Efficient Air Conditioning Research Articles

BIM-based techno-economic assessment of energy retrofitting residential buildings in hot humid climate

Buildings in hot humid climates are energy intensive to operate. Energy consumption in Saudi Arabia is almost three times higher than the global average, and one of the major contributors to that is the residential sector. Increasing environmental and economic concerns, in the form of Saudi Vision 2030, mean that the existing unsustainable residential building stock has to be energy retrofitted. This study examines the techno-economic feasibility of retrofitting existing homes in Eastern Province, Saudi Arabia. A Building Information Modelling (BIM)-based retrofit framework has been adopted and investigated on two case studies. Eight Energy Efficiency Measures (EEMs) have been implemented including increasing cooling set point temperature, using energy efficient appliances, replacing conventional lights with more efficient lights, applying window shading, improving glazing type, improving air tightness, using more efficient air conditioning system, and adding envelope insulation. A three-level energy retrofit plan is proposed. Results indicate that annual energy consumption in a villa is reduced by 13.79%, 19.27% and 56.9%, and in the apartment building by 22.84%, 28.85% and 58.5% through a level 1, 2 and 3 retrofit respectively. Compound Payback Period (CPP) was computed to assess the economic viability. For the villa, investing in a level 1, 2 and 3 retrofit will pay back in 0.92, 8.37 and 25.15 years respectively, while for the apartment building, the payback period is 0.60, 11.28 and 24.60 years respectively. Thus, energy retrofitting of existing homes has the potential to significantly reduce energy consumption, however, it is economically not viable in the existing scenario. Electricity tariffs need to be further increased and coupled with incentive programs to render deep energy retrofits feasible. Furthermore, the investigated BIM-based approach can be adopted to investigate energy retrofitting in other climate zones of Saudi Arabia and other countries in the region, and eventually be adopted to efficiently effectuate the colossal task of retrofitting the whole existing residential building stocks of these countries.

A review on current status of capacity control techniques for two-phase ejectors

Abstract The adoption of highly efficient vapour-compression heating, ventilation, air conditioning and refrigeration (HVAC&R) systems is compulsory to achieve a low-carbon society. Expansion work recovery using a two-phase ejector is widely recognized as one of the most promising measures to improve the energy efficiency of HVAC&R units. This holds true for all operation conditions provided that an effective capacity control technique is implemented. In this work a thorough critical review on the current status of the presently available capacity control strategies for two-phase ejectors was carried out. In addition, their pros and cons as well as the comparison of their performance were reported. It was concluded that two-phase ejectors can be properly capacity controlled in large- and medium-scale vapour-compression units. However, a suitable capacity control mechanism for small-scale vapour-compression solutions still requires a major breakthrough and is being intensively discussed among experts in the field.

An Intelligent Feedback Controller Design for Energy Efficient Air Conditioning System

Air conditioning systems were invented to improve human comfort in a room or hall. An efficient air conditioner systems are always needed to minimize the power consumption. There are several settings with lot of control devices were introduced in the past years to achieve minimal energy consumption rate. Those control systems were minimized the energy consumption to certain limit without considering human comfort. The proposed model is designed to minimize the energy consumption with maximum human comfort. Several sensor modules were introduced in the model to predict human comfort level in a room or hall. The sensor data are taken as feedback to the air conditioning system for attaining maximum human comfort level. The proposed design is verified with energy consumption calculation and change in room temperature measurements.

Air Conditioning Research Evolution from 2008 to 2019: A Scientometric Analysis

Air conditioning is an essential topic in heat transfer phenomena because it is widely applied in homes and industries. It has an incredible amount of applications ranging from health care to food shelf life. With the enhancement of technology, it is necessary to create new devices that increase the efficiency of air conditioning. Hence, it is required to evaluate the trend of study of this topic to help researchers to get the best research direction that promotes the acquisition of better experimental results. For that reason, it was collected a total of 2431 documents about air conditioning from the Science Citation Index Expanded during the period from 2008 to 2019. Next, it was used HistCite to analyze the yearly output, country, institution, citation impact, and citation relationships in this field of study. Results suggest that the research of air conditioning had an increase during the studied 11-year period. The countries with the highest research output were China, The USA, and Japan, and the institutions with the highest research output were the National Natural Science Foundation of China and the Hong Kong Polytech University. The journals with the largest number of articles were Energy and Buildings with 195 publications and Applied Thermal engineering with 164 papers.

