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Solar photovoltaic (PV) cells have emerged as the primary technology for producing green electricity. This innovation harnesses direct sunlight to generate power and its flexibility of installation has drawn significant investment in PV panels. Despite numerous benefits, these cells are hindered by a decline in efficiency caused by elevated cell temperature. As such, researchers have undertaken extensive investigations into possible solutions aimed at enhancing the performance of photovoltaic cells using diverse techniques. This review paper provides a thorough analysis of cooling techniques for photovoltaic panels. It encompasses both passive and active cooling methods, including water and air cooling, phase-change materials, and various diverse approaches. Within each category, it delves into detailed sub-categories, such as evaporative cooling, water immersion, floating systems, water pipes, cooling channels, water sprayers, jet impingement, geothermal cooling, and natural convection enhanced by PV designs. It also covers forced convection using cooling ducts, heat sinks, and air collectors, alongside the integration of Phase Change Materials (PCMs), nanofluids, radiative cooling, thermoelectric methods, heat pipes, heat pumps, and other innovative techniques. Each of these approaches is illustrated with specific schematics and thoroughly discussed and compared. Furthermore, this paper introduces an original classification system for these cooling methods applied to photovoltaic panels, offering valuable guidance for future research and insights into improving efficiency.

This paper investigates the potential of utilizing air-conditioning (AC) system exhaust to cool Photo Voltaic (PV) panels, leading to improved efficiency. Additionally, the study explores harnessing the heat emitted from the PV modules for thermal applications. Numerical simulations demonstrate that this cooling method can enhance PV module efficiency by 5% to 50% compared to non-cooled scenarios. Moreover, the recovered hot air leaving the PV panels is directed to a dishwasher for drying purpose, thereby optimizing the overall energy utilization of the proposed system. An energetic and exergetic analysis of the recuperated thermal energy showcases its exceptional thermal efficiency, ranging from 98% to 45%, which aligns with values reported in existing literature. The exergetic efficiency of the suggested system falls between 5.2% and 1%, consistent with the range of values documented in previous studies. By exploiting AC system exhaust and waste heat, this new approach can significantly enhance the performance of PV panels and promote energy efficiency. Implementing this technology could prove instrumental in sustainable energy applications.

Electricity is a critical component of many everyday activities, demanding continuing research to create new or improved techniques for generating electrical power. Thermoelectric generators (TEGs), which work basically on the Seebeck effect can successfully transform input heat from numerous applications into valuable electrical energy, as well as power electronic devices and sensors on their own. However, obstacles include increasing the temperature difference and creating novel materials to improve electrical output and efficiency. Accordingly, this paper discusses these problems by providing a thorough examination of available strategies to enhance the thermoelectric performance. In this study, a variety of materials is presented, starting by the standard used conventional organic and inorganic thermoelectric (TE) materials. Organic materials, such as polyaniline and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT) composites, acquired ZT values ranging from 0.5 to 1.0, demonstrating their promise for versatile and low-cost applications. At extreme temperatures (∼500 K), inorganic materials such as bismuth telluride (Bi2Te3) and lead telluride (PbTe) achieved ZT values around 2.0, indicating great efficiency in power production. Bi2Te3/PEDOT, a hybrid material with organic and inorganic components, demonstrated improved performance with ZT values of 1.5–2.0 due to the synergistic effects of its constituents. Novel composite materials, such as Bi2Te3-carbon nanotube (CNT) composites and using graphene, developed to optimize thermal and electrical characteristics, enhanced device performance by up to 25% over standard materials, with ZT values ranging from 1.8 to 2.2. In addition, in the present study the new recent materials after applying enhancement methods will be presented. These new materials are developed by different methods and synthesis such as doping, superlattice and heterostructure materials and other methods will be discussed. The main findings indicate that the strategic use of these advanced materials may significantly increase the efficiency and output power of TEG devices, making them more practical for a wide variety of applications. As an examples, 2.8 for (GeTe)0.95(Sb2Te3)0.05 alloy, 2.4 for Chalcogenide, ZrS2, Bismuth telluride thin film (p-type Bi2Te3/Sb2Te3 superlattices) and 2.75 for Bismuth telluride thin film (Bi2Se1.2Te1.8). Finally, the present paper investigates on the newest technology and strategies that are applied in this research area in order to enhance the TEG performance enhancement.

