Energy Efficiency Of System Research Articles

Thermodynamics analyses on a novel CHP system integrated with multi-grade thermal energy storage

The high penetration level of intermittent renewable power necessitates the crucial requirement for combined heat and power systems to possess both high efficiency and flexibility. However, the heat-controlled operation modes of traditional combined heat and power systems impose limitations on their efficiency and flexibility. Therefore, it is of great significance to develop a heat-power decoupling technology that exhibits exceptional efficiency and flexibility. A novel combined heat and power system integrated with multi-grade thermal energy storage is proposed in this study. Thermodynamic analysis models of all operational conditions are developed, and the comprehensive characteristics of efficiency and operational flexibility for the proposed system are assessed by taking a 330 MW system as an example. Results show that the proposed system can decrease/increase 16.05 MW/30.96 MW power loads comparing with the reference system during the charging/discharging periods under the design condition. Energy efficiency of the proposed system can reach 49.40 %, which is improved by 1.66 percentage points. Exergy analysis reveals the exergy destruction order for the proposed system, and shows that the combustion and heat transfer in the boiler are the major process of exergy dissipation. Moreover, operation strategies of the proposed system during charging-discharging cycle are explored and formulated under off-design condition, suggesting that thermodynamic performances of the novel system under various conditions even extreme conditions exhibits exceptional properties. The maximum heat load of the proposed system can be improved by 46.78 % comparing with the reference system, and the maximum improvement of power load capacity during charging-discharging cycle is 14.58 percentage points. This study provides a promising approach for multi-grade thermal energy storage to improve the comprehensive characteristics of combined heat and power systems.

The Integration of Thermal Energy Storage Within Metal Hydride Systems: A Comprehensive Review

Hydrogen storage technologies are key enablers for the development of low-emission, sustainable energy supply chains, primarily due to the versatility of hydrogen as a clean energy carrier. Hydrogen can be utilized in both stationary and mobile power applications, and as a low-environmental-impact energy source for various industrial sectors, provided it is produced from renewable resources. However, efficient hydrogen storage remains a significant technical challenge. Conventional storage methods, such as compressed and liquefied hydrogen, suffer from energy losses and limited gravimetric and volumetric energy densities, highlighting the need for innovative storage solutions. One promising approach is hydrogen storage in metal hydrides, which offers advantages such as high storage capacities and flexibility in the temperature and pressure conditions required for hydrogen uptake and release, depending on the chosen material. However, these systems necessitate the careful management of the heat generated and absorbed during hydrogen absorption and desorption processes. Thermal energy storage (TES) systems provide a means to enhance the energy efficiency and cost-effectiveness of metal hydride-based storage by effectively coupling thermal management with hydrogen storage processes. This review introduces metal hydride materials for hydrogen storage, focusing on their thermophysical, thermodynamic, and kinetic properties. Additionally, it explores TES materials, including sensible, latent, and thermochemical energy storage options, with emphasis on those that operate at temperatures compatible with widely studied hydride systems. A detailed analysis of notable metal hydride–TES coupled systems from the literature is provided. Finally, the review assesses potential future developments in the field, offering guidance for researchers and engineers in advancing innovative and efficient hydrogen energy systems.

Three-Dimensional Printing of Bioinspired Hierarchical Structures for Enhanced Fog Collection Efficiency in 3D Space via Vat Photopolymerization

