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Energy consumption in the building sector is responsible for a very large amount of electricity consumption worldwide. The reduction of this consumption is a crucial issue in order to achieve sustainability. The objective of this work is to investigate the use of phase change materials (PCMs) in the building walls in order to reduce the heating and the cooling loads. The novelty of this work is based on the investigation of different scenarios about the position of the PCM layer in the south and the north walls. PCMs can improve the thermal performance and the thermal comfort of a building due to their ability to store large amounts of thermal energy in latent form and so to reduce the temperature fluctuations of the structural components, keeping them within the desired temperature levels. More specifically, this work presents and compares the heating loads, the cooling loads and the temperature distribution of a building in Athens (Greece), with and without PCMs in different positions in the south wall and in the north walls. The simulation is performed with the commercial software TRNSYS 17, using the TRNSYS component: type 1270 (PCM Wall). The results proved that the maximum energy savings per year were achieved by the combination of the insulation and the PCM layer in the north and south walls. More specifically, the reductions in the heating and the cooling loads were found to be 1.54% and 5.90%, respectively. Furthermore, the temperature distribution with the use of a PCM layer is the most acceptable, especially during the summer period. [ABSTRACT FROM AUTHOR]

The exploitation of low-grade heat sources that are available from existing thermal systems processes consists a promising concept for the production of energy. In this research, the integration of an Organic Rankine Cycle (ORC) unit on a supermarket transcritical CO 2 refrigeration system with ejectors is investigated, which is supplied with low-grade heat by the common discharge of the compressors. The optimization analysis proves that for different combinations of CO 2 temperature and pressure in the ORC evaporator, as well as for different ORC condensation temperatures, there is a different optimum ORC evaporation temperature that leads to the highest energy production. Concerning the annual performance analysis conducted for the city of Athens, Greece, operation with isopentane is found to provide the greatest energy production with 10.36 MWh annually, which corresponds to a 3.69% reduction in the refrigeration system's energy consumption. For operation under the ambient temperature of 40 °C, the corresponding reduction of the refrigeration system consumption due to the presence of ORC is 7.54%. Finally, the financial analysis reveals that toluene is the most advantageous solution, leading to a payback period of 3.9 years, with a net present value by the end of the project's lifetime equal to 34.32 k€. • Integration of an Organic Rankine Cycle to a transcritical CO 2 refrigeration system. • Optimization analysis of the system for operation with different working fluids. • Energetic and financial investigation for the case of Athens, Greece. • Isopentane leads to annual production of 10.36 MWh with 3.69% energy savings. • The lowest payback period is 3.9 years and it is achieved for operation with Toluene. [ABSTRACT FROM AUTHOR]

[Display omitted] • Roof thermal insulation results in the maximum (21.9%) yearly electricity savings. • Cool coating induces the highest electricity savings for cooling (50.6%). • Indoor thermal comfort is best achieved with roof insulation for winter and summer. • Thermochromic coating restricts heating penalty but reduces winter thermal comfort. The present study studies the coupling method of building energy simulation and computational fluid dynamics analysis for the detailed and thorough investigation of roof retrofit techniques. The computations are conducted in DesignBuilder software and concern a one-story residential building, equipped with air-to-air heat pump split units, located in Athens, Greece. The retrofit actions aim at the improvement of the building rooftop thermal and optical properties and include i) the addition of external thermal insulation, ii) the addition of phase change material on the exterior surface, iii) the application of cool coating, and iv) the application of thermochromic coating. The aforementioned techniques are examined as standalone retrofit actions. The yearly heat pump electricity consumption and the local and mean surface thermal comfort indexes of predicted mean vote and predicted percentage of dissatisfied, for a typical winter and summer afternoon hour, are calculated and compared. The importance of the present study lies in the combination of energy simulation and thermal comfort analysis for the multi-criteria assessment and selection of the most suitable roof retrofit technique. Additionally, the evaluation of the indoor thermal environment with the integration of various passive roof retrofit techniques is not adequately investigated in the existing literature. The application of cool roof coating results in the maximum electricity savings for cooling (50.6%), whereas the addition of thermal insulation in the maximum decrease in electricity consumption for heating (21.9%) and total (18.4%). Furthermore, the application of thermochromic roof coating restricts the heating penalty at 6.3% in contrast to the cool coating (42.0%) but increases the predicted percentage of dissatisfied by 170% compared to the baseline scenario, during the examined afternoon winter hour. Lastly, every examined retrofit technique results in a comparable improvement in thermal comfort conditions for summer, undermining the energy advantages of the cool and thermochromic roof coatings, against the energy and thermal comfort effectiveness of the retrofit action of insulation. [ABSTRACT FROM AUTHOR]

