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New working fluids with favorable features of moderate environmental effects are presently being developed to avoid high global warming potential. These hydrocarbon refrigerants have excellent energy efficiency and a low global warming potential, which means they have a low overall environmental impact. Some of these choices are non-flammable, and the flammable ones have substantially lower flammability than the much more flammable hydrocarbons. This paper examines the performance of hydrocarbon refrigerants in commercial refrigeration applications as alternatives for R-22. The findings of MATLAB software analysis of R-22 and R-290, as well as comparisons of the results in various parameters, systems, and components, are presented, demonstrating the benefits of using these hydrocarbon refrigerants. R-290 shows better performance at various evaporator and condenser temperatures. R-290 has a 4% higher performance than R-22. [ABSTRACT FROM AUTHOR]

In this paper, a 1 kW-class Solar-Ocean Thermal Energy Conversion integrated Air-Conditioning (S-OTEC/AC) experimental system, which can provide both electrical energy and cooling energy without any pollution, is constructed for the first time. Based on the experimental data, the system's overall performance was comprehensively evaluated in terms of energy, exergy, economy, and environment (4 E). Furthermore, the performance difference between the system using solar energy (i.e., S-OTEC/AC) and the system without solar energy (i.e., OTEC/AC) was compared. The experimental results revealed that the maximum thermal efficiency of the S-OTEC/AC system could reach 2.10%, which was 1.91 times higher than the OTEC/AC system. For the OTEC/AC and S-OTEC/AC systems, the maximum cold energy utilization efficiency was 4.12% and 10.09%, and the maximum isentropic efficiency was 18.81% and 76.84%, respectively. The minimum payback period for the S-OTEC/AC system was 13.90 years, which was much lower than the 18.40 years of the OTEC/AC system. Additionally, the maximum primary energy saving achieved by the OTEC/AC system was 0.53 kW, while the S-OTEC/AC system reached a higher value of 1.56 kW. From the results, the superiority of the S-OTEC/AC system over the OTEC/AC system was confirmed. This work not only provides data references for the actual operating characteristics of the S-OTEC integrated system, but also provides a new technical way for comprehensive utilization of ocean temperature difference energy. • 1 kW class S-OTEC/AC experimental system was built for the first time. • The first 4 E analysis was used to characterize S-OTEC/AC with experimental data. • The S-OTEC/AC system has a thermal efficiency of up to 2.10%. • The S-OTEC/AC system achieves a cooling energy utilization of 10.09%. • The S-OTEC/AC system is superior to the OTEC/AC system in all aspects. [ABSTRACT FROM AUTHOR]

• This paper presents an experiment on solar-powered air conditioning. • The study compares two scenarios: on-grid and off-grid, offering insights into their respective performances. • Evaluation metrics include solar fraction, energy consumption, and operational time fraction. • The solar-powered air conditioning system exhibits superior performance under higher demand and elevated temperatures. • The economic viability of the system is attractive, enhancing its appeal and potential for widespread adoption. Air conditioning is vital in maintaining indoor comfort and improving air quality, particularly in regions with high temperatures and humidity. However, the increasing demand for air conditioning has significant implications for energy consumption and the environment. Solar air conditioning can play a vital role in mitigating such impacts. This study presents an experimental setup that utilizes a solar photovoltaic system to power an air conditioning unit. The system is installed in a 36 m2-research lab at The University of Jordan, equipped with PV panels with a capacity of 2.67 kWp, a battery pack, a charge controller, an inverter charger, and an air conditioning unit. Two testing scenarios are conducted: an on-grid system connected to the electrical grid and an off-grid system operating independently. A clear sky day and a partially cloudy day were selected for each scenario in testing. The results were evaluated based on the solar fraction, energy consumption, and operational time fraction (OTF). The solar fraction was found to be higher during periods of higher demand and ambient temperature, and the average OTF was 70 % for all trials. In off-grid trials, the system had maintained operation solely on PV power during the studied load profile in the clear sky day. In contrast, limitations in charging power caused system shutdown in the partially cloudy trial. An economic analysis for the local payback period (PBP) was conducted based on the Hourly Analysis Program and PVsyst software simulation, which shows an attractive simple local PBP for on-grid and off-grid systems of 6.91 and 6.4 years, respectively. [ABSTRACT FROM AUTHOR]