Evaluation of energy requirements of an industrial scale plant for the cultivation of white button mushroom (<em>Agaricus bisporus</em>)

The white button mushroom (Agaricus bisporus) industry is paying attention to innovation for a more sustainable production and it is getting sophisticated to reach high grade of energetic efficiency coupled with high quality product. For mushroom cultivation the environmental conditions must be controlled therefore in some phases the heat needs to be provided and in other ones it needs to be removed. The objective of this study was to investigate the current growing methodology used at an industrial mushroom farm site for a quantification of energy consumption. Mushroom growing parameters such as temperature and relative humidity were monitored during the production process placing sensors for a continuous data recording of these parameters in different and crucial positions throughout the entire production cycle. Heat is massively produced by the compost/mycelium system and the goal was to quantify the amount of energy needed to remove it through a cooling system and a forced air system that pulls cold air in the cultivation room and picks up the warmer and more humid air. Often, the heat produced by the cultivation room is not enough to reach the optimal growth conditions. In this case the application of an air heating system is necessary. The study was focused on evaluating the energy exchanges during a 41-day period corresponding to a growth cycle of three flushes to quantify the energy requirements of the conditioning system. A total energy of 5483 kWh/cycle was quantified for a mushroom production of 25,000 kg, corresponding to a specific energy requirement of 0.22 kWh/kg, 0.18 for cooling and 0.04 for heating. Results showed that the electric power consumption represents a crucial cost for the mushroom production, therefore an optimization of the energy requirements of the production plant is desirable and it can lead to relevant economic savings. A scenario considering a more efficient air conditioning system was proposed for a more sustainable mushroom production.

Comparison of Energy Consumption Between a Standard Air Conditioner and an Inverter Type Air Conditioner in an Office Space

Demand for air conditioners (ACs) has exponentially increased worldwide over the last few years. Countries with booming economies report high growth of sales of room air conditioners. Sri Lanka is not an exception. With the increased gross domestic product (GDP) and warming climates, demand for room air conditioners is expected to further increase. Meeting the increased demand for electricity will be a challenge. Increased use of energy efficient air conditioners has positive impacts on the national grid, especially during periods of high demand. In a regular AC, the compressor runs at a fixed speed and is either ON or OFF. In an inverter AC, the compressor is always on, but power drawn depends on the demand for cooling. The speed of the compressor is adjusted appropriately. In this study, the energy consumption of a regular and an inverter AC of the same capacity was evaluated in a typical office room, under similar operating conditions. Energy consumption was measured for six consecutive weeks and compared. Results show that the daily average energy consumption (for an 8-hour operating period) was 13.5 kWh for the standard AC and 8.7 kWh for the inverter type AC. Therefore, it is concluded that inverter technology can save about 35% of electricity consumed over a standard air conditioner. With the expected growth of air conditioner use and ambient temperature rise, inverter technology can significantly contribute to reduce the peak demand and energy use.

Transitioning to high efficiency air conditioning in Saudi Arabia: A benefit cost analysis for residential buildings

This paper assesses the benefits of transitioning to high efficiency air conditioning (AC) equipment for existing units specific to the residential building stock in the Kingdom of Saudi Arabia (KSA). The analysis is based on a calibrated residential building stock model for Saudi Arabia supported by national statistics regarding the characteristics of AC systems. Various housing prototypes, vintages, and locations are included in the analysis. Specifically, the analysis considers the scaling up of the government's High Efficiency AC (HEAC) program which offers 900 Saudi Riyals (240 USD) per unit to consumers for up to 6 split system units with an energy efficiency rating (EER) of 13.0 or more per household. The main findings of the study suggest that upgrading the existing old stock of window units and split systems currently in place to the requirements of HEAC program would generate a reduction in electricity consumption of around 33 TWh/year and 24 million tons of CO2. Due to the effect of the HEAC consumer subsidy, purchasing a high efficiency unit has a simple payback period for the consumer of 5 years which is faster than less efficient AC options. This would come at a cost to the government of approximately 6 Billion USD resulting in an annual income of 3.0 Billion USD from the sale of avoided fuel associated with the saved electricity consumption.

