Air Conditioning Energy Research Articles

Structural Safety Analysis of Cantilever External Shading Components of Buildings under Extreme Wind Environment

The high intensity of solar radiation and long sunshine time in the Turpan area lead to the necessity of sunshade construction. Sunshade components can effectively block direct solar radiation and the secondary heating of buildings. Through the analysis of the importance and sensitivity of sunshade components, it was found that the importance of sunshade components accounts for the largest proportion of multi-parameters, and the sensitivity of sunshade components accounts for about 60% of the total. At the same time, the change in sunshade length has an important influence on the proportion of air conditioning energy consumption and space comfort when the sunshade length reached the 0.6 m–0.8 m range. The energy consumption curve of air conditioning no longer decreased and tended to be horizontal, which showed that a sunshade could effectively reduce the energy consumption of air conditioning, while the PMV comfort curve gradually increased and tended to be horizontal, indicating that a sunshade could effectively improve indoor comfort; therefore, a sunshade could reduce direct solar radiation, reduce the energy consumption of air conditioning and improve indoor thermal comfort. In view of the extremely harsh climate characteristics of Turpan, although Turpan needs to carry out shading design, as a typical wind-sensitive component, the structural safety of the visor under the action of an extreme wind environment is the primary focus of designers. The design requires wind loads as control loads. Based on the ANSYS Workbench platform, this study used the fluid–structure coupling technology to calculate and solve for the wind load stress and strain of a horizontal sunshade and a vertical sunshade in a cantilevered external sunshade of different buildings orientations. In this study, by solving for the maximum principal stress and maximum principal elastic strain under 10 working conditions, the results showed that the maximum principal stress of the sun visor under all working conditions was 0.39 MPa, which is much smaller than the tensile strength of C25 concrete. The calculated maximum principal elastic strain of the sun visor was 0.12 × 10−4, which is much smaller than the maximum strain value of concrete. Therefore, the wind load under this research condition had no great influence on the structural safety of the concrete sunshade, which proves the structural feasibility of the building sunshade member in the Turpan area, and provides a reference for the future practical engineering of cantilever members in the Turpan area.

MARTINI: Smart meter driven estimation of HVAC schedules and energy savings based on Wi-Fi sensing and clustering

HVAC systems account for a significant portion of building energy use. Nighttime setback scheduling is an Energy Conservation Measure (ECM) where cooling and heating setpoints are increased and decreased respectively during unoccupied periods with the goal of obtaining energy savings. However, knowledge of a building’s real occupancy is required to maximize the success of this measure. In addition, there is the need for a scalable way to estimate energy savings potential from ECMs that is not limited by building specific parameters and experimental or simulation modeling investments. Here, we propose MARTINI, a sMARt meTer drIveN estImation of occupant-derived Heating, Ventilation and Air Conditioning (HVAC) schedules and energy savings that leverages the ubiquity of energy smart meters and Wi-Fi infrastructure in commercial buildings. We estimate the schedules by clustering Wi-Fi derived occupancy profiles and, estimate energy savings by shifting ramp-up and setback times observed in typical operational/static load profiles that are obtained by clustering smart meter energy profiles. Our case-study results with five buildings over seven months show an average of 8.1%–10.8% (summer) and 0.2%–5.9% (fall) chilled water energy savings when HVAC system operation is aligned with occupancy. We validate our method with results from Building Energy Performance Simulation (BEPS) and find that estimated average savings of MARTINI are within 0.9%–2.4% of the BEPS predictions. In the absence of occupancy information, we can still estimate potential savings from increasing ramp-up time and decreasing setback start time. In 51 academic buildings, we find savings potentials between 1%–5%.

Energy-saving effects of yard spaces considering spatiotemporal activity patterns of rural Chinese farm households

The space-occupation behavior of rural residents can occur in an “indoor air-conditioned environment” or a “courtyard natural environment.” High-quality outdoor environments can attract residents to spend more time in the outdoor space, thereby reducing the use of indoor space and building energy consumption. Quantifying the complementary effects of indoor and outdoor spaces on the thermal environmental quality is fundamental in detecting the potential of behavioral activities in building energy-saving. This study on Chinese farmhouses and resident space-occupation behavior in nine districts across various climatic zones investigated the typical farmhouse physical models and resident occupancy rates. Indoor temperature and humidity parameters without air conditioning were simulated, and the predicted indoor and outdoor mean thermal sensation votes were measured and compared hourly. The number of hours of indoor space out of comfort zone but yard space in comfort zone were calculated and analyzed. Finally, the air conditioning energy consumption of farmhouses with and without yard spaces was calculated and compared, considering the difference in spatiotemporal behavior in various rural buildings. The results indicated that yard spaces in rural buildings had a complementary effect on thermal comfort environment provision and have the potential to reduce building energy consumption of farmhouses by 7.21%–33.99%.

