Energy Efficiency Of Air Conditioners Research Articles

Soft-Sensor Modeling of Temperature Variation in a Room under Cooling Conditions

Non-uniform temperature distributions in air-conditioned areas can reduce the energy efficiency of air conditioners and cause uncomfortable thermal sensations for occupants. Furthermore, it is impractical to use physical sensors to measure the local temperature at every position. This study developed a soft-sensing model that integrates the fundamentals of thermodynamics and transport phenomena to predict the temperature at the target position in space. Water experiments were conducted to simulate indoor conditions in an air-conditioning cooling mode. The transient temperatures of various positions were measured for model training and validation. The velocity vectors of water flow were acquired using the particle image velocimetry method. Correlation analysis of various positions was conducted to select the input variable. The soft-sensing model was developed using the multiple linear regression method. The model for the top layer was modified by the correction of dead time. The experimental results showed the temperature inhomogeneity between different layers. The temperature at each target position under two initial temperatures and two flow rates was accurately predicted with a mean absolute error within 0.69 K. Moreover, the temperature under different flow rates can be predicted with one model. Therefore, this soft-sensing model has the potential to be integrated into air-conditioning systems.

Laboratory load-based testing and performance rating of residential heat pumps in heating mode

Improving the energy efficiency of air conditioners and heat pumps is crucial for reducing the effects of continuously rising energy demands for space conditioning. One of the effective and tested approaches for achieving this goal has been to set energy efficiency benchmarks based on minimum energy performance standards which drive technological innovation and implementation in the market. For heat pumps, a testing and rating procedure that estimates equipment seasonal performance from laboratory measurements forms the technical basis for these standards. However, with current residential heat pumps rating standards, significant differences have been observed between efficiency measured in the lab and actual operational performance in field applications. One of the reasons for this is that with current rating approaches, the test unit native controls are overridden when measuring performance in the laboratory. As an alternative, a load-based testing approach has been developed that captures dynamic interactions of the integrated controls, equipment and building with the goal of better-representing field application conditions. In this paper, a load-based testing approach previously developed for air-conditioners is extended for heat–pump heating-mode and demonstrated for a variable-speed system. Climate-specific heating seasonal performance ratings were determined by propagating the test results through a temperature-bin method.

Experimental Investigation of Energy Efficient Room Air Conditioners for Mini-Stores

An experimental investigation of energy efficiency room air conditioners for the mini-stores was presented and illustrated in the paper. The experiment has been carried out in two well-insulated rooms with two different compressor technologies (fixed-speed and inverter) and essential equipment in a laboratory located at the School of Heat Engineering and Refrigeration (Hanoi University of Science and Technology). The authors conducted the test with three different heat load categories and weather conditions to examine the energy efficiency based on several factors such as room temperature and power consumption of air conditioner from records. Results show the significant effect of various aspects on the efficiency and the behaviour of air-cooled air conditioners including the indoor heat load and the outdoor temperature. The results also suggest a suitable cooling capacity choice that helps improve the energy efficiency of air conditioners besides the technical data such as CSPF (or SEER) and power consumption.

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.

Energy Efficiency of Air Conditioners in Developing Countries: A Malaysian Case Study

Growing demand for air conditioner (AC) in developing countries has hit an alarming point. Enforcing higher efficiency standards for cooling appliances is one of the easier initiatives that governments can implement to reduce energy consumption and emissions of potent greenhouse gases. Malaysia has adopted the Minimum Energy Performance Standards (MEPS) in 2013 to regulate the energy performance of five common household appliances including ACs. This work sheds light on the overall improvement of AC’s energy performance after MEPS implementation. A rigorous data collection exercise was conducted to build a comprehensive sales and technical database of MEPS-compliant ACs covering the years 2013-2015. In 2015, the average energy efficiency ratio (EER) of ACs sold in the local market is 3.4, and the cumulative electricity saving and CO2 emission reduction after MEPS implementation are 1,764 GWh and 1,178 ktCO2eq respectively. The results from this study will contribute significantly to the review of the effectiveness of MEPS implementation in developing countries.