Natural cooling energy and high-efficient radiant cooling techniques are essential to mitigate energy resources shortage crisis, breakthrough on traditional convective air-conditioning systems in isolation between indoor and outdoor environment with high indoor air quality. In this paper, a polyethylene aerogel (PEA) and phase change material (PCM) integrated novel Trombe wall was proposed, involving natural cooling energy harvesting, cooling energy storage, indoor ventilation and radiant cooling. A two-dimensional unsteady numerical model based on surface-to surface (S2S) radiation model and effective specific heat capacity method was developed in the commercial software Ansys Fluent to evaluate the cooling performance and dynamic heat-transfer mechanism of the novel Trombe wall. Subsequently, climate-responsive operation strategies on ventilation modes were proposed to maximize natural cooling energy utilization and fresh air supply. Parametrical and comparative studies were conducted on optimal structural design and robust operation. Our results showed that, with the novel design and advanced operation strategies, passive cooling capacity of 0.64 kWh/m2·day can be provided, together with fresh air supply of 2705.2 kg/day (1.4 m2 Trombe wall), corresponding to air change rate per hour (ACH) of 1.15. In terms of active cooling system, the integration of PEA and PCM can effectively prevent moisture condensation and shift peak cooling load. Hence, radiant cooling capacity of 0.99 kWh/m2·day and radiant cooling ratio of 47 % can be achieved by the novel Trombe wall, with electricity consumption only at valley period. Moreover, economic saving of 55.0 CNY/day and decarbonization potential of 23.8 kg CO 2,e /day can be achieved when the novel Trombe wall is integrated into a typical office building in subtropical climate Guangzhou. This study provides a novel structural design and optimal operation strategies on a Trombe wall, together with guidelines on techno-economic-environmental performance improvement, promoting effective natural cooling energy utilization and energy-flexible/efficient radiant cooling for decarbonization of buildings in cooling-dominant regions. • A novel Trombe wall for natural cooling energy harvesting and radiant cooling. • An unsteady numerical model for thermodynamic analysis. • Passive cooling capacity of 0.64 kWh/m2.day and fresh air supply of 2705.2 kg/day. • Radiant cooling capacity of 0.99 kWh/m2·day and radiant cooling ratio of 47 %. • Daily CO 2 reduction of 23.8 kg and economic saving of 55.0 CNY in a typical office building. [ABSTRACT FROM AUTHOR]

This paper uses an interview study in Doha, the capital city of Qatar, to consider the role of qualitative methods in identifying how human relationships with air-conditioning are influenced. Drawing on discussions with three groups of comparatively affluent residents who spent significant amounts of time in air-conditioned spaces, it makes four points to researchers hoping to encourage less energy demanding lifestyles. The first is that 'comfort is only one aspect' when a premature focus on comfort obscures other potentially important analytical concerns. The second is that 'air-conditioning changes cultures' when valuable insights may be gleaned from what people say about how it creates, rather than responds to, local preferences and expectations. The third is that 'comparison can be instructive' when different groups may feel themselves to possess very different relationships with air-conditioning. The fourth is that 'discussion can disappear' when those hoping to influence these relationships may benefit from understanding when and how 'conditioning conversations' currently occur and how they could be part of processes of positive local change. After substantiating these points, wider conclusions are drawn about the promotion of less energy consumptive ways of adapting to a warming world and the value of this approach to the cultural geography of air-conditioning. [ABSTRACT FROM AUTHOR]

[Display omitted] • The LCA methods and findings of 41 papers on air-conditioning systems are examined. • Retrieved studies presented discrepancies in the LCA goals and scope definition. • The global warming potential (GWP) was the most evaluated indicator across papers. • Grid-connected electrical heat pumps generally had a higher life cycle GWP. • Improvements related to AC energy sources and other life cycle aspects are proposed. Air conditioning (AC) has become the fastest-growing energy end-use in buildings worldwide, and its adoption is expected to increase further due to various socioeconomic factors and climate change. Despite this, the decarbonization of space cooling is progressing slowly; hence, the emissions burden at each stage should be examined in detail. Given this context, it is crucial to assess the environmental performance of AC systems by considering a comprehensive approach like the Life Cycle Assessment (LCA). While several studies have already targeted the LCA of AC systems, a clear overview of those studies' methodologies, assumptions, and results is still lacking. Therefore, this systematic review examined the methods and key findings of 41 peer-reviewed articles. Although the results revealed discrepancies among the goals and scope, impact assessment methods, and indicators, most articles predominantly focused on the global warming potential (GWP) impact, and its reported quantification was further analyzed. It was observed that grid-connected vapor-compression heat pumps/chillers (conventional systems) presented higher GWP impacts than other AC systems powered by renewables, which in contrast, exhibited higher impacts in some toxicity and resource depletion-related indicators. However, the share of GWP showed different distributions, as the pre-operation emissions of solar-powered AC systems (either PV or thermal) were higher than those of conventional systems, mainly driven by reduced energy consumption usage. This review concludes with some recommendations for each stage of the life cycle. Since the operation phase generally showed the highest impact, more efforts should be devoted to accelerating the transition to a 100% clean electricity power system at a national scale. In contrast, the need to power AC systems with on-site renewables should be carefully assessed based on the context. [ABSTRACT FROM AUTHOR]