Collecting fog water is crucial for dry areas since natural moisture and fog are significant sources of freshwater. Sustainable and energy-efficient water collection systems can take a page out of the cactus’s playbook by mimicking its native fog gathering process. Inspired by the unique geometric structure of the cactus spine, we fabricated a bioinspired artificial fog collector consisting of cactus spines featuring barbs of different sizes and angles on the surfaces for water collection and a series of microcavities within microchannels inspired by Nepenthes Alata on the bottom to facilitate water flowing to the reservoir. However, replicating the actual shape of the cactus spine using conventional manufacturing techniques is challenging, and research in this area has faced a limitation in enhancing water-collecting efficiency. Here, we turned to 3D printing technology (vat photopolymerization) to create bio-mimetic fog collectors with a variety of geometric shapes that would allow for the most effective conveyance and gathering of water. Various barb sizes, angles between each barb in a single array, spine and barb arrangements, and quantity of barbs were tested experimentally and numeric analysis was carried out to measure the volume of water collected and optimize the mass rate. The result shows that optimal fog collection is with a mass flow rate of 0.7433 g/min, with Li = 900 μm, θ = 45°, ϕ = 90°, Nb = 2, and Ns = 5. This study presents a sustainable and ecologically sound method for efficiently collecting humid air, which is expected to be advantageous for the advancement of future-oriented fog-collection, water-transportation, and separation technologies.

Energy systems integration and sector coupling in future ports: A qualitative study of Norwegian ports

Ports will play an important role in the decarbonisation of maritime transport towards 2050, and for the energy transition in a larger perspective. In this context, options for integrating multiple energy carriers and end-user sectors are seldom addressed. This study aims at qualitatively assessing the energy transition in Norwegian ports, centred around energy supply to the maritime sector, but with a particular focus on sector coupling and energy system integration. To elaborate on plausible energy systems in ports towards 2050, four exploratory scenarios were designed, driven by a low or high techno-economic and socio-technical development. Four case ports were selected for the scenario assessment, differing in ship traffic, ownership, location, port activities, nearby industries, current energy carriers, and ambition level for energy transition.The assessment of the four case ports reveals many options for energy and sectoral interactions. Following the electrification of maritime and road transport, as well as the port itself and nearby industries, it was shown that sector coupling facilitates renewable power production in all case port. A more complex multi-energy carrier integration, e.g., between electricity, heat and hydrogen, is of special relevance for ports located near offshore wind establishments and heat demanding sectors like aquaculture industry or buildings with central heating. Here, sector coupling could trigger hydrogen production in the port area, and thereby enable hydrogen supply to ships. Concludingly, energy and sectoral interactions contribute towards a decarbonised, flexible and efficient port energy system, however, the benefit depends on port characteristics and energy transition scenarios.

Intelligent fuzzy-PSO based grid connected solar EV charging station for electric buses to enhance stability and energy management

Abstract Modern power networks are relying more and more on Distributed Generation (DG) and solar energy-powered Electric Bus (EB) charging stations; nevertheless, controlling the charging process under situations of peak EB load and variable solar irradiation presents considerable hurdles. This study presents a coordinated control approach that maximizes energy distribution for solar (PV)-based EB charging stations by using an intelligent energy management system (IEMS). Through the analysis of load demand and meteorological data in real time, the IEMS optimizes PV generation and grid power consumption, thereby halving peak power demand, minimizing system losses, and easing distribution grid stress. In order to enable dynamic modifications to the energy flow between PV power, the grid, and battery storage, the method integrates an adaptive neuro-based fuzzy control system that anticipates solar energy generation and predicts EB load demands. Furthermore, to balance power distribution between battery and ultracapacitor systems and control energy storage in ultracapacitors, a fuzzy inference system optimized using Particle Swarm Optimization (PSO) is utilized. This prolongs battery life and guarantees effective energy management. The overall performance of the IEMS is improved by the fuzzy logic controller, which produces output signals that specify the best power distribution for any energy storage system. Digital simulations and a real-time hardware-in-loop experimental setup are used to validate the effectiveness of the proposed system, which shows notable gains in energy management, grid stability, and system efficiency. In order to improve intelligent energy management in grid-connected solar-powered systems, this study offers a viable method for incorporating renewable energy sources into EB charging stations.

