Heat Gain Research Articles

Robust multi-objective building design optimization approach using NSGA-II algorithm considering weather and occupant uncertainties

A novel methodology is presented to evaluate how real-world operational uncertainties impact multi-objective building design optimization process. NSGA-II algorithm is applied across nine distinct operational scenarios, considering diverse weather datasets and energy usage patterns to optimize energy efficiency and thermal comfort in a residential building within India's hot and dry climate. The analysis considers 382,400 possible design options for each scenario. Using (10.5–12.5) % of model evaluations, NSGA-II significantly reduces Annual Cooling Energy Demand (ACED; 46.7%–58.7%) and Cooling Set-point Unmet Hours (CSUH; 70.92%–86.93%) to identify nine Pareto–Optimal solution sets. The final robust optimal design is confirmed by selecting the most repeated parameter settings, representing the highest robustness. Low thermal transmittance walls, double-glazed windows with a 10% window-to-wall ratio (WWR), deep overhangs, and a low solar heat gain coefficient are recognized as robust optimal building components. However, Air Conditioner (AC) sizing lacks robustness in minimizing energy demand across scenarios, requiring case-specific evaluation due to its sensitivity to weather and operational variations. Further, PAWN sensitivity analysis highlighted the substantial impact of WWR (KSWWR ∼ (0.46–0.66)) and wall type (KSWall ∼ (0.31–0.46)) on ACED and CSUH in chosen climate. AC operation is more important for predicting CSUH (KSAC ∼ 0.35) than ACED (KSAC ∼ 0.10).

Night-time radiative warming using the atmosphere

Night-time warming is vital for human production and daily life. Conventional methods like active heaters are energy-intensive, while passive insulating films possess restrictions regarding space consumption and the lack of heat gain. In this work, a nanophotonic-based night-time warming strategy that passively inhibits thermal radiation of objects while actively harnessing that of atmosphere is proposed. By using a photonic-engineered thin film that exhibits high reflectivity (~0.91) in the atmospheric transparent band (8–14 μm) and high absorptivity (~0.7) in the atmospheric radiative band (5–8 and 14–16 μm), temperature rise of 2.1 °C/4.4 °C compared to typical low-e film and broadband absorber is achieved. Moreover, net heat loss as low as 9 W m−2 is experimentally observed, compared to 16 and 39 W m−2 for low-e film and broadband absorber, respectively. This strategy suggests an innovative way for sustainable warming, thus contributes to addressing the challenges of climate change and promoting global carbon neutrality.

Perovskite Smart Windows: The Light Manipulator in Energy-Efficient Buildings.

Uncontrolled sunlight entering through windows contributes to substantial heating and cooling demands in buildings, which leads to high energy consumption from the buildings. Recently, perovskite smart windows have emerged as innovative energy-saving technologies, offering the potential to adaptively control indoor solar heat gain through their impressive sunlight modulation capabilities. Moreover, harnessing the high-efficiency photovoltaic properties of perovskite materials, these windows have the potential to generate power, thereby realizing more advanced windows with combined light modulation and energy harvesting capabilities. This review summarizes the recent advancements in various chromic perovskite materials for achieving light modulation, focusing on both perovskite structures and underlying switching mechanisms. The discussion also encompasses device engineering strategies for smart windows, including the improvement of their optical and transition performance, durability, combination with electricity generation, and the evaluation of their energy-saving performance in building applications. Furthermore, the challenges and opportunities associated with perovskite smart windows are explicated, aimed at stimulating more academic research and advancing their pragmatic implementation for building energy efficiency and sustainability.

Building Envelope Performance to Achievement of Energy-Efficient Buildings : a case study analysis in Ulil Albab Mosque Yogyakarta

