Typical Office Research Articles

Novel energy efficient integration of chimney ventilation, liquid desiccant dehumidification, and evaporative cooling for humid climates

The chimney effect for driving passively building ventilation is effective in dry and moderate climates to introduce cool fresh air into the space. However, its application in hot humid climates is limited due to the high energy demands associated with dehumidifying and cooling outdoor air. Thus, a novel energy-efficient assistive system is proposed integrating a chimney-driven ventilation with liquid desiccant dehumidification membrane loop and indirect evaporative cooling. This system leverages natural buoyancy to supply ventilation airflow and uses potassium formate loops through semi-permeable membranes for effective dehumidification. The objective is to dehumidify and cool the induced outdoor air to the room conditions of 24°C and relative humidity between 40% and 60% at minimal energy consumption. Mathematical models were developed to simulate the heat and mass transfer processes in the air and liquid desiccant flows within the system components. The system was sized, and its operation was optimized using an advanced machine learning-genetic algorithm model for a typical office space in Beirut. During the summer, the chimney air flowrate ranged from 45L/s to 48L/s, and it was delivered at the target room conditions. The system saved around 350kWh of electrical energy during the summer months due to elimination of the need to treat ventilation air by room cooling system. This was equivalent to the total energy required to handle the ventilation load during the summer season and resulted in a saving of $50/month in the case study.

Life cycle carbon emission calculation model of energy system in public buildings: A case study in Shanghai

Energy consumption and carbon emissions (CE) in the building sector have grown in importance in relation to global climate change for China's sustainable development. Relatively few research have addressed the embodied CE, despite the fact that many have examined the operational CE from energy system operational use. In order to determine the CE of the energy production, transportation, construction, operation, and recycling stages, we therefore put up an integrated model. An inventory analysis of the energy system's life cycle CE, a scenario forecast of various combinations of building energy system equipment, and a case study of the building energy system of a typical office building in Shanghai's service industry. According to the results, the embodied CE emits 38.01 % of its energy, and the operational CE emits 61.99 %. However, we should not underestimate the significance of the impact of the embodied CE. Among all projection scenarios, the suggested CE share is highest (18.40 %) when the system combination of air-source heat pump units, LED lights, and ground-source heat pump units is implemented. In the end, based on the structural analysis of the embodied CE, low-carbon growth strategies and policy recommendations for Shanghai's service sector will be made.

Thermal insulation provided by chairs with various clothing ensembles

The thermal insulation provided by chairs significantly influences human thermal comfort. On the one hand, it modifies the heat exchange mechanism at the contact points between the body and the chair surface. On the other hand, an increase in local thermal insulation can exacerbate differences in thermal insulation across various areas of the body, impacting overall comfort. However, the thermal insulation data for chairs are decades old and thus need to be updated to reflect modern designs and materials. Six typical office chairs were tested using a thermal manikin dressed in five typical clothing ensembles (ranging from summer to winter). The effective thermal insulation of the chairs varied between 0.04 and 0.14 clo when tested in the nude. The added values ranged from 0.04 to 0.30 clo when tested with different clothing ensembles. Higher clothing levels correspond to higher added chair thermal insulation. Therefore, a simple weighing method was developed to adjust the seasonal coefficient of the mean chair insulation value (0.75 in summer, 1.0 in transition, and 1.25 in winter). Furthermore, a simple model was established for calculating the overall clothing level for a seated person. The model was validated using data measured in this experiment and other external sources, with a minimum prediction mean error of 1.4 %. This study provides a reference for accurately acquiring the thermal insulation value of chairs for a seated person in thermal comfort studies.

