Air Conditioning Energy Consumption Research Articles

Influencing Factors on Air Conditioning Energy Consumption of Naturally Ventilated Research Buildings Based on Actual HVAC Behaviours

The fixed description of HVAC behaviours leads to inaccurate prediction of air conditioning energy consumption, which in turn affects the appropriateness and effectiveness of energy conservation strategies. Based on a naturally ventilated research building located in Hangzhou, China, a stochastic prediction model reflecting actual HVAC behaviours is established based on clustering analysis and the Monte Carlo method, and it is integrated into the AC energy consumption simulation through Python programming. Then, important factors influencing AC energy consumption are clarified by importance analysis based on random forest regression, and the integrated strategies based on them are studied based on the simulation and control variable approach. As a result, the error rate between the measured and simulated AC power consumption is −5.24% and 2.56% in the heating and cooling conditions, respectively. And the relative importance and the number of important factors following the actual HVAC behaviours are remarkably different from those based on the fixed behavioural pattern. The implementation of integrated AC energy conservation strategies based on important influencing factors achieves 35.02% energy savings. Consequently, a theoretical basis for the accurate prediction of AC energy consumption and efficient implementation of energy conservation strategies is established.

Extensive green roofs thermal effect and energy saving indoor by cooling

This work analyzes the thermal effect of extensive green roofs (EGR), in different climatic conditions of eight cities in Mexico. A house is simulated and temperature, comfort sensation and air conditioning energy consumption are analyzed. The results show that the extensive green roof helps to decrease the maximum interior temperature, especially in the rooms located on the upper floor, where greater energy saving for air conditioning (cooling) is also observed. In all the cases studied, EGRs contribute to achieve thermal comfort conditions; in fact, their implementation under some climatic conditions avoids the use of air conditioning.

An investigation on the energy-saving potential of thermal insulating walls constructed with super thin vacuum insulated panels

Using EnergyPlus software to simulate the energy consumption of residential buildings in Harbin, Beijing, Nanjing, Haikou, and Kunming under various conditions, this study investigated the energy-saving potential of thermal insulating walls constructed with Super Thin Panel (STP). It also examined the benefits and drawbacks of the heat transfer performance of the panels, as well as the potential and viability of using STP as insulation materials. The findings demonstrated that in Harbin, Beijing, and Nanjing, the overall energy consumption for heating, cooling, and air conditioning dropped as the thickness of the insulation layer increased. Haikou had no need for any heating energy, and cooling energy use reduced as insulation thickness grew. In Kunming, the total energy consumption for cooling and air conditioning increased as insulation layer thickness grew while the energy consumption for heating reduced as insulation layer thickness increased. According to the findings, when STP panels is utilized as a thermal insulation material, its thermal insulation effect is remarkable. Under the same thermal insulation effect, the thickness was substantially thinner than that of conventional thermal insulation material. STP implementation had the biggest impact in Harbin, followed by Beijing, and had little influence in Haikou and Kunming, where there was essentially no heating demand. This implies that the use of STP vacuum insulation panels in cold areas of China has a promising future.

Research on energy consumption analysis of air conditioning and refrigeration equipment based on perceptron model

Abstract This paper mainly studies the energy consumption of air conditioning and refrigeration system from the perspective of the dynamic operation of air conditioning systems and selects the energy consumption of a chiller system, cooling tower system, chilled water pump system and fan coil system, which affect the energy consumption of air conditioning system, as model variables. An integrated learning method based on a multilayer perceptron is proposed to integrate spatial features with temporal features, and a spatio-temporal prediction model for air conditioning energy consumption analysis is established under the Seq2Seq framework, and then the input curves of the four variables with load change under the optimal operation of the air conditioning system under dynamic load are derived. The results show that the deviation between the simulated value and the measured, calculated value of the energy consumption analysis model of air conditioning and refrigeration equipment based on the multilayer perceptron is within 5%, which can effectively and accurately predict and reduce air conditioning energy consumption by 15% to 20%. The maximum energy-saving efficiency can reach 30% when the air conditioning system is in optimal operation under dynamic load, and the energy-saving effect of the chiller, chilled water pump and cooling water pump is relatively significant. The research results of this paper have a certain reference value for reducing the energy consumption of air conditioning systems in practice.

