Average Energy Efficiency Research Articles

Scenarios for energy transition in public transport

The growing global demand for new energy sources and innovative technologies is driven by environmental concerns and the need to address the worldwide energy crisis. The Paris Climate Agreement, also known as the United Nations Climate Change Conference Paris 2015 (COP21), has compelled nations to explore cleaner, more sustainable, and carbon-neutral technologies and products. This commitment was reaffirmed at the 2021 Climate Change Conference (COP26) in Ireland. This study seeks to determine whether the global shift in transportation models from combustion to electric traction holds promise for achieving the Sustainable Development Goals (SDGs) in the Brazilian context, thereby contributing to climate change mitigation. To investigate this, a quantitative field research approach was employed, accompanied by relevant literature references. Key indicators, including urban bus routes in Cascavel, Paraná, Brazil, their average mileage, emissions, and energy efficiency, were examined in comparison to electric buses. The research applied the Life Cycle principle, known as "Well to Wheels," to assess emissions in relation to the bus's propulsion system and energy sources. The findings revealed a remarkable 97.19% reduction in emissions (in gCO2eq/km) when using electricity from the predominantly renewable Brazilian electricity grid. Additionally, a 98.37% reduction in emissions (in gCO2eq/km) was observed when a photovoltaic system served as the energy source. These results underscore the sustainable potential of such systems in addressing the urgent global climate crisis.

Assessing energy efficiency and its dynamic changes in the water sector integrating heterogeneity and carbon emissions

Enhancing the energy performance of water utilities is a critical step towards achieving a net-zero carbon industry. Traditional energy performance assessments in the water industry often overlook heterogeneity among water companies and fail to account for changes in energy efficiency (EE) over time. To address these shortcomings, this research employs Stochastic Frontier Analysis (SFA) techniques to assess energy performance of two types of water companies such as Water and Sewerage Companies (WaSCs) and Water-only Companies (WoCs) within a single energy frontier model. Empirical analysis of water companies in England and Wales reveals an average EE score of 0.940 over the 2010–2020 period, suggesting a 6% energy-saving potential. English and Welsh water industry exhibited an overall 0.3% annual improvement in energy productivity change (EPC). This improvement was primarily attributed to efficiency changes (average 1.005), which offset the negative shift in technology change (average 0.998), while the scale effect remained negligible (average 1.000). WaSCs experienced a slight increase in EPC, with an average value of 1.018, indicating an improvement in energy productivity. In contrast, WoCs exhibited a decrease in EPC, with an average value of 0.989, suggesting a decline in energy productivity. These disparities were due to opposite shifts in the efficient production frontier; WaSCs had a positive shift (average 1.012), while WoCs had a negative shift (average 0.984). The study also highlights the impact of regulatory policies on energy performance. The 2009 price review involved modest improvements (average EPC = 1.013), while the 2014 price review yielded unfavorable results (average EPC = 0.993), emphasizing the need for long-term policies to facilitate sector-wide transformation towards carbon neutrality.

Energy contribution and loss of greenhouse-type drying chamber in multi-energy drying system: Heat distribution and exergy efficiency

In this paper, the relationship between the structural design of the greenhouse drying chamber and energy contribution and loss is discussed from the perspective of energy saving and system performance, and the rationality of their design is analyzed based on the exergy efficiency. Taking the multi-energy drying system of kelp as an example, the airflow and temperature distributions of different greenhouse-type drying chambers were simulated and optimized by using the computational fluid dynamics (CFD) method, and the heat transfer and loss were analyzed. The results show that the optimized drying chamber has an increase of about 40 % in The results show that the optimized drying chamber has an increase of about 40 % in exergy efficiency and a reduction of about 37 % in exergy damage. The average energy efficiency of the greenhouse-type drying chamber was more than 80 % with a size of 5000 × 2500 × 2300 mm, a tilt angle of 22.5°, and fans of 7. In addition, the energy efficiency was negatively correlated with the temperature difference between the inlet and outlet and positively correlated with the ambient temperature. Despite the heat loss in the drying chamber, its contribution to the system's overall energy efficiency is significant.

