Air-conditioning Energy Savings Research Articles

Perovskite-Coated Thermochromic Transparent Wood: A Novel Material for Smart Windows in Energy-Efficient and Sustainable Buildings.

Transparent wood (TW) has emerged as a sustainable alternative to conventional glass as an energy-efficient window glazing material owing to its exceptional optical transparency and superior mechanical and thermal performances. However, it is challenging to develop the TW-based color-switching smart windows with both high optical performance and mechanical strengths. In this work, an optically switchable and mechanically robust perovskite-coated thermochromic transparent wood (PTTW) is developed for use as smart windows to achieve an effective solar modulation and thermal management. PTTW exhibits a substantial solar modulation ability Δτsol of 21.6% and a high clear-state luminous transmittance τlum of 78.0%, which enable an efficient thermal regulation while ensuring high visual clarity. PTTW also offers enhanced mechanical properties (i.e., tensile strength σtens = 71.4 MPa and flexural strength σflex = 93.1 MPa) and improved thermal properties [i.e., thermal conductivity K = 0.247 W/(m·K) and heat capacity C = 1.69 J/(g·°C)] compared to glass-based smart windows, as well as excellent performance stability (i.e., 200 heating-cooling cycles), manifesting its applicability in real building scenarios. In addition, PTTW also demonstrates a remarkable thermal-regulating performance (i.e., 5.44 °C indoor air temperature regulation) and an energy-saving potential (i.e., 12.9% heating, ventilation, and air conditioning energy savings) in Hong Kong. Overall, this study contributes to the progression toward energy-efficient and sustainable buildings.

IoT-Based Air Conditioning Control System for Energy Saving

A high portion of electric consumption is air conditioning in householders or offices, reaching 42%. Therefore, it is necessary to automatically regulate air conditioning operations for energy saving using a control system, usually involving its hardware. As another option, the control system also involves electronic devices and software. This research developed an automatic control system using an ESP32 microcontroller integrated into the Blynk-based internet of things (IoT) for energy-saving air conditioning. The ESP32 was programmed using Arduino IDE and combined with a motion sensor to maximize energy saving. The motion sensor was a trigger to turn on the system. The recorded data were current, voltage, power, temperature, and motion detection. Based on the recorded power, the consumed energy was computed using trapezoidal and Simpson's composite rules of numerical integrations and ordinary methods. The testing was conducted in conventional, manual, and automatic operations. The yielded automatic control system operated adequately. The testing results revealed that the automatic operation saved 1.15 kWh (15.00%),0.99 kWh (13.66%), and 1.14 kWh (14.87%) average daily energy compared to the conventional operation, respectively, by using the ordinary, Simpson's composite rule, and trapezoidal composite rule computations. While the automatic compared to the manualmethodssaved1.68 kWh (20.44%), 1.78 kWh (22.14%), and 1.66 kWh (20.24%), respectively, for the same computations. Thus, the automatic system considerably saved energy compared to conventional and manual operations. Moreover, these energy savings were also higher than some previous research on air conditioning energy savings.

Effect of source location on contaminant dispersion pattern and occupants inhaled air quality in lecture room under displacement ventilation

AbstractDisplacement ventilation (DV) is considered an energy saving air conditioning system and is especially recommended for classrooms for providing cool clean air in the occupied zone. However, in the current pandemic situation, ventilation systems should be assessed in terms of infection‐spread prevention as well. Hence, this study aims at assessing the efficiency of displacement ventilation in minimizing infection spread in lecture halls through investigating the effect of source position on the contaminant concentration distribution. The settings of a mid‐size DV lecture hall in Osaka University, Japan was chosen as a case‐study. Ten single‐contaminant‐source cases were simulated using CFD software. The cases were analyzed in terms of temperature distribution, contaminant diffusion pattern and vertical distribution, and breathing air quality using indices, such as local air quality index and scale of ventilation efficiency. The results demonstrated a considerable variation between cases in terms of contaminant distribution pattern, number of occupants affected, average inhaled‐air quality, and diffusion radius. Accordingly, given the ventilation system design, best and worst case‐scenarios were pointed out and factors affecting the variation were highlighted and further investigated to conclude the impact of each factor.

