Air Conditioning Energy Research Articles

A study of energy performance and audit of commercial mall in hot-summer/warm-winter climate zone in China

The building energy performance improvement of large-scale public buildings is very important to release China’s energy shortage pressure. The aim of the study is to find out the building energy saving potentials of large-scale public and commercial buildings by energy audit. In this paper, the energy consumption, energy performance, and audit were carried out for a typical commercial mall, the so-called largest mall in Asia, located in a hot-summer and warm-winter climate zone. The total annual energy consumption reaches 210.01 kWh/m2, of which lighting energy consumption accounts for 30.03 kWh/m2 and the lift and elevator energy consumption accounts for 40.46 kWh/m2. It is by far higher than that of the average building energy consumption in the same category. However, the annual heating, ventilation, and air-conditioning (HVAC) energy consumption is only 87.19 kWh/m2 even though they run 24/7. It proves that the energy performance of the HVAC system is good. Therefore, the building energy savings potential mainly relies on reducing the excessive usage of lighting, lifts, and elevators.

Role of Green Coverings in Mitigating Heat Island Effects: An Analysis of Physical Models

Worldwide, governments are introducing several rules and standards in the aim of limiting the quantity of primary energy for air conditioning of buildings and supporting the use of renewable source of energy for generating thermal and electric energy to be utilized in buildings such as the European Directive on the Energy Performance of Buildings [1]. Along with these interventions, another important action takes currently place in the building sector, that is the introduction of passive structural components of the envelope, able to reduce the requirements of energy for air conditioning purposes. Among these building components, the so-called green roofs are becoming more and more interesting for designer and buildings owners. This simple technical solution, in fact, apart its effectiveness in lowering particularly the summer cooling loads, could make more attractive the shape of each single building and, when adopted on a large extension, of an entire city district, reducing the risks for urban heat island phenomena that represent a severe problem in urban contexts. In this work, a short review of the literature models for computing the energy balance of roof coverings will be proposed, with particular reference in modelling the heat exchange of a canopy.

A New Type Phase Change Energy-Saving Device for Building Field

The heat transfer enhancement in a latent heat energy storage device through embedment of copper foam (CF) is reported. The CF had a 96% porosity and the phase change material (PCM) was 25# paraffin. The CF and PCM were contained in a cuboid sample. A prototype test room was designed to numerically investigate the performance of the device. The melting and freezing process of the PCM and the day-night temperature of the room were observed. The results show that the tested totally melting time of the PCM is 8.72 hours during the daytime while the freezing time is 8.19 hours at night, and the phase change process could accomplish within 8-9 hours. The maximum temperature difference of the room is reduced 8.3°C. The room comfort could be significantly enhanced under the premise of less air conditioning energy consumption by applying the device.

The Influence of Wall Structures to Air Conditioner Energy Consumption Based on the Characteristics of Intermittent and Loculose Energy Use

In some areas like south of China, energy is used in part time of the 24 hours and part space of the buildings, that is the characteristics of intermittent and loculose energy use. The energy consumption of the air conditioner can be calculated from the transient state with the help of numerical computing method. Among different wall configurations of self-insulation, internal insulation and external insulation walls, it shows that self-insulation and internal insulation walls performs better than external insulation walls in energy saving. The energy stored by walls which account for the most part of the energy consumption can be sharply reduced in the configurations of self-insulation, internal insulation walls.

Field Test for Heat and Humidity Environment and Analysis of Air-Conditioning System Consumption

Museum has its particularity in public buildings and high research value for its thermal and humidity environment and building energy efficiency status. According to a investigation of air-conditioning systems and a test of indoor heat and humidity parameters in summer and winter for a museum in Shenyang, this article analysis its thermal environment and air-conditioning energy consumption status, draw the winter and summer indoor temperature and humidity and air-conditioning energy consumption chart, research the indoor temperature change rules and the energy consumption status of air-conditioning system in winter and summer. The results show that as air-conditioning energy consumption accounted for the main body of museum’s total building energy consumption, more energy-efficient technologies can be used to reduce the energy consumption of air-conditioning systems. And how to control the thermal environment of different types of collections in this museum, and take a consideration of energy saving, are focues of future research.