Hydropneumatic Storage Methodology Towards a New Era of Hybrid Energy System's Efficiency and Flexibility

This research explores the link between hydropneumatic energy storage capacity and the efficiency and flexibility of hybrid energy systems in water-energy solutions. A new methodology is introduced, featuring mathematical models, experimental data collection, and hydraulic simulations using 1D and 2D CFD models for hydropneumatics modeling. A promised energy storage efficiency of around 30-50% was obtained on a small lab scale. The optimization of hybrid systems through Solver and Python algorithms with various objective functions enables optimal design choices tailored to specific needs such as drinking water supply, irrigation, or industrial processes. Hydropneumatic vessels emerge as an effective storage solution, combining pumped storage and hydropower in one circuit. When integrated with renewable sources, such as solar (PV) and wind energy, they offer a flexible, long-lasting energy management system, applicable across different water-energy sectors to support Sustainable Development Goals. A case study with 4.8 Mm³/year water allocation, producing 1000 MWh of hydropower and 13500 MWh of solar energy, achieved 100% water reliability and a 25-year cash flow of 2.5 million euros.

Unlocking the potentials using humidifier-dehumidifier for proton exchange membrane fuel cell waste heat recovery

This study addresses the dual challenges of waste heat dissipation and operational longevity degradation in proton exchange membrane fuel cells (PEMFCs) by proposing a novel hybrid system that integrates PEMFC with a humidifier-dehumidifier (HDH) unit. The primary objective is to enhance the energy efficiency and sustainability of PEMFC systems by leveraging waste heat for freshwater generation. A comprehensive mathematical model based on thermodynamic and electrochemical principles is developed to capture the system’s inherent irreversible losses. The performance metrics, including power density, energy efficiency, and exergy efficiency, are evaluated through systematic computational simulations. The proposed PEMFC/HDH hybrid system achieves a maximum power density of 4.8292 W cm-2 and an energy efficiency of 17.30%, showing a 1.48% improvement over standalone PEMFC systems. Parametric studies reveal that optimizing operating pressure significantly enhances system performance, while factors such as increased PEM thickness and thermodynamic loss composite parameter hinder it. Local sensitivity analysis identifies PEM thickness as the most critical parameter affecting performance. This research pioneers the integration of PEMFC and HDH for cogeneration, offering a viable path for performance enhancement and efficient waste heat utilization. The findings contribute to the strategic design and operational regulation of PEMFC-based hybrid systems for sustainable energy solutions.

Energy efficiency and economic performance of a low-temperature heating system combining double-layer pipe-embedded wall and ground source heat pump

Reducing heating energy consumption in buildings is a crucial step towards a low-carbon future. The energy efficiency of heat pump heating systems can be improved by reducing the water supply temperature of terminals. However, existing terminals are limited in using lower-temperature hot water and leaves potential for energy savings. Therefore, this study proposes a double-layer pipe-embedded wall heating system coupled to a ground source heat pump. The outer pipes use shallow geothermal energy to reduce envelope load, whereas the inner pipes use water produced by the heat pump to provide heating. Energy, economic, and carbon emission analysis models of the proposed system are developed. A residential heating case study is conducted in Harbin, Shenyang, Beijing, Zhengzhou, and Shanghai to investigate the performance of the proposed system. The results show that the proposed system achieves much lower-temperature heating than the reference floor heating system. The seasonal energy savings of the proposed system in the selected cities are 12%–18%, with a SCOP of 4.0–5.8. The dynamic payback period of the proposed system is 1.6–4.3 years and the CO2 emission intensity is reduced by 1.2–3.2 kg/m2. This study provides an insight into the application of DPEW heating systems.

