Thermal Comfort Of Occupants Research Articles

Gender difference regarding thermal comfort in Japanese residential building during free running mode

When experiencing a similar indoor environment, people's thermal comfort and sensation may differ, making it more difficult to create an appropriate thermal environment for each person who living in the same building or residence. In both shared and single-occupant constructed environments, personal or individual comfort models have been proven to more precisely forecast particular thermal comfort requirements than aggregated models, raising occupant tolerance and related energy advantages. Dealing with these issues can result in more balanced datasets and the expansion of personalized model applications into new environments. Therefore, from November 2015 to November 2017, a field measurement was carried out in a Japanese condominium. 53 selected houses with measured indoor air temperature and 21,502 thermal sensation votes (TSV) from thermal comfort survey for each participant during free running mode (FR) were gathered. The results showed that 98% of male and 96% of female voted within comfort band. The thermal comfort zone starts from 18 to 26 °C as 90% of the occupant voted 3, 4 and 5 for TSV (comfort zone). The mean comfort temperature for males was found to be significantly higher than females during summer at which males has 1.2 °C (June), 2.1 °C (July) and 2.2 °C (August) higher comfort temperatures. Clothing insulation for each gender proved to be an important role on how they choose their TSV and thus impacted the comfort temperature. The results can help the researchers in providing information when designing passive building system while contributing to improve the occupant behavior and thermal comfort.

Dynamic interdependence of comfortable thermal conditions and energy efficiency increase in a nursery school building for heating and cooling period

The paper studies the influence of building function and orientation, level of thermal insulation on energy efficiency and occupant thermal comfort dynamic interdependence. Energy state dynamic modelling of the typical preschool educational facility (Kyiv, Ukraine) was carried out with different levels of thermal comfort in each of the zones, taking into account occupants' activity, metabolism, clothing, etc. The research was conducted for the heating and cooling periods, taking into account the operational peculiarities of the building. Increasing the thermal resistance from the base version to the Swedish norms reduces energy consumption by 32% for the heating period, compared to the base version. The introduction of intermittent heating leads to a reduction of energy consumption by 14%, compared to the base version. Intermittent heating and ventilation and increased thermal protection to Swedish standards can reduce energy consumption by 42%. The investigation of comfort indicators revealed that during the transition period when the heating is turned off, electric heating of the premises is required to maintain the comfort conditions, which increases the heating energy consumption by 18%. Three different options for children's clothing in the summer period to avoid feeling cold were investigated.

The impact of personal environmental control on the performance of thermal systems: Building energy consumption, occupant thermal comfort, and productivity

Personal environmental control (PEC) is an energy-saving approach that empowers occupants with the freedom to regulate the indoor thermal environment, ensuring comfort while conserving energy by conditioning only the occupied space based on individual preferences. However, necessary information to support the practical application of PEC is still missing. Specifically, how the degree of freedom given to occupants changes the building energy efficiency, occupant thermal comfort, and productivity has not yet been investigated systematically. This research (i) investigates the application of PEC in existing thermal systems; (ii) examines the effects of PEC on the aforementioned three criteria for assessing the performance of thermal systems; and (iii) suggests an optimized thermal system incorporating the concept of PEC for a better performance of thermal systems. Primary data was collected by experimentation and observation among 21 participants under four different conditions in a field study in Hong Kong. Repeated measures ANOVA was applied in analyzing the thermal ratings, the energy consumption, and the productivity of participants. The outcome of this study shows that a higher PEC can only lead to marginal improvement of thermal comfort, but the building energy efficiency drops when they set the thermostat temperature themselves under a condition that they are given full control. No clear relationship is found in this study between the PEC and occupant productivity. As a pilot study to compare the performance of thermal systems under different PEC designs, this study contributes to the research field into a practical energy-efficient design of thermal systems by enhancing the occupants’ personal control of the thermal environment.

