Heat Gain Research Articles

On the Significance of Hydrate Formation/Dissociation during CO2 Injection in Depleted Gas Reservoirs

Summary The study aims to quantitatively assess the risk of hydrate formation within the porous formation and its consequences on injectivity during storage of CO2 in depleted gas reservoirs considering low temperatures caused by the Joule-Thomson (JT) effect and hydrate kinetics. Hydrates formed during CO2 storage operation can occupy porous spaces in the reservoir rock, reducing the rock’s permeability and thus becoming a hindrance to the storage project. The aim was to understand which mechanisms can mitigate or prevent the formation of hydrates. The key mechanisms we studied included water dry-out, heat exchange with surrounding rock formation, and capillary pressure. A semicompositional thermal reservoir simulator is used to model the fluid and heat flow of CO2 through a reservoir initially composed of brine and methane. The simulator can model the formation and dissociation of both methane and CO2 hydrates using kinetic reactions. This approach has the advantage of computing the amount of hydrate deposited and estimating its effects on the porosity and permeability alteration. Sensitivity analyses are also carried out to investigate the impact of different parameters and mechanisms on the deposition of hydrates and the injectivity of CO2. Simulation results for a simplified model were verified with results from the literature. The key results of this work are as follows: (1) The JT effect strongly depends on the reservoir permeability and initial pressure and could lead to the formation of hydrates within the porous media even when the injected CO2 temperature was higher than the hydrate equilibrium temperature; (2) the heat gain from underburden and overburden rock formations could prevent hydrates formed at late time; (3) permeability reduction increased the formation of hydrates due to an increased JT cooling; and (4) water dry-out near the wellbore did not prevent hydrate formation. Finally, the role of capillary pressure was quite complex, as it reduced the formation of hydrates in certain cases and increased in other cases. Simulating this process with heat flow and hydrate reactions was also shown to present severe numerical issues. It was critical to select convergence criteria and linear system tolerances to avoid large material balance and numerical errors.

Study of parabolic trough collector with crucial analysis on controller and estimator with variable mirror efficiency

Solar Thermal Power (STP) plants are a crucial technology for converting solar energy into electricity. Among the STP, the Parabolic Trough Collector (PTC) is one of the integral parts of STP systems for electrical power generation. Maximizing PTC performance is a challenge due to dynamic and unpredictable solar radiation and environmental disturbances, such as cloud cover and dust accumulation. The optical efficiency parameter of the PTC is critical for calculating the desired heat gain, which is difficult to measure in real-time, necessitating sophisticated control and estimation strategies for optimal heat regulation. This study introduces two control mechanisms for the PTC system and comparing their efficacy. A classical PI controller supplemented by Static Feed-Forward (SFF) control demonstrates improved performance with an optimal transfer function model. In contrast, Nonlinear Model Predictive Control (NMPC) excels in disturbance rejection and setpoint tracking, considering operational constraints. The NMPC controller notably outperforms the PI controller with SFF in performance metrics, with the Integral Time Squared Error (ITSE) decreasing by approximately 99% across case studies. Also, in the case of heat gain, NMPC controller exhibits percentage increases when compared to the PI controller. Furthermore, since the measurement of optical efficiency is essential, but due to difficulty in the measurement for various reasons, the estimator is used as a virtual sensor to estimate those optical efficiency. The unmeasured states and parameters, including optical efficiencies of the PTC, are estimated using Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) techniques, with UKF exhibiting superior accuracy. However, considering the average computation time, EKF is preferred for real-time applications.

Effect of cold beverages on whole-body heat exchange in young and older males during intermittent exercise in the heat.

