Renewable Power Sources Research Articles

Day Ahead Solar Generation Forecasting in Smart Grids to Minimize Electricity Bill

Abstract: In order to meet the increasing growth of energy demand, integration of renewable resources into residential applications appears to be a viable solution. In the proposed model,a residential house is considered where the consumer is able to generate his own energy from a microgrid consisting of solar panels and wind turbines. In this study, an optimization method is employed to minimize the overall electricity bill of a residential home over a periodof 24 hours. In smart grids, energy management is imperative in reducing the electricity cost of consumers under a real time pricing approach. Nowadays, learning-based modeling methods are utilized to build a precise forecast model for renewable power sources. In this paper, we propose a long short-term memory (LSTM) recurrent neural network-based framework, which is one of the most popular techniques of deep learning. This technique predicts day ahead solar irradiation and wind speed data. We also consider an energy storage system (ESS) for efficient energy utilization. Optimization is done and from the obtained results a substantial reduction in electricity bill is observed

Ultra‐high gain quadratic boost DC–DC converter based on a three‐winding coupled inductor with reduced voltage stress for fuel cell‐based systems

AbstractHere, an ultra‐high gain quadratic boost DC–DC converter (UQBC) based on the conventional quadratic boost converter (CQBC) and a three‐winding coupled inductor (TWCI) has been proposed. It benefits from an extensive voltage gain range and low voltage stress on semiconductors. In addition, the converter requires a reasonable number of components. This structure is suitable for connecting renewable DC power sources like fuel cells to a DC‐bus in DC microgrids. Unlike CQBC, the produced conversion ratio has been improved to [1+n+m+d(1+n)]/(1−d)2 thanks to integrating a TWCI into CQBC. As a result, the proposed quadratic boost converter gives a better step‐up factor than previously presented quadratic boost converters (QBC). Meanwhile, the employed improvement method has not adversely affected some critical parameters like voltage stress on semiconductors or the input current ripple. This paper presents the mathematical analysis and operating principle of the proposed topology for both continuous and discontinuous current modes (CCM and DCM). Experimental results are represented to validate the converter theory and its performance. Results indicate that a high gain and efficiency have been obtained. Also, the voltage stress on the power switch is reduced by one‐fourth by choosing a proper duty cycle and winding coefficient.

Two-Stage Optimization Scheduling of Virtual Power Plants Considering a User-Virtual Power Plant-Equipment Alliance Game

Distributed renewable energy, loads, and power sources can be aggregated into virtual power plants (VPPs) to participate in energy market transactions and generate additional revenue. In order to better coordinate the transaction relationships among various entities within VPPs, this paper proposes a two-stage optimization model for VPPs that considers the user-VPP-equipment alliance. Firstly, starting from the basic structure of VPP, it is proposed to divide the alliances in VPP into two alliances: demand-side user-VPP and supply-side equipment-VPP. And a VPP optimization framework considering the cooperative game of the user-VPP-equipment alliance has been established. Then, a two-stage optimization model for VPPs was established considering the cooperative game of user-VPP-equipment alliance. The day-ahead optimization model takes economic and social benefits as the dual objectives, and the intraday optimization model aims to minimize the cost of deviation penalties. Secondly, taking into account the risk levels and comprehensive marginal benefits of various entities within the VPP, a profit distribution method combining improved Shapley values and independent risk contribution theory is adopted to allocate the total revenue of the VPP. The case results show that the operating cost has been reduced by 5.75%, the environmental cost has been reduced by 4.46%, and the total profit has increased by 29.52%. The model can improve the overall efficiency of VPPs.