APPLICATION OF PHASE CHANGE MATERIAL TO SAVE AIR CONDITIONING ENERGY IN BUILDING

Energy saving in Air Conditioning (AC) system is quite important for climate-change mitigation, since AC system consumes around 60% of building electricity. Air conditioning technology also deals with ozone depletion problem. Chilled-water AC system needs smaller amount of primary refrigerant, so it can minimize possible CFC or HCFC (Ozone Depleting Substances) emission into the atmosphere. Latent heat transportation system applied in chilledwater system open opportunity to save energy. In the second aspect, integration of Phase Change Material (PCM) in building wall can increase heat capacity of the wall and reduce and stabilize indoor temperature. Both technologies can mutually contribute in reducing AC energy consumption. In this paper, application of some PCMs in chilled water system and wall model are reported.

Modeling of Air to Air Enthalpy Heat Exchanger

The thermal performance of a Z-shaped enthalpy heat exchanger utilizing 45-gsm Kraft paper as the heat and moisture transfer surface for heating, ventilation, and air conditioning (HVAC) energy recovery is experimentally investigated through temperature and moisture content measurements. A mathematical model is developed and validated against the experimental results using the effectiveness-NTU method. In this model the paper moisture transfer resistance is determined by paper moisture permeability measurements. Results showed that the paper moisture transfer resistance is not constant and varies with moisture gradient across the paper. Furthermore, the model is used to predict the heat exchanger performance for different heat exchanger flow configurations. The results showed that higher effectiveness values are achieved when the heat exchanger flow path width is reduced. Temperature and moisture distribution in the heat exchanger is also studied using a computational fluid dynamics package (FLUENT). To model the moisture transfer through the porous materials a nondimensional sensible–latent effectiveness ratio was developed to obtain the moisture boundary conditions on the heat exchanger surface.

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.

Heat Energy Storage Characteristics of a New Type of PCM Heat Exchange Tube

Heat energy storage characteristics of a new type of PCM heat exchange tube was researched, in which it took the traditional double-tube exchanger as the total construction foundation and phase change material(CaCl2•6H2O) was filled in the annular area between the inner tube and the outer tube. As air with different temperatures flowed through the PCM heat exchange tube, temperature measurements were carried out at the inlet and the outlet by the experimental system. The experimental results showed that, a new type of PCM heat exchange tube could store heat energy from the hot air by the phase change material in the annular area, and discharge the stored heat energy into the required fluid if necessary. Thus it has two functions of heat exchange and heat energy storage, and is mainly suitable for recovery and utilizations of heat energy in greenhouses, buildings, air conditioning and manifold industrial afterheat or waste heat.

A Study of Solar Desalination Still Combined with Air-Conditioning System

A study of solar desalination still combined with air-conditioning system is presented in this work. Combining the solar still with the air-conditioning system can increase the condensate output from the solar still while meeting the cooling load needs. The operation of the combined solar distillation and air-conditioning system, that utilized the heat rejected by the condenser and the heat sink of the evaporator, has been tested to obtain the distillate output from the solar still during the air-conditioning of a space application. Experimental work of the present system is carried out in June 2009 (summer month), in Cairo, Egypt. The present problem is tested to use the integrated system operation for already utilizing air-conditioning energy consumption; that is, meeting the hourly air-conditioning load and the daily fresh water production. The system is tested for day and nighttimes of operation of the combined system for the summer month: June 2009, Cairo, Egypt. Economic study evaluation is presented. The results show that the maximum fresh water productivity through June is 29 Liters in daytime of June 5 2009 and 37 liters in nighttime (nocturnal time) of June 3 2009. The present system more efficient in day time (8:00 AM–8:00 PM) and night time (8:00 PM–8:00 AM). Therefore, the maximum efficiency is recorded 40% for the present system in daytime, 36% in nighttime, and 25% for conventional solar still. COP increases with inside temperature (Ti), however it decreases with outside temperature (Tamb). The average cost of one liter of distillate water from the present combined system = 0.021441 (LE).