To mitigate health risks associated with occupational heat stress, workers are advised to adhere to a work-rest regimen, and hydrate regularly. However, it remains unclear if beverage temperature influences whole-body heat exchange during work-rest cycles, and if responses differ in older workers who have a blunted heat loss capacity. Ten young (mean [SD]: 22 [3] years) and 10 older (60 [4] years) males performed four 15-min bouts of moderate-intensity cycling at a fixed rate of metabolic heat production (200 W·m-2), each interspersed by 15-min rest in dry heat (40°C, ~12% relative humidity). On separate days, participants consumed either ice-slurry (~0°C), standardized to provide a heat transfer capacity of 75 kJ·m-2, or an identical mass of warm fluid (37.5°C) before the first and third exercise bouts. Evaporative and dry heat exchange (direct calorimetry) and metabolic heat production (indirect calorimetry) were measured continuously to determine cumulative heat storage (summation of heat loss and heat gain) over the entire protocol. Rectal temperature was also measured continuously. Relative to warm fluid, ice-slurry ingestion reduced cumulative heat storage in young (69 [181] vs. 216 [94] kJ) and older males (90 [104] vs. 254 [140] kJ, main effect: p < 0.01), but was unaffected by age (p = 0.49). However, rectal temperature was unaffected by beverage temperature in both groups (all p ≥ 0.15). We show that cold fluid ingestion is an appropriate administrative control for both young and older males as it can mitigate increases in body heat content during moderate-intensity work-rest cycles in dry heat.

Climate-responsive wada architecture: a bioclimatic design for climate change resilience

ABSTRACT With rising living standards and a growing global population, the energy consumption of buildings is predicted to soar. Energy efficiency and occupant comfort may both be enhanced by constructing buildings with climate-sensitive design principles in mind. The traditional architectural style of a given region, known as vernacular architecture, has changed throughout the years to accommodate the local climate. One example of a vernacular style of building that made use of climate-responsive design to produce energy-efficient and aesthetically pleasing structures is the Wada style, which is located in the Pune region of India. The performance of the traditional Wada House envelope and its thermal characteristics are being researched in this study. This study investigates the thermal performance of traditional Wada houses, utilizing simulation models, validation, and analyzing climate change scenarios for 2050 and 2080. Research shows that passive design principles are widely used in Wada architecture to control inside temperatures and cut down on energy usage. Insulation through thick walls and roofs, orientation to reduce solar heat gain, and natural ventilation are all part of these measures.

Evaluating conventional and renewable energy systems for green buildings: A case study on energy efficiency and cost optimization

This study explores two primary categories of power generation: conventional methods reliant on fossil fuels and renewable energy methods. Fossil fuel-based approaches, including natural gas and heavy fuel oil, contribute to environmental concerns due to their carbon dioxide (CO2) emissions, which are responsible for the greenhouse effect and global warming. Many nations, particularly in Europe, have implemented stringent measures to restrict CO2 emissions, imposing fines on industries that exceed emission limits. In response to these concerns, this study focuses on a green building project that aims to meet its power requirements through renewable energy sources. Various renewable energy resources will be evaluated, considering the merits and drawbacks of each technology, to identify the most suitable option for the building under investigation. Additionally, a comprehensive thermodynamic analysis will be conducted, including calculations of electrical needs such as cooling load, lighting load, and equipment load. A customized power calculator will also be developed for application in similar projects. The ultimate objective of this study is to achieve complete autonomy from the electric grid by utilizing renewable energy resources, transforming the building into a green building. The results indicate that at an outside temperature of 22 °C, the total heat gain decreases from 157.3 to 39 kW, reducing the total cost of electricity from 20,000 to 5100 AED/year. Conversely, at an outside temperature of 50 °C, the total heat gain increases from 157.3 to 196 kW, raising the total cost of electricity from 20,000 to 26,000 AED/year. These findings demonstrate the significant influence of outside temperature on the building's energy requirements and costs, underscoring the importance of considering temperature variations in energy efficiency and cost optimization strategies.