• A two-layer framework is proposed for building HVAC and associated multi-energy consumption optimization. • 100% renewable complementarities are proposed for building multi-energy supplies. • A R-C thermodynamic network is formulated to model the building HVAC. • AC slow charging and DC fast charging types of EVs are considered and managed via a novel real-time supply–demand pricing. Building heating, ventilation, and air conditioning (HVAC) and associated energy consumption make up the more and more important part of the world, whose reduction provides a cost-effective path to the "dual carbon" goal. This paper proposes a two-layer management of HVAC-based multi-energy buildings under proactive demand response of fast/slow-charging electric vehicles (EVs). In this paper, the building HVAC is mathematically formulated via a R-C thermodynamic model, which coordinates with multi-energy converters and storages to form a 100% renewable building. The building management is a challenging optimization problem due to its severe constraints and strong spatio-temporal couplings. In the first layer, a day-ahead multi-energy dispatch is formulated to economically optimize the electrical, heat, gas energy carriers. In the second layer, alternating current (AC) slow charging and direct current (DC) fast charging types of EVs are considered and managed via a novel real-time supply–demand pricing mechanism. After acquiring the economical dispatch references in the first layer, the second layer implements a model predictive control (MPC)-based real-time scheduling to handle the multi-energy supply–demand fluctuations. The original two-layer optimization is further handled via mixed-integer linear program (MILP) reformulation for high-efficient solving. Comparisons have shown the advantageous performances of the proposed two-layer optimization over economics and practicability. Simulations results show that the overall system operating cost can be reduced by at most 3.01% with a higher operational flexibility in building management. [ABSTRACT FROM AUTHOR]

Energy is an efficient source in the present world and it is very significant. Huge building systems such as luxury hotels, commercial complex, malls and educational institutes require chiller plants for air-conditioning purpose in their premises. In this paper, a case analysis on energy savings and efficiency improvement of a chiller plant is done for a luxury hotel building located at Chennai, Tamil Nadu, India. The building consists of carrier make 2 Nos. 633 kW/180 TR and 1 No. 1185 kW/337 TR water cooled chillers. The chiller plant system at the site consumes up to 43% of the facility's annual energy cost. To increase the energy savings and efficiency of existing system and to achieve a lower number on the Specific Power Consumption (SPC), the existing chiller plant is retrofitted with 1 No. 879 kW/250 TR Premium efficiency chiller and an energy analysis is done by simulating the proposed chiller using Chiller Plant Automation (CPA) software and by understanding the energy usage of the chiller as per the site operating load and weather conditions. With the change in chiller, the system efficiency of the hotel increased by 40% and the energy consumption reduced to 38%. [ABSTRACT FROM AUTHOR]

Hospitals are generally made by a large complex with many buildings serving different functions. These buildings such as the patient registration area, wards, operation theatre, emergency and trauma department and pharmacy operate continuously for twenty-four hours daily throughout the year, hence consuming a large amount of energy. This paper presents a pioneering case study carried out at three hospitals in Iraq, designated as Hospital A, Hospital B and Hospital C to analyze their energy intensity by determining the building energy index (BEI). This study also identified the factors affecting energy usage in these hospitals. Detailed energy audits were carried out in these hospitals, followed by desktop analysis and comparison with BEI values from selected hospitals reported in the literature. It was found that the average electricity consumed annually for a period of three years (2016 to 2018) by Hospital A, B, and C were 19,280,900 kWh, 11,958,121 kWh and 4,275,760 kWh, respectively. It was also found that more than 60% of the energy consumed in all three hospitals were by the air conditioning systems hence becoming the significant energy user (SEU). The study thus proposes methods to reduce the energy consumption in these hospitals without reducing their level of comfort. It was also found that the outside ambient temperature was the main factor that affecting the energy consumption in the building. The study concludes that the BEI values attained for the hospitals in this case study ranged from 360 to 532 kWh/m2/year, which are relatively high and hence signifies the energy efficiency measures to be implemented in these hospitals. [ABSTRACT FROM AUTHOR]

Desiccant is a hygroscopic substance generally used in the dryer and air-conditioning system as a drying agent. The function of desiccant is to remove moisture from the air to reduce the humidity of the surrounding air been conditioned. This paper presents several works on the performance of desiccant material in the drying and air-conditioning application. It puts focus on the various advantages and disadvantages of the use of desiccant as a drying agent. There are some advantages of using desiccant include consistent drying and low energy usage. However, there are several disadvantages of using desiccants which are low capacity for moisture absorption and pressure drop in solid desiccant. Solar drying applications have some advantages such as being comparatively cheaper than other methods and less risk of spoiling the product. On the contrary, drying applications have disadvantages include being lower in comparison to the original foodstuff and drying foods eventually leads to shrinkage. The advantages of using desiccant in air-conditioning applications offer dehumidified fresh air to keep the building's temperature in a comfortable range and enhances water recovery efficiency. There are disadvantages such as desiccant will substantially impact the system's performance and desiccant should be cooled after completely dried. [ABSTRACT FROM AUTHOR]

Past investigations have identified phase change emulsions (PCMEs) as potential working fluids that could be used to reduce energy consumption in heating, ventilation and air conditioning (HVAC) systems. But how PCME behaves in a fin-and-tube heat exchanger, which is commonly found in HVAC system, is still unclear. The paper focused on theoretical studies of thermal performance of a novel PCME PCE-10 in a fin-and-tube heat exchanger. The research analyzed heat transfer and flow behavior in fin-and-tube heat exchangers and the results showed that PCE-10 has several performance advantages as a cold storage medium, which provides a basic basis for the design of a new type of practical cold storage device. [ABSTRACT FROM AUTHOR]

