Off-grid System Research Articles

Optimizing microgrid integration of renewable energy for sustainable solutions in off/on-grid communities

Rising energy costs, climate change impacts, and transmission losses have increased demand for renewable energy sources and decentralized solutions. As more people seek smart living and working environments, integrated smart microgrids powered by hybrid renewable systems have become attractive solutions for off-grid and on-grid communities. This study proposes designing a solar-wind-battery hybrid microgrid supplying a medical load et al.-Ain Al-Sokhna, Egypt. The optimization objectives aim to minimize the loss of power supply probability (LPSP %) and the levelized cost of energy (LCOE, $/kWh). A key consideration when designing and optimizing hybrid microgrids is the energy management strategy, which coordinates different generation sources and fluctuating load demand. Therefore, optimization algorithms were applied to balance energy flows while meeting loads, mitigating weather impacts, and preventing overcharging/deep discharge of battery storage. Models of wind turbines, photovoltaic panels, and battery storage were developed to simulate and analyze proposed microgrid operations. A multi-objective optimization approach evaluated LPSP and LCOE metrics using transit search, grey wolf, and particle swarm algorithms to find optimal system configurations. The optimization algorithms demonstrated varying performances in minimizing the multi-objective functions for the on-grid and off-grid microgrids. The particle-swarm optimization technique is the best solution for the off-grid system, which contains PV, wind, and battery storage, with a minimum LCOE of 0.3435 $/kWh and an LPSP of 4.5334%. Meanwhile, the transit-search optimization algorithm found the optimal solution for the on-grid configuration according to the objective function, yielding an LCOE of 0.116 $/kWh and an LPSP value of 3.0639 × 10−16. Statistical analysis confirmed that the algorithms generally exhibited stable and robust optimization capabilities. Of the methods, transit search was the most effective overall optimization approach.

A Sustainable Hybrid Off-Grid System Design for Isolated Island Considering Techno-Economic and Frequency Stability Analysis

Electrifying remote islands presents complex challenges. Currently, most remote areas in Indonesia rely on diesel fuel for their electricity supplies, contributing to escalating generation costs and environmental degradation. Aligned with the global net-zero emission goal, this study proposes the design of a hybrid off-grid system for Kabare Village in the Raja Ampat Islands, integrating techno-economic and frequency stability analyses. HOMER Pro was employed to identify the most optimal system configuration, while DIgSILENT PowerFactory was utilized to assess the frequency stability performance of the system. This study unveils that the optimal system combines existing generators, solar panels, and batteries, with a net present cost of $1.37 million. The optimal system delivers an 11.8% reduction in levelized cost of energy to $0.269/kWh, alongside a 25.6% decrease in both fuel consumption and greenhouse gas emissions compared to the existing system. Moreover, the system meets frequency stability metrics, even under extreme operational conditions. This study demonstrates that implementing a hybrid off-grid system in Kabare Village is not only technically and economically feasible but also a practical option. These findings are anticipated to assist the government in promoting the utilization of renewable energy sources, particularly in remote areas such as the islands of eastern Indonesia.

Low-voltage DC-DC off-grid PV system: various irradiance studies

The off-grid photovoltaic (OGPV) system, also referred to as a stand-alone power system, generates electricity from solar energy independently of the main electricity grid. However, photovoltaic (PV) modules face limitations in consistently providing the necessary voltage. Thus, a DC-DC converter is employed to adjust the voltage to match the requirements of the load. This paper proposes a detailed analysis of irradiance patterns resembling in-lab and real-world conditions to address the challenge of selecting the optimal DC-DC OGPV system capable of functioning effectively under standard test condition (STC) and dynamic test condition (DTC), respectively. Three proposed irradiance analyses, tailored to different environmental scenarios, aim to identify output performances for DC-DC OGPV system which are aligning with standards set by the International Electrotechnical Commission (IEC) 61727. The DC-DC OGPV system is simulated using MATLAB Simulink. Furthermore, comparative studies involving different PV module types and several switching techniques (pulse generator and maximum power point tracking or MPPT implementations), where findings are instrumental in advancing the development and projection planning for medium to high-voltage OGPV systems, contributing to the global initiative for accessible and sustainable energy solutions aligned with sustainable development goal (SDG 7).

