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In buildings, air conditioning and mechanical ventilation (ACMV) systems are the major shareholders of overall energy consumption. Energy-efficient designs for ACMV systems in building applications are therefore needed. While designing an efficient ACMV system, consideration must be given to the growing concerns of enhanced thermal comfort and improved indoor air quality. The variable refrigerant flow (VRF) air-conditioning system is a widely adopted alternative to the existing building cooling systems due to the higher energy efficiency and individualized temperature control feature. However, it still suffers from shortcomings such as no outdoor air induction for ventilation and higher initial cost. Therefore, this paper reviewed the variable refrigerant flow and mechanical ventilation/air distribution systems, their integrated designs for non-residential buildings, performance evaluation and control optimization of the integrated systems, VRF systems' faults detection and diagnosis, current application of the VRF systems, and associated challenges. Together with these all, some advanced buildings' cooling techniques and improvements toward nearly/net-zero energy buildings are briefly discussed. Indoor thermal comfort models and criteria for different climates are also presented for an in-depth understanding of the VRF integrated mechanical ventilation designs. The literature survey shows that the supply air temperature and airflow rate are foremost in parameters that can be optimized in VRF integrated ventilation design as they greatly reduce the energy consumption. Further, policies on elevated indoor temperatures in air-conditioned buildings to mitigate their carbon footprint are strictly being implemented. Therefore, this review provides an insight to the researchers for further improvement in the integrated design and control optimization of the parameters involved. A paradigm shifts from the conventional compression-based electric-powered air conditioning systems to the renewable energy driven advanced air conditioning technologies which is also an emerging research area to be focused on achieving the target of nearly/net-zero energy buildings. [ABSTRACT FROM AUTHOR]

Low global warming potential hydrofluoroolefin-1234yf (R1234yf) is an alternative green refrigerant for the automotive air conditioning (AAC) system to replace the existing R134a refrigerant. However, the low energy efficiency of the AAC system using R1234yf has been a significant obstacle to its wider use. This paper describes using Al2O3–SiO2/DEC PAG nanolubricant to enhance the performance of the AAC-R1234yf system. The hybrid nanolubricant was created by a two-step preparation process. The experiment was undertaken at volume concentrations up to 0.05% and under various operating conditions. The stability test shows that the hybrid nanolubricant remained in superior stability after 6 months, with minimum particle aggregation and sedimentation. The AAC-Al2O3–SiO2/DEC PAG system achieved the best performance at 0.03% volume concentration with an average increment of 12.01%. This outcome was contributed by the increase of the AAC evaporator's heat absorb value by 2.8% and the reduction of the compressor work with an average decrease of 7.7%. In conclusion, a 0.03% volume concentration of Al2O3–SiO2/DEC PAG nanolubricant in the AAC compressor was recommended for optimum system performance and energy saving. [ABSTRACT FROM AUTHOR]

Over the past three years, regulations have been implemented to combine natural ventilation (NV) and air conditioning to mitigate the risk of disease transmission, particularly in response to the COVID-19 outbreak. As we know, simultaneous use of NV and air conditioning can make it challenging to achieve indoor thermal comfort. This paper aims to analyze the effect of NV on the air conditioning's cooling and heating load in a classroom through simulation. A simulation model was developed using EnergyPlus software with an OpenStudio interface software. Simulation results demonstrate that continuous use of NV alongside an air conditioner increases the cooling load from 1.06 to 1.75 times during summer and a 1.54 to 9.49 times heating load increase during winter. On the other hand, intermittent NV every hour results in a cooling load increase from 1.05 to 1.46 times in summer and a heating load increase from 1.13 to 4.63 times in winter. Moreover, employing NV based on the outside air temperature can reduce the cooling load at the air conditioner with set-point 26℃—28℃ from 0.94 to 0.88 times. The outcomes of this study are expected to serve as a reference for determining strategies that effectively combine NV and air conditioning to meet various needs without causing a significant increase in energy consumption. Additionally, the results are expected to be useful for reducing AC energy consumption in extremely hot and cold weather with some strategies of NV application. [ABSTRACT FROM AUTHOR]

