Cell Operating Temperature Research Articles

Floating photovoltaics: modelled and experimental operating temperatures and the impact of wind speed and direction

Floating photovoltaics (FPV) is rapidly emerging as a promising alternative to ground-mounted PV (GPV) where available land area is scarce or expensive. Improved cooling has often been reported as a benefit of FPV, as cell temperature is an important parameter for the performance of a PV system. However, more recent literature shows that the cooling effect depends strongly on FPV technology and that it is not always superior to that of open rack GPV systems. There is still a need for more information on how to estimate cell temperatures for FPV systems, and how to consider the influence of various environmental factors such as wind speed and direction. Operating cell temperature may be estimated with the PVsyst model, where heat loss coefficients (U-values) denote the heat transfer capabilities of the PV system. In this work, cell temperatures and U-values for a small footprint FPV system with east-west orientation and a 15° tilt located in Sri Lanka are studied using both module temperature measurements and computational fluid dynamics (CFD) modelling. CFD modelling allows for investigating the influence of both wind speed and direction on cell temperatures, as well as to look at the distribution of cell temperatures within the system under different wind conditions. Calculations based on measurements give Uc = 22.6 W/m2K and Uv = 4.9 Ws/m3K and correlate well with CFD calculations. We also show that wind direction, system configuration and sensor placement influence the estimated U-values, complicating the use of tabulated values for any given technology.

Clay powder in polymer composite membranes enhanced the performance of direct methanol fuel cells

Polyvinyl alcohol has the potential to be used in fuel cell membranes due to its chemical, mechanical, and membrane-forming capabilities, as well as its higher hydrophilicity and low methanol permeability. However, the pure PVA membrane has a lower proton conductivity than the NafionTM membrane. With the addition of some ceramic fillers, PVA can be a possible alternative to NafionTM membranes. Therefore, we used the solution method to prepare three polyvinyl alcohol-based composite membranes with the following compositions: a) 5 wt% PVA (polyvinyl alcohol), b) 5 wt% PVA/2 wt % PEG (polyethylene glycol)/wt.1% silicon dioxide (SiO2) nanoparticles, and c) 5 wt% PVA/2 wt% PEG/wt.1% clay powder. The membranes were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX), oxidative stability, ion exchange capacity, water absorption characteristics, conductivity, and permeability. FITR, EDX, and SEM confirmed the successful fabrication of the composite membrane, while TGA demonstrated membrane thermal stability and other parameters relevant to fuel cell membranes. The methanol permeability of the membrane is pure 5 wt % PVA, 5 wt%PVA/2 wt%/1 wt% SiO2, and 5 wt% PVA/2 wt% PEG/wt.1% Clay measured 2.37 × 10−6 cm2/s, 2.89 × 10−6 cm2/s, and 1.57 × 10−6 cm2/s, respectively. The methanol permeability of 5 wt% PVA/2 wt% PEG/wt.1% Clay is better than of Nafion117 (5.16 × 10−6 cm2/s as reported). The membrane 5 wt% PVA/2 wt% PEG/1% Clay exhibits satisfactory levels of oxidative stability (RW% = 94.09 at 1.32 h), IEC (0.232 meq/g), conductivity (0.00432 S/cm), methanol permeability (1.57 × 10−6 cm2/s), selectivity (3.63 × 10−4 Ss/cm3), and better water uptake properties at fuel cell operating temperature. As a result, it is reasonable to expect that PVA-based modified membranes will outperform NafionTM membranes in the future.