The HVAC (heating, ventilation, and air conditioning) systems utilization has increased in the last decade. It conducts global warming which has an impact on the rising of global temperatures. An excellent air conditioning system will make the room comfortable conditions. This paper aims to investigate the mosque space with a cooling model of wallmounted air conditioning and the difference in inlet angle and air inlet velocity. The room design was constructed using SolidWorks software. Air distribution observations were created using ANSYS Workbench simulation software. The use of a supply angle of 90° results in an even distribution of air with a low inlet velocity, whereas in conditions of a supply angle of 60° requires a higher inlet speed. Thus, the uniform air distribution is able to be realized by the proper configuration which results an appropriately room temperature and saves energy usage. [ABSTRACT FROM AUTHOR]

Highlights • EnergyPlus is capable of accurately estimating the heat transfer in parked vehicles. • Spectrally selective glazing can cause an average temperature difference inside the cabin as high as 12.5 °C. • Solar-reflective opaque coating in combination with ChLC glazing can reduce the cabin air temperature up to 23.8 °C. Abstract Parked vehicles have the tendency to overheat quickly. This can lead to a negative impact on the thermal comfort of the driver and its passengers, as well as intensive use of air conditioning systems, and thus fuel consumption of the vehicle or, in the case of electric mobility, a reduced cruising range. In the search for effective measures to mitigate this effect, important guidance can be provided by the field of sustainable building design. On the one hand, inspiration can come from design strategies in terms of shapes and advanced cover materials, but this paper advocates that this can also pertain to the simulation-based design support tools that are used by building engineers. This paper first presents the results of a thermal soak test, and then uses this data to demonstrate the suitability of the building performance simulation tool EnergyPlus for predicting the thermal behavior of parked vehicles. This fit-for-purpose validated model is used to evaluate the performance of three overheating mitigation measures for two car models in two climates. The results show that spectrally selective glazing can reduce the cabin air temperature by 12.5 °C and when combined with solar reflective opaque surfaces, the reduction of cabin air temperature can reach 23.8 °C. Increased use of building performance simulation in the automotive domain can help to further optimize the overheating reduction potential of cars. [ABSTRACT FROM AUTHOR]

Highlights • One-stop archive for developments in solid desiccant coated heat exchangers (DCHEs). • Comprehensive study on the selection of desiccants and binders. • Thorough analysis on the effect of operating parameters on dynamic performance. • Detailed review of advances in mathematical modeling of DCHEs. • Discussion on the potential system-level applications of DCHEs. Abstract Rapid urbanization and higher thermal comfort requirements have sharply increased buildings' energy demands. In tropical countries, for achieving energy efficient air-conditioning, desiccant dehumidifiers, which decouple sensible and latent load, are essential. While fixed-bed and rotary wheel desiccant dehumidifiers suffer from reduced adsorption capacity and lowered heat transfer efficiencies, desiccant coated heat exchanger (DCHE) system is a promising technology that can improve the energy efficiency of the standard vapor-compression air conditioners. Moreover, DCHEs also have prospective benefits in heat pump, adsorption chiller, and atmospheric water harvesting applications. In this paper, the advantages of DCHEs over other dehumidifiers are established, and a comprehensive review of various desiccant materials and binders used in DCHEs is carried out. The possibilities of using advanced materials to achieve superior energy efficiencies are also underlined. Different methods of coating the desiccant on heat exchangers are described, and quantitative parameters required to analyze the performance of the system are presented. Operating parameters affecting the dehumidification and thermal performance are identified, and the effect of their variation on the dynamic behavior of DCHEs is elaborately studied. The significance of using mathematical models as design tools is recognized, and the underlying assumptions, applicability, and limitations of the models for simulating the complex heat and mass transfer phenomenon are highlighted. The possibility of integrating an additional heat transfer equipment such as sensible heat exchangers, heat recovery devices, solar evacuated tube collectors, cooling towers, and evaporative coolers with DCHE is also presented. Finally, the potential system-level applications of DCHEs as heat pumps, adsorption chillers, water harvesters, and standalone air-conditioners are assessed. This review paper provides an update on recent developments in desiccant dehumidification and is intended to be a "one-stop" archive of known practical solutions that DCHEs can offer. [ABSTRACT FROM AUTHOR]

Religious art, expressed through the architecture and painting of churches, is subject to the action of time, requiring preservation of the architectural and artistic heritage throughout their existence by providing adequate microclimate parameters. Functional and constructive particularities of cult buildings – large volumes constructed, high thermal inertia of the envelope elements and periodically occupied spaces with variable occupant – influence the conditions of conformation and operation of the heating and air conditioning systems. The determination of the calculation parameters and the conformation of the installation systems must take into account these particularities and consequences leading to the necessity to provide some installations with low functional inertia. The report presents an adequate method of calculation based on the thermal balance of the air in the enclosure and the envelope space, under the conditions of cyclical operation and with limited duration of the installations. The paper is within the thematic context of the doctoral thesis "Energy efficiency solutions for heritage buildings". [ABSTRACT FROM AUTHOR]