In hot and humid areas with high solar radiation intensity, the use of air conditioning systems on the basis of desiccant materials such as solar desiccant cooling systems with a view to reducing energy consumption and economic saving can be a good alternative to conventional air conditioning units. In this paper, in order to offer a cooling load of a sample space in the city of Bandar Abbas, which has a high latent load and high radiation intensity, solar absorption cooling cycle has been considered as the base cycle, and two absorption cooling cycles were designed for comparison. Then the three cycles were modeled in the TRNSYS software, studied technically and economically, and at the end the best cycle has been selected. In terms of current energy prices, application of solar energy in Iran is not economically feasible, so the solar absorption refrigeration cycle has been considered as the basic system for the cycle's comparison. Modeling of the expressed cycles was done in TRNSYS software. The basic cycle has been composed of two main parts of cooling by absorption chillers and providing the required heat supply by the solar collector, and also two desiccant dehumidification cycles have been added by a desiccant dehumidification system. In the economic analysis of the three systems, the costs estimation during lifetime (LCC) method also has been used. As a result of this modeling and due to the Act to amend energy prices, the cooling system with the help of desiccant wheel and using returned water of chiller's generator as the regeneration source, with an annual energy saving of about 29.1%, 29.1% (1,371,980 m3) of natural gas consumption has been saved and the amount of 18/15% (156,667$) cost savings over 20 years compared to the base period, has been selected as the most efficient cooling system. [ABSTRACT FROM AUTHOR]

In this paper, we forecast residential electricity consumption in Brazil considering the variability in consumption behavior in different regions. In order to do so, we use a bottom-up approach to estimate long-term electricity consumption that considers three technology-driven scenarios: one assuming reference efficiency development, another one based on the Brazilian government's predictions, and the third one assuming high efficiency. The results show an increase of residential electricity consumption due to the increasing appliance ownership rate, especially air conditioning, as well as the increasing number of households. In addition, it is shown that 96 TWh of electricity could be saved in the highest efficiency scenario due to significant efficiency gains between 2016 and 2050. Further, the results indicate the southeast of the country has the highest potential for consumption reduction: by 27% in the most efficient scenario. This work is the first to use a bottom-up approach to forecast the residential electricity consumption by region and by technology-driven scenarios in Brazil. With this methodology, it is possible to indicate which types of appliances should be targeted by policy makers when designing energy efficiency incentives. Hence, this model can be used as a roadmap to achieve the desired efficiency gains in Brazil. [ABSTRACT FROM AUTHOR]

Heating and cooling energy consumption of buildings accounts for a large portion of global energy use and is significantly affected by the air conditioning system in the buildings. In order to predict the energy performance of buildings, various energy simulation engines have been developed and recently applied to the BIM data of buildings. However, due to the interoperability between them, estimating heating and cooling energy at the design stage of the air conditioning system, in collaboration with the building model, still lacks of efficiency and accuracy. In this paper a highly efficient design framework with enhancement of interoperability that enables the designing of a variable refrigerant flow (VRF) type air conditioning system in BIM environments and to analyze its energy behavior is proposed. The framework covers i) computing the energy load of a building, ii) designing a VRF system that includes equipment selection, layout and piping, and iii) predicting energy consumption by the system with consideration of the building's thermal properties and annual weather conditions. The novelty of the proposed approach lies in the fact that the layout and piping for air conditioning system are enabled inside a BIM environment to maximize interoperability. We implemented the framework as an add-in program to the commercial BIM software and present its accuracy in comparison with the reference data provided by ASHARE. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of a three-dimensional (3D) air-conditioning (AC) system on cabin thermal comfort. Current AC systems are dependent on the cooling performance of Heating, Ventilation, and Air-Conditioning (HVAC) systems located inside the front instrument panel and supplying cold air from the front to the rear cabin. This results in a difference in perceived thermal comfort between the front and back seats due to a number of factors, including solar radiation through the windows, blower air path, and individual environmental differences. The 3D AC system was designed to improve the thermal comfort of passengers. In order to simulate the 3D AC system, an auxiliary blower was adapted for rear passengers. A cooling performance test and thermal comfort evaluation were conducted, with the blower at various positions in the cabin. According to the experiment results, four positions of the auxiliary blower showed cooling comfort ratings similar to those of the current HVAC system environment, and the thermal comfort ratings in the 3D AC experiment showed improvement. In other words, 3D AC system can reduce energy consumption, because it can reach the set temperature with less AC system operation. [ABSTRACT FROM AUTHOR]