Hydrogen Crossover in Anion Exchange Membrane Fuel Cells

In recent years anion exchange membrane fuel cells (AEMFC) have started to draw more attention by potentially allowing catalysts based on more abundant materials, and by showing high performance [1]. One often overlooked parameter in these systems is membrane permeability of hydrogen, often referred to as hydrogen crossover, which directly affects fuel cell stability and efficiency. This undesirable effect creates mixed potential due to the permeated hydrogen reacting with oxygen on the cathode, and not generating useful electric energy, only water and heat [2]. The generated heat creates hotspots of temperatures enough to cause membrane defects or even destruction which further accelerates the degrading process [3].During fuel cell operation relative humidity (RH) and temperature varies in the system, therefore in this study hydrogen crossover is measured at different temperatures (between 50 and 70 ⁰C) and RH (between 30 and 100 %), on Aemion anion exchange membranes (AEMs) with and without reinforcement and with a variety of membrane thicknesses (25 and 50 μm in Figure 1. a). The hydrogen crossover is measured using a mass spectrometer (MS) at the inert gas exhaust. To avoid effects of other components pure membranes and gas diffusion layers (GDLs) were utilized without electrodes.It is shown that AEMs increase in permeability with temperature for all tested while the effect of RH depends on if they are reinforced or not (Figure 1. a). The non-reinforced membranes show a constant decrease in hydrogen crossover with increasing RH, while the reinforced show constant hydrogen crossover until full humidification where it sharply decreases. While the observed trends are different, the quantitative values between reinforced and non-reinforced membranes were relatively similar: at dry conditions, RHs lower than 50 %, crossover is 10 to 30 % lower for reinforced membranes, around 10 % higher at 70 % RH, and at full humidification a non-significant difference compared with non-reinforced (Figure 1. a). It is shown that an increase in the membrane thickness is not proportional to the decrease in hydrogen crossover, suggesting that interface resistance is not negligible. The calculated interface resistance is higher than the bulk resistance for both reinforced and non-reinforced membranes at all RHs (Figure 1. b). However, the bulk resistance is higher for reinforced membranes than for non-reinforced, while interface resistances are relatively similar. Interestingly, the ratio between the interface and the bulk resistance remains constant at all RHs. However, for the membranes without reinforcement the bulk resistance is 20 % of total crossover resistance, while for reinforced it is two times higher, 40 %. Scanning electron microscope (SEM) cross-section analysis shows that the reinforcement is a relatively thin layer of a different polymer in the membrane, which suggests that even a very thin reinforcement could affect membrane permeability properties. Understanding the effects of the reinforcement and their influence on fuel cells will allow for more durable and safer AEMFCs.Figure 1. H2 crossover measured using a MS at the inert gas side. a) At different temperatures, relative humidities and membrane thicknesses. b) H2 crossover resistance at the interface and in the bulk for membranes with and without reinforcement. Measurements are done at 70 °C and at flows 20 ml/min of both hydrogen and the inert gas (Ar).[1] D. R. Dekel, “Review of cell performance in anion exchange membrane fuel cells,” J. Power Sources, vol. 375, pp. 158–169, 2018, doi: 10.1016/j.jpowsour.2017.07.117.[2] S. S. Kocha, J. D. Yang, and J. S. Yi, “Characterization of Gas Crossover and Its Implications in PEM Fuel Cells,” 2006, doi: 10.1002/aic.10780.[3] Q. Tang, B. Li, D. Yang, P. Ming, C. Zhang, and Y. Wang, “Review of hydrogen crossover through the polymer electrolyte membrane,” Int. J. Hydrogen Energy, vol. 46, no. 42, pp. 22040–22061, 2021, doi: 10.1016/j.ijhydene.2021.04.050. Figure 1

Experimental evaluation of proton exchange membrane fuel cell performance with sinusoidal flow channel designs

Proton Exchange Membrane Fuel Cells (PEMFCs) with three distinct flow field designs were investigated: sinusoidal with a diffuser at the intake, sinusoidal serpentine, and serpentine flow fields. The sinusoidal flow field with a diffuser at the intake has been found to be the best flow field design. Following that, parametric experiments were performed on PEMFCs equipped with a sinusoidal flow field with a diffuser at the intake. Operating pressures (1–3 bar), back pressures (0–3 bar), anode humidification temperatures (40 °C–80 °C), cathode humidification temperatures (40 °C–70 °C), anode flow rates (250 sccm to 350 sccm) and cathode flow rates (250 sccm to 400 sccm) and cell operating temperatures (COT) ranging from 40 °C to 70 °C were all adjusted. The experimental findings showed that a COT of 60 °C, a 3-bar back pressure, a 3-bar working pressure, cathode humidification at 70 °C, anode humidification at 60 °C, and flow rates of 300 sccm for the anode and 350 sccm for the cathode resulted in the best PEMFC performance.

