Energy Conversion Efficiency Research Articles (Page 1)

The increase in the temperature of photovoltaic (PV) cells is a critical factor that negatively affects the efficiency of converting solar radiation into electrical energy. This phenomenon not only reduces energy conversion efficiency but also causes damage to PV components, thereby preventing the achievement of the intended energy production goals. Moreover, the heating of PV modules has two significant impacts: first, a reduction in energy efficiency, and second, a decrease in the lifespan of the solar cells. Therefore, projects aimed at producing clean electrical energy using PV solar panels must consider the study of installation sites for PV solar plants and the impact of environmental conditions on panel performance. Given that an increase in PV cell temperature reduces their productivity, this study examines the impact of ambient temperature on the maximum temperature reached by a PV solar panel and analyzes the results. The results show that installing solar panels in harsh environments characterized by high temperatures, such as Ouarzazate in Morocco, can cause these panels to reach critical temperature thresholds of up to 115°C under high solar flux, which can lead to solar system failure and thus the failure of the entire project. In addition, the heating of photovoltaic modules has two major impacts: firstly, energy efficiency is reduced by around 0.44% for every 1°C increase, and overall efficiency is reduced from 16% to less than 10% under extreme conditions; secondly, solar cell life is shortened. Finally, this study highlights the importance of carrying out thorough climatic and environmental assessments before establishing solar photovoltaic power plants. It also highlights the importance of employing high-performance cooling systems or innovative technologies to reduce the impact of heat on photovoltaic panels. This approach is essential to ensure the longevity and efficiency of solar photovoltaic installations, and to achieve our ambitions for sustainable, green energy production.

Abstract This paper focuses on the expansion train designed for the Compressed Air Energy Storage (CAES) concept under development in the EU-funded ASTERIx-CAESar project. The system integrates concentrated solar thermal energy from a high-temperature (800°C) volumetric central-receiver into a hybrid storage configuration, combining Low-Temperature Thermal Energy Storage (LT-TES) with Compressed Air Storage (CAS) and High-Temperature Thermal Energy Storage (HT-TES). Electricity from the grid powers compressors during low-price periods, storing compressed air and recovering compression heat in LT-TES. Solar heat is stored in HT-TES. During discharge, preheaters and reheaters supply stored energy to the expansion train. Residual energy in the exhaust of the low-pressure turbine reduces round-trip efficiency; therefore, a bottoming Waste Heat Recovery (WHR) unit based on Organic Rankine Cycle (ORC) technology is assessed. Multiple air-cooled configurations are modelled for Expander Exit Temperatures (EET) of 300-600°C, using organic fluids and steam in subcritical, transcritical and supercritical layouts. Scale effects on expander type (screw or axial) and isentropic efficiency are considered for capacities from 1 to 100 MWe. A multi-objective optimisation of the bottoming cycle considers technical and economic aspects to maximise efficiency and heat recovery by adjusting vapour generator pressure/temperature. A global optimisation of the expansion train identifies the optimal cycle configuration for each EET and scale, integrating the WHR system with a two-stage turbine. Recommendations to improve CAES system efficiency are provided.

Conversion-type transition-metal fluoride cathodes, renowned for their multielectron redox capacity, hold great promise for next-generation high-energy-density rechargeable batteries. However, their practical implementation has historically been hampered by the large overpotentials that deviate from the intrinsic voltage profiles, resulting in severe voltage hysteresis and ultralow round-trip efficiency of the battery. Herein, we demonstrate a sulfur-mediated dynamic charge redistribution strategy that unlocks the near-theoretical voltage plateaus of 2.73 V for the FeF3 cathode, achieving a remarkable enhancement in the energy efficiency from 71.9% to 81.9%. The intrinsically multivalent nature of sulfur enables dynamic charge redistribution at the sulfur-fluoride interface during electrochemical charge/discharge, significantly enhancing lithium diffusion kinetics while constructing M-F-S intermediate states to mitigate phase and valence state heterogeneity on the surface of fluoride active particles. This synergistic mechanism substantially improves the reversibility of the conversion reactions. Extensive validation across diverse metal fluorides (e.g., CuF2, FeF2, CoF2, NiF2, MnF3, and CrF3) demonstrates the universality of this approach for mitigating voltage hysteresis in conversion-type fluoride cathodes, paving a critical advancement toward their practical deployment.

