Energy Efficient Air Conditioning Research Articles

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.

Energy-Efficient Elastocaloric Cooling by Flexibly and Reversibly Transferring Interface in Magnetic Shape-Memory Alloys.

Elastocaloric cooling is currently under extensive study owing to its great potential to replace the conventional vapor-compression technique. In this work, by employing multiscale characterization approaches, including in situ neutron diffraction in a loading frame, in situ transmission electron microscopy observation at different temperatures, in situ synchrotron X-ray Laue microdiffraction, and high-resolution infrared thermal imaging, we have investigated the thermal and stress-induced martensitic transformation, the stability of superelastic behavior and the associated elastocaloric effect for a Heusler-type Ni50.0Fe19.0Ga27.1Co3.9 single crystal. On the basis of transformation from cubic austenite into monoclinic martensite with a flexibly and reversibly transferring interface, this unique single crystal exhibits a giant elastocaloric effect of 11 K and ultralow fatigue behavior during above 12 000 mechanical cycles. The numerical simulation shows that the Ni50.0Fe19.0Ga27.1Co3.9 alloy offers 18% energy saving potential and 70% cooling capacity enhancement potential compared to the conventional shape-memory nitinol alloy in a single-stage elastocaloric cooling system, making it a great candidate for energy-efficient air conditioner applications.

Rebound effect across seasons: evidence from the replacement of air conditioners in Japan

Switching to more energy-efficient appliances may lead to higher energy demand. This phenomenon is known as the rebound effect, which may lead to less power saving than expected prior to the switch. Using a combination of propensity score matching with the difference-in-differences method, we examine the change in household electricity consumption that may be caused by replacing air conditioners with more energy-efficient ones. Based on the results of our estimations, we calculate the magnitude of the rebound effect for summer and winter. We find that the rebound effect is positive in summer and winter, and the magnitude is higher in winter (7.87% versus almost 100%, respectively). The estimated rebound effect is small in summer, implying that the power-saving effect due to switching to energy-efficient air conditioners is sizable. On the other hand, no power-saving effect due to the switch was found in winter.

An experimental investigation of performance characteristics of an energy-efficient air conditioning in vehicle

In order to reduce the fuel consumption of air-conditioning in vehicle, an air conditioning system was designed based on the principle of direct evaporative cooling and liquid dehumidification. In this paper, main devices were conducted in the way of numerical simulation and experiment, the overall layout of the device was designed under the guidance of Solidworks. The results showed that the high temperature and humidity air could be changed into the livable air. In particular, the regenerator could be operated with waste heat from the engine for higher energy efficiency. It can achieve the effect of the temperature dropped by 5-7°C. which need less energy than the traditional car air-conditioning while satisfy the comfort of the human body.

Getting More of Something Without Subsidizing It: Impact of Time-of-Use Electricity Pricing on Residential Energy Efficiency and Solar Panel Adoption

This paper provides the first empirical evidence of the impact of Time-Of-Use (TOU) electricity pricing on the adoption of energy efficient appliances and solar panels. A theoretical model is constructed to show that TOU customers have a larger incentive to adopt these technologies compared to customers on non-dynamic pricing plans. Using household-level data in Phoenix, Arizona from an appliance saturation survey of about 16,000 customers conducted by a major electric utility and relying on propensity score matching and coarsened exact matching to address potential selection bias, empirical results show that TOU consumers are 27% more likely to install solar panels but not more likely to adopt energy-efficient air conditioning. The findings highlight that TOU can act as a cost-effective policy instrument to facilitate solar panel adoption, compared to other more costly instruments with a similar magnitude of impacts such as tax credits or rebates of $2,070~$10,472.

Characterizing domestic electricity consumption in the Indian urban household sector

The aim of this work is to forecast electricity consumption for energy efficient management in the Indian urban household by evaluating current practices which are followed in a living place (residence/home). Conclusions and electricity consumption forecasting are derived from the data obtained through a questionnaire survey conducted in three different climate zones of India. Utilizing micro level primary data obtained through the household survey, authors have analysed the variation in the electricity consumption and the factors such as demographic and dwelling attributes which cause such variations. Ownership of major home appliances like air conditioner, refrigerator and electric water heaters (geyser) have seen a significant rise over the years in households. They are found to contribute high electricity consumption in Indian urban households.Price elasticity of electricity consumption is found as −0.72 (negative sign indicates that when the price of electricity increases, the consumption decreases). Electricity consumption in the Indian urban household is observed more responsive to ownership of air conditioner rather than demographic variables and other appliances. Considering predicted accountability of India for increased global emission due to air conditioning, ownership of air conditioners was investigated in depth, based on the data captured in the questionnaire survey. Factors considered were tonnage, energy star rating, usage duration, year of purchase, and numbers. It is observed that, electricity consumption in air conditioning could be reduced by 15% to 31%; if existing household air conditioners, older than 7 years were replaced by new energy efficient air conditioners, subject to all other parameters like tonnage and usage remain constant. The outcomes of this study can be utilized for swotting the electricity prices and policy making.