Feasibility of ground source heat pump using spiral coil energy piles with seepage for hotels in cold regions

Ground source heat pump (GSHP) using energy piles is a clean and efficient air conditioning technology. However, this system may suffer annual soil thermal imbalance when it is applied in buildings in cold regions, causing cold or heat accumulation in soil and having effect on the system’s long-term operation. To simulate the system performance and investigate system feasibility in Chinese cold regions, a system simulation model is established considering important influential factors of energy piles group. The system is applied in a hotel of four typical cities (Harbin, Changchun, Shenyang and Beijing). The dynamic building load is simulated which shows that the hotels in four cities are heating-dominated with load ratios of 6.78 in Harbin, 6.51 in Changchun, 2.94 in Shenyang and 1.20 in Beijing. Results show that GSHP system using spiral coil energy piles is efficient and only consumes 51–62% power of conventional Boiler + AC system. When GSHP is applied in hotels in cities with similar climates to Harbin and Changchun, the soil thermal imbalance with serious cold accumulation will cause the heating performance decline as well as the heating deficiency. When GSHP is applied in hotels in cities with similar climates to Shenyang, the soil thermal imbalance with cold accumulation will cause the heating performance decline but the system’s heating capacity is acceptable. When GSHP is applied in hotels in cities with similar climates to Beijing, the soil thermal imbalance with slight heat accumulation will increase the heating performance. This work contributes to the performance prediction and application guidance of GSHP systems using spiral coil energy piles in cold regions.

The Weather Impact on Heating and Air Conditioning With Smart Thermostats

These days, the majority of devices are connected to the Internet of Things. One of the areas that need further research is the smart thermostats’ operation. In this article, we perform an analysis of efficient household heating and air conditioning with smart thermostats. To the best of our knowledge, this is the first article that correlates real data from the smart thermostats and weather to predict heating, ventilation, and air conditioning (HVAC) operation. The main problem that we focus on is the study of overheated and overcooled homes. Our results show that adaptive strategies that learn the weather impact on the house enabled three times reduction of heating time and four times reduction of air conditioning, with the most significant improvement during sunny days.

Regulating Automobile Air Conditioning Efficiency Can Save Megatons of CO <sub>2</sub> Emissions for Free

Improving fuel efficiency for on-road vehicles is crucial to reducing the environmental impacts of the transport sector. However, fuel efficiency is regulated based on laboratory tests that usually do not consider the performance of on-board air conditioning systems. Therefore, car manufacturers are not fully incentivized to improve the efficiency of air conditioning. By analyzing one million real-world fuel efficiency records from Chinese light-duty passenger vehicle drivers, we show that gasoline consumption increases by 1.3% annually due to air conditioning use at higher temperatures. This response differs across car models with models produced by Chinese manufacturers showing the lowest efficiency. We estimate that regulating air conditioning efficiency could save 1.6 million tons of CO2 emissions annually for light-duty passenger vehicles in China, and this potential is essentially free to achieve. We suggest that expanding the regulation to more vehicle categories in more countries will further increase the saving potential substantially.

Energy Efficient Air Conditioning System of the Temple Complex

The purpose of this work is to develop a year-round energy-efficient air conditioning system for the temple complex, that meets modern engineering requirements and standards. And it should not violate the traditional appearance of an Orthodox church.In this article there are considered the requirements and standards for the construction of the temple complex together with the architectural solution and the geographical location of the construction entity. The proposed air conditioning system (ACS) with a pneumohydraulic diagram and design modes is described. This system is valid for the summer and winter seasons. The main element of the ACS of the temple complex is an array of heat pipes. The efficiency of the installation is achieved, first of all, due to the recovery of soil heat in the annual cycle. In addition, efficiency is increased by utilizing the heat of the waste air stream and indoor recirculation systems. The article represents a constructive solution for the proposed heat pipe and its design modes of operation in the summer and winter periods together with the expected technical characteristics in different modes of operation, as well as design options for the upper heat exchanger. There is given the concept of the arrangement of the elements of the pneumohydraulic diagram on the cartographic plan of the building and their mutual correlation with the intensity of the operating mode for the soil. And the last, but not least, the article represents a simulation of the annual soil regime, calculated by the finite element method, performed in the ANSYS computational environment.