Population growth, coupled with industrial and agricultural development, has resulted in increased demand for freshwater supply. For countries with scarce water resources, desalination constitutes the only viable solution to this problem. Reverse osmosis (RO) technology has become widely used as the membrane materials have been upgraded and the costs have been reduced. Nowadays, RO is the foremost technology for desalting different types of water such as seawater, brackish, and tap water. However, its design is critical since many parameters are involved in obtaining a good design. The high use of RO encourages the establishment of a procedure that facilitates the design process and helps in obtaining an optimum-performance RO desalination system. This paper presents a procedure divided into three parts: (1) classifying RO parameters; (2) choosing the parameters in a certain order and doing the calculation process through 12 steps; and (3) then inserting the selected parameters and the obtained values on RO System Analysis (ROSA) software. These points are then summarized by creating an algorithmic chart to follow during the design phase of the RO system using ROSA. An example on the proposed list is then taken to validate the procedure, and a comparison is conducted on choosing different values for the parameters. The results of this comparative study show that choosing different parameters affects the RO system productivity. Additionally, every design has a specific optimum set of parameters, which depends upon the design constraints set by the user.

The rising demand for sustainable energy solutions has made the utilization of waste heat from industrial processes a priority. Thermoelectric generators present an effective method for recovering and converting waste heat into useable electrical energy, therefore enhancing energy efficiency and sustainability. This study presents a parametric study of thermoelectric generators for waste heat recovery from heating chimney exhaust. In order to investigate the impact of placing the thermoelectric generators at different locations, simplified thermal resistance modeling was performed. Performance metrics demonstrate that the positioning of the thermoelectric generator site can bring about major improvements including thermal resistance, generated power, temperature of water heated, and energy conversion efficiency, which ranged from 0.57 % to 5.6 %, depending on thermoelectric generators configuration and operating parameters. By positioning thermoelectric generators on the exterior walls of the exhaust pipe, close to the heat source, a significant amount of electrical power—up to 37.67 W—could be produced. Additionally, a parametric analysis was conducted on important operating parameters: the mass flow rate and input temperatures of the exhaust gas and water. The application of 6 different cases showed that Case 5 of thermoelectric generator modules, with ṁg = 0.25 kg/s, Tg,i = 390 °C, ṁw = 0.3 kg/s and Tw,i = 20 °C, was the optimal condition, based on observations. The results demonstrate notable advancements in power production and energy recovery, and includes clear recommendations for future research that will bring about a shift in the direction of sustainable industrial operations.

Recovering the waste heat from condensers of Heating, Ventilating and Air Conditioning (HVAC) is taking big importance nowadays in the building energy management sector. Advances in this area are still needed due to the high amount of heat released from the condensers versus the low effectiveness of and high volume of the heat recovery medium. As compact and high effectiveness heat exchangers, tubes and fins heat exchangers constitute a potential candidate to overcome the concerns. In this context, the primary goal of this research is to investigate the effect of employing tubes and fins heat exchangers to recover heat from the condenser. To accomplish this goal, a thermodynamic modeling, in addition to analytical approach of the system performance were introduced. Then, a parametric study was performed to examine the effect of the mass flow rate of air and water on the suggested heat recovery system. Finally, economic, and environmental insights based on the energy analysis are presented. It was observed that increasing the mass flow rate from 0.417 kg/s to 2.5 kg/s enhanced the power output from 14.5 kW to 15.1 kW. Similarly, lowering the water inlet temperature from 35 °C to 15 °C increased the power output from 11.28 kW to 15 kW The study highlighted the notable savings with various COP and cooling load, particularly at low COP and a cooling load of 30 kW. Moreover, the investigation revealed that maintaining a constant COP of 2 and increasing cooling loads contributed to higher CO2 emission reduction, ranging from 3.8 kg at 5 kW to 16.5 kg at 25 kW. The findings confirm that the suggested heat recovery system is effective in reducing energy waste and minimizing environmental impact. Finally, it was observed that the proposed system has 95 % capacity of heat recovery.