An IMU dataset for human thermal comfort activities identification: Experimental designs and applications

Thermal comfort of occupants is key feedback information for improving indoor environment and managing building energy use. Through analyzing inertial measurement units (IMU) data from wearable devices with machine learning, thermal comfort of occupants can be detected in a non- intrusive method. This paper proposed a dataset consisted of IMU data collected from 30 participants (14 males and 16 females, aged 23.23 ± 1.70 years, height 168.67 ± 8.02 cm, and weight 59.55 ± 10.96 kg) who wore two IMUs on their hands while performing 30 thermal comfort activities (10 cold-related, 10 hot-related, and 10 neutral activities) according to their personal habits.The database is divided into two parts: (1) Single activities data, which includes 4500 samples acquired from experiments where each participant was asked to perform 30 thermal comfort activities individually. (2) Continuous multi-activity data, which comprise 360 samples collected while participants performed a series of randomly assigned activities in a more natural and continuous manner. The combination of these two parts provides a comprehensive dataset for both the training and testing phases of machine learning models. By offering detailed labels, this database aims to serve as a foundation for research exploring machine learning applications in detecting occupant thermal comfort, ultimately contributing to improved indoor environments and more efficient building energy management.

A coupled analysis on human thermal comfort and the indoor non-uniform thermal environment through human exergy and CFD model

The importance of human thermal comfort evaluation lies of the development of healthy buildings as well as low-carbon buildings. In recent years, the applications of the second law of thermodynamics to thermal comfort offered a new perspective and this study, for the first time, an integrated human exergy model and the indoor CFD model for a coupled analysis is put forward, which supplements a critical link between human and building environment. In this paper, a predefined office model is investigated to improve the efficiency and thermal comfort of occupants. Based on the human exergy model, the parameters of metabolism, respiration, evaporation, convection, radiation, skin, and core heat storage terms are optimized. Additionally, the effects of gender, age, and clothing thermal resistance on the exergy model values are also separately explored. Finally, the optimized human exergy model is combined with computational fluid dynamics (CFD) to calculate, under different air supply conditions, the distribution of exergy consumption values in the predefined room model. The results show that the factors of gender, age, and thermal resistance of clothing have some influences on human exergy consumption, while the above factors do not have a significant enough influence on the model in the thermal comfort interval. Moreover, the combination of the human exergy model and CFD can offer some suitable air supply conditions for the development of indoor thermal comfort and work efficiency. This study presented a new tool that bridges human thermal sensation and indoor thermal environment.

Adaptive thermal comfort in the offices of three climates of North-East India

Buildings not only provide shelter to the occupants but also security, safety and comfort, as well as signifying economic and socio-cultural status. The high energy intensity of buildings has become a matter of concern worldwide in the context of climate change and global warming. Adaptive comfort principles and guidelines afford greater design opportunities for reduced energy intensity without compromising occupant thermal comfort and indoor environmental quality performance. However, thermal adaptation opportunities of office occupants in the North-Eastern part of India are rarely addressed by previous thermal comfort studies conducted in the Indian subcontinent. A yearlong questionnaire-based adaptive thermal comfort study with concurrent indoor environmental measurements was conducted in naturally ventilated office buildings located in three locations, i.e., Tezpur, Imphal and Shillong, representing the climatic zones of North-East India. A total of 2326 valid questionnaire responses were collected. ASHRAE Class-II field study protocols, seven-point thermal sensation and five-point preference scales were used to collect objective and subjective comfort assessments. It was found that the clothing insulation (clo) levels worn by occupants varied non-linearly with indoor temperatures. The estimated preferred temperatures for building occupants in Tezpur, Imphal and Shillong were 24 °C, 23.5 °C and 22 °C, respectively. Probit analysis of thermal sensation data indicated that the indoor temperature stimulus associated with a shift of one thermal sensation unit differed between the warm and cool side of the 7-point thermal sensation scale. Increasing indoor air velocity up to 0.8m/s shifted the upper threshold of discomfort to 32 °C. It was also found that 80% of office occupants were comfortable within the temperature range of 25 °C–30 °C. The adaptive comfort model derived from the current database shows lower sensitivity of subjects to outdoor temperature changes compared to existing International standards like ASHRAE Standard 55 or EN16798. The present study demonstrates the potential for low-energy, naturally ventilated office design strategies in similar climatic conditions in North-East India and other parts of the world. Above all, it enriches the worldwide thermal comfort database.

