untapped potential of CAES, which can be also utilized for the second generation of CAES such as adiabatic CAES and isothermal CAES. [ABSTRACT FROM AUTHOR]

The concept of off-grid hybrid wind energy system is financially attractive and more reliable than stand-alone power systems since it is based on more than one electricity generation source. One of the most expensive components in a stand-alone wind-power system is the energy storage system as very often it is oversized to increase system autonomy. In this work, we consider a hybrid system which consists of wind turbines, photovoltaic panels, diesel generator and battery storage. One of the main challenges experienced by project managers is the sizing of components for different sites. This challenge is due to the variability of the renewable energy resource and the load demand for different sites. This paper introduces a sizing model that has been developed and implemented as a graphical user interface, which predicts the optimum configuration of a hybrid system. In particular, this paper focuses on seeking the optimal size of the batteries and the diesel generator usage. Both of these components are seen to be trade-offs from each other. The model simulates real time operation of the hybrid system, using the annual measured hourly wind speed and solar irradiation. The benefit of using time series approach is that it reflects a more realistic situation; here, the peaks and troughs of the renewable energy resource are a central part of the sizing model. Finally, load sensitivity and hybrid system performance analysis are demonstrated. [ABSTRACT FROM AUTHOR]

The objective of this paper is to establish a theoretical framework for the exergy analysis and advanced exergy analysis of a real biomass boiler. These analyses can be used for both the diagnosis and optimization of a biomass boiler as well as for the design of a new biomass boiler. Conventional exergy analysis is performed to recognize the source(s) of inefficiency and irreversibility and identify exergy destruction in different components of the biomass boiler. An advanced exergy analysis is performed to provide comprehensive information about the avoidable exergy destruction and real fuel-saving potential for each component, as well as the overall system. Sensitivity studies of several design parameters including the excess air, biomass moisture and steam parameters were evaluated. The results show that the maximum exergy destruction occurs in the combustion process, followed by the Water Walls (WW) & Radiant Superheater (RSH) and the Low Temperature Superheater (LTSH). The fuel-saving and exergy efficiency improvement strategies for different components are discussed in this paper. [ABSTRACT FROM AUTHOR]

• An improved operation strategy for decentralized A-CAES is proposed. • TES behavior and its effects on A-CAES performance are analyzed. • Characteristics and capacity limitations of HES's components are considered. • A parametric study showed an optimum value for the system's design parameters. • Improved operation strategy reduced the ramp-up /down rate by around 4% /11%. Adiabatic compressed air energy storage (A-CAES) has shown great application potentials in integrated hybrid energy systems (HES) in recent years. The integration requires A-CAES to store intermittent renewables power to meet the fluctuating load demand. Therefore, the operation of compressors and turbines must be adjusted by renewable power output and load demand, respectively. This paper presents an improved energy management operation strategy (I-EMOS) to enhance the A-CAES system's utilization for decentralized applications. In doing so, besides integrating thermal energy storage (TES) unit into CAES, several limitations of an A-CAES unit, such as its conversion process mode, dynamic characteristics, power input/output constraints of compressor/turbine train, air pressure constraint, and thermal storage capacity limitations are considered. An HES consisting of PV, A-CAES, and grid to answer the building's electric demand is simulated. The results are validated against data from an existing A-CAES pilot. It is concluded that adopting features and capacity limitations of the A-CAES system's power conversion unit in operational strategies contributes to improved management of energy flow in HES. It is observed that for certain air tank volume and maximum/minimum pressures under I-EMOS, an enhanced performance can be achieved. This analysis presents a feasibility assessment approach for decentralized A-CAES integrated with renewables implemented and tested in a real-world case study. [ABSTRACT FROM AUTHOR]