Investigation of modified deep eutectic solvent for high performance vanadium redox flow battery

Amidst the growing need for sustainable energy solutions, the vanadium redox flow battery (VRFB) emerges as a promising technology for large-scale grid energy storage. Compared to conventional aqueous electrolyte system, deep eutectic solvents (DES) have the potential to be considered as the smart electrolyte system for VRFB, owing to its exceptional features such as broad electrochemical window, facile synthesis, low vapor pressure, and economically viable. Unfortunately, original DES have inherently low ionic conductivity and high viscosity, limiting their applicability in flow batteries. To address this issue, we propose deep eutectic solvent (DES)-based vanadium electrolytes containing an optimal amount of aqueous acid and dispersed sulfonated multi-walled carbon nanotubes (sMWCNT) in a 1:6 choline chloride:ethylene glycol mixture (Eu-sMWCNT VIII/VIV) and in detail, evaluate the performance of a single-cell VRFB using this electrolyte. In this work, it is demonstrated that DES electrolyte can be made more conducting and less viscous with subtle modifications. The prepared electrolyte exhibits excellent electrochemical properties, showcasing high-capacity retention (90.0 % over 400 charge/discharge cycles at an applied current density of 30 mA cm-2) and efficiencies (average Coulombic and energy efficiencies of 84.0 % and 70.0 % over 400 cycles, respectively). This modified DES system holds potential as the future electrolyte for various flow battery technologies, enabling operation at higher applied current densities compared to reported DES-based flow batteries.

Simulation of a Tidal Current-Powered Freshwater and Energy Supply System for Sustainable Island Development

Sustainable development of islands cannot be achieved without the use of renewable energy to address energy and freshwater supply issues. Utilizing the widely distributed tidal current energy in island regions can enhance local energy and water supply security. To achieve economic and operational efficiency, it is crucial to fully account for the unique periodicity and intermittency of tidal current energy. In this study, a tidal current-powered freshwater and energy supply system is proposed. The marine current turbine adopts a direct-drive configuration and will be able to directly transfer the power of the turbine rotation to the seawater pump to improve the energy efficiency. Additionally, the system incorporates batteries for short-term energy storage, aimed at increasing the capacity factor of the electrolyzer. A simulation is conducted using measured inflow velocity data from a full 12 h tidal cycle. The results show that the turbine’s average power coefficient reaches 0.434, the electrolyzer’s average energy efficiency is 60.9%, the capacity factor is 70.1%, and the desalination system’s average specific energy consumption is 6.175 kWh/m3. The feasibility of the system design has been validated.

Quasi-Homogeneous Bromine Phase in Zinc-Bromine Batteries with Advanced Energy Efficiency and Energy Density

Regarding energy density, kinetics, and reversibility, the zinc-bromine batteries (ZBBs) exhibit advantages comparable to the conventional metal hydride nickel batteries as aqueous systems. However, the development of ZBBs has been impeded by two critical challenges: the self-discharge of Br-Br species cross-over and the short circuit caused by zinc dendrites. Achieving high energy density necessitates a large areal capacity electrode and tight battery assembly, which introduces additional hurdles. Addressing these challenges, we have successfully implemented a novel quasi-homogeneous bromine phase. Our optimized approach has realized ZBBs with a remarkable energy efficiency (EE) of 92.7% based on an areal capacity of 12 mA h cm−2 in a period duration of 13 h, an energy density of whole battery (EDB) of 80 W h l−1 with average EE of 92.5% for an extended cycle life of approximately 500 cycles, and a maximum EDB of 186 W h l−1 without pre-added zinc metal. This innovative work holds practical significance for developing ZBBs and providing insights and solutions to critical challenges.