A novel solar-based human-centered framework to evaluate comfort-energy performance of thermochromic smart windows with advanced optical regulation

Thermochromic windows provide a promising and practical solution to lower building air conditioning energy via automatically reducing window-through solar radiation which imposes large cooling loads on air conditioning systems. The conventional framework for evaluating thermochromic windows assumes that the solar radiation passing through smart windows is immediately absorbed by indoor air, which ignores the deviated occupant comfort by indoor solar radiation and leads to a biased comfort-energy performance of thermochromic windows. This study proposes a novel solar-based human-centered framework to evaluate the comfort-energy performance of hydrogel thermochromic smart windows (HTSWs) via integrating human-solar modelling, solar-based indoor set-point correction, and building simulations. The comfort-energy performance of HTSWs are evaluated with different warm climates and compared to that of normal windows. The main results indicate that, the conventional framework, which ignores solar radiation on indoor human bodies, underestimates the discomfort time duration of indoor occupants by 55.0% and 75.2% when evaluating normal windows and HTSWs, respectively. Under the human-centered framework, with solar-based set-point correction, indoor occupants with HTSWs regulating solar radiation will be comfortable during more than 95% of working hours; and HTSWs reduce nearly 50% of the discomfort hours compared to normal windows. In addition, the average energy saving potential of HTSWs under the human-centered framework is extended by 35.0% compared to that under the conventional framework. To be specific, the air conditioning energy savings of HTSWs under the conventional framework are 9.9%–20.3% (average 14.5%); under the human-centered framework, the energy savings are 13.5%–25.6% (average 19.5%, which is 35% higher than that under the conventional framework). The considerably improved comfort-energy performance of HTSWs under the human-centered framework will further contribute to the wide adoption of HTSWs.

Experimental studies on natural bank type heating/cooling energy saving Air conditioning system

The present study reports air-based novel energy saving compact bank type earth air heat exchanger system (EAHE) (having only 25m2 area) fabricated from Polyvinylchloride pipes of nominal diameter 0.203 mm (8 inches) for inlet and outlet headers and main pipes and 0.150 mm (6 inches nominal diameter) for branched pipes, which is installed in Shaheed Bhagat Singh State University, Ferozepur in Punjab state, India (North West border area of India) and studied for the duration from April to August 2021 using the full factorial design with four inlet variables at multilevel to find a model equation between inlet and outlet variables, i.e., heat exchanger effectiveness and achieved temperature difference. An induced airflow mode has been used to provide near-uniform flow through all corresponding pipes of symmetrical-shaped earth air heat exchangers. The values of Dry bulb temperature (DBT) and wet bulb temperature (WBT) have been measured for air inlet, for air outlet, as well as for ambient air using resistance temperature detectors (RTD) installed at the requisite locations. Earth's undisturbed temperature (EUT) was also noted by installing RTD at a depth of 2 m, and the average measured value of EUT is found to be 28.5°C. The current system has imparted the temperature difference variation from 0.4 oC to 9.4 oC, and the effectiveness varied from 0.16 to 0.82 during the whole season. This system could give a cooling potential of 0.0523 kJ/s to 1.587 kJ/s using a mass flow rate of 0.163 kg/s.Experiments have been designed methodically to apply the full factorial technique. Most favorable parameters have been found for hot and dry and hot and humid weather. The current study is novel in terms of significantly improving the effectiveness of EAHE and addressing the central issue of space limitation in urban areas.

MARTINI: Smart meter driven estimation of HVAC schedules and energy savings based on Wi-Fi sensing and clustering

HVAC systems account for a significant portion of building energy use. Nighttime setback scheduling is an Energy Conservation Measure (ECM) where cooling and heating setpoints are increased and decreased respectively during unoccupied periods with the goal of obtaining energy savings. However, knowledge of a building’s real occupancy is required to maximize the success of this measure. In addition, there is the need for a scalable way to estimate energy savings potential from ECMs that is not limited by building specific parameters and experimental or simulation modeling investments. Here, we propose MARTINI, a sMARt meTer drIveN estImation of occupant-derived Heating, Ventilation and Air Conditioning (HVAC) schedules and energy savings that leverages the ubiquity of energy smart meters and Wi-Fi infrastructure in commercial buildings. We estimate the schedules by clustering Wi-Fi derived occupancy profiles and, estimate energy savings by shifting ramp-up and setback times observed in typical operational/static load profiles that are obtained by clustering smart meter energy profiles. Our case-study results with five buildings over seven months show an average of 8.1%–10.8% (summer) and 0.2%–5.9% (fall) chilled water energy savings when HVAC system operation is aligned with occupancy. We validate our method with results from Building Energy Performance Simulation (BEPS) and find that estimated average savings of MARTINI are within 0.9%–2.4% of the BEPS predictions. In the absence of occupancy information, we can still estimate potential savings from increasing ramp-up time and decreasing setback start time. In 51 academic buildings, we find savings potentials between 1%–5%.