• A solar-driven polygeneration unit with CO 2 as the working fluid is investigated. • Initial optimization in steady-state conditions and secondary dynamical analysis. • The payback period is found to be around 6.4 years and the total efficiency is 55%. • The use of an extra ORC can be used for enhancing electricity production. • The exergy efficiency with ORC is found 23.63%, while without 23.37%. The object of this study is the investigation of polygeneration plants utilizing solar energy in order to produce power products on the scale of a few MW. Parabolic trough collectors are used in order to exploit solar irradiation and to provide the generated heat to the polygeneration/trigeneration cycle in a high-temperature range (500–570 °C). The plants under consideration additionally consist of a storage tank, a Brayton cycle with s-CO 2 , a LiBr-H 2 O absorption chiller and also the installation of a suitable thermodynamic organic Rankine cycle (ORC) cycle is examined in order to utilize waste heat for further power generation. The systems are first investigated for operation under steady-state conditions and then for dynamic conditions on an annual basis. Based on the final annual results of the plants, the plant in which ORC was not used shows annual electrical, exergy and energy efficiencies equal to 18.33%, 23.37% and 54.91% respectively, while the plant in which ORC was used similarly shows 19.05%, 23.63% and 49.00%. According to economic analysis, the payback period was found at 6.37 years without ORC and 6.51 years with ORC. Taking into account the operational and techno-economic results of the plants it can be concluded that the plants produce satisfactory energy products ensuring also the economic viability of the investment. [ABSTRACT FROM AUTHOR]

The heat transfer and flow characteristics of water-based fly ash nanofluid for concentrations of 0.1–1.5 vol.% that flow through a copper tube at an inlet fluid temperature of 303 K with constant heat flux boundary conditions are estimated numerically. Stability, viscosity, and thermal conductivity of fly ash nanofluid have been determined experimentally and compared with correlations available in the literature. STAR CCM + software was used to solve the governing equations using the finite volume method (FVM). Water and stable fly ash nanofluid were used as working fluids for the Reynolds number range of 4500–16,000. The Nusselt number and friction factor at 1.5% volume concentration are greater than the base fluid by 36% and 9.4%, respectively. The fly ash nanofluid showed a performance index (η ) value of more than 1 at all concentrations undertaken, indicating that the use of fly ash nanofluid in heat transfer applications is beneficial. The highest η value is determined to be 1.5 approximately for a nanofluid concentration of 1.5 vol.%. The fly ash nanofluid exhibits enhanced heat transfer performance contrasted to SiO2 nanofluid. The utilization of fly ash particles for heat transfer enhancement can aid in the reduction of environmental pollution to a certain extent. Novel correlations are suggested for the estimation of fly ash nanofluid Nusselt number and friction factor. [ABSTRACT FROM AUTHOR]

In the past decade, nanotechnology's rapid developments have created quite a lot of prospects for researchers and engineers to check up on. And nanofluids are important consequences of this progression. Nanofluids are created by suspending nanoparticles with average diameters below 100 nm in conventional heat transfer carriers such as water, oil, ethylene glycol, etc. Nanofluids are considered to offer substantial advantages over usual heat transfer fluids. When dispersed in a uniform way and suspended stably in the base fluids, a minimal amount of nanoparticles can significantly improve the thermal properties of host fluids. Present work attempts to address this challenge considering state-of-the-art advances in understanding, discussing, and mitigating problems about nanofluids' stability. Stable and highly conductive nanofluids are produced by generally, one-step and two-step production methods. Both approaches suffer from problems with the nanoparticles' agglomeration to be an important one. Thus, numerous numerical models and the principal physical phenomena affecting the stability (fundamental physical principles that govern the interparticle interactions, clustering and deposition kinetics, and colloidal stability theories) have been analyzed. Concerning the particles' dynamic motion, the significance of different forces in nanofluid in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, Van der Waals, electrostatic double-layer forces are investigated. Furthermore, an overview of nanofluids' thermophysical properties, physical models, and heat transfer models is​ included in this work. In order to realize the unexpected discoveries and overcome classical models' limitations, several researchers have suggested new physical concepts and mechanisms, and they have created new models to enhance the transport properties. This review study includes numerous aspects of the nanofluids' science by investigating applications, thermal properties and giving critical chronological milestones about the nanofluids' evolution. Also, the present review discusses in detail various modeling and slip mechanisms for the heat transfer of nanofluids. Potential novel 2D materials as nanofluids have also been discussed and reported. A brief overview of the potential applications utilizing nanofluids has been reviewed, and future research gaps have been reported. Furthermore, recommendations were extracted regarding current scientific gaps and future research directions to cover the physical phenomenon, stability, thermophysical properties, overview of some applications, and the limitations hindering these nanofluids' deployment. The review is presumed to be valuable for scholars and researchers working in the area of numerical simulations of nanofluids and experimental aspects and help them understand the fundamental physical phenomena taking place during these numerical simulations and experiments and explore the potential of nanofluids both in academia and industry. [Display omitted] [ABSTRACT FROM AUTHOR]

