Improvement In Electrical Efficiency Research Articles

A comprehensive investigation of porous media’s effects on the performance of photovoltaic thermal systems

Porous media in thermal collectors have been found to enhance the performance of photovoltaic thermal systems. However, there is a lack of comprehensive research on the benefits of using porous media in this context. This paper represents the first comprehensive study comparing various types of porous materials and their effects on system performance. The study employs a three-dimensional simulation to analyze the influence of factors such as material type, porosity, permeability, and thermal conductivity on module efficiency in top, middle, and fully filled configurations. In particular, it has been observed that each material has an optimum porosity, and there is little difference among metal foams, ceramic foams, and ordinary materials, such as aluminum and copper screens. Among the different configurations, the middle configuration had the lowest thermal efficiency improvement (∼17 %), the top configuration increased efficiency by ∼7 %, and the full porous configuration had the highest thermal efficiency improvement, 32 %. Materials with very low conductivity, such as wood, perform better in the middle than in the top configuration. Graphite, despite its high thermal conductivity, has low permeability, which leads to lower thermal efficiency compared to that of most other materials in the top configuration. In the full configuration and particularly in the middle configuration, graphite shows the smallest thermal efficiency improvement due to its significant longitudinal conduction heat transfer. Therefore, in these configurations, graphite is not recommended for use as a porous medium. Regarding added mass, metal foam materials add the most mass to the system, followed by ceramic foam materials, which present considerably lower figures. In all cases, the pump power consumption growth is negligible compared to the photovoltaic power output. In all materials and configurations, there was a small improvement in electrical efficiency, reaching 1.25 % in the full porous configuration. From a holistic perspective, this study showed that porous media can improve the overall equivalent power by up to 9.8 %, compared to a smooth channel.

Enhancement and Broadening of the Internal Electric Field of Hole-Transport-Layer-Free Perovskite Solar Cells by Quantum Dot Interface Modification.

Hole-transport-layer-free perovskite solar cells have attracted strong interest due to their simple structure and low cost, but charge recombination is serious. Built-in electric field engineering is an intrinsic driver to facilitate charge separation transport and improve the efficiency of photovoltaic devices. However, the enhancement of the built-in electric field strength is often accompanied by the narrowing of the space charge region, which becomes a key constraint to the performance improvement of the device. Here, we propose an effective regulation method, the component engineering of quantum dots, to enhance the strength of the built-in electric field and broaden the range of space charge. By using all inorganic CsPbBrxI3-x (x = 0, 1, 2, 3) quantum dot interface modification to passivate the defects of MAPbI3 perovskite films, the regulation law of quantum dot components on the work function of perovskite films was revealed, and the mechanism of their influence on the internal electric field intensity and space charge region distribution was further clarified, thereby fundamentally solving the serious problem of charge recombination. As directly observed by electron-beam-induced current (EBIC), the introduction of CsPbBr2I quantum dots can effectively enhance the interfacial electric field intensity, widening the space charge region from 160 to 430 nm. Moreover, the efficiency of the hole-free transport layer perovskite solar cells modified by CsPbBr2I quantum dots was also significantly enhanced by 1.5 times. This is an important guideline for electric field modulation and efficiency improvement within photovoltaic devices with other simplified structures.

Techno-economic and environmental analysis of a hybrid PV/T solar system based on vegetable and synthetic oils coupled with TiO2 in Cameroon

To assess the production potential, economic profitability and ecobalance of the photovoltaic/thermal (PV/T) system in Cameroon, different configurations of HTF based on water, vegetable and synthetic oils, coupled with different forms of titanium dioxide (TiO2) are used. A numerical code is written in Matlab. The PV/T model connected in direct contact PV-absorber is validated and a multi-objective optimization of the system is performed. The hourly evolution of PV cell temperature for the six HTF configurations revealed a value below 36 °C with Coton/TiO2. The platelets-and spherical-shaped nanoparticles increase the convection transfer coefficient between the fluids and the tubes. TiO2 showed a higher thermal influence in vegetable and synthetic oils than in water at a volume concentration of 4 %. The cotton/TiO2 configuration showed a 12.08 % improvement in electrical efficiency over conventional PV systems with low exergy efficiency compared to water. Configurations with therminolVP-1/TiO2 are better, with the proposed energy cost reduced to 33 % of the price of electricity in Cameroon. The PV/T-Palm/TiO2 system showed an energy cost of $0.03 with a net present value of $568.45, an emission rate of 7.78 kg, a reversibility index of 1.95, an annual cost of $7.07 and a payback time of 5.97yr. This shows that PV/T systems based on vegetable oils are economical.