For areas with hot summer and cold winter, air conditioning is an essential tool to improve the living environment, but the traditional air conditioning needs to consume a lot of energy in cooling and heating, the fan operation noise is large and the sense of blowing will be uncomfortable. This paper briefly introduced the basic structure of a ground-source heat pump-floor radiant air conditioning system and the control strategy which was used for regulating the operation of the air conditioning system. Then, in order to ensure the appropriate comfort and reduce energy consumption, the control strategy was optimized. An experimental room in Xining, Qinghai province, was taken as an example for analysis. The results showed that the thermal comfort under the control strategy proposed in this study was more stable at the moderate degree and the temperature was slightly higher under the traditional control strategy, although the indoor temperature fluctuation under the optimal control strategy was large and the temperature was slightly lower than that under the traditional control strategy; under the control strategy proposed in this study, the air conditioning system had shorter operation time and less power consumption. [ABSTRACT FROM AUTHOR]

Traditional air conditioning may be inappropriate for electric vehicles due to its moving parts noise besides using chlorofluorocarbons that harm the environment. In addition, it consumes a significant portion of the stored energy in batteries, reducing the vehicle's driving range. So, in this paper, a novel design of thermo-electric cooling (TEC) system coupled with a photovoltaic (PV) panel replacing the vehicle roof is studied. This system consists of a sandwich of PV panel outside the vehicle and TEC inside with a heat sink system integrated between them. The air temperature variation in the cabin during the daytime is predicted by solving a complete mathematical transient thermal model of the whole system before and after mounting the cooling system. The air streams through the vehicle moving are exploited to improve the TEC and PV system performance. The system performance is investigated for different cases during the day with and without including the PV output power and for the vehicle parks inside or outside. The results indicate that, for each scenario, the number of used TEC modules influences the system performance where the best number varies between 128 and 98. Coupling the PV panel with the TEC system reduces the daily required energy from batteries by about 19%. Running the TEC system during parking from 8 to 10 am decreases the cabin air temperature from 47.5 to 34°C while the input power declines by about 45%, which reduces the interior temperature to 25°C in 10 min (transition time). The contribution of the PV panel based on the studied conditions can increase the range of the vehicle by 10.4 km/day and about 160kWh/year energy saving. The reduction in the input power during transition time reaches 27.8% when the vehicle speed increases from 30 to 60 km/h, while this ratio declines to 10.8% as the vehicle speed rises from 60 to 90 km/h. During vehicle moving, powering the TEC system by the PV panel only can prevent the cabin temperature from rising over 40°C, whereas during parking, there is an optimum fan air velocity that gives the maximum reduction of the cabin temperature. • A novel design of a thermo-electric air conditioning system for electric vehicles is studied. • Contribution of the PV panel reaches 19% of the daily energy consumption in some scenarios. • PV panel increases the range of the vehicle by 10.4 km and can save 160kWh/year. • The best number of TEC modules is about 128 for scenarios 1 and 2 and 98 for the others • Power the TEC by PV power in parking reduces the vehicle temperature less than ambient. [ABSTRACT FROM AUTHOR]

In hot and humid areas with high solar radiation intensity, the use of air conditioning systems on the basis of desiccant materials such as solar desiccant cooling systems with a view to reducing energy consumption and economic saving can be a good alternative to conventional air conditioning units. In this paper, in order to offer a cooling load of a sample space in the city of Bandar Abbas, which has a high latent load and high radiation intensity, solar absorption cooling cycle has been considered as the base cycle, and two absorption cooling cycles were designed for comparison. Then the three cycles were modeled in the TRNSYS software, studied technically and economically, and at the end the best cycle has been selected. In terms of current energy prices, application of solar energy in Iran is not economically feasible, so the solar absorption refrigeration cycle has been considered as the basic system for the cycle's comparison. Modeling of the expressed cycles was done in TRNSYS software. The basic cycle has been composed of two main parts of cooling by absorption chillers and providing the required heat supply by the solar collector, and also two desiccant dehumidification cycles have been added by a desiccant dehumidification system. In the economic analysis of the three systems, the costs estimation during lifetime (LCC) method also has been used. As a result of this modeling and due to the Act to amend energy prices, the cooling system with the help of desiccant wheel and using returned water of chiller's generator as the regeneration source, with an annual energy saving of about 29.1%, 29.1% (1,371,980 m3) of natural gas consumption has been saved and the amount of 18/15% (156,667$) cost savings over 20 years compared to the base period, has been selected as the most efficient cooling system. [ABSTRACT FROM AUTHOR]

Coefficient of performance of air conditioning system is the ratio of cooling capacity and power consumption, and also is an important parameter to characterize the performance of the system. Based on an actual ground source heat pump system in Wuhan, China, this paper calculated the coefficient of performance of the system under long-term continuous cooling operation and then evaluated the performance of the system through experiment. The continuous testing time ranged from June 1, 2017, to June 15, 2017, and the outside air temperature ranged from 21 °C to 32 °C during the testing progress. The experimental results show that the coefficient of performance of the system changes non-linearly with time, and varies greatly with the atmospheric temperature. The results also show that the coefficient of performances average value of the system is about 3.3, and the system has good performance under refrigeration conditions. This paper helps to understand the changes in the distribution characteristics of the coefficient of performance of the ground source heat pump system and promote the wide application of the ground source heat pump system. [ABSTRACT FROM AUTHOR]

