Improve Indoor Thermal Comfort Research Articles

Fast-Growing Bio-Based Construction Materials as an Approach to Accelerate United Nations Sustainable Development Goals

The United Nations Sustainable Development Goals (UN SDGs) ensure future human well-being. However, they face challenges due to the pressing need to reduce carbon emissions, with nearly 40% originating from the construction sector. With the current global environmental and energy crisis, there is a pressing need to address building carbon emissions and prioritise investments in passive strategies for improving indoor thermal comfort. Exploring fast-growing bio-based materials like bamboo, straw, hemp, and flax directly addresses these concerns, fostering environmental sustainability. Material selection in construction is crucial for advancing the SDGs, for example, promoting sustainable cities and communities (SDG11) and responsible consumption and production (SDG12). This paper proposes a comparative analysis of conventional and bio-based construction materials, focusing on their production stages through life cycle analysis. Tools such as Building Emissions Accounting for Materials (BEAM) and the Methodology for Relative Assessment of Sustainability (MARS) enable a detailed comparison. The results highlight the benefits of bio-based materials in storing carbon more rapidly and their lower environmental impact compared to conventional alternatives. Moreover, bio-based materials contribute to indoor moisture regulation and a healthier indoor environment, underscoring their potential to accelerate progress towards the UN SDGs through informed material choices in design practices.

Design optimization of an assisted living facility to improve summer thermal comfort in warming climates

Assisted living facilities with optimal summer thermal comfort are necessary to ensure improved quality of life for the older individuals in warming climates. Older individuals are exposed to higher mortality risks during periods of excessive heat. This study aims to identify and optimize key design variables for a passive house certified assisted living facility in Belgium with high comfort expectations using EnergyPlus to improve indoor thermal comfort during extreme climates. The sensitivity analysis used the Standard Regression Coefficient method with Latin Hypercube Sampling for eighteen design variables under four categories: layout, envelope, operation, and system. The analysis identified flat roof and external floor insulation as the most influential parameters, whereas lighting gain and cooling setback temperature were the least influential parameters. Furthermore, optimizing the reference building with the most sensitive design variables using a genetic algorithm based on the NSGA-II method found ideal configurations that would ensure minimum thermal discomfort hours during extreme summers. The study findings provide an evidence-based approach for building engineers and designers for early-stage design of assisted living facilities that maintain optimal comfort in mixed humid climates of Europe.

Cooling collars incorporated with PCM packs and gels to improve indoor thermal comfort in healthy young females

Cooling collars incorporated with PCM packs and gels to improve indoor thermal comfort in healthy young females

The effect of internal blinds on thermal comfort: An experimental analysis in an office room with radiant panels

This study investigated the impact of two types of internal blinds on the indoor thermal environment of a highly glazed office room in Istanbul during summer. The research examined four configurations: (i) no blinds, (ii) roller blinds, (iii) layered roller blinds in night mode and (iv) layered roller blinds in day mode. Measurements of air velocity, average radiation temperature, air temperature and relative humidity were conducted to assess thermal comfort. The findings revealed that internal blinds significantly influence thermal comfort in radiantly cooled office spaces during summer. Without blinds, the indoor environment only met ISO 7730 comfort category C, with average predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) values of 0.6 and 12.5%, respectively. However, with internal blinds, comfort categories A and B were achieved, resulting in improved thermal comfort levels, with average PMV and PPD values ranging from 0.2 to 0.3 and 6% to 7.5%, respectively. Roller blinds, in particular, proved highly effective in enhancing thermal comfort and reducing mean radiant and indoor air temperatures in highly glazed radiant cooling offices. This demonstrated their energy-efficient potential for improving indoor thermal comfort.

Disodium hydrogen phosphate dodecahydrate/fumed silica composites with high latent heat and suitable phase change temperature for use in building roof

Introducing phase change materials (PCM) with suitable phase change temperature and large latent heat into the application of building roofs is conducive to building energy efficiency, which can reduce indoor temperature fluctuation and improve thermal comfort. In this paper, the optimized disodium hydrogen phosphate dodecahydrate (DHPD) was combined with fumed silica (FS) to prepare a new type of DHPD/FS composites, with a phase change temperature of 41.5 °C, a latent heat of change of 103.46 J/g, and an optimal content of 22.5 % of FS. The leakage experiments proved that there was no leakage of the PCM at this ratio, and after 200 cycles of thermal cycling, the phase change temperature of DHPD/FS composites basically remains unchanged, with good thermal reliability, but the addition of FS will make the material decrease in thermal conductivity, and the thermal conductivity is reduced to 0.19 W·m−1·K−1. Furthermore, the study investigated the application of the encapsulated DHPD/FS composites as a phase change board on the roof. The results indicated that the inclusion of the phase change board improved indoor thermal comfort and demonstrated good thermal performance. When the phase change board was positioned in the top layer, the enhancement of thermal comfort was most optimal.