Multi-junction solar cell measurements at ultra-high irradiances for different temperatures and spectra

This paper reports experimental results on the impact of the temperature and spectral conditions on the behaviour of III-V multi-junction solar cells, employed in concentrator photovoltaic modules, operating under ultra-high concentration (UHC) conditions. The electrical parameters of the I–V curves of a 3-junction solar cell were measured using an experimental set-up based on a multi-flash indoor solar simulator, which allows adjustment of the cell operating temperature up to 85°C and reaching irradiance concentration levels up to 2200 suns under controlled spectral conditions. The measurements presented are unprecedented, as there are no previous publications that combine different spectral and temperature-controlled experimental conditions in the UHC range, thus extending the range of studies reported in works carried out at lower concentrations.

Effects of minor alloying elements (Si, Mn and Al) on the corrosion behavior of stainless steels in molten carbonate fuel cell cathode environment

Abstract Effects of minor alloying elements (Si, Mn, and Al) on the corrosion resistance behaviors of stainless steel (SS) modified 310S used as a cathode current collector (CCC) material for molten carbonate fuel cells (MCFC) were examined in a mixture of 62 mol% Li2CO3–38 mol% K2CO3 at 650 °C by measuring the change in corrosion potential and the potentio-dynamic, potentio-static polarization responses. The corrosion potential of modified 310S gradually increased after 9 h of immersion due to an active to passive transition and that of SSs added with minor alloying elements drastically increased before 6 h of immersion due to the reactive alloys. Si, Mn, and Al addition to base SS led to a decrease in corrosion resistance due to the rapid corrosion rate at the cathode operation potential, −40 mV, of the MCFC. The steady state current densities of SSs added with minor alloying elements were higher than that of 310S and modified 310S. Addition of Si, Mn, and Al induced a decrease in corrosion resistance of CCC materials in molten carbonate fuel cell operating temperatures, 650 °C.

Control strategy of solid oxide electrolysis cell operating temperature under real fluctuating renewable power

Power-to-liquid (PtL) technology through solid oxide electrolysis cells (SOECs) can efficiently convert renewable energy sources into synthetic fuels for long-time energy storage. However, due to its fluctuation and intermittence, renewable energy sources only produce time-varying currents, which directly impact the operating temperature of SOEC, generating high thermal stresses for SOEC and reducing its durability. To deal with this issue, a control-oriented SOEC dynamic model containing an electrochemical part, a reversible water gas shift (RWGS) part, and a thermodynamic part, was developed in this paper. Afterward, main control parameters, able to adjust SOEC operating temperature effectively, were determined through the Extended Fourier Amplitude Sensitivity Test (EFAST). The corresponding results show that the air flow rate was the best choice to control SOEC temperature when it works in a low current density case, while the fuel flow rate becomes optimal when SOEC operates in a high current case. Given this knowledge, an adaptive feedback control strategy was proposed to stabilize the operating temperature of SOEC in practice. In the end, the effectiveness of the proposed control was demonstrated through step signals of current in both low- and high-current density cases and an actual fluctuating current from real solar cells.

