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This paper analysis the operational electricity consumption of 2 office buildings in campus with VRF and centralized air conditioning system respectively, according to the monitoring data derived from a building energy monitoring and management system. Results show that both two air conditioning systems have great potential for energy saving, and t...
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... SRC is a more quantitative method for measuring sensitivity, while PCC can be used in SA based on correlations between the data [101]. PCCs are used to indicate a pure correlation between the independent variable and the dependent variable [102]. A PCC greater than 0.5 indicates a linear correlation. ...
Variable Refrigerant Flow (VRF) systems are becoming increasingly popular in commercial and residential buildings due to their flexibility and efficiency. Building design and operational parameters play an important role in the process of predicting cooling loads, and these variables contain a variety of uncertainties that must be taken into account when seeking to obtain a reliable prediction. It is common practice to oversize the Heating, Ventilation, and Air Conditioning (HVAC) system installed in a building in order to reduce uncertainties in its performance. However, oversizing is undesirable due to additional capital and operating costs, inefficient space utilization, and excessive emissions of greenhouse gases. This study provided a comprehensive literature review on previous uncertainly analysis studies from six perspectives: classification of uncertainty factors, sensitivity analysis methods, building energy model for uncertainty analysis, sampling method, the most effective parameter , and distribution of uncertainty parameters., and then developed a framework to investigate the effects of uncertainty of operational and design parameters on annual cooling load, total energy consumption, HVAC electricity use per conditioned floor area, VRF system cost, and the cooling-to-total electricity consumption ratio (R) in residential buildings equipped with VRF systems located in the Middle East (ME) region (Kuwait City, Tehran, and Istanbul). Artificial Neural Network (ANN) model was also developed to predict output parameters in residential building. Latin Hypercube Sampling (LHS) simulation was also applied to generate near-random samples of uncertainty parameter values from a multidimensional distribution. It should be mentioned that a correlation was derived in this study to predict VRF cost. The study evaluated thirteen uncertainty parameters related to building characteristics, occupants, building energy systems, VRF variables, and lighting conditions. Several methods were used to evaluate the effects of input uncertainty parameters on the output variables, namely, the Standardized Regression Coefficient (SRC), Partial Correlation Coefficient (PCC), and Spearman Rank Correlation Coefficient (SRCC) or Pearson Product-Moment Correlation Coefficient (PPMCC). The results indicated that VRF cost and HVAC electricity use per area have a greater coefficient of variation compared with other output parameters. The density distribution of output parameters indicated that uncertainty parameters had the greatest impact on output parameters in Kuwait (hyper arid climate), whereas in Istanbul (humid subtropical climate), they were the least. Among the variables examined in the Sensitivity Analysis (SA), cooling setpoint had the greatest impact on residential building energy consumption in ME climates. Finally, this paper highlights emerging trends and offers recommendations for advancing future research in the realm of building energy uncertainty analysis.
... A performance of ACS is characterized by off-design modes which are especially evident in temperate climatic conditions and off-season operation. Therefore, the VRF systems are the most well adapted to cover efficient off-season operation [51,52]. ...
Outdoor air conditioning systems (ACS) are used as autonomic systems as well as in combined outdoor and indoor ACS of the variable refrigerant flow (VRF) type, with variable speed compressors (VSC) as their advanced version. Methods for determining the optimal value of refrigeration capacity and providing the maximum rate of the summarized annual refrigeration energy generation increment, according to its needs at minimum compressor sizes and rational values, are applied to reveal the reserves for reducing the designed (installed) refrigeration capacity, thus enabling us to practically achieve maximum annual refrigeration energy generation as the primary criterion at the second stage of the general design methodology previously developed by the authors. The principle of sharing the total thermal load on the ACS between the ranges of changeable loads for outdoor air precooling, and a relatively stable load range for further processing air are used as its basis. According to this principle, the changeable thermal load range is chosen as the object for energy saving by recuperating the excessive refrigeration generated at lowered loading in order to compensate for the increased loads, thereby matching actual duties at a reduced designed refrigeration capacity. The method allows us to determine the corresponding level of regulated loads (LRL) of SRC and the load range of compressor operation to minimize sizes.
... The VRF systems are considered the most efficient for off-season operation [65,66]. Their combined version includes two subsystems for outdoor and indoor air processing [67,68]. ...