Effectiveness of enhanced roof ventilation unit (ERU) based on venturi cap in different wind environments and new evaluation models: A numerical study

Reasonable building ventilation design can effectively improve indoor thermal comfort and reduce energy consumption. Therefore, an enhanced roof ventilation unit (ERU) was developed for this study, and its performance and influence law under various wind speeds and directions were explored through numerical simulation. Additionally, a new evaluation method for ERU was proposed through data fitting, and applicability was verified for different climate zones in China. The results showed that: (1) With a maximum difference of 3.11 °C, the ERU performed best in the N direction and poorest in the SW direction for indoor temperature. Furthermore, the impact of wind directions was more evident than wind speeds. (2) The wind speed affected the volume flow rate significantly in the NE direction (7.77 m3/s) and insignificantly not in the SE direction (0.32 m3/s). Nevertheless, the performance was the opposite in the NE and SE directions when the wind speed increased from 0.5 m/s (3) The air age performed best in the NE and worst in the SE directions. As wind speeds surpassed 2.0 m/s, the air age variation steadily stabilized in various wind directions. (4) The fitted equation for indoor temperature has applicability in typical cities in five climate zones, and the fitted equation for volume flow rate is applicable in four climate zones except the hot summer and warm winter zone. The study results can provide references for the ERU to improve indoor thermal ventilation, contributing to sustainable building energy efficiency.

Thermal Impact Investigation of Shaded Opaque Walls in Bangkok

The effectiveness of overhang shading devices in mitigating solar radiation on opaque walls is crucial for passive building design in tropical regions. However, opaque walls commonly are side-lined in shading design due to a preoccupation with insulation properties, appearance, and aesthetics. Unprotected walls exposed to solar radiation maximize heat gain, while shaded walls decrease external heat gain and indoor temperature, resulting in improved indoor thermal comfort and well-being. This research employs EnergyPlus and SPSS to investigate the optimal design of overhang shading devices for opaque walls in Bangkok, Thailand. The investigation is divided into two phases: (1) determination of the optimal depth-to-space ratio of overhang devices based on a parametric study of 12 overhang configurations; (2) an evaluation of the ratio in reducing solar radiation. The findings demonstrate a relationship between the device depths and the wall solar radiation and indoor temperature. The optimum depth-to-space ratio is suggested as 1:1.15, which can lower the annual average indoor temperature by 3.53% (1.18°C) compared to the benchmark design. Deeper shading device depths than the optimum depth-to-space ratio can be applied, with a slight improvement in protective performance (and commensurately increased costs). This research underscores the importance of overhang shading devices as a performance-improving strategy for buildings in the tropical climate of Thailand.

An Investigation of the Energy-Saving Optimization Design of the Enclosure Structure in High-Altitude Office Buildings

Concerning the double carbon national strategy, the energy-saving renovation of old buildings has become one of the most important tasks of energy conservation and emission reduction in construction in China. There are many problems, such as high energy consumption, thermal environment, and poor thermal comfort. Taking Lhasa as an example, this study adopts field research, questionnaire interviews, on-site measurements, numerical simulations, and other methods to propose suitable energy-saving potential excavation points and thermal optimization strategies for office building envelopes in Lhasa through software simulation. Additionally, typical office buildings are selected to carry out the energy-saving renovation of envelopes with the goal of improving indoor thermal comfort to validate the feasibility of the energy-saving renovation strategies. The results show the following: (1) The measured and predicted thermal neutral temperatures of the office population in Lhasa are 16.5 °C and 18.9 °C, respectively. The 90% acceptable temperature range is from 16.10 °C to 21.77 °C, and the occupants of the office buildings in Lhasa have a higher tolerance for cold than predicted. (2) The passive measures adapted to Lhasa are prioritized in the order of passive solar energy, high-heat-capacity materials, and nighttime ventilation. (3) Through the optimization of the enclosure structure of existing office buildings, the improvement of the heat storage capacity of the outer enclosure structure, and the increase in the window opening area to increase natural ventilation, the indoor thermal comfort of the renovated buildings is effectively improved.