A study of preheating liquid desiccant and its effect on the performance of a PV/T system

When photovoltaic (PV) cells operate, their electrical efficiency decreases due to a rise in temperature. To counteract this, Photovoltaic/thermal (PV/T) systems have been created to maintain PV cell electrical performance and utilize the heat they release to warm fluids. A low temperature is required for liquid desiccant regeneration, which allows for the possibility of using the heat released by PV cells to preheat a unit prior to the main heating unit. This study investigates the use of an aluminum cold plate with a serpentine tube placed behind a PV panel to transfer heat dissipated by PV cells to a desiccant solution. Two desiccant solutions were tested: lithium chloride (LiCl) and potassium formate (KCOOH). Using COMSOL Multiphysics, three-dimensional CFD simulations were conducted to analyze the temperature of both the photovoltaic cells and the solution exiting the cold plate. The simulation results were then used to determine the hybrid system's electrical, thermal, and overall efficiencies. Under nominal operating cell temperature (NOCT) conditions, the total efficiency of the hybrid system was 57.15 % and 55.28 % when using LiCl and KCOOH solutions, respectively, with a cold plate inlet temperature of 25 °C and a mass flow rate of 30 g.s-1. Given the similar efficiency of the system and the lower corrosiveness and cost of KCOOH solution compared to LiCl solution, the study concluded that using KCOOH solution is more appropriate. Simulations were conducted under NOCT conditions to compare the system's performance using desiccant solution and water. As expected, the thermodynamic properties of water resulted in a greater decrease in temperature and increased cell efficiency, but using the desiccant solution directly in the cold plate for cooling eliminated the need for an additional heat exchanger in the system.

Effect of Ni loading onto Pt (Pt‐Ni/C) electrocatalysts for PEM fuel cell: A study of ORR activity, stability, and temperature effect

AbstractPt is a noble metal when alloyed with transition metals like Ni onto the carbon support, minimizes the cost and increases the oxygen reduction reaction (ORR) activity and stability of Pt‐Ni/C electrocatalyst in a low‐temperature proton exchange membrane (LTPEM) fuel cell. A simple sonochemical‐based synthesis of Pt‐Ni/C bimetallic nanoparticles is carried out through varying amounts of Ni and Pt precursors. The various combinations of Pt and Ni metal (50:50, 75:25, and 83:17) nanoparticles were uniformly distributed on a carbon support. The shifting of 2θ values to higher levels in XRD patterns confirmed the alloy formation between Pt and Ni. The carbon (60 wt. %) supported Pt and Ni (40 wt. %) electrocatalyst ink is coated on a carbon paper which acts as a gas diffusion layer (GDL). The electrocatalytic performance of Pt‐Ni/C was evaluated in the PEM fuel cell using an electrochemical test station. The best performance was observed with the Pt: Ni (83:17) coated electrocatalyst, which delivered 0.162 W/cm2 power at 0.45 V. Also, the PEM fuel cell performance was enhanced by increasing the single cell's operating temperature.

Estimation models of photovoltaic module operating temperature under various climatic conditions

Accurate control of the operating temperature is essential for achieving optimal efficiency in the use of solar panels. The Normal Operating Cell Temperature (NOCT) is a widely used method for estimating module temperature, but it is not always accurate for all conditions. In this paper, the authors propose four different models for estimating module temperature using various techniques including Neural Networks, a linear method proposed by Ross, and a Fitting method. The objective is to find more accurate methods than the NOCT model. The results show that all four models provide good agreement between measured and calculated module temperatures, with R² > 0.91 and RMSE < 3.74 for clear days, and considering the resources of time, cost, and expertise necessary for simulating or evaluating the proposed model, the two models based on RN neural networks offers a more cost-effective solution, by utilizing straightforward mathematical skills, the RN model demonstrates applicability in any environment, making it a preferable choice over the NOCT model for predicting polycrystalline photovoltaic module temperature under different climatic conditions. The proposed models can be used to estimate PV module temperature with good precision under different climatic conditions.

