Air-conditioned Buildings Research Articles

Special issue on “Optimal design and operation of energy systems”

Special issue on “Optimal design and operation of energy systems”

Performance characteristics of desiccant rotor using metal organic framework material

A desiccant rotor is often adopted for dehumidification applications, owing to the increased importance of humidity control and energy saving in air conditioning and ventilation systems for buildings. In previous studies, silica gel, zeolite, and silica composites have been widely used in the desiccant rotor. However, it is difficult to further improve the dehumidification performance of a conventional desiccant rotor, owing to the inherent limitations of the desiccant material. In this study, a desiccant rotor using a metal organic framework (MOF) material was proposed and manufactured to improve the dehumidification performance under various operating conditions. The dehumidification and regeneration performance of the MOF desiccant rotor were measured and analyzed by varying the temperature, humidity, volumetric flow rate of the process air, and temperature of the regeneration air. Furthermore, the performance of the MOF desiccant rotor was compared to that of a conventional silica composite desiccant rotor. The MOF desiccant rotor showed 53% lower sensible energy ratio and 139% higher specific moisture removal capacity than the conventional desiccant rotor. In addition, empirical correlations were developed for performance predictions for the MOF desiccant rotor.

Odor from Building Air Conditioners: Emission Characteristics, Odor Compounds and Influencing Factors

The odor generated by air conditioners is an important factor influencing the perceived air quality in buildings. In this study, different types of air conditioners and air filters were investigated to study the level of odor emission related to the operation state of the compressor, to identify the odor compounds and to analyze the cooling setpoint temperature on emitted odor intensity. Results show that the odor from constant frequency air conditioner use is periodic and stronger than that from variable frequency air conditioner use due to the different operation strategies of the compressor, which affect the evaporation of condensed water on the surface of the cooling coil. Ethyl acetate, acetic acid, 2-ethyl-1-hexanol, acetaldehyde, hexanal, nonanal, toluene and n-hexane are identified as odor compounds by Odor Active Value (OAV), Gas Chromatography/Olfactory/Mass Spectrometry (GC/O/MS) and Flavornet methods. The higher cooling setpoint temperature would lead to stronger odor, due to greater release of hydrophilic odorous compounds from condensed water. In our opinion, reducing the residual condensed water in air conditioners may be the key to control odor emission before purification.

Air conditioning system analysis for two floors electronic industrial building size 40 X 25 X 10 meters at PT. CI. in Jakarta

<div><p>Air fresheners or AC (Air Conditioning) systems are increasingly becoming a necessity for urban communities and the industrial world in Jakarta. AC functions to cool industrial rooms, offices and homes. The PT CI Electronic Industry Building, has not yet installed an air conditioning system so that the production room is not comfortable for its employees. The purpose of installing air conditioning in the industrial building is to increase employee comfort and productivity. In installing an air conditioning (AC) system in the industrial building, design data and cooling load analysis are required. Therefore it is necessary to study the design of industrial air conditioners at PT CI by calculating the cooling load, calculating the required electrical power in order to determine the size and type of air conditioner needed. The research methodology starts from determining industrial building data, such as what tools and machines are in the room, the area of the room and the room wall materials, then analyzing the cooling load, determining the power of the cooling machine and determining the cooling system used. From the results of the cooling load analysis in the Electronics Industry building at PT CI, the total load on floors 1 and 2 was 709 kW, or 201,6 TR, including sensible load: 705.83 kW and Latin load: 3.03 kW. The refrigerant used by the AC R 134a engine. The compressor power is 356 HP. Medium large COP 2.8. The cooling system chosen is the central air conditioning system.</p></div>

Energy efficiency evaluation method of refrigeration and air conditioning in intelligent buildings based on improved entropy value method

In order to improve the accuracy and precision of the evaluation of cold source energy efficiency, this paper proposes an evaluation method of cold source energy efficiency of refrigeration and air conditioning in intelligent buildings based on the improved entropy method. On the basis of analysing the energy efficiency ratio composition of refrigeration and air conditioning system, the calculation process of energy efficiency ratio is refined by using refrigeration energy efficiency transport function. Then the AHM improved entropy method was used to optimise the weight ratio process, and the efficient and accurate evaluation of the cooling source energy efficiency of refrigeration and air conditioning was completed by adjusting the weight ratio. The experimental results show that the average evaluation accuracy of the proposed method is 95.9% and the average evaluation accuracy is 96.3%, which proves that the proposed method achieves the design expectation.

