Residential Air Conditioning Research Articles

Impact of Air Conditioning Type on Outdoor Ozone Intrusion into Homes in a Semi-Arid Climate

Outdoor ozone (O3) is elevated on hot, sunny days when residential air conditioning is used most. We evaluated the impact of direct evaporative coolers (ECs) and vapor-compression air conditioners (ACs) on indoor O3 concentrations in homes (N = 31) in Utah County, Utah, United States of America. Indoor and outdoor O3 concentrations were measured for 24 h at each home using nitrite-impregnated glass-fiber filters. AC homes (n = 16) provided a protective envelope from outdoor O3 pollution. Only one AC home had O3 levels above the limit of detection (LOD). Conversely, EC homes (n = 15) provided minimal protection from outdoor O3. Only one EC home had O3 levels below the LOD. The average indoor O3 concentration in EC homes was 23 ppb (95% CI 20, 25). The indoor-to-outdoor (I/O) ratio for O3 in EC homes was 0.65 (95% CI 0.58, 0.72), while the upper bound for the I/O ratio for AC homes was 0.13 (p < 0.001). Indoor exposure to O3 for residents in EC homes is approximately five times greater than for residents of AC homes. Although ECs offer energy and cost-saving advantages, public health awareness campaigns in O3-prone areas are needed, as well as research into O3 pollution controls for direct ECs such as activated carbon filtration.

Revealing spatial and temporal patterns of residential cooling in Southern California through combined estimates of AC ownership and use

Air conditioning (AC) is an important tool for combatting the adverse health effects of heat, but its use can also drive surges of high demand for electricity. To better understand these effects, there is a need for non-intrusive methods of estimating AC access and operation. In this study, we use a novel methodology to identify residential AC ownership rates using smart meter data from 200,000 customers in Southern California, and find that 79 % of all customers in the region have AC. In contrast to previous methods, we classify AC ownership using hourly, rather than daily, electricity consumption records and directly account for the potential presence of electric heating. We then adapt and apply an algorithm to determine in which hours these households operate their AC. We estimate that the average customer runs their AC during 8.3 % of all hours in the two-year study period, but census-tract level averages range from 1 to 23 % of all hours. Lastly, we combine our estimates of AC ownership and use to analyze cooling behavior spatially and temporally, and are able to identify pockets of high cooling demand, areas lacking in access or the ability to use their AC, and potential targets for cooling-related DR programs.

REFRIGERANT CHARGING UNIT FOR THE RESIDENTIAL AIR CONDITIONERS: AN EXPERIMENT

In the present work, an automatic R410A refrigerant charger for residential air conditioners is fabricated and tested. The charger operates on the throttling principle and uses the suction pressure of the compressor to estimate the refrigerant charge level. This helps to reduce the risk of compressor damage and ensures the correct composition ratio of R410A refrigerant when charged into the machine. The charging process is controlled by the LabVIEW platform, which provides adequate control and visualization of the charging process. The developed charger meets expectations in solving the technical problems encountered when charging R410A refrigerant for residential air conditioners. It is compact, portable and can be directly controlled through the LabVIEW interface, allowing real-time visualization of the charging process. The present work is expected to make a significant practical contribution, serving as a useful reference for the future manufacturing of compact portable equipment in the residential air conditioning field.

Humidity-aware model predictive control for residential air conditioning: A field study

Model predictive control of residential air conditioning could reduce energy costs and greenhouse gas emissions while maintaining or improving occupants’ thermal comfort. However, most approaches to predictive air conditioning control either do not model indoor humidity or treat it as constant. This simplification stems from challenges with modeling indoor humidity dynamics, particularly the high-order, nonlinear equations that govern heat and mass transfer between the air conditioner’s evaporator coil and the indoor air. This paper develops a machine-learning approach to modeling indoor humidity dynamics that is suitable for real-world deployment at scale. This study then investigates the value of humidity modeling in four field tests of predictive control in an occupied house. The four field tests evaluate two different building models: One with constant humidity and one with time-varying humidity. Each modeling approach is tested in two different predictive controllers: One that focuses on reducing energy costs and one that focuses on constraining electric power below a utility-specified threshold. The two models lead to similar performance for reducing energy costs. Combining the results of this study and a prior heating study of the same house, the estimated year-round energy cost savings were $340–497 or 22%–31% (95% confidence intervals); these savings were consistent across both humidity models. However, in the demand response tests, the simplifying assumption of constant humidity led to far more frequent and severe violations of the power constraint.