In this manuscript, we present a unique cogeneration system that combines diesel power generators with thermoelectric generators (TEGs), using the comparatively cool water in an integrated tank and hot exhaust gases to produce additional heat and power. By connecting a series of TEGs and a cold water tank to the diesel generator, the design enables the water to gradually warm up and become appropriate for usage in both domestic and commercial settings. We did a parametric study and created detailed thermal models to verify the viability of our idea. The findings indicate that the temperature differential across each TEG module and the total power output increase roughly linearly, based on the ratio of the diesel generator's power to the thickness of TEG to thermal conductivity. Additionally, the total power output increases linearly with the length of the TEG plate and declines exponentially with the height of the exhaust gas duct. The system may produce up to 3,223 W more electricity under certain circumstances, such as an exhaust gas duct height of 0.05 m, a TEG plate length of 1 m, and a generator output of 150 kW. This improvement could result in a 2.58 % reduction in fuel consumption and an equivalent increase in total power production when compared to conventional systems. The heater system recovers up to 22.4 kW/m² and can heat 100 liters of water in 0.2 h. According to these results, diesel generators and eventually diesel power plants might use less fuel and have more energy efficiency thanks to the suggested cogeneration technology.

This research addresses the problem of predicting the thermo-hydraulic performance of concentric tube heat exchangers (CTHE) under turbulent flow conditions, a critical aspect in energy-efficient industrial systems such as HVAC, power generation, and chemical processing. Existing studies often lack accurate predictive methods for balancing heat transfer performance with pumping power requirements. To tackle this issue, novel correlations and an iterative Newton–Raphson method were developed for predicting pumping power and heat transfer rates. Three-dimensional CFD simulations of a water-to-water counter-flow CTHE were conducted, with Reynolds numbers ranging from 4000 to 8000 for both the hot and cold fluids. The simulations employed the Reynolds-Averaged Navier–Stokes (RANS) equations with the k−ω SST turbulence model. The results demonstrated that increasing the Reynolds number enhances both heat transfer rates and pumping power, with the cold fluid requiring consistently higher pumping power. New correlations were developed to predict pumping power, capturing the impact of both entry and fully developed flow regions. These correlations showed an average error of less than 2.33% when compared with the CFD data. The iterative Newton–Raphson method for predicting heat transfer rates demonstrated high accuracy, with an average error of 0.66% for heat transfer rate, 0.03% for hot fluid outlet temperature, and 0.01% for cold fluid outlet temperature. Additionally, we identified optimal operating conditions for efficient cooling and heating based on the heat capacity ratio (Cr). The novelty of this work lies in the development of new, highly accurate predictive correlations and iterative methods for optimizing CTHE performance, going beyond existing literature by providing comprehensive insights into the relationship between pumping power, heat transfer efficiency, and flow conditions.

This research presents a novel approach to power generation utilizing thermoelectric generators (TEGs) by combining the hot exhaust gases from diesel generators with the relatively cool exhaust air from HVAC systems. A number of TEGs are strategically integrated with the HVAC exhaust in the suggested architecture. A comprehensive parametric research and a detailed thermal model were created in order to evaluate the feasibility of this idea. According to the findings, there is a nearly linear increase in the temperature differential across each TEG module as the space cooling load, diesel generator power, and thickness to thermal conductivity (t/k) increase. This, in turn, increases the power output of the TEG assembly. Additionally, the TEGs' power generation displays an exponential fall with increasing exhaust gas duct height and a near-linear connection with the length of the TEG plates. With a diesel generator output of 125 kW and a space cooling load of 200 kW, this configuration can produce up to 3231 W under certain situations, using a duct height of 0.05 m and a TEG plate length of 1 m. This hybrid generator setup might increase power generation by about 2.59 % and decrease fuel consumption by the same proportion when compared to conventional systems.

