Thermal Efficiency Research Articles

Numerical and experimental analysis of a cross-finned solar receiver for parabolic dish collectors

A parabolic dish solar collector (PDC) is used to concentrate solar radiation on a receiver to produce hot water or steam for various thermal applications. The solar receiver of the PDC is one of the significant components to improve the overall efficiency of the PDC. The present study is a numerical and experimental investigation of the thermal performance of a solar receiver with vertical fins with and without cross fins. The fin orientation was investigated using 0.056 kg/s, 0.083 kg/s, and 0.111 kg/s water flow rates. COMSOL Multiphysics® was used to simulate the receiver to determine the receiver’s temperature behavior. The thermal performance parameters such as heat gain, heat loss, convective heat transfer coefficient, and thermal, and exergy efficiency were analyzed under various flow conditions. The cross fins effectively prolong the water residence, increasing turbulence, and heat transfer and reducing heat loss to the surroundings. The receiver with cross fins at higher flow rate conditions shows higher thermal performance than lower flow rate and without fins conditions. The solar radiation during the outdoor testing is in a range of 300–950 W/m2 and the ambient temperature varies from 30-37 °C. The peak average thermal and exergy efficiency obtained for the cross-finned receiver at 0.111 kg/s is 64.4 %, and 6.3 %, respectively. Cross-finned receiver operating at 0.111 kg/s reduced CO2 mitigation rate, estimated at approximately 0.29 tons of CO2 per year, along with a lower carbon credit gain at $0.47. Thus, the proposed cross-fin solar receiver demonstrates improved thermoeconomic performance than conventional receiver designs, offering a more cost-effective design with minimal investment.

Rice husk reuse as a sustainable energy alternative in Tolima, Colombia

Colombia has great potential to produce clean energy through the use of residual biomass from the agricultural sector, such as residues obtained from the life cycle of rice production. This document presents a mixed approach methodology study to examine the combustion of rice husks as a possible energy alternative in the Tolima department of Colombia. First, the physicochemical characteristics of the rice husk were analyzed to characterize the raw material. Next, System Advisor Model (SAM) software was used to model a bioenergy plant to obtain biochar, bio-oil, and biogas from the combustion of rice husks and generate performance matrices, such as thermal efficiency, heat rate, and capacity factor. Then, the project was evaluated for financial feasibility using a mathematical model of net present value (NPV) with a planning horizon of 5 years. Finally, a subset of the local population was surveyed to assess perspectives on the project in the region. The results of the rice husk physicochemical analysis were the following: nitrogen content (0.74%), organic carbon (38.04%), silica (18.39%), humidity determination (7.68%), ash (19.4%), presence of carbonates (< 0.01%), and pH (6.41). These properties are adequate for the combustion process. The SAM simulation showed that the heat transferred in the boiler was 3180 kW, maintaining an efficiency between 50 and 52% throughout the 12 months of the year, meaning that the rice husk can generate electricity and thermal energy. The financial analysis showed that the internal rate of return (IRR) was 6% higher than the opportunity interest rate (OIR), demonstrating economic feasibility of the project. The design and creation of a rice husk processing plant is socially and environmentally viable and has the potential to contribute to the economic development of the Tolima community and reduce greenhouse gases. Likewise, this activity has the potential to promote energy security for consumers and environmental sustainability while at the same time being economically competitive.

Computational study of the performance of a solar dryer for improvement in the shelf life of the food materials.

In this study, the thermal and drying characteristics of a thin layer food sample were investigated. An indirect type, simple, efficient, and economically feasible solar dryer was fabricated and used for food preservation. However, a dynamic model of a fabricated solar dryer was also presented to gain a better insight into the drying and thermal actions. This model consists of thermal modeling of the drying chamber, solar collector, and solar-dried food sample. The law of conservation of energy was applied to evaluate the temperature at different sections of the solar dryer with respect to drying time. All listed model equations were solved in the MATLAB environment. This study helps to examine the influence of solar radiation on the collector plate temperature, drying chamber temperature, food sample temperature, and performance parameters such as thermal efficiency with respect to drying time. Model data was found in good agreement with experimental data within a 4% error. It is concluded that the drying of food material is affected by air temperature, the collector temperature, mode of heat transfer, and material characteristics such as dimension and mass of the food sample.