To meet the demand of improved comfort for passengers, drive ability and standard in fuel economy; external variable displacement swash (wobble) plate type compressors are used in automobile air conditioning control system because of their low energy consumption and highly efficient characteristics. It controls the compressor displacement by increasing or reducing the swash plate angle. Solenoid operated electromagnetic control valve (ECV) in the compressor controls the air conditioning system by means of a pulse width modulation (PWM) input signal supplied from an external source (controller). The mechanism changes the swash plate angle by increasing or reducing the pressure of swash plate chamber using the ECV functions. The force (solenoid) for ECV operation is important as the force directly related to the movement of the internal feature i.e. mainly plunger of the ECV which is responsible for the amount of air/refrigerant flow that results the air conditioning control procedures with various pressure ports. The research paper highlights the improved theory and equation for calculating the working force (solenoid force) in ECV and experimental analysis of 3 (three) ECV samples followed by the comparison of theoretical and experimental force results. [ABSTRACT FROM AUTHOR]

The development of climate-friendly technologies and its diffusion across countries is of key importance to slow climate change. This paper considers technologies in the mobile air-conditioning (MAC) sector which is a major contributor of fluorinated greenhouse gas emissions. Using patents as an indicator of innovations and patent citations as a proxy for knowledge flows, the inducement of new environmental and non-environmental technologies and knowledge diffusion within and across countries are analysed. The focus is on direct abatement of fluorinated greenhouse gases excluding energy efficiency improvements. We find that most environmental MAC patents originate from the US and Germany. Most knowledge flows take place within countries. Regarding cross-country flows most environmental knowledge diffuses from French and German patents, which is likely to be a result of regulatory activities in Europe and intensified research on environmentally benign MAC systems. Yet, this exchange of knowledge is not very intensive and stable so that the impact of EU regulations on US and Japanese patenting behaviour seems to be fairly weak. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and analytical study on the inverter split-type air-conditioner for the purpose of energy saving and a proper balance between sensible and latent capacity. Performance of an inverter split-type air-conditioner is investigated at varied refrigerant mass flow rates, air volume flow rates, and set point temperatures. The performance investigated for a 2.54-kW inverter split-type air-conditioner includes cooling capacity, power consumption, the value of coefficient of performance (COP), and equipment sensible heat ratio (SHR). An increase of electrical frequency input to compressor from 34 to 66 Hz results in an increase of cooling capacity by 0.88 kW, a decrease of COP by 0.84, and a decrease of SHR by 0.11. An increase in cooling coil flow rate from 4.14 to 8.2 m3/min results in an increase in cooling capacity by 0.16 kW, an increase in COP by 0.10, and an increase in SHR by 0.15. An increase of set point temperature from 24 to 26°C results in an increase of the value of COP by 0.13 and a decrease of SHR by 0.03. The study offers guidelines for the application of small-size inverter split-type air-conditioners in hot and humid climates. [ABSTRACT FROM AUTHOR]

The major focus of this work is on the impact of both the temperature and humidity variations on the air conditioning load model characteristics based on field measurements. A typical residential house was used for experimental investigation and data collection for the segregated residential air conditioner load. Important field data has been collected for several hot and humid consecutive months covering a wide range of outdoor temperatures and humidity. The Simulated Annealing (SA) method based on the Monte Carlo technique for finding solutions to optimization problems was used for data analysis and model shaping. The SA algorithm has been implemented to find the best model for the AC load by finding the optimal estimates of the proposed AC load model parameters. The mathematical model developed in this paper was successful in reproducing the experimental testing data with a very good degree of accuracy. The model reached was found to adequately represent the effect of humidity and temperature on the AC load. The nonlinear relationship between humidity, temperature, and real power demand is consistent through all temperature and humidity ranges. [ABSTRACT FROM AUTHOR]