The performance of the building envelope is one of the most important in energy-efficient buildings. As the outermost layer, the building envelope will be very decisive for heat transfer from outside to inside the building. The performance of the building envelope in heat transfer refers to as the Overall Thermal Transfer Value (OTTV). OTTV measures the average heat gain into the building through the building envelope. It is a measure widely adopted in many countries to improve the design of energy-efficient buildings. The OTTV value strongly influences the ratio of transparent openings on the building facade. The size of the transparent opening will affect the inclusion of natural lighting in the building. This study aims to see how closely the relationship between the OTTV value and the achievement of natural lighting in buildings according to standards. The values used as success standards are the GBCI and SNI parameters. This research expects to provide a reference for existing buildings to improve building performance, especially for energy efficiency. This study uses a simulation method with OTTV worksheets and DIAlux Evo calculations. The mosque chooses to be a case study because the mosque is a building that has a distinctive orientation. In this research, Ulil Albab mosque, Yogyakarta, for the case study. For the location of Yogyakarta, the Qibla direction is azimuth direction 294° 42′ 39.894″ (Northwest) from Yogyakarta, where the radiation factor value is the largest. The results of this study indicate that the OTTV value can follow the standard by lowering the percentage of WWR in a facade with a high radiation factor value. Still, a WWR that is too small can result in natural lighting being unable to enter the room. In this building, the most efficient thing to do is replace the transparent material with one with better thermal properties.

Unbalancing mean radiant temperature and air temperature

Radiant heating and cooling systems promise to provide heat transfer over large surface areas to enable lower temperature supply improving both supply efficiency and user comfort. Radiant panels provide both radiant and convective heat transfer. We investigate the balance of the heat transfer occurring via radiation and convection. A commonly referenced benefit of radiant panels is that the radiant heating or cooling delivered to occupants allows thermal perception to remain neutral while lowering or raising air temperatures, which in turn reduces heat losses or gains through the facade. In our previous work on radiant systems, we have observed that very rarely do air temperatures actually get set to more ideal temperatures alongside the radiant panels. Using the framework of a recent study of an office space in Singapore we present a simulation showing the breakdown of radiant and convective heat and the resulting air temperature in a simple heat balance model. We then use a computational fluid dynamics (CFD) model and analytical model to observe the relationship between air temperature and mean radiant temperature (MRT) through space. We find that it can take up to 40 kW of additional heat gain to successfully decouple the air temperature from the MRT generated by the panel by more than 2 °C. We also show that in the CFD model, while the air temperature and MRT remain relatively tightly coupled, the vertical spatial variation of MRT is significant, changing by more than 2 °C across the space from floor to ceiling.

Experimental study of the performance of a novel solution with double skin façade and diffuse ceiling ventilation

In Denmark, about 80% of public schools were built before 1980, and most of them are with the Energy label D or lower. In addition, more than 60% of schools suffer from poor air quality and thermal comfort. The need for school renovation is undeniable. A novel renovation solution was proposed recently by combining double-skin façade (DSF) and diffuse ceiling ventilation (DCV). The integrated system can adapt its operating modes based on indoor and outdoor conditions. The performance of the above-mentioned solution was tested in a small-scale classroom and compared to a reference room with the traditional renovation solution. The results show that the novel solution was able to provide better indoor comfort than the traditional solution. Although significant overheating was observed in both rooms, the novel solution showed promise in mitigating the maximum operative temperature and shifting the peak hour. In terms of energy efficiency, the novel solution optimized the utilization of natural sources. The DSF was able to recover the transmission loss through the glazing and capture the heat gain by solar radiation. The heat recovery rate reached 1 when the solar radiation was strong.

The Effect of Shading Position on The Thermal Comfort Commercial Buildings Through Energy Retrofitting

The Surabaya building sector is a prime target for energy efficiency initiatives, given its substantial contribution to overall energy consumption. Commercial buildings, often filled with glass to harness natural lighting, inadvertently raise room temperatures and increase cooling demands. Thus, ensuring thermal comfort within these structures becomes paramount. An energy use survey reveals that air conditioning accounts for a significant 62% of consumption, underscoring the need for retrofitting, especially in commercial buildings. This study centers on retrofitting strategies, focusing on the application of shading devices to glass exteriors, aimed at reducing solar heat gain and, consequently, heat transfer through the building envelope. The research investigates two shading positions: horizontal and vertical, each with specific opening angles and width variations. The Computational Fluid Dynamics method, assisted by CFD software, serves as the simulation tool, exploring shading opening angles at 0°, 30°, and 45°, and shading widths at 20% and 60% of the window glass height. Simulation results highlight the efficacy of horizontal shading, boasting a 60% width of the glass height and a 45° opening angle, which reduces temperatures by a significant 2.5278°C. Additionally, a cost-benefit analysis reveals substantial electricity consumption savings post-retrofitting, amounting to 7619.9 kWh. This translates to best-case cost savings of Rp15,586,068 and worst-case savings of Rp10,390,712, with respective payback periods of 1.57 and 2.52 years.