Thermal response in Boer goats differing in coat colour

Context The coat is the first defense layer protecting animals from direct sunlight, influencing radiant-heat absorption and loss. Dark coat colour may increase animal heat impact because of higher absorption of solar radiation. Aims We investigated the impact of pigmentation intensity on the heads of animals and their thermal responses to solar radiation. Furthermore, we compared the thermal responses between dark and light brown-coloured animals, to determine whether the duration of sun and shade exposure (3 h each) is sufficient to differentiate the heat gain and losses between the two groups. Methods The effect of coat colour on rectal and surface temperatures in Boer goats, classified according to their head pigmentation pattern as dark (DB, N = 11) or light brown (LB, N = 11), exposed to sun and shade, was evaluated. The animals’ body and head surface temperatures were measured the same day before, during, and after sun exposure by using infrared thermography. Individual thermographic images were analysed by body regions (rump, leg, neck) and head areas (eye, ear, upper and lower part of the head, and the muzzle). Key results During solar radiation, all measured variables increased. In the shade, the rump, leg, and neck surfaces remained elevated, whereas the head area cooled down faster, with the highest temperature changes measured for the ear of about 10%. Most surface cooling occurred within 30 min after returning to the shade. Coat colour groups differed only in higher overall muzzle temperature of DB than that of LB goats (P = 0.048). Correlations between rectal and surface temperatures were low to medium, ranging from −0.02 (eye) to 0.31 (muzzle). Conclusions The head area is suggested as the important thermal window for heat dissipation and selective brain cooling. Light brown-headed animals were more efficient in eliminating the heat gained from solar radiation when returned to shade. Implications The colouration of the animal’s head may play an important role for its heat tolerance. As an easy-to-recognise characteristic, coat colour can serve as a selection trait for local goat populations. In view of global warming, selection for lighter coat colour in domestic ruminants may also become important even under temperate climates.

Comparative analysis of hydrogel-based thermotropic glazing and fixed horizontal overhangs in building performance

Thermotropic (TT) glazing is able to achieve energy-saving capabilities similar to external shading devices by dynamically regulating solar heat gain transmitted through windows in response to ambient climatic conditions. However, the building performance of TT glazing compared to traditional shading devices remains underexplored. This study aims to bridge this knowledge gap by comparing the building performance of hydrogel-based TT glazing and fixed horizontal external shading devices in terms of building energy consumption, daylighting performance, and thermal comfort. Experimental tests were conducted over a continuous ten-day period, focusing on the indoor temperature and illumination distribution within experimental rooms equipped with either TT glazing or fixed horizontal external shading device. Building performance models were developed using EnergyPlus and validated with experimental data. Subsequently, a comparative analysis was then conducted to evaluate the impact of TT glazings and fixed horizontal external shading devices on building energy consumption, daylighting performance, and thermal comfort across five typical climate conditions in China. The findings indicated that: (1) In five climate zones, TT provided the greatest energy savings in West-facing orientations, followed by East-facing orientations. (2) TT can replace fixed horizontal external shading device with a certain length to achieve similar building energy efficiency and indoor thermal comfort performance. (3) In regard to daylighting performance, TT achieved the desired values of sUDI<100lx,50 % and sUDI300–3000lx,50 % across all four orientations in the five climates. (4) In terms of thermal comfort, TT improved thermal comfort by reducing the annual daytime average PPDoverheating across all orientations in the five climate zones.

Highly insulated hydrogen powered vacuum gasochromic smart windows for energy-efficient buildings

Switchable active hydrogen powered gasochromic smart windows present an appealing option for energy-efficient building integration, offering two controllable transparencies between ON and OFF states compared to traditional windows. Implementing such glazing in cold-climate buildings requires minimizing the total heat transfer across the glazing, achievable through vacuum-insulated glazing resulting in the retrofitting to obtain energy efficient building. This study investigates the potential of vacuum gasochromic (VGC) windows to enhance the energy efficiency of buildings in diverse climatic conditions, focusing on London, UK, and New Delhi, India. Comparing traditional single-glazing and double-glazing windows with vacuum-gasochromic windows in terms of thermal performance, energy demand, and dynamic control over solar heat gain and visible light transmission are evaluated using advanced simulation techniques with SketchUp, OPTICS6, WINDOW 7.8 and EnergyPlus 9.6. Results reveal that vacuum gasochromic windows exhibit superior thermal insulation with significantly lower U-values of 1.559W/m2K, reducing heat transfer and energy demand for heating and cooling. Vacuum gasochromic opaque states demonstrate exceptional performance in minimizing energy transfer, making them the most energy-efficient option, especially in warm climates like New Delhi with 9544.4 kWh. Conversely, vacuum gasochromic transparent state shows promise in reducing heating demand in London's cold climate by 9.43 %, highlighting their adaptability. Moreover, vacuum gasochromic windows allow dynamic control over solar heat gain and visible light transmission, enabling occupants to adjust transparency based on weather conditions and preferences.