With recent advances in waste-to-energy technologies, the integration of municipal solid waste in energy recovery systems is becoming a promising alternative. However, it is still unclear how these technologies can be optimally combined, especially when the future price of energy and the quantity of waste are uncertain. Additionally, it remains an open question whether these uncertainties exert a notable impact on the optimal configuration and trade-off between costs and emissions of energy recovery systems. This paper studies a multi-carrier energy infrastructure to generate energy from municipal solid waste, aiming to optimize the selection and size of waste-to-energy technologies. To account for uncertainty in heat, electricity, and hydrogen prices, as well as waste supply in the future, a two-stage robust optimization model is proposed to minimize the total annual cost (including an environmental penalty) of the waste-to-energy facility. On a real test case in Nova Scotia, Canada, the solution obtained from the robust model led to a 19.9% decrease in emissions compared to that of the deterministic model, albeit with an increase in total cost under the current prices. Plasma arc gasification is selected as the optimal technology in the deterministic case, but pyrolysis outperforms it when the cost of hydrogen sufficiently decreases. Moreover, the viability of hydrogen production hinges upon a 36% reduction in its cost or a 90% decrease in energy operating costs. The outcomes of this investigation furnish compelling proof regarding the influence of parameter uncertainties on both optimal system design and performance. They also showcase the efficacy of the proposed framework for selecting waste-to-energy technologies, and highlight the circumstances that prompt a change in the optimal technology mix. [ABSTRACT FROM AUTHOR]

• Innovative approach to achieve high-energy performance in retail and greenhouses. • Design optimization shows 49% improvement over the code compliant base design. • Heat sharing between individual buildings achieves further 21% site energy reduction. • Net-zero energy design has been achieved by on-site solar PV arrays. • Prototypical template for carbon neutral urban centric infrastructure is explored. Devising methods to recover waste heat and to share it within a neighborhood can lower the energy footprint of this neighborhood and reduce its dependence on the utility grids. This paper presents a novel methodology for capturing waste energy from individual buildings and sharing the recovered energy with an entire neighborhood. A survey of the current state of research on energy sharing is presented. A mixed-use neighborhood consisting of retail, residential, and greenhouse buildings is modeled to develop a holistic design of energy sharing strategy. Neighborhood-level waste heat recovery and distribution network is modeled in the EnergyPlus-DesignBuilder co-simulation platform. The energy sharing methodology is applied to different neighborhood configurations and neighborhood densities. The results show that with the application of energy sharing methodology integrated with energy efficient design and on-site solar energy, a net reduction of 74% energy in the mixed-use neighborhood is achieved compared to a design complying with the minimum requirement of the applicable energy codes. Similarly, a net 90.46% reduction in greenhouse gas (GHG) emissions is realized by energy sharing and on-site carbon capturing using neighborhood greenhouse. [ABSTRACT FROM AUTHOR]

In this paper, four energy control strategies are proposed and analyzed for the standalone Renewable/Fuel Cell Hybrid Power Source (RES/FC HPS). The concept of the load following (LF) and Maximum Efficiency Point Tracking (MEPT) is used to control the fueling rates. A standalone RES/FC HPS uses at least one Renewable Energy Sources (RES) and a Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) as backup source. Photovoltaic (PV) array and wind turbines (WT) farm are used as RES and the surplus of energy during light load stages is stored in hydrogen tank via water electrolysis to fuel the PEMFC. Small-scale RESs and commercially available PEMFCs are interfaced to the common DC bus via power converters and then to the single-phase distribution grid through a voltage source inverter. RES/FC HPS seem to be an efficient alternative for supplying smart houses and isolated sites. This paper proposes a new supervision strategy of the Energy Management Unit (EMU) based on the LF control approach that assures a charge-sustaining (CS) mode for the Energy Storage System (ESS). So, the capacity of the batteries stack can be reduced at minimum if it is directly connected to the DC bus. The ultracapacitors stack compensates dynamically the power flow balance on the DC bus, regulating the DC voltage via a bidirectional buck-boost power converter. Thus, a semi-active hybrid topology is adopted for the ESS having the batteries stack. The MEPT loops ensure an optimized energy management of the RES/FC HPS. The LF strategy designed based on the power flow balance guarantees the load demand through the efficient management of the power flow from RES, FC and ESS, adapting FC energy production to load profile. The FC energy production is controlled via the fueling rates (one is controlled in the LF loop and the other is controlled in the MEPT loop) to maximize the energy consumption indicator: the ratio of the produced energy and the fuel consumed by the FC system during a load cycle. Thus, this paper evaluates the control performances of the four control topologies to fuel the FC stack during an variable RES and load profile. The MATLAB-Simulink® software package is used to model the RES/FC HPS and develop the four EMU strategies. Simulation results shown comparatively the performance of the EMU strategies proposed under different scenarios of RES power generation and load demand. [ABSTRACT FROM AUTHOR]