Coupling PCM wallboard utilization with night Ventilation: Energy efficiency and overheating risk in office buildings under climate change impact

The rising population and increasing thermal comfort expectations are expected to exacerbate the already high HVAC use in offices, which unavoidably places a strain on energy supply systems. Storing thermal energy by incorporating phase change materials (PCMs) is an effective method for improving the buildings’ energy efficiency. Understanding how a PCM wallboard responds to climate change (CC) is crucial to maintaining its viability and effectiveness in achieving energy efficiency and sustainability goals during a building’s lifetime. This study presents a methodological framework to assess the performance of a building utilizing PCM wallboards in terms of cooling/heating energy demand (and corresponding GWP and operation cost) and occupant thermal comfort considering the changing climate. As a case study, a hypothetical office building located in a cold semi-arid climate with high diurnal fluctuations was selected, and the performance of offices orienting in different directions was evaluated when PCM wallboards with different melting ranges were utilized. PCM19 with a melting range close to heating set point reduced the heating demand by 5.0–7.4% for 2020 and 7.8–9.2% for 2050; while PCM25 with a melting range close to cooling set point yielded cooling reductions of 1.9–4.3% for 2020 and 0.7–2.4% 2050. However, PCM19 and PCM25 were ineffective in cooling and heating, respectively, as they were not compatible with the chosen set points. Coupling PCM25 with night-ventilation (NV) significantly enhanced the cooling savings (NV: 23.2–25.7% for 2020; 13.9–15.7% for 2050; NV + PCM25: 29.4–30.6% for 2020; 16.6–17.5% for 2050); though, the effectiveness of NV was impaired with rising night temperatures due to CC. Hourly energy analysis demonstrated varying performance of wallboards based on the time of day, suggesting potential benefits in supply–demand dynamics and time-of-use energy pricing. In naturally-ventilated scenarios, PCM utilization was ineffective in reducing indoor overheating risk, even when night-ventilation was introduced. Results highlight that to effectively mitigate indoor overheating risk in office buildings, PCM wallboards should be coupled with air-conditioning and night-ventilation. Furthermore, for a comprehensive evaluation of the energy/GWP/cost saving potential of a PCM wallboard during a building's lifetime, not only the current but also the projected local climate should be considered given the shifting energy demand towards cooling due to climate change. Overall, this study provides valuable insights into effective PCM wallboard utilization and lays the groundwork for enhancing the resilience of built environments in the face of climate change challenges.

Study on adaptive thermal comfort model and behavioral adaptation in naturally ventilated residential buildings, Jimma Town, Ethiopia

Ethiopia boasts abundant untapped energy resources, yet access to electricity remains limited (30%), with frequent and prolonged outages. Research on occupant thermal comfort in Ethiopia remains limited as well. This study aimed to investigate comfort temperature, adaptive models, and behavioral adaptations in naturally ventilated residential buildings in Jimma town, Ethiopia. Our thermal comfort field survey involved 870 occupants from 104 houses, generating 5220 datasets between February and September 2020. Indoor environments were simultaneously measured using handheld digital instruments. Notably, the subjects lacked electrical fans, space heaters, or air-conditioners, relying instead on charcoal and plant residue for cooking and heating.Overall, only 56.2% of subjects felt comfortable within the thermal sensation scale's defined band, while 70.9% preferred either warmer or cooler environments, and 63.4% accepted their environments. The mean comfort temperature was 23.3˚C ± 3.44 based on all data. Our adaptive model predicted a 1.82 K perturbation in outdoor running mean temperature, resulting in a unit change in indoor comfort temperature. Significant occupant behavioral adaptation through operable environmental controls, clothing choices, and activity levels was observed. Our model is essential for building simulation in Ethiopia, emphasizing the need for an Ethiopian adaptive standard. Given the limited modern energy sources, understanding low-energy thermal comfort and human adaptation becomes vital for sustainable living conditions.