A study on the assessment of renewable energy resources for power generation using the MCDM approach

The development and survival of contemporary economies are fundamentally dependent on energy. Practically every aspect of human well-being depends on it, encompassing "sustainability, employment, connectivity to necessities, and the economy, health care, employment, and education". Energy is regarded as being essential to the economic system and a key factor in a nation's prosperity. Developing markets must diversify their energy sources to ensure energy independence, supply options, employment generation, and sustainable development. A comprehensive energy development strategy is essential to meet supply and demand since population growth and modernization are two major drivers of rising energy needs.“The multicriteria decision making (MCDM) method" is used to decide amongst many renewable power sources when numerous criteria are present. Using the COPRAS rating system, the report examines five alternative energy sources "PV, solar thermal, hydro, wind, and biomass"—against five components. "Solar PV ranks fifth, solar thermal is third, hydro is first, the wind is fourth, and biomass is second" in the COPRAS ranking of alternatives. Hydro recorded the largest significance compared to biomass, trailed by “solar thermal, wind, and solar PV”, as per the COPRAS ranking. "Hydro > Biomass > Solar Thermal > Wind > Solar PV" sums up the order. The most potential renewable source for economic development, according to this, is hydro.

Site Selection for Sustainable Wind-Solar Hybrid Energy Harvesting Plant

The world’s energy landscape is undergoing rapid transformation as societies strive towards renewable and sustainable power sources in response to the need for energy security and climate change. Depletion of fossil fuels and increasing focus on environmental sustainability have been significant drivers in this global shift towards renewables. Among the promising solutions, solar-wind hybrid energy systems have gained attention, capitalizing on the complementary nature of solar and wind resources. However, selecting the optimal site for these hybrid plants is crucial for their successful implementation and efficiency. This research introduces a comprehensive methodology for site selection, seamlessly integrating the Delphi method and Analytic Hierarchy Process (AHP). The Delphi method harnesses expert consensus to distil essential criteria, while AHP offers a structured framework to evaluate and prioritize these criteria. The results showed successful utilization of the AHP and Delphi techniques for evaluating the optimal location selection among different cities for solar-wind hybrid energy harnessing in the northwest region of Pakistan. The key factors for selection of optimal location were identified through expert feedback and analysis. Among the selected key main criteria, resource availability and infrastructure and socio-economic factors emerged as the top-ranked criteria in this study. The results of this study hold significant relevance and should be duly considered for solar-wind power project site selection, while also offering opportunities for further enhancements in the future.

Influence of Hydrogen Electrode Active Layer Thickness on Electrochemical Performance of Solid Oxide Cell Operating in Electrolysis Mode

Reversible solid oxide cell technology (RSOC) is a key technology in future hydrogen energy concept and may play a significant role in stabilizing intermittent renewable electric power sources. This work handles an attempt to optimize the thickness of the hydrogen electrode active layer (HEAL) for solid oxide cells designed and developed initially for fuel cell application (SOFC). Five cells with HEAL thickness of 0, 7, 12, 16 and 20 μm, prepared using industrial manufacturing methods, are analyzed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods under a wide range of operating conditions. Optimal thickness of an active layer studied depends on operating conditions. Depending on the temperature and feed gas water content applied highest performances were achieved for cells with HEAL thicknesses between 7 and 16 μm. At 800 °C and 90% feed gas water content, the best cell had an active layer of 7 μm, drawing −3.5 A cm−2 current at −1.4 V.

Feasibility Study of Theoretical Efficiency Calculation for Flat Plate Collectors in Solar Water Heating Systems

Solar energy stands as a paramount clean, abundant, and renewable power source holding remarkable potential to address our escalating energy needs. Among its crucial utilization methods, solar water heating systems integrating flat plate collectors (FPCs) emerge as vital contributors in harnessing and converting solar energy into utilizable heat. This study delves into the realm of FPCs' theoretical efficiency assessment, employing mathematical models and factoring regional weather conditions to meticulously evaluate the efficiency of single-glaze and double-glaze collector variants. The outcomes spotlight the single glaze collector's efficiency at 0.669 and the double glaze collector at 0.713, underscoring the discernible performance gap. In a landscape where industries, hospitals, residences in Kandahar, and comparable settings extensively depend on hot water, often derived from fossil fuel-driven heating, this research's implications hold particular relevance. By transitioning towards solar water heating, this study not only underscores a concrete method to curtail carbon emissions but also to significantly reduce energy expenses linked with conventional heating techniques. The findings beckon a departure from the status quo, emphasizing that cleaner energy options are attainable, even for regions demanding hot water requirements. As society navigates complex decisions concerning energy sourcing, embracing solar water heating stands as an auspicious stride towards a sustainable future, beckoning us to collectively embark on a path of energy-conscious choices for the greater good of our planet and the generations that will inhabit it.