Corrigendum to “An off-grid solar district energy system with borehole thermal energy storage: Life cycle assessment in a subarctic region”

Corrigendum to “An off-grid solar district energy system with borehole thermal energy storage: Life cycle assessment in a subarctic region”

Techno-economic feasibility analysis and optimisation of on/off-grid wind-biogas-CHP hybrid energy system for the electrification of university campus: A case study

This paper provides a comprehensive feasibility analysis of a hybrid energy system with different configurations to meet electricity and thermal load demand at the University of Southampton campus. The suggested hybrid energy system (HES) comprises wind turbine, biogas generator, battery, CHP natural gas-generator, thermal load controller, boiler, and converter and is simulated in Homer Pro software. In addition, a comparative analysis between stand-alone and on-grid HES is presented. The results indicate that the grid-connected HES is significantly more cost-effective, with a 45% reduction in cost of energy (COE) and %15.5 decrease in net present cost (NPC) compared to the off-grid system, which amounts to 0.03359 $/kWh and 467M$, respectively. The grid-connected HES is not only more eco-friendly in terms of greenhouse gas emissions (GHG) and produces 19% less emissions annually compared to the grid-independent system, but it also effectively achieves a positive return on investment (ROI) of %45 with 2.3 years of payback time. Considering the university’s total emissions of 38.56 kT CO2e, the proposed on-grid hybrid system has the potential to lessen GHG emissions by 91.2%.

Techno-economic analysis of green hydrogen production from wind and solar along CPEC special economic zones in Pakistan

Hydrogen-based systems are garnering attention as part of efforts to achieve low-carbon emissions and net-zero targets. In developing countries, natural gas and coal serve as a primary source for hydrogen production, given their accessibility and cost-effectiveness. Green hydrogen presents a promising clean energy solution with significant potential to decarbonize the industrial sector. In this article, a techno-economic analysis has been performed for green hydrogen production using wind and solar as primary energy sources. The analysis is conducted at nine special economic zones (SEZs) and a free zone at Gwadar Sea Port using the Hybrid Optimization of Multiple Energy Resources (HOMER) Pro software. A hybrid energy system has been designed to meet the industrial electrical and hydrogen demand of 600 MWh/day and 60 tonnes H2 per day, respectively. A comparative analysis of on-grid and off-grid systems across all SEZs is performed for the optimal system. A sensitivity analysis is conducted on different parameters that could impact the levelized cost of hydrogen (LCOH). The results indicate that LCOH varies from 4.19 $/kg to 8.66 $/kg for off-grid and 2.12 $/kg to 4.65 $/kg for on-grid systems which is a competitive cost to other countries. The most feasible economic zones for green hydrogen production are found to be Dhabeji and Port Qasim with the lowest LCOH of 4.19 $/kg and 4.22 $/kg for off-grid, 2.12 $/kg and 2.36 $/kg for the grid-connected system, respectively. Dhabeji also exhibits the lowest CO2 emissions per year making itself the most feasible location for green hydrogen production. Grid-connected systems are a great opportunity for Pakistan to produce low-cost green hydrogen for industrial decarbonization and the country’s economic growth.

A novel Zero Back Power Flow (ZBPF) controlled DAB for DC bus stability and energy storage integrations in hybrid DC/AC off-grid systems

The paper presents an innovative approach for integrating energy storage devices into hybrid AC/DC grids to ensure a consistent power supply for modern loads. It introduces a Zero Back Power Flow (ZBPF) enabled bi-directional Dual Active Bridge (or, Direct AC-AC Boost) (DAB) controller strategy aimed at enhancing the power handling capacity DABs, while offering adaptable control for the microgrid system. Utilizing the proposed ZBPF control technique, the system endeavors to improve the power quality of the high-frequency AC link and regulate power transfer across DAB converter. Furthermore, a power management control strategy is described to facilitate efficient power flow among the diverse sources and loads within the hybrid off-grid system via battery system. By incorporating multiple utility features, the system aims to maintain stable bus voltages and mitigate potential power supply reliability issues. The paper concludes with simulation results validating the efficacy of the proposed ZBPF DAB control algorithms in grid forming operational modes, demonstrating the feasibility and effectiveness of the proposed solution. Additionally, the proposed ZBPF controller is tested on a hardware platform using batteries. An experimental setup has been conducted to verify the operation of the proposed ZBPF modulation scheme for a DAB converter in a practical setting. It involves implementing the ZBPF modulation scheme using a Hardware-in-the-Loop (HIL) setup and testing the DAB converter under both forward and reverse power flow modes.