Performance assessment of capric acid-ethyl alcohol/expanded vermiculite phase change material incorporated cement mortar for thermal insulation in buildings

Due to global warming, the construction sector is looking for newer materials that can be incorporated into buildings to improve occupant thermal comfort while reducing energy consumption. The ability of construction materials to store thermal energy can be enhanced by incorporating phase change materials (PCM). A PCM is a substance that releases and absorbs energy at phase transition temperatures to offer useful heating or cooling. The addition of PCM in construction materials for thermal insulation has been proven beneficial by many researchers. The current study explores the feasibility of the incorporation of an organic PCM composite, which is developed by impregnating expanded vermiculite (EV) with capric acid (CA) using ethyl alcohol (EA) under vacuum conditions in cement mortar. Cement mortar mixes with EV, CA-EA/EV based PCMs, and PCMs with partially added nano silica and coir fiber combinations (PSC) were prepared by replacing fine aggregate in varied weights. Initially, the study on the primary characteristics of the developed PCM was introduced based on mechanical behavior, microstructure observations, and thermal effects. To estimate the field exposure capacity, PCM composite mortar boards were developed and tested for their physical and mechanical characteristics. Based on the findings of these tests, it was concluded that the presence of PCM improves the thermal characteristics of the mortar boards and the addition of nano silica and coir fiber enhances the physical and mechanical strength of the mortar boards. With regard to the characterization of the mortar, there was an increase in flexural strength by 8.06 % and a decrease in chloride diffusivity by 10.24 %, in water absorption by 17 %, the capillary water absorption coefficient by 8.56 % and the ultrasonic pulse velocity by 18.48 % relative to the control sample after addition of PSC into the mortar. Apart from the strength and durability studies, differential scanning calorimetry (DSC), energy-dispersive X-ray spectroscopy (EDS), thermogravimetry analysis (TGA) and scanning electron microscopy (SEM) tests were also carried out to characterize the thermal, chemical and morphological effects of the developed cementitious composite boards. As per the SEM and EDS test results, the fine aggregate replaced with 5 % of PCM in addition to nano silica and coir fiber (PSC-5 %) possesses better compatibility with the mortar by effectively penetrating through the pores. The DSC test results showed the melting and freezing point of PSC-5 % integrated mortar as 32.47 °C and 20.91 °C, respectively. A thermal conductivity value of 0.129 W/m·K also demonstrated the efficiency of PSC-5 % mortar board for maintaining better thermal comfort in buildings. The TGA assessment reported that the proposed PCM composite cement mortar board has excellent thermal durability.

An adaptive indoor temperature control approach simultaneously improving thermal comfort and task performance

Air conditioning and mechanical ventilation systems help maintain the thermal comfort (TC) of occupants in a workplace. Indoor temperature determination that only aims to improve TC causes difficulty in fulfilling the occupant's task performance (TP). It is crucial to find an appropriate indoor temperature range that simultaneously accommodates occupants' TC and TP. In this study, we propose an adaptive temperature control approach that simultaneously improves the occupant's TC and TP. The relationship among the dissatisfaction rate, predictive mean vote, and indoor temperature was established and quantified. An investigation in a human-robot collaboration scenario was conducted by using the proposed approach. The preferable temperature range under various combinations of TC and TP is recommended. The proposed algorithm successfully achieves a significant energy-saving of 9.98% within the desired temperature range. By reducing the preferred upper limit of the temperature range by 3 °C compared to current standards, the algorithm further reduces energy consumption. To validate the effectiveness of the proposed model, we developed empirical formulas that establish the relationship between thermal comfort, task performance, and temperature, enabling the identification of optimal indoor temperature settings. Additionally, our model effectively captures the complex trade-offs and complementary nature between thermal comfort and task performance with respect to indoor temperature. Overall, this approach offers a solution for setting indoor temperatures in the workplace.

Occupant thermal comfort and indoor environmental conditions in Mies van der Rohe’s S. R. Crown Hall

ABSTRACT There is little empirical data in the published literature on occupant thermal comfort in buildings from the Modern Movement in architecture. We present a field survey of occupant thermal comfort and indoor environmental conditions in Mies van der Rohe’s modern S. R. Crown Hall (1956) on the campus of Illinois Institute of Technology in Chicago, IL. Surveys were deployed to 557 student participants on four separate days, including two days in the cooling season and two days in the heating season, to assess their perceptions of thermal comfort throughout the space. Indoor air temperature, relative humidity and mean radiant temperature were measured concurrently in several locations throughout the space. Occupants reported high levels of dissatisfaction with comfort in the space (percent dissatisfied ranging 37%–54%), with somewhat counterintuitive results for this building type. Overcooling was apparent during warm weather and a combination of both over- and under-heating occurred during cold weather, contrary to what was expected in this building with a high thermal transmittance enclosure. There was also high spatial variability in comfort responses and measured indoor environmental conditions. Findings highlight the need to develop contextual approaches to meeting occupant comfort needs in this building while preserving architectural aesthetics/intent.