Model of Hydrogen Production by Combination of Water Electrolysis and Unstable Sources of Energy

Water electrolysis is accepted as direct method for hydrogen production from water. The emission pathway of hydrogen is related to the source of electric energy and process of water electrolysis just define energy efficiency or amount of hydrogen produced from energy supplied. For green hydrogen production almost exclusively, renewable energy sources are necessary. But unstable production is typical for most frequently mentioned wind and solar power station. Currently four types of water electrolyzers are available: Proton exchange membrane water electrolysis (PEMWE), Alkaline water electrolysis (AWE), Membrane alkaline water electrolysis (MAWE) and high temperature solid oxide water electrolysis (SOWE). Each of mentioned type exhibits different properties and requirements if operated in combination with renewable power sources. Proper selection of electrolyzer type and its size is crucial for economic production of hydrogen.PEMWE shows higher flexibility in operation changes. Its warming up to operating temperature is only few minutes or seconds due to the high current densities, thin ion conductive membrane and circulation only of demineralized water. Its production range is limited by hydrogen permeation through membrane at low production and electrolyzer stability at high production. The production range starts usually from 5% and finish at short term 120% of designed capacity.AWE represents oldest technology with high durability proved by large number of installations. But old electrolysers were designed for continual operation with limited possibility to moderate its production. Newly developed units are better adapted to intermittent operation. Parasitic currents in electrolyte distribution channels are main reason for efficiency decrease at low loading. Their minimum operation range varies from 1% up to 30% depending of manufacturer and size. Despite it, the request for circulation of concentrated hydroxide and low conductivity of separator make warm up period significantly slower with low efficiency. Therefore, frequent phase off and on affect the total amount of produced hydrogen.MAWE is newest electrolyzer type. It combines the concept of ion selective membrane usage as separator and alkaline environment to avoid platinum metals need. Thanks to the ion-selective membrane the startup dynamics is faster but durability of membrane limits its operation temperature.SOWE as process with operating temperature 800 °C is not suitable for irregular operation. But it high efficiency make this process interesting for combination of power sources to keep permanent run. Nuclear and renewable power sources are one of possible combination.Mathematical model capable to calculate actual and integral production of hydrogen on the base of known power sources production and elektrolyzer parameters was created. Input data of elektrolyzer behavior for the model come from an in-house measurement and from literature. Various data of for unstable power sources involve a photovoltaic power-plant and train recuperation energy from braking on the 15 min interval were taken.Created model indicates production capacity of given combination and also the running time and amount of utilized energy. With consideration of investment cost i tis able to estimate most suitable sizes.Acknowledgment:This project is financed by the Technology Agency of the Czech Republic under grant TO01000324, in the frame of the KAPPA programme, with funding from EEA Grants and Norway Grants.

A Bottom-up Transient Theory for Concentration Polarization with Applicability to over-Limiting Current Conditions

