Energy Efficient Air Conditioning Research Articles

Comparison of Energy Consumption Between a Standard Air Conditioner and an Inverter Type Air Conditioner in an Office Space

Demand for air conditioners (ACs) has exponentially increased worldwide over the last few years. Countries with booming economies report high growth of sales of room air conditioners. Sri Lanka is not an exception. With the increased gross domestic product (GDP) and warming climates, demand for room air conditioners is expected to further increase. Meeting the increased demand for electricity will be a challenge. Increased use of energy efficient air conditioners has positive impacts on the national grid, especially during periods of high demand. In a regular AC, the compressor runs at a fixed speed and is either ON or OFF. In an inverter AC, the compressor is always on, but power drawn depends on the demand for cooling. The speed of the compressor is adjusted appropriately. In this study, the energy consumption of a regular and an inverter AC of the same capacity was evaluated in a typical office room, under similar operating conditions. Energy consumption was measured for six consecutive weeks and compared. Results show that the daily average energy consumption (for an 8-hour operating period) was 13.5 kWh for the standard AC and 8.7 kWh for the inverter type AC. Therefore, it is concluded that inverter technology can save about 35% of electricity consumed over a standard air conditioner. With the expected growth of air conditioner use and ambient temperature rise, inverter technology can significantly contribute to reduce the peak demand and energy use.

Time-of-Use Electricity Pricing and Residential Low-carbon Energy Technology Adoption

This paper provides the first empirical evidence on the correlation between Time-Of-Use (TOU) electricity pricing and the adoption of energy efficient appliances and solar panels. We use household-level data in Phoenix, Arizona from an appliance saturation survey of about 16,000 customers conducted by a major electric utility. Our empirical results show that TOU consumers are associated with 27% higher likelihood to install solar panels but not more likely to adopt energy-efficient air conditioning based on the propensity score matching and coarsened exact matching methods. The findings highlight that policy makers could combine TOU and solar panels when implementing educational programs or when giving out financial incentives to consumers. Our results imply that TOU is associated with a similar impact of the incentive offered by $2,070∼$10,472 tax credits or rebates on solar adoption.

Air Conditioning Energy Saving from Cloud-Based Artificial Intelligence: Case Study of a Split-Type Air Conditioner

This study developed cloud-based artificial intelligence (AI) that could run AI programs in the cloud and control air conditioners remotely from home. AI programs in the cloud can be altered any time to provide good control performances without altering the control hardware. The air conditioner costs and prices can thus be reduced by the increasing energy efficiency. Cloud control increased energy efficiency through AI control based on two conditions: (1) a constant indoor cooling rate and (2) a fixed stable range of indoor temperature control. However, if the two conditions cannot be guaranteed or the cloud signals are lost, the original proportional-integral-differential (PID) control equipped in the air conditioner can be used to ensure that the air conditioner works stably. The split-type air conditioner tested in this study is ranked eighth among 1177 air conditioners sold in Taiwan according to public data. It has extremely high energy efficiency, and using AI to increase its energy efficiency was challenging. Thus, this study analyzed the literature of AI-assisted controls since 1995 and applied it to heating, ventilation, and air conditioning equipment. Two technologies with the highest energy saving efficiency, a fuzzy + PID and model-based predictive control (MPC), were chosen to be developed into two control methodologies of cloud-based AI. They were tested for whether they could improve air conditioning energy efficiency. Energy efficiency measurement involved an enthalpy differential test chamber. The two indices, namely the energy efficiency ratio (EER) and cooling season power factor (CSPF), were tested. The EER measurement is the total efficiency value obtained when testing the required electric power at the maximum cooling capacity under constantly controlled temperature and humidity. CSPF is the tested efficiency value under dynamic conditions from changing indoor and outdoor temperatures and humidity according to the climate conditions in Taiwan. By using the static energy efficiency index EER for evaluation, the fuzzy + PID control could not save energy, but MPC increased the EER value by 9.12%. By using the dynamic energy efficiency index CSPF for evaluation, the fuzzy + PID control could increase CSPF by 3.46%, and MPC could increase energy efficiency by 7.37%.