Optimal Design of an Off-Grid Solar Energy System Integrated with a Diesel Generator for Urban Areas in Pakistan

The growing energy demand in Pakistan, coupled with the challenges posed by reliance on imported fossil fuels, necessitates the exploration of alternative energy solutions. This study presents the design and techno-economic analysis of an off-grid hybrid energy system tailored for a residential neighborhood in Karachi, Pakistan. The system integrates individual solar energy solutions for seven housles, supplemented by a shared diesel generator to ensure a reliable power supply, particularly during load-shedding and grid outages. The study utilizes HOMER Pro software to model and optimize various configurations, taking into account local solar insolation levels and seasonal variability in energy demands. The optimized system includes photovoltaic (PV) panels, battery storage, and a shared diesel generator with individual connections and meters, with each house receiving a customized solution based on its specific energy requirements, ranging from 15 kWh/day to 45 kWh/day. The shared diesel generator is designed to reduce the need for large battery banks, thereby minimizing both capital and operational costs. The results demonstrate a cost-effective solution with a Levelized Cost of Energy (LCOE) of $0.2959/kWh and a Net Present Cost (NPC) of $15,562.55 over a 25-year period. This research highlights the potential for implementing such systems in urban areas of Pakistan, offering a sustainable, reliable, and economically viable alternative to conventional energy sources.

Optimization scheduling of off-grid hybrid renewable energy systems based on dung beetle optimizer with convergence factor and mathematical spiral

With the rapid development of renewable energy and the increasing modernization demands in remote areas, off-grid hybrid renewable energy systems (HRES) have become a key technology for achieving sustainable development. This paper presents an improved Dung Beetle Optimization (DBO) algorithm that enhances step size by introducing six elementary functions as convergence factors. It combines polar coordinate expressions of three different mathematical spirals, multiplied by a zeroing factor related to the number of iterations, resulting in six distinct mathematical images that optimize the algorithm's dancing path, thereby enhancing global search capability. Experiments on the CEC2022 test functions demonstrate improved optimization performance of the algorithm. Furthermore, the algorithm is applied to the optimization design of off-grid HRES, integrating configurations such as photovoltaic panels, wind turbines, biomass generators and various battery types (Lead Acid battery/Lithium-Ion/Nickel-Iron), with lifecycle cost as the objective function while assessing energy costs. The results indicate that the nickel-iron battery system optimized by the improved DBO algorithm achieves the lowest lifecycle cost ($961,139) and energy cost ($0.3607/kWh), requiring a total of 1329 PV panels, no wind turbines, and 268 nickel-iron battery units.

Optimized Energy Management Strategy for an Autonomous DC Microgrid Integrating PV/Wind/Battery/Diesel-Based Hybrid PSO-GA-LADRC Through SAPF

This study focuses on microgrid systems incorporating hybrid renewable energy sources (HRESs) with battery energy storage (BES), both essential for ensuring reliable and consistent operation in off-grid standalone systems. The proposed system includes solar energy, a wind energy source with a synchronous turbine, and BES. Hybrid particle swarm optimizer (PSO) and a genetic algorithm (GA) combined with active disturbance rejection control (ADRC) (PSO-GA-ADRC) are developed to regulate both the frequency and amplitude of the AC bus voltage via a load-side converter (LSC) under various operating conditions. This approach further enables efficient management of accessible generation and general consumption through a bidirectional battery-side converter (BSC). Additionally, the proposed method also enhances power quality across the AC link via mentoring the photovoltaic (PV) inverter to function as shunt active power filter (SAPF), providing the desired harmonic-current element to nonlinear local loads as well. Equipped with an extended state observer (ESO), the hybrid PSO-GA-ADRC provides efficient estimation of and compensation for disturbances such as modeling errors and parameter fluctuations, providing a stable control solution for interior voltage and current control loops. The positive results from hardware-in-the-loop (HIL) experimental results confirm the effectiveness and robustness of this control strategy in maintaining stable voltage and current in real-world scenarios.