Renewable power sources have drawn interest due to scarcity of fossil fuels and associated pollution during their combustion-based power production. Renewables are projected to produce approximately 60% of US electricity generation by 2050, with an expected contribution of 2000 TW-h from wind power alone. To overcome the mismatch between electricity demand and intermittent supply, such power plants require large-scale energy-storage device integrated with them. In contrast to other technologies, redox flow batteries (RFBs) offer independently scalable power and energy capacity that is demanded for such applications. Despite significant achievement in their designs through experimentation and modeling, limited understanding has been established to date concerning their transient response while operating under irregular charge/discharge scenarios in renewable-powered grids and micro-grids. Under such conditions pore-scale mass transport physics and different mechanisms of concentration polarization can occur, but the conventional film law of mass transfer (FLoMT) using a constant Sherwood number cannot capture time-varying diffusion layer thickness near electrode surfaces. Further, the mean solute advection rate through porous RFB electrodes can deviate from the value expected from product of superficial velocity and average concentration inside the electrode if pore-scale concentration polarization is substantial. Consideration of these effects in the present bottom-up theory makes it applicable to over-limiting conditions, while predicting concentration polarization in agreement with experimental observations. We accomplish this by creating theory with similarity to the theory of Ralph White and co-workers for solid-state, particle-scale diffusion in Li-ion batteries [J. Power Sources, 2012, Vols. 214 and 218], while our theory is instead applied to an arbitrary representative volume element of flowing liquid electrolyte inside electrode pores.Here, we present a theory to incorporate these transient effects into a bottom-up transient model (B-UTM) by using frequency-dependent transfer functions (TFs) that are derived from the Fourier transformed pore-scale mass conservation equations (MCEs). These TFs preserve pore-scale mass transfer physics during their embedding into an up-scaled model. One of these TFs is the spectral Sherwood number that extends the film law of mass transfer to transient conditions and that correlates reactive flux with concentration polarization through an output-input relationship in the frequency domain. Another TF named the advective-flux transfer function captures the acceleration/suppression of solute advection rate that arises from the inhomogeneity in pore-scale concentration distributions. We first present validation of this theory using transient RFB experiments where the introduced B-UTM predicts the time evolution of concentration polarization in good agreement. Meanwhile the conventional FLoMT model that uses time-independent Sherwood number and neglects the solute acceleration/suppression effect shows systematically larger polarization (up to 400%), which restricts such models from simulating charging/discharging with applied current near and above the limiting current.The utility of the introduced bottom-up theory is demonstrated by incorporating it into a multi-scale RFB model in which redox-active electrolyte flows through a porous electrode comprised of an array of circular cylinders in crossflow that mimics commonly used carbon felt. The frequency dependence of the introduced TFs obtained from numerical solution of pore-scale MCEs are analyzed for different electrode porosity and Péclet number, where both the TFs reach a non-zero finite value in the limit of vanishing frequency. The non-zero value of the spectral Sherwood number in this limit is identical to the Sherwood number obtained in the pseudo-steady limit (PSL) where transient effects are negligible. With increasing frequency both the TFs show a transition from lagless response to semi-infinite Warburg response with orders higher values compared to that of the PSL. Finally, these TFs are embedded into an up-scaled model to obtain the time-domain response of RFBs operating under a step impulse applied current with different step durations. Numerically obtained concentration polarization and the average reactant concentration inside electrodes is used to construct non-dimensional regime maps showing a regime of over-limiting current. The results show that fast current fluctuations are sustained even when current exceeds the limiting current, which provides a means to increase the utilization of charge capacity of existing flow-based electrochemical devices that are operated under transient conditions. The theory introduced here can find applicability in other flow-based electrochemical devices including electrochemical separations and CO2 capture. Figure 1

Development of a Self-Powered Microneedle Based Wearable Electrochemical Sensor for Glucose Monitoring

Diabetes is increasingly being recognized as a worldwide public health concern owing to the affected rate of the patients in the past years. One of the major barriers to the disease control is the lack of sensitive and reliable point-of-care device that can provide quantitative diagnosis and monitoring. The wearable sensing technology has the potential of revolutionizing the precision medicine and personalized healthcare system. Within the emerging class of wearables, the microneedle-based sensors play a key role in combining the advantages of monitoring the analytes in interstitial fluid (ISF) and minimally invasive skin pricking. However, such devices require appropriate power sources to realize their full capacity, and the increasing power costs, global warming, and environmental pollution are certain aspects that needs to be pondered upon. Researches are dedicated on power generators with focus on wearable energy harvesters to address the issue of power supply. Thermoelectric generators (TEGs) have the ability to generate power by transforming thermal energy to electrical power output. Herein, we have developed a microneedle based enzymatic, electrochemical glucose sensing system powered by TEG utilizing the body heat. 1 mm stainless steel microneedles were sputtered with gold and platinum, and further coated with graphene paste, glucose oxidase, poly-hydroxyethyl methacrylate, and nafion. The fabricated device exhibited a good sensitivity, and a wide linear range. According to the World Health Organization (WHO), the normal glucose level in human body are between 4.0 mM to 5.6 mM, and our device has shown a concentration dependent output current signal from 4.0 mM to 24.0 mM. The device has also exhibited excellent detection results in real-sample (artificial ISF) in vitro study as well as in vivo analysis performed in 12 – 15 weeks SD rats. The device is completely self-powered where the TEG derives power from the temperature gradient between the body heat and the exposed environment. The novelty of this work lies in integrating the microneedle-based sensing device with the TEG as the power source. The results indicate a promising self-powered sensor with the renewable and sustainable source of power ensuring continuous operation.