Inequalities in global residential cooling energy use to 2050

Intersecting socio-demographic transformations and warming climates portend increasing worldwide heat exposures and health sequelae. Cooling adaptation via air conditioning (AC) is effective, but energy-intensive and constrained by household-level differences in income and adaptive capacity. Using statistical models trained on a large multi-country household survey dataset (n = 673,215), we project AC adoption and energy use to mid-century at fine spatial resolution worldwide. Globally, the share of households with residential AC could grow from 27% to 41% (range of scenarios assessed: 33-48%), implying up to a doubling of residential cooling electricity consumption, from 1220 to 1940 (scenarios range: 1590-2377) terawatt-hours yr.−1, emitting between 590 and 1,365 million tons of carbon dioxide equivalent (MtCO2e). AC access and utilization will remain highly unequal within and across countries and income groups, with significant regressive impacts. Up to 4 billion people may lack air-conditioning in 2050. Our global gridded projections facilitate incorporation of AC’s vulnerability, health, and decarbonization effects into integrated assessments of climate change.

Flexible emulation of the climate warming cooling feedback to globally assess the maladaptation implications of future air conditioning use

Abstract Rising affluence and a warming climate mean that the demand for air conditioning (AC) is rising rapidly, as society adapts to climate extremes. Here we present findings from a new methodological framework to flexibly couple and emulate these growing demands into a global integrated assessment model (IAM), subsequently representing the positive feedbacks between rising temperatures, growth in cooling demand, and carbon emissions. In assessing global and regional climate change impacts on cooling energy demand, the emulator incorporates climate model uncertainties and can explore behavioural and adaptation-related assumptions on setpoint temperature and access to cooling. It is also agnostic to the emissions and climate warming trajectory, enabling the IAM to run new policy-relevant scenarios (Current Policies, 2 °C and 1.5 °C) with climate impacts that do not follow Representative Concentration Pathways. We find that climate model uncertainty has a significant effect, more than doubling the increase in electricity demand, when comparing the 95th percentile cases to the median of the climate model ensemble. Residential AC cooling energy demands are expected to increase by 150% by 2050 whilst providing universal access to AC would result in the order of a 400% increase. Depending on the region, under current policies and limited mitigation, climate change could bring in the order of 10%–20% higher cooling-related electricity demands by 2050, and approximately 50% by 2100. Set point temperature has an important moderating role—increasing internal set-point from 23 °C to 26 °C, approximately halves the growth in electricity demand, for the majority of scenarios and regions. This effect is so strong that the change in set point temperature to both residential and commercial sectors outweighs the growth in demand that would occur by providing universal access to AC by 2050 to the 40% of the global population who would otherwise not afford it.

Pathways Toward Improving the Energy Efficiency of Residential Air-Conditioning Systems in Saudi Arabia

Abstract In Saudi Arabia, the residential electricity consumption approaches 50%, primarily driven by air conditioners (AC). This study explores the potential energy savings and carbon dioxide (CO2) emission reductions up to 2030 through three scenarios: business as usual (BAU), continuous improvement scenario (CIS), and accelerated improvement scenario (AIS). BAU scenario assumes that the current energy efficiency ratio (EER) of 11.8 BTU/Wh is maintained until 2030. CIS considers a 5% EER improvement in new AC stock every two or five years, while AIS assumes a 10% improvement in the EER at the same intervals. Additionally, energy savings and emission reductions possible from varying adoption levels of a new refrigerant (R32) are estimated for three scenarios. Finally, the CO2 emission reduction under each scenario is computed for two extreme cases of grid emission factor. BAU scenario predicts energy savings of up to 17.7 TWh in 2030 compared to 2020 energy consumption figures. AIS with two-year intervals results in additional energy savings of 10.1 TWh in 2030 and cumulative energy savings of 37.1 TWh over a decade compared to the BAU scenario. Even CIS with five-year intervals yields additional energy savings of 1.69 TWh in 2030 and 5.1 TWh cumulatively compared to the BAU scenario. In comparison, the introduction of the new refrigerant results in cumulative energy savings of 10.2 TWh in the best-case scenario. These findings emphasize the importance of enhancing the EER of residential AC systems as a priority in energy efficiency policy.