Performance evaluation of solar-assisted humidification dehumidification system for seawater desalination: An experimental approach

Humidification/dehumidification desalination presents a promising method for small-scale water production due to its ability to utilize solar energy and minimal technological requirements. This research examines the performance of solar-assisted humidification/dehumidification (SA-HDH) desalination system, which is designed to treat seawater from Dumas Beach in Surat city of India. The system integrates a solar air heater, a packed humidifier, and a dehumidifier with an indirect evaporative cooler. Through comprehensive energy, exergy, sustainability, and economic assessments, the study aims to assess system efficiency and viability. Results demonstrate that increasing airflow rates significantly enhances heat transfer efficiency within the humidifier and dehumidifier, boosting system performance and increasing yield by 5.4–7.7 %. The average energy efficiency of 35.5 % is observed at an airflow rate of 125 kg/h. The system effectively removed 99.7 % of total dissolved solids, total hardness, and chloride from the seawater, producing high-quality freshwater. The cost of water production ranging from 0.025 to 0.028 $/L, with a sustainability index ranging from 1.052 to 1.064. These findings underscore the SA-HDH system’s potential as an efficient, sustainable, and cost-effective solution for mitigating water scarcity.

High-throughput systolic array-based accelerator for hybrid transformer-CNN networks

In this era of Transformers enjoying remarkable success, Convolutional Neural Networks (CNNs) remain highly relevant and useful. Indeed, hybrid Transformer-CNN network architectures, which combine the benefits of both approaches, have achieved impressive results. Vision Transformer (ViT) is a significant neural network architecture that features a convolutional layer as its first layer, primarily built on the transformer framework. However, owing to the distinct computation patterns inherent in attention and convolution, existing hardware accelerators for these two models are typically designed separately and lack a unified approach toward accelerating both models efficiently. In this paper, we present a dedicated accelerator on a field-programmable gate array (FPGA) platform. The accelerator, which integrates a configurable three-dimensional systolic array, is specifically designed to accelerate the inferential capabilities of hybrid Transformer-CNN networks. The Convolution and Transformer computations can be mapped to a systolic array by unifying these operations for matrix multiplication. Softmax and LayerNorm which are frequently used in hybrid Transformer-CNN networks were also implemented on FPGA boards. The accelerator achieved high performance with a peak throughput of 722 GOP/s at an average energy efficiency of 53 GOPS/W. Its respective computation latencies were 51.3 ms, 18.1 ms, and 6.8 ms for ViT-Base, ViT-Small, and ViT-Tiny. The accelerator provided a 12× improvement in energy efficiency compared to the CPU, a 2.3× improvement compared to the GPU, and a 1.5× to 2× improvement compared to existing accelerators regarding speed and energy efficiency.

Comparative study on productivity of double slope solar still using different wick and energy storage materials

The aim of the proposed study is to evaluate the efficiency of Double Slope Solar Still (DSS) using different wick and energy storage materials. In the study, wick materials such as jute, cotton and sponge were used in combination with energy storage materials such as mild steel, cast iron and copper. The experiments were conducted using DSS with different combinations of wick and energy storage materials to determine the efficient performance combination. The results show that sponge and copper have higher efficiency with wicks and energy storage materials. The results show that the maximum amount of water produced in a single day was 3147 ml when the DSS system was used with a combination of sponge and copper materials. This range shows an increase of 17.47 % and 12.44 % over the DSS with jute and copper and the DSS with the combination of cotton and copper respectively. The DSS showed the highest average energy efficiency when used in conjunction with a combination of sponge and copper, namely 51 % of the average efficiency. This corresponds to an increase of 18.60 % and 10.86 % compared to the combination of DSS with jute and copper and the combination of DSS with cotton and copper respectively. The best evaporation heat transfer coefficient of 345 W/m2K was determined for the combination of DSS with sponge and copper. Average exergy efficiency is also maximum of 3.076 % for the DSS with sponge and copper materials, which is higher than other investigated combinations. The proposed system has an energy payback period of 1.26 years, an energy production factor of 0.78, a life cycle efficiency of 6.9 % and a cost of $0.031 per litre of water produced in the environmental economic analysis.