This paper describes a method for residential water use modeling predicated on metered energy data. Actual measured hot water volumes for major indoor consumption are used to verify and adjust the outputs in gallons of hot water consumption based on climate variables, water heater technical features, and set-point and intake temperatures. Three independent datasets for residential energy (RECS 2009), water heater efficiency (Air-conditioning, Heating and Refrigeration Institute-AHRI), and end-use domestic water (Residential End Uses of Water, Version 2-REU II) are applied to identify specific demographic, built environment and geographic factors that relate patterns of energy demand to water consumption. The proposed model acts within the broader Integrated Urban Metabolism Analysis Tool (IUMAT), a system-based analytical framework for evaluating the environmental performance of the built environment. The method described in this paper offers an alternative approach to residential water consumption modeling by implementing volume of hot water consumption as a proxy for indoor water use. It provides utilities with the potential to parse and prioritize energy and water conservation measures. [ABSTRACT FROM AUTHOR]

Heating, ventilation and air conditioning (HVAC) systems play an essential role in demand response (DR) programs. In this paper, a fuzzy controller is designed to adjust the HVAC set-points optimally. The aims of the designed controller are multifold: to save energy, to improve user's comfort, and reduce HVAC electricity costs. In the current research, indices such as daily energy cost, minimum and maximum home temperature, energy usage, energy usage during peak hours, and user's comfort are proposed and discussed for the evaluation of HVAC function. In addition, the effect of different pricing schemes such as fixed pricing (FP), time-of-use pricing (TOU), and real-time pricing (RTP), are analyzed. Further, the adaptability of the proposed model enabled us to investigate users with different attitudes toward welfare and cost. Finally, the effects of set-point and dead-band width are discussed. The results show that the proposed controller reaches the pre-determined aims successfully. Abbreviations: HVAC: Heating, ventilation, and air conditioning; FP: Fixed Pricing; TOU: Time Of Use; RTP: Real Time Pricing; PR: The HVAC system energy consumption cost in a day; UC: The total time that the user experiences an uncomfortable situation in a day; T_min: The minimum RealFeel Temperature experienced in a day by the user; T_max: The maximum RealFeel Temperature experienced in a day by the user; ECP: Energy consumed by the HVAC system during peak hours; EC: Energy consumed by the HVAC system during a day [ABSTRACT FROM AUTHOR]

Summary: A tremendous increase in the industrial and commercial applications of low voltage variable frequency drives (VFD) has been observed in the last decade. VFD are mainly used for energy saving and reliable speed control of industrial motors in an electrical system. However, power quality issues are becoming more apparent due to the installation of VFD. In this paper, a nonintrusive technique has been employed to determine the optimum operation of VFD system for improving the performance of heating, ventilation, and air conditioning centrifugal chiller system. The effect of load and speed ratios of VFD systems on total harmonic distortion (THD), power factor, distortion loss ratio, temperature, and efficiency has been investigated. The measurement of these parameters has been carried out by performing a series of experiments under variable operating conditions. The binomial relations have been developed between the various performance parameters and the operating conditions. Based on experimental results, optimum operating conditions have been proposed and implemented for the VFD system. Moreover, the results have been compared with the existing operating conditions and indicate a considerable improvement in THD, power factor, distortion loss ratio, efficiency, and the annual cost of energy consumed. [ABSTRACT FROM AUTHOR]

In this paper, we forecast residential electricity consumption in Brazil considering the variability in consumption behavior in different regions. In order to do so, we use a bottom-up approach to estimate long-term electricity consumption that considers three technology-driven scenarios: one assuming reference efficiency development, another one based on the Brazilian government's predictions, and the third one assuming high efficiency. The results show an increase of residential electricity consumption due to the increasing appliance ownership rate, especially air conditioning, as well as the increasing number of households. In addition, it is shown that 96 TWh of electricity could be saved in the highest efficiency scenario due to significant efficiency gains between 2016 and 2050. Further, the results indicate the southeast of the country has the highest potential for consumption reduction: by 27% in the most efficient scenario. This work is the first to use a bottom-up approach to forecast the residential electricity consumption by region and by technology-driven scenarios in Brazil. With this methodology, it is possible to indicate which types of appliances should be targeted by policy makers when designing energy efficiency incentives. Hence, this model can be used as a roadmap to achieve the desired efficiency gains in Brazil. [ABSTRACT FROM AUTHOR]