Faraday Efficiency Study of Pressurized Alkaline Water Electrolyzer

According to a BloombergNEF report, China is the largest green hydrogen market, accounting for about 60% of the expected global electrolysis volume in 2022-2023. More than 90% of these electrolyzers are pressurized alkaline water electrolyzers (AWE), like the classic design of Lurgi. AWE manufacturers and end-users place great emphasis on advanced electrodes and membranes to improve power efficiency, and often using 100% Faraday efficiency to calculate current density-based yields.As an end-user, the authors investigated a combination of real AWE operating data and electrochemical engineering principles and discovered that Faraday efficiencies were around 85-93%. Therefore, Aspen ACM simulation models were developed based on detailed internal structures and configurations that well corresponded with plant data, suggesting that many AWE manufacturers exaggerate Faradic efficiencies by to 10%.Some low-cost design improvements are proposed for the bipolar plate and manifold alkali channels, which can improve the Faradaic efficiency by 5-7%, producing higher power efficiency especially when connected to a renewable power source at low loads.

Integration of Reversible Solid Oxide Electrolysis (rSOC) to Wastewater Treatment Plants for Sustainable Green Gas Production and Balancing of Green Power

Biogas produced from anaerobic digestion (AD) of sewage sludge and organic wastes at wastewater treatment plants (WWTPs) can present an important energy contribution to a sustainable society. This raw biogas contains typically 50-65 molar% methane (CH4) and 50-35 molar% carbon dioxide (CO2). The raw AD biogas can be further upgraded to biomethane (with over 98 molar% CH4). This is a sustainably produced gas of biological origin which has same usability and energetic properties as fossil natural gas. Either by use as biofuel in transportation, local combined heat and power (CHP) or directly fed into the gas grid, biomethane has become a vital non-fossil energy source in Europe but also other parts of the world.During the CO2 separation step of biomethane upgrading, substantial amounts of CO2 are emitted to the atmosphere. A methanation unit can convert this CO2 into sustainable Synthetic Natural Gas (SNG), with a strong potential to be used as additional biomethane (SNG-Biomethane). The methanation unit can replace the conventional carbon dioxide (CO2) separation unit for biomethane upgrading, but needs addition of hydrogen from water electrolysis, e.g. high performance Solid Oxide Electrolysis (SOE). Such SOE can also be built as a novel high-performance reversible Solid Oxide Electrolysis (rSOC), as demonstrated in the European H2020 project BALANCE. Besides the SOE mode, such rSOC can operate also in the opposite fuel cell direction (SOFC): In times when power demands exceed sustainable supply, the SOFC mode of the rSOC can convert raw AD biogas directly to electricity. In this way, WWTPs can act as energy storage solutions to buffer temporal electrical energy surplus and produce domestic sustainable SNG to the transport sector or the gas grid. At the same time, the rSOC provides a concept of zero-emission power production. To highlight the zero-emission potential of the rSOC, this paper emphasizes author’s earlier results from the European H2020 project DEMOSOFC, which demonstrated zero-local emission SOFC using raw biogas from WWTP sewage sludge and organic wastes.In this paper, profitability estimations for optimal rSOC and methanation investment and operation strategies at a modern city level WWTP in Finland, Europe, are presented. Power used in rSOC electrolysis mode (SOEC) origins from intermittent green power sources such as wind power, while power produced in rSOC fuel cell mode (SOFC) uses raw AD biogas. For the assessment, we utilize a dedicated Power-to-X optimization model which combines optimally power market operations, dimensions of renewable power sources, plant dimensions and operational scheduling strategies. The assessment showed high profitability using European gas crisis power market data 2021-2022, resulting in sustainable biomethane net production costs of 30-70 €/MWh.