A Framework for Adaptive Façade Optimization Design Based on Building Envelope Performance Characteristics

The adaptive façades serve as the interface between the indoor and outdoor energy of the building. Adaptive façade optimization design can improve daylighting performance, the thermal environment, view performance, and solar energy utilization efficiency, thus reducing building energy consumption. However, traditional design frameworks often neglect the influence of building envelope performance characteristics on adaptive façade optimization design. This paper aims to reveal the potential functional relationship between building façade performance characteristics and adaptive façade design. It proposes an adaptive façade optimization design framework based on building envelope performance characteristics. The method was then applied to a typical office building in northern China. This framework utilizes a K-means clustering algorithm to analyze building envelope performance characteristics, establish a link to adaptive façade design, and use the optimization algorithm and machine learning to make multi-objective optimization predictions. Finally, Pearson’s correlation analysis and visual decision tools were employed to explore the optimization potential of adaptive façades concerning indoor daylighting performance, view performance, and solar energy utilization. The results showed that the optimized adaptive façade design enhances useful daylight illuminance (UDI) by 0.52%, quality of view (QV) by 5.36%, and beneficial solar radiation energy (BSR) by 14.93% compared to traditional blinds. In addition, each office unit can generate 309.94 KWh of photovoltaic power per year using photovoltaic shading systems. The framework provides new perspectives and methods for adaptive façade optimization design, which helps to achieve multiple performance objectives for buildings.

Advanced co-simulation framework for assessing the interplay between occupant behaviors and demand flexibility in commercial buildings

With buildings contributing significantly to electricity usage, enabling demand flexibility becomes a challenge, especially when accounting for occupant comfort. This study introduces an innovative co-simulation framework integrating multiple models: heating, ventilation, and air conditioning (HVAC) system, building zone load, indoor airflow, supervisory control, and occupant comfort and behavior. Uniquely, this framework allows for a comprehensive and dynamic analysis of building systems and occupant interactions in demand response events. Using this framework, we conducted a case study using a typical small office building model. Specifically, we focused on three areas: (1) the impact of indoor airflow modeling on energy use, occupant comfort, and behaviors forecasting, (2) the impact of occupant behaviors on demand flexibility, and (3) occupant comfort and behaviors under demand response events. Key performance indicators such as energy use, flexibility factor, durations of occupant discomfort and occupant behaviors were analyzed. Our findings indicated variations in energy usage and occupant comfort within demand flexibility events, marked by uncertainty boundaries, with variability in demand shedding up to 57.9%. We concluded that this framework is suitable for analyzing typical commercial buildings and their HVAC systems in terms of demand flexibility potential under the impact of occupant behaviors.

Influence of materials and surface parameters on the moisture buffering in office buildings: A sensitivity analysis of China

The management of indoor humidity through equipment consumes massive energy, leading to the growing interest in passive regulation of indoor humidity via moisture buffering. Numerous factors may impact the performance of interior finishing material during moisture regulation, thus identifying the dominant parameters is critical for moisture buffering effect optimization. This study analyzes the influence of five moisture and surface parameters, which are directly related to the moisture transfer of the interior finishing layer, on the thermal loads in a typical office building under typical climates in China. The analysis employs scatter plots and sensitivity indices based on Sobol's method. The results show that the material thickness plays a decisive role under different climates. The importance of sorption isotherm varies with climates and load types. The vapor diffusion resistance factor of the material only affects the latent heat loads, while the effect of the surface vapor transfer resistance is negligible. Finally, this study puts forward suggestions for interior finishing material selection to achieve low-load performance based on the characteristics of parameter combinations.

Energy-saving potential benchmarking method of office buildings based on probabilistic forecast

Building energy consumption represents a substantial portion of China's total energy usage profile. Conducting a quantitative assessment of the energy-saving potential in buildings is crucial, as it aids in estimating the investment risk and payback period for energy-efficient projects. This evaluation also informs the development and formulation of policies promoting building retrofits and energy conservation. However, this field's present state of research exhibits a significant gap. This study takes 8 typical office buildings as case objects and conducts relevant research on quantitative evaluation of energy-saving potential. On the basis of quantile regression, three corresponding probabilistic forecasting models for building energy consumption are established by combining the classic time series prediction algorithm Long Short-Term Memory (LSTM) in data-driven methods, Gradient Boosting Decision Tree (GBDT) in known building energy benchmarking, and a relatively simple linear model. The evaluation results demonstrate that the LSTM-QR model can serve effectively as a probabilistic forecasting model for estimating building energy-saving potential. Based on the LSTM-QR model results, a quantitative evaluation method for building energy-saving potential benchmarking is proposed, utilizing linearized Cumulative Distribution Function (CDF) curves. This method can quantitatively assess the energy-saving potential of the studied buildings. By analyzing and comparing these buildings' hourly energy consumption data over the past three years, it is evident that the quantitative scoring results from this method can provide directional guidance for building renovation projects to enhance energy efficiency.