Enhanced condensation heat transfer in air-conditioner heat exchanger using superhydrophobic foils

Air-conditioners have the highest energy consumption among the household appliances because of the improved thermal resistance by the filmwise condensation in summer and frosting in winter on the surface of hydrophilic foils of condensers. The wet foils are also easy to adsorb dirts and reproduce bacteria, further affecting people health in the room. Here, through chemical oxidation and subsequent chemical modification, we fabricated a novel air-conditioner fin-tube heat exchanger with superhydrophobic foils, which showed high performance in self-cleaning, anti-condensation, anti-frosting, anti-corrosion and environment stability, promising a good candidate for improving energy efficiency of air-conditioners in future. Enhanced condensation heat transfer were demonstrate on indoor and outdoor condenser in summer and winter, respectively. The results of testing revealed that the cooling capacity and heat transfer coefficient from superhydrophobic Fan Coil Unit (indoor condenser) increasing over 8 and 2% than conventional hydrophilic one under rated output working conditions. Moreover, the superhydrophobic outdoor condenser under the condition of frosting has higher energy conversion (over 85%) than the conventional hydrophilic one after 60 min.

The role of technology, product lifetime, and energy efficiency in climate mitigation: A case study of air conditioners in Japan

This study analyzed the impact on the life-cycle CO2 emissions derived from a specific durable good (i.e., household air conditioners in this study) of industrial technology changes, product lifetime changes, and energy efficiency improvements. I proposed a comprehensive structural decomposition analysis including two factors of average lifetime and energy efficiency trend of household air conditioners and applied the decomposition method to the Japanese environmental input-output tables of 1990, 1995, 2000, and 2005. The empirical results show that “Household air-conditioner sector” itself contributed to reducing life-cycle CO2 emissions derived from household air conditioners, while other sectors such as “On-site power generation sector” and “Retail trade sector” contributed to increasing life-cycle CO2 emissions derived from household air conditioners. I also conducted combined scenario analysis about reduction potential of product lifetime and energy efficiency of air conditioners and the results showed the reduction rate of energy efficiency necessary for maintain CO2 emissions in 2005 at 1990 level on each average lifetime scenario. (e.g. if average lifetime of air conditioners is shortened by 1 year, energy efficiency of air conditioners have to be further improved by 20.6% from current level.

Consumer valuations of energy efficiency investments: The case of Vietnam's Air Conditioner market

Research on the energy-efficiency gap in developing countries remains very scant. In this study, we apply the hedonic price model to investigate how Vietnamese consumers value the energy efficiency of air conditioners (ACs). We assume that the energy efficiency of ACs in the Vietnamese market improves to that of ACs in the Japanese market. Then, we calculate the payback period by dividing the capital cost to improve the energy efficiency by the annual electricity cost saving. We show that the initial investment cost can be recovered in a short time. In addition, we calculate the implicit discount rate to show how Vietnamese consumers value energy efficiency investment. We find that the implicit discount rate in Vietnam's AC market is much higher than the rates found in studies on developed countries. Hence, consumers in developing countries place much lower value on energy efficiency investment than consumers in developing countries, even though purchasing energy-efficient appliances offers opportunities to save substantial amounts.

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 life cycle rebound effect of air-conditioner consumption in China

Governments worldwide are attempting to reduce energy consumption and environmental pollution by confronting environmental problems and adopting more energy-efficient products. However, because of the rebound effect, energy-saving targets cannot always be fully achieved, and sometimes greater energy consumption is generated. Research on the rebound effect from the perspective of industrial ecology considers not only direct energy consumption but also its life cycle negative impacts on the environment with China’s rapid economic development and simultaneously improving quality of life, the ownership of room air conditioners (RACs) has increased more than three hundred times, and air conditioners’ energy consumption has increased one thousand times over the last twenty years. The Air Conditioner Energy Efficiency Standard is one of the most important measures in China for reducing the amount of energy consumed by RACs. This paper introduces a life cycle based method to estimate the rebound effect of Chinese RACs consumption. This model provides a product’s life-cycle view to assess the rebound effect, considering the contribution of both producer and consumer. Based on the established life cycle rebound effect model, we compared urban household RAC consumption behaviour before and after the launch of the Air Conditioner Energy Efficiency Standard. A rebound effect in RAC consumption was found that there was a longer daily usage period in the household as air conditioner efficiency levels improved. The life cycle rebound effect of household air-conditioner consumption was calculated to be 67%. The main conclusion obtained from this study is that policies and regulations should consider the rebound effect when encouraging households to alter their energy consumption patterns.

Beyond the end-consumer: how would improvements in residential energy efficiency affect the power sector in Saudi Arabia?