This research examines mixed convection phenomena in stagnation point flow of a Casson hybrid nanofluid, exploring the synergistic effects of magnetic fields and thermal source/sink configurations. The study employs a water-based nanofluid system enhanced with copper (Cu) and aluminum oxide (Al2O3) nanoparticles flowing adjacent to a vertical surface. Using numerical methods with MATLAB’s shooting technique, we develop and solve a mathematical model that captures the complex interplay between electromagnetic forces and thermal gradients. The investigation advances current knowledge by simultaneously analyzing magnetic and thermal in fluences on hybrid nanofluid behavior, an underexplored area in contemporary research. Critical performance metrics such as velocity profiles, thermal distributions, skin friction, and Nusselt numbers are systematically evaluated. Results indicate that the hybrid nanofluid configuration achieves substantially improved thermal conductivity (up to 18% enhancement) compared to conventional fluids, with particular relevance to affordable and clean energy through optimized heat exchanger applications. The analysis of boundary layer dynamics provides fundamental insights into transport mechanisms, supporting Industry, Innovation and Infrastructure by informing next generation thermal management solutions. These findings offer significant potential for advancing energy-efficient technologies in power generation and industrial cooling systems, contributing to both responsible consumption and production through improved energy conversion efficiency.

Climate change is projected to increase environmental humidity in northern latitudes, yet its effects on tree hydraulics remain underexplored. We investigated how elevated air relative humidity and increased soil moisture influence water relations, gas exchange, and aquaporin (AQP) expression in silver birch (Betula pendula) at the free air humidity manipulation experiment. We applied air humidification and soil irrigation treatments and measured leaf hydraulic conductance, gas exchange parameters, and AQP transcript levels in leaves to assess physiological and molecular responses. Both treatments significantly decreased leaf hydraulic efficiency, that is the capacity of leaves to transfer water in liquid phase. However, AQP expression responded divergently: air humidification downregulated most AQP transcripts, whereas soil irrigation upregulated them. Despite these changes, gas exchange remained stable, but stomatal sensitivity to vapour pressure deficit declined under both treatments. Our findings suggest distinct regulatory mechanisms of AQPs in response to atmospheric vs edaphic moisture, while resulting in convergent physiological outcomes. The reduced stomatal sensitivity and decoupling between hydraulic performance and photosynthetic activity under nonstress conditions indicates a shift in water-use strategies and highlights the pronounced hydraulic plasticity of B. pendula. These results have implications for predicting tree and forest resilience under future climate scenarios, where increasing humidity may compromise hydraulic safety and water-use regulation during extreme weather events.

Introduction Exploring the variation in plant functional traits from different perspectives not only helps to reveal how plants adapt to their environment but also reflects their ecological strategies. This study investigated the differences in trait variability across different life history stages and how these differences affect the net photosynthetic rate of trees. Methods The research measured photosynthetic traits, hydraulic traits, leaf morphological traits, and leaf stoichiometry at various life history stages, exploring the variation and coordination among functional traits at different stages. Results Results showed that (1) the sapwood specific hydraulic conductivity and leaf specific hydraulic conductivity exhibited the highest variability among all traits, while carbon and phosphorus content had the lowest variability. (2) Intraspecific trait variation accounted for a significant portion of the total variance, indicating extensive plasticity in ecological strategies and environmental adaptability among individuals of the same species. (3) Regarding different life history stages, small trees surpassed mature trees in several physiological indicators, including higher leaf specific hydraulic conductivity, sapwood specific hydraulic conductivity, whole-branch hydraulic conductivity, and contents of carbon, nitrogen, and phosphorus. (4) As trees grew, both net photosynthetic rate and hydraulic efficiency tended to decline, with a weakened synergy between them, suggesting that water and nutrient transport efficiency are key factors limiting tree growth. Discussion In summary, our findings emphasize the importance of water transport efficiency in photosynthesis and reveal the coordinated relationship between water transport and net photosynthetic efficiency across different life history stages of trees. These findings provide new insights into how trees adjust their functional traits to respond to environmental stress during their growth and have important implications for maintaining productivity and balancing biodiversity in forest ecosystems.