Thermal performance of a novel traditional Chinese personal heating device (Huotong) combined with PCMs

Chinese traditional individual heating equipment with a history of hundreds of years “Huotong” was widely used in rural areas. The Huotong consisted of a closed wooden barrel-shaped outer wall and an iron basin with combustion layer. However, the traditional Huotong had problems of low energy utilization efficiency and poor thermal comfort. Thus, a novel Huotong combined with phase change materials (PCMs) was proposed. The basic model of novel Huotong was designed and manufactured. The thermal performances of the novel Huotong under two kinds of heat sources of charcoal heating and electric heating were investigated. The results showed that: (1) Under the method of charcoal heating, the heat storage and thermal comfort performance of the novel Huotong were higher than that of the traditional Huotong. Under the three-charcoal mass of 0.15, 0.25 and 0.5 kg, the heat storage performance of the novel Huotong was 1.36, 1.43 and 1.52 times of the traditional Huotong, respectively. The average PMV values of the novel Huotong was 0.92, 1.17 and 1.31, while for the traditional Huotong was 0.87, 1.32 and 1.58, respectively. (2) Under the four electric heating methods, the thermal efficiency of the novel Huotong was 1.63, 1.61, 1.47 and 1.39 times of the traditional Huotong, respectively. The heat storage performance was 1.72, 1.67, 1.47 and 1.28 times than that of the traditional Huotong. The average PMV values of the novel Huotong was 1.25, 1.22, 0.69 and 1.68, while for the traditional Huotong was 1.64, 1.53, 0.87 and 2.03, respectively.

Utilization of hydrogen and methane as energy carriers with exhaust gas recirculation for sustainable diesel engines

Hydrogen and methane as secondary fuels in diesel engines can be promising solutions to meet energy demand. The current study investigated the effect of the specialty gases of different compositions on diesel engine performance and exhaust gases. Four gases with various compositions of exhaust gas recirculation (Carbon monoxide, Carbon dioxide, and Nitrogen) and fuels (Hydrogen and Methane) were used at various mass flow rates of 10, 20, and 25 LPM (liter per minute), and various engine speeds of 2000, 2500, 3000, and 3500 rpm (revolutions per minute). The procured results revealed that adding specialty gases improved brake thermal efficiency and power. Similarly, the brake-specific fuel consumption was also massively retarded compared to diesel due to the influence of the hydrogen and methane composition. However, the fuel with the higher nitrogen reported less BTE (brake thermal efficiency) and comparatively higher exhaust gas temperature owing to the higher presence of nitrogen in their composition. Regarding emissions, including exhaust gas recirculation dropped the formation of pollutants efficiently compared to diesel. Among various fuels, Case 1 (30 % H2, 5 % CH4, 5 CO2, and 60 % CO) reported the lowest emission of NOx, and Case 2 (25 % H2, 5 % CH4, 5 CO2, 30 % CO, and 35 % N2) of CO and CO2 emissions. Generally, specialty gases with a variable composition of exhaust gas recirculation gases can be a promising sustainable replacement for existing fossil fuels.

Empirical Study of the Effect of Nanocoolant Particles on Corrosion Rate of 316 Stainless Steel

The advancement of nanotechnology has had an impact on the use of heat exchangers. Nanocoolants, which offer higher thermal efficiency than traditional coolants, have paid significant attention. These innovative fluids, which contain nanomaterials, not only have better heat efficiency but also improve energy efficiency compared to regular coolants. However, the presence of solid nanoparticles in the coolant may cause corrosion and erosion of tubes, leading to massive degradation of those parts. To evaluate the effectiveness of nanocoolant particles, this research was conducted by studying the impact of using nanocoolant on erosion-corrosion occurring on metal surfaces. The study focused on the erosion-corrosion of stainless steel (AISI 316) in coolant solutions containing nanoparticles. The experiments utilized a rotating cylinder electrode (RCE) with rotational speeds ranging from 0 to 1800 rpm and a temperature range of 30°C-70°C. The corrosion rate was determined using the linear polarization resistance (LPR) method, while the erosion was measured by calculating the average surface roughness of the samples. The design of the experiment (DOE) was utilized to find the mathematical expressions of the effects of the nanocoolant on erosion and corrosion. The findings revealed that the corrosion rate and surface roughness of the samples increased with an increase in temperature and rotation speed. Furthermore, the erosion-corrosion effects of the nanocoolant were less significant in stagnant conditions than in flow conditions, and significant differences were observed when compared with conventional coolant. Additionally, synergistic erosion and corrosion processes were detected at higher temperatures and higher rotation speeds for both types of coolants.