A Review of Three-Dimensional RGB Images and Drone Thermal Camera Images Merged for Building Information Modeling for Energy Audit

The site visit is the core of the energy audit, where you inspect, measure, and document the building's energy performance and efficiency. Various tools and techniques may be used for this purpose, such as a walk-through survey to observe the building's condition, a blower door test to measure air tightness and infiltration, a thermographic scan to detect heat loss and gain, a lighting audit to assess lighting quality, quantity, and controls, a plug load audit to quantify appliance and equipment energy consumption, a submetering or data logging system to monitor specific systems or zones, and a power quality analyzer to measure electrical parameters and harmonics. Additionally, it is important to interview the building's owner, manager, and occupants in order to gain their feedback and suggestions on energy performance and issues. This paper review of how a drone can help in the energy audit of a building using thermal images and RGB images from thermal camera which will be use in Building Information Modelling (BIM). There are a variety of relevant literatures that serve as sources of inspiration for the conduct of this study. One example is the utilization of teleoperated helicopters that are equipped with an infrared thermal camera. These helicopters are intended to be investigated for energy audits in order to readily assess the conditions of the structure. More improvements will be made to the collected photographs, such as merging them with three-dimensional RGB images. This will allow for an exact determination of which area of the building need upgrading in order to reduce the amount of energy that is emitted; this notion is similar to that of finite element analysis.

Solar Collectors with Nanofluid for Domestic Applications: A Review

Energy management and the usage of renewable energy sources are essential for a sustainable future. This paper carried out a review and summarize the recent topic of solar collectors heating water for use in a domestic application. Several researchers have studied solar collectors with flat plates, evacuated, and concentrators to improve heat gain for heating water. Entropy is an important function that the attention of investigators to reduce and increase the thermal efficiency of solar collectors. Nanofluid has been selected as have found a new class of thermal efficiency enhancement for this purpose. Thermal performance is enhanced by changing the geometry of the absorber plate of the solar collector and the evacuated tube is the best. It was found that increasing nanoparticle concentration to 4% improves solar collector efficiency to 30%. It was observed that the report of solar-collector enhancement by changing geometry and fluid flow through the solar-collector.

Resilient cooling of the Mediterranean office spaces under climate change

ABSTRACT Resilient cooling strategies can minimize overheating risks by reducing energy demands and providing healthy indoor environments. Envelope-based resilient cooling strategies are particularly crucial for limiting external heat gain through conduction, convection, and radiation. This paper examines the impact of these strategies on the indoor environment under climate change. Using a case study approach, we simulate various scenarios for single and combined envelope-based resilient cooling strategies in a hypothetical, free-running office building located in the Mediterranean across five Köppen-Geiger climate zones (BSh, BSk, BWh, Csa, and Cfa) for both historical and 2050 weather data. We calculate indoor overheating degree and evaluate occupants' adaptive comfort. The findings suggest that combining envelope-based resilient cooling strategies significantly reduces indoor overheating risks, particularly in Southern European and North-Western African cities. Strategies that effectively control solar exposure are more influential in mitigating these risks. Among the strategies examined, a ventilated double skin with low-SHGC or chromogenic glazing is the most climate-change-resilient. This study contributes to the field by assessing the effectiveness of envelope-based resilient cooling strategies and providing recommendations for their application in the Mediterranean climate. It also evaluates how climate change may impact the performance of these strategies, offering insights for design and policymaking.