A systematic review on thermal environment and thermal comfort studies in Chinese residential buildings

Amid the backdrop of the energy crisis, thermal comfort is crucial to achieve energy savings. Residential buildings are characterized by a wide range of adaptive comfort opportunities. However, there has been a lack of systematic refinement and review of residential thermal comfort field studies in China to provide valuable recommendations for energy conservation. We systematically reviewed studies on thermal environment and thermal comfort in Chinese residential buildings published in peer-reviewed journals up to 2020. A total of 34 studies were deemed to have provided sufficient information on both the thermal environment and thermal comfort. We found that in winter, there were obvious differences between urban and rural dwellings in Severe Cold (SC) and Cold (C) zones, with regard to their indoor air temperature (urban: 19.8 ∼ 25.0 °C v.s. rural: 11.3 ∼ 17.8 °C) and neutral temperature (urban: 17.6 ∼ 25.1 °C v.s. rural: 11.9 ∼ 23.45 °C). While in summer, the indoor air temperature in urban dwellings were slightly lower than those in rural areas due to their prevalent use of air conditioner (urban: 26.1 ∼ 28.9 °C v.s. rural: 29.5 ∼ 34.9 °C). Indoor air temperature and neutral temperature varied considerably in different climate zones in winter. In SC zones, the indoor environment was overheated, which could lead to energy wastage and overheating discomfort for residents. Residents in Hot-Summer and Cold-Winter (HSCW) zone were the most tolerant to the variation of thermal environment (the median coefficient of MTS or TSV equation: SC: 0.18; C: 0.20; HSCW: 0.13; HSWW: 0.23).

Co-Simulation of Electric Power Distribution Systems and Buildings including Ultra-Fast HVAC Models and Optimal DER Control

Smart homes and virtual power plant (VPP) controls are growing fields of research with potential for improved electric power grid operation. A novel testbed for the co-simulation of electric power distribution systems and distributed energy resources (DERs) is employed to evaluate VPP scenarios and propose an optimization procedure. DERs of specific interest include behind-the-meter (BTM) solar photovoltaic (PV) systems as well as heating, ventilation, and air-conditioning (HVAC) systems. The simulation of HVAC systems is enabled by a machine learning procedure that produces ultra-fast models for electric power and indoor temperature of associated buildings that are up to 133 times faster than typical white-box implementations. Hundreds of these models, each with different properties, are randomly populated into a modified IEEE 123-bus test system to represent a typical U.S. community. Advanced VPP controls are developed based on the Consumer Technology Association (CTA) 2045 standard to leverage HVAC systems as generalized energy storage (GES) such that BTM solar PV is better utilized locally and occurrences of distribution system power peaks are reduced, while also maintaining occupant thermal comfort. An optimization is performed to determine the best control settings for targeted peak power and total daily energy increase minimization with example peak load reductions of 25+%.

A data-driven rolling optimization control approach for building energy systems that integrate virtual energy storage systems

The virtual energy storage system (VESS) is an innovative and cost-effective technique for coupling building envelope thermal storage and release abilities with the electric and heat power conversion characteristics of an air conditioner; this system provides building energy systems (BESs) with adjustable potentials similar to those of conventional battery energy storage systems (BESSs). However, the VESS is a dynamic system, and uncertainties in the outdoor temperature and solar irradiance are difficult to accurately predict, which impacts the quantification accuracy of VESSs; these characteristics challenge the BES control scheme economy and the thermal comfort of occupants. To solve this crucial issue, a data-driven rolling optimization (RO) control approach for a BES that integrates a VESS is proposed. First, a BES state space model integrating the VESS is created to reflect the VESS adjustable potential and dynamic characteristics. Based on the above model, while aiming at a small BES data sample size, a support vector machine (SVM) is combined with RO to correct the day-ahead quantification errors of the VESS adjustable potential and enhance the economical operation and thermal comfort of the BES that integrates the VESS in uncertain environments. Comparative simulations validate the effectiveness of this VESS modelling and data-driven RO control approach.