This paper examines both the potential of and barriers to grid-scale energy storage playing a substantive role in transitioning to an efficient, reliable and cost-effective power system with a high penetration of renewable energy sources. Grid-scale storage is a term that describes a number of different technologies with a wide range of characteristics. This versatility leads to the use of storage to perform a number of grid-services. We first enumerate these services, with an emphasize on those that are best suited to mitigate the effects of uncertainty and variability associated with intermittent, non-dispatchable renewable energy sources. We then provide an overview of the current methods to evaluate grid-integrated storage, summarize key findings, and highlight ongoing challenges to large-scale adoption of grid-scale energy storage. We focus on one particular area that is critical to both the efficient use of energy storage in the power grid and its long-term economic viability: the conflict between the technical benefits of this resource, which can provide both power and energy related grid-services (in some cases simultaneously), and the economic challenges of compensating these services within the current market structures. We then examine recent progress in addressing these issues through regulatory changes and other initiatives designed to mitigate previous market failures. This discussion is followed by some remarks about ongoing regulatory and market design challenges. The paper closes with a summary of the ideas presented and a discussion of critical research needs. [ABSTRACT FROM AUTHOR]

In the paper the method for energy and ecological evaluation of refrigeration system based on the adsorption machine is presented. The energy effectiveness is calculated on the level of the primary energy consumption. The method for ecological evaluation is also discussed. In the ecological evaluation the influence on greenhouse gasses (GHG) is taken into account and the ecological effects are expressed as equivalent CO 2 emission. The authors compare the effectiveness of a refrigerator existing in an example Polish food factory supplied with heat from a boiler house fired with natural gas, a cogeneration system and solar collectors. In the last case the climatic conditions and detailed solar radiation data for Poland have been used. The authors demonstrated that the application of cogeneration or renewable energy sources (RES) for the cooling system can lead to energy savings and ecological benefits. To measure the energy effects the authors introduced the following indices: (PES) – Primary Energy Savings and (GHGS) – Greenhouse Gasses Savings. The results of the mentioned indices for different configuration of heating systems are calculated and presented in the paper. [ABSTRACT FROM AUTHOR]

Renewable energy (RE) penetration growth without energy storage system (ESS) is restricted due to its poor dispatchability. Compressed air energy storage system (CAES) is one of the promising ESS technologies. But, low energy density and high mechanical inertia confined its application as a bulk ESS. In this paper, a novel hybrid thermal-compressed supercritical carbon dioxide energy storage (T-CCES) system is proposed to address CAES shortcomings. In this system, a stratified water thermal energy storage (TES) is employed to store both released heat of compression process and high-frequency reluctant power of a wind farm (which cannot be followed by CCES) using electrical heaters. A dynamic simulation is performed to evaluate system characteristics in steady wind generation condition and in a real wind generation condition. Stochastic simulation of the proposed system integrated with a real wind farm is also fulfilled to assess its characteristics and performance by considering uncertainties using sparse polynomial chaos expansion. Additionally, global sensitivity analysis via Sobol’ indices is conducted to identify the most important parameters of the system. Results show that the system can store wind power during off-peak hours and smoothly releases it into the grid with 57.55% round-trip efficiency (RTE) and 84.1 kWh/m 3 energy density. Uncertainty quantification results indicate that the system can properly work under uncertainties with standard deviation of 55.72–58.16% RTE and 83.7–86.5 kWh/m 3 energy density. Moreover, results show that the random production of wind turbine has a negligible effect on performance characteristics of the T-CCES which makes it a promising solution for integration with wind farms. [ABSTRACT FROM AUTHOR]