Cycling durability and potentiostatic rejuvenation of electrochromic tungsten oxide thin films: Effect of silica nanoparticles in LiClO4–Propylene carbonate electrolytes

Electrochromic (EC) technology allows control of the transmission of visible light and solar radiation through thin-film devices. When applied to “smart” windows, EC technology can significantly diminish energy use for cooling and air conditioning of buildings and simultaneously provide good indoor comfort for the buildings’ occupants through reduced glare. EC “smart” windows are available on the market, but it is nevertheless important that their degradation under operating conditions be better understood and, ideally, prevented. In the present work, we investigated EC properties, voltammetric cycling durability, and potentiostatic rejuvenation of sputter-deposited WO 3 thin films immersed in LiClO 4 –propylene carbonate electrolytes containing up to 3.0 wt% of ∼7-nm-diameter SiO 2 nanoparticles. Adding about 1 wt% SiO 2 led to a significant improvement in cycling durability in the commonly used potential range of 2.0–4.0 V vs. Li/Li + . Furthermore, X-ray photoemission spectroscopy indicated that O–Si bonds were associated with enhanced durability in the presence of SiO 2 nanoparticles. • Electrochromic properties, durability, and potentiostatic rejuvenation of W oxide thin films are investigated. • The aim was to study the effect of ∼7-nm-diameter silica nanoparticles in LiClO 4 –propylene carbonate electrolytes. • Film degradation was investigated in range between 2.0 and 4.0 V vs. Li/Li + . • Adding about 1 wt% SiO 2 led to a significant improvement in cycling durability. • O–Si bonds were associated with enhanced durability in the presence of SiO 2 nanoparticles.

Design and experimental study of an outdoor portable thermoelectric air-conditioning system

This study aims to identify suitable microclimate cooling systems to reduce heat stress and improve human thermal comfort. A portable thermoelectric air conditioner was developed for local cooling of the human body. Effects of core components thermoelectric refrigerators (TECs), hot end heat dissipation, intake flow and cold end heat exchangers on TEAC performance. It is shown that, remarkably, this operating voltage can be distinguished from the optimal voltage for the maximum operational performance of TEAC. When the TECs operating voltage is 4V, the maximum COP is 2.2, and the best operating voltage is 10V, the maximum cooling capacity is 26.7 W (COP=0.92). Simulation data show that the area of the diffuser can effectively control the contact between the air and the cooling surface with an error of less than 10% compared to the experimental results. The fans and radiators attached to the hot side of the TEM play an important role in keeping the temperature difference on the hot side of the TECs as small as possible, by dissipating the heat generated on the hot side of the TEM to the external environment. In addition, the experimental refrigeration capacity is greater than 26.7 W and the new system has ultra-quiet operation at large refrigeration capacity, which has promising potential for advanced refrigeration, building air conditioning, ventilation systems and other applications. • Thermalelecrtic air conditioner (TEAC) can achieve a cooling capacity of 26.7W and a cooling coefficient of 0.92, enabling local cooling of the human body. • The maximum cooling capacity of thermoelectric refrigerator varies nonlinearly with the surface area and height of thermoelectric leg. • The increase of cooling capacity decreases with the increase of intake flow rate. • Increasing the strength of heat dissipation at the hot end of the thermoelectric cooler has a larger effect on the TEAC cooling capacity than on the cooling coefficient.

Cooling air in contact with natural sources of cold

Issues of microclimate mitigation in Uzbekistan during the summer period require urgent resolution. It should be noted that currently there are very few research, as well as practical recommendations related to the formation of a favorable microclimatic environment in cities with a hot climate. The simplest and most economical way of cooling, in dry and hot climates, is the evaporative cooling of a dry air stream. One of the possible ways to increase the efficiency of the system is the use of night evaporative cooling of water, followed by its accumulation for daytime cooling in heat-insulated batteries. The conducted experiments testify that rather simple and cheap natural sources of cold can be used along with machine cold sources for air conditioning of residential buildings in Uzbekistan.