Data-driven prediction of vehicle cabin thermal comfort: using machine learning and high-fidelity simulation results

Predicting thermal comfort in an automotive vehicle cabin's highly asymmetric and dynamic thermal environment is critical for developing energy efficient heating, ventilation and air conditioning (HVAC) systems. In this study we have coupled high-fidelity Computational Fluid Dynamics (CFD) simulations and machine learning algorithms to predict vehicle occupant thermal comfort for any combination of glazing properties for any window surface, environmental conditions and HVAC settings (flow-rate and discharge air temperature). A vehicle cabin CFD model, validated against climatic wind tunnel measurements, was used to systematically generate training data that spanned the entire range of boundary conditions, which impact occupant thermal comfort. Three machine learning algorithms: linear regression with stochastic gradient descent, random forests and artificial neural networks (ANN) were applied to the simulation data to predict the Equivalent Homogeneous Temperature (EHT) for each passenger and the volume averaged cabin air temperature. The trained machine learning models were tested on unseen data also generated by the CFD model. Our best machine learning model was able to achieve a test error of less than 5% in predicting EHT and cabin air temperature. Predicted EHT can also yield thermal comfort metrics such as Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD), which can account for different passenger profiles (metabolic rates and clothing levels). Machine learning models developed in this work enable predictions of thermal comfort for any combination of boundary conditions in real-time without having to rely on computationally expensive CFD simulations.

Energy and thermal storage in clusters of grid-independent buildings

The extensive substitution of fossil fuels with renewables creates the U-shaped demand curve (duck curve) problem which is exacerbated in the summer months with the extensive use of air-conditioning. This study examines the hourly, daily, and yearly operation of a cluster of one hundred grid-independent buildings that completely rely on photovoltaics for electricity generation, including their air-conditioning needs. The cluster stores energy in hydrogen as the seasonal storage medium and chilled water for cooling as the daily storage medium. Thermal storage of chilled water and the use of efficient air-conditioning (refrigeration) equipment significantly reduces the needs for the generated electric energy and stored energy: The utilization of thermal storage in addition to chemical storage has three beneficial results: a) it reduces by about 40% the needed solar power installation; b) it reduces by a factor of three the losses associated with energy storage; and c) it reduces by factor of four the necessary hydrogen storage capacity. The improved performance of the system is expected to significantly reduce the overall cost associated with grid independent buildings.

Rules of Cooperation Between the State Fire Service and Selected Institutions Under the Conditions of CBRN Threats, Including Biological Ones — Analysis of Polish Solutions

The article presents conclusions from the analysis of solutions applied in Poland in the field of implementation of joint projects of the State Fire Service and selected institutions responsible for ensuring the internal security of the state in the field of counteracting CBRN threats, including biological ones. The analysis refers to the binding legal system and the organizational solutions resulting from it. The considered legal order included the provisions of universally binding law and local law. It was assumed that the use of weapons of mass destruction in a terrorist attack might be executed through the contamination of air, water or soil, as well as by disease carriers: infected insects, rodents or people. One of the real methods of performing bioterrorists attacks is to contaminate the air by spraying, for example, biological aerosol. That is since aerosol production equipment is easily accessible, and most biological agents can be easily transported by air. The objects of such an attack will be primarily places with efficient air conditioning systems, public buildings and metro stations, and all places where people gather including railway stations, airports, shopping centers, sports and cultural facilities, government and public buildings, areas of military concentration, and places of public mass events. The considerations presented in this article refer to issues on a macro and micro scale, which allowed for distinguishing the rules of cooperation and its effectiveness. While endeavoring to objectify the conclusions from the analysis, the article was elaborated by a team of Polish, Czech, and Ukrainian experts.