How much HVAC energy could be saved from the occupant-centric smart home thermostat: A nationwide simulation study

Thermostat management plays a significant role in household energy conservation. This study aims to conduct a systematic and comprehensive analysis to quantify the energy savings potential of the occupant-centric smart thermostat based on a large-scale nationwide simulation infrastructure. The single-family Residential Prototype Building Model was used to represent a typical single-family detached house in the U.S. A generalized random occupancy presence schedule was created based on an occupancy probability schedule and k-means clustering algorithm. A total of 16,000 simulations, which were composed of four building foundation types, four heating source types, 40 American cities, five building energy code versions, and five thermostat control strategies, were conducted to evaluate the performances of the smart home thermostat in terms of saving building energy usage and maintaining occupant thermal comfort. The nationwide simulation results suggested that the temperature setback control during the unoccupied period could achieve some energy savings in the U.S. households. However, only very few of the 40 cities could see an annual Heating, Ventilation, and Air-conditioning energy savings ratio of over 30%. Besides, the implementation of the occupied standby temperature reset could greatly increase the peak load of the HVAC system and contribute to the grid load imbalance issue. It’s also worth noting that the smart recovery feature is proved to be able to bring additional benefits for a smart home thermostat. It could decrease the temperature setpoint not met time by about 30 min, and relieve the thermal discomfort due to the temperature setback control.

Effect of different building envelope materials on thermal comfort and air-conditioning energy savings: A case study in Basra city, Iraq

Recently, a numerous number of houses has been built using AAC materials, which consume the most amount of energy in the building sector by Heating, ventilation, and air -conditioning (HVAC) systems. Thus, the most significant factor affecting the energy consumed by HVAC systems is the materials used in the building. Building models are important tools in determining the energy efficiency of buildings. Numerous strategies have been established to construct building models, such as the weight, gray, and black boxes, as well as hybrid models. Hybrid models have not been researched extensively, although they provide a reasonable representation of actual indoor conditions. Therefore, this study employs a hybrid calculation model for the analysis of physical and empirical correlations to evaluate thermal comfort in buildings, which reflects their energy consumption. The residential load factor (RLF) technique is adopted owing to its systematic organization and ease of use, which is achieved by dividing the model into submodels. The model is verified and validated by drawing a comparison with field measurements and the output obtained from ANSYS software. The actual field measurements and ANSYS outputs match the outputs of the proposed model; the results show small residual errors, indicating a well-defined model structure. The cost and energy savings of vernacular buildings and autoclaved aerated concrete (AAC) (or low-cost) buildings have been highly debated in Basra city. Models of these two different building materials are simulated within the MATLAB/Simulink environment. Their results indicate that the vernacular building has the highest energy saving potential up to 47.83% over 24 h a day. These results provide an excellent argument to realize the benefits of vernacular buildings by reducing the dependency on powered cooling.

Using solar availability factors to adjust cool-wall energy savings for shading and reflection by neighboring buildings

The extent to which a solar-reflective “cool” wall can reduce a building’s cooling load in summer or increase its heating load in winter scales with the wall’s incident solar radiation, or solar availability. We assess how the solar availability at the wall of a central (modeled) building is affected by a neighboring wall across an urban canyon by calculating the central wall’s solar availability factor (SAF), defined as the ratio of sunlight incident on the central wall in the presence of the neighboring wall to that incident in the absence of the neighboring wall. Cool-wall heating, ventilation, and air conditioning (HVAC) energy savings simulated for an isolated central building (no neighbors) can be multiplied by SAFs to account for interactions with neighboring walls.Monthly values of SAF were evaluated in 17 climates across the United States, including three in California, for north, east, south, and west central walls, over a wide range of canyon aspect ratio (height/width). Results for four representative aspect ratios—0.2, 1, 2, and 10—are presented. In Fresno, CA, monthly SAF ranges from 0.90 to 0.96 for central walls facing north, east, south, or west when the aspect ratio is 0.2 (two-story single-family homes across a street) and both the central and neighboring walls are conventional (albedo 0.25). Monthly SAFs decrease as aspect ratio rises, falling to 0.06–0.24 at an aspect ratio of 10 (adjacent 10-story buildings on the same side of the street).An example worked for a two-story single-family home in Fresno on the west side of a residential street yields SAFs of 0.47 (north), 0.92 (east), 0.50 (south), and 0.63 (west) to apply to the cool-wall annual HVAC energy savings computed for an isolated central building. Shading and reflection reduce the home’s annual HVAC energy cost savings by 31%.

Social Influence and Energy Conservation: Using Obedience to Authority to Promote Air Conditioning Energy Saving

Social Influence and Energy Conservation: Using Obedience to Authority to Promote Air Conditioning Energy Saving

在室者の調整行動を利用したアクティブ省エネ空調制御システムの研究 その3.冬期における室内温熱環境の実測とアンケート調査

在室者の調整行動を利用したアクティブ省エネ空調制御システムの研究 その3.冬期における室内温熱環境の実測とアンケート調査

Effect of retro-reflecting transparent window on anthropogenic urban heat balance

Solar heat shielding against solar radiation over the entire building envelope is one of the most effective measures for achieving air-conditioning energy savings and preventing heat-island phenomenon in warmer climate regions. For this purpose, we proposed a new heat-shielding film, which possesses a retro-reflective property and a wavelength-selection property, while having the same degree of transparency as that of transparent glass. The proposed film can be easily applied to a wide variety of buildings and architecture, including new and existing buildings. This film embodies an innovative heat-shielding technique that makes it possible to effectively return solar radiation toward the sky, while minimizing the secondary effects to other buildings, to the ground, and so on. In order to verify these effects, several aspects of quantitative evaluation are demonstrated.The measurement results and concepts in this paper are referred to from the previous conference paper Inoue et al. [10].