Optimization and Thermodynamic Analysis of CO2 Refrigeration Cycle for Energy Efficiency and Environmental Control

Supermarket applications are significant contributors to greenhouse gas emissions, necessitating efforts to reduce carbon footprints in the food retail sector. Carbon dioxide (R744) is recognized as a viable long-term refrigerant choice due to its favorable properties, including low Global Warming Potential, non-toxicity, non-flammability, affordability, and widespread availability. However, enhancing the energy efficiency of pure CO2 systems in basic architecture units, particularly in warm regions like India, remains a challenge. To address this, modern refrigeration systems must prioritize low energy consumption and high coefficient of performance (COP) while meeting environmental standards. This study investigates different operating conditions to determine the optimal parameter range for maximizing COP and improving the efficiency of conventional CO2 refrigeration configurations. It examines both subcritical and transcritical refrigeration cycles under varying parameters, emphasizing the importance of understanding COP’s relationship with factors such as subcooling, superheating, ambient temperature, and evaporator temperature. The study advises against superheating in CO2 systems but highlights the substantial COP increase with higher degrees of subcooling, leading to enhanced system performance. Additionally, it provides a comprehensive theoretical comparison between advanced pure CO2 supermarket applications and commonly used hydrofluorocarbons-based systems, offering insights into energy efficiency and environmental impacts for informed decision-making in the industry.

Enhancing Seasonal Performance of Heat Pumps integrated into Building Ventilation Systems using a Multi-Stage Volume Enlarger: a Comparative Study across European Regions

The buildings sector is one of the largest energy consumers in the EU, accounting for approximately 40% of final energy consumption and around 36% of greenhouse gas emissions. European governments are implementing various measures to reduce these figures. One effective approach to lowering energy consumption is to enhance the energy efficiency of HVAC systems in buildings. Extending the control range of heat pumps can significantly improve their seasonal energy efficiency, thereby reducing carbon dioxide emissions and enhancing building sustainability. Modern heat pump capacity control commonly involves a variable-speed compressor and an electronic expansion valve. In this study, the authors introduce an additional control component—variable volume in the active loop of the heat pump.The paper evaluates the performance of a variable-volume heat pump integrated into a ventilation system across different European regions (Vilnius, Helsinki, and Milan). A comparison is made between the conventional control approach, which uses a compressor and expansion valve, and an enhanced control method that incorporates an additional device to regulate the heat pump circuit volume. Based on data from prior experiments—specifically, the dependencies of the heat pump heat output and efficiency on compressor speed, expansion valve position, and circuit volume—a control algorithm was developed with Matlab to simulate heat pump performance in a ventilation system over a typical meteorological year for each city.Key findings highlight that the use of additional volume control in the heat pump loop significantly extends the unit’s operational time compared to conventional control methods. Specifically, operational time increased from several percent to as much as 69.97% across the regions analysed, positively impacting seasonal performance. These results underscore the critical importance of optimizing heat pump control strategies, as they not only enhance energy efficiency but also contribute to reducing reliance on auxiliary heating and lowering overall carbon emissions. Furthermore, despite these advantages, the study notes a significant limitation: the current lack of commercially available tools for implementing dynamic volume adjustment in heat pumps, which presents challenges for practical application in the field.

Exploring energy efficiency and savings potential of a horizontal domestic drain water heat recovery system in high-rise apartment buildings

In residential buildings, domestic hot water (DHW) used for showering and handwashing produces significant amounts of hot drain water (DW), which is typically wasted. This study proposes a horizontal drain water heat recovery (DDWHR) unit to capture waste heat from DW and improve overall DHW system efficiency with the focus on thermal exchange in a compact installation suitable for high-rise apartment buildings. Experiments under different operating conditions were conducted to evaluate the DDWHR unit’s thermal performance and energy-saving potential. Results showed that the proposed DDWHR unit achieved energy efficiency of 90–95%, depending on operating conditions, due to high heat recovery rates. In the entire DHW system, the DDWHR unit demonstrated approximately 15% heating energy savings compared to conventional DHW setups. Also, nationwide adoption of the DDWHR unit in two-person apartments could reduce gas costs by about 14% annually. The findings of this study indicate that the horizontal DDWHR unit can effectively promote sustainable DHW use in high-rise residential buildings and offers a promising solution for improving energy efficiency in DHW systems.