Energy, Exergy, Exergoeconomic, and Environmental (4E) Analysis of the Existing Gas Turbine Power Plants in BOB - PT. Bumi Siak Pusako Pertamina

The power plants in Indonesia are mostly used to supply energy for the industrial sector, including the upstream oil and gas as well as mining companies. Several companies operating in Riau contribute to the status of the region as the largest oil producer in Indonesia. These companies rely on self-generated electricity for their operations with subsequent impact on the environment. Therefore, this research was conducted to analyze the flow of energy, exergy, exergoeconomic, and environment at the 6 MW power plant operated by BOB - PT Bumi Siak Pusako - Pertamina Hulu. The second law of thermodynamics was used to evaluate energy efficiency as the maximum achievable effort. This was further integrated with economic principles to appraise the useful and wasted costs associated with thermodynamic systems through the concept of exergoeconomics. The results showed that the thermal efficiency of the gas turbine power plant was 42.85% and the exergy efficiency was 33.22% with the largest loss recorded in the combustion chamber to be 3.091 MW in the form of vibration, friction, or expansion of the components. It was also discovered that the exergy efficiency of each component was above 75%, thereby indicating the components of the gas turbine power plant components were in good condition. Moreover, the largest exergy destruction cost was 2349.16 USD/h and the exergy cost was 3,778.05 USD/kWh. The exhaust emission generated by the gas turbine power plant was 0.21 kg/s or equivalent to 0.1425 kg/kWh requiring a forest area of 11.63 ha. The results showed that the analytical method used could be comprehensively developed and applied to other power plants in Indonesia. It could also be used to understand system performance, identify energy losses, optimize energy efficiency, and link economic aspects with energy use.

Utilizing waste heat from data centers with adsorptive heat transformation – Heat exchanger design and choice of adsorbent

The electricity and water consumption of data centers is growing on a global scale. A shift towards liquid cooled racks in combination with thermally driven cooling can help to reduce the electricity and water demand associated with the necessary heat rejection. To quantify the potential of adsorptive heat transformation devices in reducing the electricity and water demand, the prediction of thermal efficiency, heat flow rates and energy efficiency ratio is required. To this end, a numerical model is newly developed using basic adsorption heat exchanger theory. This model can predict the necessary performance indicators with respect to temperatures and volume flow rates, heat exchanger design and adsorbent. The full performance map of a market-available adsorption chiller (71 points) and own measurements are used for calibration and rigorous validation of the model. An average deviation (experiment vs. calculation) of 8.3 % in terms of thermal efficiency and 7.2 % in terms of heat flow rates is achieved, indicating a very good agreement for a wide range of temperatures. At a moderate liquid cooled rack outlet temperature of 50 °C, a heat rejection temperature of 26 °C and a cold aisle inlet temperature of 18 °C the cooling power of the silica gel reference chiller of 5.3 kW can be increased by 59 % to 8.5 kW at a partial energy efficiency ratio (pumps and control, no fans) of > 20 by assuming MIL-100(Fe) as adsorbent on a flat-tube lamella heat exchanger. The model can be used in subsequent annual system simulations to quantify the savings in electrical power and water consumption, which strongly depend on the ambient conditions.