Fossil fuel consumption is the primary and most influential contributor to global warming. Since fossil fuels are non-renewable energy sources that will eventually be depleted, decision-makers are encouraging individuals and businesses to invest in renewable energy systems. Among these, photovoltaic (PV) panels offer a promising solution for combating global warming by generating electricity from solar energy. However, their efficiency diminishes as temperatures rise. Water cooling systems have emerged as highly effective in reducing PV panel temperatures and thereby enhancing efficiency. The current study focuses on theoretical parametric analysis of water-cooled PV panels, specifically examining the intervals of maximum and minimum relative efficiency enhancements suitable for residential applications. It provides energetic, economic, and environmental insights based on mathematical equations, providing theoretical parametric analysis based on relative efficiency enhancement values of water-cooling methods retrieved from the literature due to the lack of parametric studies present on cooling PV panels. Moreover, the scaled parametric analysis conducted is in terms of the PV area, prompting the user to enter the desired PV area to get insights on the possible system to be constructed. Interval and parametric studies were conducted at the level of water cooling, providing a tool for readers to estimate potential improvements in energy production, savings, and CO2 reduction based on PV applications with respect to the consumption ratio R, which is the amount of energy being consumed by the house from the PV panels. Results indicate that at minimum efficiency enhancement levels, the photovoltaic-thermal water (PVT-W) system demonstrated the highest values for energy enhancement, savings, and CO2 reduction, averaging 634.57R kWh, $272.86R, and 368.05R kg, respectively. Conversely, at maximum efficiency enhancement levels, the flowing water on the PV surface (PV-WS) system exhibited the highest values with averages of 678.16R kWh, $291.61R, and 393.33R kg, respectively. Furthermore, a linear relationship was observed among energy production, savings, and CO2 reduction concerning relative efficiency enhancement.

The aim of this study is to combine renewable energy sources with heat pumps so that the usage of electricity needed to operate heat pumps is minimized along with associated fuel combustion. The aforementioned objective leads to reduce the energy consumption, the operational cost and the environmental impact of the heat pump. To minimize the usage of electricity, it is proposed that the heat pump (HP) system is combined by two renewable energy systems, a Solar Air Heater (SAH) and a Geothermal Well Water (G). To enrich this study, five prospective combinations of Heat Pump (HP), Solar Air Heater (SAH) placed Upstream (U) and Downstream (D) of the condenser, and Geothermal Water Well (G) were investigated. Hereafter, these five combinations are referred as HP-G, HP-S-U, HP-S-D, HP-G-S-U and HP-G-S-D. The thermal modeling of the aforementioned combinations in addition to baseline HP were developed and examined using an in-house computational code. To ensure that the input data used in the computational code are reliable, experiments were conducted to validate that the geothermal water temperature is higher than the ambient temperature in winter, in addition to confirming the analytical thermal modeling of the solar air heater. Numerical analyses and associated parametric studies revealed that the combination of Solar Air Heater (SAH) and a Geothermal Well Water (G) can efficiently increase the performance of the system by reducing the power needed to operate the compressor of HP. The gain in COP was found to be 48, 43, 81, 105 and 191 % for HP-G, HP-S-U, HP-S-D, HP-G-S-U and HP-G-S-D respectively. In addition, results revealed that the most efficient system is the (HP-G-S-D) for all simulated conditions and assumptions with a gain in COP that can reach up to 191 % in comparison to the baseline heat pump system.

This paper presents a simplified theoretical model for analyzing the temperature dynamics of photovoltaic (PV) modules. The model is built on an energy balance approach, considering solar irradiation as the primary energy input. It accounts for the conversion of solar power into electricity and the storage of thermal energy within the PV module, which subsequently increases the PV temperature leading to decay in its electrical efficiency. Heat loss from the top and bottom surfaces of the module, with variations for cooling techniques, is also included. The model is validated against three different experimental studies, demonstrating good agreement with the experimental temperature variations, with a maximum discrepancy ranging from 4 % to 16 %. This simplified model is then applied to two case studies: one representing typical daytime conditions and another simulating cold weather events. By comparing the PV temperature dynamics between the model and the experimental data, it is shown that the model accurately captures the dynamic response of the PV temperatures to changes in solar irradiation and ambient temperatures. Moreover, a parametric analysis is conducted to investigate the effects of key parameters on PV temperature and efficiency. Higher cooling rates from the bottom surface significantly boost electric power output, aligning closely with solar irradiance variations. Enhanced upper surface cooling, through increased convection, reduces PV temperature and thereby improves electric efficiency and power production. The PV temperature increases quasi-linearly with ambient temperature, especially at lower wind speeds, and decreases with higher wind speeds, eventually stabilizing at high values. Additionally, both ambient temperature and solar irradiance contribute to rising PV temperatures, with ambient temperature having a slightly greater effect. These findings underscore the critical role of cooling techniques in optimizing PV performance amidst varying environmental conditions.