A solar thermal driven ORC-VFR system employed in subtropical Mediterranean climatic building

This paper investigates the configuration of solar thermal collector driven organic Rankine cycle (ORC) utilized to power air-conditioning system of the two-story office building in Paralimni, Cyprus, through a Variable-Refrigerant-Flow (VRF) system. The reason to choose this Mediterranean climate of Paralimni, Cyprus, is due to its higher dependency on fossil fuels compared to many other countries in the EU and with a high potential of harnessing solar irradiations and demand for air-conditioning (AC) loads. This location is categorized as warm temperate zones, subtropical climates and is placed in the subcategory of Mediterranean climates with humid winters and dry summers according to climatic zone, highly demanding for air conditioning. Based on the climatic data of the study area, this system can make an effective performance. Modeling the building and estimating the AC system power consumption is carried out in the DesignBuilder. Designing the organic Rankine cycle is done with EES. A solar hot water system is designed with TRNSYS to supply the required mass flow rate of water at the desired temperature of 95 °C. In this climate, the annual surface irradiation rate is 1,793 kWh/m2 whilst the AC energy requirement of a two-story building is 7,909 kWh. The employed ORC with an internal heat exchanger is designed with a constant output rate of 3.920 kW, which delivers a total of 8,154 kWh yearly. The required heat input of the ORC is supplied by a solar hot water system, employing evacuated tube collectors. The solar system consumes a 454 kWh auxiliary heating rate per year to deliver the desired mass flow rate and outlet temperature for the ORC. As a result, the designed solar-driven ORC delivers a net of (8,154 – 454) kWh = 7,700 kWh energy each year, meaning 7,700 kWh energy saving per year, equal to 97% of VRF annual energy demand. This amount of yearly energy saving yields 2,010 USD yearly capital saving as the reward of investment in this system, and defining a 20-year project, the implementation of this solar-driven power generation system at the end of the project's lifetime would save 25,049 USD.

Analysis on occupant behavior of split air conditioner in hotel buildings in the Yangze River Region

The split air conditioner is commonly used in hotel buildings because of its flexible function. However, there are some differences in occupant behavior (OB) regarding the usage of split and central air conditioner systems, so that more targeted studies are needed. Based on data recorded from 104 air conditioners in 13 hotels in 5 cities from March to July, this study analyzed OB in split air conditioner usages in hotel buildings. An OB model of air conditioner usage in hotels was established by the Monte Carlo stochastic model and the Markov chain method (MCM). Analysis of the results show that 58.0% of occupants turn on the air conditioner within 2 min of entering their room, and that probability is affected by room temperature. By simulating the OB model in DeST, the air conditioning energy consumption index of hotel buildings was found to be 12.6 kWh/m2, which is 41.4% lower than the normal method of usage.

A weather-clustering and energy-thermal comfort optimization methodology for indoor cooling in subtropical desert climates

This paper proposes a novel methodology to assess the yearly Heating Ventilation Air Conditioning (HVAC) energy costs and indoor comfort levels for indoor spaces. The methodology involves a weather clustering technique coupled with a simulation-based multi-objective optimization for HVAC systems operation control. The clustering technique is utilized to determine representative days that capture the yearly variability of outdoor air temperature, total solar radiation on horizontal surface, wind speed, and outdoor relative humidity from historical time series. The optimization framework then determines the optimal cooling operation strategies that simultaneously minimize energy consumption cost and thermal discomfort for each representative day. Such clustering-based approach, particularly, enables the assessment of the annual operation of the HVAC using representative daily weather conditions while avoiding the high computational costs of a day-by-day optimization. The numerical prospects of the proposed framework are illustrated using an office building located in Saudi Arabia, i.e., under subtropical desert conditions. The results show that the proposed methodology can achieve reductions of up to 17.6% and 19.4% in annual cooling consumption cost and thermal discomfort, respectively, compared to standard baseline policies.