Some Villas Solar Heating and Air Conditioning System Design of Double-Source Heat Pump Programmer

This article on a villas in Langfang city, Hebei province, heating and air conditioning systems. According to the owners of the double requirement of energy saving and environmental protection to owners selection of solar energy and geothermal heat pump heating system combined. To better achieve heating and air conditioning energy saving operation of villas, the system can be run by optimizing the control scheme, time-sharing partition building heat adjustment.

Energy Consumption Analysis on Office Building Ventilation

Chongqing weather conditions as the representative, energy simulation software DesT-c Chongqing office building energy simulation analysis, simulated natural building under different ventilation conditions at room temperature, the energy consumption of building cooling load and air-conditioning system changes, with an emphasis on energy-saving effect of the night ventilation; The study showed that in Chongqing reasonable use of ventilation reduce building natural room temperature to a certain extent; Sensitive indicators of building air conditioning energy consumption than the heating energy consumption of ventilation was significantly; Night ventilation when the number of ventilators is less than 5 times / h, the energy saving effect is very significant.

Thermal Performance of Cultivation Waste of Edible Fungi as Planting Substrates in Extensive Rooftop Greeneries

As a kind of planting substrates for light virescence plant, cultivation waste of edible fungi (CWEF) has been analyzed and studied in this article. The survival condition of the kind of light green placed on rooftop had been observed in the hottest month summer which concluded a rainfall recycle. Based on the data, we could find that the kind of light green could cut down 80% heat flux into room through rooftop compared with the common rooftop, bring down obviously the temperature of the internal surface and outside surface, contribute to set up favorable indoor thermal environment. Furthermore, it can drop the air-conditioning energy consumption.

Sustainability assessment of low carbon technologies–case study of the building sector in China

In order to meet the goals of GHG reduction and sustainability in industry development, strategies are needed that are reducing GHG emissions without compromising other economic, environmental and social priorities. In this paper, existing low carbon and sustainability requirements and evaluation methods are comparatively analyzed based on an in-depth literature review. Based on this analysis, multi-attributive assessment is selected as the methodological basis of our envisaged assessment framework; modified indicators and classified values are designed accordingly. The building sector in China is analyzed as a case study. Eleven main building energy saving technologies are assessed. The results show that under the sustainability criterion, the priority order of the assessed technologies is as follows: geothermal heat pump; solar thermal; solar PV; air conditioning energy saving; central heating system energy saving; building enclosure; lighting energy conservation; electric water heater energy saving, washing machine energy saving, refrigerator energy saving (these three have equal priority), and cooking appliance energy saving. The GHG and sustainability properties of technologies are discussed by comparing the indicator scores of the two aspects. The designed evaluation method can be used in regional cases if data resources are available; and for other sectors after indicator modification.

스페이서의 재질변화에 따른 전열교환기 성능변화에 관한 연구

ABSTRACT:The importance of ventilation system is being emphasized by interest of indoor air quality. Especially, heat recovery ventilation system has attracted attention as most effective ventilation plan. Because it can reduce hazardous construction materials, indoor air pollutions, and also can reduce air conditioning energy cost. In heat recovery ventilator, the element core is the most important part. The element core is composed of liner and spacer. And liner and spacer are stacked alternately. On the Liner, heat and humidity transfer are made between supply and exhaust air. And spacer plays a role as a tunnel of exhaust and supply. In this study, we investigated and analyzed the efficiency of a heat recovery ventilator, when the spacer’s properties are changed. As a result, difference spacer’s properties affect an efficiency of heat recovery ventilator.Keywords:Heat recovery ventilator(전열교환기), Element core(전열교환 소자), Liner(라이너), Spacer(스페이서) †Corresponding author Tel.: +82-51-510-2492; fax: +82-51-514-2230 E-mail address: ycahn@pusan.ac.kr

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.