Decoupling the complexities of air-conditioning cooling energy use in express hotels by data mining approaches

The air-conditioning (AC) energy use in express hotels is stochastic with the high coupling relationships amongst AC usage, indoor temperature and energy consumption. Such complexities and stochasticity make it hard to facilitate energy saving with clear effect on indoor environment. However, lacking analyses of high-resolution occupants’ energy use makes it difficult to achieve such goals due to the split form of ACs and various thermal comfort of guests in express hotels. Therefore, this study made a serial analysis on the AC energy use in a more detailed scope. The stochastic AC usage, indoor temperature and AC energy consumption were quantified by proposed typical patterns with the cluster method. The stochasticity was described by four typical patterns for each aspect. After the quantifications, the relationships amongst these three aspects were decoupled by the proposed energy use decoupling model. Two data mining methods, namely, random forest method and decision tree method, were employed to achieve this purpose, respectively. With these models, the impacts of each variable on AC energy consumption and explicit relationships of operation rules for management are presented. Strictly limiting set point temperature higher than 23°C is the effective way to save energy for most of AC usage patterns. This study can provide a deeper understanding of AC energy use in express hotels, and benefits energy saving and facility operation in express hotels.

Development of dynamic shading control for daylight measures in green buildings towards overall energy efficiency of lighting and air-conditioning systems

The introduction of daylight can improve buildings’ energy efficiency and bring benefit to occupant satisfaction. However, the introduction of daylight may accompany with excessive heat. Properly counterbalancing the energy consumption of air conditioning and lighting systems owing to the entry of daylight is a critical control target of dynamic shading adjustment in cooling season. Most dynamic shading control strategies in use only consider one single system. Additionally, for advanced control mode like performance-based control, the predictive model usually only examines the instantaneous effect of energy performance to determine the shading adjustment state, unable to quantify the overall influence of shading adjustment state on building energy consumption. In order to address this issue, special consideration is given to calculating the cumulative contribution of heat gains to cooling load in this study. An overall energy-efficient shading control metric is proposed and used as basis to develop optimized dynamic shading control strategy. An application example demonstrates that the SGR-Optimal control strategy can further save energy by 21.8% ~ 38.8% when compared to the Rule-based control strategy, thus allowing a better exploration of the energy efficiency potential of daylight measure.

Analysis of the Influence of Office Building Operating Characteristics on Carbon Emissions in Cold Regions

Reducing buildings’ operational carbon dioxide emissions has become a crucial element in China’s efforts to achieve carbon peak and carbon neutrality targets. This study focus on the influence of office building operating characteristics on carbon emissions in cold regions. By utilizing DesignBuilder v7.0.0.096 to conduct numerical simulations of 10 different operating conditions for heating, ventilation and air-conditioning (HVAC) and lighting systems, this study solves the problems in the past of poor comfort and high energy consumption with manual management and achieves a win-win situation for health and environmental protection. The study shows that by implementing a mixed mode of mechanical ventilation and natural ventilation based on outdoor climate conditions and design requirements, unsatisfied hours can be reduced by 202 h compared to the traditional air condition heating operation mode for both winter and summer seasons. Furthermore, compared to a year-round HVAC operation mode, the air-conditioning energy consumption can be reduced by 19%, resulting in a carbon emissions reduction of 1.45 kg CO2/(m2·a). Additionally, for every 2 °C increase in the outdoor temperature, the cooling energy consumption decreases by 2–5%. In terms of lighting, the intelligent lighting mode can reduce energy consumption by 31.04%, leading to a carbon emissions reduction of 3.04 kg CO2/(m2·a). The coupling operation characteristics of mixed mode, intelligent lighting, and energy-saving lamps can achieve a maximum saving of 83.46 MWh of electricity and approximately CNY 72,000 every year, with a static payback period of approximately 2.7 years. This operational strategy, which fully considers the utilization of natural ventilation and daylighting in conjunction with traditional design approaches, improves indoor air quality and ventilation conditions, while also maximizing the energy-saving and carbon reduction potential. The study results provide valuable design and operational guidance for new and existing office buildings in cold regions, to effectively reduce carbon emissions, while offering significant investment returns.

