Air Conditioning Energy Research Articles

Thermal Insulation System for Energy Efficiency

Building construction has gone for tremendous changes during the last decade. The total building architecture including construction system and external finish has improved tremendously. Now a days even residential houses are tailor made to individual requirements. As we all know with the improvement in quality of life, earnings, living style, the building construction methodology and construction materials have got modified to suit the life style of people. Previously in residential houses use of room air conditioner was a rare commodity, but now it has become very common. In fact now we find that air conditioning has become a necessity. The art of living has changed and human comfort is given a lot of importance. Buildings including residential houses hence consume lot of energy now a days. Buildings world over consume more than 40% of the Energy Generated followed by Industry (32%) and Transportation (28%). With the increase in electronic gadgets in the houses along with air conditioning and heating system energy consumption becomes enormous. It is in this context of energy consumption and human comfort the function of Thermal Insulation in buildings has become an important construction element. Thermal insulation is directly linked to human comfort and reducing energy consumption that is creating Energy Conservation.

Design of Air-Conditioning System and Elevator System Based on Intelligent Control

Air-conditioning system is the importance facilities to provide people with the comfort service, and air conditioning energy consumption accounts for about 40% of the total building energy consumption. However, the elevator system is an important transport vertical transport of high-rise buildings. Therefore, this article combines intelligent control technology with traditional air-conditioning control technology and elevator group control technology to solve the existing problem of air-conditioning control system, and greatly improve the transport capacity of the elevator system. Under the precondition of ensuring environmental comfort and improving systems, reduce the energy consumption of the system obviously.

Passive cooling by phase change material usage in construction

This work examines the significance of using phase change material (PCM) in the construction works for conservation of energy. The objective of using PCMs is that the materials help in enhancing thermal performance of buildings as these have the advantage of high storage density with small temperature swing. Among various types of PCM, rice bran distilled fatty acid – grade A (RBDFA), which is a non-paraffin type was selected considering its thermal and physical parameters, particularly its melting point that falls between human comfort temperature range. Two types of investigations, numerical and experimental, were followed in the methodology to identify the thermal performance of building during PCM usage. The results indicated that inclusion of RBDFA in construction gives positive effect in maintaining less temperature variation at indoor. Practical application: Phase change materials are substances capable of storing or releasing thermal energy as latent heat. Phase change material has wide applications in many fields, such as building envelope design to reduce ventilating and air-conditioning (HVAC) energy consumption in buildings, solar energy utilization, waste heat recovery, thermo-regulated smart textiles, and active and passive cooling of electronic devices.

Photovoltaic-thermal (PV/t) panel to minimize electrical and air conditioning energy consumption of a typical office in Beirut

ABSTRACTA combined photovoltaic–thermal (PV/t) panel is proposed to produce simultaneously electricity and heat from one integrated unit. The unit utilizes effectively the solar energy through achieving higher PV electrical efficiency and using the thermal energy for heating applications. To predict the performance of the PV/t at a given environmental conditions, a transient mathematical model was developed. The model was integrated in a heating application for a typical office space in the city of Beirut to provide the office needs for electricity, heating during winter season, and dehumidification and evaporative cooling during the summer season. To minimize the yearly office energy (electrical and heat) needs, the PV/t panel cooling air flow rate and the dehumidification regeneration temperature were determined for opimal unit operation. Thermal energy savings of up to 85% in winter and 71% in summer were achived compared to conventional systems at a payback period of 8 years for the panels.

칠드빔 유니트의 최적설계 및 성능평가 연구

Chilled Beam system is the kind of water-air system which reduces the conveyance energy for air conditioning as well as allows efficient installation and comfortable indoor environment, and has been increasingly popular mainly in Europe. To effectively install such Chilled Beam system domestically, it is necessary to develop the product considering domestic climatic condition and the requirements for air conditioning system, and particularly the way to deal with condensation during operation of cooling system in summer shall be provided. In this study, the optimal design on induction structure of Chilled Beam unit was carried out through a numerical method, and the performance test for the prototype of unit was conducted in a real-scale experiment facilities of Chilled Beam unit. While the flowrate of 1st air is 101.3 CMH, the pressure in pressure chamber is 158.7 Pa and the cooling capacities of 1st air side and 2nd air side are 498.1 W and 709.5 W respectively.

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.

Modeling the comfort effects of short-wave solar radiation indoors

Exposure to sunlight indoors produces a substantial effect on an occupant's comfort and on the air conditioning energy needed to correct for it, yet has in the past not been considered in design or in thermal comfort standards. A public online model of the effects of solar radiation on human heat gain and comfort has been developed to make this possible. SolarCal is a whole-body model for ease of use in early design. Its predictions compare closely (<0.1 PMV mean absolute error) to results of a human subject test. It can be used to determine the allowable transmittance of fenestration in a perimeter office.