Experimental study and performance enhancement of a novel micro heat pipe photovoltaic/thermal system in a cold region

The photovoltaic/thermal (PV/T) system, which utilizes solar energy to generate electricity and thermal energy, has significant potential in the northwest region of China, an area with abundant solar irradiation. To improve the performance of the micro heat pipe PV/T system, the study analyzed the system's thermal collection efficiency and power conversion efficiency using numerical simulation of the PV/T panel. The model incorporated double-layer glass and replaces water with nanofluid as the working medium inside the airfoil heat exchanger. The average relative error of the model was 0.9 %. In experiments conducted in Lanzhou, located in the northwest region of China, the power conversion efficiency reached its peak of 12.64 % during winter, while the thermal collection efficiency reached its maximum of 39.45 % during summer. Moreover, utilizing R141b as the working fluid in the micro heat pipe resulted in an average increase of 7.14 % in thermal collection efficiency and an average increase of 4.46 % in power conversion efficiency compared to acetone. This indicated that R141b outperforms acetone in terms of system performance. The study observed that the highest overall efficiency is achieved when the air layer thickness of the double-layer glass is 11 mm. The thermal resistance between the inner wall of the airfoil heat exchanger and the water in the PV/T components was the highest, reaching 48.85 %. Therefore, it was necessary to use nanofluids instead of water to reduce the thermal resistance of PV/T modules. The system performance remained relatively stable when the volume fraction reaches 8 %. At this volume fraction, the Al2O3-water nanofluid, Cu-water nanofluid, and Ag-water nanofluid increased the power conversion efficiency by 0.34 %, 0.72 %, and 0.77 % respectively. Moreover, they improved the thermal collection efficiency by 1.16 %, 2.69 %, and 2.78 % respectively. The micro heat pipe PV/T system was utilized for winter heating of farmers in Lanzhou and Jinchang cities. It maintained an indoor temperature of over 16 ℃ throughout the day, thus meeting the indoor heating standards.

Exploration Of Key Approaches to Enhance Evacuated Tube Solar Collector Efficiency

Exploration Of Key Approaches to Enhance Evacuated Tube Solar Collector Efficiency

Experimental investigation on the performance of MXene/C-dot hybrid nanofluid-based photovoltaic/thermal system: An Energy, Exergy, and Enviro-Economic analysis

Nanofluids (NFs) with exceptional heat transfer properties are increasingly being adopted in solar collectors as heat transfer fluid (HTF). Hybrid photovoltaic thermal systems are becoming more popular because they increase overall efficiency by producing both high- and low-grade electricity. This research focuses on the application of thermally efficient NFs for enhancing the thermal and electrical output of a photovoltaic/thermal (PV/T) system. Indoor experimental investigation was conducted on the PV/T system to find the thermally efficient HTF. Carbon quantum dot (C-dot), MXene and MXene/C-dot hybrid NFs were selected for experimentation. Thermo-economic factors (thermal conductivity, volumetric heat capacity, thermal property degradation rate, and cost) were used to optimise the NFs' concentration. Optimized C-dot, MXene, and hybrid NFs were used for experimentation in the PV/T system. Energy, exergy, and enviro-economic analysis was conducted on the PV/T system with each HTFs. The results show that the thermal efficiency of PV/T was enhanced by 5.39, 3.87, and 9.45 % with C-dot, MXene and hybrid NFs, respectively. Hottel-Whillier-Bliss (HWB) analysis was performed on the collector from the generated experimental data. The analysis states that at zero heat loss conditions, the thermal efficiency of the PV/T was enhanced by 5.4 % with the hybrid NF. The maximum CO2 emission from PV/T with C-dot, MXene, and hybrid NFs, were calculated to be around 2.024, 1.979, and 1.931 kgCO2/day, respectively. Emission cost reduction analysis states that the hybrid NF achieved the highest reduction of 0.02 $/day which was a considerable decrement of 13.5 % over the water-based PV/T system.