Enhancing performance of wall mounted split air conditioner using capillary tube in a tube heat exchanger

The high cost of electricity rates has affected the demands of the public for the availability of energy-efficient air conditioning systems. This study aims to obtain data on improving performance of air conditioner using capillary tube in tube heat exchangers. Tests were carried out on a wall mounted split AC capacity of 9000 Btu/h which was modified using a heat exchanger with capillary tube in tube heat exchanger. The results showed that the installation of a capillary tube in tube heat exchanger on a wall mounted split AC resulted in an increase RE and COP of 13.2% and 14.9%, respectively. In addition, the room cooling time in the TiTHX capillary mode testing is shorter. So it has implications for lighter compression work and saves the power consumption required by AC.

In pursuit of a replacement for conventional high-density polyethylene tubes in ground source heat pumps from their composites – A comparative study

Ground-source heat pumps, as the most environmentally friendly and energy-efficient air conditioning technology, suffer from a great required length of ground heat exchanger, partly arising from the low thermal conductivity of high-density polyethylene tubes commonly used in ground heat exchangers. In an attempt to find a replacement with an acceptable thermal conductivity for high-density polyethylene tubes, in this study, first, a comprehensive comparative study on fillers commonly used in thermally conductive polymer composites and resulting high-density polyethylene composites was conducted. Then, based on the advantages and disadvantages presented, an appropriate composite was selected and applied in the modeling of a case study to demonstrate the effect of thermal conductivity of the tube on the borehole length of the ground heat exchanger. The findings indicated that low-temperature in situ expandable graphite was a suitable filler to add to high-density polyethylene polymer, resulting in a composite with acceptable thermal and rheological properties. Investigating the effect of thermal conductivity of the tube on the borehole length revealed some intriguing findings. First, using a composite with a thermal conductivity of approximately 1.4 Wm−1 K−1, for instance, the affordable high-density polyethylene composite filled with 10 wt% of low-temperature in situ expandable graphite, the length of the ground heat exchanger reduced by a notable amount of 10 %, which is more than 68 % of the maximum potential for reducing borehole length could be achieved by improving thermal properties of the tube. Furthermore, using polymer composites with thermal conductivity in the range of 2 Wm−1 K−1 could obviate the need for using metal tubes, which are used even nowadays in certain cases. However, due to the lack of results of some specific test, such as Hydrostatic Design Basis, the mechanical properties of the newly introduced composite require further investigation.

Characterizing energy-related occupant behavior in residential buildings: Evidence from a survey in Beijing, China

Despite progress in energy efficiency technologies and energy intensity reduction, the buildings sector's final energy consumption and associated CO2 emissions both continue to grow, pointing to the necessity of understanding real occupant behavior. This study, therefore, explores occupants' energy-related behavior in residential buildings with empirical data from a large-scale survey in Beijing, China, aiming to present an in-depth and comprehensive picture of occupant behavior. We obtained a total of 1003 valid responses to an online questionnaire concentrating on occupant behaviors with respect to space heating and cooling, water heating, cooking, lighting, appliances and other equipment. Our results show that, typically, purchase behavior is overall energy-efficient, as most appliances purchased are energy efficient. For both purchase and usage behaviors, air conditioning (AC), which is used for both space heating and cooling, plays a critical role as residents usually have less energy efficient AC in their homes and use it more often and for a longer period of time than other devices. Their habitual reactions are consistent across all habitual categories, but show no significant correlation with their purchase behavior. There is no single, straightforward and coherent pattern that can be explained by any single socio-demographic factor. These findings offer a behavioral insight into efforts to improve residential energy efficiency at the city scale. For instance, more policy attention should be directed to occupants’ purchase and usage behavior of ACs, such as by promoting the energy rating program in a more effective way. Moreover, given the lack of apparent linkage between purchase and habitual behaviors, a comprehensive policy framework incorporating different measures for different types of behavior is necessary. The complexity underlying behavioral choices also suggests the necessity of better understanding the behavioral patterns and their determining factors, as well as avoiding any simplistic assumption in policy making that aims to take behavioral factors into account.