This paper focuses on the application of speed-regulated compressors (SRCs) to cover changeable heat loads with high efficiency in conventional air conditioning systems (ACS) as well as in the more advanced variable refrigerant flow (VRF)-type outdoor and indoor ACS. In reality, an SRC is an oversized compressor, although it can operate efficiently at part loads. The higher the level of regulated loads (LRL) of the SRC, the more the compressor is oversized. It is preferable to reduce the size of the SRC by covering the peak loads and recouping the excessive refrigeration energy reserved at decreased actual loads within the range of regulated loads. Therefore, the range of changeable loads is chosen as the object to be narrowed by using the reserved refrigeration capacity. Thus, the general fundamental approach of dividing the overall heat load range of the ACS into the ranges with changeable and unchangeable loads, as previously developed by the authors, is applied for the range of primary changeable loads. Due to this innovative step, the principle of two-stage outdoor air conditioning according to changeable and unchangeable loads, also proposed by the authors, has been extended over the range of primary changeable loads to reduce the level of refrigeration capacity regulation and SRC size. To realize this, part of the changeable load range is offset by the reserved refrigeration capacity, leading to a reduction in the changeable load range and the SRC size by approximately 20% for temperate climatic conditions.
... Numerous investigations are aimed to improve the operation efficiency of variable refrigerant flow (VRF) systems [50,51]. The VRF systems provide energy saving above 20% compared to variable air volume systems [52,53]. ...
... None of the above criteria [48,51,53,54,56,57,74] can assess actual loading of the range outside the load regulation, whereas the lack of load indicates a reduction in the performance efficiency of SRC. ...
... The ambient ACS as an autonomous system, the main subsystem of combined outdoor and indoor ACS of the VRF type [48,51,53,54,56,57,70,71], and the ranges of changeable and unchangeable thermal loads are accepted as the objects of investigation. ...
All the energetic management and controlling strategies in ambient air conditioning systems (ACS) are aimed to match design load to current needs. This might be achieved by determining a rational value of design thermal load without overestimation that can minimize its deviation from the actual values. The application of variable refrigerant flow (VRF) systems with speed-regulated compressors (SRC) is considered as the most advanced trend in building air conditioning due to the ability of SRCs to cover changeable heat loads without lowering their efficiency. The level of load regulation by SRC is evaluated as the ratio of the load range, regulated by SCR, to the overall design load range. With this, the range of actual changeable loads is usually supposed to be covered by SRC entirely while keeping the rest, unregulated, and load range unchangeable. However, to confirm this, the rest load range behind the regulated one should be investigated to estimate the efficiency of SRC operation. Therefore, the approach to dividing the overall thermal load range of ambient air conditioning into the ranges of changeable and unchangeable loads to compare with those covered by SRC is used. From this approach, the method of rational designing and shearing a design refrigeration capacity in response to current loading, based on the principle of two-stage ambient air conditioning, has been widened on the VRF systems to estimate the efficiency of SCR application. This was realized by imposing the load ranges regulated by SRC onto the ranges of changeable and unchangeable loads within the overall range of actual loading. The proposed innovative criteria and indicators for rational shearing the load ranges to match current duties and load level evaluation can reveal the reserves for improving the efficiency of SRC compressor operation and the ACS of VRF type as a whole.
... The lowest monthly consumption cost is the best option on selecting the lighting system, motor controller and air-condition units controller for the project. The elements with the lowest costs will be LED lighting system (case no.3) (Siddiqui & Soleja, 2017), motor loads with VFD controller (case no.3) (Lozanov et al., 2019) and VRF type air conditioning units (case no.3) (Liu et al., 2015). The environmental impact of electricity generation is becoming more critical as electricity consumption continues to increase, one of the products produced by the system is called Greenhouse Gas (GHG), the lower the GHG value the lower the risk in the environment. ...
The impact of having an energy efficient electrical system in a 30 MLD wastewater treatment plant (WWTP) is examined in this study. A WWTP also known as Sewage Treatment Plant (STP) treats wastewater from residential, commercial and industrial consumers and converts it into reusable and safe water. The purpose of this study is to identify the parameters that influence the electrical system's performance when energy-saving strategies are used. The design invoked in this plant uses several Energy Efficient Configurations using the following ElectroMechanical intermediation; Variable Frequency Drive (VFD) Motors, Variable Refrigerant Flow (VRF) on Air Conditioning units, LED Lighting System, Solar-powered Perimeter Lighting (independent). This paper highlights three different design cases. Case 1: No Automatic Power Factor Correction (APFC), No Solar (Standard Electrical System), Case 2: With APFC, no solar and Case 3: With APFC, With Solar (Energy Efficient Electrical System). Comparisons are shown based on each design's cost and kWh savings, as well as an analysis of the many implications of the technology/strategy in the system, such as illumination and total harmonic distortion. At its core, energy efficiency refers to a method of minimizing energy consumption by using less energy to achieve the same amount of useable power.
