The location of the two rooms with (S.kh) and without (S.w.kh) a Kharkhona.
The rate of decrease of PMV, PET and SET* of S.kh compared to Sw.kh during the different hours of the day.
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...Achieving thermal comfort in buildings is one of the major concerns of studies in energy in buildings. One of the ways to achieve thermal comfort is to study and optimize vernacular solutions, especially in extreme climates. The Sistan region in the east of Iran is one of the special climatic regions in the world. The present study was conducted to achieve the thermal comfort conditions quantitatively updating one of the vernacular architectural techniques of the Sistan region called Kharkhona. Accordingly, the authors performed field measurements in two rooms with and without a Kharkhona on certain days and hours in the summers of 2019, 2020, and 2021. The results revealed that, on average, the thermal comfort index of PMV was 1.39 units lower, the PET index was 7.69 °C lower, and the SET* index was 3.98 °C lower than the room without a Kharkhona and throughout the day and night in the space with a Kharkhona. Moreover, based on the semantic range of PMV, PET, and SET*, it was determined that by creating a Kharkhona, the thermal perception of the room without Kharkhona was moderated primarily from the very unfavorable status of hot and very hot to much more favorable status of warm and comfortable with a Kharkhona. This change in this status is due to the presence of the Kharkhona and its positive climatic impacts, so it could bring the extreme climatic condition of the Sistan region closer to a comfortable thermal condition in a closed space..
•Liquid-desiccant air-conditioning system applied to a high-latent-load building.•A vapor compression cooling system is chosen as a reference system for comparison.•Onsite indoor thermal comfort and ...energy performance of both systems are analyzed.•Proposed system saves 92.4% of energy, achieving thermal comfort in rainy weather.•Proposed system saves 12.1% of energy, achieving thermal comfort in summer weather.
Indoor humidity control is increasingly important because indoor sensible heat ratio decreases to reduce building energy consumption. However, reference vapor compression cooling systems exhibit energy inefficiency and limitations in maintaining indoor thermal comfort. Therefore, this study proposes an alternative heat-pump-driven liquid-desiccant air-conditioning system, independently controlling air temperature and humidity. The reference and proposed systems are applied to a high-latent-load building to investigate their onsite indoor thermal comfort and energy performance empirically and simultaneously under various outdoor summer conditions. The reference system exhibits a thermal comfort satisfaction ratio of 97% only under limited hot and dry weather. Conversely, the thermal comfort satisfaction ratio sharply drops to 2% or less under humid weather. The proposed system consistently achieves a high thermal comfort satisfaction ratio exceeding 90% under various outdoor summer conditions. In empirical comparisons, the proposed system can maintain a thermally comfortable room for an hour while achieving energy savings exceeding 92.4% and 12.1% under warm and humid (rainy season) and hot and humid outdoor conditions, respectively. The proposed system is concluded to consistently maintain indoor thermal comfort while using energy efficiently, demonstrating its widespread applicability for general high-latent-load buildings characterized by low indoor sensible heat ratio values of 0.56 on average.
•Challenges of optimal control for active storages for fast DR are addressed.•The linear state-space model is developed for online MPC control.•Simplified parameter identification and self-correction ...for the MPC are developed.•Both expected power reduction and acceptable indoor environment are satisfied.•Cooling discharging rate of storages and chiller power demands are optimized by MPC.
Demand response (DR) can effectively manage electricity use to improve the efficiency and reliability of power grids. Shutting down part of operating chillers directly in central air-conditioning systems can meet the urgent power reduction needs of grids. But during the special events of fast DR, how to optimally control the active cold storage considering the indoor environment of buildings and the needs of grids at the same time is rarely addressed. A model predictive control (MPC) approach, with the features of shrunk prediction horizon, self-correction and simple parameter determination of embedded models, is therefore developed to optimize the operation of a central air-conditioning system integrated with cold storage during fast DR events. The chiller power demand and cooling discharging rate of the storage are optimized to maximize the building power reduction and meanwhile to ensure the acceptable indoor environment. Case studies are conducted to test and validate the proposed method. Results show that the proposed MPC approach can effectively handle the optimal controls of cold storage during DR events for required power reduction and acceptable indoor environment. Due to the feedback mechanism of MPC, the control performance is not negatively influenced by the simplified parameter identification of models, which will be convenient for real applications. While achieving the expected building power reduction for the power grid, the indoor environment is effectively improved in the DR events using the MPC and the maximum indoor temperature is reduced significantly without extra energy consumed.