WIND ENVIRONMENT ANALYSIS OF GREEN BUILDING BASED ON BUILDING INFORMATION MODELING (BIM)

ABSTRACT This papers offers a more simple and effective method to simulate indoor and outdoor wind field at the same time, while also exploring the influence of indoor wind field on air conditioning energy consumption. This paper presents an application framework for simulating indoor and outdoor wind field and an air conditioning system based on BIM. Through the BIM software with built-in CFD calculation, the indoor and outdoor wind environment is simulated, and it is found that the outdoor vertical wind field has a certain influence on indoor ventilation. Meanwhile, the air conditioning energy consumption of the building is calculated, and the influence of indoor natural ventilation on air conditioning energy consumption is quantified. This paper provides important guidance for building researchers and practitioners to better align BIM development with green building development in the future.

Optimizing Energy Efficiency in High-Rise Residential Buildings in Abu Dhabi’s Hot Climate: Exploring the Potential of Double Skin Façades

This study investigates energy efficiency in high-rise residential buildings in Abu Dhabi, where the increased use of glass building façades has led to increased air-conditioning costs due to heat gain. The research focuses on evaluating the type of glass and the appropriate cavity between glass façades to minimize energy consumption while incorporating sustainability and innovative design principles. To achieve these objectives, this study employs a Double Skin Façade (DSF), a high-performance façade that adapts to the external climate conditions to fulfill internal cooling load requirements and meet occupants’ needs. Data were collected through an online survey distributed among residents of a selected residential tower, and a combination of qualitative and quantitative approaches was utilized to analyze the gathered information. The selected case study was analyzed using Energy Plus simulation software using the existing data and available details. The analysis aimed to identify the optimal DSF design that significantly enhances energy efficiency. The findings of this study emphasize the substantial impact of the optimum DSF design on energy efficiency in high-rise residential buildings. Through modeling existing data and comparing them with new model results for each variable, this study demonstrates that a DSF with a 35 cm cavity, comprising a double-glazed single skin layer in the interior and a Low-E double-glazed single skin layer as an outer layer, can reduce overall air-conditioning energy consumption by over 25%. These outcomes provide valuable insights into implementing DSF as a solution to address the unique energy challenges presented by high-rise residential buildings in hot climates.

Indices for dynamic evaluation of indoor humidity and thermal environment

Moisture sources release wet-components into indoor air, affecting the occupants’ health, air conditioning energy consumption, and building service-life. Wet-component evaporation and diffusion are dynamic processes, and yet existing indices are limited in their ability to accurately describe moisture sources dynamically influencing indoor air. Here we propose two indices CRIt(H), an index of the rate of humidity contribution change, and CRIt(c) as the rate of indoor climate contribution change. Taking a humidifier as the source, we use our indices to compare by experiment the impact of source parameters on a variety of ambient conditions over space and time. Our approach accurately reflects how the moisture source affect humidity and temperature, with identification of specific stages of dynamic influence. This study will be beneficial for the establishment of transient indoor environmental models, regulation of air-conditioning systems, and sustainable control of the indoor environment.

Influence of heating, air conditioning and vehicle automation on the energy and power demand of electromobility