This study delves into exploring and comparing various cooling technologies for PV panels, with a special focus on revealing the harmful effect of excessive heat absorption on solar energy efficiency. Effective temperature management and dissipation of excess heat are essential to protect the integrity of PV panels and improve power generation. With a strong emphasis on the importance of experimental setups, this comprehensive research examines the methodologies and cooling methods used across a wide range of experimental studies, illustrating the complexities of data collection and analysis. Supported by schematic illustrations depicting various experimental setups, this study demystifies the complexities inherent in distinct PV cooling methods. Furthermore, the research extends beyond experimentation to include a comprehensive examination of the energy and economic aspects associated with various cooling technologies, including the calculation and presentation of energy efficiency ratios. It is worth noting that the results confirm the superiority of passive cooling techniques, including heat sinks (43 %), PCM (25), evaporation techniques (36 %), and spray cooling systems (54 %), in contrast to active cooling methods, as indicated by their net energy efficiency ratios. Passive cooling is advantageous for its low maintenance and cost-effectiveness, whereas active cooling, though effective in hot climates and enhancing PV efficiency, incurs higher initial costs and maintenance requirements. The novelty of this research lies in its detailed classification of cooling techniques and the specific materials used for each method, coupled with a thorough examination of the measuring tools employed. Furthermore, this study includes a comprehensive comparative analysis based on energy and economic aspects, alongside the advantages and disadvantages of each cooling technique. These invaluable insights hold the potential to revolutionize the development of efficient and dependable cooling strategies for PV systems, thereby elevating the feasibility and sustainability of solar energy as a pivotal cornerstone in our future energy landscape.

Vortex generators are very effective tools in increasing heat transfer from one region to another, especially by convection, and appear to be a very promising concept to be coupled with heat recovery systems. On the other hand, Thermoelectric Generators (TEGs) are devices able to convert differences in temperature into electrical power using the Seebeck effect, the main advantage being working on high or even low differences in temperature. These TEG modules could be very effective tools in the hybridization of heat recovery systems. In this context, the present paper suggests an innovative system that couples three important energy axes together such as Heat recovery, TEGs, and Vortex generators. The current study employs a TEG in a rectangular channel to analyze the influence of the TEG on the flow and the effect of the effect of flow regime on producing electric power in order to assess the viability of this recently proposed concept. The investigation is conducted by varying the Reynolds number in a range of five values: 1000, 2000, 4000, 7000, and 10,000, applying six different configurations. Consequently, the results show that several factors affect the electrical power generated by TEG such as the emplacement, angle of attack, and absence/presence of vortex generators. On the other side, the heat recovered by the flow is affected by the TEG and Re, where the highest heat recovery is achieved at Re = 10,000 for configuration 4 with electrical power of 7.4 W, and for configuration 5 heat recovered by the flow of 1913 W. Besides, it was concluded that TEGs decreased the losses in both hot and cold sides by 1.42 times.