Prediction method of energy consumption for high building based on LMBP neural network

With the power consumption of high-rise buildings rising year by year, energy consumption of high-rise buildings has become the main object of energy-saving supervision and transformation, and its prediction has become a research hotspot. Aiming at the problem that the existing total energy consumption forecasting methods cannot accurately distinguish the consumption direction of high-rise building and the forecasting accuracy is low. LM algorithm is used to improve the standard BP neural network, and a prediction model of lighting energy consumption for high-rise buildings based on LMBP neural network is established. According to the prediction results of lighting energy consumption, hourly average outdoor temperature, hourly average outdoor relative humidity, weather characteristics, holidays, hourly average wind speed and 24 hourly hours a day, the energy consumption of air conditioning, power consumption and special energy consumption can be predicted separately. The experimental results show that the MAE and RMSE predicted by the design model for air conditioning energy consumption, power energy consumption and special energy consumption are 5.4707 and 8.6575, 1.7916 and 2.9356, 1.6075 and 2.2178 respectively, which are smaller than the comparison model MAE and RMSE, which proves that the design model can more accurately and effectively predict the sub item energy consumption in the energy consumption of high-rise buildings.

Assessment of airflow and heat transfer around a thermal manikin in a premise served by DOAS and ceiling fans

Ceiling fan improves thermal comfort and reduces air-conditioning energy consumption in super low energy buildings operated at warmer room air temperature with increased air movement. This paper investigated the characteristics of airflow generated by the ceiling fans around a thermal manikin body, and the convective heat transfer caused by the airflow distribution through experiment and CFD for standing and seated postures. The standing and seated postures showed almost the same convective heat transfer for the whole-body, but the contribution of mean velocity and turbulence components were different. Turbulence intensity (median value and dispersion) of the seated posture was higher, and the dispersion range reaches between 20 and 84% despite the average velocity being relatively low compared to the standing posture when the fan speed exceeds 100 rpm. The convective heat transfer coefficient for the whole-body caused by the ceiling fan was 32–75% of the horizontal air flow cases of previous studies at inflow air speed under 1.1 m/s for both postures. On the other hand, under ceiling fan flow the heat transfer coefficient at the lower body of the manikin remains relatively low compared to horizontal flow even at increased fan speeds. This difference potentially leads to a different thermal sensation in corresponding body parts between the ceiling fan flow and the horizontal flow situations.

A method for energy consumption optimization of air conditioning systems based on load prediction and energy flexibility

A new method for heating ventilation and air conditioning (HVAC) energy consumption optimization based on load prediction and energy flexibility is proposed. First, the energy consumption prediction of the chillers and air conditioning terminals is made. Then, an optimal chiller loading (OCL) equation is built, and is new in the following aspects: the electricity consumption of air conditioning terminals is included and amended by a penalty coefficient to consider thermal comfort. This penalty coefficient is calculated based on energy flexibility. The prediction results are used as constraints of the OCL equation. Next, the sensitiveness of the system's energy consumption with different penalty coefficients and different settled comfort air temperatures are tested. All cases are solved by the particle swarm optimization (PSO) algorithm and validated by the genetic algorithm (GA). Finally, economic analyses are made. The results show that the comprehensive energy-saving ratio is about 10%, and the discounted payback value is 5.8 years. The penalty coefficient is more sensitive than the settled comfort air temperature for the system's energy saving. This proposed method is significant for improving the reliability of the feedforward control strategy and reducing the response time of the feedback control strategy.

Optimization of insulation layer location and distribution considering maximum time lag and damping factor

Approximately 35% of air conditioning energy consumption in buildings is caused by the heat transfer through the external walls, and this can be reduced by changing the location and distribution of insulation layers. To optimize the location and distribution of the insulation layers, transient heat conduction equation is solved by using the thermal quadrupole method, and a combinatorial algorithm is adopted to determine the wall structures. Time lag (TL) and damping factor (DF) are two evaluation indexes of wall thermal performance. The multi-objective algorithm is then adopted to determine the best wall configuration considering the maximum TL and DF. The external wall is composed of 20-cm thick reinforced concrete and 6-cm thick insulation layer, and the insulation layer is divided into one, two and three parts, respectively. The Pareto optimality shows that TL and DF of the wall with evenly distributed insulation layers are larger than that with unevenly distributed layers. For the same thickness of the insulation, both the DF and TL increase with increasing the number of the layers. The best performance is achieved when the three layers of insulation are placed on the outer surface, in the middle and 1 cm from the inner surface of the wall.

