Maximum Temperature Reduction Research Articles

Energy, exergy, and economic assessment of thermal regulation of PV panel using hybrid heat pipe-phase change material cooling system

There has been a theoretical investigation for energy, exergy, and economic evaluation of thermal regulation of PV panels via an innovative hybrid cooling system of flat heat pipes (HPs) coupled with phase change material (PCM). PV panel dissipates its heat through the HP evaporator while the HP condenser is cooled by PCM. The cooling system performance is investigated for different PCM quantities and types (RT42, RT35HC, and SP31) for summer and (RT21, RT18HC, and SP15-gel) for winter conditions in Egypt. A thorough study and analysis have been conducted for the impact of the cooling system on PV panel's temperature, electric efficiency, output power, PCM energy storage, and system efficiency. The results show that compared with conventional PV, the best PCM type for PV performance in summer is SP31 of 3 cm thickness, which achieves a maximum PV temperature reduction of 20.6 °C with a maximum improvement in PV electric efficiency of 11.5%. SP15-gel of thickness 2.5 cm is the best PCM for winter conditions, achieving 14.1 °C temperature reduction with 7.2% enhancement in PV electric efficiency. The exergy efficiency of the PV panel is higher than in PCM, where it rises as the phase change temperature of the PCM increases. PV maximum average daily exergy efficiency is 13.4% for SP15-gel, compared with 12.71% for conventional PV in winter, while SP31 achieved 12.25%, 1% higher than reference PV in summer. PCM's maximum average daily exergy efficiency is 0.69% and 0.7% for RT42 and RT21 in summer and winter, respectively. The minimum payback period for conventional PV is about 18.01 years, while it is approximately 13.39 years for PV with HP and PCM. The studied cooling system at different PCMs proves its capability to enhance the PV performance with higher energy and exergy efficiencies and lower cost and store the excess heat inside the PCM.

On the mitigation potential and urban climate impact of increased green infrastructures in a coastal mediterranean city

An increase of the green infrastructure (GI) in cities contributes to sharing the common goals of reducing energy usage, mitigating pollution emissions, and improving the urban climate. The synergy between urban heat island (UHI) and extreme urban heat in Athens (Greece), during the summer, is inevitable, while its green cover is considerably low. However, very few studies have reported the biophysical effects of the GI on the surface standard meteorological field and urban boundary layer (UBL) that are triggered by changes in the GI at a seasonal scale. The present study sheds light on the complex synergies between UHI and extreme urban heat focusing on warm coastal cities like Athens.To this end, we hypothetically designed and simulated three scenarios of increased GI, such as GI30, GI50, and GI70. The mosaic approach is used, and the portion of each urban grid cell is replaced with different types of vegetation patches, by 30%, 50%, and 70% using the weather research and forecasting (WRF) model, coupled with a single-layer urban canopy model (SLUCM) at city-level for assessing mitigation potential and urban climate impact. The results showed that the daily peak decrease of the ambient temperature at 17:00LT is close to 0.0157 °C per unit of increase of the GI, while the maximum expected daytime summer temperature decrease is 0.7 °C, 1 °C, and 1.1 °C for GI30, GI50, and GI70 scenarios respectively compared to the control case. The corresponding decrease of the nighttime ambient temperature is found to be 0.0375 °C per unit of increase of the GI, whereas the maximum temperature reduction for the G70 scenario is close to 1.9 °C. Increased GI is found to significantly lower the height of the planetary boundary layer (PBL), thus increasing the risk of higher pollution concentration, while a significant impact on the strength of the sea breeze and the level of humidity is observed increasing the risk of thermal discomfort. Results are also compared with the findings of thirty similar projects from other cities to provide a global assessment of the mitigation potential of additional GI in cities. Our results contribute significantly to understanding the mitigation potential and urban climate impact of increased GIs at a seasonal scale.