(Best Student Presentation) Extending the NaCl-AlCl3 Phase Diagram to Enable Low-Cost, Long-Duration Na-Al Batteries for the Grid

Achieving deep grid decarbonization via intermittent renewable power sources requires extensive grid-scale energy storage technologies to deliver stable power during periods of low generation. Doing so at scale and at low cost further adds to this challenge, as current solutions generally rely on geographically limited solutions such as pumped hydro storage, or costly battery chemistries focusing primarily on Li-ion technologies. As an alternative, battery systems based on lower cost materials such as sodium offer an attractive alternative for low-cost, scalable, and non-geographically limited electrochemical energy storage.This work combines an abundant and inexpensive molten sodium metal anode with a cost-effective aluminum cathode to provide a proof-of-concept alternative for grid-scale energy storage. Building on prior work utilizing the high reversibility of the neutral sodium chloroaluminate (NaAlCl4) molten salt electrolyte commonly used for classic molten sodium batteries, this work demonstrates greater capacity utilization of the NaCl-AlCl3 binary system by ‘overcharging’ this Na-Al battery to form an acidic chloroaluminate catholyte, NaAl2Cl7. Leveraging the reaction between NaAlCl4 and NaAl2Cl7 in conjunction with that between Al/NaCl and NaAlCl4 advantageously utilizes the majority of Na available in the cathode for capacity, in addition to providing a higher discharge voltage (~ 2 V compared to ~ 1.6 V for the NaAlCl4 reaction), thereby adding ~ 119 Wh kg-1 additional specific energy, on top of the 493 Wh kg-1 theoretical specific energy of the neutral Na-Al battery reaction between Al/NaCl and NaAlCl4.Fundamental aspects of the acidic chloroaluminate reaction are investigated, showing that cells using only the acidic reaction are able to cycle for hundreds of cycles. The acidic reaction between NaAlCl4 and NaAl2Cl7 occurs via a solution-phase reaction, unlike the two-phase neutral reaction between NaCl/Al and NaAlCl4, and we confirm via Raman and NMR spectroscopies that complete conversion to NaAl2Cl7 occurs at end of charge. Na-Al batteries utilizing both reactions demonstrate high areal capacity (~ 46 mAh cm-2) and excellent reversibility. Enabled by the rapid mass transfer and solid-liquid reaction mechanism of the chloroaluminate catholyte, a higher areal capacity cell with ~ 132 mAh cm-2 is demonstrated, allowing a discharge duration of 28.2 h, implying that this Na-Al battery chemistry may be suitable for long-duration energy storage for grid applications. Finally, the raw active materials cost of this battery is estimated to be only ~ $7 kWh-1, which is promising for enabling low-cost renewable power utilization for the grid. Figure 1

Non-Nucleophilic Electrolytes with Non-Fluorinated Hybrid Solvents for Long-Life Magnesium Metal Batteries