Data-based modelling of proton exchange membrane fuel cell performance and degradation dynamics

Proton exchange membrane fuel cell (PEMFC) is in the commercial adoption process for hard-to-decarbonize applications such as transport. However, its long-term durability, reliability, diagnostics, and performance remain a critical challenge. In this study, the data-based modelling technique, artificial neural network (ANN), is adopted to comprehend performance degradation and thermal and pressure dynamics. Experimental data consisting of polarization and cyclic voltammetry data are acquired after every 6,000 accelerated stress test (AST) degradation cycles as stipulated by the US Department of Energy guidelines. Over 40,000 test cases were considered for training and evaluating the neural network comprising data from 30,000 full-cell AST cycles. Fuel cell operating temperatures, pressures, flow rates, and relative humidities are varied to capture the entire spectrum of PEMFC performance characteristics. Parameters such as the number of AST cycles endured or instantaneous catalyst electrode surface area, operating current density, reactant flow rate, relative humidity, system temperature and pressure are considered as feature vectors (inputs) to predict cell output voltage, reactant outlet pressure and temperature for both anode and cathode streams. Data preprocessing and batch learning are implemented in Python to improve prediction accuracy and computational time; considering the substantial nonlinear data sets, various Keras library optimizers and corresponding hyperparameters are investigated for better convergence. The trained neural network model is evaluated on 15,000 test cases resulting in an R2 ≥ 0.995 for all the predicted variables, demonstrating the capability of data-based models to accurately predict the nonlinear behavior of such electrochemical systems with minimal processing time, advocating for their application in real-time system monitoring, controls and diagnostics.

Thermal performance of three concentrating collectors with bifacial photovoltaic cells part I – Experimental and computational fluid dynamics study

Bifacial photovoltaic cells can produce electricity from incoming solar radiation on both sides. These cells have a strong potential to reduce electricity generation costs and may play an important role in the energy system of the future. However, today, these cells are mostly deployed with one side receiving only ground reflection, which leads to a profound sub-optimal utilization of one of the sides of the bifacial cells. Concentration allows a better usage of the potential of bifacial cells, which can lead to a lower cost per kWh. However, concentration also adds complexity due to the higher temperatures reached which add the requirement of cooling in order to achieve higher outputs. This way, this paper focuses on the effectiveness of forced air circulation methods by comparing the thermal performance of three specific concentrating bi-facial collector designs. This paper developed a computational model, using ANSYS Fluent intending to assess the thermal performance of a covered concentrating collector with bifacial Photovoltaic (PV) cells. These results have then been validated by outdoor measurements. Results show that even a simple natural ventilation mechanism such as removing the side gable can effectively reduce the receiver temperature, thus resulting in favourable cell operation conditions when compared to the case of an airtight collector. Therefore, compared with a standard model, a decrease of 13.5% on the cell operating temperature was reported when the side gables are removed. However, when forced ventilation is apllied a 22.8% reduction on temperature is found compared to the standard air-tight model. The validated CFD model has proven to be a useful and robust tool for the thermal analysis of solar concentrating systems.

SCAPS Numerical Analysis of Graphene Oxide /TiO2 Bulk Heterojunction Solar Cell Sensitized byN719 Ruthenium Dye

Solid-state dye-sensitized solar cells (SSDSC) have been fabricated using two different metal oxide materials, graphene oxide and titanium oxide, are used as hole and electron transport materials, respectively. The N719 dye ruthenium between the hole and electron transport materials to act as an absorber layer in your Go/N719dye/TiO2 solar cells. Through the SCAPS-1D simulation, it was found that the Go/N719dye/TiO2 solar cells have significantly improved the performance of the solar cells compared to the Go/TiO2 solar cells. Specifically, the short circuit current (Jsc) has increased from 0.17 mA/cm2 to 1 mA/cm2, the open circuit voltage (Voc) has increased from 0.2 V to 1 V, and the power conversion efficiency (η) has increased from 0.02% to 2.5%. Additionally, Various factors that can affect the performance of Go/N719 dye/TiO2 solar cells. It was found that the optimal dye thickness for achieving high short circuit current density, high power conversion efficiency, and high open circuit voltage is between 200nm and 300nm. Furthermore, the operating temperature of the solar cells also affects their performance. Increasing the operating temperature negatively affects the open circuit voltage and power conversion efficiency of the cells, while the short circuit current density is slightly enhanced. Finally, the efficiency of a solar cell can be affected by the type of metal used for the electrode and the type of semiconductor material used in the cell. In Ni and Cu electrodes solar cells ohmic contacts allow for efficient transfer of electrons, whereas Schottky barriers can impede electron flow and reduce efficiency in Mo and Ag electrodes solar cells .