Aiming at the limitations of direct drive wave energy conversion (DD-WEC), especially the poor power density, low energy conversion efficiency, and a large volume of linear generators (LGs), a novel magnetic helix hybrid excitation rotary generator (MH-HERG) with the higher power density and higher energy conversion efficiency is proposed. The proposed MH-HERG can convert linear motion into rotary motion without contact with a hybrid excitation magnetic screw (HEMS) unit, so it has high energy conversion efficiency. Furthermore, a new quasi-Halbach magnetization array is used in the proposed MH-HERG to increase its power density and allows a hybrid excitation method to be used to make the thrust adjustable to further improve power density. The analytical solution model is established to derive the calculation equations of air gap flux density, which are validated through the finite element simulation. Arc-shaped permanent magnets (PMs), instead of tile-type PMs, are designed to weaken cogging torque and harmonic content in proposed MH-HERG’s no-load back electromotive force (back-EMF), thereby improving output power quality. Finally, the prototype is built and an experiment is conducted to ascertain the effectiveness and superiority of the proposed MH-HERG which has increased power density by 4.4 times and energy conversion efficiency by 3 times compared to existing LGs.

ConspectusPhotoelectrochemical (PEC) systems are among the most promising solar-to-electrochemical energy conversion and storage technologies and are uniquely positioned to address global energy demand and environmental sustainability. Mimicking the essential functions of natural photosynthesis, including light harvesting, catalytic water oxidation, CO2 reduction, and energy storage, requires materials that integrate efficient photon capture with rapid charge transport and robust catalytic activity. However, conventional photoelectrochemical materials are limited by the incomplete utilization of the solar spectrum and rapid charge recombination, leading to a narrowed redox potential window and compromised overall conversion efficiency. In this context, organic molecular PEC materials offer distinct advantages through their tunable, well-defined structures, enabling precise control over their electronic properties, redox behavior, and broad-spectrum light utilization. Integrating electron donor-acceptor (D-A) frameworks with redox-active or catalytic units into porous assemblies establishes spatially organized pathways for charge separation and catalytic transformation, although such a molecular-level design remains in its early stages. The central challenge lies in translating these structure-function insights into design principles that deliver multifunctional materials capable of controlled charge modulation, long-range electron transfer, and adaptive catalysis, thereby advancing the realization of complete artificial photosynthesis.In this Account, we begin with decoding PEC systems through the design principles of molecular materials, emphasizing how molecular-level modifications influence key performance metrics. The main concept of developing molecular materials through molecular engineering for artificial photosynthesis, centered on PEC energy conversion and storage, is presented in this Account. It focuses on the state-of-the-art construction of efficient D-A structures by tuning functional groups and incorporating single and dual metals, with charge dynamics regulated by thermodynamic and kinetic processes. Advances and challenges in molecular engineering are highlighted, emphasizing that designing efficient D-A architectures requires the appropriate selection of molecular functional groups, tailored structures, and optimized properties, which are crucial for regulating long-lived charge separation states and driving diverse redox reactions in PEC systems. We outline best practices for designing and assembling coupled D-A architectures, highlighting our research contributions and the broader progress in solar-to-electrochemical energy conversion and storage during the past decade. The discussion further explores coupled/decoupled strategies, which offer solutions to challenges associated with solar-driven CO2 splitting (for CO and O2 generation), N2 reduction (for NH3 synthesis), and organic molecular-level energy storage devices (solar batteries), and is extended to perspectives on sustainable development. Taken together, we anticipate that this Account will outline emerging strategies for integrating multifunctionality into PEC molecular assemblies, providing valuable design insights for adaptable materials that enhance solar-to-electrochemical energy conversion and storage efficiency.