IMPACT OF THE MIGRATION FROM R410A TO R454C IN THE COMPRESSOR PERFORMANCE

The quasi-azeotropic mixture of refrigerants R410A replaced R-22 as the preferred refrigerant for use in residential and commercial air conditioners. However, newer regulations have mandated the phase-down of refrigerants with a high GWP as R410A, and thus, new substituting refrigerants and mixtures must be selected. Among the different possibilities, some manufacturers have been interested in mixtures such as R454C, composed of R32 and R1234yf (21.5/78.5), which has a GWP lower than the limit imposed by the new F-Gas regulation.In this study a variable-speed scroll compressor was tested working with both R410A and R454C at different operating conditions. From these tests, the compressor behavior with these refrigerant mixtures has systematically been analyzed in terms of compressor efficiency, volumetric efficiency, and working range.

A high performance solar-assisted ejector expansion refrigeration cycle for residential air conditioning

Introducing a solar collector between the compressor and condenser of an ejector expansion refrigeration cycle (EErc) can improve the performance of the system by further superheating the refrigerant. Hence, this paper proposes a new configuration of a vapor compression refrigeration system, solar compression-ejector expansion refrigeration cycle (SCEErc) with energy saving in the compressor via an ejector and an evacuated tube solar collector. The performance improvement of the proposed system under a wide range of operating conditions such as condenser and evaporator temperatures, superheating and subcooling degrees, nozzle and diffuser efficiencies, and solar radiation intensities has been evaluated and compared with EErc under the same operational conditions and for four different refrigerants. The results indicate that the coefficient of performance (COP) of the SCEErc increased by 26.53 % compared to the EErc for the solar radiation energy of 0.2 kW. Moreover, exergy analysis results indicate a 59 % increase in the exergy destruction of the condenser in the SCEErc compared to the EErc. This is due to the increase in heat rejected from the condenser to the environment, which can be beneficial if the condenser cooling air outlet is utilized for applications like heat recovery technologies. The R152a, boasting a COP of 3.963, presents itself as a more favorable alternative to R134a.

Refrigerant Selection in Air Conditioning Systems Considering Thermodynamic, Environmental, and Economic Performance Using the BHARAT-II Multi-Attribute Decision-Making Method

A simple and effective multi-attribute decision-making method, named as "Best Holistic Adaptable Ranking of Attributes Technique (BHARAT)-II”, to choose the best refrigerant for air conditioning systems is presented. The thermodynamic properties of the refrigerants, and their environmental, and economic performances are also considered for the selection. Two case studies are provided to demonstrate the proposed multi-attribute decision-making method. The first case study addresses the problem of selecting the best refrigerant for residential split air conditioners out of 15 alternative refrigerants considering 12 selection attributes; the second case study addresses the problem of selecting the best refrigerant for automobile air conditioning systems by considering 14 alternative refrigerants and 13 selection attributes. The results of the proposed decision-making method are compared with those of other well-known multi-attribute decision-making methods such as EDAS, TOPSIS, and MOORA. The proposed method is shown to be simple to implement, providing a logical way for allocating weights to the selection attributes and is useful to solve the best alternative refrigerant selection problems of the residential as well as industrial refrigeration and air conditioning.

Investigation of the application safety of R-290 in residential air conditioning systems

In the context of energy conservation and reduction of greenhouse gas emissions, there has been considerable attention focused on the application of the natural refrigerant R-290 (propane) in residential air conditioning (AC) systems. An ignition event can occur once R-290 is released from residential AC systems and encounters an ignition source within an indoor environment. For studying the application safety of cabinet AC systems, this paper employs Computational Fluid Dynamics (CFD) to simulate the release of R-290 in residential rooms and derive the real-time flammable volume during release. The most hazardous cases are identified by analysing the effects of practical influences such as release rate, release location, air supply velocity, room size, and furniture arrangement. On this basis, the frequency of ignition events is calculated under the selected leak hole in conjunction with a quantitative risk assessment methodology. The results show that when the airflow is off, the most hazardous case is the flow of refrigerant into the room after being obstructed by the enclosure, whereas when the airflow is on, the most hazardous case is the direct release of refrigerant from the air supply outlet into the indoor space. With the charge limits required by the IEC standard, the frequency of indoor ignition events in R-290 cabinet AC systems does not exceed 10−10 triennially. This study investigates the flammable volume and the frequency of ignition events associated with R-290 leakage, which is useful for analysing the safety measures for R-290 applications in residential AC systems.