Energy efficiency evaluation method of refrigeration and air conditioning in intelligent buildings based on improved entropy value method

Energy efficiency evaluation method of refrigeration and air conditioning in intelligent buildings based on improved entropy value method

A Control Framework to Enable a Commercial Building HVAC System for Energy and Regulation Market Signal Tracking

Commercial buildings are great demand response resources in the energy and regulation markets. Many commercial building heating, ventilation and air conditioning (HVAC) systems are composed of a chiller producing chilled water, and multiple Air-Handling Units (AHUs) distributing cooled air to thermal zones. Demand response of such systems has the potential to closely track energy and regulation market signals. However, existing control methods are mostly focused on fan control, neglecting the impact of the air loop fan control on the power consumption of water loop pumps and chillers. This paper presents a complete modeling of a commercial building HVAC system consisting of chiller, water pump and multiple AHUs, and develops a two-level control to follow five-minute energy market signals and four-second frequency regulation signals. The first-level coarse control provides commands for both water and air loop variables, the second-level fine control adjusts the fan commands while maintaining the water loop inputs within the five-minute control period. As a result, the water-loop power serves as a basis to track energy market signals and the air-loop fan control can be adjusted flexibly for frequency regulation. A high-fidelity model in Dymola is built to validate the model and control. The validation is conducted through co-simulation between Matlab and Dymola model via the Building Controls Virtual Test Bed (BCVTB). The simulation results show significant tracking improvement with the proposed two-level control framework.

Research on Thermal and Humidity Environment of Cultural Relics Exhibition Room

In order to meet the needs of humanistic education, museum buildings have developed vigorously in recent years. The protection and display of cultural relics is an effective way to continue historical information, which has important social and cultural significance. During the design and operation of the building air conditioning system, both the thermal and humidity environment of the cultural relics exhibition room should be responsible for the safety of the displayed cultural relics and the thermal comfort of visitors should be considered. In this paper, the indoor thermal and humidity environment of a cultural relic exhibition room in Beijing was measured, and the indoor air velocity distribution and temperature and humidity distribution were obtained. The results show that the thermal and humidity environment of the cultural relics exhibition room is better, but the indoor temperature of the exhibition room is lower, which still has great energy saving potential. It needs to be improved in the future engineering practice to achieve double optimization of comfort and energy saving effect. In order to achieve accurate control of the indoor thermal and humidity environment of the cultural relics exhibition room, we built a data collection for thermal environment parameters and air quality, which is used for monitoring and data collection of the cultural relics exhibition room.

Room Temperature Dynamic Control and Energy-saving System

According to statistics, the energy consumption of building air conditioning system operation accounts for about 50% of the energy consumption in the building operation phase. Therefore, reducing the energy consumption of building air conditioning systems is of great significance for building energy conservation. The traditional air conditioning system sets a constant temperature during operation and then adopts the PID control method to gradually approach this target value. This method does not take into account dynamic factors such as the building environment, personnel activities, and startup equipment rates, resulting in a large waste of energy consumption and poor comfort. This paper proposes a solution combining the Internet of Things and a heuristic optimization algorithm, in which the Internet of Things is responsible for collecting real-time parameters, and the optimization algorithm is responsible for solving the optimal control strategy, to realize intelligent real-time dynamic adjustment of indoor temperature. By comparing the actual operation results, it can be seen that the control system can reduce power consumption by about 10% and increase user satisfaction by about 8%.

Effect of Office Design Characteristics and Anthropometrics on Thermal Comfort in Malaysian Universities Air-Conditioned Buildings

Apart from indoor environmental and personal factors, contextual factors have significantly influenced several thermal comfort studies. In air-conditioned spaces, thermal comfort is conveniently attainable by adjusting the temperature settings, but indoor design elements might alter thermal perceptions and provide adaptive opportunities. This study examines the influence of office design characteristics and anthropometrics on thermal comfort parameters and perceptions. Nineteen university offices in Kuala Lumpur and Shah Alam, comprised of twelve shared and seven private spaces, were investigated, and 628 responses were collected from 42 participants with even gender distributions. The results showed that room occupancy and size were statistically significant with Griffiths’ comfort temperature. Offices with five or more people had lower mean comfort temperature (24.1 ℃) than private offices (25.0 ℃). The mean comfort temperature in offices larger than 80 m2 was 23.7 ℃ with warmer thermal preference, while offices smaller than 40 m2 were approximately one-degree Celsius higher. Offices with no shading device, window blinds opened, and tiled floorings had mean comfort temperatures higher than 25.0 ℃. The findings also indicated that offices with more than a 60% glazing ratio have a slightly higher mean comfort temperature at 24.9 ℃. The thermal sensation during closed blinds was much cooler than opened ones. The anthropometry of the human body impacts how heat is regulated; thus, respondents with higher Body Mass Index (BMI) and above-average body surface area (higher than 1.7 m2) had significantly lower comfort temperatures and preferred more humid surroundings. Mean comfort temperature was statistically significant with BMI with a noticeable difference between underweight (25.1 ℃), normal (24.5 ℃), and obese (23.9 ℃) BMIs. In this study, it is recommended that BMI be considered when positioning occupants in shared offices, and window blinds are an integral shading device for adjusting indoor thermal comfort levels.