A numerical study on the performance of a hybrid ventilation and power generation system

Ventilation, cooling and power are essential requirements of buildings. Integration of solar chimney, earth-air heat exchanger and photovoltaic panel forms a new hybridsystem, which is able to provide simultaneous ventilation, cooling capacity and electricity in an effective manner for buildings. The contribution of this study is to quantitatively identify the thermal and electrical performances of the hybrid system using a comprehensive validated numerical model. In addition, a parametric study was also performed to examine the effect of the number of EAHE pipe and solar collector on the performance of the hybrid system in order to further enhance the system performance. The results revealed that the peak daytime ventilation of the proposed hybrid system is reduced by 22.05 % compared to the ventilation system of solar chimney integrated with earth-air heat exchanger, and the outlet air temperature is reduced by 0.12 °C in average; the indoor temperatures for the hybrid and ventilation systems are slightly different. Moreover, the minimum electrical efficiency of hybrid system is 1.34 % higher than that for stand-alone photovoltaic system. Increasing the number of earth-air heat exchangers leads to more than 36.43 % increase in peak ventilation volume and 3.7 % improvement in electrical efficiency. In addition, increasing the quantity of solar chimney-photovoltaic modules can effectively increase the induced ventilation volume, and the outlet air temperature, but has slight effect on the temperature and electrical efficiency of photovoltaic panel. Therefore, the hybrid system not only can supply appropriate ventilation but also can generate electric power to buildings. The findings provide a preliminary guidance for optimizing design of the hybrid system.

Electrical Energy Efficiency Improvement in Chiller Operation

The need for electrical energy to meet consumers is increasing which must be addressed immediately. Along with population growth and economic growth, this energy need will continue to increase. With the use of large amounts of electrical energy, it is necessary to increase efficiency in operating equipment. Airports are one of the largest users of electricity, especially when it comes to cooling systems. Therefore, it is necessary to save energy in airport operations. Airports are one of society's activities, so airports need to save energy. By optimizing power management and calculating the chiller coefficient of performance (COP) value, an airport can be built that saves energy on the HVAC system (especially chillers). Through analysis, it was found that COP increased to 0.584, and the value before optimization was 6.181. As COP increases, chiller performance will increase. The optimized electrical energy efficiency of the cooler is 138.82 kWh / day.

Influence of self-cleaning coating on performance of photovoltaic solar system utilizing mixture of phase change material and Graphene nanoparticle

Improvement of electrical efficiency of photovoltaic systems with utilizing self-cleaning approach has been scrutinized in present work. The dust accumulation has a negative efficacy on the performance of the unit and the optical feature of glass has been improved with coating SiO2 nanoparticles. The finned tank of paraffin (RT25) has been utilized for cooling of silicon cell and cooling tube has been utilized in the middle section. The dispersion of Graphene nanoparticles within paraffin and water makes the heat absorption increase. The single phase formulations for both cooling zones have been incorporated and gravity force has been neglected in the model. Numerical approach has been utilized for unsteady simulation and validation section proved the good agreement of current code. The uniformity of cell temperature enhances about 29.53% with mounting fins. Loading nanoparticles causes the liquid fraction to increase about 4.58%. With installing fins, the electrical performance enhances and such increment enhances about 10.22% for coated glass when t = 3600s. Utilizing fins can increase the amount of CO2 reduction about 10.22%. Also, reduction of emission improves about 29% by utilizing glass with coating.