A Crossflow turbine is a device used to generate power from hydro, which is a renewable source of energy. The salient feature of this turbine is its simplicity in construction. In the past few decades, variables such as flow diverter, air holes, bidirectional flow were introduced in the turbine design to improve its efficiency. This paper presents a comprehensive review of the performance of the cross flow turbine. The review of literature is classified into experimental and numerical studies. The present study highlights the optimum range of geometrical variables required for the efficient design of a cross flow turbine. The study also emphasizes the importance of employing the cross flow turbine in remote places where run-of-river hydro power plants are feasible, as it provides a low-cost energy solution. The outcome of the present study will help the researchers to identify the research gap based on the present status of work done and to improve the performance of the cross flow turbine further in the future. • Experimental investigations on the performance of cross flow turbine is reviewed. • Numerical investigations carried out by several researchers is presented. • Performance of the cross flow turbine with varying geometrical parameters is analyzed. • Research gap and the scope for future work are discussed. [ABSTRACT FROM AUTHOR]

• Solar-biomass supercritical CO 2 trigeneration system is studied. • Energetic analysis and selection of optimal conditions for the proposed unit. • Assessment of financial viability for installation in refrigeration application. • Determination of performance results for annual operation in Athens climate. • Production of 185.59 MWh yearly with at least 519 k€ savings during the lifetime. The ever-growing increase of the energy demand required to satisfy the needs of society has aroused considerable interest regarding the investigation of polygeneration systems that employ renewable energy sources. In the present work, the concept of installing a supercritical CO 2 trigeneration system to cover the needs of a refrigerated warehouse in Athens with simultaneous production of power and heating is studied in terms of energy performance, and its financial benefits compared to the solution of an ejector refrigeration-only system are analyzed and assessed. The trigeneration system utilizes solar energy in parabolic trough collectors and biomass energy as the supplementary source, in order to increase the temperature of high-pressure CO 2 and produce power in the turbine which is coupled to a generator. Regarding the collectors, the installation of zero up to four solar modules that exploit the solar power is examined, while the rest energy input needed in order to achieve the selected operating conditions is supplied by a biomass boiler. Since all the trigeneration cases require the same amount of energy input to reach the desired conditions, the trigeneration system for every combination of solar modules is found to produce 185.59 MWh annually, while the refrigeration-only system is found to consume 172.94 MWh during a year. The power production efficiency, the combined power and refrigeration production efficiency and the total trigeneration efficiency for the selected nominal conditions are calculated 11.77 %, 66.09 % and 163.70 % respectively. The case of a trigeneration system with four solar collectors displays a payback period of 4.0 years compared to the refrigeration-only case, providing financial savings equal to 542 k€ for the duration of the project lifetime. The same case compared to that of trigeneration system using only biomass boiler and no solar collectors exhibits payback period of 13.5 years, achieving financial savings of 22.9 k€ for the considered lifetime of the project. [ABSTRACT FROM AUTHOR]

The goal of the present paper is the investigation of a solar desalination system with an organic Rankine cycle system for power and freshwater production. This system is an environmentally friendly technology that is able to utilize solar energy properly in a novel cogeneration application. A parabolic trough concentrator with a smooth and corrugated receiver was employed as the heat source of the desalination system. A humidifier–dehumidifier desalination technology was used for producing freshwater. The electricity is produced by an organic Rankine cycle which is fed both by the solar field and by the hot brine. The present analysis is performed by using a detailed numerical model which is validated by experimental literature data. Based on the final results, the corrugated tube has a maximum performance of 66.59%, and it is more efficient than the smooth tube with 63.11%. The average freshwater productions were estimated equal to 13.09 kg hr−1 and 12.71 kg hr−1 for the corrugated and smooth tubes, respectively. The maximum net work production is found at 7.57 kW with R113, while the less efficient working fluid is R134a. It was found that the application of the developed desalination system leads to the production of high amounts of fresh water and a significant reduction of the equivalent CO2 emissions. [ABSTRACT FROM AUTHOR]

In this study, a solar parabolic trough concentrator (PTC) was evaluated as a heat source of a power generation system based on energy (E1), exergy (E2), environmental (E3), and economic (E4) analyses. Various configurations of power generation systems were investigated, including the solar SRC (SRC) and solar ORC (ORC). Water and R113 were used as heat transfer fluids of SRC and ORC system, respectively. It should be mentioned that the proposed solar systems were evaluated for providing the required power of a mobile house in an emergency condition such as an earthquake that was happened in Kermanshah, Iran, in 2016 with many homeless people. The PTC system was optically and thermally investigated based on sensitivity analysis. The optimized PTC system was assumed as a heat source of the RC with two various configurations for power generation. Then, the solar RC systems were investigated based on 4E analyses for providing the power of the mobile house based on various numbers of solar RC units. It was concluded that the solar SRC system could be recommended for achieving the highest 4E performance. The highest value of its energy efficiency was found at 24.60% and of his exergy at 26.37%. On the other hand, the ORC system has energy and exergy efficiencies at 17.64% and 18.91%, respectively, which are significantly lower than the efficiencies of the SRC system. The optimum heat source temperature for the SRC system is found at 650 K, while for the ORC system at 499 K. Moreover, the best economic performance was found with the SRC system with a payback period of 7.47 years. Finally, the CO2 mitigated per annum ( φ CO 2 ) was estimated at 5.29 (tones year−1), and the carbon credit ( Z CO 2 ) was calculated equal to 76.71 ($ year−1). [ABSTRACT FROM AUTHOR]