A Novel H2O/LiBr Absorption Heat Pump with Condensation Heat Recovery for Combined Heating and Cooling Production: Energy Analysis for Different Applications

The aim of this study is to analyze the feasibility of the single-effect H2O/LiBr absorption heat pump cycle to produce combined heating and cooling. To achieve this, first, the main changes that the absorption cycle requires are described in comparison with the conventional single-effect absorption chiller. Then, the cycle’s operational limits in terms of temperature lift and LiBr crystallization are evaluated. In this sense, driving heat temperatures required for these applications range from 85 °C to 120 °C. The energy and exergy performance (in terms of cooling and heating capacities, cooling and heating coefficient of performance, and exergy coefficient of performance) of the cycle is theoretically studied for five different types of applications that require simultaneous heating and cooling: building air conditioning, a 4th generation district heating and cooling network, a sports center with an indoor swimming pool, a hybrid air conditioning system with an absorption heat pump and a desiccant evaporative cooling system, and simultaneous cooling and water purification application for coastal areas. The system performance in terms of the cooling coefficient of performance varies in the range of 0.812–0.842, in terms of heating coefficient of performance from 0.58 to 1.842, and in terms of exergy coefficient of performance from 0.451 to 0.667. The application with the highest exergy coefficient of performance is the 4th generation district heating and cooling network.

RETRACTED: Optimal design and transient simulation next to environmental consideration of net-zero energy buildings with green hydrogen production and energy storage system

The integration of renewable energies to produce required commodities and mitigate environmental effects in developed countries has been investigated and tested recently. This study aims to model and develop a building without getting energy from the grid with four occupants for Kuwait's capital and largest metropolis, one of the most significant cities in the Middle East, for reducing greenhouse gas emissions (GHG). Hydrogen energy is employed as energy storage for this building outside the zero-energy network due to the benefits and applications of hydrogen energy. TRNSYS software was utilized for this simulation, and the transient performance of the previously described ZEB was examined annually using TRNSYS software. The building is powered by solar panels, and any extra electricity generated is considered for the hydrogen production and storage unit for use when there is a lack of solar radiation and the building has to be powered. Hot water is created using an evacuated tube solar collector, and it is then kept in a hot water tank. For cooling and heating load, a geothermal heat pump system with auxiliary heaters is employed. MATLAB software is used to analyze the thermal comfort of occupants using the Fanger model. The findings indicate that 72 PV panels with a 1.46 square foot surface area will be used to supply the building without any power shortages. In addition, the building will have zero energy and will receive its hot water from forty 1.5 m2 solar collectors. The ultimate hydrogen pressure tank will be greater than that of the beginning level. The building's air conditioning system offers annual thermal comfort. Additionally, the provided DHW is always at the predetermined temperature of 55 °C. Finally, the usage of the building's roof space can turn into a ZEB and greatly lower Kuwait's greenhouse gas emissions. Environmentally, the proposed system reduce 33% CO2 emission rate compared with fossil fuel.

Semi-Supervised Random Forest Methodology for Fault Diagnosis in Air-Handling Units

Air-handling units have been widely used in indoor air conditioning and circulation in modern buildings. The data-driven FDD method has been widely used in the field of industrial roads, and has been widely welcomed because of its extensiveness and flexibility in practical applications. Under the condition of sufficient labeled data, previous studies have verified the utility and value of various supervised learning algorithms in FDD tasks. However, in practice, obtaining sufficient labeled data can be very challenging, expensive, and will consume a lot of time and manpower, making it difficult or even impractical to fully explore the potential of supervised learning algorithms. To solve this problem, this study proposes a semi-supervised FDD method based on random forest. This method adopts a self-training strategy for semi-supervised learning and has been verified in two practical applications: fault diagnosis and fault detection. Through a large number of data experiments, the influence of key learning parameters is statistically represented, including the availability of marked data, the number of iterations of maximum half-supervised learning, and the threshold of utilization of pseudo-label data. The results show that the proposed method can effectively utilize a large number of unlabeled data, improve the generalization performance of the model, and improve the diagnostic accuracy of different column categories by about 10%. The results are helpful for the development of advanced data-driven fault detection and diagnosis tools for intelligent building systems.