Performance Enhancement of Photovoltaic-Thermal Modules Using a New Environmentally Friendly Paraffin Wax and Red Wine-rGO/H2O Nanofluid

Photovoltaic/thermal systems are one of the most efficient types of solar collectors because they absorb solar radiation and generate electricity and heat simultaneously. For the first time, this paper presents an investigation into the impact of red wine-rGO/H2O nanofluid and paraffin wax on the thermohydraulic properties of a photovoltaic/thermal system. The study focuses on three innovative nonlinear arrangements of the serpentine tubes. The effects of these materials and configurations are analyzed through numerical simulations. To improve the performance, environmentally friendly materials, including red wine-rGO/H2O nanofluid and paraffin wax, have been used. Various performative parameters such as electrical and thermal efficiency of the photovoltaic/thermal system, exergy, and nanofluid concentration were investigated. The results demonstrated a significant enhancement in the system’s performance when using innovative serpentine tubes instead of simple tubes for the fluid flow path. The use of paraffin C18 increases electrical efficiency, while the use of paraffin C22 improves thermal efficiency. Moreover, the incorporation of phase change materials along with the utilization of innovative geometries in the serpentine tube led to a notable improvement in the outlet temperature of the fluid, increasing it by 2.43 K. Simultaneously, it substantially reduced the temperature of the photovoltaic cells, lowering it by 21.55 K. In addition, the new model demonstrated significant improvements in both thermal and electrical efficiency compared to the simple model. Specifically, the maximum thermal efficiency improvement reached 69.2%, while the maximum electrical efficiency improvement reached 11.7%.

Comparative review and evaluation of state-of-the-art photovoltaic cooling technologies

Photovoltaic systems have a reliable method to generate electrical power from direct solar irradiance. Their efficiency is only up to 20% in real operating circumstances and is affected adversely by the inevitable temperature rise in their surface. Passive, active or combined cooling methods are applied to reduce operating temperature to a suitable level, depending on specific application. A Great body of literature has been investigating different PV cooling methods and techniques to reach optimized system efficiency and cooling effect. It is critical for both researchers and practitioners to have a thorough understanding and awareness of the most recent advances and existing gaps. Although there are certain review papers in this field, it is necessary to have up-to-date reviews of the most recent progress and research since the previous ones. In the present work, the main focus was to provide a review of the most recent studies and to compare their outcomes to provide a reference for practitioners and researchers. The holistic classification and evaluation of all the possible cooling technologies were provided in order to draw a comparison between various cooling approaches. Based on the analysis obtained, cooling techniques can ensure improvement in electrical efficiency in a range from 1% to 53% with expected decrease in the photovoltaic panel's surface operating temperature from 1.8 °C to 46 °C. It was also found that spectrum filtering and jet impingement indicated highly remarkable enhancements. The other factors, such as the size of the examined photovoltaic panel, photovoltaic technology, as well as climate circumstances have a strong impact on the cooling performance besides the selection of the specific coolant. The necessity for integral evaluation (performance, economic and environmental) of cooling techniques was also identified as key issue.

Digital development, environmental regulation, and electric power utilization efficiency

To further promote green and sustainable development, the Chinese government has put forward the carbon peaking and carbon neutrality goals in 2020. As a clean energy, electric power can effectively replace the use of traditional fossil energy and ultimately reduce environmental pollution. Under the relevant background, in order to further explore the impact mechanism of digital development on China’s electric power utilization efficiency, a static panel regression model of provincial panel data was established on the basis of measuring the electric power utilization efficiency of 30 provinces in China from 2011 to 2020. The impact of digital development on electric power utilization efficiency of China and the moderating effect of environmental regulation are analyzed. The empirical evidence yields the following conclusions: 1) Digital development has a significant positive impact on the electric power utilization efficiency in China. 2) The results of moderating effect analysis and heterogeneity analysis show that strengthening environmental regulation can promote the improvement of electric power utilization efficiency; Digital development has different impacts on electric power utilization efficiency in the east, central and west of China, especially in the west. 3) In addition, the increase of the Consumer price index of hydropower and fuel and Share of R&D expansion in regional GDP will promote the improvement of electric power utilization efficiency, while the Share of secondary industry in regional GDP will have a negative impact on it.

