Energy Efficient Air Conditioning Research Articles

Energy-efficient air conditioning system with combination of radiant cooling and periodic total heat exchanger

The main thrust of this paper is directed toward a novel air conditioning system that can maintain a healthy indoor environment and be energy-efficient. This system consists of a low-temperature regenerative periodic total heat exchanger, radiant ceiling-cooling coil, and conventional air conditioner. The natural cold energy of the tap water in the cooling coil provides comfortable and uniform cooling, and the desiccant-packed bed in the total heat exchanger recovers the indoor energy to handle the fresh air. The performance of each component is discussed, and the actual performance of the whole system is investigated in an office at the Taipei Water Department. The results indicate that using a radiant ceiling-cooling coil to precool the indoor environment enables the traditional window-type air conditioner to reduce two-thirds of the original operating time. In addition, the test of the whole system was conducted in the same office, and it was observed that using this system to handle the incoming air could save 13%–19% of the energy consumption per month during a year-round operation compared to directly introducing untreated fresh air.

Application of High-Strength Nonoriented Electrical Steel to Interior Permanent Magnet Synchronous Motor

We investigated the torque characteristics and the motor efficiency of interior permanent magnet synchronous motors (IPMSM), in which a rotor core consists of high-strength nonoriented electrical steel, as-cold-rolled nonoriented electrical steel, and conventional nonoriented electrical steel with various bridge widths. Furthermore, we analyzed deformation behavior of the rotor core during operation by finite element method. The motor of the high-strength nonoriented electrical steel generated greater magnet torque than that of the conventional nonoriented electrical steel. Although the high-strength nonoriented electrical steel had much higher iron loss than the conventional nonoriented electrical steel, the motor efficiency decreased only slightly. A reduction in the bridge width of the rotor core significantly enhanced the torque characteristics and the motor efficiency of IPMSM. The high-strength nonoriented electrical steel effectively suppressed the deformation of the rotor core with its excellent mechanical properties, and the suppression enabled us to reduce the bridge width sufficiently. Accordingly, a magnetically optimum rotor core design will be realized with the high-strength nonoriented electrical steel, and the performance of IPMSM will be significantly enhanced, particularly in traction motors for electric vehicles and hybrid electric vehicles and compressor motors for energy-efficient air conditioners.

New Approaches to Energy-Efficient Air-Conditioning in Electric Vehicles

New Approaches to Energy-Efficient Air-Conditioning in Electric Vehicles

LCCP Evaluation on Environmental Impact of Air-Conditioning Cold and Heat Source

Several indexes for evaluating the global warming impact, including GWP (global warming potential), TEWI (total equivalent warming impact) and LCCP (life cycle climate performance), are analyzed and investigated from the concept, contents, difference and correlation among them. LCCP is a rigorous method to calculate the cradle-to-grave warming impact of different refrigeration and air conditioning systems. The LCCP index was therein used to analyze overall greenhouse effect of three air conditioning cold and heat source plans for a public building. The results show that the total amount of equivalent CO2 emission from air conditioning heat and cold sources is up to 50,000 tons throughout the life cycle. Indirect global warming impact dominated the LCCP values of cold and heat source systems, which accounts for >96% of overall impact and caused by energy consumption both for producing refrigerant and operating refrigeration and air conditioning equipment. Therefore, increasing the energy efficiency of air conditioning and refrigeration equipment to reduce indirect global warming impact is the key to lowering A/C’ total impact on climate change. The LCCP of water source heat pump is always lower than that of conventional electric water chillers plus gas direct-fired unit, and its carbon emission reduction rates up to 32.4% as compared to the latter. So the overall impact from air conditioning cold and heat source could be effectively reduced through using renewable energy technology.

Experimental performance study of a proposed desiccant based air conditioning system

An experimental investigation on the performance of a proposed hybrid desiccant based air conditioning system referred as HDBAC is introduced in this paper. HDBAC is mainly consisted of a liquid desiccant dehumidification unit integrated with a vapor compression system (VCS). The VCS unit has a cooling capacity of 5.27kW and uses 134a as refrigerant. Calcium chloride (CaCl2) solution is used as the working desiccant material. HDBAC system is used to serve low sensible heat factor applications. The effect of different parameters such as, process air flow rate, desiccant solution flow rate, evaporator box and condenser box solution temperatures, strong solution concentration and regeneration temperature on the performance of the system is studied. The performance of the system is evaluated using some parameters such as: the coefficient of performance (COPa), specific moisture removal and energy saving percentage. A remarkable increase of about 54% in the coefficient of performance of the proposed system over VCS with reheat is achieved. A maximum overall energy saving of about 46% is observed which emphasizes the use of the proposed system as an energy efficient air conditioning system.