Natural ventilation in Brazilian homes: depicting perceptions, usage patterns and motivations in a questionnaire survey

ABSTRACT Natural ventilation is a default conditioning strategy in the Brazilian residential sector, while fans and air conditioners are complementary strategies. However, climate change and the increasing air conditioning penetration in this sector threaten the prevalence of natural ventilation and the potential wind-driven (breeze) performance on households’ thermal comfort. A questionnaire survey launched across Brazil assessed multiple aspects of natural ventilation at home: perceptions, usage patterns and motivations behind its use or avoidance. Data analysis methods were multinomial logistic regression and contingency tables of categorical data. The findings indicated that households’ preference for a conditioning strategy related to income and energy-saving concerns (economic aspects). The frequency of use of natural ventilation showed a decreasing trend towards the higher income level and preference for air conditioning. In contrast, the frequency of use of natural ventilation tended to increase as households considered it more positively. Moreover, participants who preferred to use natural ventilation at home expressed less dissatisfaction with the oscillation and unpredictability of the breeze from natural ventilation. The survey outcomes highlight the benefits of a favourable scenario for natural ventilation at home, potentially impacting households’ preferences and routines.

Improved robust model predictive control for residential building air conditioning and photovoltaic power generation with battery energy storage system under weather forecast uncertainty

The rising demands for comfort alongside energy conservation underscore the importance of intelligent air conditioning control systems. Model Predictive Control (MPC) stands out as an advanced control strategy capable of addressing these demands. However, accurate prediction of all relevant variables remains a challenge in practical scenarios, complicating MPC’s ability to devise effective control actions amid prediction inaccuracies. To counteract this issue, this paper introduces an enhanced Double-Layer Model Predictive Control (DLMPC) algorithm. This innovative approach adjusts for discrepancies between forecasted and actual values without the need for additional variables and models, thereby reducing the adverse effects of prediction errors. Additionally, we develop precise models for room temperature simulation and for calculating air conditioning (AC) load and energy consumption, grounded in empirical data from residential settings and AC performance tests. Validation of these models demonstrates their efficacy in enabling MPC to formulate efficacious control strategies. When juxtaposed with a baseline model, the DLMPC algorithm significantly improves temperature regulation accuracy by up to 15.12% and achieves a 10.50% reduction in energy consumption over the heating season.

The role of load and distributed energy resources modeling in voltage recovery studies

Load modeling in power systems is crucial to stability studies. The analysis of certain dynamic phenomena requires proper load modeling. Fault Induced Delayed Voltage Recovery (FIDVR) relates directly to Residential Air Conditioner (RAC) stalling. Therefore, the modeling of induction motor (IM) loads is essential to this analysis. Delayed voltage recovery in the system can result in delayed power recovery in inverters connected to the transmission system, which connects photovoltaic and wind power plants to the Brazilian Interconnected Power System (BIPS). In the last few years, there has been a considerable growth of Distributed Energy Resources (DER) in Brazil. Modern and legacy ride-through settings coexist in power systems around the world. Inverters with legacy settings are more likely to disconnect in systemic events. This creates a context that has been assessed in this paper. The modeling of induction motors in the Acre-Rondonia system leads to a deterioration of this system’s dynamic performance, which can lead to collapse. DER’s voltage support can contribute to post-fault system voltage recovery, mitigating the delay caused by RAC stalling and avoiding collapse. Thus, more robust ride-through settings are required to avoid inverter disconnection. Moreover, dynamic voltage support and reactive current priority requirements are demands from inverters connected to the system. The results obtained show that this consideration enable more consistent results than the ones obtained by the classic ZIP load model.