Chemical and Mechanical Degradation of the Interface between Li7La3Zr2O12 Electrolyte and LiNi0.6Mn0.2Co0.2O2 Cathode as a Result of Electrochemistry

All solid-state Li-ion cells promises high energy density and high safety standards over conventional Li-ion cells based on liquid electrolytes. The first principle calculations shows that the most of the potential candidates for solid electrolytes for Li-ion cells have small electrochemical stability window. The limited electrochemical stability window leads to electrochemical reactivity with the cathode when cycled beyond the voltage limit. The reactions products are often leads to increased overpotential, hence rapid capacity fade during continuous cell operation. In addition to the electrochemical reactions, mechanical incompatibility further makes the cathode-solid-electrolyte interfaces prone to cracking, as cathodes undergoes structural changes during lithiation/delithiation. Indeed many experimental works have also showed limited cyclability of all-solid-state Li-ion cells owing to interfacial side reactions and mechanical cracking. Therefore, electrochemistry induced mechanical failure and electrochemical side reactions at the interface remains the bottleneck for the development of all-soli-state Li-ion cells. This paramount challenge invites us to systematically investigate the aforementioned problem by probing non-destructively near the cathode-solid-electrolyte interface. We introduce a model system that utilizes very thin layer of LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode (60-600 nm) on top of bulk Al-doped-Li7La3Zr2O12 (Al-LLZO) solid-electrolyte pellet. This unique system allows us to non-destructively probe the electrochemical reaction by combined in-operando and ex-situ X-ray absorption spectroscopy (XAS), with probing depth beyond the cathode-solid-electrolyte interfaces.In this work, we elucidate the mechanism of electrochemical failure of NMC622 cathode and Al-LLZO solid-electrolyte interface at different temperature, through combined ex-situ and in-operando characterization techniques. The study revealed that the electrochemical reactivity is dependent on cell operation temperature. For the ex-situ samples that was cycled at higher temperature (80 ⁰C), the reduction of transition metals in cathode, i.e., nickel and cobalt was evident by soft X-ray absorption spectroscopy (XAS) of their respective L-edges. The results match closely with DFT prediction for the interfaces at high voltage. On the other hand, the in-operando XAS experiment, where characterization was done at room temperature, the reduction of transition metals in cathode, and hence electrochemical reactivity, was not observed. These results remarkably outline that electrochemical reactivity of solid-electrolyte and cathode interfaces at high voltage is kinetically inhibited at low or near room temperature, and hence very sensitive to cell operating condition. Nonetheless, it was found that irrespective of operating conditions i.e., temperature, the cell capacity rapidly decays as number of cycles continue. The focused ion beam scanning electron microscopy (FIB-SEM) revealed that this can be mostly attributed to intergranular cracks in NMC622 cathode films as well as to delamination of the cathode-solid-electrolyte interfaces during cell operation. As these cracks, in cathode films and at the interfaces, grows, the overpotential/impedance increases due to limited contacts for effective Li+ migration.The current work contributes to the field by showcasing interfacial degradation pathways in cell operation by novel design of experiments that allows for both in-operando and non-destructive characterization. The findings of this work will guide towards engineering cells of practical use. Figure 1

Development Progress of a 70% Efficient Hybrid SOFC-I.C. Engine Hybrid System for Stationary Applications up to 1 MW