A comprehensive review of cylindrical two-phase closed thermosyphon for low-temperature applications is presented in this paper. The review of literature based on the experimental studies of two-phase closed thermosyphon is categorized according to the utilization of refrigerants, nanofluids, external parameters, surface coating and modifications in the design of two-phase closed thermosyphon to provide a useful reference to the researchers in the field of cylindrical two-phase closed thermosyphon. The effect of geometrical parameters, power input, working fluid, inclination angle and fill ratio on the performance of thermosyphon has been studied thoroughly. The outcome of this review paper would help the research community to enhance the thermal efficiency of cylindrical two-phase closed thermosyphon. It would emphasize the need for utilization of environment-friendly refrigerants in two-phase closed thermosyphon, powered by a solar photovoltaic system, as these two would not affect the environment. v kinematic viscosity, m2s−1 [ABSTRACT FROM AUTHOR]

Solar energy is an auspicious renewal energy source because of its abundant availability and its flexibility to be converted into heat or into electricity. Concentrated solar power technologies are promising units for producing electricity in large scale applications and parabolic trough solar collector is the most matured technology for these plants. The objective of this paper is to summarize and to discuss the current status of parabolic trough collector commercial power plants around the world and the technological developments in various constituents of such concentrated solar power plants. More specifically, this review includes various developments in the concentrators and receiver tubes in order to enhance both the thermal and the optical efficiencies. Moreover, the different existing and newly developed heat transfer fluids are discussed in this work and the emphasis is given in the discussion of the different operating temperature levels, the storage system and the applications that use different fluids. Furthermore, different tracking options of the parabolic trough solar collector are examined, different storage technologies, as well as various power cycles and their modifications to enhance the overall efficiency of the parabolic trough collector-based power plants are discussed in detail. The final conclusions of this work indicate the recent developments and the future designs of the parabolic trough solar collector power plants. [ABSTRACT FROM AUTHOR]

The use of renewable energies including hydropower energy is growing throughout the world. Among the existing hydropower technologies, small-scale hydropower technologies are popular due to easy accessibility and availability in different locations. Recently, Archimedes Screw Turbines (ASTs) as a new technology have been considered. The main objective of this research is the structural optimization of an AST for substituting in irrigation canals instead of existing check structures. For this purpose, the AST performance model was numerically developed for screw performance optimization in MATLAB 2013a environment. The developed model was validated using experimental data. Different structural parameters were optimized to design an appropriate AST for replacing instead of check drop-1 in the east Aghili canal in Khuzestan province (Iran). The canal was simulated using the ICSS hydrodynamic model. The results of the developed model showed a good agreement with reported experimental data. The highest efficiency was obtained 90.83% for the screw length of 6 m, the inclination angle of 20°, and the flight number of 1 at the design flow rate. Based on the findings, the suggested system can be used instead of the canal structures without considerable change in the hydraulic and performance of the canal. • Numerical Optimization Study of Archimedes Screw Turbine (AST) was considered to generate energy from flowing water. • The numerical modeling wad implemented in MATLAB. • Simulation modeling was implemented in FORTRAN. • Aghili east irrigation canal was used. • The mechanical power and efficiency at the optimum point were obtained 19.90 kW and 90.83%, respectively. [ABSTRACT FROM AUTHOR]

In this study, the thermal performance of a solar dish concentrator with different cavity receivers and nanofluids was experimentally studied. The first step in this work is a detailed literature review of the studies about the solar dish cavity receivers. The second step is the experimental investigation of a solar dish concentrator with a cubical cavity receiver using Al 2 O 3 /oil nanofluid and pure thermal oil. The last step of this work is the comparison of the found results with others from the literature in order to make an overall overview of cavity receivers. The finally presented results of the dish concentrator with different cavity receivers (including cubical, cylindrical, and hemispherical cavities) using different nanofluids (including Al 2 O 3 /oil, MWCNT/oil, and SiO 2 /oil nanofluids are reported based on a same experimental setup that was designed and built by authors of this research. The results reveal that the hemispherical and the cubical cavities are the most effective designs, while the cylindrical cavity presents lower performance. Moreover, it was found that the use of nanofluids always leads to thermal performance enhancement. More specifically, it was found that the mean thermal efficiency enhancement with the use of nanofluids is 12.90% with the hemispherical cavity, 5.84% with the cubical cavity and 1.44% with the cylindrical cavity. • A cubical cavity receiver was experimental investigated using Al 2 O 3 /oil nanofluid. • Performance comparison was conducted with pure oil and nanofluid. • Performance comparison of cubical, cylindrical, and hemispherical cavities was presented. • A detailed literature review related to the cavities and nanofluid was conducted. • The highest mean thermal efficiency enhancement was calculated equal to 12.90% using hemispherical cavity and nanofluid. [ABSTRACT FROM AUTHOR]