Experimental study of enhanced convection in mini-tube with jet chamber insert using infrared thermometry

Enhancing single-phase convection in mini-tubes is essential for improving the efficiency and compactness of heat exchangers. Conventional mini-tube inserts, such as twisted tapes and helical screws, suffer from limited fluid mixing and significant pressure drops. These limitations restrict their effectiveness in achieving high heat transfer efficiency, especially in compact systems where space and energy are constrained. To overcome these challenges, this study introduces a novel mini-tube insert design featuring linked jet chambers to promote adequate spatial fluid mixing and significantly boost convective heat transfer. Experimental results demonstrate that at a Reynolds number (Re) of 300, the new insert increases the Nusselt number (Nu) by 67 % over a tube without inserts. Infrared thermometry further reveals that this enhancement leads to a 15.1 °C reduction in average wall temperature. The performance evaluation criterion (PEC) for the jet chamber insert reaches 1.66 at Re = 300, representing an 18.5 % improvement compared to traditional helical screw inserts. Beyond heat transfer, the insert design also improves temperature uniformity along the flow direction and stabilizes the outlet fluid temperature, addressing critical performance metrics for practical applications. The findings highlight its potential to improve energy efficiency and thermal performance in systems where space and thermal management are crucial.

Assessment of photovoltaic system in existence of nanomaterial cooling flow

In this study, a photovoltaic (PV) system was enhanced through the combination of a cooling duct utilizing a nanofluid composed of water and Al₂O₃ nanoparticles, aimed at optimizing thermal regulation and improving electrical efficiency. A novel approach was introduced by systematically examining the effects of channel cross-sectional shapes and fin arrangements on heat dissipation. Using a single-phase simulation model, the thermal performance of the nanofluid was evaluated across various nanoparticle shapes, providing new insights into the relationship between geometry and nanofluid cooling efficacy. The results demonstrated that altering the cross-sectional shape generally reduced thermal performance, but strategic fin configurations significantly enhanced heat transfer. The optimal design, featuring eight shorter fins arranged around an eight-lobed pipe, resulted in a 4.3% improvement in thermal performance. Additionally, blade-shaped nanoparticles were identified as the most effective, enhancing heat absorption by 1.15% compared to pure water. This research presents the first combination of advanced nanofluid cooling with a detailed analysis of geometric factors (cross-section and fin design) in PV systems. The findings provide practical guidelines for improving heat management in PV cells, ultimately leading to increased electrical efficiency and an extended operational lifespan. These insights hold promising implications for the design of more efficient solar energy systems and could inform future thermal management solutions in renewable energy applications.

Optimized design and comparative analysis of double-glazed photovoltaic windows for enhanced light harvesting and energy efficiency in cold regions of China

This study investigates the daylighting performance and energy efficiency optimization strategies of double-glazed photovoltaic windows (DS-STPV) in cold regions of China. By conducting a comprehensive comparative analysis with traditional and energy-efficient window systems, this research aims to identify high-efficiency building solutions tailored to extreme climatic conditions. Amidst the escalating global energy demand and the pressing need for energy conservation and emission reduction, Building-Integrated Photovoltaic (BIPV) technology is increasingly recognized for its potential and value as a critical method for harnessing green energy. However, the widespread adoption of BIPV technology faces several challenges, including cost-effectiveness, conversion efficiency, system stability, and architectural aesthetic integration. Utilizing the T&A House from the 3rd International Solar Decathlon as an empirical case study, this research employs Ecotect and DesignBuilder simulation software to systematically evaluate the daylighting effect and energy performance of DS-STPV. The analysis considers various key design parameters, including photovoltaic cell coverage, window orientation, and window-to-wall ratio. Through refined modeling and multi-dimensional analysis, this study aims to identify the optimal design configurations of DS-STPV windows in cold regions, with the goal of simultaneously achieving superior natural lighting quality and significant building energy efficiency. The findings indicate that a south-facing DS-STPV window design with approximately 30% photovoltaic cell coverage and a window-to-wall ratio of 30% effectively balances daylighting requirements and energy efficiency in cold regions of China. This design strategy not only ensures an abundance of natural light in the room, but also significantly reduces the building’s energy consumption, proving the superior performance of DS-STPV windows in cold climates. In addition, the unique optical properties of DS-STPV windows reduce glare, further improving the overall quality of the indoor environment. In summary, this study provides a robust scientific foundation for the application of DS-STPV windows in cold regions, offering practical guidance and reference for optimizing energy efficiency and facilitating green transformation in future building design.