Assessment of using different ozone-friendly R22 alternative refrigerants in residential air conditioners in a high-ambient temperature country

The performance of a vapor compression refrigeration system (VCRS)-based residential air conditioner operating in a high-ambient temperature (HAT) country was investigated using six zero-ODP (ozone depletion potential) refrigerants as replacements to R22. The non-flammable alternative refrigerants considered in the present research were R134a, R404A, R407C, R410A, R448A, and R507A. Using the basic conservation laws, the VCRS was modeled during steady-state operation and solved using engineering equation solver (EES) software. Coefficient of performance (COP), pressures and temperatures at compressor suction and discharge, Global Warming Potential (GWP), critical pressure and temperature, compressor pressure ratio, volumetric cooling capacity (VCC) specific cooling capacity (SCC), and refrigeration effect were utilized as assessment criteria for the alternative refrigerants considered. From these refrigerants, the highest values of suction pressure, discharge temperature, and condenser pressure were attained by R410A. In addition, the discharge temperatures for all refrigerants, except R134a, were all higher than their corresponding critical values, causing a quicker drop in the VCRS’s performance. As an alternative refrigerant, R407C showed the highest SCC of 141.0 kJ/kg followed directly by 139.2 and 138.0 kJ/kg for R410A and R448A, respectively. A reverse trend was found for VCC with respective values of 4722 and 3775 kJ/m3 for R410A and R448A. Lower volume flow rates and smaller-sized compressors are expected for higher VCC refrigerants. The same trend was found for the compressor’s specific work input and condenser’s specific heat transfer with values of (51.14, 46.82, and 45.38 kJ/kg) and (190.3, 187.8, and 183.4 kJ/kg) for R410A, R407C, and R448A, respectively. For applications in HAT countries, larger condenser’s specific heat transfer makes the refrigerant more applicable. Conversely, with respect to COP, refrigerant R134a with a value of 3.075 was the superior alternative followed by R448A and R407C with respective COPs of 3.042 and 3.011. Based on the overall assessment in terms of environmental obligation, COP, compressor input power, refrigerant flow rate required, and all the evaluations made in this research, refrigerant R448A was recommended as the most appropriate substitute to R22 which can effectively be used in residential air conditioners in a HAT country.

Cooling and heating innovations: exploring the diverse applications of heat pumps

Heat pumps are versatile and energy efficient devices that play a crucial role in modern heating, cooling, and refrigeration applications. This paper provides a concise overview of the diverse applications and benefits of heat pumps across residential, commercial, industrial, and transportation sectors. The paper discusses the principles of heat pump operation, emphasizing their capability to transfer heat from one location to another using thermodynamic processes. The work highlights key applications such as residential heating, ventilation, and air conditioning systems, commercial refrigeration, hot water heating, process cooling, and renewable energy integration. The energy efficiency and environmental benefits of heat pumps are also emphasized, showcasing their potential to reduce carbon emissions and contribute to sustainable energy practices. By understanding the broad scope of heat pump applications outlined in this work, researchers, engineers, policymakers, and industry stakeholders can gain insights into the significance of heat pump technology in advancing energy efficiency and addressing climate change challenges.

Aggregate scheduling potential evaluation of large-scale air conditioning loads

As an adjustable load, the air conditioning (AC) load is a high-quality resource for power system operation regulation. However, due to the large number of AC loads and the heterogeneity among individual users, the scheduling potential of AC loads is difficult to accurately calculate. An aggregate scheduling potential evaluation of large-scale AC loads is proposed. Firstly, according to the operation characteristics of ACs, the aggregation models of central ACs and household split-type ACs are constructed by using the equivalent thermal parameter model and Monte Carlo sampling method respectively. Secondly, based on the proposed aggregation models of large-scale AC loads, the AC loads are rescheduled by resetting the set temperature, and the scheduling potential calculation model of central ACs and residential ACs is obtained. Finally, case studies show that AC loads have considerable scheduling potential when the indoor temperature is maintained within the range of human comfort.