Evaporative Cooling With Novel Devices: A Review

Evaporative cooling is an energy efficient, environmentally friendly and cheap air conditioning technology. In this paper, the principles underlying the operation of evaporative cooling (EC) systems are recalled and their novel design characteristics are discussed. The review is presenting in details: theory, working principles, flow and construction of various EC system. Paper describes the work done by various researchers on conventional and newly developed cooling systems. The working principles and thermodynamic characteristics of different types of EC i.e. direct, indirect and dew point EC are discussed.

Energy appliance transformation in commercial buildings in India under alternate policy scenarios

The total electricity consumption from commercial sector was about 9% during 2013–14 in India. Load research survey was carried out to study the usage patterns for all types of electric appliances used in commercial establishments at income, appliance and end-use levels in Gujarat state of India – one of the most progressive states. Penetration level of efficient appliances, electricity load curves and Energy Performance Index (EPI) were estimated. The mean EPI was 98 kWh/m2/year (SD = 105.5) for surveyed small commercial establishments (low income) while mean EPI was 181 kWh/m2/year (SD = 68) for surveyed large commercial establishments (Malls). Electricity saving potentials was estimated if electric appliances at these commercial establishments were replaced with efficient appliances. Four alternate scenarios were analyzed using cost of conserved energy (CCE) curves with various efficiency enhancement options – following at least commercial sub-category level median EPIs, following average EU equivalent EPI levels, following average EPI levels of equivalent US commercial establishments, and following the best available technologies (BAT). The average energy savings ranged between 14% and 25% across buildings and scenarios. Energy efficient air-conditioner and LED lights offer the highest energy savings potential among appliances.

Energy-efficient air conditioning in shallow mines

Energy-efficient air conditioning in shallow mines

Occupancy estimation with environmental sensing via non-iterative LRF feature learning in time and frequency domains

Occupancy information is an important parameter to energy-efficient Air Conditioning and Mechanical Ventilation (ACMV) systems for the design of suitable control strategies. To predict the occupancy in an air-conditioned space, the harnessing of environmental parameters such as carbon dioxide, relative humidity, temperature and air pressure can provide an implicit and non-intrusive representation of occupancy in the room. Most of the prior works utilized the statistics of time domain features with feature selection, but the way to obtain suitable features based on raw sensor data still remains an issue. The niche of this paper is that a better representation of pattern of occupancy with respect to the environment can be learned automatically to enhance the estimation performance, rather than depending too much on human empirical knowledge in feature extraction. The prediction accuracy could be improved by using a non-iterative feature learning method, namely the Local Receptive Fields (LRF) with random weights. We find that raw data from the frequency domain together with time domain data which carries rich information for feature learning can enhance the performance of the estimation system. Experiments are evaluated in a research laboratory environment which consists of 24 cubicles with more than 20 occupants. Our experimental results demonstrated that feature learning with additional frequency domain data can significantly improve the occupancy estimation system.

Performance assessment of a membrane liquid desiccant dehumidification cooling system based on experimental investigations

A membrane-based liquid desiccant dehumidification cooling system is studied in this paper for energy efficient air conditioning with independent temperature and humidity controls. The system mainly consists of a dehumidifier, a regenerator, an evaporative cooler and an air-to-air heat exchanger. Its feasibility in the hot and humid region is assessed with calcium chloride solution, and the influences of operating variables on the dehumidifier, regenerator, evaporative cooler and overall system performances are investigated through experimental work. The experimental results indicate that the inlet air condition greatly affects the dehumidification and regeneration performances. The system regeneration temperature should be controlled appropriately for a high energy efficiency based on the operative solution concentration ratio. It is worth noting that the solution concentration ratio plays a considerable role in the system performance. The higher the solution concentration ratio, the better the dehumidification performance. However simultaneously more thermal input power is required for the solution regeneration, and a crystallization risk in the normal operating temperature range should be noted as well. The system mass balance between the dehumidifier and regenerator is crucial for the system steady operation. Under the investigated steady operating condition, the supply air temperature of 20.4°C and system COP of 0.70 are achieved at a solution concentration ratio of 36%.