Simulation Analysis on Sun-Shading Design Case of Buildings in Cold Regions

The sun-shading design was carried out based on a comprehensive building in a cold region. The reasonable building sun-shading design method in combination with the regional and facade characteristics in the cold regions is discussed, meanwhile, the unit-area refrigeration power consumption of the room and the annual building energy consumption before and after sun-shading setting are analyzed with simulation software. It is proposed that in the cold regions, designing sun-shading reasonably can reduce air conditioners energy consumption in summer, improve the indoor thermal environment and increase the indoor comfort level. This research can provides a technical reference to promote the sun-shading and building integration design and application in the cold regions.

Experimental based energy performance analysis and life cycle assessment for solar absorption cooling system at University of Californian, Merced

Traditional air conditioning and heating systems in buildings are fossil fuel based energy systems, which take the main responsible for the carbon emissions. In contrast, using solar energy for air conditioning becomes one of the promising approaches to reduce energy consumptions and negative environmental impacts from buildings. University of California, Merced built a test facility to investigate the technology: solar cooling. The solar system has 54m2 external compound parabolic concentrator (XCPC) solar collectors to drive a 23kW double-effect absorption chiller. This paper first provides the detailed energy performance analysis of the experiments conducted in August, 2012. The data collected from the experiments shows that the system could provide adequate cooling for a test facility between 11AM to 5PM in both sunny and cloudy days. The daily average collector efficiency is at the range of 36% to 39%. The average coefficient of performance (COP) of the LiBr absorption chiller is between 0.91 and 1.02 with an average of 1.0, and the daily solar COP is approximately at 0.374.In addition to the experimental investigation, a detailed life cycle economic and environmental assessment was also performed by comparing the solar systems to the conventional systems in two types of office buildings at three locations at California. Two different solar cooling system configurations were considered: (i) configuration 1 sizes the area of solar collectors and absorption chiller to meet the peak cooling demand, and uses natural gas as the only backup energy source; (ii) configuration 2 sizes the area of solar collectors and absorption chiller to meet half of the peak cooling demand, and uses natural gas as the backup energy source for the absorption chiller, while incorporates an electrical vapor compression chiller to meet the rest half of peak cooling demand. The annual performance predicts that the systems can achieve the annual solar fraction around 55–68%. And the configuration 2 achieves better life cycle economic and environmental performance than the configuration 1. Specifically, the configuration 2 can achieve lower present worth cost during the entire life span than the conventional systems. And both configuration 1 and 2 can reduce the life time carbon footprint by 35–70%.

The Effect of Urban Form and Residential Cooling Energy Use in Sacramento, California

The impact of urban form on residential space-conditioning energy use has been controversial in recent planning literature. This study empirically evaluates the association between urban form and residential energy use, focusing particularly on residential electricity use for space cooling in the City of Sacramento, California. We characterize urban form, property conditions, and demographic and socioeconomic characteristics by applying spatial metrics embedded within a geographic information system where LiDAR data effectively include each building and the surrounding vegetation. A statistical model is applied to assess the relationship between these explanatory variables and the estimated summer air-conditioning energy use. Controlling for other variables, higher population density, east—west street orientation, higher green space density, larger vegetation on the east, south, and especially the west sides of houses, appears to have statistically significant effects on reducing summer cooling energy use. This study quantifies the built environment impact on the energy demand of air conditioning and informs planners as they craft urban planning and design policies for energy conservation.

Occupant behavior and schedule modeling for building energy simulation through office appliance power consumption data mining

The occupants’ health, comfort, and productivity are important objectives for green building design and operation. However, occupant behavior also has “passive” impact on the building indoor environment by generating heat, CO2, and other “disturbances”. This study develops an “indirect” practical data mining approach using office appliance power consumption data to learn the occupant “passive” behavior. The method is tested in a medium office building. The average percentage of correctly classified individual behavior instances is 90.29%. The average correlation coefficient between the predicted group schedule and the ground truth is 0.94. The experimental result also shows a fairly consistent group occupancy schedule, while capturing the diversified individual behavior in using office appliances. Compared to the occupancy schedule used in the Department of Energy prototype medium office building models, the learned schedule has a 36.67–50.53% lower occupancy rate for different weekdays. The heating, ventilation, and air conditioning (HVAC) energy consumption impact of this discrepancy is investigated by simulating the prototype EnergyPlus models across 17 different climate zones. The simulation result shows that the occupancy schedules’ impact on the building HVAC energy consumption has large variations for the buildings under different climate conditions.