Reducing The Energy Cost of Buildings Using Shading Plates: Experimental and Numerical Study

The amount of carbon emission pumped into the atmosphere has led to a rise in global temperature. Rapid urbanization increased the use of air conditioners, resulting in the urban heat island effect. The use of environmentally friendly methods in reducing energy consumption for buildings is needed now more than ever. This study aims to evaluate the cooling load of a prototype by installing a shading plate above its roof at a height of 0.67m. A wooden panel with an attached aluminium sheet is used as a shading plate, 2m by 0.9m. The prototype with a dimension of 0.80m (L) x 0.50m (W) x 0.97m (H) is a scaled-down model of the guardhouse located near Block E, UCSI University. Along with the shading plate, the prototype is placed nearby the guardhouse to validate the actual guardhouse's exact condition. The shadow acts as an insulator to the prototype. There were two devices used for data collection; a VELOCICALC thermometer to measure the air velocity and air temperature and an infrared thermometer to measure the profile temperature of the room walls, roof, and floor. To ensure the prototype is adequately ventilated, it was placed 20 cm above the floor using red bricks from 9 a.m. to 5 p.m, a maximum temperature reduction of 4.5°C when the shading plate thoroughly shades the room. A total of 14.5% electricity cost can be reduced monthly when the guardhouse is fully shaded from 11 a.m. to 2 p.m. In contrast, both the actual guardhouse and the prototype model can receive full sunlight from 11 a.m. to 5 p.m., while from early morning till 11 a.m., the guardhouse is fully shaded by the UCSI Block E building.

Planning, Designing, and Managing Green Roofs and Green Walls for Public Health – An Ecosystem Services Approach

Installing green roofs and green walls in urban areas is suggested to supply multiple ecosystem services of benefit to human health and well-being. In a three-step literature review, we examined current knowledge on the link between public health and green roofs and green walls. A systematic search identified 69 scientific articles on green roofs/walls with a public health discourse. These articles were categorized according to type of health path covered (reduction of temperature, air pollution, noise or environmental appraisal) and coverage of issues of relevance for strategies on planning, design/construction, and maintenance of green roofs and green walls. Articles identified through the structured search were complemented with reviews (with no explicit public health rationale) covering reduction of noise, temperature, or air pollution and environmental appraisal. Other relevant studies were identified through snowballing. Several of the articles provided guidelines for optimizing the effect of green roofs/walls in supporting ecosystem services and maximizing well-being benefits to support health pathways identified. These included specifications about planning issues, with recommended spatial allocation (locations where people live, sun-exposed for maximum ambient temperature reduction) and with physical access needed for environmental appraisal. Recommendations regarding design parameters covered substrate depth (deeper generally being better), plant choices (more diverse roofs providing more services), and maintenance issues (moist substrate positively correlated with heat reduction).

Performance enhancement of the photovoltaic system with different cooling methods.

Solar energy has been a vital renewable energy source for humanity for decades. Researchers have proposed many strategies to harness the same but solar photovoltaic (PV) is the only technology which has reached commercial scale and highly successful in meeting renewable energy goals of many countries. The major drawback of PV systems is that increase in the temperature of solar cell of the PV module beyond the threshold limit brings down its electrical efficiency (EE). Hence, this review paper discusses the different cooling techniques responsible for reducing the cell temperature, which in turn increases not only its EE, but also collection of the thermal energy that is otherwise considered to dampen the performance of the PV system. A brief study on PV with air cooling, photovoltaic thermal (PVT) with water cooling, PVT/PCM with and without fins, PVT integrated with nanofluids has been done in this review paper. PVT hybrid systems are the need of hour to get the optimum efficiency. Amongst the PVT systems, the performance analysis of PV integrated with the nanofluid is discussed and it is found to give the maximum cell temperature reduction. Since reduction in the cell temperature directly relates to better efficiency, PVT system using nanofluid as a cooling medium gives the best overall efficiency (OE) followed by PVT system incorporating water and air respectively. This review paper also gives spotlight to the real-time usages of PCM and nanofluids for the effective cooling ability especially in the case of PV module.