Enhancing Daylight Comfort with Climate-Responsive Kinetic Shading: A Simulation and Experimental Study of a Horizontal Fin System

This study employs both simulation and experimental methodologies to evaluate the effectiveness of bi-sectional horizontal kinetic shading systems (KSS) with horizontal fins in enhancing daylight comfort across various climates. It emphasizes the importance of optimizing daylight levels while minimizing solar heat gain, particularly in the context of increasing energy demands and shifting climatic patterns. The study introduces a custom-designed bi-sectional KSS, simulated in three distinct climates—Wroclaw, Tehran, and Bangkok—using climate-based daylight modeling methods with the Ladybug and Honeybee tools in Rhino v.7 software. Standard daylight metrics, such as Useful Daylight Illuminance (UDI) and Daylight Glare Probability (DGP), were employed alongside custom metrics tailored to capture the unique dynamics of the bi-sectional KSS. The results were statistically analyzed using box plots and histograms, revealing UDI300–3000 medians of 78.51%, 88.96%, and 86.22% for Wroclaw, Tehran, and Bangkok, respectively. These findings demonstrate the KSS’s effectiveness in providing optimal daylight conditions across diverse climatic regions. Annual simulations based on standardized weather data showed that the KSS improved visual comfort by 61.04%, 148.60%, and 88.55%, respectively, compared to a scenario without any shading, and by 31.96%, 54.69%, and 37.05%, respectively, compared to a scenario with open static horizontal fins. The inclusion of KSS switching schedules, often overlooked in similar research, enhances the reproducibility and clarity of the findings. A physical reduced-scale mock-up of the bi-sectional KSS was then tested under real-weather conditions in Wroclaw (latitude 51° N) during June–July 2024. The mock-up consisted of two Chambers ‘1’ and ‘2’ equipped with the bi-sectional KSS prototype, and the other one without shading. Stepper motors managed the fins’ operation via a Python script on a Raspberry Pi 3 minicomputer. The control Chamber ‘1’ provided a baseline for comparing the KSS’s efficiency. Experimental results supported the simulations, demonstrating the KSS’s robustness in reducing high illuminance levels, with illuminance below 3000 lx maintained for 68% of the time during the experiment (conducted from 1 to 4 PM on three analysis days). While UDI and DA calculations were not feasible due to the limited number of sensors, the Eh1 values enabled the evaluation of the time illuminance to remain below the threshold. However, during the June–July 2024 heat waves, illuminance levels briefly exceeded the comfort threshold, reaching 4674 lx. Quantitative and qualitative analyses advocate for the broader application and further development of KSS as a climate-responsive shading system in various architectural contexts.

Investigating the performance of an affordable parabolic dish collector with double glass vacuum cavity cover

Parabolic dish collectors (PDC) are one of the most important ways to concentrate solar energy. In this study, the performance of a low-cost parabolic dish collector with high average output temperatures is investigated. The low-cost PDC has a 45 ° edge angle and a circular receiver. A vacuum double-glazed cavity is used to keep heat inside the receiver and reduce the rate of heat losses. On clear and cloudy days, tests were conducted with thermal oil as a heat transfer fluid (HTF) to analyze the performance of the PDC. The results show that the change in temperature of the heat transfer fluid between the open and closed ends of the cavity receivers affected the receiver heat gain, thermal efficiency, and exergy efficiency. It was also found that the HTF has the highest exit temperature of 221 °C, with an average radiation intensity of 1032 W/m2. With 48.4 % thermal efficiency and 9.1 % exergy efficiency, the results showed the best performance. When it came to total efficiency, PDC showed its highest value of 46.2 % at 13:17 p.m. on January 4th, 2024.