A simulation study on the heating characteristics of residential buildings using intermittent heating in Hot-Summer/Cold-Winter areas of China

Radiant air conditioning system is an important heating method with better thermal comfort, less noise and greater energy-saving potential. However, different intermittent heating modes may significantly impact both the heating efficiency and indoor thermal comfort, which has been neglected in existing studies. Therefore, to obtain optimal intermittent heating modes for achieving higher energy efficiency and better indoor thermal comfort for the residential buildings in Hot Summer and Cold Winter areas, a TRNSYS model of the radiant air conditioning system was developed and validated. The indoor thermal comfort and energy consumption characteristics during the coldest day and entire heating season were simulated and analyzed based on four different intermittent heating modes. The results demonstrated that the supply water temperature of the air source heat pump unit and the radiant terminals stabilized at the set temperature in about 1 h during the start-up stage, and the indoor air temperature stabilized at 24.0 °C after 7.5 h during the shutdown stage. The proportion of time that meets first-level thermal comfort under the four intermittent heating modes was above 90.1% and even higher at over 96.1% when considering the sleeping period. Compared to the continuous heating mode, the four intermittent heating modes saved 22.3%, 25.8%, 40.4% and 48.4% of energy. Overall, the preferred intermittent heating mode for residential buildings with the radiant air conditioning system in Hot Summer and Cold Winter areas was identified as switching on from 7:00 to 15:00 and 19:00 to 3:00, while switching off from 15:00 to 19:00 and 3:00 to 7:00. This model not only considered the immediate benefits of improved indoor thermal comfort and energy efficiency, but also showed great advantages in developing sustainable construction.

Balancing thermal comfort and energy efficiency in high-rise public housing in Hong Kong: Insights and recommendations

As global warming intensifies, passive design for public housing in hot and humid climates has become a pressing issue. Achieving a balance between thermal comfort and energy conservation is particularly challenging in low-income public rental housing, where residents may endure extended periods of uncomfortable and unhealthy thermal conditions without resorting to air conditioning. In this study, EnergyPlus simulations are employed in combination with a novel thermal-comfort-based HVAC control approach to evaluate the performance of 14 Passive Cooling Strategies (PCS) in optimizing thermal comfort and energy conservation in high-rise public apartments of various sizes and orientations in Hong Kong, particularly under extreme summer conditions. The results reveal that, during extreme summer weather, the implementation of PCS primarily enhances thermal comfort conditions in May and September, while facing challenges in creating comfortable conditions during peak summer months. Most PCSs struggle to improve indoor comfort while simultaneously reducing energy consumption, with two exceptions: 1) Cross-ventilation-based designs enhance thermal comfort without increasing cooling energy consumption. 2) With energy-saving HVAC and opening control behavior, coupled with the use of fans for improving indoor thermal comfort, all PCSs can achieve a simultaneous improvement in thermal comfort and a reduction in cooling energy consumption. This results in a reduction in summer air-conditioning operation time of up to 50% and a decrease in air-conditioning cooling energy consumption of up to 30%. Regarding the impact of building size and orientation: 1) Small apartments show a heightened sensitivity to PCSs, particularly concerning indoor temperature, thermal comfort, and cooling energy consumption. 2) The influence of building orientation on cooling and comfort time in any PCS varies by less than 10% of its average and is even lower in PCSs with lower internal heat gain.

ADOBE BRICKS TO HOLLOW SANDCRETE BLOCK WALLING IN TROPICAL BUILDING CONSTRUCTION: MATERIAL IMPACT ON SUSTAINABLE INDOOR THERMAL COMFORT ATTAINMENT