Performance Improvement of a Novel Trapezoid Air-Cooling Battery Thermal Management System for Electric Vehicles

An air-cooling battery thermal management system is a reliable and cost-effective system to control the operating temperatures of the electric vehicle battery pack within an ideal range. Different from most designs of the rectangular battery pack in previous research, this one proposed a novel isosceles trapezoid layout to improve system heat dissipations. The simulation results showed that the trapezoid design delivered better cooling performances than the rectangular one with a maximum temperature reduction of 0.9 °C and maximum temperature difference reduction of 1.17 °C at the inlet air flow rate of 60 L/s. Moreover, the cooling performance was further boosted by an aluminum heat spreader. The boosted design delivers an average Max T (32.95 °C) and an average ΔT (3.10 °C) at five different flow rates, which are 8.8% and 66.1% lower the one without the spreader (35.85 °C and 5.15 °C). Compared with the rectangular design without the spreader, the average Max T and ΔT of the boosted trapezoid design are reduced by 10.4% and 91.9% in addition to a space-saving of about 5.26%.

Utilization of a phase change material with metal foam for the performance improvement of the photovoltaic cells

This study presents a novel configuration for improving the photovoltaic (PV) panel's thermal management system, which includes a phase change material (PCM) with the metal foam layer. During the energy-absorbing mode, the arrangement allows for quicker heat dissipation from the system, resulting in the cooling of the PV panels. The effects of the foam-layer material, PCM thickness, and foam porosity are numerically simulated and analyzed. The results demonstrated that the higher PCM layer thickness leads to a lower PV surface temperature. The extracted curves indicated that lower porosity causes higher maximum PV temperature. Furthermore, it was found that average electrical efficiency for the model with a porosity of 0.9, 0.8, 0.4, and no-foam state are 13.805%, 13.794%, 13.761%, and 13.714%, respectively. All data are almost similar for both copper and aluminum foams, and there are negligible differences between the results. The results for the four chosen months describe that for June, March, and September, the PCM layer absorbs heat and causes a considerable reduction in the PV maximum temperature, but for December, this process is not valid. Accordingly, superior PCM-based thermal management is achieved through the proposed system.

Novel design optimization for passive cooling PCM assisted battery thermal management system in electric vehicles

Recently, the phase change material (PCM) battery thermal management system (BTMS) attracted attention. However, enhancement and optimization for the BTMS are required due to volumetric system design and low thermal conductivity. This study provides a novel design optimization to improve the environmental aspect of the cooling system and reduce its weight. Jute fibers as a planet-system, available, cheap, and weightless material is combined with the PCM battery thermal management based. The thermal behavior of large lithium-ion batteries (LIB) under different load protocols including fast discharge, periodic load, and real drive cycle are investigated. The results with the periodic load profile confirm that the maximum temperature for the cooling strategies of no-cooling, PCM cooling and PCM with jute reaches 39.22 °C, 38.22 °C and 35.09 °C, respectively. Moreover, applying aggressive high constant discharge current leads to further reduction in maximum temperature, where the maximum temperature reaches 47.27 °C, 41.06 °C, and 36.29 °C with the no-cooling, PCM cooling and PCM with jute cooling strategies, respectively. This article represents the first attempt to use a combination of jute and PCM in order to maximize temperature efficiency enhanced. Thus, this research contributes to further design optimization in battery thermal management system simplicity, environmental friendliness, energy and weight saving.

Enhanced Net Channel Based-Heat Sink Designs for Cooling of High Concentration Photovoltaic (HCPV) Systems in Dammam City

In this study, enhanced net channel based heat sink designs for cooling HCPV systems at geometrical concentration ratios ranging from 500× to 3000× are presented. The effect of increasing the number of layers in the parallel flow net channel, as well as the fraction of the coolant mass flow rate in the counter flow net channel, on the overall performance of the HCPV systems, are investigated. The various configurations of each proposed net channel based-heat sink design are examined, and a comparative analysis between the different proposed designs is performed under the climate weather conditions of Dammam city, Saudi Arabia. On one hand, the double-layered counter flow net channel heat sink outperformed the other designs in terms of electrical efficiency and in keeping the solar cell operating well below the safe operating limits, achieving a reduction in maximum cell temperature relatively compared to the parallel flow net channel with five layers and conventional mini channel of 11.72% and 12.01%, respectively. On the other hand, for effective usability of the heat recovery rate by the cooling mechanism, the parallel flow net channel is the most appropriate design since it has recorded 27.55% higher outlet water temperature than the double-layered counter flow net channel.