With the increasing number of electric vehicles in the transport sector, the relevance of accurate energy and power demand predictions of electromobility is growing. Thereby, different vehicle functions, especially heating and air conditioning and vehicle automation, have a significant influence. In accordance with the upcoming Euro-7 emissions standard, the energy consumption for heating even has to be contained in the manufacturer’s consumption data in the future. To increase the accuracy of energy and power demand predictions of electromobility, the energy consumption of vehicle functions such as heating and air conditioning as well as the energy savings through vehicle automation must be considered.This paper presents approaches for modeling and simulation the energy consumption of heating, air conditioning and vehicle automation which can be used as an extension of electric vehicles WLTP (Worldwide Harmonized Light-Duty Vehicles Test Procedure) consumption simulation on the level of vehicle classes. The Germany-wide results of the electric vehicles energy demand for heating and air conditioning on the level of NUTS3-areas (Nomenclature of territorial units for statistics) and vehicle classes show regionally different results and confirm the relevance of the research approach. Vehicle automation results are described on the level of the five SAE automation levels (Society of Automotive Engineers automation levels) and the vehicle classes. The approaches and results can be used for single vehicles or assumed vehicle fleets.

A Sustainable Indoor Air Quality Monitoring Approach through Potable Living Wall for Closed Confined Spaces: A Way Forward to Fight Covid19

The COVID-19 pandemic has greatly influenced various aspects of life, part of which has consequently paved the way toward improvements in building design criteria, especially for closed confined spaces. The closed confined spaces are directly proportional to the quantity and quality of the volatile organic compounds (VOCs) present in the atmosphere, from which human beings breathe. In managing the impact produced by VOCs, a practical, sustainable, economical and environmentally friendly concept of indoor living walls has become a prominent feature for improving the indoor air quality (IAQ) of closed confined spaces to efficiently reduce sick building syndrome (SBS) factors. In modification of common practice of ventilation systems, living wall technology leverages the natural ability of plants to purify indoor air quality by reducing air pollutants and allows the recycling of indoor air and the creation of a productive and inspiring environment. In this paper, the concept of a portable living wall through the use of a native plant species locally available in Sindh, Pakistan is introduced. Herein, the portable living concept was assessed by means of the design, construction, and data collection (testing and monitoring) of various environmental parameters carried out before and after the installation of the living wall. The study was monitored for 90 days, and analyses for various types of air pollutants were carried out in the environmental laboratory. During the monitoring period, the parameters humidity, VOCs, hazardous chemicals of concern (HCOC), CO2 and CO showed reductions in their values, with changes observed ranging from 61.5 to 58%, 0.66 to 0.01 ppm, 0.2 to 0.01 ppm, 1070 to 528 ppm and 0.2 to 0.01 ppm, respectively. The outcomes showed noticeable changes in air pollutants coupled with reductions in heating, ventilation and air conditioning (HVAC) energy consumption by up to 25%, mainly due to limited air requirements for ventilation.

Thermodynamic performance analysis of air-to-air hybrid heat recovery unit driven by pump combined with booster

The air conditioning energy consumption for fresh air handling in buildings increases yearly, especially in low energy buildings. This energy consumption can be greatly reduced when exhaust air is recovered for preheating or precooling fresh air. Then, significant savings in the total energy consumption in buildings will be achieved, which in turn helps achieve the carbon peak in the building field. In this paper, a booster/pump coupled energy recovery ventilator is proposed for energy recovery in buildings. The system performance, which depends on the loop number and combination strategies were analyzed and compared through model simulations. Results indicate that the heat transfer rate of different coupling systems increases with the temperature difference. In summer, the pump/booster driven dual-loop system has the highest average temperature effectiveness of 47.3% and average heat transfer rate of 4.97 kW. The booster/booster-driven dual-loop system has the highest average heat transfer rate of 5.07 kW and average temperature effectiveness of 47.1%. The average temperature effectiveness of the pump/booster/booster driven triple-loop system reaches up to 45% and average heat transfer rate of 4.73 kW. The booster/booster/booster-driven triple-loop system has the highest average heat transfer rate of 4.82 kW and average temperature effectiveness of 44.7%. In winter, the maximum average heat transfer rate and temperature effectiveness of the pump/booster driven dual-loop system are 8.54 kW and 44.44%, respectively. The maximum average heat transfer rate and temperature effectiveness of the pump/booster/booster driven triple-loop system are 7.90 kW and 41.5%, respectively. Throughout the year, the best coupling scheme of the dual-loop system is the pump/booster driven dual-loop system, and its average heat transfer rate and temperature effectiveness are 6.755 kW and 45.85%, respectively. The best coupling scheme of the triple-loop system is the pump/booster/booster-driven triple-loop system, and its average heat transfer rate and temperature effectiveness are 6.315 kW and 43.25%, respectively.