Introduction: Tropical climate is characterized by high temperature, the consequence of which induces indoor thermal discomfort. This is attributed to high solar gains through various elements of the building envelope, including windows, walls, and roof among others. However, in an attempt to optimize indoor thermal comfort with minimal or no recourse to mechanical installations, this study explores the roles of the walling fabrics by comparing varying thermo-physical properties of two identified masonry units in the study area of Ogbomoso, Nigeria (adobe bricks and hollow sandcrete blocks), with a view to identifying a more thermally comfortable and sustainable material option. The methodology involves virtual models of two similar residential buildings each composed of either adobe bricks or sandcrete blocks, as masonry units. These models were subjected to energy performance simulation analyses using DesignBuilder software, over a 12‑month cycle period, to experience year-round differential thermal conditions. Through the observed comparative annual heat loads as experienced in the models, the results show improved indoor thermal comfort in the brick building (i.e., 7119.54 KWh), with heat loads being 11% lower than that of the sandcrete building (i.e., 8875.65 KWh) due to the brick walling fabric. This may be associated with the brick’s lower thermal conductivity (U-Value) of 1.798 W/m2-K, compared with the sandcrete blocks’ value of 1.999 W/m2-K. Results: In general, adobe bricks as a walling unit exhibit more thermal resistance against the harsh outdoor weather conditions than sandcrete blocks. The study is part of an ongoing effort towards reviving this partially neglected low impact material — adobe brick — with a view to attaining sustainable indoor thermal comfort as well as protect the environment in the study area.

Moisture buffer value for hygroscopic materials with different thickness

Moisture buffering is the capacity of hygroscopic building materials or adsorbents to mitigate the humidity fluctuations in the indoor environment through the adsorption/desorption phenomenon. NORDTEST proposed the moisture buffer value to quantitively characterize the moisture buffering capacity of porous materials. Materials with high moisture buffer values have a higher ability to passively control indoor humidity conditions and thus reduce building energy consumption and improve indoor thermal comfort. However, the ideal moisture buffer value theory is based on the assumption that the thickness of the studied materials should exceed the penetration depth of that material. This assumption significantly limits the application of moisture buffer value theory to thin-layer materials, such as textiles, desiccant coating, wallpaper, wood wall panels, etc, which represent a large proportion of moisture buffering in the built environment. In this study, we developed a new numerical model to calculate moisture buffer values for hygroscopic materials with different thicknesses. Experimental measurements were also carried out to validate the solutions. The moisture buffer value of a new kind of desiccant (metal-organic frameworks) under different thicknesses were measured by climatic chamber tests. Simulated results showed agreement with both the measurements and theory. The results indicate that the new moisture buffer value model can be used to find the optimal thickness of desiccant coating or hygroscopic materials for autonomous indoor humidity control.

Green roofs and thermal comfort: a comparative study of soil layers’ seasonal thermal performance integrated with ventilation in hot climate

ABSTRACT Green roofs’ (GR) positive impact on indoor thermal conditions in hot areas may have possible negative impacts during hot and cold weather. Most previous studies have focused on GR’s positive effects as a standalone strategy without mitigating these side effects of GR application. This study contributes to a more comprehensive understanding of the impact of GR and how to mitigate the negative aspects by integrating it with other passive techniques (natural ventilation and thermal insulation). Therefore, this study experimentally compares the seasonal impact of various soil layer configurations, integrated with natural ventilation, on improving Indoor Thermal Comfort (ITC) throughout the day in summer and winter. Field experiments were conducted using two identical validated test boxes. The results revealed that clay soil reduced Indoor Air Temperature (IAT) during the daytime in summer by up to 4.7 and 4°C for low and high soil thickness, respectively. Increasing clay soil thickness improved average IAT during the daytime in summer and winter by up to 6.49% and 2.61%, respectively. Additionally, adding thermal insulation is preferred in winter, while uninsulated soil had a slight positive effect on IAT and Indoor Relative Humidity (IRH) in summer. The use of natural ventilation at night and closed-ventilated systems during the daytime in summer and winter is recommended. Clay soil could save cooling and heating energy by up to 34.8% and 12.18%, respectively. These findings might inform designers by adjusting different GR soil parameters and the importance of natural ventilation in improving multi-seasonal thermal and energy performance.