Growing energy demands and the widespread of renewable power sources call for high-energy storage systems beyond lithium-ion batteries (LIBs). Rechargeable magnesium batteries (RMBs) are high-energy, safer, and more cost-effective alternatives to LIBs and lithium metal batteries (LMBs) thanks to Mg’s high volumetric capacity (3832 mAh cm-3)1, low theoretical potential (-2.37 V vs SHE)2 and earth-abundance3. Non-nucleophilic and non-fluorinated compounds are the most important class of materials to enable sustainable rechargeable magnesium (Mg) batteries, however, they suffer from poor stability due to the formation of unstable solid-electrolyte-interphase (SEI).4 Here, we design a hybrid-solvent electrolyte by dispersing a non-nucleophilic solution in a non-fluorinated weakly-coordinating solvent to prevent parasitic reactions and form stable SEI. This strategy significantly improved the cycle life of the Mg anode from 24 to 4000 hours (in Mg-Mg symmetric cells) and realized a stable cycle life of Mg-Mo6S8 full cells for more than 2300 hours with an average CE of 99.96%. The non-fluorinated weakly-coordinating solvent suppressed uneven Mg growth and contributed to the formation of polymeric SEI, which filled the cracks of pristine SEI, preventing side reactions and passivation. This strategy revealed the critical role of weakly-coordinating solvents in stabilizing Mg anode for reversible Mg batteries.

Techno-economic evaluation of the electrochemical production of renewable ethylene oxide from fluctuating power sources and CO2

We present a techno-economic assessment of a novel ethylene oxide (EO) production process, which converts carbon dioxide (CO2) and water electrocatalytically to ethylene (C2H4) and hydrogen peroxide (H2O2), which are further synthesized into EO. To ensure environmental sustainability, the primary focus was on available CO2 from biogenic sources (biomethane and bioethanol plants) and renewable power sources (wind and photovoltaics) for decentralized applications. Accordingly, data on existing European CO2 and renewable power sources were compiled for spatial analysis to develop technology roll-out and exploitation scenarios: 175 suitable locations were identified. Focusing on three locations, the production costs of EO and the product mix were calculated, considering various energy sources and plant configurations (as of 2030 and 2040). For a generic scenario, considering CO2 to be available free of cost (existing biomethane upgrading) and electricity cost of 36€/MWh, the production cost of the product mix (EO, H2O2, methane, hydrogen) amount to 0.86 €/kg. This is at a similar order of magnitude as assessments on other Power-to-X value chains. Assuming that EO is the only utilizable product, the costs increase to 5.78 €/kg, which is significantly higher than for fossil alternatives. According to the sensitivity analysis, energy efficiency, electricity prices, and capital expenditure are the most relevant factors. Regarding the latter, an extended plant lifetime is a crucial factor.

A New Soft Computing Fuzzy Logic Frequency Regulation Scheme for Two Area Hybrid Power Systems

Modern renewable energy power system designs provide significant application benefits, but they also produce losses. The total generation, total load demand, and system losses must be balanced in order for this structured power system to operate reliably. The actual and reactive power balances are disturbed as a result of changes in load demand. System frequency and tie line interchange power deviate from their planned values as a result of this. A high system frequency deviation can cause the system to crash. In that case, multiple connect area systems use intelligent load frequency control techniques to deliver dependable and high-quality frequency and tie line power flow. Here, a standalone hybrid power system is taken into consideration, with generated power and frequency being controlled intelligently. In addition to the unpredictable nature of the wind, frequent adjustments in the load profile can produce sizeable and detrimental power variations. The output power of such renewable sources may fluctuate to the point that it causes significant frequency and voltage changes in the grid. An intelligent approach recently proposed to address the load frequency control (LFC) issue of an interconnected power system is known as fuzzy logic PID controller (FLPIDC). Standard proportional integral derivative (PID) controllers are used to control each section of the system.

The Impact of Phase-Locked Loop (PLL) Architecture on Sub-Synchronous Control Interactions (SSCI) for Direct-Driven Permanent Magnet Synchronous Generator (PMSG)-Based Type 4 Wind Farms