• A comprehensive parametric study of roller shades and cellular shades. • Identify key parameters affecting window attachment's energy performance through simulation results. • Sensitivity analysis of different parameters. • A new index for a unified assessment of different window attachments. This paper investigated the energy performance of window attachments and analyzed the impact of window attachments' parameters on air conditioning energy consumption of residential buildings in a cooling-dominated city (Houston) and a heating-dominated city (Minneapolis). Roller and cellular shades were selected as research objects in this study. Nine parameters related to window attachment energy performance were chosen as the probable important influence factors for the parametric study. Three values, high, medium and low levels, were set for each parameter, resulting in a total of 9520 (roller) and 9072 (cellular) combinations respectively. The optical and thermal properties of each combination were calculated with Berkeley Lab WINDOW program before coupling with an EnergyPlus typical residential building model. Based on simulation results, an annual energy performance (AEP) index was proposed to rate the energy saving potential of window attachments. Key parameters which have significant impacts on air conditioning energy consumption were determined through the parameter sensitivity analysis. The research results indicated that solar transmittance and solar reflectance are the most influential factors to the energy performance of window attachments among the nine selected parameters. The current cellular shade could achieve the AEP h and AEP c of 0.19 and 0.12. Among all combinations, the best AEP h and AEP c of cellular shades are 0.68 and 0.89, respectively. Besides, as for roller shades, the current level of AEP h and AEP c are 0.14 and 0.09, and the optimal AEP h and AEP c are 0.43 and 0.79. [ABSTRACT FROM AUTHOR]

Energy consumption has drastically increased in buildings in several places over the last decade owing to economic growth and population increase. Substantial energy saving can be attained if these buildings are designed in a proper way. This paper presents a case study about energy-efficient building methods that can be applied in Oman. A residential building was taken as a case study which was evaluated using DesginBuilder software. Several energy efficiency measures (EEMs) such as thermal insulation in walls and roof, high-performance glazing, external shading, LED lights and energy-efficient air conditioning were evaluated. Total energy consumption was reduced by as much as 37%. Adding 6 kW PV and solar water heater can reduce the annual consumption by more than half when compared to the business as usual case. In addition to the technical feasibility, the design with EEM and renewable energy systems was found to be economically attractive. The results from this study provide energy-efficient design guidelines for residential sector in hot climates. [ABSTRACT FROM AUTHOR]

In order to improve energy efficiency and overcome the shortcomings of single refrigeration technology, a new type of composite refrigeration air-conditioning system driven by low grade energy is proposed:solar energy refrigeration and dew point evaporative cooling coupling air-conditioning system. Take a project in Nanjing as an example. The cooling capacity, power consumption and coefficient of performance of dew-point evaporative cooling subsystem and solar ejector refrigeration subsystem are calculated and analyzed respectively. By comparing the Pcop with indirect evaporative cooling-ejector refrigeration air conditioning system, it is concluded that the system performance of the proposed system increases by 6.38%, and the energy saving is about 6%. Compared with the traditional mechanical compression refrigeration system, the Pcop of the proposed system is increases by more than 70% and the power consumption is reduced by 44%. In the last part of this paper, the initial investment and operating cost of the composite system was analyzed, showing that the system can save 476.5 RMB annually, with a payback period of 6 years. It is economical and environmentally friendly. [ABSTRACT FROM AUTHOR]

Heat-pump liquid desiccant air conditioning (heat-pump LDAC) systems can provide effective control over indoor air humidity and provide healthy environments for occupants. Although several studies have been recently conducted on heat-pump LDAC systems, no information is available in the scientific literature about how to design, size, and operate these systems to optimize energy efficiency. A novel thermodynamic analysis for heat-pump LDAC systems is developed and presented in this paper. The thermodynamic analysis is aimed to guide engineers and researchers to identify optimal operating points for the design, sizing, and operation of heat-pump LDAC systems. This thermodynamic analysis reveals a new fundamental capacity matching index for heat-pump LDAC systems that optimizes energy efficiency (increasing COP by 50%). The proposed thermodynamic analysis is demonstrated in this study on a heat-pump membrane LDAC system, which uses two liquid-to-air membrane energy exchangers (LAMEEs) as the dehumidifier and regenerator. [ABSTRACT FROM AUTHOR]

In this paper, PSO-OMRC model is proposed for heating ventilation and air conditioning (HVAC) system. The PSO-OMRC predicts SPT in HVAC for energy saving and thermal comfort of persons in room. PSO-OMRC used data collected from temperature, humidity, PIR, and thermal camera sensors in HVAC installed rooms for SPT prediction. In existing HVAC systems, SPT is constant and consumes more energy. Moreover, SPT prediction using traditional machine learning algorithms considers various parameters such as room temperature, humidity and person count in room. Existing algorithms considers the above parameters for energy saving in HVAC and thermal comfort for persons, whereas other parameters such as room walls and ceiling temperature, human body temperature need to be considered for SPT prediction and for energy saving in HVAC. The PSO-OMRC model predicts the SPT based on number of occupants and microclimatic conditions such as environment temperature, humidity, room wall temperature and ceiling temperature. From experimental results, the utilization of the thermal image occupant model provides significant energy savings in the PSO-OMRC model. In nano coated room, PSO-OMRC model is evaluated with the implementation of a thermal image occupant model to improve energy savings, resulting in approximately 25.2% of energy savings while maintaining the level of thermal comfort. • Microclimatic and occupant data-based setpoint temperature prediction in HVAC. • Gaussian Process Regression algorithm is used to predict setpoint temperature. • The proposed PSO-OMRC model provides thermal comfort for occupants. • Nano coated room has considerable energy savings with PSO-OMRC model in HVAC. [ABSTRACT FROM AUTHOR]