Performance comparison between metal-organic framework (MOFs) and conventional desiccants (silica gel, zeolite) for a novel high temperature cooling system

The use of desiccant-coated heat exchangers (DCHE) in air conditioning systems possesses great advantages in the independent control of both temperature and humidity, as well as low energy consumption and high coefficient of performance (COP). The paper presents a novel high temperature cooling system that uses metal-organic frameworks (MOFs) as sorbents for humidity control. MOFs are a new class of porous crystalline materials consisted of metal clusters and organic linkers, which have an excellent performance of water sorption due to the large specific surface areas and high porosity. In this research, we directly coat MOFs on the heat exchange surface of evaporator and condenser. The evaporator can simultaneously remove both the sensible and latent loads of the incoming air without reducing the temperature below its dew point. The regeneration of wet MOFs is completely driven by the residual heat from the condenser. We also make comparison between the MOF-coated cooling system and conventional desiccants coated ones (i.e. silica gel, zeolite) by way of tests and calculation. The results indicate that the dehumidification capacity of the MOF-coated heat exchanger outperforms other conventional desiccant coated ones under low regeneration temperature (∼50°C). The MOF-coated system has a high COP, up to 7.9, and can save 36.1% of the energy required, compared to the traditional vapour compression system with reheating. The amphiphilic MOFs used in the study have high water uptake and low regeneration temperature, and they thus have the potential for being scaled up for large-scale applications in energy efficient air conditioning systems.

ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ КОНДИЦІЮВАННЯ ЗОВНІШНЬОГО ПОВІТРЯ СИСТЕМИ КОМБІНОВАНОГО ТИПУ

One of the most attractive reserves of enhancing the energetic efficiency of air conditioning systems is to provide the operation of refrigeration compressors in nominal or close to nominal modes by choosing rational design cooling loads (cooling capacities) and their distribution according to a cooling load behaviour within the overall design (installed) cooling load band to match current changeable climatic conditions and provide close to maximum annual cooling capacity generation according to cooling duties. The direction of increasing the efficiency of outdoor air conditioning in combined central-local type systems by rationally distributing the heat load - cooling capacity of the central air conditioner into zones of variable heat load in accordance with current climatic conditions and its relatively stable value, i.e. cooling capacity required for further air cooling at the entrance to the indoor recirculation air conditioning system is justified. By comparing the values of the excessive production of cold and its deficit within every 3 days for a rational design heat load of the air conditioning system (cooling capacity of the installed refrigeration machine), which provides close to maximum annual production of cold, and the corresponding values of the excess and deficit of cooling capacity in accordance with current climatic conditions during July substantiated the feasibility of accumulating the excess of cooling capacity of a central air conditioner at low current loads and its use for covering cooling deficit at elevated heat loads through pre-cooling the outdoor air. It is developed a scheme of a combined central-local air conditioning system, which includes the subsystems for the outdoor air conditioning in a central air conditioner and the local indoor recirculated air conditioning.

Modeling and Simulation of a Building towards Energy Efficiency

Residential buildings are the significant energy consumer of the India which is about 24% of the total energy consumption. Energy efficient buildings are the ideal solution to reduce energy consumption in the building sector. The energy efficient buildings can be achieved by incorporating passive features or renewable energy systems or both. The current work aims to perform a retrofitting analysis of an existing building into an energy efficient building. For performing the energy analysis REVIT 2017 tool is used. Using the REVIT 2017 tool building model is developed, building information are loaded and energy analyses are performed. The building is analyzed as two cases. The first case is to estimate energy performance of the existing building. The second case is to incorporate passive features and renewable energy system to the building and evaluate the energy performance. Existing building Energy Usage Intensity (EUI) was 193 kWh/m2/year. When passive features (Insulation, additional window glazing and efficient air conditioning systems) alone incorporated to the building the building EUI is reduced to 138 kWh/m2/year. Along with Passive features Photovoltaic modules with different efficiencies 16%, 18% and 20% are considered for renewable energy generation. The energy generation for the different PV modules for three different roof area (40%, 60% and 70% of total roof area) is evaluated. The energy usage intensity varies from 11.4 from -150 kWh/m2/year for the combination of different efficiency of PV module and the different % of roof area covered. The negative sign indicates the energy generation after the required energy usage. The payback period for only incorporating passive features is 6.3 years and while incorporating PV system with passive features is 9 years.