Modeling and optimization of turbulent flow through PEM fuel cell cooling channels filled with metal foam- a comparison of water and air cooling systems

One of the proposed methods to improve the performance of a proton exchange membrane fuel cell is using metal foam within the channels. Here, we performed a 3D numerical simulation and studied the effect of structural properties of metal foam on the system performance. Also, we used artificial neural network to predict three criteria, i.e., maximum temperature, temperature uniformity index, and pressure drop, together with Genetic Algorithm for system optimization. Obtained results indicate that using metal foam can improve the temperature uniformity in the cell, so that maximum temperature and temperature uniformity index are decreased about 1.785 K and 0.7 K, respectively, while resultant increase in overall pressure drop of the system is only about 4.4%. The same amount of maximum temperature reduction is possible by increasing the flow rate; however, this scheme puts 60% more pressure drop upon the system. Moreover, we compared the performance of air- and water-cooling systems and found that for a given pressure drop, the maximum temperature as well as temperature uniform index of an air-cooling system is lower than that of a water-cooling system, while for the same system parasitic power, a system with water coolant has more uniform temperature distribution with lower maximum temperature.

Thermal and Performance Efficient On-Chip Surface-Wave Communication for Many-Core Systems in Dark Silicon Era

Due to the exceedingly high integration density of VLSI circuits and the resulting high power density, thermal integrity became a major challenge. One way to tackle this problem is Dark silicon. Dark silicon is the amount of circuitry in a chip that is forced to switch off to insure thermal integrity of the system and prevent permanent thermal-related faults. In many-core systems, the presence of Dark Silicon adds new design constraints, in general, and on the communication fabric of such systems, in particular. This is due to the fact that system-level thermal-management systems tend to increase the distance between high activity cores to insure better thermal balancing and integrity. Consequently, a designing dilemma is created where a compromise has to be made between interconnect performance and power consumption. This study proposes a hybrid wire and surface-wave interconnect (SWI) based Network-on-Chip (NoC) to address the dark silicon challenge. Through efficient utilization of one-hop cross the chip communication SWI links, the proposed architecture is able to offer an efficient and scalable communication platform in terms of performance, power, and thermal impact. As a result, evaluations of the proposed architecture compared to baseline architecture under dark silicon scenarios show reduction in maximum temperature by 15∘C, average delay up to 73.1%, and energy-saving up to ∼3X. This study explores the promising potential of the proposed architecture in extending the utilization wall for current and future many-core systems in dark silicon era.

Energetic and thermal comfort assessment of phase change material passively incorporated building envelope in severe hot Climate: An experimental study

Phase change materials (PCMs) can beneficially work as a successful thermal energy storage medium in different applications. PCMs have shown a remarkable enhancement in building energy-saving and thermal comfort in hot locations. In this paper, the thermal behaviour of a PCM-enhanced thermally-poor building envelope is studied experimentally. To this aim, two identical rooms, one loaded with PCM (PCM room) and the other without (reference room), are built and tested under a severe hot climate of Al Amarah city, Iraq. Previously examined parameters, such as the optimal position and thickness of the PCM layer in the roof and the best-thermally performed PCM capsules integrated concrete bricks, are considered to build the PCM room. Several energetic and thermal comfort indicators such as maximum temperature reduction (MTR), average temperature fluctuation reduction (ATFR), decrement factor (DF), time lag (TL), operative temperature difference (OTD), discomfort hours reduction (DHR) and maximum heat gain reduction (MHGR) are determined and discussed to show the potential of PCM. The experimental results revealed that the incorporated PCM could remarkably improve the thermal performance of building envelope exposed to high outdoor temperatures. Amongst envelope elements and compared with the reference room, the roof and east wall of the PCM room recorded the best thermal behaviour, where the MTR difference, ATFR, DF, and TL difference reached 3.75 °C, 6.5 °C, 25.6%, 70 min for the roof, and 2.75 °C, 2.4 °C, 12.8% and 40 min for the east wall, respectively. Moreover, the PCM room shows a thermal comfort enhancement by 11.2% and 34.8%, considering the DHR and MHGR, respectively, compared with the reference one. The study highlighted that suitable ventilation means are necessary to improve the building performance and reach acceptable thermal comfort when the PCM is incorporated passively.