AN EMPIRICAL STUDY OF STUDENTS’ AIR CONDITIONING ENERGY USE BEHAVIOR IN UNIVERSITY DORMITORIES—A CASE OF NANJING, CHINA

ABSTRACT People’s lifestyle and energy use behavior have been shown to influence the energy consumption of buildings. Since university dormitories consume a significant amount of energy, it is important to investigate the energy use behavior of students in such dormitories. The aim of this study was therefore to improve students’ energy use behavior in order to reduce the energy consumption of air conditioning in university dormitories. Based on a review of relevant literature, air conditioning energy use behavior was defined, and influencing factors were identified from demographic characteristics, indoor characteristics of personnel, as well as physiological and psychological factors. Students’ air conditioning energy use behavior during the summer and influencing factors of students’ energy use behavior was then revealed by an analysis of 332 respondents to a questionnaire survey. The results indicated that differences in energy use behavior are influenced by: age, major and monthly living expense of students; indoor characteristics such as the number of students in the dormitory, time spent in the dormitory, distance to an air conditioning unit; physiological factors including body comfort, clothing, and activity intensity; and psychological factors including cognition degree, values, living habits, attitude, perceived behavior control, and subjective norms. Based on these findings, suggestions for reducing energy consumed by air conditioning were proposed and intervention studies then conducted to confirm that energy use behavior had improved, with subsequent consumption savings after the intervention. This study adds to the body of knowledge in the field of energy use behavior and provides guidance for the sustainable development of green universities.

AN EMPIRICAL STUDY OF STUDENTS’ AIR CONDITIONING ENERGY USE BEHAVIOR IN UNIVERSITY DORMITORIES—A CASE OF NANJING, CHINA

ABSTRACT People’s lifestyle and energy use behavior have been shown to influence the energy consumption of buildings. Since university dormitories consume a significant amount of energy, it is important to investigate the energy use behavior of students in such dormitories. The aim of this study was therefore to improve students’ energy use behavior in order to reduce the energy consumption of air conditioning in university dormitories. Based on a review of relevant literature, air conditioning energy use behavior was defined, and influencing factors were identified from demographic characteristics, indoor characteristics of personnel, as well as physiological and psychological factors. Students’ air conditioning energy use behavior during the summer and influencing factors of students’ energy use behavior was then revealed by an analysis of 332 respondents to a questionnaire survey. The results indicated that differences in energy use behavior are influenced by: age, major and monthly living expense of students; indoor characteristics such as the number of students in the dormitory, time spent in the dormitory, distance to an air conditioning unit; physiological factors including body comfort, clothing, and activity intensity; and psychological factors including cognition degree, values, living habits, attitude, perceived behavior control, and subjective norms. Based on these findings, suggestions for reducing energy consumed by air conditioning were proposed and intervention studies then conducted to confirm that energy use behavior had improved, with subsequent consumption savings after the intervention. This study adds to the body of knowledge in the field of energy use behavior and provides guidance for the sustainable development of green universities.

Proposal of Energy Management Method for Air Conditioning in Operational Office Buildings

In recent years, the building industry has been focusing on creating new value by combining data collected in buildings with advanced analytical technologies such as AI and digital twin. In particular, there are high expectations for energy conservation, as indicated by keywords such as ZEB and carbon neutral. This study combines BEMS data and machine learning to build a simulation model that predicts the indoor environment and air conditioner energy, with the aim of achieving carbon neutrality in office buildings. We have constructed a simulation model to predict energy consumption of indoor environment and air conditioners by combining BEMS data and machine learning, and confirmed that the model can predict the indoor environment and air conditioner energy with high accuracy.