A review of complex window-glazing systems for building energy saving and daylight comfort: Glazing technologies and their building performance prediction

The increasing energy consumption and detrimental CO2 emissions contributing to global warming underscore the urgent necessity for energy conservation, especially within buildings. Among different building components, fenestration plays a pivotal role as it accounts for the majority of heat transfer across the building envelope. This emphasises the significance of window-glazing technologies in enhancing their thermal performance. Furthermore, window-glazing systems can lead to overheating issues, particularly in summer, and glare issues, especially in winter. These challenges have spurred the development of various advanced glazing systems. This paper provides a comprehensive review of these advanced glazing technologies based on their functionalities and working principles, with a focus on parameters such as U-value, solar heat gain coefficient and visible transmittance. Among these technologies, vacuum and aerogel glazing systems exhibit superior thermal insulation properties, with U-values below 1 W/m2 K, making them suitable for heating-dominated climates. Smart window systems, such as electrochromic windows, are ideal for cooling-dominated climates due to their low solar heat gain coefficient (0.09–0.47) and visible transmittance (0.02–0.62). Photovoltaic window systems not only provide effective thermal insulation and solar shading but also produce additional power for on-site use. Some of these glazing systems feature complex structures, which present challenges when integrating them into existing building simulation software to assess their impact on building performance. Therefore, this paper also examines techniques for conducting energy and daylight performance simulations for buildings that make use of complex window systems. Ultimately, the authors propose an approach to characterise the thermal, optical and electrical properties of a complex photovoltaic window system within existing building simulation software, such as EnergyPlus. This approach facilitates a thorough investigation into the effects of complex window systems on building energy efficiency and indoor comfort.

Sustainable building envelopes: Evaluating the thermal performance of thatched roofs fabricated using coconut leaves

Excessive heat gain in residential buildings during sunny days, especially in tropical regions, leads to increased reliance on active energy cooling systems, contributing to higher carbon emissions and energy costs. Traditional roofing materials, such as terracotta tiles are often insufficient in mitigating indoor temperature rise, necessitating the exploration of alternative, sustainable solutions. This study investigates the thermal performance of naturally available coconut leaves used as thatch roofing, comparing it with conventional terracotta tiles, to determine their effectiveness in controlling interior temperatures and reducing heat gain in buildings. To mitigate such a problem, the Near Infra-Red (NIR) light reflectivity of dried plant leaves derived from deciduous and coniferous trees was measured. The structural hierarchy of the leaves was confirmed through Field Emission Scanning Electron Microscope (FESEM), Fourier Transform Infrared Spectroscope (FTIR) and X-ray Diffraction (XRD) studies. FTIR spectra reveal characteristic vibrations of ester, cellulosic components, etc., and XRD confirms the amorphous status of cellulosic materials present in the plant biomass. To study the use of thatched roofs made using coconut leaves as a roofing element, two test huts were fabricated - one was covered using terracotta roof tiles and the other was covered using coconut leaves thatches. The thermal performances of two roofing materials were recorded on a sunny day and the results were compared. The temperature data noticed reveal the fact that the maximum average surface temperature of the terracotta roof model was 59.53 °C, while the rooftop covered with coconut thatches exhibits a temperature of 54.26 °C which is 8.8% less than the hut covered with terracotta tiles. The interior temperature recorded in the coconut thatch was 33.36 °C, which was 1.15 °C lower (34.51 °C) than the terracotta tiles-covered test hut, confirming the better thermal comfortability of thatched roof model than a terracotta roof model.

Occupational Heat Exposure-related Symptoms Prevalence and Associated Factors Among Hospitality Industry Kitchen Workers in Ethiopia: Wet Bulb Globe Temperature