ABSTRACT The optical Vernier effect significantly improves sensitivity and resolution in fiber‐optic sensors, especially in Fabry–Pérot interferometers (FPIs). This study presents a novel mode Vernier photothermal spectroscopy (MV‐PTS) based on a dual‐mode anti‐resonant Bragg hollow‐core fiber (BHCF), which is spliced with a single‐mode fiber and a suspended core fiber (SCF) to construct an FPI. The dual‐mode configuration facilitates the mode Vernier effect (MVE) within a single FPI, enhancing the sensitivity of photothermal phase demodulation. Eccentric splicing of the BHCF and SCF enables regulation of the dual‐mode energy ratio to enhance the MVE, while constructing a natural gas channel to support direct trace gas detection. Monitoring the phase difference of the modes minimizes common‐mode noise, leading to a high signal‐to‐noise ratio of the photothermal signal. The excitation and demodulation processes occur within a compact 0.8 nL hollow core, improving energy conversion efficiency. The 1 mm‐long BHCF‐based F‐P cavity achieves a minimum detection limit of 12 parts per billion (ppb) for acetylene gas, demonstrating rapid responsiveness and long‐term stability. This compact sensor design overcomes challenges in achieving ultrasensitive gas detection with minimal light‐matter interaction length in intrinsic fiber structures, offering promising applications in gas sensing.

Enhancing the energy conversion efficiency of fuel cells necessitates optimization of oxygen reduction reaction (ORR) under high-voltage conditions through improved Pt catalysis. This study introduces an electrocatalyst that uniformly anchors a high loading (40 wt%) of small Pt nanoparticles (3.2nm) on a novel support: tellurium and nitrogen co-mediated graphitized mesoporous carbon (Te-N-GMC). The strong metal-support interactions arise from Pt─Te and Pt─N bonds. Density functional theory (DFT) calculations and operando X-ray absorption spectroscopy reveal that Te-N co-mediation enhances the high-voltage oxidation resistance of Pt via electron reverse transfer from the Te-N-GMC support to Pt. Consequently, the Pt valence state in Pt/Te-N-GMC increases by only +0.085 from open-circuit potential to 1.5V, resulting in exceptional durability over 100000 high-voltage cycles (1-1.5V) with negligible morphological aggregation. Moreover, the Te-N-GMC support effectively lowers the energy barrier of the rate-determining step, enabling Pt/Te-N-GMC to achieve outstanding activity (0.7V at 1.26 A cm-2 under H2-air conditions). This translates to an 18.6% increase in electrical efficiency compared with commercial Pt/C at the same output power density. These findings demonstrate the potential of Te-N-GMC as a robust cocatalyst for high-voltage ORR and highlight a promising strategy for enhancing Pt catalysis for high-efficiency fuel cells.