System Optimization and Operating Strategy of Single-Stage Air Source Heat Pump with Thermal Storage to Reduce Wind Power Curtailment

Wind power generation has increased in China to achieve the target of decreasing CO2 emissions by 2050, but there are high levels of wind curtailment due to the mismatch between electricity supply and demand. This paper proposes a single-stage air source heat pump coupled with thermal storage for building heating purposes. The main objective is to find the proper system designs and operating strategy, which can help to avoid peak demand periods while obtaining minimized running costs and reduced wind energy curtailment. Dynamic simulations were performed using TRNSYS to investigate its use in a typical office building based on an actual electricity tariff, wind power, and meteorological data. The proper system designs, including the tank size and thermal storage temperature, were determined to maximize the system’s performance. It was found that a proper combination of the two parameters exists for a specific application. Further, results showed that the use of auxiliary electric heating is necessary for single-stage air source heat pumps to participate in a wind curtailment reduction. The operating strategy of the system was also studied. Results indicate that by implementing a proper operating strategy, non-renewable power consumption can be reduced by 11% for the studied building, with a total wind power utilization of 3348 kWh during the heating season while still satisfying the heating demands of users. These findings can contribute to the green and low-carbon development of the building industry and further enhance the grid’s accommodation capacity for renewable energy sources.

Research on geometry optimization of park office buildings with the goal of zero energy

At the conceptual design stage, the building geometry design can predict the building load demand and renewable energy application potential to some extent. Geometry design interventions are critical to efficiently achieving the goal of zero-energy buildings. In the existing studies, the typicality and representativeness of the object geometry in the practice project are not high, and the influence of different geometry indices on energy savings and photovoltaic (PV) utilization potential under the same type of plane shape is rarely considered. In addition, the surrounding building shading situations considered are single. There is still significant room for improvement in the typical geometries selection and optimization condition settings. This paper presents a study of three typical park office building geometries in hot summer and cold winter regions. An optimization method based on the genetic algorithm and energy consumption simulation is proposed that takes into account both building energy savings and PV utilization potential improvements. The geometry-related indices of each typical geometry are then optimized under different PV layout scenarios and surrounding shading situations, and suitable geometry design strategies for typical office buildings are proposed under each optimization scenario. Geometry optimization can significantly reduce building energy consumption (the building energy-saving rate is 1.3–10.7 %) and increase PV generation (enhancement of 13.37–66.67 % for PV generation potential), thus lowering the net energy consumption of buildings. The findings of this study can be used to guide the design of park office building geometries in hot summer and cold winter regions with the goal of zero energy, as well as to promote the practice of zero-energy office buildings at the regional and national levels.

Climate change impact on energy savings in mixed-mode ventilation office buildings in Brazil

With the projected increase in temperature, coupled with the rise in intensity and frequency of heatwaves caused by climate change, it has become essential to investigate the impact of climate change on building energy consumption and thermal comfort. This study focuses on office buildings with mixed-mode ventilation in Brazil as a case study. Using a typical 15-story office building archetype for various Brazilian cities, considering current and predicted scenarios (2050 and 2080), the potential for energy savings through natural ventilation was assessed. It was observed that the average increase in temperature and wind speed in the predicted climate varied in each city and showed significant variations over the years. Predicted projections under high-emission scenarios (SSP5-8.5-2080) reveal significant increases in energy consumption, highlighting the vulnerability of cities like Belo Horizonte, which could face a 77% increase in total energy consumption. Additionally, the analysis of HVAC hours of use over time indicates a progressive increase, suggesting a potential reduction in natural ventilation as a mitigation strategy. Mitigation measures, especially in the SSP1-2.6 scenario, are crucial to stabilize HVAC consumption and preserve the use of natural ventilation, emphasizing the importance of sustainable approaches to address the energy challenges arising from climate change.