Flexible and dispatchable, high-efficiency power generation supplied with carbon-neutral renewable fuels is needed to help enable defossilization of the electric grid. Pressurized, hybrid SOFC systems fueled with hydrogen, biogas, or renewable natural gas can generate clean power at ultra-high efficiency. This presentation presents an update on the development progress of a full-scale, hybrid system that targets low cost (<1000 $/kW) and ultra-high efficiency (70%-LHV) distributed power generation for applications up to 1 MW. The system features mature, metal-supported SOFC technology and the system design, control, hardware integration, and demonstration activities are funded by the U.S. DOE ARPA-E INTEGRATE Program. Some of the more novel aspects of the system include the intermediate operating cell temperature (600°C) and internal reforming capabilities which enable excellent thermal management and effectively reduce air preheater duty by >60% over more conventional SOFC systems operating near 800°C. Pressurization of the system decreases area specific resistance (ASR) and increases stack power density, thereby lowering capital cost. The use of a gasified diesel engine converts the residual chemical exergy in the anode tail-gas from the SOFC to drive auxiliaries and produce net additional power. Furthermore, the syngas engine enables a simple engine after-treatment for achieving ultra-low engine emissions (NOx, CO, PM, UHC). Updates on critical hardware advancements around pressurized multi-stack, 30 kW fuel cell modules, low-speed high efficiency rotating equipment, and ultra-high efficiency power electronics are provided. Results from experimental testing, system design and layout, and demonstration test facility capabilities are presented and discussed. The presentation concludes with a techno-economic outlook for such power generation systems in various stationary applications, as well as comparison with competing distributed generation technologies, such as solar PV-battery systems, microturbines, stationary engines, and non-hybridized SOFC technologies. Figure 1

A novel integration of plasma gasification melting process with direct carbon fuel cell

As municipal solid waste (MSW) is a low-cost, available, and basically renewable source, energy recovery from MSW is a beneficial technique for reducing fossil fuel usage while also lowering MSW disposal challenges. The current study proposes a novel scheme consisting of plasma gasification melting (PGM) process and direct carbon fuel cell (DCFC) system for converting MSW into high-quality syngas and power. Plasma air and high-temperature steam are employed in the process as gasification agents. The DCFC runs on the pyrolysis char, which is a carbon-rich source and is extracted during the PGM process and sent to the DCFC. The process is simulated in Aspen Plus, and a computational model for estimating the DCFC's output voltage and power is developed in MATLAB. Effects of main operating parameters, including equivalence ratio, steam to biomass ratio, plasma energy ratio, char separation fraction, and fuel cell operating temperature on the system's performance indicators, namely syngas composition, syngas lower heating value, syngas yield, gasification temperature, overall efficiency, and DCFC power output were investigated. By increasing the char separation fraction, more pyrolysis char was extracted and forwarded to the DCFC, which leads to less amount of char entering the gasification section and higher power output through the DCFC. Keeping other parameters constant, at a fuel cell operating temperature of 923 K, the optimal value for char extraction fraction was 0.15, resulting in a 79.5% overall efficiency.

Enhancing geothermal ORC power generation with SOFC: A comprehensive parametric study on thermodynamic performance

Geothermal energy is a promising renewable energy source due to its abundant global reserves. However, most geothermal resources are of low grade, severely restricting their power generation capacity and efficiency. In this study, the geothermal organic Rankine cycle power generation system is combined with a solid oxide fuel cell-gas turbine system to improve the overall power supply and heat utilization efficiency. The heat source and cycle temperature are upgraded using high-temperature solid oxide fuel cell waste gas, and the combined system’s efficiency is further improved through cascade heat utilization. Electrochemical-thermodynamic models are developed for the proposed system, and energy-exergy analysis is carried out. The effects of fuel cell current density, operating temperature and geothermal grade on the combined system’s performance are comprehensively analyzed. Compared to the standalone geothermal system, the energy efficiency and output power of the organic Rankine cycle increase by 8.11% and 7.95% respectively in the baseline case. Under the lowest geothermal temperature condition, the cycle output power is improved by 22.64%. The net power of the combined system can vary from 358 kW to 846 kW by adjusting the fuel cell current density from 1000 A m−2 to 8000 A m−2, demonstrating a flexible power supply capability. The optimal solid oxide fuel cell operating temperature is 1023.15 K, resulting in the highest system overall energy efficiency of 14.85%. The presented work provides essential guidelines for improving geothermal power generation performance and designing applicable combined systems.