A Gray-Box Surrogate Vehicle Energy Consumption Model Capable of Real-Time Updating

Vehicle energy consumption model, as a function of its operational environment, plays a significant role in real-time optimization of vehicle route and speed for a given pair of origin and destination with a desired arrival time for minimal energy consumption. In this article, a gray-box vehicle energy consumption model is developed based on a high-fidelity vehicle dynamic model with environmental influence based on the kriging modeling method, which includes rolling resistance, aerodynamics, gravity, and energy consumption of air conditioning and heater (HVAC), along with environmental conditions, such as temperature, wind speed, etc. The data-driven model, trained based on Gaussian process assumption, ensures the accuracy of the resulting model with a modeling error below 2.5%. The real-time model updating is based on recursive least-squares optimization using current driving data so that the model used for route and speed optimization represents the current vehicle status. The proposed gray-box model is validated in computer-in-the-loop simulations using SUMO and MATLAB with less than 2% error of energy consumption, which is a significant improvement over the vehicle dynamic model with up to 35% error in certain cases. A case study also indicates energy consumption reduction for vehicle route-speed optimization.

New Evacuated Tube Solar Collector with Parabolic Trough Collector and Helical Coil Heat Exchanger for Usage in Domestic Water Heating

Buildings represent approximately two-thirds of the overall energy needs, mainly due to the growing energy consumption of air conditioning and water heating loads. Hence, it is necessary to minimize energy usage in buildings. Numerous research studies have been carried out on evacuated tube solar collectors, but to our knowledge, no previous study has mentioned the combination of an evacuated tube solar collector with a parabolic trough collector and a helical coil heat exchanger. The objective of this paper is to evaluate the thermal behavior of an innovative evacuated tube solar collector (ETSC) incorporated with a helical coil heat exchanger and equipped with a parabolic trough collector (PTC) used as a domestic water heater. To design the parabolic solar collector, the Parabola Calculator 2.0 software was used, and the Soltrace software was used to determine the optical behavior of a PTC. Moreover, an analytical model was created in order to enhance the performance of the new model of an ETSC by studying the impact of geometric design and functional parameters on the collector’s effectiveness. An assessment of the thermal behavior of the new ETSC was performed. Thus, the proposed analytical model gives the possibility of optimizing ETSCs used as domestic water heaters with lower computational costs. Furthermore, the optimum operational and geometrical parameters of the new ETSC base-helical tube heat exchanger include a higher thermal efficiency of 72%. This finding highlights the potential of the heat exchanger as an excellent component that can be incorporated into ETSCs.

Case Study: Impacts of Air-Conditioner Air Supply Strategy on Thermal Environment and Energy Consumption in Offices Using BES-CFD Co-Simulation.

Due to energy constraints and people's increasing requirements for indoor thermal comfort, improving energy efficiency while ensuring thermal comfort has become the focus of research in the design and operation of HVAC systems. This study took office rooms with few people occupying them in Wuhan as the research object. The EnergyPlus-Fluent co-simulation method was used to study the impact of 12 forms of air distribution on the thermal environment and air-conditioner energy consumption. The results indicate that 3 m/s supply air velocity and 45° supply air angle are more suitable for the case model in this study. The EnergyPlus-Fluent co-simulation method used in this paper provides a reference for the study of indoor environments in offices with few people occupying them.