Waste-Energy Nexus: Cellulose Wood Chips Conjugated Metal Nanoparticles Based Phase Transformation for Improving Thermal Energy Storage Performance.

Highlighting waste as a wealth is the future sustainability of the world. Also, using solar energy stored during off-sun periods will overcome the energy crisis. The introduction of wood chip waste for thermal energy storage systems is a sustainable opportunity. Cellulose derived from wood chips was mixed with the environmentally benign magnetite to form a composite (WCM) and mixed with paraffin-based PCM. The composite was characterized through transmission electron microscopy, TEM analysis, scanning electron microscopy, SEM (augmented with dispersive X-ray analysis, EDX). Micrographs, Fourier transform infrared (FTIR), and X-ray diffraction (XRD), which confirmed that the composite material was prepared. Various system proportions of the composite (0.5, 1.0, 2.0, and 4.0%) are embedded in paraffin, and then the thermal system performance is compared. The experimental data revealed that the addition of 2.0 weight percent of composite material showed superior system performance. Also, differential scanning calorimeter (DSC) and TEM analyses of the paraffin-based WCM-composite materials are conducted. The system achieved a heat gain of 87 kJ/min in comparison to 7 kJ/min for 2.0% WCM-PCM and pristine PCM, respectively. Hence, WCM-PCM embedded with waste stream nanoparticles could be suggested as a potential candidate for heating applications.

Experimental investigation of an integrated renovation solution combining diffuse ceiling ventilation and double skin façade

A novel renovation solution was proposed recently by integrating diffuse ceiling ventilation and double skin façade. This study presents an experimental investigation on the performance of the novel solution in a small-scale classroom. The aim of this study was to evaluate the potential in combining the diffuse ceiling ventilation principle with the double-skin façade through the thermal comfort and passive energy performance evaluation in two operation modes: heating mode and cooling mode. The performance of the novel solution was compared to a traditional renovation solution installed in an identical room. The results showed that the novel solution achieved comparable or even superior thermal comfort than traditional renovation solution. In winter, the DSF is able to recover the transmission loss through the glazing and capture the heat gain by solar radiation. The heat recovery rate can reach up to 1.2 when solar radiation was strong. In summer, the air ventilated the DSF cavity and served as an air curtain to remove part of the heat gain. Consequently, it reduces the heat gain to the room and maintains lower indoor temperature than the traditional solution. Benefit of the further activation of thermal mass, the novel solution can reduce the peak operative temperature and shift the peak hour to later of the days. Further research is needed to optimize the system's control strategies and integrate solar shading device in the control strategy.

Selecting the Optimal Thermal Insulation Material for a Residential Building Envelope in Cairo in Consideration of The Thermal Comfort and Energy Consumption

As a result of the current global energy crisis, there is a universal tendency towards energy-saving in the housing sector. In Egypt, mega housing projects such as "Dar Misr" are established to provide apartments for middle-income families. The envelopes of those buildings play a significant role in the increased heat gain of indoor spaces. Therefore, this study aims to assess the thermal performance and calculate the energy savings of five thermal insulation materials available in the market; (Vermiculite, Rockwool, Phenolic Foam, Extruded Polystyrene (XPS), and Polyethylene). The assessment is for those materials installed in the apartment's external walls to find the optimal material that achieves the most extended annual indoor thermal comfort hours and the highest annual energy-saving. An apartment in a typical floor was modeled by DesignBuilder software to calculate the indoor thermal comfort hours and energy consumption for the five alternatives. The results show that thermal insulation materials inside the external walls are pivotal in reducing heat gains and extending comfort hours. The optimal insulation material is XPS which achieved thermal comfort for 33% of the year compared to 28% and 29% by the Phenolic Foam and Rockwool, respectively. Moreover, the XPS saved 9.27% of the annual energy consumption, which is the highest energy-saving ratio compared to Polyethylene (6.21%) and Vermiculite (2.4%).