Electric vehicles (EVs) are a promising solution to reduce carbon dioxide (CO2) emissions, but this reduction depends on the fraction of renewable sources used to generate electricity. Wind energy is thus a vital candidate and has experienced a remarkable surge recently, establishing itself as a leading renewable power source worldwide. The research on Direct-Driven Permanent Magnet Synchronous Generator (PMSG)-based type 4 wind farms has indicated that the Phase-locked Loop (PLL) bandwidth significantly impacts Sub-Synchronous Resonance (SSR). However, the influence of PLL architecture on SSR remains unexplored and warrants investigation. Therefore, this paper investigates PLL architectural variations in PLL Loop Filter (LF) to understand their impact on SSR in type 4 wind farms. Specifically, an in-depth analysis of the Notch Filter (NF)-based enhanced PLL is conducted using eigenvalue analysis of the admittance model of a PMSG-based type 4 wind farm. The findings demonstrate that the NF-based enhanced PLL exhibits superior performance and improved passivity in the sub-synchronous frequency range, limiting the risk of SSR below 20 Hz. Additionally, Nyquist plots are employed to assess the impact on system stability resulting in increased stability margins. In the future, it is recommended to further investigate and optimize the PLL to mitigate SSR in wind farms.

A New Power-Frequency Oscillation Suppression and Power Allocation Control Method Based on MPC in Multi-VSGs Parallel System

The virtual synchronous generator (VSG) technology can provide frequency support for power systems that are dominated by renewable power sources. However, it also introduces the characteristic of active power oscillation, which can cause power-frequency oscillation between parallel VSGs when there are disturbances in the load power or command power. To address this problem, this paper proposes that the idea of equivalent comparison can be used to compare the power-frequency interaction of N-VSGs parallel systems with the current-voltage interaction of N-RLC circuits. This allows us to establish a mathematical model of the parallel VSGs system based on Kirchhoff’s equation of the circuit. Using this model, we designed a new power-frequency oscillation suppression and a power allocation control method based on the model predictive control (MPC) in multi-VSGs parallel systems. This method can effectively suppress power-frequency oscillation in each VSG branch after a disturbance occurs, and accurately allocate active power according to instructions. Finally, simulation results confirm the effectiveness of the controller.

Synergistic effect of complementary cleaner energy sources on controllable emission from hybrid power systems in optimal power flow framework

The increased penetration of renewable energy resources into the power system may make the system operation extremely vulnerable due to their inherent volatility and variability. Thus, optimum utilization of cleaner power generation into the power system without affecting the operational economy, voltage security and stability becomes a challenging issue. To minimize this adverse impact of intermittent renewable resources, hydro power sources may be considered as an effective option. Inclusion of hydro power may contribute towards optimal utilization of the abundant clean energy and enhance the capability to mitigate the volatile renewable power sources while forming a stable hybrid power system (HPS). In this context, an intelligent generation scheduling (IGS) mechanism is proposed to effectively mitigate these complex challenges. To further analyze these issues, multiple case studies under different operating conditions are carried out to portray the significance of incorporating the complementary behaviour of hydro-solar generation with thermal power generation facilities in environmental optimal power flow (EOPF) framework. Widely accepted IEEE 30 bus benchmark system is considered for the validation of results. Optimal operational paradigm (OOP) for the three different HPS configurations i.e. (1) Solar-Thermal (ST); (2) Hydro-Thermal (HT); and (3) Solar-Hydro-Thermal (SHT) is evaluated using Jaya algorithm (JA) while meeting the real time constraints. With the OOP, a comparative performance evaluation is carried out among different hybrid configurations in fulfilling the multiple objectives. Results show the supremacy of SHT configuration in minimizing the operating cost by 1.324×105 US$/y to 2.445×105 US$/y and emission up to 15.768 Tons/y compared to other configurations.

Experimental Characterization of a Novel Fluidized‐Bed Zn–Air Fuel Cell

AbstractZn–air fuel cells are promising energy storage devices for renewable energy and power sources, as they are cost‐effective and have high energy density. However, limited charge and discharge cycles and low round‐trip efficiency have long been obstacles to large‐scale market deployment. Herein, a new fluidized‐bed zinc–air fuel cell is designed, constructed, tested, and characterized. The integration of the fluidized bed in the zinc–air fuel cell leads to key advantages such as: erosion of the anode passivation layer, which plays a key role in the rapid voltage decay and keeping the products of reactions away from the proximity of the electrodes, reducing the concentration overpotential, due to the concentration gradient of electrode species in the diffusion boundary layer between the electrode–electrolyte interface and the electrolyte bulk.