The Central Air-Conditioning Energy Saving System

At present most of the research is aimed at the end of the central air conditioning equipment, not considering the inner link between each component of the central air conditioning. In order to achieve economic operation of equipment and systems, to maximize energy saving of central air conditioning, we designed and implemented a monitoring system analysis which considered in the system more equipments linkage, multi parameter coupling, and a variety of factor. It collected energy consumption data of each device, to get the system running in typical operating conditions of the system by simulating the optimal process parameters and guide debugging critical control equipment.

Study on Energy Saving Model of Air Condition for Subway Station

In order to analyze air conditioner energy conservation of subway station quantitatively, three-dimensional numerical simulations study is conducted by using CFD theory for air distribution of subway platform, and the flow field and temperature field of the platform under different environment conditions are obtained. The orthogonal experiment method is applied to the numerical simulation analysis for human comfort under different parameters. Based on those results, the functional relationship between human comfort and the boundary conditions of the platform is produced by multiple linear regression fitting method, the order of major boundary conditions which affect human comfort is obtained. The experimental verification is also carried out, the simulation results are well coincided with experimental results. The above study provides a theoretical basis for the final energy-saving strategies.

EnergyPlus model-based predictive control within design–build–operate energy information modelling infrastructure

This study proposes a design–build–operate energy information modelling (DBO-EIM) infrastructure to allow users to deploy the design-stage building energy model for model predictive control (MPC) system in the building operation. A newly constructed office building is studied as a test bed. An EnergyPlus model-based predictive control (EPMPC) system is designed and simulated in the Matlab/Simulink environment within the DBO-EIM infrastructure. EPMPC aims at minimizing heating, ventilation, and air conditioning energy consumption while maintaining occupant thermal comfort. Compared to the baseline rule-based control system, EPMPC demonstrates a 28.9% energy reduction in one-week simulation in the heating season and 2.7% energy reduction in one-week simulation in the cooling season. The comfort constraint is met during more than 90% of the simulated hours. The study demonstrates one significant contribution of the DBO-EIM infrastructure that a design-stage EnergyPlus model can be integrated in an MPC system and the preliminary simulation results are satisfactory.

Air-conditioning energy consumption due to green roofs with different building thermal insulation

On hot days, green roofs could reduce heat flux into indoor space and air-conditioning energy use. Most thermal-benefit studies estimate energy saving based on temperature measurements. A field experiment on the roofs of two residential buildings in subtropical Hong Kong was designed to measure air-conditioning electricity consumption in relation to three factors: (1) building thermal insulation (BTI): omitted at Block 1 and installed at Block 2; (2) green-roof type: each block had a bare (Control) and two extensive green-roof plots, namely simple Sedum and more complex herbaceous Peanut vegetation; and (3) three summer weather scenarios: sunny, cloudy, and rainy. Air-conditioning electricity consumption of six vacant apartments below the experimental plots was monitored by precision energy loggers. Under all weather conditions, the unshielded Control imposes high cooling load at Block 1, but BTI at Block 2 cuts heat ingress. Sedum reduces more energy consumption than Control at both blocks, with Block 2 better than Block 1. The best effect occurs on sunny day, followed by cloudy and rainy. Sedum roof with BTI enhances thermal benefit. Without BTI, Sedum roof consumes more energy, hence the simple green roof cannot substitute BTI function. Under three weather scenarios, Peanut uses more electricity at Block 2 than Block 1, indicating the joint operation of green-roof heat-sink effect (GHE) and building heat-sink effect (BHE) at Block 2. Thicker substrate with higher moisture-holding capacity generates GHE. Added BTI material layers create BHE, with thermal resistance reduced by moisture penetration and elevated temperature. Their joint effect has raised thermal mass and thermal capacity. A rather steep thermal gradient is formed to induce thermal-insulation breaching to push heat into indoor space. At Block 1, Peanut roof can partly compensate for omission of BTI. At Block 2, however, Peanut coupled with BTI can synergistically increase cooling load. The findings can inform policies and design of green roof and associated BTI in cities with hot summer.

Effect of climatic conditions on energy consumption in direct fresh-air container data centers