Abstract Energy efficiency in buildings has garnered significant attention in Saudi Arabia. This paper outlines the potential effects of higher residential efficiency on electricity load profiles in the Kingdom. It further presents the associated benefits that could have been realized by the local utilities in 2011. To perform the analysis, we designed an integrated methodology in which an engineering-based residential electricity demand model is used within an economic equilibrium framework. The modeling approach allows us to capture the physical interactions arising from higher efficiency and the structural changes that could occur in the economy beyond the end-consumers. Raising the average air-conditioner energy efficiency ratio (EER) to 11 British thermal unit (BTU)/(Wh) from its 2011 average would have saved 225,000 barrels/day of crude oil in electricity generation. Alternatively, increasing the share of insulated homes from 27 to 64 % would have allowed the power sector to lower its use of the fuel by 158,000 barrels/day. Combining both measures in a single simulation yields incremental yet not additive reductions. All alternative scenarios reduce costs to the utilities and improve the average thermal efficiency for the electricity generated. The studied efficiency options shift the load curve downward during the peak load segment when the least efficient turbines would be used. We additionally show how efficiency improvements in end-uses can affect the decisions of other sectors in the economy.

Integrating Domestic Air Conditioner with Solar Water Heater of the Development of an Energy-Saving Heating System

The current thesis proposed the integration of air conditioners that exhaust heat with solar energy to enhance the overall efficiency of thermal energy conversion. The analysis of thermal storage tanks of different volumes revealed that a two-ton air conditioner operating for an hour produced double energy than normal sunshine for a day. With thermal storage tanks of fixed volume, the integration of air conditioners of different tons with solar energy indicated that air conditioners of less tons produced faster and more efficient energy conversion. Therefore, the current thesis proposed that the modification of condenser in domestic air conditioner into water-cooled condenser not only enhanced the energy efficiency of air conditioners but also increased hot water supplies since hot water from air conditioners could be integrated into solar water heaters. By doing so, energy conservation and carbon reduction could be achieved.

Effectiveness of Energy Efficiency Standards and Labeling Requirements: The Case of Air Conditioners in Japan, Thailand, China and India

This chapter evaluates whether standards and labeling programs aimed at improving the energy efficiency of electrical appliances have been successful at achieving their goals. Standards and labeling programs work to reduce energy consumption by (a) influencing consumers’ choice of appliance and (b) inducing manufacturers to improve the energy efficiency of their products. In Most middle- and high-income countries first introduced mandatory minimum energy performance standards (MEPS) and/or multi-grade labeling and then added high energy performance standards (HEPS) that upgraded those standards. Analysis of product-level data for the air conditioner markets in Japan, Thailand, India and China yielded the following findings: (1) Standards and labeling programs appear to be effective at changing energy efficiency levels in the marketplace. There has been a clear improvement in the energy efficiency of air conditioners, measured by such indexes as coefficient of performance (COP), energy efficiency ratio (EER) and annual performance factor (APF) in Japan. (2) More energy-efficient products are priced higher in Japan and India. (3) Japan succeeded in reducing electricity consumption from air conditioners by one-half, but neither Thailand nor China succeeded in curbing electricity consumption. Appropriate fine-tuning of policy instruments is necessary to effectively reduce electricity use by air conditioners. An example is the introduction of a rule-based mechanism to revise minimum efficiency standards regularly. Cross-country harmonization of regulatory methods, such as methods to measure energy efficiency and revise efficiency standards, may also be beneficial.

Cooling energy consumption and reduction effect for residential buildings in South East Queensland, Australia

This paper presents a bottom-up approach to quantify the regional cooling energy consumption in South East Queensland (SEQ), one of the fastest growing regions in the last decade in Australia. This study focuses on addressing the impact of climate change, economic and population growth. This study investigates the sensitivity of regional cooling energy consumption to several key parameters: air temperature, number of households, cooling-system penetration rate, energy efficiency of air conditioners and ceiling insulation. The results show that the four major cities (Brisbane, Gold Coast, Moreton Bay and Sunshine Coast) will constitute 73% of the total SEQ residential cooling energy in 2030 in comparison with their share of 77% in 2005. Due to the anticipated strong growth in the number of households, Ipswich and Scenic Rim will have an energy use increase of 145% and 124%, respectively, for the 25-year period. With a 1°C temperature rise between 2010 and 2030, the SEQ cooling energy consumption in 2030 will be 80% more than that in 2005, compared with 33% without temperature rise. We found from sensitivity analysis that installing ceiling insulation is more effective for reducing residential cooling energy than increasing the energy efficiency of cooling systems or decreasing the penetration rate of cooling systems. The results are useful for the decision makers to formulate future energy policies of the region.