A comparative study on photovoltaic/thermal systems with various cooling methods

Nowadays Photovoltaic (PV) is the most promising technology for converting solar radiation into electricity. The main drawback of PV technology is lesser efficiency as compared to conventional power-generating technologies. Generally, PV efficiency decreases as temperature increases, with a magnitude of about 0.5%/°C. This drawback can be resolved with a proper cooling technique that has been proposed in recent years. Numerous cooling techniques have been developed, and most of them are based on active water and air cooling because they are the simplest. This article aims to discuss the recent developments in PV panel cooling techniques and thermal management. The improvement in electrical efficiency depends upon the proper cooling techniques, capacity, type of PV module, and yearly climate condition of the locations which often results in a 3–5% improvement. The cooling techniques should be designed for PV systems in such a way that is simple to install, reliable, natural in their effectiveness, and maintain a low solar cell temperature.

Insight into the investigation of Fe3O4/SiO2 nanoparticles suspended aqueous nanofluids in hybrid photovoltaic/thermal system

This experimental study aims to evaluate the energetic performance of a photovoltaic-thermal system with a serpentine tube collector. A photovoltaic-thermal unit with a serpentine tube collector is used to compare the unit's performance metrics to those of a PV panel without cooling. The considered heat transfer fluid is the hybrid nanofluid prepared using water and Fe3O4/SiO2 nanoparticles. Using irradiance data from an average day in Aligarh, India, the experiment is conducted in indoor environment in a solar simulator under regulated operating circumstances. Effects of mono and hybrid nanofluids are examined at 3% wt. concentration for varying flow rates (20, 30, 40 LPM). The experimentation analysis showed that the maximum drop in PV temperature at 20 LPM is 25 °C, 24 °C, and then 16 °C for Fe3O4/water, SiO2/water, and Fe3O4/SiO2 nanofluids-based PVT systems, respectively with a highest possible increase in electrical efficiency of 12.6 percent, 18.46 percent, and 24.34 percent, respectively, when compared to traditional PV systems. At a flow rate of 40 LPM, the best performance is obtained using a hybrid PVT method coupled with an aqueous Fe3O4/SiO2 nanofluid. Additionally, it is discovered that hybrid nano-fluid-based PVT systems exhibit 10.5% and 5% greater thermal efficiency than Fe3O4-Water and SiO2-Water PVT systems, respectively. The overall highest efficiency of 67% is achieved for hybrid nanofluid at a flow rate of 40LPM. The hybrid Fe3O4/SiO2 nanofluid is capable of serving as an acceptable cooling fluid for the PV/T collector, as evidenced by the PV/T system's notable improvement in thermal and electrical efficiency and prominent cooling impact. Keywords : Solar energy, Hybrid nano-fluid, Heat transfer, Electrical Power, Thermal Efficiency, PVT system. • The role of hybrid nanofluids for the performance of PVT systems was studied. • Hybrid nature of nanofluid make it more stable than mono-nanofluid. • Electrical and thermal efficiency were analysed at fixed concentration and varying flowrate. • Comparison of Fe 3 O 4 /SiO 2 nanofluid is carried out with individual mono-nanofluid.

How does residential electricity consumption respond to electricity efficiency improvement? Evidence from 287 prefecture-level cities in China

Energy conservation from efficiency-oriented policies could be undermined due to the substitution effect and the income effect originating from the fact that energy efficiency improvement decreases the real price of electricity consumption. The ratio of the electricity consumption caused by the substitution effect and the income effect to the potential energy savings is termed the rebound effect. The magnitude of the rebound effect depicts how residential electricity consumption responds to electricity efficiency improvement. This paper adopts a stochastic electricity demand frontier approach based on the panel data covering 278 cities in China to uncover the relationship between electricity efficiency and residential electricity consumption. The main results show that 48.88% of the energy saving from efficiency improvement is offset due to households’ behavior adjustments. We also find that residential income, population density, and temperature deviation are vital determinants of residential electricity consumption, whereas household size significantly shapes the magnitude of the rebound effect. The empirical findings imply that different regions in China should design supporting policies for energy efficiency improvement according to local conditions considering that households are incentivized to consume more electricity with efficiency improvement.