A preliminary investigation of a novel solar-powered absorption-desiccant-radiant cooling system for thermally active buildings

Desiccant air-conditioning systems are considered a competitive alternative to conventional vapor compression cycles. However, the literature lacks detailed studies of such systems when coupled with thermally active buildings and powered by solar energy due to the complexity of modeling and controlling the system. In the present study, a novel hybrid desiccant-dehumidification-absorption system, driven by external compound parabolic concentrators (DDA-XCPC), is used to serve a typical office space in a hot climate zone. The entire system is modeled and simulated dynamically in the TRNSYS environment. The current study investigates the proposed system performance in terms of the achieved thermal comfort, energy consumption, solar fraction, life cycle costs, and carbon emissions. The results reveal superior thermal comfort levels with percentages of people dissatisfied below 5.6 %. The daily solar fraction ranged between 41 and 90 %, with an average of 49 %, whereas the coefficient of performance varied between 0.46 and 1.38 while having a season average of 0.86. Compared to a conventional system, driven by a gas boiler, the proposed system increased the life cycle costs by 6,824 USD due to the large capital investment of the solar thermal loop. However, each 1,000 USD of additional expenses was accompanied by a cutdown of 4,619 kg of CO2 emissions. Increments in the solar system’s capacity (i.e., solar collector area and storage tank volume) have adverse and favorable impacts on the economic and environmental performances, respectively. Therefore, the system can be a viable option whenever green energy production is prioritized and considerably incentivized.

Building energy saving of a rotatable radiative cooling-photovoltaic system by alternate utilization of solar energy and radiative cooling

Building-integrated photovoltaic (BIPV) and Building-integrated radiative cooling (BIRC) are recognized as efficient renewable utilization technologies that can promote building energy savings and reduce carbon dioxide emissions. An innovative rotatable radiative cooling-photovoltaic (RRC-PV) system is proposed, which has multi-functions of photovoltaic power generation, radiative cooling power utilization, and overhang shading. The nonstop alternate utilization of solar energy and free cooling energy from the outer space can be realized. The system breaks the constraint of limited building surface areas and has significant meaning for the renewable energy exploit in high-density cities.In this study, the model of the RRC-PV module is developed and validated with experimental data. Rhino and Grasshopper platform are used, and the radiative cooling power is calculated with a self-developed GH_Cpython program. The RRC-PV system is applied to a typical office in Shenzhen with hot summer and warm winter climate. By applying the RRC-PV modules with total area of 1.68 m2, the daytime PV power generation is 361.9 kWh throughout the year, and the nocturnal radiative cooling power utilization is 246.9 kWh. The building energy usage intensity was reduced from 89.7 kWh/(year·m2) to 83.7 kWh/(year·m2), resulting in payback period of less than 6 years.

Gaussian Analysis of the Elevator Traffic under the Typical Office Building

Elevators serve as indispensable transportation systems in contemporary buildings, facilitating vertical mobility for occupants. However, the proliferation of tall buildings has exacerbated traffic congestion issues within elevator systems. A significant number of elevator passengers voice dissatisfaction with prolonged wait times, leading to impatience and frustration. Traditional approaches to address elevator traffic problems include installing additional elevators or implementing group control systems. However, these solutions often fall short due to designers' limited understanding of elevator traffic dynamics. This research seeks to address these challenges by employing Gaussian analysis to comprehensively examine elevator traffic patterns within a typical office building context. By analyzing both actual monitored data and predictions generated by LS-SVMs, the study aims to offer valuable insights into elevator traffic behavior. Additionally, the research endeavors to serve as a valuable resource for ETA (Elevator Traffic Analysis), providing designers with a deeper understanding of elevator traffic dynamics and guiding the development of more effective solutions to alleviate congestion and improve passenger experience within vertical transportation systems. Through this approach, the study contributes to advancements in elevator design and operation, ultimately enhancing the functionality and efficiency of vertical transportation systems in built environments.