Research on the impacts of operating frequency at combustion process for opposed single-cylinder free piston generator under direct injection

The opposed single-cylinder free piston generator（OSFPG）has the characteristics of compact structure, variable compression ratio and low emission characteristics of common free piston generator, etc. More, it also has unique features such as high unit power, low vibration noise, and good motion stability, etc. So, in this research, a physical prototype platform based on OSFPG is built. For the key factors, both experiment and simulation have been combined to investigate the changes in OSFPG's work performance under different operating frequencies. It was found that operating frequency affected OSFPG's working characteristics through the entire combustion period. More, the combustion period of each combustion stage increased with the increase of the operating frequency, and the increase amplitude was gradually reduced with the advancing of the ignition advance angle, but the operating frequency affected the after burning period most. When the operating frequency changed from 15 Hz to 35 Hz, the after burning period was extended by at least 100 %. The important thing was that the indicated thermal efficiency of the OSFPG increased first and then decreased with the increase of operating frequency. When the operating frequency was 25 Hz, the OSFPG's indicated thermal efficiency could reach 40.4 %.

Improving the performance of a PCM integrated solar air collector by adding porous fins over the bottom side of the absorber: A transient CFD study

In this study, it is aimed to improve the utilization time period of a solar air collector by integrating a PCM unit. In this context, a PCM unit was integrated to a single-pass solar air collector. Additionally, porous fins were added into the PCM unit in order to shorten PCM melting time. Thus, six different solar collectors were designed and numerically analyzed by adding a storage unit and fins to the collector. A collector without storage and five PCM added collectors with different number of porous fins were studied. In other words, the effect of integrating PCM container and adding porous fins inside the PCM container on various parameters such as utilization time period of the collector, outlet temperature, thermal efficiency and exergy efficiency were investigated. The ANSYS Fluent program was used in numerical analyses. As a result, integrating the PCM unit to the analyzed air collector caused to extend utilization time period of the collector. Adding porous fins into the PCM unit has resulted in a significant increase in the overall performance of the system. In addition, increasing the number of porous fins accelerated the melting process of paraffin. Increasing the number of porous fins was significantly improved average energy efficiency. Average thermal efficiency of the tested collectors was obtained between 38.66 and 41.73 %. In general, as a result of numerical analysis of six different systems, the utilization time was increased by adding the PCM unit to the solar air collector. Moreover, placing porous fins inside the PCM unit increased the performance of the system by accelerating the melting of the paraffin.

Working fluid selection and performance analysis for multistage ship waste heat recovery based on thermal power generation‐organic Rankine cycle combined cycle

AbstractThe energy utilization rate of ships is low, and waste heat accounts for most of the energy loss of the main engine. In this work, a new method called the thermal power generation‐organic Rankine cycle cascaded cycle is suggested to recover ships waste heat in a cascade utilization way. When comparing the performances of R245fa and R1234ze as working fluids, factors such as performance simulation, environmental protection, and safety were taken into account. Based on these simulation, the organic working fluid chosen is R245fa. On the basis of the cascaded cycle, the influence of working fluid flow rates on essential performance parameters, such as power‐production cost, power output, thermal efficiency, and waste heat utilization of main engine flue gas is explored. The experimental system performs at its best for all metrics when the working fluid flow rates is 0.0403 kg/s, including power output of 483.25 W, thermal efficiency of 8.34%, power‐production cost of 0.3464 $/kWh, and waste heat utilization of main engine flue gas of 69.05%.

Energy efficiency of ecological buildings in Tunisia: Natural fiber composites and passive strategies impact

Improving the thermal insulation and energy efficiency of building envelopes is a major objective worldwide and has significantly developed in the recent years. This study aims to evaluate the impact of ecological additive and passive strategies on building energy efficiency. An experimental study was carried out to examine the effect of the incorporation of treated Alfa and Posidonia-Oceanica fibers on the thermal properties of cement and gypsum composite samples. The experimental results were then introduced in a numerical study using TRNSYS software to perform a comparison of the energy efficiency and thermal performance of three individual buildings; two ones constructed with our ecological materials and the third one with typical materials is considered as a reference case under the Tunisian climate. The obtained results indicate that the buildings built with Alfa fibers (BAF) and Posidonia-Oceanica fibers (BPOF) are economically effective since they allow a decrease of about 48.20% and 43.48% in heating, 45.71% and 42.77% in cooling, leading to a reduction in CO2 emission of 47.90% and 43.40%, respectively, in comparison with the reference case. The investigation also focuses on the improvement of the ecological building envelope by a storage wall integrated on the south front and shaded by solar movable overhangs during the summer season. The indoor climate results reveal that incorporating passive strategies into the building improves indoor air temperature and preserves a comfortable indoor relative humidity. Heating requirements decrease by 82.82% for BAF and by 79.76% for BPOF. The cooling requirements of the reference building are also reduced by 63.46% for BAF and 60.45% for BPOF by the use of natural night ventilation (4 ACH) and the appropriate shading for Trombe walls and windows. Consequently, the implementation of passive strategies on the ecological buildings led to a net reduction in CO2 emissions by up to 80.55% for BAF, compared to the reference case.