Numerical Investigation on Using MWCNT/Water Nanofluids in Photovoltaic Thermal System (PVT)

Photovoltaic thermal systems (PVT) are solar energy conversion systems that produce both electricity and heat simultaneously. PVT systems seeking to minimize temperature of solar cells become more significant with the increased thermal and electrical efficiency of the working fluids (water and nanofluids) employed in the solar thermal system. The major objective of this research is to investigate the thermal, electrical and overall performance of the photovoltaic thermal (PVT) system with different weight fractions of MWCNT/water nanofluids (φ = 0.3%, 0.6% and 1%) and water. A sheet and tube PVT system model geometry, which has been simplified to rectangular PV cell, absorber plate, cylindrical pipe, and fluid domain geometries to investigate outlet and PV cell temperature of photovoltaic thermal (PVT) system between different weight fractions of MWCNT/water nanofluids (φ = 0.3%, 0.6% and 1%) and water with varying fluid inlet velocities from 0.02 m/s to 0.08 m/s using ANSYS FLUENT. The results show that increasing the inlet fluid velocity and weight fraction of the working fluid improves thermal and electrical efficiency. The highest improvement in thermal and electrical efficiency at 0.08m/s inlet fluid velocity for the weight fractions, φ = 1% of MWCNT/water nanofluids is 7.8% and 0.03% compared to water. In addition, the weight fractions, φ = 0.3% of MWCNT/water nanofluids is 4.46% and 0.01% and the weight fractions, φ = 0.6% of MWCNT/water nanofluid is 6.72% and 0.02%. Additionally, the maximum increase of overall efficiency at 0.08m/s inlet fluid velocity for the weight fractions, φ = 1% of MWCNT/water nanofluids is 7.83% compared to water while the weight fractions, φ = 0.3% of MWCNT/water nanofluids is 4.43% and the weight fractions, φ = 0.6% of MWCNT/water nanofluid is 6.74% at inlet fluid velocity of 0.08 m/s. As a result of the research, it was discovered that using MWCNT/water nanofluids improves the performance of PVT systems.

Effect of reflective coating on thermal and electrical performances of solar roof tiles

Compared to solar panels, the current adoption rate of building integrated photovoltaic (BIPV) systems in Australia is relatively low owing to their complex design, fluctuation in efficiency during operation and high cost. The efficiency of the BIPV system drops significantly with the increase of module temperature beyond 25°C. To stabilise the system temperature during operation and reduce the complexity of integration of a cooling system, reflective coating (RC) has been introduced in the present work. The effect of reflective coating on the electrical and thermal performances of a BIPV system, specifically solar roof tiles (SRTs), has been investigated. Several types of RCs and their application methods have been tested to optimise their performance. In the laboratory test, it was found that the RC could reduce the surface temperature by 11 °C, leading to an electrical efficiency improvement of 6.61%; while in the natural environment test, the observed temperature reduction was 10 °C, providing an electrical efficiency improvement of 6%. The internal temperature of an enclosed polystyrene test chamber placed under the SRTs during testing was also monitored. It was found that a reduction in the internal test chamber temperature of 18.7% could be achieved with RC, indicating a positive influence in lowering the interference between indoor and outdoor environments. However, RC beneath the monocrystalline silicon solar cells did not make an obvious contribution to the temperature reduction.

PV/Thermal as Promising Technologies in Buildings: A Comprehensive Review on Exergy Analysis

Solar Photovoltaic (PV) systems are degraded in terms of efficiency by increment in their temperature. To keep away from efficiency degradation regarding the temperature increase, various thermal management techniques have been introduced to keep the temperature low. Besides improvement in electrical efficiency, the overall efficiency can be enhanced by using the extracted thermal energy from the cell. The extracted heat in these systems, known as PV/Thermal (PV/T), can be applied for some purposes including water or air heating. This article reviews the works on the PV/T systems exergy analysis and discusses their findings. Based on the findings of the reviewed works, different factors such as the system configuration, used components and elements, and working conditions affect the exergy efficiency of these systems. As an example, use of coolants with improved thermal features, i.e., nanofluids, can cause improvement in the exergy efficiency. In addition to the nanofluid, making use of the thermal energy storage unit can further enhance the exergy efficiency. Furthermore, it has been observed that the materials of nanostructures can be another element that influences the enhancement of exergy efficiency. Moreover, the usage of some components such as glazing can lead to avoidance of thermal energy loss that would be beneficial from an exergy point of view. Finally, according to the reviewed works and knowledge of the authors, some suggestions are represented for future works in this field.