Moisture buffer value for hygroscopic materials with different thicknesses

Moisture buffer value (MBV) is a critical parameter for assessing hygroscopic material's ability to moderate indoor humidity variation. The original MBV theory is strictly valid only for a semi-infinite (or “very thick”) material. When the material is thinner than semi-infinite, the material's thickness will affect its moisture buffering ability. The existing MBV theory is inapplicable. This study proposed a new numerical method to calculate a material's MBV at different thicknesses. The proposed model is simple and efficient. The relation between a material's MBV and thickness and the optimal thickness can be obtained without extensive experimental measurement. What's more, the material's adsorption and desorption isotherms, as well as the material's hysteresis loop and scanning isotherms, are incorporated in the proposed model, making it applicable to advanced desiccant materials like Metal-Organic Frameworks (MOFs). MIL-100(Fe), one of the most promising MOF candidates for indoor humidity control, was used to validate the newly developed model. MBVs of MIL-100(Fe) samples with different thicknesses were measured, and the experimental data closely matched the simulated results. Finally, a building energy consumption simulation model was developed based on the proposed numerical model. A MOF panel with its optimal thickness was placed in the BESTEST typical office room located in Copenhagen. The results show that MOF can reduce about 30 % of the energy consumption of air conditioning in a purely passive way.

Energy consumption, power generation and performance analysis of solar photovoltaic module based building roof

Building energy intensity (BEI) of typical office buildings in Malaysia ranges from 200 to 250 kWh/m2/year, wherein a substantial portion is due to the cooling system. This study evaluates of the performance and suitability of double-laminated monocrystalline solar photovoltaic (PV) glass in comparison to traditional solar PV systems installed on roofs in Malaysian conditions. To address this aim, simulation studies have been conducted to examine the efficacy of Building Attached Photovoltaic (BAPV) and Building Integrated Photovoltaic (BIPV) systems. Key parameters such as heat transfer across the building envelope, cooling demand, daylight utilization, and solar irradiance were analyzed. Additionally, an evaluation of economic viability, including Return on Investment (ROI) and payback period (PBP), was undertaken. Analysis showed that more heat was transferred through the roof on the BIPV building as the U-value of the solar PV glass was higher than the metal deck roof on the BAPV building. The lighting energy in the BIPV building can be saved by up to 80 % as sufficient daylight was entering the building. More than 30 % of the building area had a daylight factor of 1.0 %–3.5 %. From economic viewpoint, the double-laminated monocrystalline solar PV glass had a longer payback period as the initial capital cost was much higher even though the one-off savings and annual savings in the BIPV building were more than the BAPV building.

Influence of short bouts of stair climbing on young adults during prolonged sitting on posture, discomfort, and musculoskeletal performance outcomes: a counterbalanced pilot randomised crossover trial

Prolonged sitting is postulated to influence musculoskeletal performance (cervical flexor endurance, balance, and agility), discomfort and alter cervical spine angles during work-based computer use. Stair climbing breaks may be a great addition at typical and home offices however remain unexplored for its impact on musculoskeletal performance. In our counterbalanced pilot crossover trial, 24 adults were randomised to three interventions: (1) prolonged sitting, (2) interrupted by 2 min of self-paced, and (3) externally paced stair climbing for 2 h. Cervical spine angles were measured every 30 min while balance, agility, endurance, and discomfort were assessed before and after 120 min. Stair climbing interruptions have favourable effects on agility (F = 8.12, p = 0.009, ηp 2 = 0.26) and musculoskeletal discomfort, but failed to improve other musculoskeletal outcomes associated with prolonged sitting. Brief stair climbing interruptions are effective in improving discomfort and agility while pragmatic trials are warranted for translated effects.