Transforming our buildings for a low-carbon era: Five key strategies

Significantly reducing building sector greenhouse gas emissions is necessary to meet state and local climate stabilization goals. Initiatives to decarbonize home and building energy use are enabled by a new generation of advanced air source heat pumps (ASHPs) that provide efficient, comfortable heat even at low outdoor temperatures as well as highly efficient air conditioning in the summer. Coupled with thermal improvements to building envelopes and smart controls responsive to grid reliability needs, ASHPs are displacing the use of fossil fuels for comfort heating while providing a range of economic benefits. Investments to decarbonize buildings are most economical in natural market cycles of building construction, renovation and equipment replacement, and as part of community development initiatives to improve and preserve affordable housing. A growing number of state and local policies and programs are accelerating the rate of efficient electrification of home and building heating to replace fossil fuel heat with increasingly carbon-free renewable electricity.

Cascaded liquid desiccant system for humidity control in space conditioned by cooled membrane ceiling and displacement ventilation

Displacement ventilation (DV) combined with liquid desiccant membrane cooled ceiling (LDMC-C) is an efficient Heating, ventilation and Air conditioning (HVAC) system. However, the LDMC-C/DV has limited performance in office spaces located in hot and humid climates or characterized by high internal latent loads due to the inability to control the humidity. This study proposes a cascaded liquid desiccant system in which the liquid desiccant flow exiting the LDMC-C is directed into a liquid desiccant heat and mass exchanger in the DV supply duct to control the humidity in the space and conserve energy. To achieve this goal, an integrated model for different components of the cascaded liquid desiccant system is developed to predict the comfort level and the air quality inside the space as well as the energy consumption of the system. The model was validated experimentally in a climatic chamber. The validated integrated system model was applied to a case study to assess the effectiveness of the system in hot and humid climate. Two configurations of the LDMC-C and mass exchanger were simulated and found to provide acceptable humidity for comfort in the occupied zone of the space. Moreover, the cascaded system cooling and heating energy were found lower by 21.25% and 16.23% respectively in August when compared to a LDMC-C/DV, and to DV membrane exchanger system with different configuration. The cooling and heating energies were also lower in the cascaded system compared to a LDMC-C/DV while using conventional supply air dehumidification method.

Energy efficiency and cost saving opportunities in public and commercial buildings in developing countries – The case of air-conditioners in Ghana

Available data and market surveys conducted in Ghana have shown that 60–80% of electricity consumed in offices of public and commercial buildings is used to run air-conditioners to provide indoor thermal comfort for productive office work. Electricity consumptions of these air-conditioners are relatively high and are in the range of 3000–5400 kWh/yr per air-conditioner depending on the brand and the cooling capacity. Low energy efficiency rating of the air-conditioners is a major contributing factor to their high electricity consumption.This present work has conducted studies on the energy efficiency of air-conditioners used in the offices of public and commercial buildings in Ghana. Technical data from a national survey conducted on air-conditioning equipment used in the country was used for this study. In addition, a power quality clamp meter was used to monitor the actual power consumptions of stratified samples of the conventional air-conditioners in the offices, as well as that of an inverter air-conditioner installed in an office.The results from this study show that over 85% of air-conditioners used in Ghana exist in the lowest energy efficiency ratio category (1-star) and the remaining percentages are in the next lower categories (2 and 3-stars). It has been determined that enforcing energy efficiency regulations to shift the air-conditioner market in Ghana into the higher energy efficiency ratio (EER) categories has huge benefits for the country. For instance, there are annual electricity savings potential of 260 GWh and 1770 GWh respectively for the year 2020 and 2030 using inverter air-conditioners which have higher energy efficiency rating (4-star equivalent) compared to the current lower EER air-conditioners in the country. It is also determined that if Ghana continues to follow business as usual with low EER air-conditioners, it will need to install electricity generation capacity of about 480 MW by 2030 to handle influx of low energy efficient air-conditioners alone.Financial analysis has also revealed that there is opportunity for electricity consumption cost savings of about US$ 1.96 billion from the year 2018–2030 with higher EER air-conditioners (4-star) being installed in the country compared to the current low EER air-conditioners.