Spatiotemporal climate variability in the Andes of northern Peru: Evaluation of gridded datasets to describe cloud forest microclimate and local rainfall

AbstractTropical montane cloud forest may be especially sensitive to climate change. However, our ability to understand effects of climate on montane biodiversity remains limited by the resolution of climate data. We compared 5 years of in situ weather data from cloud forests in northern Peru, regional weather stations, and gridded datasets to examine how climatologies reflect (a) forest microclimate buffering and (b) local rainfall in a sparse data region; we also examined spatiotemporal variability and regional trends. Across a 1,700–3,100 m gradient in which temperature did not covary with relative humidity (RH), in situ data showed interactions between climate and land‐use. Forest humidity buffered warming‐induced evaporative drying across elevations, and inside forest maximum vapour pressure deficit (VPDmax) did not change with elevation, whereas with a 22% reduction in RHmin at stations, VPDmax increased >10‐fold from high to low elevations. Cloud forest dried out on sunny days after 3 days without rain, especially during ENSO‐related drought concurrent with peak solar insolation. Climatologies were twice as precise for temperature as rainfall. Chelsa captured a 3.9°C reduction in maximum temperatures inside forest (MAE 1.6°C, R2 = 0.95) whereas WorldClim reflected drier lapse rates and higher Tmax outside forest. CHIRPS provided the best fit for monthly rainfall (MAE 23 mm, R2 = 48), capturing regional drought but underestimating rainfall >150 mm·month−1. Consistent with stations, CHIRPS showed strong support for regional increases in wet‐season rainfall. Reduced variability and more regular dry seasons were only detected by montane stations, especially south of 6°S, where rainfall seasonality shifted to earlier wet‐season peaks and reduced dry‐season rainfall as part of a transition from the Northern to Central Andes. Our results show that cloud forests may be partly buffered from warming but are likely to become extremely vulnerable under reduced humidity either through forest loss or drought.

Thermo-regulating performance of concrete slab loaded with shape stabilized phase change material in tropical climate

The building overheating problem is one of the most important problems facing all over the world. Various methods like using highly thermal resistive building materials, composite building materials were used to reduce the heat gain of the buildings. One of the method which can be used in place of traditional methods is using building elements with high thermal energy storage capacity. The significance of this study is to improve the thermal energy storage capacity of the building element for improving indoor thermal performance of the building. In this study latent heat energy storage capacity of the concrete slab is enhanced by incorporating Shape Stabilized Phase Change Material (SS-PCM) in it. SS-PCM was prepared by incorporating eutectic PCM (Paraffin Wax 70% and Coconut Oil 30%) in highly porous material called zeolite. The zeolite powder successfully incorporate 30 wt% PCM without showing any leakage at elevated temperature. Morphology of the SS-PCM was evaluated through Scanning Electron Microscopy (SEM) images. The SS-PCM at 0 wt%, 10 wt%, 20 wt%, and 30 wt% was used to prepare composite concrete slab by replacing fine aggregates. Composite concrete slabs were tested for indoor thermal behavior in real outdoor testing of 72 h. Indoor thermal performance was evaluated on the basis of peak temperature reduction, thermal amplitude, time delay, and decrement factor. The 30% SS-PCM has a high latent heat capacity, which significantly improves thermal energy storage in buildings. Various parameters like peak temperature reduction, time lag, thermal amplitude and decrement factor were evaluated. Concrete slab integrated with 30% SS-PCM shows maximum peak percentage temperature reduction of 10.04 % and percentage reduction in thermal amplitude of 23.71 % in comparison to conventional concrete. Additionally, infrared thermography of all the concrete slabs at different time of the day was done.

Design, development, and analysis of modified concrete block integrated with thermal energy storage material for regulating indoor temperature