This paper introduces a novel empirical correlation designed to predict the overall heat transfer coefficient (U) in concentric tube heat exchangers. The study utilizes a comprehensive dataset of 2700 data points from CFD simulations, examining the impact of critical variables including hot and cold fluid Reynolds numbers (Reh, Rec), Prandtl numbers (Prh, Prc), and heat exchanger dimensions (tube hydraulic diameter Dh, annular space hydraulic diameter Dc, and overall length L). The analysis incorporates a range of fluid combinations in the tube and annular sections – air–air, air–water, water-air, and water–water – across Reynolds number ranges from 1000 to 20000, covering both laminar and turbulent flow regimes. The correlation was developed using the Adam optimizer to minimize the Weighted Mean Squared Error (WMSE), achieving an impressive convergence to an average prediction error of 6.7% compared to actual U values. The model categorizes flow into four distinct categories, each corresponding to a combination of flow patterns in the tube and annular spaces regimes – Laminar–Laminar, Laminar–Turbulent, Turbulent–Laminar, and Turbulent–Turbulent – integrating both hydrodynamic and thermal entry effects to enhance prediction accuracy. Rigorous error analysis revealed a median error of 5.18%, substantially outperforming existing models. Notably, 10% of the predictions deviate by less than 1%, with 90th percentile errors staying below 15%. Parameters were finely tuned through extensive numerical simulations, ensuring accurate application of the correlation across diverse operational conditions. The study concludes by highlighting the model’s potential to significantly enhance the design and efficiency of heat exchangers and proposes future enhancements to further improve its predictive accuracy.

The gut microbiome plays a significant role in the pathogenesis of pancreatic ductal adenocarcinoma (PDAC), influencing oncogenesis, immune responses, and treatment outcomes. Studies have identified microbial species like Porphyromonas gingivalis and Fusobacterium nucleatum, that promote PDAC progression through various mechanisms. Additionally, the gut microbiome affects immune cell activation and response to immunotherapy, including immune checkpoint inhibitors and CAR-T therapy. Specific microbes and their metabolites play a significant role in the effectiveness of immune checkpoint inhibitors (ICIs). Alterations in the gut microbiome can either enhance or diminish responses to PD-1/PD-L1 and CTLA-4 blockade therapy. Additionally, bacterial metabolites like trimethylamine N-oxide (TMAO) and lipopolysaccharide (LPS) impact antitumor immunity, offering potential targets to augment immunotherapy responses. Modulating the microbiome through fecal microbiota transplantation, probiotics, prebiotics, dietary changes, and antibiotics shows promise in PDAC treatment, although outcomes are highly variable. Dietary modifications, particularly high-fiber diets and specific fat consumption, influence microbiome composition and impact cancer risk. Combining microbiome-based therapies with existing treatments holds potential for improving PDAC therapy outcomes, but further research is needed to optimize their effectiveness.

In this work, the exact solutions of the (2+1)-dimensional generalized Hirota–Satsuma–Ito equation are reported by adopting the He’s variational direct technique (HVDT). The analytic findings of solutions were obtained by semi-inverse scheme, and six form of supposed studies reveal that the solutions belong to soliton groups. The modulation instability is considered. The tan(Π(ξ))\tan \left(\Pi \left(\xi )) scheme on the suggested model is employed to study new rational solutions. The investigated properties of solutions were determined by graphic studies, which shows significantly values of the parameters and susceptibility of abundant solutions. The obtained results in this work are expected to open new perspectives for the traveling wave theory. For the aforementioned wave solutions, we graphically describe their dynamical properties. It is worth mentioning that our results not only enable us to understand the dynamic properties of such equations more intuitively but also provide some ideas for researchers to facilitate more in depth exploration. It is important to mention that our proposed method is highly effective, consistent, and impacting and can be utilized to solve different physical models.

Our aim of this work is to present a review of solar photovoltaic (PV) systems and technologies. The principle of functioning of a PV system and its major components are first discussed. The types of PV systems are described regarding the connections and characteristics of each type. PV technology generations are demonstrated, including the types, properties, advantages and barriers of each generation. It was revealed that the first generation is the oldest among the three PV generations and the most commonly utilized due to its high efficiency in spite the high cost and complex fabrication process of silicon; the second generation is characterized by its low efficiency and cost and flexibility compared to other generations; and the third generation is not commercially proven yet in spite the fact that it has the highest efficiency and relatively low cost, its raw materials are easy to find and its fabrication process is easier than the other generations. It was shown that the target of all the conducted studies is to study the PV technology to enhance its performance and optimize the benefit from solar energy by reducing conventional energy dependence, mitigating CO2 emissions and promote the economic performance.