Advanced heat removal technologies are critical for high-performance automotive engines. The conventional fluids being used today are based on a mixture of distilled water (DW) and ethylene glycol (EG), which widens the operational temperature range but at the same time limits the heat removal. Therefore, the use of nanofluids for improving heat transfer performance has soared over the past few years. The problem is that most of the reports highlight the short-term heat transfer results which may not be true over time. In this paper, a suggested best practice for analyzing the usage of nanofluids in heat transfer applications is presented, specifically for an actual car radiator. This work investigates the use of aluminum oxide (Al 2 O 3) and titanium dioxide (TiO 2) nanoparticles dispersed in DW and EG at 50:50 volumetric proportions. The choice of these oxide-based nanofluids is motivated by their anti-corrosive properties that are usually not analyzed or discussed in most of the articles. Furthermore, the emphasis is given on the presentation of a comprehensive characterization of the nanofluids including thermophysical properties (size, density, viscosity, thermal conductivity, corrosive behavior) and long-term stability (zeta potential) which are essential for an end-user to have. The results showed a maximum enhancement of the thermal performance by 24.21% using Al 2 O 3 at a volume fraction of 0.3%. Friction factor and performance evaluation criterion (PEC) for the radiator experiments are calculated in order to determine the penalty in the pressure drop and to evaluate it properly. Finally, it is found that the values of PEC lie in the range of 1.03–1.31 which indicates significant flow enhancement. • A critical review on stability and application of nanofluids (NFs) in a radiator is presented. • The effect of surfactant concentration on stability is investigated. • Thermophysical properties of Al 2 O 3 –DW/EG and TiO 2 -DW/EG NFs are experimentally investigated. • Effect of NFs with respect to corrosion for the pipping system of the radiator is investigated. [ABSTRACT FROM AUTHOR]

The concentrating solar systems of linear Fresnel reflectors offer the ability to generate electricity from solar energy. The main objective of this paper is to perform a transient numerical simulation on a linear Fresnel solar reflector directed to produce superheated water steam for the power plants, in order to determine its efficiencies (optical and thermal), where the heat transfer fluid mass flow inside the copper absorber tube is 0.045 kg/s. The dimensions of the studied linear Fresnel solar collector are the same dimension as the modular system Nova-1 of NOVATEC SOLAR Company. The dimension of the studied model is 1D. For this purpose, El-Oued region has been designated as a study field. The twelve recommended average days for months have been selected for the study. This paper was based on a numerical solution using the finite differences method. MATLAB has been used as a software language. The optical efficiency of the LFR solar receiver has reached 53.7% where the thermal efficiency has reached 37.5%, while the pressure drop within the absorber pipe has reached 02 bars. As for superheated steam temperatures variations, it ranged between 233.35 °C and 263.75 °C, knowing that the water steam inlet temperature when entering the absorber tube is equal to 140 °C. As for the overall coefficient of heat loss, its mean value is 5.84 W/m2.°C. The results obtained are very encouraging to invest in this steam power plant, especially in the desert areas, which are rich in solar energy. Image 1 • Optical efficiency of the solar reflector obtained was 53.7% • Thermal efficiency of the solar reflector achieved was 37.5% • An annual electricity capacity of more than 2000 MW can be produced • This technique is 100% clean and has no negative environmental impact [ABSTRACT FROM AUTHOR]

Highlights • A solar organic Rankine Cycle was considered using dish collector as the heat source. • The performance of three cavity receivers was modeled and compared. • A hemispherical cavity receiver was experimentally investigated. • Alumina/thermal oil was investigated as the solar working fluid. • The system was evaluated at different sizes and concentrations of nanoparticles. Abstract The objective of this work is the investigation of a solar-driven organic Rankine cycle with nanofluid-based solar dish concentrator. Three different cavity receivers are tested with the alumina/oil nanofluid in order to determine the most effective choice. More specifically, the examined cavities are hemispherical, cubical, and cylindrical, while the organic Rankine cycle is a non-regenerated system with superheating, R601 working fluid and heat rejection temperature at 310 K. The analysis is perfumed using the first and the second thermodynamic laws. The organic Rankine cycle is investigated for different pressure in the turbine inlet and different nanoparticle concentrations are also studied. According to the results, the thermal performance of the cavity and the electricity production are improved by decreasing alumina nanoparticle size, and by increasing the nanofluid concentration. Moreover, the optimum pressure in the turbine inlet was found at 2 MPa. Finally, the hemispherical cavity receiver has been found to be the best choice with cubical to be the second one and the cylindrical to be the less effective choice. [ABSTRACT FROM AUTHOR]