Adzuki bean ( Vigna angularis L.) is a characteristic economic crop with ecological adaptability and industrial potential. During crop production and cultivation, regulating light quality through photo-selective nets or films has become an important environmental control strategy for optimizing their yield and quality. This experiment studied the effects of different color photo-selective nets (red photo-selective net, RN; blue, BN; yellow, YN; green, GN; natural light, CK) on the yield, quality, agronomic traits, photosynthetic characteristics and antioxidant capacity of adzuki beans. The results demonstrate that, compared with CK, RN treatment significantly increased plant height (12.23%) and total dry weight (18.04%), while BN treatment significantly enhanced stem diameter (8.15%), root dry weight (21.62%) and root-shoot ratio (23.53%). RN and BN treatments both optimized the anatomical structure of leaves, showing that palisade tissue and spongy tissue increased significantly by 8.68%, 49.74% and 21.01%, 66.96% respectively compared with CK. This is possibly related to the increased net photosynthetic rate (RN: 23.18% and BN: 14.44% higher than CK) and stomatal conductance (RN: 15.82% and BN: 21.65% higher than CK) to minimize photosynthetic “noon break” depression, and ultimately enhancing the light energy conversion efficiency and actual light energy capture efficiency of the PSII reaction center. Under both RN and BN treatments, the activities of antioxidant enzymes (SOD, POD, CAT) were enhanced to suppress reactive oxygen species (ROS) accumulation; Meanwhile, the malondialdehyde (MDA) content was correspondingly reduced by 11.62% and 39.08% compared to CK. Crucially, RN treatment significantly enhanced the yield of adzuki beans (15.05%), starch content (4.69%), and total phenol content (20.00%) compared to CK. BN treatment substantially increased yield (10.63%), soluble protein content (7.69%), amino acid content (9.55%), and total flavonoid content (38.05%). Under GN treatment, although the yield of adzuki beans decreased (8.56%) and the net photosynthetic rate reduced (2.25%), the total flavonoid content of adzuki beans significantly increased by 51.21%. In conclusion, the red and blue light treatments enhance both photosynthetic capacity and yield and improve quality traits in adzuki beans, offering novel insights into optimizing light environments in cultivating specialized legume varieties.

Wave energy converters (WEC), as alternative power sources for marine equipment, play a crucial role in promoting the development and utilization of ocean resources. However, the harsh marine environment and the low-frequency nature of ocean waves pose substantial challenges to the lifespan and energy conversion efficiency of WECs. This paper proposes a pull-out mooring wave energy converter (POM-WEC) integrating a high-performance electromagnetic power take-off (EPTO) system. The EPTO system can convert the low-frequency and low-speed wave excitation into high-speed inertial rotational motion of the rotor. Under an excitation velocity of 0.5 m s-1, the EPTO system achieves an average output power of 9.1mW. A comprehensive methodology based on response amplitude operators and Cummins equations is developed to analyze and predict the motion response of the POM-WEC under various wave conditions. By comparing the numerical simulation with experimental data, the validity and applicability of the methodology are further verified. The influences of wave height and frequency on both the motion response of the POM-WEC and the output performance of the EPTO system are also systematically tested and evaluated. Furthermore, a self-powered wireless sensing node based on the POM-WEC is successfully developed, featuring non-volatile data storage and three distinct operation modes.

Abstract Energy scarcity and electromagnetic microwave (EMW) management pose global challenges, yet integrating functionalities in a single material to manage ultrawide‐spectrum radiative energy from visible to microwave remains formidable. Here, sustainable yet appropriate cellulose and cellulose nanofibers (CNFs) are utilized to integrate silver nanowires and transition metal carbides, consequently yielding the large‐area, ultrathin, high‐strength, ultra‐flexible, and durable paper‐based window films toward advanced ultrawide‐spectrum heating and EMW attenuation. The ultrawide‐spectrum‐selective films demonstrate high visible light transmittance, near‐infrared photothermal conversion, mid‐infrared low emissivity‐induced passive radiative heating, and effective EMW attenuation, simultaneously elevating energy conversion efficiency and EMW management. Under a solar power density of 50 mW cm − 2 , a CAMC‐equipped room with dimensions of 30 × 20 × 18 cm 3 exhibits a temperature increase of 9.4 °C, outperforming other heating materials of identical dimensions and initial temperatures. Furthermore, they offer an adjustable range of optical transmittance and EMW shielding effectiveness (SE), with a thickness‐normalized specific SE ranging from 937 to 2562 dB mm −1 and transmittance between 80.3% and 55.1%, surpassing the reported materials.