Integrated Application of Renewable Energy Technology in Building Energy Efficiency

During the average fifty or sixty years of building lifecycles, large amounts of energies are consumed at all stages, from the production of building materials, transportation for project constructions, daily use, and maintenance to demolition, in particular, the daily energy consumption of air-conditioners, lighting, and elevators. The main “energy saving indicator,” from among nine green building indicators, evaluates the electrical power consumption of air conditioners and lighting. The main evaluation items are building envelope heating load ratio, air-conditioner energy efficiency ratio, and lighting energy saving ratio. During evaluation, the promotion and application of renewable energy is encouraged by incentive factors. The development and use of renewable energy technology may improve energy utilization efficiency, maintain a balance of supply and demand, and reduce environmental pollution, thus, this study developed a indoor personal office system with 1KW solar energy and a 500W proton exchange membrane fuel cell (PEM fuel cell) as the power source, which is composed of LED indoor lighting, air fan, LED table lamp, notebook computer, printer, and acoustic equipment. Under continuous operations of 24h, this office system will generate 12kwh of electricity, which reduces 7.656kg of carbon dioxide output. If continuously operated for 1 year, it will generate 4,320kwh electricity, which reduces 2,756.16kg of carbon dioxide output. In addition, the side product water can be recycled as landscape water.

Estimation of Cooling Energy Reduction by Utilizing Cross-Ventilation in Detached Houses, within the Japanese newly introduced Energy Regulation - Evaluating Energy Consumption for Different Uses

The reduction of carbon dioxide emission due to energy consumption in the household sector is an urgent task, worldwide. As a measure to respond to the task, a new regulation has just been enforced since April 2009, in Japan. This regulation evaluates the energy performance of detached houses by estimating the primary energy consumption for different uses, namely, heating, cooling, ventilation, domestic hot water and lighting.Especially in mild or hot climates, it has been frequently claimed by practitioners that the regulation, which is heavily focused on insulation performance, is not enough and broader aspects should be equally evaluated. The effectiveness of cross ventilation in reducing cooling energy is one of these aspects. However, there have been difficulties to overcome in predicting the effectiveness of cross ventilation on cooling energy reduction. Among such difficulties are the decrease of the discharge coefficient of openings with inclined airflow, variation of the wind pressure coefficient depending on surrounding conditions, etc., occupants’ window opening behaviour and actual energy efficiency of air conditioners depending on their output and outdoor conditions. By referring to the results from experiments and observations on cross ventilation and air conditioners, the authors have proposed a solution for the Japanese new energy regulation on how to predict cooling energy consumption, taking the above factors into consideration. Even though there are still problems to be solved, the solution by the authors, shown in this paper, can be a guidepost to a more reasonable evaluation of the energy performance for cooling in buildings, as well as to a more reasonable design practice for windows and openings on the partition walls.

Estimation of the Effectiveness of Cross Ventilation as a Passive Cooling Method for Houses

The effectiveness of various methods for saving energy and improving the indoor environment in buildings depends upon the building conditions under which those methods are applied. To find better design solutions in such situations, designers or building owners need to make reference to quantitative information so that they can choose appropriate methods, which fit to the design conditions. These include data such as climate, surrounding environment, construction, occupants' lifestyle and economic constraints. Passive cooling by natural ventilation is one of the promising methods to achieve thermal comfort, but its effectiveness should be clarified, especially in relation to saving energy. In this paper, an integration of research outputs on cross ventilation is made in order to determine the reduction of cooling energy that can be achieved. This is undertaken by considering a series of questions and, by reviewing existing knowledge, finding appropriate answers. Existing research outputs include the prediction of wind pressure and discharge coefficients as well as the behavioural model of window opening by occupants, the application of coupled heat and airflow simulation tools, and the actual energy efficiency of air conditioners under use. Through such integration it is possible to estimate the sensitivity of cooling energy resulting from errors in the discharge coefficient and the wind pressure coefficient and to determine the necessary accuracy for those two parameters.