Smart double glazing integrated polymer dispersed liquid crystal for enhancing building's thermal performance in hot-arid climate

Polymer-dispersed liquid crystal glazing is an electrically activated smart switchable glazing that requires an AC power supply to become transparent and remains opaque without power. This dynamic feature, with multiple transparency states, is suitable for building in hot and arid climates. It can effectively reject unwanted solar energy, allowing visible light while contributing to building energy efficiency by reducing the carbon footprint. In this work, the PDLC glazing system was included with a low-e coated glass and this coupled system was investigated with two control approaches for residential buildings in hot arid climates. The first control is a standard On-Off operation based on the tenant preferences, while the second is able to set glazing transparencies according to the solar radiation intensity, in order to minimize the penetration of direct solar radiation and to provide daylighting and indoor privacy protection. The system is reversed to examine the proper positions and layer order in the glazing system. The proposed system demonstrates remarkable enhancements in indoor thermal performance, surpassing clear glass by 21 % in the south orientation and 25.5 % in the west orientation. Furthermore, when the PDLC is oriented towards the outdoor environment, the system achieves an impressive 53.9 % improvement in heat gain control compared to clear glass. Additionally, the system not only enables dynamic control over direct solar radiation but also offers efficient daylighting and indoor privacy protection.

Determination Of Optical Constant of a Clear Glass Material for Accurate Daylighting and Solar Heat Gain Assessment Using Spectrophotometer Measurements

Many qualities make glass attractive, as it is transparent, chemically inert, environmentally friendly, sustainable, strong, easily available and relatively cheap. Recently, many researchers have been interested in designing the buildings to get the benefit from daylight inside, which saves a lot of building consumption for artificial lighting, which gives visual and thermal comfort and also contributes to reducing costs. The complex refractive index of glass is a very crucial concept because it determines not only how much light is reflected and transmitted, but also its angle of refraction in glass. The optical constants of glass material are very useful for determining its radiative properties, as well as for selecting the appropriate thin-film coatings on a glass substrate. The objective of this study is to calculate the real part (n) and the imaginary part (k) of the complex refractive index of a clear glass material using a simple method based on the reflectivity and transmissivity measurements. In this study, the parts n and k are derived from the equations of the reflectivity at near zero incidence and transmissivity at normal incidence by using Shimadzu IR-70 Spectrophotometer and Cary 5E Spectrophotometer apparatuses. The real and the imaginary parts of the complex refractive index of the glass sample obtained in the present study are in very good agreement with Rubin’s data. Although, a direct comparison between different samples is not possible, due to the difference in manufacturing process and material composition.

Experimental and numerical study on thermal performances of a modular hydronic thermal barrier wall with heat injection system in filler cavities

The hydronic thermal barriers with dynamically adjustable thermal performance have become one of the highly anticipated solutions for opaque envelope insulation while improving the efficiency of the use of low-grade energy. In response to the technical constraints encountered by conventional hydronic thermal barrier walls (i.e., CHTBs) when it comes to enhancing heat transfer, the concept of modular hydronic thermal barrier walls (i.e., MHTBs) was introduced. The MHTB incorporates a heat injection system within its filler cavities, a feature designed to promote the overall thermal performance of the opaque enclosure structure. The performance enhancement described is mainly achieved through active management of the thermal conductivity of the filling material within the vicinity of fluid pipes. In this study, field thermal performance assessments were carried out during winter conditions in three reduced-scale experimental rooms. The southern boundary of these test rooms adopts walls with different configurations, i.e., MHTB, CHTB, and traditional thermal insulation wall. Subsequently, a comprehensive investigation regarding the impacts of filling materials on the energy performances of MHTB was conducted through numerical simulations. The outcomes demonstrated a substantial reduction in heat loss through the south wall by using MHTB, leading to reduced room thermal discomfort. In particular, with a charging temperature set at 35.0 °C, the inner surface temperature of MHTB displayed a noteworthy increase of 10.3 °C compared to that of the traditional thermal insulation wall, resulting in a significant reduction in heat load by a factor of 7.4. Additionally, it was observed that the filler material within the pipe cavity played a vital role in shaping MHTB's thermal performance. For instance, considering the case with a heat injection temperature of 25.0 °C, a doubling of thermal conductivity resulted in an enhancement of 0.24 W/m2 in heat gain on the outer surface and an overall increase of 0.04 MJ in total injected heat. This study demonstrated the positive effect of MHTB on optimizing the efficiency of hydronic thermal barriers and guided their further application and research.