ABSTRACT Greece’s path toward climate neutrality, aligned with the European Green Deal and REPowerEU strategies, relies on the rapid expansion of renewable energy sources combined with the development of energy storage capacity to ensure system resilience and reduce dependence on natural gas. This study uses the LEAP-NEMO model to assess the role of seasonal hydrogen storage in achieving national energy and climate targets. The results confirm that hydrogen storage allows for a higher penetration of renewable energy sources, thereby reducing curtailments and contributing to the early phasing out of natural gas from the country’s energy mix. However, its low round-trip efficiency and limited short-term response make it unsuitable for short-term balancing, highlighting the need for complementary storage technologies. Furthermore, reduced dependence on gas imports enhances energy security, allowing Greece to meet demand with competitive domestic resources, mitigating exposure to the high volatility of global market. The novelty of this work lies in the updated analysis of the Greek electricity system through an energy model framework, applied for the first time in the country, and in the demonstration of the role of hydrogen as a factor for the future scaling-up of renewable energy sources.

Sideslip maneuverability is a critical future requirement for hypersonic airbreathing vehicles. One of the main challenges is maintaining inlet performance under not only non-uniform inflow (NUF) but also varying inflow angles. This study systematically investigates the aerodynamic performance, sensitivity, and underlying flow mechanisms of four vector adaptive inward-turning inlets (VAIs) under angle of sideslip (AOS) conditions. In contrast to classical design methods, this study utilizes an originally developed methodology that integrates osculating flow theory and multi-objective optimization. A key advantage of this approach is its ability to design inlets for arbitrary NUFs. In this work, this method is applied to generate configurations for several representative NUFs. A high level of flow properties is achieved for all VAIs within AOS −3° to 3° (σex ≥ 0.534, φ ≥ 97.6%, and ηKE ≥ 0.966). A lateral flow mechanism is identified: as AOS increases, the lateral velocity component intensifies, leading to a significantly asymmetric flow structure. This evolution results in increased distortion and a gradual migration of low-kinetic flow in both circumferential and spatial directions, thereby reducing flow capture and energy conversion efficiency, while enhancing compressive capability. The findings provide critical insight into the lateral adaptability of such inlets, which is essential for designing maneuverable hypersonic vehicles.

Ambient state effects on energy conversion efficiency: Multilevel analysis of thermodynamic cycle performance in two-stroke aviation engines

Sandwich-structured piezoelectric ultrasound harvester for wireless power charging of implantable biomedical electronics.

Valorization techniques for biomass waste in energy Generation: A systematic review.

Bioinspired PVA/CS/WPU@c-MWCNTs aerogel for concurrent highly efficient freshwater generation and hydrovoltaic power production.

To enhance both the hydraulic efficiency and noise performance of a hot water circulation pump, key design variables were identified using the Plackett–Burman experimental design. These variables include the impeller outlet width, blade wrapping angle, and volute base circle diameter, which significantly influence the pump’s performance. A database of 60 optimization samples was generated through the Latin hypercube sampling method, enabling the development of predictive models using eXtreme Gradient Boosting (XGBoost), back propagation neural network, and least absolute shrinkage and selection operator algorithms. Among them, XGBoost demonstrated superior accuracy in predicting the pump’s performance. For optimization, non-dominated sorting genetic algorithm III was employed, yielding an optimal configuration with parameters D3 = 429 mm, φ = 119°, and b2 = 36.9 mm. Compared to the original model, this optimized pump performs better hydraulically over the flow range from 0.8Q to 1.2Q, which achieves a reduction in entropy production by 5.32% in the impeller and 3.33% in the volute. Noise levels also improved substantially after optimization. The high sound power region near the blade working surface disappeared, and the total sound pressure level decreased by 3.02 dB.