Thermal and dynamic characterization of a multi-jet system with different geometry diffusers

This paper proposed to use the impinging jets mixing process to improve the quality of residential heating and air conditioning. The main objective is to meet the requirements of occupants in terms of thermal comfort and air quality by proposing an optimal solution for the thermal homogenization improvement in the rooms by changing of the diffusers geometry and their arrangement in the ventilation and air-conditioning devices in blowing systems. This study involves both experimental and numerical studies of a three diffusers configurations composed of four peripheral jet with similar geometries and a central jet with a different geometry. All the configurations consist of four equidistant peripheral swirling jets, only the central jet that makes the difference between them. The configuration 1 includes a swirling central jet, on the other hand a circular central jet for the configuration 2 and finally a lobed central jet for configuration 3. The velocity and temperature distributions of the three configurations are investigated experimentally and numerically. Experimentally, the multifunction thermo-anemometer have been used to measure flow temperature and velocity. The dynamic and temperature features are more radially spread and get better homogeneity in configuration 3 and this is due to the energy distribution on the radial plane, which is relatively better than configuration 1 and configuration 2. The second part deals with numerical predictions of the dynamics and thermal fields of the three configurations considered. The study was realized using a RANS-based turbulence model. The numerical results are in reasonable agreement with our experiments for the three configurations. With this study, detailed information on the structure of the resulting flow is very useful to deepen the understanding of the physics of jet interaction and to validate turbulence models. The turbulence simulation is realized by the k-ω-SST model. This model gives a satisfactorily predicts the axial drop in velocity and temperature over the entire study range, demonstrating its ability to handle the interaction between swirling and lobe jets. Our results show that the geometry of the central diffuser is essential. This allows the axial velocity to decrease faster than configurations 1 and 2. This increases lateral diffusion, resulting in better homogenization.

Revealing and optimizing the design of cover installation for outdoor units of air conditioners through CFD simulations and thermodynamic modeling

When renewing building facades in most Chinese cities, covers are often designed and installed to conceal the outdoor units of residential split air conditioners for congruousness of building facades. However, how those covers impact airflow and energy efficiency should be thoroughly examined. This study investigates two popular designs of cover (louver and circular-hole) and selects Nanjing, renowned for its hot summers, as the case city. This study employs Computational Fluid Dynamics models to simulate airflow obstruction caused by the covers surrounding the outdoor units. Grey Model, trained from the CFD results, quantifies interactions between design of cover and inlet air temperature. Additionally, a thermodynamic model assesses the covers' impact on the coefficient of performance of air conditioners. The findings reveal that the primary cause of outdoor unit overheating is warm air backflow from the outlet to the inlet. A mere 1 °C increase in inlet air temperature can reduce COP by 4.1%–8.7%. The maximum temperature differences caused by different designs of cover are 4.5 °C for the louver type and 4.4 °C for the circular-hole type. To mitigate these negative impacts, optimal design recommendations are provided: a minimum distance between the cover and outdoor unit of 0.29 m for louver type and 0.1 m for circular-hole type, both feasible in most installations. These findings can help designers, manufacturers, installers and policymakers, to facilitate the design and installation of optimal covers for outdoor air-conditioning units, thus minimizing energy efficiency losses.

RETRACTED: Enhancing desalination efficiency using waste heat from household air conditioning: A heat pipe-assisted HDH system performance analysis

This study presents an experimental exploration of a desalination system that produces freshwater from saltwater using a novel heat pipe-assisted humidification-dehumidification (HDH) process. The system utilizes waste heat recovered from residential air conditioners that use vapour compression refrigeration systems. The study focuses on the mass and heat transfer within the system's components, with performance evaluations conducted at three different air conditioning temperatures (19 °C, 20 °C, and 21 °C). The experiments highlight the freshwater production of the R32 heat pipe over the R134a and R600a heat pipes. The study estimates the system's cost-effectiveness at $0.0085/L, emphasizing its economic viability. Preheating resulted in significant improvements in freshwater yield, ranging from 43.33 % to 51.5 %, at temperatures of 21 °C and 20 °C, respectively. The Gain Output Ratio (GOR) doubled from 0.75 to 1.52, indicating a more energy-efficient process with significant improvements in the effectiveness of humidification and dehumidification. The pH levels improved from 8.32 to 7.07, representing a 15 % reduction and falling within the WHO-recommended range of 6.5–8.5. Electrical Conductivity (EC) shows a notable reduction from 62,720 to 826.1 micromhos/cm, representing a 98.68 % reduction, and well below the permissible limit of 1500 micromhos/cm. Total Dissolved Solids (TDS) also experienced a drop from 31,777 to 413.1 ppm, representing a 98.7 % reduction, and falls under the WHO guideline of <600 ppm for drinking water. The experiments prove that the use of waste heat from household air conditioners for sustainable freshwater production through the HDH desalination method, with the added efficiency benefits of heat pipe.