Improving the performance of indirect evaporative cooler for energy recovery from the perspective of nozzle configuration: A CFD model analysis

As a sustainable cooling technology, indirect evaporative cooling (IEC) has been widely recognized as an effective means of achieving carbon neutrality based on its low energy consumption and high efficiency in central air conditioning (AC) systems of buildings. In contrast to the conventional arrangement, IECs as heat recovery units are often arranged in a diamond shape inside the air handling units (AHUs) of data centers (DCs), an approach that facilitates the flexible use of space and integration within the units in a more compact form. The use of CFD simulations allows an integrated analysis of the coupling of hydrodynamic, thermal and mass properties helps to improve the evaporation performance of IECs. In this study, a 3D simulation model of a diamond-shaped IEC containing the water spray system was developed to compare and analyze the air-water arrangement options in IEC systems currently used in DCs, and the corresponding characteristics are explored from the perspective of CFD techniques to determine the effect of nozzle configurations on the formation and evaporation of water film within the wet channels. Then, parametric analysis of nozzle setup schemes based on performance metrics showed that the nozzle arranged in top-side configuration and paired with the air-water counterflow form had the best performance, with 59.2% and 27.4% improvement in water film coverage area and temperature drop, respectively, over the worst scheme (bottom configuration) at a water supply flow rate of 65 L/s. Finally, the effectiveness of the enhanced approach was simulated and analyzed for hydrophilic and fiber coatings, and it was found that the water film coverage increased by 14.5% and 31.6%, respectively, while the coefficient of performance (COP) increased by 7.4% and 16.1%.

Experimental evaluation of split air conditioning performance using nanodiamonds particles in compressor polyester lubricant oil

Rationing energy consumption in air conditioning (AC) systems has become increasingly necessary due to the continuous global increase in energy demand and the prevailing sustainability vision worldwide. Therefore, an AC system utilizing nanodiamond/Polyester (ND/POE) lubricant oil, which shows potential to improve the performance and reduce energy consumption, was investigated. Consequently, a 5-ton refrigeration split AC unit was modified with an oil separator to assess the ND/POE nanolubricant in the compressor’s loop, in particularly. The AC unit was examined under various operating conditions up to an extreme high ambient temperature of 52˚C, with an optimal nanolubricant concentration of 0.1% as recommended from the literature, using a fully automated psychrometric testing facility. The results showed that using ND/POE instead of pure POE resulted in a 4.7% and 3% reduction in compressor discharge temperature and pressure, respectively. Furthermore, the overall system's coefficient of performance (COP) improved by up to 8% due to a reduction in power consumption of up to 3% and an increase in cooling capacity of up to 6%. Therefore, it is anticipated that the use of ND/POE will result in improved compressor durability, reliability, and longevity, as well as a significant improvement in the performance of AC systems operating for prolonged periods, such as those operating in extreme high ambient temperature applications.

Research on the influence of soak in the cold environment on the energy consumption of electric vehicles

The discharge mode has a great influence on the energy consumption of electric vehicles, especially at cold environment, soak in cold environment will lead to the decrease of the temperature of the vehicle/battery, resulting in the increase of energy consumption. In this paper, a segmented driving energy consumption test method was designed according to the real road discharge low of private vehicle, and the continuous and segmented energy consumption tests were carried out on the laboratory drum under −10 °C. From the perspective of energy flow, the differences of driving energy consumption, air conditioner energy consumption and brake energy recovery under the two test methods are analyzed. Results shown that soak in cold environment will cause the energy consumption of driving and air conditioner to increase by 5.5% and 43.8%, respectively, and also lead to a 17.1% decrease in brake recovery energy.

Radiation Effect on Heat Transfer in Narrow Cavities

The thermal comfort and air-conditioning energy consumption of vehicles or trains are dependent on the thermal resistance of its envelopes, which could be enhanced by improving the radiation characteristics of the narrow cavities scattered in their envelopes. However, the study for a feasible method and its effectiveness has been given little attention. This paper introduces a method that involves pasting aluminum foil on the inner wall to change the radiation characteristics of the narrow cavity and analyzed its effects on narrow-cavity heat transfer by experimental and numerical methods. The results indicate that the radiation effect on heat transfer in a narrow cavity made of conventional material is dominant, with a rate larger than 75%, and that pasting aluminum foil is an effective and feasible method of weakening the radiation rate in narrow-cavity heat transfer, decreasing it to less than 10%. This paper will provide a reference to improve the insulation characteristics of vehicle enclosure.