To examine the use of fresh-air cooling to reduce energy consumption in container data centers (CDCs) regardless of location, a prototype fresh-air-cooled CDC was constructed in a Tokyo suburb, and a year-long operating test was conducted. Fresh-air cooling of information technology (IT) equipment does not require energy for air conditioning, and can be operated at reduced cost and energy usage. However, the characteristics of fresh-air change throughout the year, which would make it difficult to maintain inside temperature and humidity of a server room at the set points. Also, some geographic locations may be unsuitable for CDCs cooled directly by fresh-air. In addition to fresh-air cooling, CDCs at these locations have been equipped with supplemental air-conditioning units such as air conditioners to control the internal temperature and humidity. To reduce energy usage, it is desirable to use energy conservation methods such as evaporative cooling and waste heat from IT equipment as supplemental air-conditioning because they can be more feasible in compact facilities than conventional air conditioners. Although data centers (DCs) that supplement fresh-air cooling with these air-conditioning methods are currently in operation, it is not clear whether these methods can be applied in any location regardless of the climatic conditions. Depending on the application, in particular, it is necessary to set up CDCs in urban suburbs, because large access latency for users may be required. To examine these issues, a fresh-air-cooled CDC was set up and evaluated for one year in a Tokyo suburb, under different climate conditions of existing fresh-air-cooled DCs. The results confirmed that evaporative cooling and the use of waste heat from IT equipment were sufficient to support direct fresh-air cooling even when the characteristics of fresh-air were outside the range of acceptable server settings. Moreover, this CDC realized an annual energy savings of 20.8% compared with the centers that use conventional air conditioning. Furthermore, the power usage effectiveness of this CDC was found to be 1.058 from the energy usage and was compared with that of existing direct fresh-air-cooled DCs which is located in the urban suburbs. The CDC near Tokyo exhibited similar energy savings to other DCs.

The effect of building envelope insulation on cooling energy consumption in summer

Building energy consumption has increased in China with the rapid urban development and population growth of recent years. Based on the hot climate in Chongqing, two types of experimental chambers were constructed to investigate the effects of external wall insulation on energy consumption and the indoor thermal environment. An ‘energy efficient’ chamber was constructed using a thermal insulation system for the external wall, and a ‘basic’ chamber was constructed according to the general design for residential buildings of the 1980s and 1990s. Analysis of the experimental data for power consumption and the thermal environment of the two chambers showed that the indoor thermal environment of the energy efficient chamber was less affected by the outdoor environment and could be maintained at more comfortable conditions with less energy consumption than the basic chamber. The energy consumption of the energy efficient chamber was lower than that of the basic chamber, offering a savings of up to 23.5% in air conditioning energy consumption during the summer-time test period. Therefore, the results of this study demonstrate that use of an external wall insulation system can improve building energy efficiency.

The Thermal Insulation Performance of Envelope Construction of Residential Housing – A Case Study of Detached Houses in Yilan, Taiwan

This research aims to study the design and thermal insulation performance of detached houses in Taiwan through the analysis of 55 detached houses. The research shows that 85% of detached houses are built using reinforced concrete (RC) construction, and the rest mostly using lightweight steel framing (LSF) construction. The thermal insulation performance of envelope construction of RC housing is poorer than LSF housing. More than 80% of the case study sample could not meet the roof thermal insulation requirements of Taiwans latest regulations on housing building energy saving. The most commonly used thermal insulation materials are polystyrene board, glass wool and rock wool, which are nearly all applied in LSF housings for the internal thermal insulation layer or the structural body layer of envelope construction. Polystyrene board has the widest range of use, including both internal and external thermal insulation layers of the envelope construction. If improving thermal insulation performance of the common envelope construction concluded from case study samples to meet Taiwans latest regulations on housing building energy saving, of the savings on air-conditioning energy during the summer could potentially be 11.5%. However, above improvement project is not economically beneficial due to the too long payback period.

Free Cooling Potential and Technology Options for Thermal Energy Management of a Commercial Building in Bangalore City, India

ABSTRACTA significant portion of the energy consumption in buildings is the use of energy for heating, ventilation and air conditioning (HVAC) systems. Free cooling is one of the novel methods of energy saving in building air conditioning systems. In the present study, the free cooling potential for Bangalore City in India was determined by using hourly weather data for a year and also estimating the cooling load requirement for every month, considering 25 ± 3°C as the comfort level. The different technology options suitable for different months are reported in the present work. It is summarized from the study that Bangalore City does not require any mechanical cooling throughout the year. The results of the present study will be very useful for building architects and engineers to achieve the objective of zero energy buildings.

Technological Forecasting: Heat Pumps and the Synergy with Renewable Energy

The possession and use of air conditioning in the residential sector is increasing and shifting the electricity energy use peak from Winter to Summer in Europe. As the average income grows, electricity consumption is expected to be higher, especially in developing countries, as these appliances are linked to thermal comfort in dwellings. A great effort has been made, especially in Europe and China, to study and deploy technologies driven by renewable energy. Using the Delphi technique, specialists from all continents were questioned about the future technology of air conditioning for residential use in a 20-30 year future. About half of the specialists answered that vapor compression cycle will be the main technology with direct heat dissipation to outside air. The investment and operational costs were classified as the key evaluation factor together with the Seasonal Performance Factor to compare systems and technologies. Despite the low use perspective of solar thermal energy for air conditioning, it is expected to be almost a standard for DHW in a 20-30 year period.