Cyber-Enabled Optimization of HVAC System Control in Open Space of Office Building

Thermal comfort is crucial to well-being and work productivity. Human thermal comfort is mainly controlled by HVAC (heating, ventilation, air conditioning) systems in buildings. However, the control metrics and measurements of thermal comfort in HVAC systems are often oversimplified using limited parameters and fail to accurately control thermal comfort in indoor climates. Traditional comfort models also lack the ability to adapt to individual demands and sensations. This research developed a data-driven thermal comfort model to improve the overall thermal comfort of occupants in office buildings. An architecture based on cyber-physical system (CPS) is used to achieve these goals. A building simulation model is built to simulate multiple occupants’ behaviors in an open-space office building. Results suggest that a hybrid model can accurately predict occupants’ thermal comfort level with reasonable computing time. In addition, this model can improve occupants’ thermal comfort by 43.41% to 69.93%, while energy consumption remains the same or is slightly reduced (1.01% to 3.63%). This strategy can potentially be implemented in real-world building automation systems with appropriate sensor placement in modern buildings.

A new generation of a ceiling air outlet using multi-objective optimization technique

The proper selection of ceiling air outlets represents an important step in efficient space comfort conditions. Square louver face ceiling diffusers are the most ceiling outlets used in the air conditioning applications. A small change in the geometry of this diffuser has well effect on the air flow distribution and occupant's thermal comfort inside the room. In the present work, with the aid of optimization methodology and computational fluid dynamics, different simulations and surrogate models are performed to obtain the optimal design of the diffuser by changing the variable parameters (blade and lip angles) of the standard diffuser. The optimization results of three surrogate models showed that the most suitable objective functions are jet velocity, terminal velocity and temperature difference, and the optimal diffuser shape is 64° blade angle and 2° lip angle. In addition, the reported results showed that the average terminal velocity of the optimal diffuser across the room (0.126–0.257 m/s) is higher than that provided by the conventional diffuser (0.107–0.228 m/s), and neither value exceeds ASHRAE standard conditions. Also, with a temperature difference of 1.25 °C for the optimal diffuser, the temperature distribution across the room shows a lower temperature distribution than that shown for the standard diffuser. Finally, the air with an optimal diffuser shape reaches comfort conditions faster than with conventional diffusers, which directly leads to minimising energy consumption.

Experimental investigation on indoor thermal environment improvement and energy-saving of electrochromic window under Singapore's tropical climate

This study aims at analyzing the thermal performance improvement of a gray tintable electrochromic window (EC window) under Singapore's tropical climate. Two climate chambers were experimentally studied, one with a double-glazed EC window and another with a single-glazing window, the most common in the considered region, as the reference. The indoor thermal environment and air conditioning energy consumption were compared respectively to investigate the thermal performance improvement of the EC window. The results, under the sunny outdoor weather condition, showed that the EC window could achieve an interior surface temperature reduction of 4.4 °C under the tinted state and 3.0 °C under the clear state, compared to the reference window. Moreover, the bleached EC window achieved up to 37% improvement in peak Predicted Mean Vote (PMV) over the reference window, while the fully tinted EC window achieved a 50% improvement in peak PMV. Finally, the EC window under the fully tinted state could achieve up to 19% energy savings compared to the reference window. Using the EC window under Singapore's tropical climate can improve the occupant thermal comfort during the daytime and reduce air conditioning energy consumption.