One of the most effective ways to deal with the effects of the current global energy crisis is to reduce energy consumption and rely energy management strategies. As a result, waste heat/energy recovery might be a helpful option for decreasing energy costs and environmental effect. It entails finding a practical way to apply any engineering system’s wasted heat where the percentage of wasted heat is too high in global. In this context, waste hot water is a rich source of wasted energy that, if recovered, can significantly cut down on the amount of electricity used worldwide. Within this framework, the present research paper provides a thorough analysis of Waste Water Heat Recovery Systems (WWHRS) in terms of performance, design, tools and applications. In addition, it is highlighting the key elements associated with WWHRS, including the wastewater sources and approaches used in the literature for waste water heat recovery. Moreover, the present paper demonstrates the effect of the heat recovery from the drain waste water on economically and discuss the technical barriers to using WWHRS. It will be demonstrated that the feasibility of recovering heat from waste water could decrease significantly the cost of energy consumption for residential or industrial application. In addition, the main tools that are used for heat recovery systems is the heat exchanger where various types are used and the thermal performance are strongly affected by the choice of heat exchangers. Moreover, based on the literature review, it is shown that the methods of studying the thermal performance of the heat recovery system are experimental and/or numerical and in some cases the study is performed analytically. Finally, all discussed and presented studies demonstrate that the WWHRS has a significant benefits and could be considered for new residential construction.

A new concept of power generation from thermoelectric generators TEGs using the hot exhaust gas of boilers and a cold oil tank is proposed. The suggested concept consists of a flow of exhaust gas of boilers and cold oil in a tank separated by a plate comprising several TEGs in series. The oil tank at the bottom of the system constitutes the cold convection condition for the TEG plate and the upper hot exhaust gas flow constitutes the hot convection condition. Accordingly, a temperature gradient is created across the thickness of the TEGs, which play the role of a separation plate, and converted to an electrical power. To justify the feasibility of this new concept, a suitable thermal modeling is developed and the associated parametric analysis is carried out. The parametric analysis reveals that powers up to 622 W can be generated with a system having a space heating load of 200 kW, an exhaust gas duct height of 0.05 m, and a TEG plate length of 1 m. The temperature difference across each TEG module decreases exponentially when the TEGs plate length increases and decreases exponentially when the exhaust gas duct height increases.

This work concerns a comparative experimental study of cooling PV panels by free and forced convection and using finned plates. To this end, four prototypes are considered: the first one with a PV panel alone without cooling techniques, the second one consists of a PV panel with a rectangular finned plate attached to its rear surface and cooled by free convection, a third prototype consists of a PV panel cooled by forced convection by three axial-flow fans and a fourth prototype consists of a PV panel with a rectangular finned plate attached to its rear surface and cooled by forced convection by three axial-flow fans. Results showed an increase of 3.01% in the efficiency of the PV panel with finned plate under forced convection, an increase of 2.55% in the efficiency of the PV panel with finned plate under free convection and an increase of 2.10% in the efficiency of the PV panel under forced convection. Economic and environmental studies are also conducted and estimations of savings per year and amount of carbon dioxide emission reductions are provided.

Abstract Background Stuttering is a fluency disorder characterized by changes in speech flow caused by neuroaudiological factors linked to central auditory processing. We aimed to assess the affection of cortical auditory evoked potentials (CAEP) in stutterers with secondary intention to compare the results with non-stutterers. Methods This was a case–control study, involved 80 participants distributed into 2 groups: 40 adults stutterers formed the study group and 40 adult non stutterers as the control group, aged between 18 and 45 years. N1-P2 recordings were done using tone bursts stimuli. The absolute amplitudes of the N1 and P2 cortical auditory evoked potential wave forms, as well as the peak-to-peak amplitudes and latencies of the N1 and P2 waves, were measured. Results Latencies N1 and P2 CAEP waves were statistically significant prolonged in stutterers than the control group. Regarding N1-P2 amplitudes, there was no significant difference between the two groups. There was a statistically significant negative correlation between N1-P2 amplitude and degree of stuttering. Conclusion Cortical auditory evoked potentials could be an important tool in diagnoses and in assessment of improvement in adult stutterer individuals throughout treatment phases.