Size optimization of standalone wind-photovoltaics-diesel-battery systems by Harris hawks optimization (HHO): Case study of a wharf located in Bushehr, Iran

The global increase in energy demand has led to a growing focus on renewable energy sources as a potential solution. This study examines the annual total cost of optimized off-grid hybrid multi-resource systems, considering various configurations of Wind Turbines (WT), Photovoltaics (PV), Diesel Generators (DG), and Batteries (Bat). The research focuses on an oil dock in Bushehr, Iran, as a case study. The optimization process employs the Harris Hawk Optimization (HHO) algorithm – which is used for the first time for hybrid configuration and optimal sizing in this paper-, a nature-inspired, population-based optimization technique. This algorithm’s performance is compared to conventional optimization methods to assess its efficiency. The study’s methodology involves: (1) Explaining the economic relationships for each energy source, (2) Formulating a cost function, (3) Using the HHO algorithm to minimize the total cost of the renewable energy-based hybrid systems. The HHO algorithm is inspired by the hunting behavior of Harris hawks, specifically their “wonder attack” strategy. This novel approach to optimization aims to find the most cost-effective configuration of energy sources for the given scenario. Key findings of the study include the HHO algorithm demonstrated superior efficiency compared to Particle Swarm Optimization (PSO) and Gray Wolf Optimizer (GWO) across all configurations tested. The most cost-effective configuration was found to be a combination of photovoltaics, batteries, and diesel generators. This setup had the lowest total annual cost among all configurations examined. The optimal system consisted of 450 photovoltaic units, 9 battery units, and 2 diesel generator units, with a minimum annual cost of approximately $355,525. These results highlight the potential of the HHO algorithm in optimizing renewable energy systems and demonstrate the complex trade-offs between cost and environmental impact in hybrid energy configurations. The study contributes valuable insights to the field of renewable energy system design and optimization, particularly for off-grid applications in industrial settings.

Dual-objective optimization of solar driven alkaline electrolyzer system for on-site hydrogen production and storage: Current and future scenarios

Achieving cost competitiveness of renewable hydrogen could accelerate the transition to the deeply decarbonized energy system. In this article, we develop and apply a dual-objective optimization model to explore the photovoltaic (PV) hydrogen production pathway and costs development from the present through 2050. The model is applied for optimal capacity allocation of the megawatt-scale off-grid PV-Hydrogen system to achieve maximum production at the minimal levelized cost of hydrogen (LCOH). Methodology includes a smoothing control strategy. Simulation is performed utilizing measured meteorological data for one year with hourly resolution and considering electrolyzer's load flexibility constraint. It has been found that the smoothing control strategy is indispensable for maximizing PV energy utilization, enhancing the electrolyzer's capacity factor and reducing the power curtailments. The analysis shows that the off-grid solar hydrogen in Algeria lacks economic competitiveness currently. Components CAPEX reduction turns out to be the fundamental condition towards the future LCOH decrease. LCOH could decline from 4.2 $/kg in 2025 to 2.24 $/kg in 2050 under central assumptions and to roughly 1.4 $/kg under optimistic assumptions. Alkaline electrolysis step cost could reduce by 0.28 $/kg every decade. Hydrogen storage autonomy could rise the LCOH by 7.1 c$ per day of autonomy in 2050.

Load profiles of residential off-grid solar systems on the Navajo Nation

Standalone off-grid electrical systems, no matter where they are deployed or for what user class, are designed based upon the load they are expected to serve. State-of-the-art computerized off-grid system design tools require the user to specify the expected load profile, that is, how the power consumption changes throughout the day. Often, this is at an hourly resolution, and some characterization of the distribution of power around the average values may be required. Specifying realistic and reasonable load profiles is a barrier to the appropriate design of standalone systems. This research extends previous studies on daily energy consumption of residential solar-powered off-grid systems on the Navajo Nation to provide hourly load profiles, statistical characteristics, and probabilistic models. The data analyzed come from 90 homes over a two-year period. K-means clustering is used to identify prototypical normalized load profiles when the data are grouped by year, season, weekday, and weekend. Eight parametric probability density functions are fit to the grouped data at an hourly resolution. Their fit to the data is evaluated using the Cramér-von Mises (CvM) statistic. The results show that the load profiles tend to be night-peaking and that Log Normal and Gumbel distributions can reasonably model variation in the data. The load profiles and probabilistic models can be used in off-grid design software and to synthesize load profiles for design and future research.