BackgroundOccupational heat stress caused by excessive environmental heat gain disrupts thermoregulatory mechanisms and harm workers' health and productivity. Kitchens are known for their thermal risks; however, research on heat stress in kitchen is limited. This study aimed to bridge this knowledge gap by assessing, the prevalence of heat-stress-related symptoms, and associated factors among kitchen workers in Gondar City, Ethiopia. MethodsThis institutional-based cross-sectional study (April to June 2023) evaluated heat stress among hospitality kitchen workers in Ethiopia. Heat exposure was measured using hygrometers. A simple random sample of 605 participants completed a survey and data was exported to Statistical Package for Social Science version 26. To assess strength and direction an adjusted odds ratio with 95% confidence interval (CI) was employed. A p-value of less than 0.05 was utilized to identify significant associations. ResultsOver the last 6 months 67.1% (95% CI: 63.0, 71.1), of the participants reported heat-stress symptoms. Multivariable analysis revealed that age ≥40 years [AOR: 2.28; 95% CI (1.08, 4.82)], high workload [AOR: 1.89; 95% CI (1.04, 3.49)], poor heat mitigation practice [AOR: 2.39; 95% CI (1.58, 3.59), wood fuel [AOR: 2.60; 95% CI (1.54, 4.40)], improper ventilation [AOR: 3.28; 95% CI (1.56, 6.87)], and higher heat index value [AOR: 2.15; 95% CI (1.35, 3.42)] were factors significatly associated with heat stress related symptoms. ConclusionThis study identified a high prevalence of heat–stress-related symptoms among kitchen workers. Mitigation strategies include improved ventilation, cooling, advanced building designs, and heat reduction technologies. Future research should utilize standard heat-stress assessment tools.

Experimental study on the thermal performance of a high-temperature finned latent heat storage system

The primary objective of this study is to develop and evaluate the performance of a latent heat storage (LHS) system. A tube-in-tube heat exchanger configuration was used to design the LHS system. Sodium nitrate and air were employed as the phase change material (PCM) and heat transfer fluid (HTF), respectively. To mitigate the low thermal conductivity of the PCM, six circular fins were integrated on the HTF tube surface and experiments were conducted in an in-house experimental facility. Temperature plots from the charging-discharging experiments revealed that the HTF flow direction governs the heat transfer along the axis of the system. The sensible heat gain by the PCM in the range of 270–330 °C, led to an additional ⁓0.4 MJ of heat storage beyond the storage capacity of 1 MJ. Furthermore, increasing the inlet temperature from 400 °C to 440 °C reduced the charging time by 39.6 %, while reducing the inlet temperature from 210 °C to 170 °C decreased the discharging time by 18.2 %. Despite improved heat transfer, higher inlet temperatures adversely affected the thermal uniformity whereas, the increase in inlet air velocity enhanced both the dynamics of heat transfer and the thermal uniformity within the storage system.

An Innovative Energy Storage System Based on Phase Change Material and Solar Energy Integrated With an Air Handling Unit to Produce Heating and Cooling

ABSTRACTThis study investigates the potential of using phase change material (PCM) in a building using an air handling unit (AHU) assisted by solar energy. To further enhance the system, an energy storage system (ESS) can be considered. Implementing ESS would allow the captured solar energy to be stored efficiently, ensuring a continuous and reliable power source for cooling or heating the air, even during non‐sunlight hours. The air‐conditioned zone is considered to be 220 m2 in which 30 people work for 12 h a day. An energy analysis is conducted to evaluate the performance of the proposed system in terms of energy and exergy loss. The genetic algorithm (GA) method is used to optimize the system. The results indicate that the system, including PCM and solar system, can reduce energy consumption by up to 8.9% compared to conventional AHUs in the hottest month of the year (July). The results indicated that employing PCM leads to a decrease of 124 kWh in heat loss during January and 229 kWh in heat gain during July. Taking into account the beneficial impacts of both PCM and the solar system, the yearly assessment demonstrates a 2.69% reduction in power demand, equating to an energy saving of 679 kWh. Furthermore, PCM in the proposed system can be used in integration with AHUs based on renewable energy systems to store renewable energy for buildings.