Numerical analysis of the heat exchange model with the ground on the example of a complex of industrial halls

This paper describes the process of validation of the numerical model and its calibration, based on long-term field studies that were carried out at a growing tunnel system for Agaricus bisporus in southern Poland. A verification of uncertainty indices was undertaken, based on which the applicability of the model for further research and analysis was assessed according to commonly used guidelines. WUFI®plus software was applied based on the numerical elementary balance method (EBM). The HVAC system was also simulated in order to reflect actual conditions as accurately as possible. The correctness of the model was assessed by means of uncertainty indicators in the form of the normalised mean deviation error (NMBE) and the Coefficient of Variation of the Root Mean Square Error CV (RMSE). The analysis provided an opportunity to highlight the validity of the calculations, considered reliable under the criteria adopted. It also pointed out some limitations of the model applied, resulting in negative calibration results for a small number of selected measurement monitors. Using the validated calculation model, heat flows from the ground to the building and the other way around were estimated. The specifics of the building contributed to the occurrence of heat gain from the ground being 20 times larger compared to energy losses to the ground. This opens up a potential path for extending the numerical analysis to optimise energy management for the investigated facility and to determine the thermal interaction between buildings in the surveyed area.

Demand-Oriented Review of a Dynamic Energy-Loss Monitoring System for Primary School Buildings through Micro-Environmental Data Monitoring and Occupant Behavior Analysis

The utilization of primary school buildings is multifaceted, primarily due to the high occupancy density, varying thermal preferences among occupants, diverse indoor activities (such as walking, sports, and conversation), and a constant flow of individuals entering and exiting the building. This results in the frequent opening and closing of external windows and doors and fluctuations in internal heat gain. Consequently, frequent interactions between the indoor and outdoor microenvironments lead to energy losses. This study conducts a comprehensive literature review on building energy loss stemming from occupant behavior and the interactions between indoor and outdoor microenvironments. Furthermore, it proposes a dynamic real-time monitoring system based on a foundation of computer data capture and a visualization platform for building energy loss. The research methods include data crawling, data association rule mining, and data association analysis. The research findings yield a universally applicable and informative building energy-saving design system based on extensive data analysis. Additionally, the system presents information on occupants’ behavior and the microclimate data of indoor and outdoor environments on a computer screen, facilitating human–machine communication and enabling timely adjustments to be made, thus facilitating the construction of design strategies for new buildings and operation and maintenance strategies for existing buildings.

Experimental study on thermal performance of finned tube water flow window

Water flow window is an advanced energy-saving building façade, and the design of the heat exchanger affects the thermal performance directly. A novel finned tube water flow window (FTWFW) applying a finned tube heat exchanger is proposed. Its thermal performance, with regard to energy savings and the thermal environment created under various operating conditions, is studied experimentally. The reduction in indoor heat gain reached 88.1% compared with insulated glazing unit, and the average daily water heat gain efficiency was 65.2% during the summer testing. The inner glazing surface temperature of FTWFW was more stable and closer to the comfort room temperature, especially under non-air-conditioning condition in winter, resulting in enhanced thermal comfort. Moreover, increasing the flow rate or decreasing the temperature of feed water can improve the thermal performance of FTWFW in summer. In winter, compared to increasing the feed water flow rate, raising the feed water temperature was more effective in increasing the room temperature. The advantages of FTWFW in cooling/heating energy saving, thermal collection, and thermal comfort enhancement were well demonstrated. Its large-scale application is expected to make contributions in green and low-carbon building development. The findings of this study can helpful in decision making of real projects.