Abstract The objective of this work is the investigation of two oil-based nanofluids in a hemispherical cavity receiver of a solar dish concentrator. The investigated nanofluids are Alumina/oil and Silica/oil, while the used oil is the Behran thermal oil. The two nanofluids are examined experimentally and they are energetically and exergetically compared in order to determine their performance in the solar system. Thermal performance of the hemispherical cavity receiver was studied in the steady-state condition. The results elucidated that the average cavity thermal performance has improved with the application of Alumina/oil nanofluid compared to the application of Silica/oil nanofluid, and pure oil as the solar heat transfer fluid. It was found the lower heat loss coefficient of the hemispherical cavity receiver could be achieved using the Alumina/oil nanofluid than the Silica/oil nanofluid and pure oil as the solar working fluids. Three models were presented for cavity thermal performance versus the parameter T i n − T a m b I b e a m using investigated nanofluids, and base fluid. Exergy efficiency and overall thermal efficiency of the hemispherical cavity receiver was highest using Alumina/oil nanofluid than two other investigated heat transfer fluids. Finally, it was concluded that hemispherical cavity receiver with Alumina/oil nanofluid is the best selection from the energy and exergy viewpoint. Highlights • It was an experimental study of nanofluids in a solar dish collector. • A hemispherical cavity receiver was used as the dish absorber. • Al 2 O 3 /thermal oil and SiO 2 /thermal oil nanofluids were tested. • Performance of the nanofluids was compared with the pure oil. • Three thermal efficiency models were suggested for the nanofluids and the pure oil. [ABSTRACT FROM AUTHOR]

This paper presents the initial results from a project entitled "TRiTON", funded by the Greek Ministry of Education, which addresses safety issues of Liquefied Natural Gas (LNG) at ports. Whithin this framework, a stakeholder analysis is performed for investigating the safety management operation during storage, transport, and supply of LNG at port areas. The national (Greek), the European and the international regulatory framework for LNG safety have been analysed, so as to identify relevant stakeholders and establish relationships between them. Relationships have been weighted by a group of experts to highlight the importance of some critical interactions in safety management. The social network analysis approach has been employed for creating three stakeholder networks for the most widely used methods for LNG storage and bunkering, namely: a) fixed-tank storage and tank to ship bunkering, b) truck to ship bunkering, and c) ship to ship bunkering. Statistics and metrics of the networks have been calculated, with the help of the open-source software called Gephi, such as density, centralities (degree, closeness and betweenness), clustering coefficient and modularity. Finally, the most important stakeholders for handling LNG safety at ports have been identified. [ABSTRACT FROM AUTHOR]

The organic Rankine cycle (ORC) is an effective technology for power generation from temperatures of up to 400 °C and for capacities of up to 10 MW el. The use of solar irradiation for driving an ORC is a promising renewable energy-based technology due to the high compatibility between the operating temperatures of solar thermal collector technologies and the temperature needs of the cycle. The objective of this review paper is to present and discuss the operation principles of solar-ORC technology and the wide range of solar-ORC systems that have been studied in the literature. Various solar thermal technologies that can drive the ORC are investigated, such as the flat plate collector, evacuated tube collector, compound parabolic collector, parabolic trough collector, linear Fresnel reflectors, dish concentrators and solar towers. Both simulation studies and experimental investigations are included in the study. Hybrid systems and different thermal storage techniques are also examined in detail. Moreover, systems with ORC which produce many useful outputs such as cooling, heating and fresh water are studied because they present high sustainability indexes. The limitations of the technology are also highlighted, along with critical suggestions aimed at steering future research in this field. The final conclusions indicate that the development of trigeneration and polygeneration systems with ORC sub-systems is a promising avenue, not only for the future development of solar-ORC technology but also for the development of renewable and sustainable energy systems in a broader context. • Solar driven organic Rankine cycles are summarized and discussed in detail. • Concentrating and non-concentrating solar thermal systems are included. • Parabolic trough collector is the best solar technology for power production. • The use of solar organic Rankine cycles in polygeneration is a promising idea. • There is a need for conducting future experimental studies in a great scale. [ABSTRACT FROM AUTHOR]