Link: https://iiee.org.ph:89/uploads/files/1431.pdf
... When the heating water is closed, the wireless household on-off solenoid valve activates the automatic protection function, and automatically opens the heating water according to the temperature to ensure the normal heating of the user. The temperature data reported by the wireless temperature sensor is first stored on the relay module, and then the temperature data is reported to the database server through the gateway according to the patrol instruction of the central monitoring system [14]. The wireless household on-off solenoid valve control is used in conjunction with the wireless temperature sensor, and the point-to-point binding is realized by setting on the central control system. ...
Current centralized heating monitoring system has realized the collection and control of working condition data in heating power stations, but there are still some shortcomings, such as the inability to collect data on the working conditions of user sides, and the inability to meet the further demand of heating enterprises for the refinement of heating network monitoring data. A wireless sensor network is a fully distributed sensor system with no central node, which can intensively deploy many sensor nodes to monitoring area through random placement, and integrates sensors, data processing and communication modules to form a self-organized network system. Therefore, in order to realize the intelligence of heating system and improve the flexibility of node data collection, the monitoring system can use wireless sensor network technology to realize wireless collection of node data, and display the collected data on a man-machine interface in real time. On the basis of research results from previous scholars, this paper expounds the research status and significance of centralized heating monitoring system design, elaborates the development background, current status and future challenges of wireless sensor network technology, introduces the methods and principles of wireless network communication protocol and heating and heat balance flow analysis, proposes a structural model of a centralized heating monitoring system based on wireless sensor networks, carries out the design of perception and convergence nodes, analyzes the layout of wireless sensor networks, explores the design scheme of centralized heating monitoring system based on wireless sensor networks, conducts the hardware and software design of the monitoring system, implements the software testing and hardware debugging of the centralized heating monitoring system, and finally discusses the relationship between data transfer related tasks and task scheduling. The study results show that the application of the centralized heating monitoring system based on the wireless sensor networks can not only more conveniently monitor, control and manage the entire heating networks, but also make full use of the centralized monitoring and quantitative management functions of the wireless sensor networks. This achieves dynamic tracking and monitoring of heating operation, real-time diagnosis of hidden dangers in heating operation, and safe, normal and energy-saving operation of the centralized heating system. The study results of this paper provide a reference for further researches on the design of centralized heating monitoring system based on wireless sensor networks.
... In recent years, the electricity consumption in public buildings has accounted for a large proportion of the global energy consumption (Pérez-Lombard et al. 2008;Ma et al. 2017). Heating, ventilation, and air-conditioning (HVAC) systems consume up to 80% of the energy used in public buildings, and the use of central air-conditioning (AC) systems, which are the most common thermal comfort adjustment equipment in public buildings, is responsible for a large proportion of the total building energy consumption (Liu et al. 2015). Because of its use of energy-intensive equipment such as pumps and chillers, the water system of a central AC system accounts for a large fraction of the energy consumption. ...
Central air-conditioning systems predominantly operate under partial load conditions. The optimization of a differential pressure setpoint in the chilled water system of a central air-conditioning system leads to a more energy-efficient operation. Determining the differential pressure adjustment value based on the terminal user’s real-time demand is one of the critical issues to be addressed during the optimal control process. Furthermore, the online application of the differential pressure setpoint optimization method needs to be considered, along with the stability of the system. This paper proposes a variable differential pressure reset method with an adaptive adjustment algorithm based on the Mamdani fuzzy model. The proposed method was compared with differential pressure reset methods with reference to the chilled water differential temperature, outdoor temperature, and linear model based on the adjustment algorithm. The energy-saving potential, temperature control effect, and avoidance of the most unfavorable thermodynamic loop effects of the four methods were investigated experimentally. The results indicated that, while satisfying the terminal user’s energy supply demand and ensuring the avoidance of the most unfavorable thermodynamic loop, the proposed adaptive adjustment algorithm also decreased the differential pressure setpoint value by 25.1%–59.1% and achieved energy savings of 10.6%–45.0%. By monitoring the valve position and supply air temperature of each terminal user, the proposed method exhibited suitable online adaptability and could be flexibly applied to buildings with random load changes.
... Basically, a VRF is a system that adjusts the flow of refrigerant to each indoor evaporator continually, with the help of a variable speed compressor and electronic expansion valves located in each internal unit (Alahmer & Alsaqoor, 2018). Nowadays, this type of system has been calling more attention, due to its efficient operation and improvement of the thermal comfort of the environments (Liu et al., 2015). The major energy saving of VRF systems comes from the following factors: (i) the use of variable speed air cooled compressors; (ii) the elimination of ductwork; (iii) the use of refrigerant instead of water, which requires less energy to transfer the fluids heat; and finally, (v) the use of outside air systems with energy recovery (Alahmer & Alsaqoor, 2018). ...