Long-term operational characteristics of subway source heat pump system under various tunnel internal heat source intensities

In recent years, subway systems have effectively alleviated urban traffic congestions. However, thermal pollution of underground spaces is a prevailing problem, which poses a serious threat to the safe and efficient operation of subways. The subway source heat pump system (SSHPS), equipped with a front-end tunnel lining heat exchanger, is an effective solution to tackle the aforementioned problem. However, the design methodology and operational strategy of the system is not yet established, which necessitates an analysis of its long-term operational characteristics. In this study, an SSHPS simulation model was developed using the TRNSYS simulation tool based on a demonstration project and the model was subsequently validated against measured data. The validated model was used to evaluate the long-term performance and operational characteristics of the subway system under various internal heat source intensities ranging from 0 W/m to 240 W/m. The simulation results showed that the tunnel air temperature steadily increased as the internal heat source intensity increased. When the internal heat source was 0 W/m, the average annual decrease in tunnel air temperature was 0.11 °C. However, the average annual tunnel air temperature did not fall below the minimum subway design specification temperature of 5 °C at any point in time. When the internal heat source was 120, 180, and 240 W/m, the tunnel air temperature exceeded the maximum temperature of 40 °C stipulated in subway design guidelines on multiple occasions. As the internal heat source intensity increased, the performance of both the heat pump unit and SSHPS progressively decreased during the cooling season and gradually increased during the heating season. The runtime of the heat pump unit gradually decreased from 92.72 % to 77.57 % during the cooling season, whereas it increased from 46.92 % to 89.41 % during the heating season. The heat pump unit exhibited an average energy efficiency ratio (EER) of 5.07, 4.95, 4.87, 4.80 and 4.76 whereas the SSHPS demonstrated an average EER of 3.04, 3.01, 3.00, 2.99 and 2.98. Throughout its operational years, the SSHPS consistently maintained stable and cyclically high performance. However, the system did not fully meet the specified cooling and heating loads under all operational conditions, indicating that there was a source–load mismatch issue within the system. Hence, it is recommended to incorporate auxiliary cold and heat sources, thereby establishing a composite heating and cooling system based on subway source heat pump technology, with the aim of enhancing the reliability of energy supply for the system. This study can serve as a valuable reference for formulating high-efficiency and energy-saving operational strategies for SSHPSs.

Stabilizing zinc anodes for dual-membrane Zn-Ce redox flow battery via constructing zincophilic protective layer

The development of large-scale grid storage systems has increased interest in redox flow batteries due to their flexible design characteristics, which can help overcome the intermittency of renewable energy. Zn-Ce redox flow battery is considered as one of the most promising redox flow batteries due to its high voltage and low cost. However, using Zn metal anodes in this context remains problematic due to issues with corrosion and dendrite growth, as well as electrolyte incompatibility, which limits their cycling performance and practical application. Herein, an indium-based protective layer is constructed on the Zn anode cooperating with a dual-membrane cell configuration to solve these problems. Due to its unique physical and chemical properties, the zincophilic indium protective layer can effectively prevent electrolyte corrosion as well as regulate the behavior of Zn plating and stripping. Moreover, a dual-membrane cell configuration is used to mitigate electrolyte incompatibility since it uses specified ions as charge carriers and blocks the infamous H+ poisoning on the zinc side. The cell exhibits a high discharge voltage plateau of 2.2 V at 20 mA cm−2 and maintains a high average energy efficiency of 84.39 % over 80 cycles. This work presents a practical method to enhance the cycling performance of the Zn-Ce battery by incorporating an In-based protective layer with a dual-membrane cell configuration, resulting in unparalleled efficiency and stability.