• Latest developments in solar thermal applications using nanofluids are reviewed • Low to medium temperature solar collectors are summarized • Improvements in solar collectors using nanofluids as working fluid is compiled • Application of solar collectors in buildings is reviewed The efficient exploitation of solar irradiation is one of the most encouraging ways of handling numerous environmental concerns. Solar collectors are suitable devices that capture solar irradiation and convert it into thermal energy and electricity. In the last years, the nanofluids used in solar thermal systems have been studied as a useful technique for enhancing the solar collectors' performance and establishing them as viable and highly efficient systems. The present review paper aims to summarize and discuss the most important numerical and experimental studies in nanofluid-based solar systems for application at low and medium temperature levels, while the emphasis on the fundamental physical phenomena that occur. In the first part, numerous numerical models and the principal physical phenomena affecting the heat transfer rate in the nanofluid have been analyzed. More specifically, the importance of different forces in nanofluid flows that exist in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, Van der Waals, electrostatic double-layer forces are considered. Moreover, an overview of the thermophysical properties, physical models, heat transfer models, and evaluation criteria of nanofluids are included in this work. In the second part, which is the main part of this work, a comprehensive review is performed to gather and discuss the new advantages in the nanofluid-based solar collectors that operate at low and medium temperatures. More specifically, the examined solar systems are the flat plate collectors, the evacuated tube collectors, the direct absorption collectors, and the thermal photovoltaic systems, while the investigated applications are space-heating, space-cooling, household hot water production, desalination, industrial activities, and power generation. The aforementioned collectors and applications are the most usual in the real systems, indicating the importance of the present work. Moreover, the emphasis is given in the thermal, exergy, economic, and environmental evaluation of the studied systems, as well as in the discussion of the possible limitations of the use of nanofluids like the lack of long-term stability, the agglomeration of nanoparticles, and the increased pumping work due to the increased pressure drop. Finally, it is found that the nanofluid utilization usually enhances the collector efficiency up to 5%, while higher enhancements can be found in thermal photovoltaics. Moreover, it is concluded that there is a need to emphasize issues such as stability and the use of eco-friendly solar systems. Lastly, the field's future trends are highlighted, and a clear image of the present situation and the next steps in the field are given. [ABSTRACT FROM AUTHOR]

Refrigeration systems and heating/air conditioning units used in supermarkets are responsible for a great part of the annual electricity consumption of industrialized countries. Taking also into consideration the direct emissions of carbon dioxide to the environment due to leakage of refrigerants with high Global Warming Potential that are employed today for such applications, a step towards more environmentally friendly and less energy-consuming solutions should be made. In the current research, different topologies of an all-in-one R744 transcritical unit providing refrigeration, heating and air conditioning to a real Greek supermarket store (METRO S.A.) in Athens are studied, using the softwares Engineering Equation Solver and EnergyPlus. The different configurations include a state-of-the-art R744 system with parallel compression and multi-ejector block, the same system with the addition of a subcooling heat exchanger that utilizes available geothermal water, as well as the last described unit with the integration of adiabatic cooling configuration on the gas cooler. These solutions are investigated in terms of energy efficiency and environmental impact (total equivalent warming impact) and they are compared to an indirect arrangement employing R744 and R290, to conventional direct expansion solutions (with R448A or R404A) and to a heat pump employing R410A that covers the heating and air conditioning demands of the supermarket. The comparative energy analysis was separated into the refrigeration part, the heating and air conditioning part and the sum of them. The results indicated that for the climate of the store's location, the case including the subcooler and adiabatic cooling configuration, the case with only the subcooler and the case with neither the subcooler nor the adiabatic cooling configuration consume annually 20.9%, 17.6% and 8.7% less energy respectively than the combination of a refrigeration unit with R448A and a heat pump with R410A for the heating/cooling needs. • All-in-one CO 2 units for refrigeration, heating and air conditioning are studied. • Supermarket refrigeration units using CO 2 and conventional refrigerants are compared. • The use of adiabatic cooling and subcooler employing geothermal water is studied. • The most advanced CO 2 system consumes 20.9% less energy than the conventional system. • The most advanced CO 2 system emits 34.7% less eq.CO 2 tn than a conventional unit. [ABSTRACT FROM AUTHOR]

• A parabolic trough collector with a linear V-Shape cavity receiver was studied. • The V-Shape cavity receiver was coupled with an organic Rankine cycle system. • The solar organic Rankine cycle system was evaluated exergetically and financially. • The optimum turbine inlet temperature is 592 K and the optimum pressure 6 MPa. • The simple payback period was found close to 6.01 years for the large scale setup. In this research, a parabolic trough concentrator with linear V-Shape cavity receiver was studied as the heat source of an organic Rankine cycle system. The solar organic Rankine cycle system was evaluated under exergy and economic analyses. Thermal oil was used as the solar working fluid, and ethanol was used as the organic working fluid under different turbine inlet temperatures and turbine inlet pressure. The influence of different operational parameters, including solar radiation, mass flow rate, and inlet temperature of solar working fluid was investigated on the performance of the solar organic Rankine cycle system. It was found that exergy gain and exergy efficiency of the solar system improved with increasing solar radiation, increasing inlet temperature, and decreasing the flow rate of the solar working fluid. The highest organic Rankine cycle efficiency and total efficiency were found to be 35%, and 25% at turbine inlet temperature of 592 K and turbine inlet pressure of 6 MPa, respectively. Finally, the lowest levelized cost of electricity, and the lowest payback period were calculated equal to 0.0716 (€/kWh), and 8.79 (years) for the optimum condition of the developed solar organic Rankine cycle system, respectively. The present study is beneficial for improving the performance of the solar organic Rankine cycle systems with parabolic trough concentrators in a simple and convenient way and the development of solar thermal technologies. [ABSTRACT FROM AUTHOR]