Achieving net negative sensible heat release from buildings

Heat is added to the surroundings as a result of replacing natural landscapes with buildings. This includes waste heat from air conditioning systems and heat transferred into the environment from exterior surfaces. Here, we propose a new concept of “negative sensible heat release” from buildings—that is, buildings that put less sensible heat into the environment than that released from the unbuilt terrain upon which the building was constructed. We explore the potential for net negative sensible heat releasing buildings through simulation studies in hot arid and humid cities—Phoenix, and Houston. Results show that it is possible to achieve net negative sensible heat release from low-rise office buildings by simply increasing roof and wall solar reflectance using existing technologies. While typical 2-story office buildings can generate average heat fluxes of around 100 W/m2 (based on building footprint area), by increasing solar reflectance of the roof from 0.2 to 0.9 and solar reflectance of the walls from 0.2 to 0.65, the same building can generate net negative sensible heating of 20 to 40 W/m2. Increasing building insulation and energy efficiency of appliances and air conditioning equipment can further reduce the heat release from buildings. This points to a compelling mechanism whereby buildings can be designed or retrofitted to have a beneficial impact on the local thermal environment.

Smart Readiness Indicator (SRI) as a Decision-Making Tool for Low Carbon Buildings

According to the European Energy Efficiency Directive for Buildings, member states are required to develop long-term strategies to adopt more sustainable, secure, and decarbonized energy systems in buildings by 2050. In this line of approach, an optional common regime has been established to define and calculate the smart readiness of buildings and assess their ability to adapt their operation to the needs of the occupants and the network. Thus, the smart readiness indicator (SRI) emerged, which assesses technological readiness by examining the presence and evaluation of the functionality level of various smart services, aiming at energy savings, the ability of the building to respond to users’ needs, and energy flexibility. This paper focuses on examining the SRI calculation methodology’s application to an office building, which is currently being deeply renovated. Initially, there is an analysis of the SRI, its calculation methodology, and its goals. This is followed by the practical calculation part of the SRI for a typical office building located in Greece and belonging to the climate zone of southern Europe. The results indicate that the SRIs application is not a straightforward issue since parameters that need to be considered are not regulated to the same degree. On the other hand, SRI can provide a stimulus for exploiting the renovation potential of buildings, precisely by integrating the various aspects and linking those to the use of innovative technologies.

Comparative analysis of space layouts and facade systems for office retrofit design in hot climate

ABSTRACT Worldwide, office buildings account for almost one-third of global energy consumption. Therefore, the energy retrofit design of office buildings could reduce total energy consumption. Considering the benefits of advanced facade systems, retrofit facade design is an effective strategy for energy conservation while improving daylight performance, occupant well-being, and productivity. This paper compares the daylight and energy performance of single and double-skin facade systems used in a typical office building in a hot climate with different space layouts. The main objective is to optimize the daylight and energy performance of various facade systems in combination with a wide range of design variables. Simulations were conducted in DesignBuilder software using a multi-objective optimization approach. Eleven design variables and 103 simulations were considered with the objective of enhancing daylight performance while reducing cooling and lighting loads. Based on the results, single-skin facade configurations could enhance daylight performance significantly compared to double-skin facades, while double-skin facades performed better by reducing the risk of glare and annual energy consumption. Using single and double-skin facade systems could reduce annual total energy consumption by 50% and 60% compared to the existing building.

Resilience of Personalized Ventilation in Maintaining Acceptable Breathable Air Quality When Combined with Mixing Ventilation Subject to External Shocks

This work evaluates the ventilation resilience of the combined personalized ventilation (PV)-mixing ventilation (MV) system when implemented in a typical office space. This resilience is first evaluated by monitoring the ability of the PV devices when designed at different supply flow rates to maintain acceptable levels of CO2 at the occupant’s breathing zone when the MV system is subjected to a shock. The shock considers a malfunction of the MV system for periods of 3 h and 6 h, and at shutoff percentages of MV fan flow of 100% and 50%. This is followed by evaluating the resilience of the MV system when the PV air handling unit is shutoff for short periods. The following three aspects of resilience were calculated: the absorptivity, the recovery, and the resilience effectiveness. To monitor the CO2 temporal variation at the breathing zone, a computational fluid dynamic model was developed and validated experimentally. It was found that the resilience effectiveness varied between 0.61 (100% MV shutoff for 6 h and PV at 4 L/s) and 1 (50% MV shutoff for 3 h and PV at 13 L/s). Additionally, CO2 build-up and recovery took minutes during MV malfunctions and seconds during PV malfunctions.