Hybrid solar-biomass residential micro – Combined Heat and Power systems driven by the Partially Evaporating Organic Rankine Cycle – A case study in Southern Europe

In this study, a novel hybrid solar-biomass residential micro – Combined Heat and Power system driven by the Partially Evaporating Organic Rankine Cycle is proposed and its operation is simulated, by applying an in-house numerical model. The simulation tool is applied for a test case in Athens, Greece, where the micro-CHP system operates to cover the annual energy demand of a multi-family building. The proposed cogeneration unit covers 97.10 % and 25.85 % of the modeled building’s annual Space Heating and electricity demand, respectively, by using renewable energy sources. The annual average total energy and exergy efficiencies are equal to 53.33 %, and 10.35 %, respectively, while the power cycle can achieve thermal efficiencies as high as 9.73 %. Competitive Levelized Cost of Electricity (0.072–0.133 €/kWhel), and Levelized Cost of Heat (0.036–0.067 €/kWhth) values are estimated, with a PayBack Period between 5.17 and 9.64 years. The environmental impact of the proposed hybrid micro-CHP is anticipated to be significant, rising to 46.25 kWh of Primary Energy Savings, and 31.22 kg CO2-eq. reduction in carbon emissions per m2 of residence annually.

4E Analysis of a new cogeneration system coupling heat pumps and PEMFC in summer and winter modes

In response to the ongoing optimization of energy systems and the promotion of clean energy, this paper introduces a new high-efficiency cogeneration system based on proton exchange membrane fuel cells (PEMFC). Named the Transcritical Combined Cooling Heating and Power with Subcooling Coupled ORC (CPTSO) system, it undergoes energy, exergy, economic, and environmental (4E) assessments to evaluate its performance in both summer and winter modes. This paper also analyzes the effects of key factors on the new system's performance. The results indicate that the new system performs more effectively overall and achieves faster cost recovery during winter operations. With varying degrees of subcooling (ΔTsubcooling), the system's average energy efficiency, fuel energy saving ratio (FESR), exergy efficiency, and pollutant reduction in winter are 60.97 %, 4.51 %, 17.16 %, and 33.35 % higher, respectively, than in summer. Changes in the main evaporation temperature (Te) result in winter improvements of 74.37 % in energy efficiency, 16.86 % in FESR, 17.6 % in exergy efficiency, and 45.5 % in pollutant reduction compared to summer. Similarly, adjustments to the outlet temperature of the gas cooler (Tg) lead to winter increases of 56.75 % in energy efficiency, 0.49 % in FESR, 17.1 % in exergy efficiency, and 29.3 % in pollutant reduction over summer values.

Energy Performance of LR-FHSS: Analysis and Evaluation.

Long-range frequency hopping spread spectrum (LR-FHSS) is a pivotal advancement in the LoRaWAN protocol that is designed to enhance the network's capacity and robustness, particularly in densely populated environments. Although energy consumption is paramount in LoRaWAN-based end devices, this is the first study in the literature, to our knowledge, that models the impact of this novel mechanism on energy consumption. In this article, we provide a comprehensive energy consumption analytical model of LR-FHSS, focusing on three critical metrics: average current consumption, battery lifetime, and energy efficiency of data transmission. The model is based on measurements performed on real hardware in a fully operational LR-FHSS network. While in our evaluation, LR-FHSS can show worse consumption figures than LoRa, we find that with optimal configuration, the battery lifetime of LR-FHSS end devices can reach 2.5 years for a 50 min notification period. For the most energy-efficient payload size, this lifespan can be extended to a theoretical maximum of up to 16 years with a one-day notification interval using a cell-coin battery.