Automatic Compliance Check of Window-to-Wall Ratio Software Embeded Intelligent Algorithms in Revit Modeling

Window-to-Wall Ratio(WWR) is a crucial building envelope element that decides the air conditioning and lighting energy consumption in the building. Controlling WWR within a reasonable range is of great significance to building energy conservation. Due to the importance of WWR’s selection in Revit modeling, an automatic compliance check software in Revit Modeling is developed to ensure the WWR of Revit model within a reasonable range. The range is given in Design Standard for Energy Efficiency of Public Buildings (GB50189-2015,China). Based on the value range, the enumeration-based WWR compliance inspection software was developed in C# language and integrated into Revit to achieve compliance check on Revit model. Software testing was conducted for a certain office building in Shanghai, China. And Ecotect was used to analyze the thermal environment of unchecked model and checked model, respectively. The result shows that this software can automatically obtain the WWR of each facade of the current model, and determine whether it meets the range of the building location. When a facade does not meet the specification, it can be quickly and automatically adjusted to the appropriate range within the scope. By comparing the Ecotect thermal environment analysis results of unchecked and checked model, it is found that the heating and cooling loads are reduced after the model is checked with intelligent algorithms.

A short review on measuring impact of microencapsulated phase change material in mitigating urban heat island

The mitigating urban heat island (UHI) has been extensively studied by many researchers because of its favorable Micro Encapsulated Phase Change Material (MEPCM) property. This helps to reduce the indoor temperature and this article reviews the major effects of reducing the indoor temperature by using MEPCM. The study wants to illustrate that the Phase Change Material (PCM) application is helpful for surface temperature supervision and enhancing indoor thermal performance by passive cooling. Suitable PCMs will maintain the comfort room temperature in the summer by dropping the inner temperature and increasing the temperature in winter. Basic methods of PCM incorporation are macro encapsulation and micro encapsulate by PCM implantation in the buildings. Encapsulation of PCM is essential to increase fusion of heat in the material. The several manufacturing companies on the commercial - scale produced a variety of PCMs, fatty acids, Paraffin, and Fatty acid esters as (MEPCM). PCM application in the Inter Building Environment (IBM), which is a PCM embedded building envelope, reduces the negative impact on energy usage and reasonable progress of yearly Heating Ventilation and Air Conditioning (HVAC) energy consumption. A basic understanding of UHI under various PCM is used to analyze the thermal effect in a better.

Study on optimal design of airport control hall ventilation environment based on butterfly software——Taking the design of Sining air traffic control support building as an example

Airport control hall is the key organization of air traffic control system, mainly used to manage various flight activities of the airport. The control hall contains numerous control seats and control personnel. It is particularly important to create a comfortable indoor environment for the control personnel in a high-intensity working environment. But due to the current design code and standard lack for airport control hall and affiliated offices of the requirements of the physical environment, designers often excessive attention to functional requirements in the design and the facade, while ignoring the control hall indoor environment requirement, so the chaos such as plane layout, facade window problems such as unreasonable, As a result, natural ventilation is not smooth, air conditioning energy consumption increases, and indoor comfort is seriously affected.Sining AIR traffic control Support Building is one of the three major air traffic control projects in northwest China during the 13th Five-Year Plan period. In the preliminary design process of the scheme, the design team used Butterfly tool based on Grasshopper software to conduct computer simulation analysis on the natural ventilation condition of the scheme, comb out the optimization design method and conduct comparative verification. Improve indoor comfort, reduce building energy consumption, and finally summarize the air traffic control hall design strategy adapted to Sining’s unique natural environment, which provides reference for other air traffic control support building projects in northwest China.

The alternate operation control strategy between natural ventilation and air-conditioning considering delay time

Most research in the field of indoor thermal environment control has been devoted to the search for an appropriate on/off temperature of air-conditioning while relatively ignoring the energy-saving effect of the transition period length after air-conditioning turned off. We proposed a control model for the alternate operation between natural ventilation and air-conditioning to measure the delay time of natural ventilation after air-conditioning turned off. We compared the energy consumption of two cooling modes (continuous cooling and alternative operation between natural ventilation and air-conditioning) in different thermal capacity buildings in China’s hot summer and warm winter areas. Furthermore, we obtain the delay time of natural ventilation under different thermal capacity buildings. The results indicate that buildings with more thermal capacity have a greater delay time of natural ventilation. Alternative operation strategy can save at least 15% energy consumption compared with continuous air-conditioning cooling. The results are helpful to guide residents to adjust their use habits of air-conditioning according to the delay time of natural ventilation and to alleviate the pressure of air conditioning energy consumption in hot summer and warm winter areas in China.