This study shows a comparative analysis of indoor thermal behavior of concrete block embedded with macroencapsulated phase change material with fins and without fins. Concrete blocks of similar dimensions were incorporated with square shape, rectangular shape, cylindrical shape, square shape with fins, rectangular shape with fins, and cylindrical shape with fins macroencapsulated phase change material. Pure paraffin wax (70 wt%) and raw coconut oil (30 wt%) are used as phase change material. Real outdoor testing of all the modified concrete block in comparison with conventional concrete block was conducted for continuous 96 h. Various indoor thermal comfort parameters such as peak temperature, thermal amplitude, and decrement factor were investigated. Additionally, thermographic images were also analysed to understand the effect of incorporating various shapes of macroencapsulated phase change material. Result shows maximum peak temperature reduction of 8.43 °C by concrete block integrated with cylindrical shape macrocapsule with fins. Also, concrete block integrated with cylindrical shape macrocapsule with fins shows highest reduction in indoor thermal amplitude of 26.54 % followed by cylindrical macroencapsulated phase change material without fins in comparison with reference concrete block. Lowest deviation in thermal amplitude shows by rectangular shape macrocapsule with fins. Reduction in decrement factor was also observed in modified concrete blocks in comparison with reference concrete block.

Enhanced radiative cooling of solar cells by integration with heat pipe

Thermal management of solar cells is of vital importance to maintain adequate electrical efficiency. Lately, radiative cooling (RC) of solar cells has been researched extensively because of its passive nature and structural simplicity. However, commercial solar cells are usually encapsulated with highly emissive glass covers, and therefore the additional potential to reduce the cell temperature through RC is not significant. This study proposes a new system configuration to maximize the RC potential. It consists of a photovoltaic module for electricity generation, an RC module for heat removal to the sky, and a heat pipe for quick and efficient heat transfer between the two modules. A comparative analysis of temperature reduction and efficiency improvement between the proposed and previously studied systems is performed. The influence of input parameters (i.e., solar radiation, ambient temperature, wind speed, atmospheric emissivity, radiator length, and heat pipe resistance) on the system performance is also studied using COMSOL. Results show that in contrast to the conventional glass-coated module, the proposed system gives a maximum cell temperature reduction of 12.86 °C, which corresponds to a 7.25% relative rise in electrical efficiency. The new configuration's enhanced thermal performance supports it as an alternative to the glass-coated or ideally emissive photovoltaic modules. By addressing the challenge of limited radiative sky cooling, researchers can eventually move a step ahead and use this study for the thermal management of other devices and not just solar photovoltaics.

Evaluation of the properties and carbon sequestration potential of biochar-modified pervious concrete

Adding biochar (BC) into cementitious materials to replace partial cement is a win-win strategy for both cement output reduction and hygrothermal properties improvement of cement-based composites. However, how to coordinate the different functions to achieve the optimized performance of BC-modified pervious concrete remains scarcely reported. This study is aim to explore the influence mechanism of BC prepared from construction wood waste on strength, water absorption, thermophysical properties and evaporative cooling performance of pervious concrete. The results show that when the BC content is 1.0–3.0 wt% (by weight), the compressive/flexural strength of BC-modified pervious concrete is higher than that of BC-free one, but the strength will be compromised if the content exceeds this value. The water absorption capacity of pervious concrete gradually increases with BC contents. Although the presence of these black carbonaceous particles will induce more solar radiation absorption, the increased solar absorption can be offset by the extra absorbed water via evaporative cooling. BC-modified pervious concrete performs a better cooling performance, with a maximum temperature reduction of 10 °C and a duration of about 12 h. Moreover, taking producing 1 m3 concrete as an example, it reveals that CO2 emissions reduced 15% when 8.0 wt% BC is used instead of cement as compared to the control sample.

A novel thermal regulation of photovoltaic panels through phase change materials with metallic foam-based system and a concise comparison: An experimental study