An Accurate Data Collected Model in Air Conditioning Energy Saving Control

An Accurate Data Collected Model in Air Conditioning Energy Saving Control

The moisture content distribution of a room with radiant ceiling cooling and wall-attached jet system

Radiant ceiling cooling is a comfortable and energy saving air conditioning system, but condensation on the panels limits its application. The moisture distribution of a radiant cooling room is one of the key factors affecting the condensation of radiant panels. This paper uses a simulation model validated by experimental data to investigate the influence of wall-attached jets on the moisture content distribution of a room with radiant cooling. The influence of diffuser types and air velocities on the moisture content distribution is analyzed in the pre-dehumidification stage. This paper also studies the moisture content distribution and dew point temperature variation of the attached air layer with the cooling system operating with and without pre-dehumidification. The results show that a linear diffuser has a better attach effect, and the moisture content distribution is more uniform. The time it takes to reduce the moisture content to the design value of different diffusers is similar, approximately 25 min. With increasing air velocity and decreasing linear diffuser length, the non-uniformity coefficient (NUC) of the moisture content distribution increases and the pre-dehumidification time becomes longer. When the radiant cooling system operates without pre-dehumidification, the attached layer moisture content is high at the beginning, which may cause condensation in the first 7 min. Pre-dehumidification can decrease the moisture content and dew point temperature and effectively prevent condensation.

Performance Evaluation of a Medium-temperature Solar Cooling Plant

Solar cooling plants represent today an interesting solution for air conditioning and primary energy savings. However, the plant configurations are still on development and the different solutions are tested in pilot plants. In this paper, a study on a possible high-efficiency configuration has been conducted. This solar cooling plant is based on a linear parabolic collectors solar field operating at 160- 180°C and coupled with a double effect absorption chiller. This solution could lead to an energy performance near to the DEC technology but with lower investment costs. A numerical model in TRNSYS has been developed in order to evaluate the performance and the possibility to build a pilot plant in the RSE experimental area. Thanks to the model, the system design process was studied and were identified the most important parameters (area of the solar field, nominal power of the absorption chillers, and volumes of the heat storage). The way how these parameters affect the overall performance of the plant has been investigated and a sizing procedure for solar cooling plant with a nominal refrigeration power of 20 – 45kW was developed. A building in the RSE area was chosen and the procedure has been applied in order to design a dedicated solar cooling plant.

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.

Operation Analysis of the Rail Transit Stations Energy-Saving Air-Conditioning System Based on Petri Nets

In order to fully research and describe the dynamics of the energy consumption of rail transportation equipment operation, this chapter will Petri nets Establishment and analysis of the environmental control system air-conditioning power consumption model, so as to deepen the understanding of the principle of the energy consumption of devices running depth grasp of energy consumption the operational features of the equipment, take appropriate and effective energy-saving measures.

The air-conditioning energy savings achieved by application of time-predicted driven night ventilation

This paper analyses the influence of time-predicted night ventilation applied during the summer season on the total energy consumption of airconditioning system. Analysis has been made on the basis of a computer program for dynamic simulation of air-conditioned rooms thermal behavior. The program was developed at the Department for Thermal Engineering at the Faculty of Mechanical Engineering, University of Belgrade. Air-conditioning operating modes without and with application of night ventilation, and different periods of night ventilation are analyzed. Cooling loads, fan energy consumption and overall energy consumption for summer conditions for Belgrade for the whole cooling season are given. The obtained results were compared, and hereupon a review is given of the energy savings for the whole cooling season.

Individual Thermal Environments of Building with a Novel Air-Conditioning Energy-Saving Equipment

Individual air-conditioning system (IACS) can create an individual thermal environment control in a workroom which can contribute to save air-conditioning energy. In this study, we analyze the airflow circulation cell of the IACS with varied outlet port opening dimensions using the computational fluid dynamics (CFD) technique. We created an IACS, two workstations, lightings, and a cabinet in a 3-dimensional room. The fluid was assumed to be Newtonian, unsteady, and incompressible. We examined the effects of the outlet port opening on airflow circulation establishing process. Results will indicate the suitable outlet port opening for maintaining individual satisfied occupants’ requirements and improving energy saving potential.

Air Conditioning Energy Saving by Rooftop Greenery System in Subtropical Climate in Australia

Air Conditioning Energy Saving by Rooftop Greenery System in Subtropical Climate in Australia