In the present paper, a novel method is proposed to enhance the power production and resolve the inconsistent electricity generation of solar chimney power plants (SCPPs) during nighttime. For this purpose, an integrated renewable cycle is proposed by incorporating two technologies: solar chimney and waste-to-energy. The combination is performed by exploiting the warm air of the condensers outlet into the SCPP. The waste-to-energy (WTE) plant in Tehran is thermodynamically analyzed and the mass flow rate of the condensers cooling air is found. Results indicate that by decreasing the humidity of the municipal solid waste (MSW) from 40% to 30% or by increasing MSW feeding rate (0.934–1.146 kg/s), the mass flow rate of the condenser cooling air increases from 190.3 kg/s to 233.7 kg/s. In addition, by increasing the feeding rate or by decreasing the humidity of MSW in the mentioned range, net power output of the WTE plant increases from 1350 kW to 1650 kW. The best injection method is proposed for the warm air of the condensers outlet into the SCPP. Subsequently, the average power increase is examined in different months and parametric study is performed to assess the influence of the effective WTE parameters and meteorological variables on the power output of the SCPP. The final power of the SCPP reaches 20–70 kW (even at the hottest night of the year with 5% relative humidity) and increases 20–1200% and 65–94% (monthly average) compared to the case of without injection. Results demonstrate that in the integrated system, by a 22% increase in the MSW feeding rate (from 0.934 kg/s to 1.146 kg/s) or by decreasing the MSW moisture content (from 40% to 30%), power output of the WTE plant and SCPP increases by 22% and 7%, respectively. Additionally, relative humidity of the surrounding air can increase the SCPP power production by 25%. In addition, the results indicate that wind speeds higher than 12.5 m/s will not affect power production of the SCPP, while relative humidity of the surrounding air, ambient temperature, the MSW feeding rate, and humidity of the MSW have considerable effects on the SCPP power production. In average, total energy and useful exergy efficiency of the proposed system is increased by 0.15% and 0.12% compared to the standalone WTE plant during nighttime. The integration of SCPP with the WTE plant is an applicable method to enhance the power generation and overcome the inconsistent power production of SCPP during nighttime. [ABSTRACT FROM AUTHOR]

Ground source heat pump systems that are installed in areas with heating or cooling dominant seasons, or in buildings with utilization characteristics that lead to a disparity in demand, often encounter challenges related to ground thermal imbalance. This imbalance can lead to long-term ground temperature changes and may cause premature system failure. This paper focuses on combining a ground source heat pump system with a solar thermal array, with the goal of eliminating the effect of ground thermal imbalance, and minimizing system lifetime cost. A thermal mass ground heat transfer model is combined with a time-stepping model to analyze the system for a variety of solar array sizes. The details associated with this modelling technique are presented, and case studies are provided to illustrate the results of the calculations for three different buildings. It is shown that increasing the solar array size can offset ground thermal imbalances, but increasing the array size also results in a larger initial system cost. An economic analysis is then carried out to determine the system lifetime cost as a function of this solar array size, and an optimal array size from an economic perspective was found. The result of the study shows that hybridizing a ground source heat pump system with a solar array produces a viable system from a technical and economic standpoint, can be used to avoid premature system failure, and can reduce system lifetime cost. [ABSTRACT FROM AUTHOR]

The need of a more persistent human presence on sea is driving the development of increasingly more efficient Autonomous Underwater Vehicles. A particularly promising solution to power these vehicles is the retrieval of energy from the ocean temperature gradient. This paper investigates the use of thermoelectric generators (TEGs) for that purpose, by presenting a complete model of thermoelectric generators embedded in the hull of an underwater glider. The model includes not only the thermoelectric generators but also the heat transfer process and the behaviour of different heat storage materials. Several simulations are performed, for each storage material, to determine the adequate design parameters leading to sufficient energy generation for a thermal glider. It is shown that the use of Phase Change Materials (PCM) as an energy storage material is highly advantageous over the use of sea water or stainless steel. Furthermore, it is shown that this approach, although leading to a high number of TEGs and mass of PCM, is compatible with current existing glider dimensions. [ABSTRACT FROM AUTHOR]

In the present paper, an attempt has been made to investigate the theoretical and practical performances of the photovoltaic/thermal (PV/T) system coupled with earth water heat exchanger (EWHE) cooling system for the conditions of semi-arid region of Pilani, Rajasthan. The experimental studies have been performed for different flow rates of cooling water (0.033 kg/s, 0.025 kg/s and 0.017 kg/s) for a typical day climatic conditions. An electrical efficiency comparison was made for two scenarios when the PV panel was connected or disconnected with the thermal collector and found out that the average electrical efficiency of PV/T panels is higher than the normal PV efficiency. The results of the experimental study showed that the maximum PV panel temperature goes up to 73 °C without any cooling. On the other hand, the PV panel temperature drops in the range of 43.68–49.64 °C with the flow rate of 0.033 kg/s. It has been estimated that the electrical and thermal efficiencies of the PV/T system with cooling are in the range of 8.26–8.52% and 44.06–55.45% respectively for flow rate of 0.033 kg/s. The EWHE pipe length of 38 m found to be sufficient for the proposed system. The experimental results are validated with the theoretical model by using basic energy balance equations and found in good agreement with percentage error of 0.91–12.09%. [ABSTRACT FROM AUTHOR]