Performance improvements for green hydrogen-ammonia fueled SOFC hybrid system through dead-end anode recirculation and split transcritical CO2 power cycle

This paper proposes a novel green hydrogen-ammonia fueled solid oxide fuel cell (SOFC) hybrid power system by coupling dead-end anode recirculation with split transcritical CO2 power cycle (STCC). The STCC with dual-temperature heaters adopts split heat absorbing concept to recover cathode off-gas waste heat. The thermodynamic and economic performances of novel system are investigated and compared. Furthermore, the impacts of fuel ammonia mixing ratio, cell stack fuel utilization ratio, STCC CO2 split ratio, fuel price etc. on system performance are revealed. The results show that the introduction of STCC results in a 3.96% improvement in total system energy efficiency and a 0.6% reduction in total system levelized cost of electricity (LCOE) compared with standalone dead-end anode recirculated SOFC unit. The extremely high current density is not beneficial to enhance hybrid system thermo-economic performance. For every 0.1 increase in fuel ammonia mixing ratio, total system energy efficiency increases by 0.26∼0.85% and LCOE decreases by 4.6∼7.4%. The optimal STCC CO2 split ratio of recuperator declines with increasing fuel ammonia mixing ratio. Novel hydrogen-ammonia fueled hybrid system offers a high total energy efficiency of 0.7406, and its economic performance advantage over dead-end anode recirculated SOFC declines with decreasing fuel price.

Dynamic simulation of wind-powered alkaline water electrolysis system for hydrogen production

Alkaline water electrolysis (AWE) is a mature and cost-effective technology, especially suited for large-scale deployment, yet faces challenges in adapting to the dynamic nature of renewable energy sources. Evaluating AWE's adaptability to fluctuating renewable energy inputs is crucial. This study introduces a dynamic model to assess the influence of wind energy on a 250 kW industrial-scale AWE system for hydrogen production. This paper pioneers the utilization of Aspen Plus Dynamics for dynamic modeling, offering a comprehensive approach that incorporates all vital components and controllers of the balance of plant, such as gas-liquid separator, heat exchangers, deionized water supply, pumps, and the cooling loop. This methodology allows comprehensive simulation at the system level, revealing the real dynamic characteristics of the system under fluctuating wind energy conditions. Due to the absence of a dedicated module for AWE in Aspen Plus Dynamics, an integrated dynamic operation unit for the electrolyzer is constructed using Aspen Custom Modeler. The study analyzes the dynamic characteristics of the AWE system, specifically focusing on temperature, voltage, and liquid level. The study compares two temperature control strategies, before-stack and after-stack, with the refined after-stack method effectively addressing over-temperature issues and improving system energy efficiency by 1.44%.

IOT Based Parking Lot for Smart City

Abstract: This project presents an intelligent parking lot system using infrared sensors to detect available parking spaces in realtime. The system improves user convenience and reduces traffic congestion by providing accurate parking availability data. Infrared sensors, chosen for their reliability and low power consumption, are installed in each parking slot. The sensor data is processed centrally and shared via thingspeak website and digital displays. The system will be piloted in a section of the parking lot, with calibration ensuring accuracy. Results show reduced time searching for parking and decreased congestion. The system's scalability, energy efficiency, and real-time capabilities enhance user experience and optimize parking operations. Future developments include predictive analytics and expansion to other hightraffic areas.