Conformal coating of PbO2 around boron doped diamond coated carbon felt positive electrode for stable and high-capacity operation of soluble lead redox flow battery

The commercialization of soluble lead redox flow battery (SLRFB) is challenging due to its limited cycle life, lower areal capacity, Pb dendrite formation, and positive electrode corrosion. However, improvements are made to a certain extent by employing additives chemistry in terms of electrolyte modification. One of the major problems in SLRFB is carbon corrosion at higher current densities. Therefore, electrode modification, specifically on the positive side, is required to improve the cyclability of SLRFB further. There is minimal literature on this aspect.Given this, efforts are being made to enhance the electrochemical performance of SLRFB by employing a boron doped diamond (BDD) coated carbon felt (CF) as the positive electrode. The BDD coated CF electrode possesses a high surface area (7.1 m2g−1) compared to bare CF (0.6 m2g−1), i.e., BDD creates porous morphology, which enables a high mass transfer and hence reduces concentration polarisation. BDD coating on the CF delays the OER and reduces the overpotential for PbO2 deposition/dissolution. The cell with BDD coated CF electrode is successfully cycled for >300 charge/discharge cycles @ 40 mA cm−2 with average coulombic efficiency (CE), voltage efficiency (VE) and energy efficiency (EE) of 97 %, 71 % and 69 % respectively. The EE is improved by 8 % in the presence of BDD coated CF as compared to CF electrode. SLRFB cell with BDD coated CF electrode has reached 80 mAh cm−2 areal capacity.

Comparative analysis of eight urea-electricity-heat-cooling multi-generation systems: Energy, exergy, economic, and environmental perspectives

The Haber-Bosch process for urea production is known for its significant carbon emissions. While the chemical looping ammonia generation method presents a potential alternative, its technical and economic feasibility still requires further investigation. This paper conducts a comparative analysis of eight renewable energy-driven urea-electricity-heat-cooling multi-generation systems by developing their energy, exergy, economic, and environmental evaluation models. Considering the fluctuation in renewable energy resources, an annual evaluation of the different systems is conducted based on a monthly time scale. The results indicate that systems based on the Haber-Bosch process have higher average energy and exergy efficiencies of 60–80 % and 40–50 %, respectively. For the chemical looping ammonia generation process, the respective efficiencies are 50–70 % and 30–40 %. Additionally, the system integrating the Haber-Bosch reaction, reduction reactor, and solid oxide fuel cell yields the highest energy and exergy efficiencies among the eight systems, at 68.2 % and 45.78 %, respectively. However, it is inferior to the multi-generation system integrating the chemical looping ammonia generation process in terms of economic and environmental performance. In addition, the system integrating the chemical looping ammonia generation process and solid oxide fuel cell has the shortest discounted payback period of 8 years, with annual revenue and net present value of 32.63 and 11.66 MUSD, respectively. While the operating expenditures of the Haber-Bosch (12.6–15.7 MUSD) are lower than those of the chemical looping ammonia generation process (14.0–17.5 MUSD), its capital expenditures (382.0–410.8 MUSD) are significantly higher than those of the chemical looping ammonia generation process (302.4–307.3 MUSD). Furthermore, the conducted environmental evaluation shows that the multi-generation system integrating the chemical looping ammonia generation process and reduction reactor exhibits lower overall carbon emissions (0.013 t CO2/t urea) compared to the state-of-the-art method of oxy-fuel coal-fired power plant for urea synthesis.

Energy saving and speed control in autonomous electric vehicle using enhanced manta ray foraging algorithm optimized intelligent systems

The integration of autonomous vehicles (AVs) with hybrid electric vehicles (HEVs) aims to address the problem of optimizing energy economy while improving reliability and safety. By using intelligent driver support technologies and sophisticated control algorithms, this method aims to lower emissions and fuel consumption. Therefore, the HEVs develop an intelligent driver aid system that integrates an energy management system (EMS) with adaptive cruise control (ACC). To maximize energy use, the system integrates HEVs with autonomous vehicle technologies. In order to maintain safe distances from the lead vehicle, identify the desired acceleration, and switch between speed and distance control, the ACC uses a deep learning system in conjunction with a tilt integral derivative (TID) controller. This ensures stability. Based on ACC commands, the EMS controls energy usage. An enhanced manta ray foraging optimization (EMRFO) technique is used to significantly enhance speed control and energy economy. Simulink/MATLAB analysis of the suggested model shows notable gains in energy consumption control, particularly with the ACC with deep neural network (DNN) system, and considerable reductions in driving risks. In addition, the system precisely controls engine torque to maintain a 72.75 % State of Charge (SoC) and an average engine energy efficiency of 32.36 %. To validate the performance, the proposed approach is put into practice in real-time configuration. The configuration for the experiment produced an ideal efficiency of 31.99 % with minimal error using the proposed method.