Modeling and experimental validation of the desiccant wheel in a hybrid desiccant air conditioning system

Modeling can be strong asset to the operation of air conditioning plants taking into account e.g. the strong dependency of local climate conditions for the operation of HVAC systems. This paper presents a validated physical model and a simplified model based on the results of the physical model for a desiccant wheel, which is the central part of a hybrid air conditioning system. The two models offer different advantages: While the physical model is complex and can be adapted flexibly to different wheel dimensions, desiccant materials or climatic conditions; the simplified model requires no knowledge of underlying equations and modeling language utilized and can be used for a first assessment of the potential of a desiccant cooling system in a certain location or for the use within online control systems. The coexistence of both models ensures that information tailored to the users' needs are made available. The validity of the physical model, and therewith the simplified model, is ensured through comparison with measurement obtained from a hybrid air conditioning system situated in northern Europe. The demonstration plant combines the advantages of a dedicated outdoor air system (DOAS) with the advantages of the common hybrid desiccant system to allow for energy efficient air conditioning in one installation. The availability of primary measurement data is extremely valuable to the process of model validation because knowledge about uncertainties and bias in measurement data unlikely to be known for secondary data can be used to understand and validate model results. A comparison of simulation results from the physical model to measurement data from the demonstration plant shows good compliance for a typical day of wheel operation after adjusting relevant model parameters.

Assessment of CO2 emission reduction and identification of CDM potential in a township

This paper presents the theoretical investigation of CDM opportunity in a township at Jaipur, India. The purpose of study is to identify and analyze the various opportunities viz., installation of solar water heater, energy efficient lighting, energy efficient air conditioners, and energy efficient submersible water pumps in desert coolers and thus achieve a considerable (65.7 %) reduction in GHG emissions. Out of the various opportunities considered, the retrofitting with solar water heater can be recommended for CDM. Though, the retrofitting with energy efficient lighting, energy efficient air conditioners and energy efficient submersible water pumps in desert coolers claimed CO2 emission reduction of 104.84, 25.92, and 36.94 tons per annum, respectively, but the only opportunity which got through CDM was retrofitting with solar water heater claiming 115.70 tCO2 (100 %) emission reductions per annum which could result into net earnings of 115.70 CERs. The simple and discounted payback period for all four project activities are also calculated with and without CDM and tax benefits.

Improvement Measures and Evaluation of Energy Efficiency of Air Conditioning

Air conditioning and refrigeration equipment are more and more widely applied, It’s energy efficiency proportion of total energy consumption is growing. To evaluate energy efficiency and apply high grade energy efficiency of air conditioning , that can bring considerable economic benefits and improve energy-saving initiative for the enterprises. This has great practical significance to realize Chinese energy-saving task. In this paper the air conditioning energy efficiency ratio(EER), seasonal energy efficiency ratio(SEER) and integrated part load value(IPLV) are proposed and analyzed, Many evalution methods are put forword to provide appropriate evaluation criteria for enterprise, and the energy-saving measures on the different assessment criteria are also put forward, It has some guiding significance to improve the efficiency of air conditioning and refrigeration equipment.

Energy efficient building services for tempering performance-oriented interior spaces – A literature review

The main focus of this paper is a literature review of analyses of high performance indoor environments which aid in the design of appropriate energy efficient Heating-Ventilation Air Conditioning (HVAC) systems. In the past, investors planned and built interiors primarily according to economic considerations. Aspects of performance-oriented interior spaces were not taken into account. Yet, to meet growing expectations and requirements, it is necessary to combine thermal comfort features and energy efficient HVAC systems. A huge amount of electricity is necessary for the operation of these systems. Overall, one-third of the final energy is consumed by the provision of space heating and hot water in Germany. More than 95% of this demand is met through the use of fossil fuel. There is, however, a great potential to reduce CO 2 emissions. Forward-thinking planning includes both the careful use of resources and the optimization of performance promoting rooms. The main emphasis in this case is on the well-being of humans, promoting their performance and hence their efficiency, and on achieving high exergetic efficiency.

Determinants of Consumers' Demand on Energy-Efficient Air Conditioners in Saudi Arabia

Consumer preferences detailed surveys are essential for the success of energy efficiency standards and Minimum Energy Performance Standards (MEPS) programs. This article presents the results of a survey that was designed to gather information about the main determinants of consumers demand on small villas air conditioners and their willingness to pay extra money to enjoy the low power consumption of energy efficient AC. The analysis of the surveys revealed that the advantage of low power consumption tends to be the least important factor that affects consumers demand on AC compared to other economic and technological factors. This suggests that energy sector in the Saudi Government should implement short and long terms campaigns to increase the public awareness of the advantages of using energy efficient air conditioners. The survey revealed also that most of the consumers are willing to pay up to 15% extra in the retail price to purchase a more energy efficient AC. This information is very helpful for AC manufacturers and decision makers in the energy sector in Saudi Arabia.