This paper gives a review of the most important backgrounds and trends of the present energy supply system in the Netherlands. Options are discussed for the integration of renewable energy and the present policies are reviewed that stimulate the energy transition. Last, the role of smart energy management as part of the integration of renewable energy into existing infrastructures is discussed. [ABSTRACT FROM AUTHOR]

• Hydrogen storage systems enable flexible energy conversion and scheduling. • Hydrogen storage cost accounts for the largest proportion of system cost. • The hydrogen energy storage system has less demand for energy storage space. With global energy consumption increasing year by year, the industrial sectors of the world's countries have never been more urgent in achieving carbon reduction. Renewable energy plays a crucial role in the industrial decarbonization process. As the most mature renewable energy technology, wind and photovoltaic power generation have made significant progress in recent years. However, the intermittent characteristics hinder the efficient use of renewable energy. Existing research provides sufficient support for the flexible scheduling of large-scale renewable energy. Hence, this paper proposes a combined energy system composed of wind power-photovoltaic-energy storage salt cavern with hydrogen as the energy scheduling carrier. The system mainly realizes energy conversion through electrolytic water equipment and fuel cells. Then, Qianjiang City, Hubei Province, is taken as the analysis object, and the working conditions of each component in the system are optimized with the help of an improved particle swarm optimization algorithm. According to the results, the system's contribution to the energy system is discussed, and the system's economy and carbon reduction effect is studied. The analysis proves that the improved particle swarm optimization algorithm has a stronger solving ability. The combined energy system can effectively improve the economy and renewable energy utilization rate, meet the regional electricity demand, and significantly reduce carbon emissions. The economic analysis of the system shows that the operation and maintenance cost of hydrogen storage salt caverns accounts for the largest proportion of the total cost, about 60 %. Compared with several existing large-scale energy storage technologies, it is found that the energy efficiency of the whole system is only about 40 % due to the limitation of technology maturity. Nevertheless, the flexibility of the hydrogen storage system layout is relatively high. The required underground space volume is only equivalent to 1/6 and 1/2 of pumped storage and compressed air storage with the same scheduling capacity. The system will provide a theoretical support for the optimization of energy pattern and layout. [ABSTRACT FROM AUTHOR]

• The paper offers a global analysis of complementarity between wind and solar energy. • Solar-wind complementarity is mapped for land between latitudes 66° S and 66° N. • Complementarity is examined regarding PV panel inclination and storage capacity. The concept of renewable energy sources complementarity has attracted the attention of researchers across the globe over recent years. Studies have been published regularly with focuses on aspects such as new metrics for complementarity assessment, the optimal operation of hybrid power systems based on variable renewables, or mapping resources complementarity in a specific region. This study targets the present literature gap, namely a lack of complementarity study covering explicitly the whole World, based on the same data source and methodology. The research employs Kendall's Tau correlation as the complementarity metric between global solar and wind resources and a pair of indicators such as the solar share and a sizing coefficient usually applied in the domain of hybrid generators. This method allows to conduct a preliminary estimation of a solar and wind energy hybrid generator based on a daily demand of 1 kWh. The data series employed in this study come from NASA's POWER Project Program, covering the years 2001–2020. This work provides an interesting insight into the global variability of the complementarity between these two variable energy sources. Significant findings of this paper include that Kendall's Tau ranges between –0.75 and 0.75, in line with previous research for specific regions, thus providing a theoretical maximum for planning. Additionally, the results suggest that in most tropical and subtropical areas, the hybrid solar-wind generator should be dominated by the solar portion to minimize the variability of the total daily energy produced. [ABSTRACT FROM AUTHOR]