Reducing Transient and Steady State Electricity Consumption in HVAC Using Learning-Based Model-Predictive Control

Heating, ventilation, and air conditioning (HVAC) systems are an important target for efficiency improvements through new equipment and retrofitting because of their large energy footprint. One type of equipment that is common in homes and some offices is an electrical, single-stage heat pump air conditioner (AC). To study this setup, we have built the Berkeley Retrofitted and Inexpensive HVAC Testbed for Energy Efficiency (BRITE) platform. This platform allows us to actuate an AC unit that controls the room temperature of a computer laboratory on the Berkeley campus that is actively used by students, while sensors record room temperature and AC energy consumption. We build a mathematical model of the temperature dynamics of the room, and combining this model with statistical methods allows us to compute the heating load due to occupants and equipment using only a single temperature sensor. Next, we implement a control strategy that uses learning-based model-predictive control (MPC) to learn and compensate for the amount of heating due to occupancy as it varies throughout the day and year. Experiments on BRITE show that our techniques result in a 30%-70% reduction in energy consumption as compared to two-position control, while still maintaining a comfortable room temperature. The energy savings are due to our control scheme compensating for varying occupancy, while considering the transient and steady state electrical consumption of the AC. Our techniques can likely be generalized to other HVAC systems while still maintaining these energy saving features.

Application of Complex Method for Optimization of Isolated Heat Pipe Heat Exchange System

An isolated heat exchange system is added to Beijing Unicom computer room in order to reduce air-conditioning energy consumption of original computer room. The steady-state model of the heat exchange system is built using mechanism modeling method according to actual operating data and the basic principles of heat transfer process. To obtain the maximum of energy efficiency of the system, the complex method was used to search the optimal operating point. By comparing the data before and after optimization, it shows that the complex method for solving operational problems of heat exchange system is very effective.

Weather effect on thermal and energy performance of an extensive tropical green roof

This study investigated the weather effect on thermal performance of a retrofitted extensive green roof on a railway station in humid-subtropical Hong Kong. Absolute and relative (reduction magnitude) ambient and surface temperatures recorded for two years were compared amongst antecedent bare roof, green roof, and control bare roof. The impacts of solar radiation, relative humidity, soil moisture and wind speed were explored. The holistic green-roof effect reduced daily maximum tile surface temperature by 5.2°C and air temperature at 10cm height by 0.7°C, with no significant effect at 160cm. Green-roof passive cooling was enhanced by high solar radiation and low relative humidity typical of sunny summer days. High soil moisture supplemented by irrigation lowered air and vegetation surface temperature, and dampened diurnal temperature fluctuations. High wind speed increased evapotranspiration cooling of green roof, but concurrently cooled bare roof. Heat flux through green roof was also weather-dependent, with less heat gain and more heat loss on sunny days, but notable decline in both attributes on cloudy days. On rainy days, green roof assumed the energy conservation role with slight increase instead of reduction in cooling load. Daily cooling load was 0.9kWhm−2 and 0.57kWhm−2, respectively for sunny and cloudy summer days, with negligible effect on rainy days. The 484m2 green roof brought potential air-conditioning energy saving of 2.80×104kWh each summer, equivalent to electricity tariff saving of HK$2.56×104 and upstream avoidance of CO2 emission of 27.02t at the power plant. The long-term environmental and energy benefits could justify the cost of green roof installation on public buildings.

Enhancing natural ventilation, thermal comfort and energy savings in high-rise residential buildings in Bangkok through the use of ventilation shafts

Abstract This paper describes a computational fluid dynamics (CFD) analysis of the potential use of ventilation shafts in tall residential buildings in Bangkok to enhance natural ventilation and to improve thermal comfort (and thereby reduce air conditioning energy consumption). The study focused on a room with single-sided ventilation (i.e. openings in just one external wall). A ventilation shaft located at the rear of a room can raise the average air velocity across the room by greatly increasing the pressure difference between the room’s window and the shaft’s exhaust at roof level. A hypothetical room in a 25-storey residential building in Bangkok was devised to represent a typical residential unit in Bangkok. Air velocities in the predefined occupied areas of the room without and with a ventilation shaft (called reference and test room respectively) were assessed using the CFD package in the DesignBuilder modelling software, and the comfort hours during summer in both rooms were calculated based on the room’s operative temperature after they had been moderated by the elevated air velocities. Results indicate that average air velocities in the reference room were very low and insufficient to produce any cooling effect, regardless of external wind conditions, whereas air velocities in the test room were greatly enhanced compared to the reference room. Percentage comfort hours during the summer rose from 38% in the reference room to 56% in the test room, suggesting that approximately 2700 kWh of air conditioning energy savings could be achieved in the room by employing the proposed ventilation shaft.