Human genetic studies of critical COVID-19 pneumonia have revealed the essential role of type I interferon-dependent innate immunity to SARS-CoV-2 infection. Conversely, an association between the HLA-B∗15:01 allele and asymptomatic SARS-CoV-2 infection in unvaccinated individuals was recently reported, suggesting a contribution of pre-existing T cell-dependent adaptive immunity. We report a lack of association of classical HLA alleles, including HLA-B∗15:01, with pre-omicron asymptomatic SARS-CoV-2 infection in unvaccinated participants in a prospective population-based study in the United States (191 asymptomatic vs. 945 symptomatic COVID-19 cases). Moreover, we found no such association in the international COVID Human Genetic Effort cohort (206 asymptomatic vs. 574 mild or moderate COVID-19 cases and 1,625 severe or critical COVID-19 cases). Finally, in the Human Challenge Characterisation study, the three HLA-B∗15:01 individuals infected with SARS-CoV-2 developed symptoms. As with other acute primary infections studied, no classical HLA alleles favoring an asymptomatic course of SARS-CoV-2 infection were identified., Competing Interests: Declaration of interests E.T.C., K.M.S.B., and A.B. are employees of Helix., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

We describe a novel, severe autoinflammatory syndrome characterized by neuroinflammation, systemic autoinflammation, splenomegaly, and anemia (NASA) caused by bi-allelic mutations in IRAK4 . IRAK-4 is a serine/threonine kinase with a pivotal role in innate immune signaling from toll-like receptors and production of pro-inflammatory cytokines. In humans, bi-allelic mutations in IRAK4 result in IRAK-4 deficiency and increased susceptibility to pyogenic bacterial infections, but autoinflammation has never been described. We describe 5 affected patients from 2 unrelated families with compound heterozygous mutations in IRAK4 (c.C877T (p.Q293*)/c.G958T (p.D320Y); and c.A86C (p.Q29P)/c.161 + 1G>A) resulting in severe systemic autoinflammation, massive splenomegaly and severe transfusion dependent anemia and, in 3/5 cases, severe neuroinflammation and seizures. IRAK-4 protein expression was reduced in peripheral blood mononuclear cells (PBMC) in affected patients. Immunological analysis demonstrated elevated serum tumor necrosis factor (TNF), interleukin (IL) 1 beta (IL-1β), IL-6, IL-8, interferon α2a (IFN-α2a), and interferon β (IFN-β); and elevated cerebrospinal fluid (CSF) IL-6 without elevation of CSF IFN-α despite perturbed interferon gene signature. Mutations were located within the death domain (DD; p.Q29P and splice site mutation c.161 + 1G>A) and kinase domain (p.Q293*/p.D320Y) of IRAK-4. Structure-based modeling of the DD mutation p.Q29P showed alteration in the alignment of a loop within the DD with loss of contact distance and hydrogen bond interactions with IRAK-1/2 within the myddosome complex. The kinase domain mutation p.D320Y was predicted to stabilize interactions within the kinase active site. While precise mechanisms of autoinflammation in NASA remain uncertain, we speculate that loss of negative regulation of IRAK-4 and IRAK-1; dysregulation of myddosome assembly and disassembly; or kinase active site instability may drive dysregulated IL-6 and TNF production. Blockade of IL-6 resulted in immediate and complete amelioration of systemic autoinflammation and anemia in all 5 patients treated; however, neuroinflammation has, so far proven recalcitrant to IL-6 blockade and the janus kinase (JAK) inhibitor baricitinib, likely due to lack of central nervous system penetration of both drugs. We therefore highlight that bi-allelic mutation in IRAK4 may be associated with a severe and complex autoinflammatory and neuroinflammatory phenotype that we have called NASA (neuroinflammation, autoinflammation, splenomegaly and anemia), in addition to immunodeficiency in humans., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Cooray, Price-Kuehne, Hong, Omoyinmi, Burleigh, Gilmour, Ahmad, Choi, Bahar, Torpiano, Gagunashvili, Jensen, Bellos, Sancho-Shimizu, Herberg, Mankad, Kumar, Kaliakatsos, Worth, Eleftheriou, Whittaker and Brogan.)