The human neck is one of the most thermally sensitive body regions to nociceptive stimuli. Neck cooling has been extensively researched to improve athletic performance in the heat. However, there has ...been very little research into the use of conductive neck cooling for indoor thermal comfort. We thereby designed three ultralight cooling collars with cooling gels or phase change materials (GEL6, PCM15, and PCM18). Their cooling performance on thermal comfort enhancement of 14 healthy young female participants under two warm indoor temperatures (28 °C and 30 °C) was investigated. Thermophysiological and perceptual responses, including skin temperature, heart rate, sweating, thermal sensation vote (TSV), thermal comfort vote (TCV), and thermal preference vote (TPV), were extensively studied. Results showed that, in contrast to GEL6, PCM15 and PCM18 significantly decreased the neck skin temperature, with PCM15 exhibiting the greatest reduction of 4.37 °C at 28 °C. PCM15 and PCM18 significantly decreased overall and local TSVs while also increasing overall and local TCVs (all p < 0.05), thus they could maintain >80 % occupant satisfaction at 28 °C. At 30 °C indoor temperature, however, none of these three cooling collars were found to meet the 80 % occupant satisfaction criterion. When compared to GEL6, PCM15 and PCM18 were found to only significantly reduce local TSVs at the head and neck (all p < 0.05). In sum, PCM15 and PCM18 have the potential to increase acceptable HVAC summer cooling setpoint temperature by 2.5 °C, from 25.5 °C to 28.0 °C, leading to a 25 % reduction in building cooling energy consumption.
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•Cooling gels failed to maintain occupant thermal comfort at 28 and 30 °C temperatures.•Cooling collars PCM15 & PCM18 could maintain >80 % occupant satisfaction at 28 °C.•All cooling collars failed to meet the 80 % occupant satisfaction at 30 °C temperature.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.•PCM15 and PCM18 extended acceptable HVAC cooling setpoint temperature by 2.5 °C.
In order to improve the thermal performance of Trombe wall and make its active in a whole year, this paper proposed a novel Trombe wall integrated with double layers phase change material (PCM) named ...PCM Trombe wall. This paper studied the thermal performance of PCM Trombe wall numerically in winter and summer in Wuhan. The results showed that the PCM Trombe wall can improve indoor overheating in summer, and reduce indoor temperature fluctuations in winter. Therefore, the PCM Trombe wall can improve indoor thermal comfort and reduce cooling/heating load in the whole year compared with the traditional Trombe wall.
Developing countries encounter challenges in adopting advanced roof systems due to the complexities associated with implementing advanced materials and techniques. This study introduces an advanced ...four-stage approach as a combined technique, aiming to formulate an innovative affordable cool roof application that addresses the limitations of contemporary cool roof systems. The first stage involves reviewing Cool Roof Materials (CRMs) by classifying them into three categories: traditional, modern, and advanced roofing systems, with subclasses for each category. In the second stage, Affordable Green Materials (AGMs) are reviewed to suggest alternatives aligned with the study objectives. The third stage focuses on monitoring performance methods to evaluate applicability, while the fourth stage assesses the potential transformation of these alternatives into future fabrication processes. The study suggested a natural composite sandwich panel that incorporates three main layers, with multiple potential materials alternatives for each layer. The main panel consists of a reflective coating layer, a natural insulation composite layer, and a substrate layer. It could result in a significant 44 % decrease in surface temperature, with potential energy savings reaching up to 70 % and reductions in cooling loads of up to 51 %. It forms the basis of a new affordable cooling roof technology that effectively addresses the complexity of contemporary systems, potentially resulting in significant advances in passive cooling systems. The review also identifies areas requiring further research. Ultimately, this combination of environmentally friendly solutions could pave the way for holistic innovation in sustainable building design, contributing substantially to global climate objectives and energy-saving targets.
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•A novel four stage approach is introduced to optimize cool roof assessment.•The research addressed the potential materials used as a cool roof component.•The study systematically reviewed an overall 142 articles.•Results highlighted the potential of bio-composite insulation panels.
It is important to create a comfortable, healthy, and low-carbon indoor thermal environment that meets the thermal needs of the human body at different exercise levels and climatic conditions. ...Forty-five subjects participated in subjective investigation and objective physiological test in Xi'an at temperatures of 13.5–22.5 °C in winter. The results show that the PMV overestimates the actual thermal sensation of exercise human body and the thermal adaptability is stronger. There is a dynamic game phenomenon between exercise behavior and indoor temperature. The actual neutral temperature (16.1–14.8 °C) and the preferred temperature decreases with increasing exercise time. We obtain that the exercise population has better resistance to cold and constantly reduce the need for indoor temperature. It indicates that the subjects may prefer a neutral or slightly cooler thermal environment. Moreover, the synergistic effect of the exercise time and indoor temperature promotes the early occurrence of fatigue and shows significant physiological reactions. The 90% actual acceptable temperature range is wider than the ASHRAE Standard. The upper limit of indoor thermal environment design parameters of GB50189 is oversupplied. It indicates that the current design parameters are contradictory to the needs of exercise population. The human body is less dependent on heating energy consumption during exercise. Therefore, energy efficient thermal comfort can be achieved in sports buildings.
•Develop a thermal comfort evaluation model that combines the physiological indicators.•Energy efficient thermal comfort can be achieved in sports buildings.•The exercise behavior reduced demand of people for indoor temperature.•Clarify thermal comfort significant difference between exercise and quiet state.•Propose the recommendations for heating design parameters.
Diagrams of (A)conventional cool roofs, (B) super cool roofs, and (C) temperature-adaptive roofs whose color can change with temperature.