The thermal regulation of photovoltaic (PV) modules is utmost necessary as temperature enhancement of PV panels deteriorates its conversion efficiency. Different studies have been done in the literature to regulate the temperature of module by using various fluids and materials which include air, water, nanofluids as well as phase change material (PCM). The current research studies four various types of PV configurations with the aim of enhancement in cell efficiency. These four configurations include reference panel, PV panel having only PCM, PV panel having PCM with foam of thickness 8 mm and PV panel having PCM along foam with 12 mm thickness. This is the novelty of the current research that PCM with foam have not studied yet in photovoltaic cooling. The PT58 and RT44 were used as phase change materials along with aluminum foam having 8 mm and 12 mm thickness. The experimentation was done under the environment of Taxila, Pakistan during the month of February. The maximum efficiency of PV module is found by the configuration having PCM with foam of 12 mm thickness. The result of experimentation depicts that reduction in maximum temperature by using RT44 along with foam was 11.21 °C for PV panel having only PCM, 20.95 °C for PV panel having PCM with foam of thickness 8 mm and 24.39 °C for PV panel having PCM along foam with 12 mm thickness with highest conversion efficiency 11.68 % , 11.79 % , 12.06 % respectively in comparison to naturally cooled PV module. Similarly, the lowering in temperature using PT/58 along with foam was 3.33 °C for PV panel having only PCM, 6.9 °C for PV panel having PCM with foam of thickness 8 mm and 9.03 °C for PV panel having PCM with foam of thickness 12 mm respectively having highest electrical efficiency 11.32 % , 11.50 % , 11.77 % respectively as compared to reference module. The increment in maximum percentage electrical power was 23.30 % for PV panel having RT44 PCM along foam with 12 mm thickness. The higher thickness of foam along with base phase change material depicted best results with maximum decrement in temperature of PV panel as well as maximum enhancement in conversion efficiency as compared to less value of foam thickness with base PCM. Therefore, this study is especially attractive to young researchers who are working in thermal management of photovoltaic.

Recovery and effective utilization of waste heat from the exhaust of internal combustion engines for cooling applications using ANSYS

The exhaust gases from an internal combustion (IC) engine carry away about 75% of the heat energy which means only 25% of heat energy is operated for power production. A recovery unit at the exhaust outlet port can ensure heat exchange between different temperature fluids through conjugate heat transfer phenomena. This study represents heat recovery from exhaust gases that are emitted from IC engines which can be utilized in various applications such as vapor absorption refrigeration systems. In the present work, a new type of perforated fin heat exchanger for waste heat recovery of exhaust gases is designed using SolidWorks, and the flow field design of the heat recovery system is optimized using ANSYS software. Various parameters (velocity, pressure, temperature, and heat conduction) of hot and cold fluid have been analyzed. Inlet velocity of cold fluids including refrigerant (LiBr solution), water, and graphene oxide (GO) nanofluid have been adopted at 0.03 m/s, 0.165 m/s, and 0.3 m/s, respectively. Inlet velocity of hot fluid is taken as 2 m/s, 4 m/s, and 6 m/s, respectively, to develop a test matrix. The results showed that maximum temperature reduction by the exhaust is achieved at 104.8°C using graphene oxide nanofluids with an inlet velocity of 0.3 m/s and exit velocity of 2 m/s in the heat recovery unit. Similarly, temperature reduction by exhaust gases is acquired at 102 °C using water and 96.34 °C by using a refrigerant (LiBr solution) with the same exit velocity (2 m/ s). Furthermore, maximum effectiveness of 0.489 is also obtained for GO nanofluid when compared with water and the refrigerant. On the other hand, the refrigerant has the maximum log mean temperature difference from all fluids with a value of 224.4 followed by water and GO.

Highly suppressed solar absorption in a daytime radiative cooler designed by genetic algorithm

Abstract Here, we report a selective multilayer emitter for eco-friendly daytime passive radiative cooling. The types of materials and thickness of up to 10 layers of the multilayer structure are optimized by a genetic algorithm. The passive radiative cooler is designed to mainly target low solar absorption, which allows sub-ambient cooling under direct sunlight. We used a custom objective function in the solar region to achieve high-performance daytime radiative cooling to minimize solar absorption. The designed structure minimizes solar absorption with an average absorptivity of 5.0% in the solar region (0.3–2.5 μm) while strongly emitting thermal radiation with an average emissivity of 86.0% in the atmospheric transparency window (8–13 μm). The designed and fabricated structure achieves daytime net cooling flux of 84.8 W m−2 and 70.6 W m−2, respectively, under the direct AM 1.5 solar irradiation (SI) (total heat flux of 892 W m−2 in the 0.3–2.5 μm wavelength region). Finally, we experimentally demonstrate a passive radiative cooling of the fabricated selective emitter through a 72-hour day-night cycle, showing an average and maximum temperature reduction of 3.1 °C and 6.0 °C, respectively. Our approach provides additional degrees of freedom by designing both materials and thickness and thereby is expected to allow high-performance daytime radiative cooling.