Optimal operation control strategy for off-grid photovoltaic hydrogen production system considering hydrogen production efficiency

Off-grid photovoltaic hydrogen production is an effective solution for improving photovoltaic (PV) utilization and obtaining green hydrogen. The main challenge faced by off-grid photovoltaic hydrogen production systems (OGPHPS) is how to deal with the randomness, intermittency, and volatility of PV generation. Therefore, this paper proposes an optimal operation control strategy (OOCS). First, a model of OGPHPS is established, comprising photovoltaics, batteries, and an electrolytic array (ELA). Second, a two-step optimization strategy (TSOS) that integrates both long-term and short-term time scales is proposed. In the first step of TSOS, the day-ahead optimization of the operation state of ELA is conducted according to day-ahead power prediction. A constraint was proposed to balance the operation time of the electrolyzer. In the second step of TSOS, according to the ultra-short time power prediction and the electrolyzer efficiency curve, the rolling optimization of the operating power distribution of ELA is carried out. Through TSOS, PV generation consumption is maximized by ELA, the continuous operational stability of OGPHPS is enhanced, and the lifespan of electrolyzer is extended. Third, to alleviate the influence of instantaneous power fluctuation on the system, an energy management strategy (EMS) for OGPHPS is proposed. Finally, a simulation model of OGPHPS was established, and the simulation results showed that the direct current bus voltage fluctuation was within 3%. Compared to the chain allocation strategy, the OOCS achieves higher hydrogen production under the same solar irradiance conditions. Particularly in low irradiance, OOCS has more sufficient consumption of PV generation and higher hydrogen production efficiency.

Hybrid renewable energy systems for sustainable power supply in remote location: Techno-economic and environmental assessment

Electricity supply is inconsistent and unreliable in many remote areas of India, where depending solely on a single renewable energy source is impractical. In this context, this study investigates the potential of off-grid hybrid renewable energy systems (HRES) to meet the energy needs of a village community in India. Techno-economic analysis and life cycle assessment have been employed to compare eleven HRES combinations which combine photovoltaic (PV), wind turbine (WT), battery (BAT), diesel generator (DG), biogas generator (BG), converter (CONV), and electrolyser (ELEC). By optimising the size and capacity of each component in HRES, this study aims to identify the combination with the lowest levelised cost of electricity (LCOE). This research aligns with United Nations Sustainable Development Goal No. 7 to seek “Affordable and Clean Energy”. The findings highlight that HRES comprising PV/WT/BAT/CONV/DG exhibits the lowest LCOE (0.319 $/kWh) and net present cost (6.81 M$) among all combinations. In systems with partial reliance on diesel, integrating both PV and WT could reduce diesel consumption and increase the renewable fraction to 87.4 %. For HRES involving PV, a significant contribution to greenhouse gas emissions occurs during the construction stage. The WT/DG combination, with its high diesel dependency, has the largest global warming potential. The efforts from this study provide valuable insights into determining the optimal HRES for remote communities by considering their economic and environmental factors.

Advanced control strategies for multilevel inverter in grid-connected and off-grid photovoltaic systems: A multi-objective approach using LS-PWM for THD reduction

Advanced control strategies for multilevel inverter in grid-connected and off-grid photovoltaic systems: A multi-objective approach using LS-PWM for THD reduction

Performance analysis of hybrid off-grid renewable energy systems for sustainable rural electrification