Enhancement of combustion, performance and emission characteristics of diesel engines fuelled with jatropha-karanja biodiesel using EGM and TGME as additive

The oxygenated additives can improve the physical properties of biodiesel blends to achieve enhanced characteristics of a diesel engine. The present work has investigated ethylene glycol monoacetate (EGM) and tri-ethylene glycol mono-methyl ether (TGME) as potential additives for the jatropha-karanja dual blended biodiesel for improved characteristics of diesel engines. The experiments have been conducted with a single cylinder four stroke diesel engine operating at constant speed of 1500 rpm. The performance, emission and combustion parameters of the engine were investigated with pure diesel, jatropha-karanja dual blended biodiesel having 20 % of methyl ester and the biodiesel added with 2, 4, and 6 % of both the additives respectively. The doping of additives improved the brake thermal efficiency by 4.1 and 4.7 % with brake specific fuel consumption dropped by 0.18 and 0.2 kg/kWh. The additives reduced the hydrocarbon emission by 29.8 % and carbon monoxide by 40 % with a slight increase in NOx emission by 5.2 %. The cylinder pressure attained value near to pure diesel while the heat release rate increased by 12.6 % indicating proper fuel combustion inside the engine cylinder. Thus, the oxygenated additives can suitably be adopted as performance improvers in biodiesel fuels for automotive engines.

Innovative configurations for spherical solar distillation: Ball rotation and preheating for improved productivity

Solar stills are acknowledged as an environmentally friendly desalination method that addresses water scarcity issues in remote areas; however, they contend with a productivity challenge. This work presents a combination of novel arrangements for the spherical solar distiller (RBSD) to augment its productivity. Rotational sphere was anticipated. The influence of speed for RBSD (0, 0.5, 1, 1.5, and 2 rpm) with and without wick was tested. Also, the effect of utilizing a preheater to supply the RBSD with hot feed water under various preheating temperatures, specifically 45, 50, 55, 60, 65, and 70 °C with and without condenser was investigated. Results revealed that the optimized speed is 0.5 rpm and 1 rpm for the RBSD with and without wick, respectively, where the productivity rise reached 62 % and 45 %, respectively. Also, the best preheating temperature that provided the highest performance for RBSD was 65 °C, where the CSD produced 3250 mL/m2.day, while, at 0.5 rpm and 65 °C, the RBSD with a preheater produced 6200 mL/m2.day with an increase in productivity by 91 %. When integrating the external condenser to RBSD with wick and preheater, the productivity of RBSD (6800 mL/m2.day) was augmented by 116 % over that of the CSD (3150 mL/m2.day). Also, the thermal efficiency of CSD and RBSD with wick, preheater and condenser was 32 % and 62 %, respectively. Finally, the cost of distilled water for CSD, RBSD with wick, RBSD with wick and preheater, and RBSD with wick, preheater, and condenser was found to be 0.220$/L, 0.075$/L, 0.055$/L, and 0.030$/L, respectively.

Local entropy generation optimization and thermodynamic irreversibility analysis of oval-shaped coaxial ground heat exchangers: A detailed numerical investigation