Energy Efficient Air Conditioning System of the Temple Complex

The purpose of this work is to develop a year-round energy-efficient air conditioning system for the temple complex, that meets modern engineering requirements and standards. And it should not violate the traditional appearance of an Orthodox church.In this article there are considered the requirements and standards for the construction of the temple complex together with the architectural solution and the geographical location of the construction entity. The proposed air conditioning system (ACS) with a pneumohydraulic diagram and design modes is described. This system is valid for the summer and winter seasons. The main element of the ACS of the temple complex is an array of heat pipes. The efficiency of the installation is achieved, first of all, due to the recovery of soil heat in the annual cycle. In addition, efficiency is increased by utilizing the heat of the waste air stream and indoor recirculation systems. The article represents a constructive solution for the proposed heat pipe and its design modes of operation in the summer and winter periods together with the expected technical characteristics in different modes of operation, as well as design options for the upper heat exchanger. There is given the concept of the arrangement of the elements of the pneumohydraulic diagram on the cartographic plan of the building and their mutual correlation with the intensity of the operating mode for the soil. And the last, but not least, the article represents a simulation of the annual soil regime, calculated by the finite element method, performed in the ANSYS computational environment.

Data-driven prediction of vehicle cabin thermal comfort: using machine learning and high-fidelity simulation results

Predicting thermal comfort in an automotive vehicle cabin's highly asymmetric and dynamic thermal environment is critical for developing energy efficient heating, ventilation and air conditioning (HVAC) systems. In this study we have coupled high-fidelity Computational Fluid Dynamics (CFD) simulations and machine learning algorithms to predict vehicle occupant thermal comfort for any combination of glazing properties for any window surface, environmental conditions and HVAC settings (flow-rate and discharge air temperature). A vehicle cabin CFD model, validated against climatic wind tunnel measurements, was used to systematically generate training data that spanned the entire range of boundary conditions, which impact occupant thermal comfort. Three machine learning algorithms: linear regression with stochastic gradient descent, random forests and artificial neural networks (ANN) were applied to the simulation data to predict the Equivalent Homogeneous Temperature (EHT) for each passenger and the volume averaged cabin air temperature. The trained machine learning models were tested on unseen data also generated by the CFD model. Our best machine learning model was able to achieve a test error of less than 5% in predicting EHT and cabin air temperature. Predicted EHT can also yield thermal comfort metrics such as Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD), which can account for different passenger profiles (metabolic rates and clothing levels). Machine learning models developed in this work enable predictions of thermal comfort for any combination of boundary conditions in real-time without having to rely on computationally expensive CFD simulations.

Toward energy-efficient buildings in Oman

ABSTRACTEnergy consumption has drastically increased in buildings in several places over the last decade owing to economic growth and population increase. Substantial energy saving can be attained if these buildings are designed in a proper way. This paper presents a case study about energy-efficient building methods that can be applied in Oman. A residential building was taken as a case study which was evaluated using DesginBuilder software. Several energy efficiency measures (EEMs) such as thermal insulation in walls and roof, high-performance glazing, external shading, LED lights and energy-efficient air conditioning were evaluated. Total energy consumption was reduced by as much as 37%. Adding 6 kW PV and solar water heater can reduce the annual consumption by more than half when compared to the business as usual case. In addition to the technical feasibility, the design with EEM and renewable energy systems was found to be economically attractive. The results from this study provide energy-efficient design guidelines for residential sector in hot climates.