The effect of vents arrangement on the energy efficiency of a convenient store

The objective of this paper is to investigate the energy efficiency of air conditioning via the viewpoint of the vents arrangement. In the research, a real typical convenience store located in Taichung, Taiwan is selected as a case study. The computational fluid dynamic (CFD) technique is adopted to simulate the flow, thermal and humidity distribution inside the convenient store under both close and open automatic door conditions. The results show that good air conditioning vents arrangement could lead the flow going through the path which could make sufficient heat exchange with the indoor air and increase the energy efficiency. The short-path should be avoided in order for the air that goes through one inlet vent to escape through another outlet vent directly such that the fresh air could not make mixture and heat exchange with the indoor air. The present methodology of integrating CFD simulation and experiments is powerful to make fast and accurate design on the design of air conditioning vents layout. Key words: Convenient stores, computation fluid dynamics, flow distribution, energy efficiency.

Electrophoretic deposition of mesoporous silica powder synthesized by spray-drying method

Desiccant air conditioning and humidity control systems, which utilize the water adsorption/desorption by porous materials, have attracted much attention as an environment-friendly and energy-efficient air conditioning system. Micelle-templated mesoporous silicas (MPS), which have been extensively studied in recent years, are considered as the optimum adsorbent for adsorption/desorption-based air conditioning systems because of their excellent water adsorption property due to their highly ordered porous structure; i.e., a uniform nanopores with an ordered arrangement. We first reported the formation of a thick coating of MPS powder on stainless steel by an electrophoretic deposition (EPD) method and then demonstrated the preparation of the MPS coating on aluminum substrates, which has the advantages of lightweight properties and high thermal conductivity. In this study, we investigated the dispersion stability of an EPD bath, and the influence of the EPD condition on the deposition amount in detail. The EPD bath composed of spray-dried MPS powder and acetone was stable 3 min after the suspension was prepared, and the deposition amount could be easily controlled by the EPD conditions by changing the MPS powder concentration, the applied dc voltage and the deposition time. The obtained MPS thick coating had the same porous structure and adsorption properties with respect to nitrogen and water vapor as the parent spray-dried MPS powder.

An Energy Efficient Air Conditioning System using Displacement Ventilation and Chilled Ceiling for Modern Office Buildings

Thermal comfort and indoor air quality (IAQ) play a vital role in creating a pleasant and healthier indoor environment for occupants. The supply air conditions and the concentration of CO2 contaminant present in the supply air can decide the comfort level and purity of air in indoor environments. In this study, an effort was made to investigate the combined effect of a chilled ceiling and displacement ventilation (CC-DV) air conditioning (A/C) system that would possibly achieve good thermal comfort and IAQ in a proposed office building subjected to hot and humid climatic conditions. Simulation model analysis was performed under the MATLAB-Simulink environment to examine the thermal performance of the CC-DV system for different cooling capacities shared by CC and DV. Simulation results for classifying the required supply air conditions and mean contaminant removal efficiency are presented. Experimental results and existing convective correlations for floor level and head level temperatures in the occupied zone were used to validate and compare the simulation results respectively. The deviation observed between the experimental and simulation results for establishing the supply air temperature requirement was approximately ±10%. Similarly, the deviation between the simulation and the correlation results for head level temperature was ±4%. Based on the simulation model and experimental investigation performed on the CC-DV A/C system, the air supplied at 19 °C results in better thermal comfort and IAQ in indoor environments without compromising the energy conservative potential. In total, the overall energy conserved by the CC-DV system was 13.3% higher than a conventional constant air volume (CAV) A/C system operated under the same outdoor and indoor design conditions.

Energy efficient PCM-based variable air volume air conditioning system for modern buildings

This work aims at achieving enhanced energy conservation for space conditioning with the application of a new combined variable air volume (VAV)-based chilled water air conditioning (A/C) system and thermal energy storage (TES) system. The phase change material (PCM) used in this system exhibited good charging and discharging characteristics that directly helped in conserving the overall energy spent on cooling and ventilation. The present system was experimentally investigated for summer and winter climatic conditions under demand controlled ventilation (DCV) and DCV combined with the economizer cycle ventilation (ECV) to substantiate its energy savings capability. Based on the results, in the DCV and combined DCV–ECV modes, this system achieved 28% and 47% of per day average energy conservative potential, respectively, while compared to the conventional chilled water-based A/C system. Similarly, the VAV–TES system yielded an on-peak total energy savings of 38% and 42%, respectively, for the same operating conditions.