Shading effect and energy-saving potential of rooftop photovoltaic on the top-floor room

Rooftop photovoltaic panels can serve as external shading devices on buildings, effectively reducing indoor heat gain caused by sunlight. This paper uses a numerical model to analyze rooftop photovoltaic panels' thermal conduction, convection, and radiation in hot summer areas as shading devices. The researcher builds an experimental platform to verify the model, exploring the potential for energy savings of photovoltaic rooftop units in the Wuhan area. The results show that after installing photovoltaic panels, the delay performance of the roof increases by 0.5 h, the roof heat flux is reduced by 41.7%, the peak temperature of the roof is reduced by 22.9 °C, and the daily heat gain is reduced by 74.84%. Finally, this paper discusses the impact of high-reflectance and low-reflectance roofs on the shading effect. The study finds that low-reflectance roofs are more energy-efficient in the hot summer, as high-reflectance roofs lead to a 10.8% increase in indoor heat gain when the photovoltaic panel is installed. Finally, a quantitative method for evaluating the comprehensive potential for energy savings is proposed, considering the electricity generation gain of photovoltaic panels and the comprehensive energy-saving efficiency of photovoltaic roofs, which generates a total potential for energy savings rate of 61.06%. The model presented in this paper provides theoretical guidance for analyzing the comprehensive energy-saving effects of photovoltaic rooftop systems and reveals the potential for energy savings of rooftop photovoltaic panels as external shading devices.

Influence of passive solar gains on the energy consumption of a typical house in Algiers

The purpose of a bioclimatic house is to make every effort to reduce the need for heating and cooling. For this a well studied architecture of the house is essential: - the positioning of windows to capture the maximum solar radiation, - Good thermal insulation of the house to reduce heat loss. This study focuses on the effect of solar and internal heat gain on the energy consumption of a typical well insulated house. The degree day’s method is used to determine the heat losses by transmission and ventilation according to international standards on thermal insulation of building (NBN B62-301), the results are very interesting and promising. By including the solar and internal gains, which vary from 900 to 1400 kWh, the energy consumption decreases significantly. The thermal load for heat reaches 60 kWh, but by including the free thermal gains, 10 kWh of energy can be saved daily.

Modified shape coefficient of building with Thermal considerations: concept, experiment and Application in solar-enriched areas

ABSTRACT The shape coefficient of building (SCB) characterizes the correlation between building shape and building energy consumption. Strictly restricting the SCB was harmful to reducing energy consumption, neglecting the potential benefits of solar radiation. A novel concept and determining method of modified shape coefficient of building (MSCB) were proposed based on the energy dissipating and solar heat gain. Field measurements of the indoor air temperature of model buildings for solar radiation, building orientations, and U-values under natural and heating conditions were conducted in western Sichuan. Results demonstrated that with identical SCB, the indoor thermal environment was substantially affected by the above parameters, proving the one-sidedness of SCB simultaneously. A simulation method verified via the experiments was employed to forecast the dynamic heating load of a real building. The influence of building orientations on the MSCB under actual climatic conditions from different time scales was discussed. Results illustrated that the SCB could be reduced by 34.6% in the present case. The monthly correction factor trend and the heat consumption were consistent. The restriction on SCB could be liberalized moderately even if the heating demand was tremendous. This research could provide a reference for the energy-saving design of passive buildings.

A retrofitting framework for improving curtain wall performance by the integration of adaptive technologies

Energy efficiency and the reduction of carbon emissions have become the main climate goals for newly constructed or existing buildings. In the building sector, curtain walls (CWs) account for the majority of unwanted solar heat gain and consume most of the energy used. In this context, adaptive technologies (ATs) offer a wide range of alternative solutions to improve the performance of CWs. This study aims at developing a comprehensive framework for retrofitting CWs through the integration of ATs. Based on a comprehensive analysis of previous literature, the proposed three-stage framework provides a guide for enhancing the performance of CWs by evaluating and comparing retrofitting scenarios using ATs. The three stages include pre-retrofit survey, retrofit process, and monitoring process. To achieve this goal, curtain wall systems, retrofitting levels, and sub-practices are discussed. The integration ability of ATs into CW systems is assessed according to functional, structural, and technical properties. Integration scenarios are evaluated based on SWOT analysis, performance criteria, adaptive parameters, and retrofitting practices to assess their efficiency. Results show that integration scenarios of materials like electrochromic and semi-transparent photovoltaic glazing are applicable to all CW systems with remarkable performance enhancement. Phase change materials and liquid infill tunable glazing are the least applicable materials. Integration scenarios of adaptive systems involving green walls and dynamic shading devices provide the greatest functional benefits. Whereas, algae facades should only be installed in newly constructed buildings. In conclusion, the study proves that the integration of ATs into CWs offers promising potential for improving CW performance.