Energy Conservation Measures for an Office Building in Warm and Humid Climate

Objective: To study the effect of various energy conservation measures on building energy performance. Analysis: U.S Green Building Council’s Leadership in Energy and Environmental Design (LEED) Rating System for green building uses energy modeling as one way to demonstrate the energy use of a building and to quantify the savings to the proposed design. A whole building energy simulation tool, Visual DOE4.0 is used to estimate the energy performance of an office building in warm and humid climate. The tool is used for recommending energy saving strategies for insulation, glazing, shading devices, lighting and controls and air conditioning equipment. Performance analysis of the building with different combinations of measures is carried out to identify the best possible strategy. Findings: It is analyzed green roof, insulated AAC wall, glazing system with low Solar Factor (SF) , shading devices, energy efficient air conditioning and efficient lighting systems & control helps in reducing the annual energy consumption of building by 20.85% compared to American Standard for Heating Refrigeration and Air conditioning Engineer’s (ASHRAE) standard building. Improvement: Further investigation can be carried out with different configurations in wall, roof, shading devices, air conditioning system, using daylight sensors in the periphery and also by the use of renewable energy sources.

Product lifetime, energy efficiency and climate change: A case study of air conditioners in Japan

This study proposed a modelling technique for estimating life-cycle CO2 emissions of durable goods by considering changes in product lifetime and energy efficiency. The stock and flow of durable goods was modelled by Weibull lifetime distributions and the trend in annual energy efficiency (i.e., annual electricity consumption) of an “average” durable good was formulated as a reverse logistic curve including a technologically critical value (i.e., limit energy efficiency) with respect to time. I found that when the average product lifetime is reduced, there is a trade-off between the reduction in emissions during product use (use phase), due to the additional purchases of new, more energy-efficient air conditioners, and the increase in emissions arising from the additional production of new air conditioners stimulated by the reduction of the average product lifetime. A scenario analysis focused on residential air conditioners in Japan during 1972–2013 showed that for a reduction of average lifetime of 1 year, if the air conditioner energy efficiency limit can be improved by 1.4% from the estimated current efficiency level, then CO2 emissions can be reduced by approximately the same amount as for an extension of average product lifetime of 1 year.

The effect of employing nanofluid on reducing the bore length of a vertical ground-source heat pump

In our era ground-source heat pumps are known as energy-efficient air conditioning systems. However, their high initial costs are a major obstacle to the widespread use of such systems. In this study, the effects of using Al2O3/water nanofluid as heat transfer fluid on reducing the bore length of a ground heat exchanger in a vertical ground-source heat pump are examined. For this purpose, the effective thermal conductivity and the effective viscosity of the nanofluid, which play prominent roles in the convective heat transfer, are optimized via using multi-objective Flower Pollination Algorithm. In this algorithm, the logic of the second version of non-dominated sorting is utilized to deal with the two objectives of this optimization. Then some of the best possible combinations of the thermal conductivity and the viscosity of the nanofluid, extracted from the obtained Pareto front, were used to compute the required bore length. The results were compared with the required bore length calculated using pure water as the heat transfer fluid in the ground heat exchanger. The comparison demonstrated that employing Al2O3/water nanofluid instead of water as heat transfer liquid reduced less than 1.3% of the bore length. Furthermore, investigating the reason of this low reduction in the bore length revealed that grout has the most potential to reduce the bore length among the heat transfer fluid, tubes, and grout.

Replacement or additional purchase: The impact of energy-efficient appliances on household electricity saving under public pressures

This study examined the influence of additional and replacement purchases of energy-efficient air-conditioners on power savings. We used a questionnaire survey and measured electricity use data from 339 Japanese households, collected from two city areas with different level of government-requested electricity-saving rates, namely, Osaka (10%) and Matsuyama (5%). The main findings of our study are as follows: (1) Households that purchased energy-efficient air-conditioners saved more electricity than those that did not. (2) “Additional-purchase households” showed significant energy savings, whereas “replacement households” did not. The rebound effect may negate the energy-saving effects of a new air-conditioner. (3) Altruistic attitude is associated with more active participation in power saving. (4) Households in Osaka saved more electricity than those in Matsuyama, probably because the government call to save electricity was more forceful.