Delivering sustainable power to rural communities in sub-Saharan Africa, particularly in Somalia, where many areas are far from the electrical grid and suffer from energy shortages, necessitates the deployment of appropriate technologies. This study evaluates the techno-economic and environmental viability of a hybrid renewable energy system (HRES) comprising a 15 kWp photovoltaic (PV) generator, 10 kW wind turbine (WT), 25 kW diesel generator (DG), and a 72-kWh battery energy storage system (BESS). The HRES is proposed to supply sustainable power to a rural community in Somalia. The techno-economic assessment of the proposed HRES and a comparative analysis of other configurations—namely the PV/WT/BESS and PV/DG/BESS systems is conducted using HOMER and MATLAB software. The results indicate that the proposed PV/WT/DG/BESS HRES demonstrates superior techno-economic performance compared to the other configurations. The lowest net present cost of $96,899.16 and the levelized cost of energy (LCOE) of $0.090/kWh were achieved. This system attains 25 % excess electricity, maintains a 0 % unmet electric load, and demonstrates robust environmental performance with a renewable penetration rate of 91.8 %. Approximately 53.34 % of greenhouse gas emissions are reduced compared to the PV/DG/BESS configuration. The study confirmed the significant impacts of all sensitivity parameters on operational costs, LCOE, fuel prices, fuel intake, and renewable fraction. The overall results indicate superior performance in the optimal system case, offering a feasible and suitable choice for the sustainable electrification of rural communities.

Hybrid solar and hydrogen energy system 0-D model for off-grid sustainable power system: A case in Italy

Off-grid solar systems are one of the most promising solutions for achieving complete grid independence. However, the storage of large amounts of energy produced in the summer through solar panels becomes crucial to reach this goal and hydrogen, as a zero-CO2 energy carrier, could play a pivotal role. This paper presents a case study on the integration and simulation of solar energy and hydrogen technologies in an off-grid energy plant for a teaching buildings complex in Italy. A 0-D virtual energy plant model has been developed aimed at estimating the net energy production and hydrogen consumption/production rates using different inputs of irradiance (monthly average, daily) and energy demand (constant and variable daily consumption levels) in the buildings. The outcome of the analysis identifies the most convenient configuration of the plant in terms of sizing and device interactions for achieving complete grid independence, and the impact of different inputs on the plant performance.

PROPOSTA DE ELETROPOSTOS MODULARES PARA CARROS ELÉTRICOS ABASTECIDOS POR ENERGIA SOLAR

In recent years, the growing demand for electric vehicles has intensified the need for adequate infrastructure for their charging. Charging stations, dedicated to supplying energy to these vehicles, play a crucial role in the transition to sustainable urban mobility. This study proposes the development of modular charging stations powered by solar energy, focusing on solutions that favor sustainability and efficiency. The primary objective is to create systems that integrate photovoltaic technology, promoting the use of clean energy and contributing to the reduction of air pollution. The research evaluates the viability of on-grid and off-grid systems, aiming to optimize the efficiency of solar panels and reduce operational costs. Factors such as ideal location, shading prevention, and the environmental impacts of electric mobility are analyzed. Additionally, existing charging station examples are examined to identify best practices and innovations in urban design. The methodology includes exploratory and bibliographic research, utilizing case studies and literature reviews to support the proposal. As a result, the study culminates in a sustainable modular charging station proposal that is adaptable to different locations, promoting more efficient and eco-friendly mobility.

Aging Retardation of Lead-Acid Batteries by Adjusting Charge Controller Threshold Values in Off-grid Photovoltaic System

Hybrid systems or coupled power plants with energy storage are becoming more and more popular due to the rising need for energy. Researchers have been conducting several experiments to assure longer-lasting battery use due to the increasing widespread use of energy storage and the depletion of resources such as silicon and precious metals. In this study, a simulation study is carried out in PVSyst software on lead-acid batteries, which have a low cycle and a very traditional electrochemical structure. The simulation is realized by scaling Spain’s consumption curve in 2023, taken from the European Network of Transmission System Operators for Electricity (ENTSO-E), together with lead acid batteries and off-grid photovoltaic (PV) modules. After the off-grid system design is created and consumption data is imported, it is aimed to extend battery life by changing the charge-discharge threshold values of the charge controllers. Threshold values are in two categories, high and low, and seventeen different cases are simulated. According to the results of the simulation, the state of charge (SOC) levels of the batteries decreases significantly due to radiation and cloudiness in the winter months and remain high in the spring and summer months. When charge controllers are set to high thresholds levels, they cause gassing currents that rise to an average of 20 amps, while battery life extends up to 5.3 years. When low threshold values are used, negligible levels of oxygen and hydrogen gasses are formed in the battery, but battery life decreases to 4.1 years.