Evaluating energy generation of a building-integrated organic photovoltaic vertical façade: A case study of Latin America's pioneering installation

Building-integrated photovoltaics play a key role in the reduction of greenhouse gases emission towards sustainability in the building and construction sector. Organic solar technology holds several advantages such as lightweight, flexibility and semitransparency, suiting well for this type of application. When integrated into windows and facades, it provides a dual benefit: it acts as a solar radiation barrier, improving indoor thermal comfort, while also generating off-grid power. Besides that, organic devices are known to be more efficient than traditional photovoltaics based in silicon in diffuse and low light conditions. Nevertheless, only a few studies have been conducted in the area employing large-area commercial modules, in real operational conditions and for a long-term period. This work has the purpose of reducing this gap and shine a light on this debate bringing an analysis based on real data of a set of organic panels laminated in glass in a vertical pioneer installation in Latin America. For this, several linear regression models were tested to predict the energy generation from meteorological data and solar position throughout four years of operation, and the best models developed achieved 0.76 and 0.81 values for R2 with validation data, respectively for simple and multiple regressions. A visual analysis showed that the OPV system produced more energy in winter due to lower solar altitude, despite lower global radiation levels. The most significant variables in the models were the global solar radiation and the solar altitude. The use of glass lamination and vertical orientation likely preserved the performance of the panels, keeping energy generation consistent over four years, akin to the first year.

Handling fault detection and diagnosis in incomplete sensor measurements for BAS based HVAC system

Due to the development of sensor networks, Building Automation System (BAS) based heating, ventilation, and air conditioning (HVAC) has gradually replaced traditional HVAC to improve indoor thermal comfort and decrease energy consumption. Because of inevitable faults in sensors or networks, the real-time sensor data may be incomplete with corrupted, lost or undetected missing values. Therefore, Improved Fireworks Algorithm (IFWA)-Long Short-Term Memory (LSTM) is proposed to recover incomplete measurements in BAS HVAC sensors. Because sensor data loss mostly results from incorrect control commands from the BAS system or sensor damage, there is a high probability of concurrent sensor fault. Therefore, Independent Component Analysis (ICA)-K-Nearest Neighbors (KNN) is proposed to monitor the sensor's healthy state under the measurements recovered. This paper discusses the possible causes of incomplete measurement in BAS HVAC sensors and simulates the distribution by experiment. The experiment analyzes the data recovery capability of IFWA-LSTM for different types of missing sensor data in different sensor measurement loss scenarios. The result shows that compared to the comparative methods, IFWA-LSTM achieves a 6.45 %–86.92 % improvement in recovery accuracy and a 0.0041 to 0.6340 improvement in correlation coefficients. Subsequently, it discusses the fault diagnosis rate of ICA-KNN under full measurements and incomplete measurement recovered by IFWA-LSTM. Overall, ICA-KNN achieves an average fault diagnosis rate of 99.86 % and an average fault alarm rate of 0 % under full measurement. When applied to incomplete measurement recovered by IFWA-LSTM, ICA-KNN exhibits an average fault diagnosis rate of 92.18 % and an average fault alarm rate of 1.22 %.

Identifying bioclimatic techniques for sustainable low-rise high-density residential units: Comparative analysis on the ventilation performance of vernacular dwellings in China

Vernacular dwellings equipped with bioclimatic techniques, used to form low-rise high-density communities in most Asian regions, are of great value for the development of modern sustainable residential units. Natural ventilation is a major concern mainly because of its climate-related characteristics of improving indoor thermal comfort at extremely low ecological costs. Therefore, this study applies a comparative analysis coupled with field investigations and numerical simulations to the ventilation technologies of vernacular dwellings in different areas of China. Geometric prototypes of typical vernacular dwellings in six climate zones were generated based on field measurements. Computational Fluid Dynamic (CFD) simulations were conducted in OpenFOAM with the Reynolds Averaged Navier-Stokes (RANS) modeling approach and the RNG k-ε turbulence model. A correlation analysis of the building elements and climate factors was also performed to determine the relevant parameters affecting ventilation performance. The results revealed different emphases and verified strategies for wind environment regulation based on different local climates. Six physical parameters, namely wind projection angle, orientation, wind inclination angle, window-to-wall ratio, top-to-bottom ratio, and height-to-width ratio of the atrium, are considered to be closely related to ventilation efficiency. The findings from the current research provide quantitative evidence of the effectiveness of natural ventilation technologies of vernacular dwellings and contribute to comprehensive knowledge for designing sustainable low-rise high-density residential units with optimum ventilation functions.