Optimizing the heat transfer and thermodynamic efficiency of Ground Heat Exchangers (GHE) is crucial for maximizing the energy efficiency of Ground-coupled Heat Pump (GCHP) systems utilized in building heating and cooling applications. This study pioneers an effective approach of both the first and second laws of thermodynamics of the newly oval-shaped coaxial GHEs (oval-CGHEs), assessing heat transfer, thermohydraulic performance, and local entropy generation rate to explore the optimum design and operational conditions for heat exchange maximization and entropy generation minimization. Utilizing a three-dimensional numerical model validated by experimental results, this study examines the trade-offs between heat transfer improvements and entropy generation rate intensification of the oval-CGHEs in comparison to the typical circular-shaped CGHE (circle-CGHE) further than exploring the effect of key operational and design parameters and performing sensitivity analysis. The results reveal that oval-CGHEs exhibit higher irreversibility as a penalty for their superior heat transfer capabilities compared to traditional circular-shaped CGHEs (circle-CGHE), which can be mitigated by optimizing the position of the inner tube. Moreover, the study underscores the criticality of maintaining a balance between enhanced heat transfer and the associated rise in irreversibility, particularly concerning the factors of mass flow rates and installation depths.

Performance of a solar parabolic trough concentrator using vacuum linear V-shaped cavity receiver

The popularity of renewable energy is on the rise as fossil fuel resources continue to deplete and environmental pollution levels increase. Consequently, enhancing the performance of renewable energy systems has become a compelling subject of research. This study introduces an innovative structure, the Linear Cavity Receiver (LCR), as a receiver for solar Parabolic Trough Concentrators (PTCs). Notably, this novel structure incorporates a vacuum V-shaped LCR, marking a pioneering achievement worldwide. By adopting this configuration, the solar system’s thermal efficiency is enhanced through the reduction of heat losses. The results confirmed the superiority of the vacuum V-shaped LCR over a non-vacuum receiver in optimizing the performance of the solar PTC system. It was found that the vacuum linear V-shaped cavity receiver exhibited superior efficiency for larger cavity tube diameters, higher inlet temperatures, and lower volume flow rates. Moreover, this study showed that decreasing the cavity tube diameter, increasing solar radiation, reducing the working fluid (WF)’s inlet temperature, and raising the volume flow rate contribute to an increase in both cavity heat gain and the solar system’s thermal efficiency. It can be concluded that the thermal efficiency of the solar system was about 72.24 %, 71.6 %, and 69.9 % for cavity tube diameters 5 mm, 10 mm, and 25 mm, respectively. These findings hold great significance in the design of power-generating PTC systems, ensuring their optimal efficiency. Also, the results of this study can be used to improve energy governance by using more efficient thermal power systems.

Comprehensive Review on Technical Developments of Methanol-Fuel-Based Spark Ignition Engines to Improve the Performance, Combustion, and Emissions

Abstract Methanol (CH3OH) is emerging as a viable alternative to fossil-based fuels, addressing the increasing global energy demand while promoting sustainability. The spark ignition (SI) engines are widely used to run the automobile sector. Methanol as a widely available and cheap source of energy can be strongly replaced with expensive and limited fossil-based fuels to power the SI engines. The prime objective of this study is to evaluate the advancements made in improving the fuel blends, performance, combustion, and emission characteristics of methanol-fueled SI engines. The investigation commences by examining the various technical improvements implemented in methanol-fueled SI engines to optimize their overall performance. These developments include advancements in fuel blends, engine design, combustion strategies, fuel injection systems, ignition systems, engine load, etc. The impacts of these developments on the performance parameters including brake thermal efficiency, power output, torque, fuel efficiency, thermal efficiency, etc., combustion parameters including ignition delay, combustion duration, heat release rate, in-cylinder pressure and temperature, etc., emission parameters including hydrocarbon, carbon monoxide, nitrogen oxide, formaldehyde, unburned methanol, etc., is reviewed comprehensively. The effectiveness of emission control techniques and the potential for meeting stringent environmental regulations are explored. The review paper then considers the wider implications of methanol-fueled SI engines by examining their technical, environmental, economic, and renewable applications. The technical aspects cover the compatibility of methanol-fueled SI engines with existing infrastructure and the associated challenges and opportunities. The environmental considerations delve into the potential reduction of greenhouse gas emissions and the overall sustainability of methanol as a renewable fuel. Finally, the research direction of methanol SI engines is discussed, highlighting the emerging trends and prospects in this field. The review paper concludes with recommendations for further research and development, addressing the key areas that require attention to unlock the full potential of methanol as an efficient and sustainable fuel for SI engines.