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•Cool roofs are divided into conventional ...cool roofs, super cool roofs, and temperature adaptive roofs.•The use of cool roofs is limited by geography and climate, with the net cooling power of up to 150 W/m2 in dry, rainless, and clear sky areas.•The use of cool roofs in cities may cause light pollution problems, which can be alleviated by special structures or materials.•Not only does atmospheric water vapor affect the radiative cooling power of cool roofs, but in turn, cool roofs can increase the water vapor content above the roof.•The large-scale use of super cool roofs may affect the urban wind field.
Cool roofs play a significant role in mitigating urban heat islands, improving indoor thermal comfort, and saving energy. In recent years, with advances in the manufacturing of nanophotonics and metamaterials, researchers have developed super cool roofs where the surface temperature remains below the air temperature in direct daylight and temperature-adaptive roofs where the solar reflectance or thermal emissivity can change with temperature. This paper reviews the research progress and status of conventional cool roofs, super cool roofs, and temperature-adaptive roofs. This paper affirms the role of cool roofs in mitigating urban heat islands and energy conservation. And this paper also summarizes some of the crucial issues that cool roofs may face when used in cities. The effects of cool roofs on urban wind fields, planetary boundary layer heights, and pollutants above cities as well as the effects of sky view factor, atmospheric humidity, dust, and aging on the performance of cool roofs are discussed. The results show that the use of cool roofs is limited by geography and climate. The net cooling power can reach 150 W/m2 in dry, rainless, and clear sky areas. Cool roof technology is less effective in hot and humid climates because the first atmospheric window is affected to varying degrees by the increased radiation medium in the atmosphere, while the second atmospheric window is nearly closed in hot and humid climates, weakening the terrestrial long-wave radiation entering space. The use of cool roofs in warm and humid climates (over 80% relative humidity, with temperature over 24 °C) for most summer nights may limit the radiative cooling performance of the cool roof. The large-scale use of cool roofs in cities near huge lakes or seas may affect the urban wind field, causing a cooling island effect and a local build-up of pollutants. Finally, an outlook on the research prospects of cool roofs was given to provide ideas for further research.
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•Active ventilation has been integrated into the PCM wall for solar heating.•The coupled heating system offers superior thermal storage efficiency.•Thermal storage and release ...efficiency are proportional to solar irradiance.•The ventilation PCM wall provides a satisfactory level of indoor thermal comfort.•Cascaded PCM can accelerate the thermal storage process during the initial phase.
Solar heating technology is increasingly recognized as a prominent option for clean building heating. However, challenges such as intermittent thermal energy supply and supply-demand mismatch hinder its widespread adoption. To address this issue, this paper introduces a novel coupled heating system that combines a solar air heater with a ventilation Phase Change Material (PCM) wall. A rural residential house in Tianjin was chosen as an experimental platform and comparative experiments was conducted to compare the advantages of the ventilation PCM wall with the conventional wall. Additionally, numerical simulations were utilized to address the non-uniform heat transfer in the direction of the Heat Transfer Fluid (HTF) flow by employing cascaded PCM. The experimental results demonstrated that the coupled heating system exhibited high thermal storage and release efficiency, significantly improving indoor thermal comfort. Under optimal operating conditions (air supply temperature: 35-45℃, air supply speed: 3-4m/s), the system achieved rapid thermal storage within 4 hours, reaching a maximum thermal storage efficiency of up to 87.6%. The test room maintained a nighttime temperature of 15.7°C, exhibiting temperatures 6.3-10°C higher than the control room. Numerical results revealed that the cascaded PCM enhanced the thermal storage rate, particularly at the first 2.8 hours of the thermal storage period, contributing to the overall efficiency and flexibility of the system. This research provides theoretical guidance for the optimal design and practical application of the ventilation PCM wall.
Radiant cooling panel systems are now popular solution for low carbon buildings, so has received great attention of researchers. Current development, however, is that radiant cooling panel systems ...have low cooling efficiency and cause high pressure on national energy supply during peak energy consumption periods. This study, therefore, has developed a novel composite phase change material (CPCM) coupled with a typical radiant cooling panel system, providing longer indoor comfort duration and less temperature fluctuation, while also alleviating the pressure on national energy supply during peak energy consumption. In this study, eutectic hydration salt of CaCl2·6H2O and mannitol have been combined with SiO2 to prepare a shape-stabilized CPCM. It has been placed in a test room to justify the impact of the new material. Experimental results have demonstrated some major properties of this material, namely, a melting point of 20.7 °C, a high latent heat value of 119.8 J/g, and a supercooling degree of 1.3 °C, as well as good stability and thermal reliability. Therefore, it can be used as a good solution for radiant cooling panel systems. Comparing the results with another test room with ordinary radiant cooling panels, the room with the new CPCM panel showed less indoor temperature fluctuation and 73 % longer indoor comfort duration. This work provides further development of using hydrated salts and CPCMs with different phase change temperatures in radiant cooling panel systems.
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