Does an energy efficiency label alter consumers' purchasing decisions? A latent class approach based on a stated choice experiment in Shanghai

In this paper we conducted a hypothetical choice experiment in Shanghai, China, to examine whether the China Energy Efficiency Label influences consumers' choices of air conditioners and refrigerators. A latent class approach was applied to observe both heterogeneities among the respondents and product brands. Our results suggested that consumers in Shanghai were well aware of the China Energy Efficiency Label and tended to pay more attention to products with such labels. In addition, air conditioners and refrigerators affixed with a hypothetical label that indicates saving in electricity bills compared with a standard model received significant preferences, which suggested that the more information manufacturers provide, the more their products would be preferred by consumers. Finally, weighted by class probability, the willingness to pay values for more energy efficient refrigerators were higher than those for more energy efficient air conditioners, implying that Shanghai consumers have greater incentive to pay more for appliances they use more frequently.

Actuality and Development of Pivotal Energy-saving and Emission Reduction Technology on Refrigeration and Air-condition

China has an increasingly severe energy situation. The rapid development of refrigeration and air-condition industry brings huge energy consumption and serious environmental problems. Based on energy conservation and discharge reduction, analysis of controlling and reducing energy consumption by formulating China's refrigeration and air-conditioning energy efficiency standards is presented. Moreover, because of ozone layer depletion and global warming, international response to environmental problems and refrigerant alternatives also are introduced. Natural refrigerants, especially CO2, will be future trends for environmental protection. Therefore, developments of CO2 refrigeration technology are introduced finally.

Feasibility study of capturing carbon credit benefits in an academic institution: A case study

The CDM potential in an academic institution hosting 2500 students is analyzed through the introduction of renewable energy technologies (Solar Water Heater, Solar Steam Cooking) and adoption of energy efficient technologies (Compact Fluorescent Lighting, Energy Efficient Air Conditioners). The baseline emission has been calculated for each technology. A detail investment analysis has been carried out for each of these measures. The impact of revenue generated by selling carbon credits through the clean development mechanism (CDM), on the economic viability of the project activity is analyzed along with sensitivity analysis. Out of the four cases analyzed, energy efficient lighting and energy efficient air conditioners do not require CDM benefits for their viability hence they fail to prove the additionality. Solar steam cooking having negative value of IRR does not pass the additionality criterion for CDM. The solar water heater generating 48.13 tCO 2/year is identified as the candidate CDM project. The total amount of CO 2 that can be saved from emitting to the atmosphere by employing the renewable and energy efficient technologies is 311.34 tCO 2/year. The CERs generated by this project are insufficient to cover the validation/ verification and registration expenses. For converting the CDM potential into reality, bundling of the similar activities with nearby academic institutes can be considered.

Adaptive optimal control of seawater cooling system in centralized air-conditioning system

Seawater is usually used to cool down condensers in centralized air-conditioning systems in Hong Kong where the fresh water is very scarce.Optimal control is among the means to improve energy efficiency in air-conditioning system.This paper presents an adaptive optimal control strategy to optimize the seawater pressure set-point of variable-speed seawater pumps aiming at minimal energy consumptions.This optimization is achieved by adjusting the pressure set-point according to the estimated derivative of the total power with respect to seawater pressure differential.This strategy is validated using simulations.The tests show that significant saving in the overall energy consumption of the chilling system can be achieved by properly resetting the pressure set-point only.

High-Efficiency Rooftop Air Conditioners: Small Commercial ACs Could Add Up to Big Energy Savings

ABSTRACT This article describes a technology procurement conducted by the U.S. Department of Energy, the Pacific Northwest National Laboratory (PNNL), and the Defense Logistics Agency to increase the availability of energy-efficient, packaged unitary “rooftop” air conditioners. The procurement encourages air conditioner manufacturers to produce equipment that exceeds federal energy efficiency standards by at least 25 percent at a lower life-cycle cost. Program developers have also sought to aggregate market demand by organizing groups of large-volume buyers of air-conditioning equipment. A cost estimator tool developed by PNNL to help consumers determine the cost-effectiveness, based on local climate conditions, of purchasing energy-efficient air conditioners for their own facilities also is described.

強制空冷機器を収容した電算機室の高効率空調方式に関する研究

A new energy-efficient air conditioning system in proposed for a computer room with high heat generating equipment where forced air cooling air volume is prescribed. In the proposed air conditioning system, conditioned primary air from the AHU is reduced in accordance with the heat load, while insufficient cooling air volume is compensated by induced secondary room air. Reduction of conditioned air saves fan capacity and consequently improves efficiency of the AHU. This paper describes an on-site survey of a conventional air conditioning system, as well as modeling of air distribution around equipment, and validation of the new air conditioning system based on field experiments.