Effectiveness of heat sink fin position on photovoltaic thermal collector cooling supported by paraffin and steel foam: An experimental study

Forced convective cooling effectiveness on photovoltaic thermal collector electrical and thermal performance was experimentally studied with phase change material (paraffin) + steel foam mixture and two different angular positioned finned heat sink attachments. Fins are positioned flat and inclined, and air was forced with fan to flow between them. Solar radiation, temperature, electrical and thermal power, energy, and exergy efficiencies were determined and compared with reference photovoltaic module data. The first photovoltaic thermal collector was constructed with phase change material (paraffin) + steel foam mixture application to the back surface and covering with an incline finned heat sink. The second one was assembled with phase change material (paraffin) + steel foam filling to back surface and covering with a flat finned heat sink. Incline and flat finned heat sink attached collectors were cooled 12.23% and 21.67% relatively more than photovoltaic module. Electrical efficiency improvement with incline finned and flat finned heat sink application acquired approximately 5.09% and 6.18% relative to the photovoltaic module, which has 4.38% electrical efficiency, thanks to the cooling provided. The overall efficiencies were 41.4% and 59.53%. Photovoltaic module exergy efficiency is 4.67%, it is increased to 5.59% and 6.87% by cooling with incline finned heat sink and flat finned heat sink applications. Utilizable energy enhancement is identified approximately 140.32 kWh/year and 207.42 kWh/year by assuming 2738 h annual sunshine time in Turkey. These potentials rely on increase in electrical efficiency and heat recovery during cooling of PV/T collectors with incline and flat finned heat sinks. The predicted energy profit can be estimated at $7.01/year and $10.37/year, and its equivalent in emission reduction can be 115.76 kg·CO2/year and 171.12 kg·CO2/year.

Energy, exergy, economic and environmental analysis of photovoltaic/thermal integrated water source heat pump water heater

The photovoltaic thermal integrated water source heat pump (PV/T-WSHP) water heater system can meet the demand for not only the domestic hot water but also the electricity production. To comprehensively analyze the benefits of the PV/T-WSHP water heater system, energy, exergy, economic and environmental analysis method was applied. A TRNSYS model of the PV/T-WSHP water heater system was developed based on the existing experimental setup, and validated by the experimental data. A combined system of single PV system and single air source heat pump water heater (PV + ASHP) system model was also built for comparison. The simulated results indicated the PV/T-WSHP water heater system had a 25.3% improvement in electrical conversion efficiency, a slightly lower EER of 3.71 and a significant reduction in annual exergy loss, comparing with the combined PV + ASHP system. In addition, the annual cost of the PV/T-WSHP water heater system was 217.7 yuan lower than the combined PV + ASHP system. The PV/T-WSHP heat water system and the combined PV + ASHP system could annually save the standard coal of 0.62 tons and 0.50 tons, respectively. This study provides an effective method to comprehensively analyze the performance of the PV/T-WSHP water heater system.