The aim of this study is to quantify the energy savings of a library in the city of Foz do Iguaçu/Brazil, through simulations in EnergyPlus. Due to the great participation of air conditioning in the electric consumption of the building under study, the following proposals were studied: the exchange of the current split air conditioning units by a Variable Refrigerant Flow (VRF) system; the application of solar control films on the glasses; and both options together. The methodology followed these steps: firstly, it was simulated the current electricity consumption and the results were validated with real measures; secondly, the retrofitting measures were sized and implemented in the program and the energy savings were quantified; finally, an economic analysis was performed in order to determine the feasibility of the proposals. As a result, the VRF system showed an annual saving in air-conditioning of 42.08% related to the mini-split system. The annual electricity savings were 32.01, 2.14 and 32.80% for the VRF, solar control films, and both options together, respectively. The feasibility analysis of the VRF, considering financing and for a scenario consistent with the historical average growth of the electricity prices and inflation rate, showed that the use of a VRF instead of the splits units recovers the initial investment in 14 years. The application of solar control films proved to be economically unfeasible.
... Besides, Liu [12] analyzed the operational electricity consumption between the VRF system with the centralized airconditioning system in the two office buildings at the campus based on the monitoring data obtained from a building energy monitoring and management system. From this research, the rate of electricity consumption obtained was 0.48 kWh/m 2 for the VRF system and 0.42 kWh/m 2 for the centralized airconditioning system, which can be concluded that both systems have a great potential in energy savings. ...
... From this research, the rate of electricity consumption obtained was 0.48 kWh/m 2 for the VRF system and 0.42 kWh/m 2 for the centralized airconditioning system, which can be concluded that both systems have a great potential in energy savings. However, the electricity consumption of the VRF system is better than the centralized air -conditioning system due to the flexible adjustability of the VRF system [12]. However, the main disadvantage of the VRF system is the cost [1,13,14]. ...
The usage of air - conditioning in the residential and commercial buildings is becoming necessary because of the enormous demand for thermal comfort and healthy indoor environment. In achieving human thermal comfort and healthy indoor environment in a large building, there are many types of air conditioning systems that can be used, including the multi - split type unit and the variable refrigerant flow (VRF) system. The present research analyses the annual energy use of the existing ACMV system (multi - split type ceiling cassette unit) installed in the examined building, which located in the tropical area and compares it with a VRF system. The TRNSYS software is used to simulate both of these systems in accordance with the existing building’s characteristics and its operation. The existing building’s characteristics and its operation are obtained by conducting the site survey and field measurements in the building. In the current paper, the bin method is used to estimate the annual energy consumption for these systems. Based on the simulation results, the existing ACMV system consumes more energy in comparison to the VRF system by 13.62%. In addition, the annual operating cost of these systems has shown that the VRF system has a lower annual operating cost in comparison to the existing ACMV system by 13.63%. Besides that, the VRF system can accommodate an estimated payback period of around 6.6 years and an internal rate of return of 12.75%. The result has suggested that the VRF system has a great potential in energy savings and could reduce the electricity consumption in a large building significantly.
... Various studies have been made on these non-water-based systems to make them suitable on different scales, thus, replacing those traditional chiller systems being practiced for the previous decades. Liu et al. analyzed electricity consumption of VRF systems with centralized models based on building energy management and regulating approach [9]. Further researches also carried out that kept digging more towards advancements in VRF akin to HVAC industry [10][11][12][13]. ...
Affordable energy plays a key role in economic growth but the rate at which energy is being utilized in buildings has disturbed the whole world in various ways. The traditional HVAC systems installed in commercial & residential buildings with their several subunits consume energy in a huge amount. Thus, the optimization of energy usage in conventional HVAC applications is essential in terms of both technical & economic perspectives. In this paper, Variable Refrigerant Flow (VRF) solution has been proposed by developing a simulated model to cut both the total cost & energy consumption for a complex structured auditorium building with a total covered area of 7012m 2. Actual data measured from the centralized chiller equipment already installed in the building is compared with the modelled VRF's data in terms of electricity consumption, operational, owning & maintenance costs. Considering the local climatic conditions of the region, the VRF system is more energy efficient and around 23% more profitable than conventional chiller system already installed in the chosen building, proving VRF technology to be the acme of comfort, offering more economical & high energy performance.