Enhancement of battery thermal management system using a novel structure of hybrid liquid cold plate

Battery thermal management system (BTMS) is a crucial component of electric vehicles (EVs) as it ensures optimal operating temperature of battery cells, which is critical for battery safety and performance. Among various cooling methods, liquid cooling is the most reliable owing to its high heat transfer coefficient and low power consumption. In this study, a liquid cold plate (LCP) suitable for different ambient conditions was developed, with optimized power consumption and without pre-cooling the coolant. We investigated six different microchannels, including straight, wavy walls, and metal foam-embedded microchannels, in three different ambient conditions (20 °C, 25 °C, and 35 °C) at various coolant mass flow rates (ranging from 2.5 to 17 kg/s). Our results showed that the wavy walls microchannel reduced the maximum temperature by 4–6 °C, depending on the wave amplitude. Additionally, using fully embedded metal foam microchannels resulted in a 14 °C decrease in the maximum temperature compared to that of straight microchannels, while the temperature difference of the battery module remained within an acceptable range. We also found that a thick layer of metal foam in the vicinity of the microchannel walls decreased the battery module temperature by up to 4 °C while reducing the pumping power, especially at low coolant flow rates. Deploying the wavy microchannel reduced the pumping power between 50 and 73%, while a thin layer of metal foam caused a 50% decrease in pumping power.

An improved numerical model to predict the operating temperature and efficiency of solar photovoltaic systems.

Solar photovoltaic (PV) technology has a huge potential for producing renewable energy and reducing greenhouse gas emissions. An increase in the PV cell temperature in real operating conditions reduces the actual output of a solar PV system. A 1D transient multi-layered model, based on the fundamentals of the finite difference method, has been developed to predict the operating cell temperature. Since a PV system operates in stochastic wind conditions and is not subjected to any predefined thermal boundary condition, several expressions of convection coefficient have been scientifically analyzed to determine the most suitable expression. The novel calculation approach assumes explicit radiation terms and implicit convection terms to linearize the equations and get rid of any iterative process. Comparison with experimental results shows that the convection coefficient derived from boundary layer theory corresponding to uniform heat flux predicts the cell temperature with the best accuracy showing a mean error of only [Formula: see text] and [Formula: see text]. Splitting the heat source across different solar PV layers produces a maximum change of [Formula: see text] only and can be avoided due to the involved complexity. The study proposes a new piece-wise function for PV efficiency in terms of cell temperature and irradiation. This novel function predicts PV efficiency on a sunny and a cloudy day with [Formula: see text] and [Formula: see text] mean errors, respectively, which are considerably lower than errors obtained using other popular functions in the literature. The model helps in predicting actual output from a PV system more accurately which should enable taking more informed decisions regarding the location of installation, PV technology, and the need for a cooling method.

Thermo-economic analysis of a polygeneration system using biogas and waste tire based on the integration of solid oxide fuel cell, gas turbine, pyrolysis, and organic rankine cycle

To optimize the biogas power generation process and waste tire disposal, a novel polygeneration system has been conceptualized. The hybrid design comprises a solid oxide fuel cell-gas turbine subsystem, tire pyrolysis reactor, organic Rankine cycle, and waste heat recovery subsystem. The biogas is first utilized by the solid oxide fuel cell and gas turbine for power generation. Subsequently, the high-temperature exhaust is utilized to preheat the fuel and oxidant and to heat the pyrolysis reactor and organic Rankine cycle, thereby improving the power generation and energy conversion efficiency. A comprehensive case study has been carried out to verify technological and economic feasibility of the proposed scheme. The results demonstrate that the net energy efficiency of the system is 70.11 % with an exergy efficiency of 69.65 %, and that the hybrid system maintains a high level of performance even when the fuel cell operating temperature varies. The irreversibility mainly arises from the pyrolysis reactor, cell stack, and combustion chamber. The new design requires only an initial investment of 722.93 k$ and can be recovered in 5.09 years with a net present value of 1795.51 k$ over its 25-year service life. Therefore, the proposed system is highly promising and suitable for implementation.