Windows of Opportunities: Orientation, Sizing and PV-Shading of the Glazed Area to Reduce Cooling Energy Demand in Sub-Sahara Africa

In hot climates, such as sub-Sahara Africa, window sizing and orientation pose challenges as they add, through solar insolation, to the building cooling energy demand and thus the cause of indoor overheating risk. This risk can be reduced through passive building-design-integrated measures, e.g., optimizing the window size, orientation and solar shading strategies. Through an IDA-ICE building performance simulation tool, the current study explores the impact of window size, optimization and building-integrated PV panels as shading strategies on cooling energy demands in three cities (Niamey, Nairobi and Harare) in sub-Sahara Africa. Results show that thermal comfort and cooling energy demand are sensitive to a window-to-wall ratio (WWR) > 70%, while the need for artificial lighting is negligible for a WWR > 50%, particularly in the north for cities in the Southern hemisphere and the south in the Northern hemisphere. A WWR > 70% in the east and west should be avoided unless shading devices are incorporated. Internal blinds perform better in improving occupant thermal comfort but increase artificial lighting while integrating PV panels, as external shading overhangs reduce cooling energy but also produce energy that can be utilized for building services, such as air conditioning. In this study, the results and implications of the optimization of window size, orientation and building-integrated shading and operation are discussed.

Influencing assessment of different heating modes on thermal comfort in electric vehicle cabin

Electric vehicle (EV) is more environmental-friendly than gasoline vehicle because the main power is not petrol. For the heating system, the waste heat generated by engines is recycled to heat the cabin of gasoline ones, while the EV need extra electric energy consumption for heating the cabin which decreases the driving range. Personal comfort system (PCS) has been reported that it is an alternative technique to improve occupant thermal comfort and indirectly save building heating energy. This study aims to investigate the occupants’ thermal sensation under four heating modes in the EV cabin in winter, including no heating, only PCS, only air conditioning, and both air conditioning and PCS. The field survey is conducted in a parked EV with 12 subjects. Three thermal comfort indexes (PMV, SET*, and operative temperature Top) are used and assessed for their applicability in the thermal environment of the EV. Results show that the thermal environment in the cabin is non-uniform and dynamic with the air conditioning mode, while the PCS mode just slightly affects the temperature differences inside. Meanwhile, the subjects’ thermal sensations cannot maintain neutral or warmer under the PCS mode only. The results of PMV are lower than the subjects’ actual thermal sensation votes (TSV), while the results of SET* and Top show significant linear relationships with the TSV for the correlation coefficients above 0.80. Compare to the air conditioning mode, the neutral SET* and neutral Top are decreased by 2.7 °C and 1.6 °C under the mode with PCS and air conditioning, respectively. The findings indicate that PCS not only has a positive effect on improving the cabin environment and occupant's thermal sensation but also has the potential to lower the setting temperature of air conditioner of EVs in winter.

Mutual Influence of External Wall Thermal Transmittance, Thermal Inertia, and Room Orientation on Office Thermal Comfort and Energy Demand

Upgrades in building energy efficiency codes led to differences between buildings designed according to outdated codes and those with most recent requirements. In this context, our study investigates the influence of external wall thermal transmittance, thermal inertia, and orientation on energy demand (heating, cooling) and occupant thermal comfort. Simulation models of an office building were designed, varying (i) the thermal transmittance values (0.20 and 0.60 W/(m2K)), (ii) the room orientation (four cardinal directions), and (iii) the wall thermal inertia (approximately 60 kJ/(m2K) for low and 340 kJ/(m2K) for high thermal inertia. The energy demand for heating and cooling seasons was calculated for Ljubljana using EnergyPlus 9.0.0 software. The reduction of the external wall thermal transmittance value from 0.6 W/(m2K) to 0.2 W/(m2K) contributes to significant energy savings (63% for heating and 37% for cooling). Thermal inertia showed considerable potential for energy savings, especially in the cooling season (20% and 13%, depending on the external wall insulation level). In addition, the orientation proved to have a notable impact on heating and cooling demand, however not as pronounced as thermal inertia (up to 7% total energy demand). Comparison of the thermal comfort results showed that when internal air temperatures are identically controlled in all the rooms (i.e., internal air temperature is not an influencing factor), the external wall thermal transmittance, thermal inertia, and room orientation show negligible influence on the average occupant thermal comfort. The simultaneous achievement of thermally comfortable conditions in the working environment and low energy use can only be achieved by simultaneously considering the U-value and thermal inertia.