Performance comparison between metal-organic framework (MOFs) and conventional desiccants (silica gel, zeolite) for a novel high temperature cooling system

The use of desiccant-coated heat exchangers (DCHE) in air conditioning systems possesses great advantages in the independent control of both temperature and humidity, as well as low energy consumption and high coefficient of performance (COP). The paper presents a novel high temperature cooling system that uses metal-organic frameworks (MOFs) as sorbents for humidity control. MOFs are a new class of porous crystalline materials consisted of metal clusters and organic linkers, which have an excellent performance of water sorption due to the large specific surface areas and high porosity. In this research, we directly coat MOFs on the heat exchange surface of evaporator and condenser. The evaporator can simultaneously remove both the sensible and latent loads of the incoming air without reducing the temperature below its dew point. The regeneration of wet MOFs is completely driven by the residual heat from the condenser. We also make comparison between the MOF-coated cooling system and conventional desiccants coated ones (i.e. silica gel, zeolite) by way of tests and calculation. The results indicate that the dehumidification capacity of the MOF-coated heat exchanger outperforms other conventional desiccant coated ones under low regeneration temperature (∼50°C). The MOF-coated system has a high COP, up to 7.9, and can save 36.1% of the energy required, compared to the traditional vapour compression system with reheating. The amphiphilic MOFs used in the study have high water uptake and low regeneration temperature, and they thus have the potential for being scaled up for large-scale applications in energy efficient air conditioning systems.

Influence of potential liquid desiccants on solution cooling, heating, and pumping loads of membrane-based liquid desiccant air conditioning system: An analytical study

This paper is intended to study the methodology for choosing the suitable desiccant solution among LiCl, CaCl2, LiBr, and KCOOH solutions (commonly used potential solutions) at optimum heat capacity for an energy-efficient membrane-based liquid desiccant air conditioning system. An analytical model which is validated with existing experimental and numerical results was adopted in this study to find the output parameters. Performance indices considered in this study are solution pumping power, solution heat addition rate (Qadd), and chiller load (Qchiller). Considering the specified solutions at their maximum safe concentrations (0.40, 0.35, 0.55, and 0.75, which are just below their saturation concentrations), performance indices analyzed at fixed ambient condition and dehumidification rate at different heat capacity ratios (Cr* = 4.0, 3.0, 2.5, 2.0, and 1.5). At their corresponding optimum Cr*, Qadd is observed low for CaCl2, whereas it was high for LiBr. Solution pumping power and Qchiller are observed as lesser for the LiBr solution. At their corresponding design parameters, LiBr solution’s investment cost is found to be 30% higher than LiCl solution’s, but its operating cost (pumping power) is nearly 26% to 40% less than the LiCl solution, which suggests that the LiBr solution is the most efficient solution among the four.

Energy efficiency and cost saving opportunities in public and commercial buildings in developing countries – The case of air-conditioners in Ghana

Available data and market surveys conducted in Ghana have shown that 60–80% of electricity consumed in offices of public and commercial buildings is used to run air-conditioners to provide indoor thermal comfort for productive office work. Electricity consumptions of these air-conditioners are relatively high and are in the range of 3000–5400 kWh/yr per air-conditioner depending on the brand and the cooling capacity. Low energy efficiency rating of the air-conditioners is a major contributing factor to their high electricity consumption.This present work has conducted studies on the energy efficiency of air-conditioners used in the offices of public and commercial buildings in Ghana. Technical data from a national survey conducted on air-conditioning equipment used in the country was used for this study. In addition, a power quality clamp meter was used to monitor the actual power consumptions of stratified samples of the conventional air-conditioners in the offices, as well as that of an inverter air-conditioner installed in an office.The results from this study show that over 85% of air-conditioners used in Ghana exist in the lowest energy efficiency ratio category (1-star) and the remaining percentages are in the next lower categories (2 and 3-stars). It has been determined that enforcing energy efficiency regulations to shift the air-conditioner market in Ghana into the higher energy efficiency ratio (EER) categories has huge benefits for the country. For instance, there are annual electricity savings potential of 260 GWh and 1770 GWh respectively for the year 2020 and 2030 using inverter air-conditioners which have higher energy efficiency rating (4-star equivalent) compared to the current lower EER air-conditioners in the country. It is also determined that if Ghana continues to follow business as usual with low EER air-conditioners, it will need to install electricity generation capacity of about 480 MW by 2030 to handle influx of low energy efficient air-conditioners alone.Financial analysis has also revealed that there is opportunity for electricity consumption cost savings of about US$ 1.96 billion from the year 2018–2030 with higher EER air-conditioners (4-star) being installed in the country compared to the current low EER air-conditioners.