Ultra-Low Power Circuit Design Techniques for Audio-Based Environmental Sensing in IoT Networks

Abstract: ULP circuit design consideration is critical in enhancing AS-based ESL in IoT networks essential in designing IoT devices to work with minimal power consumption. These designs enable the sensors to operate continuously interesting environments while at the same time utilizing methods like duty cycling, adaptive sampling, and wake-up circuitries. AFE parts help to minimize pre-ADC signal manipulation within the hardware and true and near-threshold processing, as well as subthreshold processing, decreases the power dissipation even more without affecting utility. Energy harvesting including, solar and piezoelectric handling ensures kinetic energy is accumulated for efficient functioning without batteries. Furthermore, incorporating lightweight machine learning (ML) models allows for audio classification and anomalous event detection on the network edge and with low data transfer. In combination, these developments bring more efficient and resource-saving IoT networks providing essential data for applications in environmental and climate change sensing, smart cities, public safety, and industrial security. This approach is essential when building IoT systems that are to last, to meet the increasing need for intelligent, self-sustaining, energy-efficient systems

A tri-level stochastic model for operational planning of microgrids with hydrogen refuelling station-integrated energy hubs

Energy hubs are efficient energy systems in which multiple energy carriers are converted, conditioned and stored to supply multiple forms of energy demands such as electricity, gas and heat. On the other hand, the penetration of fuel cell vehicles in transportation sector is increasing. The role of hydrogen refuelling stations is to inject hydrogen into fuel cell vehicles. A hydrogen refuelling station may absorb its required electricity from an energy hub. The operational planning of the microgrids with hydrogen refuelling station-integrated energy hubs has not been addressed before; therefore, the main goal of this research is to develop a hierarchical stochastic framework for operational planning of isolated microgrids with hydrogen refuelling station-integrated energy hubs, considering the uncertainties. In a hierarchical framework, the players are not obliged to submit their models to a central agent, so the privacy of players is preserved; moreover, it is computationally inexpensive. Mixed-integer linear programming models are used for hydrogen refuelling stations and energy hubs, while a mixed-integer quadratic programming model is used for modeling microgrid. CPLEX and GUROBI solvers are respectively used for solving the developed models. SCENRED module is used for scenario reduction. The studied microgrid is a renewable-rich 69-bus radial network. The findings approve the efficiency of the proposed methodology. The impact of batteries and wind generators on the operation of energy hubs has been evaluated.

Enhancing energy efficiency in MC-NOMA systems through optimized channel and power allocation

Non-orthogonal multiple access (NOMA) has quickly become popular due to its higher spectral efficiency (SE) and is crucial in extending future networks’ capacity. This paper presents an innovative approach to enhancing energy efficiency (EE) in downlink (DL) multi-carrier (MC) NOMA systems, in which a single base station (BS) supports a group of users across multiple sub-channels. A novel least user sum gain-based user assignment (LUSGUA) algorithm is proposed in this paper, which prioritizes users with the lowest channel gains for optimal sub-carrier allocation. Additionally, a novel power allocation (PA) scheme is developed across sub-carriers to further improve energy efficiency (EE), throughput, and fairness. throughput and fairness. Since the PA optimization problem (OP) is constrained and non-convex, to tackle this problem, a penalty approach (PTA) is proposed, which is then addressed by particle swarm optimization (PSO) with sequential optimization of the inter/intra-level PA. Power is allocated across sub-carriers at the inter-level using PSO, while at the intra-level, power is distributed among users via the Bisection Method (BM). Simulation results demonstrate that the proposed algorithm achieves significant enhancements in EE, with improvements ranging from 13.04% to 48.67% compared to existing resource allocation (RA) schemes techniques, while also improving system throughput, fairness, and outage percentage. These results highlight substantial advancements over traditional methods.