Development of personalized predicted mean vote based on a real-time clothing insulation recognition system

As people’s standards for indoor environmental quality and life are getting higher and higher, many studies try to find ways to improve indoor thermal comfort through experiments and simulations. Predictive mean voting (PMV) is a widely used indicator, but personal factors used to calculate PMV are not easy to monitor. This study aimed to develop a real-time clothing insulation identification (R-CLO) system to estimate personal PMV. This study is mainly divided into three stages. The first stage is to issue questionnaires to obtain the value of the personal clothing level and analyze the correlation between different external temperatures and the clothing insulation (Icl). The second stage is to build a real-time clothing recognition model and analyze its recognition accuracy. The third stage is to use ANN to establish a clothing insulation transition model and use the outdoor temperature and the results of clothing recognition to estimate Icl. This research also established an experimental environment to verify the system’s feasibility. The results show that the system has more than 80% accuracy rate for clothes recognition, and the accuracy rate of short-sleeved tops, shorts, trousers, and skirts is more than 90%. Moreover, most of the Icl estimated by the ANN have less than 0.1 differences from the value reported by occupants. In the future, this system can also combine occupant behavior recognition to strengthen PMV prediction results to achieve more precise, comfortable air-conditioning control.

Indoor thermal comfort comparison between passive solar house with active solar heating and without active solar heating in Tibetan

Passive solar house technology has been spread for many farmers and herdsmen to improve the indoor thermal environment in Tibetan. However, due to lackage of fuels and arid cold in winter, dry cow dung and coal are popularly fired in stove in passive solar houses, which leads to indoor air pollution and poor indoor comfort. For improving indoor thermal comfort of Tibetan, an active solar heating system which consists of 7 sets of tandem solar water heaters with 30 glass evacuated solar tubes, low temperature floor heating and circulation controller was developed and tested for a common house without insulation in Gan-nan Tibetan area. Its indoor environment was compared and evaluated by PMV-PPD and LPD method to that of the same passive solar house heated by coal stove. On sunny, cloudy and snow days, the active solar heating system provided 113.1, 46.4 and 26.3 kWh of heat to room. The indoor humidity and wind speed of the experimental building were better. The indoor temperatures were 17.2-20.7, 14.9-20.5 and 11.0-14.8°C, while the compared building were 8.9-14.8, 10.1-12.1 and 7.2-10.5°C. The maximum temperature difference between head and ankle were 1.7, 1.6 and 0.9℃, and the compared building were 4, 4 and 4.7℃. The PMV-PPD on sunny day were class I and II; on cloudy day were class I, II and III; on snow day was class III. On sunny and cloudy days, the LPD were class I, on snow day was class I, II and III. The PMV-PPD and LPD for typical days of the compared building were class III. During the 179 days, the mean indoor temperature exceeded 14 ℃ for 81 days, the solar active heating system provided 12471 kWh of heat to room. The CO2 emission reduction was 12905 kg. The system's dynamic payback period were 2.57 years.

The Review of the Application of the Heat Pipe on Enhancing Performance of the Air-Conditioning System in Buildings

An air-conditioning system (ACS), which consumes large amounts of high-grade energy, is essential for maintaining the indoor thermal environment of modern buildings. However, an ACS consumes almost half of the total energy of the building. Therefore, it is necessary to reduce the energy consumption of the ACS to promote energy conservation and emission reduction in the building sector. In fact, there is an abundance of waste heat and low-grade energies with the potential to be utilized in ACS in nature, but many of them are not utilized efficiently or cannot be utilized at all due to the low efficiency of thermal energy conversion. Known as a passive thermal transfer device, the application of a heat pipe (HP) in the ACS has shown explosive growth in recent years. HPs have been demonstrated to be an effective method for reducing building cooling and heating demands and energy consumption in ACS with experimental and simulation methods. This paper summarizes the different HP types applied in the ACS and provides brief insight into the performance enhancement of the ACS integrated with HP. Four types of HPs, namely tubular HP (THP), loop HP (LHP), pulsating HP (PHP) and flat HP (FHP), are presented. Their working principles and scope of applications are reviewed. Then, HPs used in natural cooling system, split air conditioner (SAC), centralized ACS (CACS) and cooling terminal devices are comprehensively reviewed. Finally, the heat transfer characteristics and energy savings of the above systems are critically analyzed. The results show that the performance of the HP is greatly affected by its own structure, working fluid and external environmental conditions. The energy saving of ACS coupled with HP is 3–40.9%. The payback period of this system ranges from 1.9–10 years. It demonstrates that the HP plays a significant role in reducing ACS energy consumption and improving indoor thermal comfort.

Thermal performance research on a novel coupled heating system combined solar air heater with ventilation PCM wall

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: 3–4 m/s), the system achieved rapid thermal storage within 4 h, 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 h 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.