Thermal energy analysis on liquid desiccant air conditioning system at different desiccant solution parameters

Selection of suitable liquid desiccant operating parameters plays a significant role in the design of energy efficient liquid desiccant air conditioning system. To achieve same dehumidification rate from ambient air, different combinations of solution parameters (heat capacity ratio, concentration, and vapor pressure) could be employed in the system. Considering dehumidifier air inlet condition and dehumidification rates are fixed, an analytical study is carried out on the thermal energy analysis of the system at different solution operating parameters. Operating parameters considered in this study are solution concentrations ( Cs = 0.25, 0.3, 0.35 and 0.40) and heat capacity ratios ([Formula: see text] = 2.5, 3, 4 and 5). Control volume which includes a pair of air and solution channels (half width channels) of full scale liquid-to-air membrane energy exchangers (LAMEE) has been chosen to analyze the energy transfer between air and solution. The results indicate system requires lesser chiller load ( Qchiller) at high concentration and low heat capacity ratio ( Cs = 0.40 and [Formula: see text] = 2.5) which is 0.29 kW to achieve 0.61 kW cooling load. This is 99% lesser than the Qchiller at high concentration and high heat capacity ratio ( Cs = 0.40 and [Formula: see text] = 5) and 30% lesser than the Qchiller at low concentration and low heat capacity ratio ( Cs = 0.25 and [Formula: see text] = 2.5). Solution heat addition rate ( Qadd) per kW cooling capacity ( Qcc) at this solution condition is found as 0.85 kW.

Energy efficient moist free air conditioning system integrated with total heat desiccant solution system

This paper experimentally investigates the performance of an efficient moist free air conditioning system. This system consists of a vapor compression system uses R-134a-15.5 kW capacity has two evaporators. Evaporator-C is integrated with a desiccant solution of lithium chloride and treats the total heat of supply air. Evaporator-D deals with sensible heat and controls the exit temperature and relative humidity of supply air separately. The supply air is moist free with low exit relative humidity. The effect of both air and desiccant solution mass flow rate is studied. At air mass flow rate of 0.4 kg/s, the total cooling capacity and system coefficient of performance reached to 14.1 kW and 5.1; respectively. The supply air relative humidity and dry air temperature are 39.2% and 15.8 °C; respectively. This system is compared to the VCR with reheat and achieves an energy saving of 48.2%.

Approaches to Energy Efficiency in Air conditioning: Innovative processes and thermodynamics

Abstract Air conditioning in buildings has transformed our human lives greatly with work efficiency in commercial buildings and improved lifestyle in all weather. However, these improvements are accompanied with the negative effects from the emissions of greenhouse gases (GHG), both directly via refrigerant emissions and indirectly through electricity generation by the burning of fossil fuels. Although there were significant improvements in the efficacy of chillers since 2000, the kW/Ron of chillers for cooling for electrically driven DCS have reached an asymptotic level of 0.85±0.03 kW/Rton for the tropics and a 20% higher for the hot and dry arid climate. The levelling-off phenomenon of chillers’ energy efficiency is attributed the improvements limits exploited from the efficacy of compressor and refrigerant technologies. Thus, an out-of-box solution, such as the decoupling of latent to sensible cooling in the dehumidification cum the indirect evaporative coolers (DH-IEC) to improve energy efficiency, It is projected that a quantum jump of 0.5 kWh/m3 or less is urgently needed for future sustainable cooling. In this paper, we adopted a top-down approach in evaluating the upper-bound energy savings of an economy if one were to employ the innovative DH-IEC cycle is assumed to be applied to the Singapore city state is highlighted with respect to the savings in the primary energy, emission of CO2 and the water savings of up to 40 % can be potentially achieved.