International inter-laboratory comparison of solar heat gain coefficient of building-integrated photovoltaic modules results of tests with or without power generation and tests with PV cell coverage ratios

The solar heat gain coefficient is one of the important indicators to evaluate the performance of the building envelope components. In a BIPV module, secondary heat transfer to the indoors is reduced, compared to conventional glazing, due to the shielding effect of the PV cells and energy conversion by power generation. There is a difference in SHGC between power-generating (MPP) and effectively open-circuit (OC) states. In this paper, in order to prepare a calorimetric SHGC evaluation methodology for BIPV modules, we documented the current status of the experimental calorimetric test methods and test apparatus adopted by test laboratories in four different countries and identified the differences. Differences between the test laboratories were found in to the applied test methods, solar simulator types, spectral distributions, DC or AC power supplies for the solar simulator, irradiation inhomogeneity on the light-receiving surface of the test sample, temperature conditions between the test chamber and the metering box, and surface heat transfer coefficients. Especially, the round-robin test results obtained in an interlaboratory comparison clarified that the differences in the characteristics of the Calorimetic Hot Box and the Heat Flux Metering methodologies with a cooled plate, the differences in irradiation inhomogeneity on the light-receiving surface of the test sample and differences in surface heat transfer coefficients significantly affect the SHGC evaluation for BIPV modules. In addition, for the SHGC test in the MPP state, it was confirmed that an absolute SHGC reduction effect of 0.02 to 0.04 was obtained for a PV laminate with 81 % cell coverage, for all SHGC test methods and test apparatus. Pe characterises the effect of converting part of the sunlight absorbed by the PV cell into electric power and extracting it from the BIPV module, reducing the heat re-radiated indoors compared to the OC state. Due to this mechanism, the reduction effect Pe always occurs during power generation, regardless of the type of PV cell technology and whether the PV cells are opaque or transparent. In addition, the decrease in SHGC for a given glazing configuration was found to be proportional to the increase in PV cell coverage ratio. SHGC tests with four different cell coverage ratios confirmed that the relationship between PV cell coverage ratio and SHGC is linear to a high degree of accuracy when no electric power is extracted (OC state), provided that the incident radiation is spatially homogeneous. The results obtained will be useful when proposing a calorimetric SHGC evaluation methodology for international standardization, as they document the differences due to a range of test facilities and testing conditions, differences caused by power generation and extraction, and the effect of varying PV cell coverage ratios. The insights gained were valuable in identifying which aspects of test methodology and boundary conditions must be specified with particular attention to detail when calorimetric testing standards are extended to explicitly address the SHGC determination of BIPV modules.

Solar PV vacuum glazing (SVG) insulated building facades: Thermal and electrical performances

As fire emergencies and energy saving demand of buildings have grown around the globe, concerns have been raised about the flammability of conventional external insulation materials in cold weather areas. In this paper, solar PV vacuum glazing (SVG) was proposed as a promising alternative to traditional external insulation layers of buildings due to its incombustible nature and superior thermal insulation performance. To assess the thermal and electrical performances of SVG-insulated facades, a heat transfer model and an effective absorptance calculation model for SVG-insulated façades were developed and validated against experimental data. Results showed that SVG-insulated facades exhibited significantly lower U values, ranging from 44.1% to 47.5% less than those of traditional concrete walls (without insulation layer). Additionally, the application of Low-emissivity (Low-e) coatings on the glazing could further reduce the U value from 2.05 W/(m2·K) to 0.647 W/(m2·K), making SVG-insulated facades competitive with traditional insulation walls. The secondary heat transfer factor (SHTF), defined as the ratio of indoor heat gain from solar radiation absorbed by building facades to incident solar radiation, was also reported for SVG-insulated facades with different solar cells (C-si, A-si, and CdTe), along with their respective efficiencies. Parametric analyses of eight parameters subsequently highlighted that their influence on the thermal performance of SVG-insulated façades was much greater than on the solar cell efficiency. Furthermore, considering the combined effect of optimal value of key influencing parameters, the lowest U value of 0.153 W/(m2·K) could be achieved, which represents approximately 24.6% of the U value of traditional insulation walls. This study provides compelling evidence for the adoption of SVG-insulated facades as replacements for traditional insulation walls and offers insights into optimizing their thermal performance.