A feedforward air-conditioning energy management method for high-speed railway sleeper compartment

In this paper, we propose a feedforward air conditioning temperature control method for high-speed railway locomotives with sleeper compartments to improve energy efficiency. First, we construct the geometric model of two typical types of compartments and three types of passengers. Then, based on the analysis of possible passenger layout patterns in each compartment, we utilize computational fluid dynamics simulations to calculate the optimal air volume for each pattern. The optimal air volume is calculated to guarantee the passenger comfort level and reduce the energy cost. In addition, we adopt an image recognition method to detect the number and types of passengers in each compartment. Passenger layout patterns serve as independent variables to determine the corresponding optimal air volume. Finally, numerical simulations were conducted to verify the effectiveness of the proposed method.

해외 빙상경기장의 친환경 계획요소에 관한 연구

Since 1994, sports on a global scale have made it essential to consider eco-friendliness in terms of ecology, society and economy, aiming to inspire a sustainable future. In particular, compared to the summer stadium, the ice skating stadium requires a lot of water and requires a lot of energy for heating, ventilation and air conditioning. In addition, although a lot of water is consumed in the process of making the floor, ice making and maintenance technology also consumes a large amount of energy and adversely affects the environment by generating refrigerant gas, which is a pollutant that is harmful to the environment. Furthermore, it has been reported to have a detrimental effect on the health of users as well. Therefore, in this study, environmental conditions and eco-friendly considerations are checked centering on the ice skating stadium, which needs more consideration in terms of energy and usability, and the plan elements that need to be supplemented for the eco-friendly use of the ice skating stadium were derived in the future. Therefore, in this study, the main eco-friendly characteristics were identified by analyzing the eco-friendly planning factors applied to 12 overseas ice skating stadiums that received awards for LEED certification and eco-friendly technology. In the main architectural elements of each analysis target, such as layout, form, plan, and elevation plan, the eco-friendly characteristics were examined. In addition, the application rate of eco-friendly planning elements was checked based on the standard supplemented with the LEED certification items to the domestic green building certification items, and the eco-friendly characteristics applied to the stadium were derived. As a result of the survey, the application rate of eco-friendly planning elements in overseas representative eco-friendly ice skating stadiums was indoor environment 96.4%, land use and transportation 94.8%, materials and resources 94.6%, maintenance 94.4%, water resource management 85.8%, ecological environment 64.8%, energy and environment Pollution is 62.2%. In this regard, it was confirmed that overseas ice skating stadiums emphasize eco-friendly considerations, especially in the indoor environment, land use and transportation, material and resource planning, and water resources. In addition, it was found that a plan that prioritizes eco-friendly materials and environmental load is being made, focusing on the health and convenience of users of overseas ice skating stadiums. Through this study, based on the technology applied to the overseas eco-friendly ice rink, it was possible to examine the possibility of applying the technology that can be applied to the domestic ice skating stadiums in the future.

A Solar Water-Heating Smart Window by Integration of the Water Flow System and the Electrochromic Window Based on Reversible Metal Electrodeposition.

Various smart windows with dynamic modulation of the light transmittance have been developed rapidly in recent years. However, current design of the smart windows can only modulate the indoor solar irradiation instead of effectively utilize them. Here, a solar water‐heating (SWH) smart window is proposed by the integration of the traditional electrochromic window and the water flow system, which can not only provide dynamic daylight modulation but also harvest the solar energy and store them by heating water. In the SWH window, the reversible metal electrodeposition (RME) not only provides daylight modulation but also provides metal layer working as a flat‐plate solar collector for energy harvesting. Compared with traditional electrochromic windows, the SWH window with a water flow system can more effectively modulate the indoor temperature, owing to the significantly enhanced tunability of the thermal irradiation from the window. Compared with water‐flow windows, the RME provide a metallic layer for efficient light harvesting, up to 42% solar energy can be effectively harvested and stored as hot water. Such an SWH smart window is promising to reduce the heating, lighting, and air conditioning energy consumption, which may bring new insights in the design of the next‐generation green buildings.