A Magnetocaloric Booster Unit for Energy-Efficient Air-Conditioning

A concept for the application of a magnetocaloric device in energy-efficient air conditioners is introduced. In order to evaluate this concept, a test stand has been developed equipped with a magnetic field source providing about a 1.5-T flux density change into which different regenerator geometries can be implemented and evaluated. A processing route for the production of profiled magnetocaloric LaFeSiMn-based composite plates by tape casting is presented. The processed plates show a maximum isothermal entropy change of about 3.8 J kg - 1 K - 1 at a magnetic field change of 1.5 T at 285 K. The hydraulic and thermal performance of regenerator geometries that can be realized by profiled plates is assessed by calculations.

Approaches to energy efficiency in air conditioning: A comparative study on purge configurations for indirect evaporative cooling

This paper presents a mathematical model to enable a more in-depth understanding of the combined heat and mass transfer processes of a counter-flow indirect evaporative cooler operating in semi-arid regions. A series of simulation was conducted to compare the performances between a single-purge and four-purge configurations. Furthermore, the effect of several parameters on the performance of the single-purge configuration was investigated under the baseline condition. The developed model was validated against experimental data from literature to within 2% discrepancy. Key results revealed that the single-purge configuration produced higher cooling capacity (around 20% higher), as well as higher dew-point effectiveness under the same operating conditions. A parametric study was also made on the single-purge configuration. The results revealed that lower product air temperature and higher dew-point effectiveness were achieved with longer channel length and larger purge ratio. However, the maximum cooling capacity approached its maximum with longer channel length and 35% purge ratio.

Blooms Taxonomy Levels as applied to developing Energy Efficient Air Conditioner Compressor

Blooms Taxonomy Levels as applied to developing Energy Efficient Air Conditioner Compressor

Optimal Performance Evaluation of Energy Efficient Residential Air Conditioning System with Nanofluid-based Intercooler using Taguchi-based Response Surface Methodology

Air conditioning is viewed as a major energy consuming area in domestic and industrial applications. However energy conservation is effectively possible in air conditioners by employing an intercooler with nanofluids, which can consequently reduce the compressor load. This paper presents an investigative report on the performance of proposed energy efficient air conditioning system. A binary mixture of ethylene glycol (C2H6O2) and water is used as the base fluid in the shell and coil type heat exchanger (SCHE). The volume concentration of C2H6O2 in base fluid, type of suspended nano particles (Al2O3 and MgO), flow rate of nanofluid at shell side of intercooler and the volume fraction of nano particles are chosen for experimentation designed using Taguchi L18 orthogonal array. The coefficient of performance (COP) of the nanofluid-based domestic air conditioner is estimated as the performance index (response). Quadratic model and response surface plots are generated to observe the effects of inputs on the COP. The nano particles of MgO (0.75%v/v), suspended in a binary mixture with 28.65% C2H6O2 is found to improve the system performance (COP) at a nanofluid flow rate of 2.42 LPM.

Willingness to accept energy-saving measures and adoption barriers in the residential sector: An empirical analysis in Beijing, China

This paper investigates the public attitude toward and willingness to accept six energy-saving measures in the residential sector in Beijing, China. The qualitative results derived from questionnaires show that financial incentives and the desire to reduce energy consumption are the most significant factors driving the public to adopt the measures and that the unavailability of electric vehicle (EV) chargers is a crucial barrier to the promotion of EVs. The quantitative results indicate that socioeconomic variables have a greater impact on technical energy-saving measures than behavioral ones. Renters or individuals with a high risk preference have a lower willingness to accept energy-efficient air conditioners. The price of gasoline, convenience of EV chargers, EV policy package, and environmental concern can significantly influence willingness to purchase an EV. With regard to behavioral energy-saving measures, control of the heating system and the influence of nearby people (spillover effect) significantly increase the preference for closing windows when the heating is on. The public transportation convenience, high gasoline prices and the congestion charge have significant effects on residents’ willingness to use public transportation. Infrastructure upgrades to heating and transportation would remove adoption barriers and facilitate energy conservation. Price policies and preferential policies related to EVs could have a significant impact on household choice of transportation mode. Finally, increasing the public energy-saving awareness and environmental concern is recommended to facilitate the promotion of energy-saving options.