Enhancing energy efficiency in Asia-Pacific: Comprehensive energy policy analysis

The Asia-Pacific (APAC) region has undergone remarkable economic growth over the past three decades, significantly reducing poverty levels. However, the concurrent rise in energy consumption and its environmental impact necessitate the development of a sustainable energy system to sustain and accelerate this progress. Recognizing the critical role of energy efficiency, governments in the region have increasingly formulated and implemented energy policies, encompassing laws, regulations, and action plans. However, understanding the precise influence of these policies on energy efficiency remains a challenge. This study employs an endogenous stochastic frontier analysis (SFA) model using data from the Asia Pacific Energy Portal Policy database covering 23 emerging economies from 2000 to 2017 to assess how energy policies affect energy efficiency in the APAC region. The findings indicate that implementing energy policies correlates with an average increase in energy efficiency by 0.158%. However, the impact varies depending on whether the policies are laws, regulations, or strategies. Though the region's average energy efficiency standing is at 0.34, there has been a consistent upward trend observed from 2000 to 2017. Furthermore, optimizing aggregate energy policies has resulted in substantial energy savings, averaging 0.15 quadrillion Btu. In light of these results, we proposed some policy actions.

Evaluation of the effect of hydrogen evolution reaction on the performance of all-vanadium redox flow batteries

The exceptional advantages of vanadium redox flow batteries (VRFBs) have garnered significant attention, establishing them as the preferred choice for large-scale and long-term energy storage solutions. However, side reactions such as hydrogen evolution reaction (HER) lead to suboptimal performance of VRFB parameters, resulting in an overall decrease in VRFB performance. Therefore, it is imperative to investigate the mechanism by which HER affects VRFB performance and identify effective methods to mitigate its impact. In light of this, critical parameters such as charge-discharge curve, internal resistance, pressure-drop, pump power consumption, efficiency, and capacity retention rate are selected to evaluate the impact of HER on VRFB performance. Experimental results demonstrate that HER causes an increases in voltage during charging and a decrease during discharging stages leading to voltage loss; additionally, bubble generation significantly increases pressure drop and pump power consumption; furthermore, blockage of flow channels and electrodes due to bubbles leads to an increase in ohmic resistance. Finally, HER has a substantial impact on efficiency and capacity with an average energy efficiency of 2.92 %. After 60 cycles, the capacity retention rate decreased by nearly 7.69 %.

Comparative performance investigation of conventional and modified stepped basin pyramid solar still with improved insulation: Experimental evaluation

This study focuses on modifying the insulation of a stepped basin pyramid solar still (SBPSS). The modified SBPSS with both side insulation and the conventional SBPSS with one side insulation of the base were compared in terms of basin and basin water temperature, freshwater output, energy and exergy efficiency, payback period, and production cost. The research was carried out on two identical SBPSSs, where 0.25 m2 was the evaporation area for each case. In modified SBPSS, the insulation on both sides of the base significantly reduced heat loss, which was justified by the higher basin and basin water temperatures than conventional SBPSS. The maximum basin temperatures for conventional and modified SBPSSs were 50.49 °C and 53.74 °C, respectively, with maximum basin water temperatures of 47.21 °C and 52.86 °C. The modified SBPSS provided more freshwater (1.24 L/m2) than conventional SBPSS (0.93 L/m2) as a result of the rapid evaporation rate caused by the higher basin water temperature. For conventional and modified SBPSSs, the average energy efficiency was 22.33 % and 27.51 %, respectively, and the average exergy efficiency was 4.71 % and 6.90 %, respectively. The modified SBPSS provided freshwater at a 24.27 % lower price than the conventional SBPSS.