Exploiting renewable energy is a critical greenhouse gases reduction strategy for China, especially in areas where new power plants are needed. Challenges in energy storage, however, always complicate the design of renewable energy-dominated power generation systems. This study attempt to provide a solution to the energy storage problem through the synergy of both the power supply and demand sides. Based on local natural energy resources endowments, this paper applies the hybrid optimization model for multiple energy resources and load types to analyse the feasibility of satisfying energy demand. To verify the model’s technological and economic feasibility, this research applies its synergy model to a 2.8 km 2 isolated island in the South China Sea. The simulation results demonstrate that the cost of energy and net present cost of the power supply system are $0.212/kW h and $127 M when hydrogen energy storage equipment is used, and $0.178/kW h and $101 M when traditional-battery energy storage equipment is utilized. This study also reveals that using flywheels to supplement the hydrogen and traditional-battery energy storage equipment could reduce the cost of energy by 5.6% and 3.4%, respectively. In addition, power system demand-side management can further reduce the cost of energy by approximately 20% for all technology scenarios considered in this study. A carbon emissions analysis demonstrates that the carbon reduction rates of the proposed power systems are between 87.7% and 95.1% compared with a fossil-energy based power system. In brief, this study indicates that solar and wind energy combined with appropriate energy storage equipment can meet the energy demand of the island. [ABSTRACT FROM AUTHOR]

Wind energy becomes more powerful and consistent with an increase in altitude, therefore, harvesting the wind energy at high altitude results in a naturally restocked source of energy which is cheaper and far more efficient than the conventional wind power system. Airborne wind turbine (AWT), one of the many techniques being employed for this purpose, stands out due to its uninterrupted scheme of energy production. This paper presents the aerodynamic performance of AWT system with NREL Phase IV rotor at an altitude of 400 m. Unsteady simulation of the airborne system has been carried out and variations in the rotor’s torque for a complete revolution are reported and discussed. In order to compare the performance of the shell mounted configuration of Phase IV rotor with its standard test configuration, steady state simulations of the rotor are also conducted under various wind conditions for both configurations. Finally, for stable design of the buoyant airborne system, aerodynamic forces on the shell body are computed and reported. [ABSTRACT FROM AUTHOR]

This work presents a smart microgrid consisting of diesel, photovoltaic (PV), and battery storage plants. One of the key features of smart grid is to provide a redundant high quality power for the consumers. In islanded microgrid, the under frequency and/or voltage collapse, caused by power deficiency, can lead to power outage. The current practice is to shed the load demand until the frequency and voltage are restored. However, the redundancy in supplying power has no meaning as long as the loads are shed. The main objective of this paper is to propose a power management system (PMS) that protects the microgrid against the load shedding. PMS is able to control the microgrid in both centralized and decentralized fashions. To prevent under frequency load shedding (UFLS), this work proposes using battery energy storage system (BESS) to compensate for the power mismatch in the islanded microgrid. A method is presented to estimate the rate of change of frequency and to calculate the power deficiency. The approximated value is exploited as the set-point to dispatch BESS. PV and battery plants are supposed to share the reactive power demand proportionally and thus regulate the voltage at the load bus. This work also suggests two outer control loops, namely, frequency restoration loop (FRL) and difference angle compensator (DAC). These loops ensure microgrid smooth transition from islanded mode to grid-connected mode. The microgrid is configured to investigate the effective utilization of exiting solar PV plant connected to distribution network in Sabah Malaysia. The microgrid is implemented in PSCAD software and tested under different scenarios. The microgrid with PMS shows operational stability and improvements in comparison with the original system. The results indicate that PMS can effectively control the microgrid in all operating modes. [ABSTRACT FROM AUTHOR]