Performance prediction of a new integrated central cooling plant for energy efficiency and comfort enhancement

The effective design of an energy efficient heating, ventilation and air conditioning system is reliant on multiple components. Among others, the air-handling unit cooling coil and its ability to perform efficiently directly influences heating, ventilation and air conditioning system performance. This paper investigates the energy and thermal performance of a water-cooled central cooling plant when combined with a direct evaporative cooling system located between the cooling tower and cooling coil of the air-handling unit. The evaporative cooler uses the water made by cooling tower to reduce the temperature of the 100% ambient air. The cooled air then passes through the cooling coil. This paper will demonstrate a series of mathematical models of the system components and validate them against experimental results. For this purpose, the central cooling plant is extensively equipped with a number of sensors and instrumentation devices for experimentation and data collection. The influence of the evaporative cooler on the energy saving potential and thermal comfort of the central cooling plant is evaluated. The advantages of this proposed hybrid system rests with the fact that the refrigeration effect of the chiller’s evaporator is decreased, which causes reduction of compressor power consumption. Results show that the hybrid system can provide average monthly energy savings between 11% and 24%, while enhancing the comfort level inside the building. Practical application: With traditional heating, ventilation and air conditioning systems contributing to 40% of a building’s overall energy consumption, the public’s increasing reliance on them as a necessity rather than a luxury is an issue in urgent need of attention. This together with a growing demand for cost-effective infrastructure and appliances has necessitated new installations and major retrofits in occupied buildings to achieve energy efficiency and environmental sustainability. The aim of this paper is to present a new integrated heating, ventilation and air conditioning system to meet these requirements without compromising comfort and indoor air quality.

Energy-Saving Monitoring System of Central Air-Conditioning Based on Dynamic Load

This paper introduces the components of central air-conditioning system and compares the advantages and disadvantages of the PID control and fuzzy control.Fuzzy control theory and inverter technology are combined to design the Energy-Saving Monitoring System based on the fuzzy control box of STM32F103C8T6,Siemens S7-200 PLC, ABB inverter as the hardware system and interfaces configuration of KingView as the software. Experimental results show that the water system can be variable flow controlled based on the dynamic load, central air-conditioning energy efficiency the COP has greatly improved under the premise of ensuring the comfort of central air-conditioning.

Risk preferences and purchase of energy-efficient technologies in the residential sector

Perceived risk in future energy cost savings of energy efficient technologies has been well identified as a major barrier to the adoption of such technologies. However, direct empirical evidence of the impact of consumer risk aversion on the adoption of energy efficient technologies has been limited. In this paper, we elicit consumer risk preferences using a multiple price list experiment tailored to household energy decisions. We then use the elicited risk preferences to explain consumers' self-reported historical purchase of energy efficient appliances and installation of energy efficiency retrofitting technologies. Using data from 432 homeowners from Arizona and California, USA, results show that more risk averse consumers are less likely to adopt energy efficient technologies (except for the case of energy efficient air-conditioners). In addition, the findings provide evidence that households' perceived mobility as measured by the probability of moving within five years, can amplify the negative impact of risk aversion on the adoption of energy efficiency retrofitting technologies. Overall, the results provide implications for policy makers and companies involved in promoting energy efficient technologies.

Net private benefits of purchasing eco-labeled air conditioners and subsidization policies in China

Built on a data set of 527 air conditioner models collected from an online retailer, this study investigates whether the savings that consumers realize on their private electricity bills from purchasing energy-efficient appliances compensate for the additional cost of the appliances on the market, and if not, the size of the gap between the savings and the cost. Our findings show that, except for the most energy-efficient category, the cost savings from using energy-efficient air conditioners does compensate for their higher price. Therefore, any government subsidy should be reserved for the most efficient products. For less energy-efficient appliances, the best policy may be to provide more effective information instead of a subsidy because the subsidy might attract consumers away from more energy-efficient air conditioners and result in an unwanted effect.

Recent advancements in liquid desiccant dehumidification technology

Abstract Liquid desiccant dehumidification technology is becoming increasingly attractive due to its high efficient utilization of low-grade heat and its effectiveness in dehumidification. Using this technology, energy-efficient air conditioning systems have been developed, which demonstrated superiority over the traditional vapor compression type system by allowing both temperature and humidity to be controlled independently. This paper presented a state-of-the-art review of the research and development in this field, covering the topics of heat and mass transfer models, performance evaluation of liquid desiccant dehumidification and regeneration, and technology development of dehumidifiers and regenerators as the most important components of liquid desiccant systems. Meanwhile, many detailed systems using solar energy in desiccant cooling was reported, and some new applications of liquid desiccant dehumidification were also introduced.