Green Cloud? An Empirical Analysis of Cloud Computing and Energy Efficiency

The rapid, widespread adoption of cloud computing over the last decade has sparked debates on its environmental impacts. Given that cloud computing alters the dynamics of energy consumption between service providers and users, a complete understanding of the environmental impacts of cloud computing requires an investigation of its impact on the user side, which can be weighed against its impact on the vendor side. Drawing on production theory and using a stochastic frontier analysis, this study examines the impact of cloud computing on users’ energy efficiency. To this end, we develop a novel industry-level measure of cloud computing based on cloud-based information technology (IT) services. Using U.S. economy-wide data from 57 industries during 1997–2017, our findings suggest that cloud-based IT services improve users’ energy efficiency. This effect is found to be significant only after 2006, when cloud computing started to be commercialized, and becomes even stronger after 2010. Moreover, we find heterogeneous impacts of cloud computing, depending on the cloud service models, energy types, and internal IT hardware intensity, which jointly assist in teasing out the underlying mechanisms. Although software-as-a-service (SaaS) is significantly associated with both electric and nonelectric energy efficiency improvement across all industries, infrastructure-as-a-service (IaaS) is positively associated only with electric energy efficiency for industries with high IT hardware intensity. To illuminate the mechanisms more clearly, we conduct a firm-level survey analysis, which demonstrates that SaaS confers operational benefits by facilitating energy-efficient production, whereas the primary role of IaaS is to mitigate the energy consumption of internal IT equipment and infrastructure. According to our industry-level analysis, the total user-side energy cost savings from cloud computing in the overall U.S. economy are estimated to be USD 2.8–12.6 billion in 2017 alone, equivalent to a reduction in electricity use by 31.8–143.8 billion kilowatt-hours. This estimate exceeds the total energy expenditure in the cloud service vendor industries and is comparable to the total electricity consumption in U.S. data centers. This paper was accepted by Chris Forman, information systems. Supplemental Material: Data files and the online appendices are available at https://doi.org/10.1287/mnsc.2022.4442 .

Stress annealing effects on magnetic properties of grain oriented electrical steel under compressive stress

There is a strict relation between Gross National Product and electric energy consumption; consequently, the improvement of electrical machines efficiency is highly desired. Regarding power transformers, power loss of magnetic core sheets increases due to compressive stresses appearing during its operation, decreasing power transformer performance. In this article, the effects of tensile stress annealing on power loss of grain oriented electrical steel under compressive stress are evaluated. To do that, the power loss of two uncoated sheets was measured before and after tensile stress annealing for several magnetic inductions (0.7, 1.0, 1.3, 1.5, and 1.7 T) and compressive stress (0, 2, 4, 6, 8, and 10 MPa). This thermomechanical procedure was performed at 500°C, 40 MPa for 10–20 min. Although the tensile stress annealing performance depends on crystallographic texture, a power loss reduction occurs for both samples when compressive stresses were higher than 6 MPa, regardless of magnetic induction. In summary, tensile stress annealing could reduce the deleterious effects of compressive stress on power loss, making commercial grain oriented electrical steel more magnetic uniform and improving power transformer efficiency.

Performance improvement of a naturally ventilated building integrated photovoltaic system using twisted baffle inserts

Building integrated photovoltaic (BIPV) systems constitute a key concept for the realization of sustainable buildings. However, these systems have limited efficiency and durability due to their insufficient cooling capabilities. To overcome this drawback, it is necessary to maintain the operating temperature as low as possible. This study investigates the effectiveness of a passive low-cost strategy to improve the photovoltaic module (PV) performance of naturally ventilated BIPV systems by decreasing the module operating temperature. This strategy consists of inserting twisted baffles on the rear side of a PV module to enhance its cooling performance. A numerical investigation was performed using Computational Fluid Dynamics (CFD) simulations in order to explore the module surface temperature and its electrical efficiency. The effects of solar irradiance, the number and position of twisted baffles, and twist ratio have been investigated. The results revealed that the average temperature of the PV surface decreases with the increase of the number of twisted baffles (N), which leads to an improvement in the electrical efficiency. Indeed, the optimum performance enhancement is attributed to N = 15, and the corresponding PV temperature was decreased from 312.66 K to 310.15 K and from 348.42 K to 342.64 K for a solar irradiance variation from 200 to 1000 W.m-2, resulting in an improvement of 1.21–3.36% in electrical efficiency compared to the case without inserts. Concerning the effect of the twist ratio, it is shown that the optimum electrical efficiency improvement is reached for the lowest twist ratio, which is in the range of 1.7–6.1% for solar irradiance range from 200 to 1000 W.m-2.