Energy tunnels as an opportunity for sustainable development of urban areas

The use of renewable energies will be increasingly necessary to reduce carbon dioxide emissions. An important contribution can be provided by energy tunnels, which make it possible to draw on a form of clean, renewable and locally accessible thermal energy for heating and air conditioning of buildings. The paper describes the characteristics of an energy tunnel and the design aspects necessary for its conception. Explicit reference will be made to the studies conducted at the Politecnico di Torino which led to the development of an innovative energy segment then used to create an experimental prototype in the true size of an energy tunnel. The data collected allowed to evaluate the performance of the system and to study the possibility of thermally activating the tunnels of the future Line 2 of the Turin Metro, allocating the heat partly to the air conditioning of the stations and partly to external users. With a view to sustainable urban development, the possibility of integration with district heating systems and the possible creation of local heat distribution networks at different temperatures, directly connected to the underground infrastructure, is particularly attractive and promising.

Experimental designs applied to a direct expansion heat pump with solar energy

The direct expansion heat pump with solar energy is an energy conversion system used for water heating applications, air heating for air conditioning buildings, water desalination, solar drying, among others. This paper reviews the main designs and analysis of experiments in order to identify the fundamental objectives of any experiment which may be: to determine the factors that have a significant influence, to obtain a mathematical model and/or to optimize performance. To achieve this task, the basic and advanced configuration of this system is described in detail in order to characterize its thermal performance by means of energy analysis and/or exergy-based analysis. This review identifies possible lines of research in the area of design and analysis of experiments to develop this water heating technology for industrial applications.

System design and long-term field test for a novel multi-mode heating tower heat pump system in cold regions

Aiming at the shortcomings of the cooling and heating sources of conventional building air conditioning systems, a multi-mode regeneration HTHP system is proposed and the working principle and working mode in detail are described. The system is applied in the actual energy-saving retrofit project, and control strategies and evaluation calculation method are given. The cooling performance, heating performance, and moisture absorption characteristics of HTHP systems are calculated hourly, daily, and throughout the year. The results show that: the average comprehensive cooling efficiency is 4.34 when the average air temperature in summer is 30 °C and the average relative humidity is 67.1%, and the average comprehensive heating efficiency is 3.12 at the temperature of -1.52 °C and humidity of 77.3%. The annual comprehensive cooling and heating operation efficiency are 4.47 and 3.49. The average regeneration efficiency during the test is 4.34 kg/kWh, which is less affected by the external environment and operating conditions. During the operation in winter, the moisture between the solution and the air migrates in two directions: evaporation dominates at higher temperatures and lower humidity, and absorption is on the contrary. Comprehensive moisture absorption accounts for about 3.9% of the whole year.

Development of a cost effective approach toward energy efficient buildings by design, fabrication and economical analysis of air conditioning pods: A case study of a bus station in Thailand

Energy consumption by air conditioners in buildings is 57% around the globe. However, particularly in Thailand percentage of energy consumption is 18.6% by bus stations due to the massive tourism. The current study aims to provide feasibility and economical analysis of small air conditioning (AC) pods at a bus station located in Hat Yai Thailand by design, fabrication and experimental investigation. As there is no need to cool complete waiting area. An economic analysis is performed in Homer Pro software. According to the results, thermal load calculated for Pod is 1236 W. COP of the system is 1.5. Moreover, proposed system is 9.5% more economical than pre working system with the payback period of 1.72years. Also, per unit cost of electricity after installation AC pods reduces by 31%. Moreover, The AC pod successfully lowered the cabin temperature down till 17 °C by using only 4.9 A and 1127 W. Current research can be used to provide thermal comfort to travelers at airports, subway or train stations or in office as a separate cabins using less amount of energy. Also, it will be a milestone towards development of simulation based small AC installations in commercial sectors, to save cost and energy in Thailand.