In an off-grid hybrid wind-diesel-battery system, the diesel generator is often not utilised efficiently, therefore compromising its lifetime. In particular, the general rule of thumb of running the diesel generator at more than 40% of its rated capacity is often unmet. This is due to the variation in power demand and wind speed which needs to be supplied by the diesel generator. In addition, the frequent start-stop of the diesel generator leads to additional mechanical wear and fuel wastage. This research paper proposes a novel control algorithm which optimises the operation of a diesel generator, using genetic algorithm. With a given day-ahead forecast of local renewable energy resource and load demand, it is possible to optimise the operation of a diesel generator, subjected to other pre-defined constraints. Thus, the utilisation of the renewable energy sources to supply electricity can be maximised. Usually, the optimisation studies of a hybrid system are being conducted through simple analytical modelling, coupled with a selected optimisation algorithm to seek the optimised solution. The obtained solution is not verified using a more realistic system model, for instance the physical modelling approach. This often led to the question of the applicability of such optimised operation being used in reality. In order to take a step further, model-based design using Simulink is employed in this research to perform a comparison through a physical modelling approach. The Simulink model has the capability to incorporate the electrical and mechanical (Simscape) physical characteristics into the simulation, which are often neglected by other authors when performing such study. Therefore, hybrid system simulation models are built according to the system proposed in the work. Finally, sensitivity analyses are performed as a mean of testing the designed hybrid system’s robustness against wind and load forecast errors. [ABSTRACT FROM AUTHOR]

Initially pushed by the European Union (EU) through the Europe 2020 strategy, the development of renewable energies is a strategic action aiming to limit climate changes and cut greenhouse gas emissions. National subsidies favored the diffusion of this new kind of energy sources, even if there are interesting economic opportunities also in non-subsidized markets. Renewable energy (RE) is a sustainable choice, but its management requires a proper analysis, both from political and operational levels. The aim of this paper is the assessment of European renewable energy source (RES) trajectory towards 2020, starting from historical values and through common scientific methods. In addition, a new reference framework is proposed, in order to evaluate RESs performances in Europe. The framework is based on three indicators: (i) share of energy from RESs in gross final energy consumption, (ii) REs primary production per capita and (iii) gross final consumption of REs per capita. Results could have practical implications for the decision makers involved in the management of energy sources throughout Europe and could be used for the comparison on a global scale. [ABSTRACT FROM AUTHOR]

A significant amount of global electric power generation is produced from the combustion of fossil fuels. Steam boilers are one of the most important components for steam and electricity production. The objective of this paper is to establish a theoretical framework for the sustainability analysis of a utility boiler. These analyses can be used by decision-makers to diagnose and optimize the sustainability of a utility boiler. Seven utility boiler systems are analyzed using energy and embodied solar energy (emergy) principles in order to evaluate their environmental efficiencies. They include a subcritical coal fired boiler, a supercritical coal fired boiler, an oil fired boiler, a natural gas fired boiler, a concentrating solar power boiler utilizing a tower configuration, a biomass boiler, and a refuse derived fuel boiler. Their relative environmental impacts were compared. The results show that the natural gas boiler has significantly lower CO 2 emission than an equivalent coal or oil fired boiler. The refuse derived fuel boiler has about the same CO 2 emissions as the natural gas boiler. The emergy sustainability index of a utility boiler system is determined as the measure of its sustainability from an environmental perspective. Our analyses results indicate that the natural gas boiler has a relatively high emergy sustainability index compared to other fossil fuel boilers. Converting existing coal boilers to natural gas boilers is a feasible option to achieve better sustainability. The results also show that the biomass boiler has the best emergy sustainability index and it will remain a means to utilize the renewable energy within the Rankine steam cycle. Before solar boiler technology can be widely used in the United States’ utility power industry, its capital cost and the O&M cost should be reduced. Using the results of this research, decision-makers can make better-informed, environmentally-efficient selections of future utility scale boilers. [ABSTRACT FROM AUTHOR]

In this paper, a new agent-based distributed reactive power management scheme is proposed to improve the voltage stability of energy distribution systems with distributed generation units. Three types of agents – distribution system agent, estimator agent, and control agent are developed within the multi-agent framework. The agents simultaneously coordinated their activities through the online information and energy flow. The overall achievement of the proposed scheme depends on the coordination between two tasks – (i) estimation of reactive power using voltage variation formula and (ii) necessary control actions to provide the estimated reactive power to the distribution networks through the distributed static synchronous compensators. A linear quadratic regulator with a proportional integrator is designed for the control agent in order to control the reactive component of the current and the DC voltage of the compensators. The performance of the proposed scheme is tested on a 10-bus power distribution network under various scenarios. The effectiveness is validated by comparing the proposed approach to the conventional proportional integral control approach. It is found that, the agent-based scheme provides excellent robust performance under various operating conditions of the power distribution network. [ABSTRACT FROM AUTHOR]