• Propose a novel machine learning-based model predictive control (MLB-MPC) framework with predictive inputs of cooling load and outdoor wet-bulb temperature. • Obtain the optimal match of prediction models and optimization algorithms for improving the performance of the MLB-MPC. • Investigate the impact of disturbances on the performance of global optimization. • Achieve an energy-saving ratio of 7.1% for the air-conditioning system when compared with the measured operation data. The dynamic optimization of key setpoints (e.g., supply water temperatures of chillers and cooling towers, or indoor temperature and humidity) can track the efficient performance point of the air-conditioning system (ACS), thus obtaining a great energy-saving effect. The model predictive control is an effective way to precisely adjust these setpoints. However, most of the existing studies focused on simple linear strategies, e.g., experience-based, rule-based, or component-based, which results in unsatisfactory energy efficiency. Aiming at this, the paper proposed a novel machine learning-based model predictive control (MLB-MPC) framework with predictive inputs of disturbances. The framework first employed the grid search and cross-validation to optimize the total energy consumption prediction models (TECPMs), which were built by data-driven models (e.g., multiple linear regression, artificial neural network, support vector regression (SVR), and random forest). And then the optimization performances of each TECPM to the controlled variables were obtained by using different optimization algorithms (e.g., genetic algorithm, particle swarm optimization (PSO), and simulated annealing). Finally, the optimal match of TECPMs and optimization algorithms was achieved by trade-off among prediction accuracies, optimization accuracies, and optimization time. The case studies demonstrated that the optimal match for the MLB-MPC is SVR and PSO as they had the highest prediction accuracy (mean absolute percentage error of 2.5%) and shortest optimization time (41 ms/per) and optimization accuracies with little difference. After adopting the optimal match, the MLB-MPC with predictive disturbing inputs achieved a great energy-saving ratio of 7.1% for the ACS, which was only less than the MLB-MPC with ideal disturbing inputs by 0.4%. This indicated that exact predictions of disturbances (e.g., cooling load and outdoor wet-bulb temperature) are important for the MLB-MPC. The proposed MLB-MPC framework would provide a method for improving the energy efficiency of ACSs. [ABSTRACT FROM AUTHOR]

This paper presents new metrics to measure the effect of thermal mass on the energy required to heat and cool buildings. Previous studies have been flawed as they have not considered the interaction between intermittent occupancy and thermal mass, which has a significant impact on overall energy use. However, existing parameters do not adequately capture these effects, so the new metrics developed in this paper are used to analyse the impact of thermal mass in hot climates with active cooling, and cold climates with active heating. The results agree with existing literature that high thermal mass structures are likely to be effective in hot climates; however, in cold climates the drawbacks of high thermal mass likely outweigh the advantages, and high thermal mass can cause an increase in energy use. This finding has implications for the design of buildings in cold climates, and contradicts the commonly-held assumption that high thermal mass is correlated with low energy use. The new metrics (transient energy ratio and effective U -value) provide a generalisable method to quantify these effects. They are further used here to analyse the dynamic performance of heavily insulated buildings and show that high thermal mass often leads to higher energy use in cold climates. [ABSTRACT FROM AUTHOR]

There has been an increasing concern on thermal comfort in sleeping environments and its associated energy use in the past few years. To improve the thermal environment and to reduce energy use of air conditioning in bedrooms, applications of task/ambient air conditioning (TAC) systems were proposed and studied previously. It’s indicated that the TAC system can be well integrated with a bed. Due to the variation of the envelope heat gain in a bedroom during night, it is necessary to study the thermal environment inside a bedroom and the energy use of a TAC system for the bedroom at varying envelope thermal loads. Therefore, this paper reports on a numerical study on a TAC system applied to a bedroom with different envelope heat gains. The influences of envelope heat gain on energy consumption of the TAC system and the indoor thermal comfort were studied in this paper. The research results show that at supply air flow rate ( Q s ) of 50 l/s, energy consumption was increased from 47.78 W to 213.11 W, and the PMV value was increased from −1.69 to −1.29 with the increase in envelope heat gain from 3.11 W to 155.6 W. To make PMV equal to zero under different envelope heat gains, linear regression models between supply air parameters and PMV were built and solved. The obtained values form curves where PMV = 0 and give a guide for operation of the TAC system. It was found that the calculation of energy consumption on these curves depends only on envelope heat gain. [ABSTRACT FROM AUTHOR]

This paper presents an energy-saving controller for automotive air-conditioning/refrigeration (A/C-R) systems. With their extensive application in homes, industry, and vehicles, A/C-R systems are consuming considerable amounts of energy. The proposed controller consists of two different time-scale layers. The outer or the slow time-scale layer called a set-point optimizer is used to find the set points related to energy efficiency by using the steady state model; whereas, the inner or the fast time-scale layer is used to track the obtained set points. In the inner loop, thanks to its robustness, a sliding mode controller (SMC) is utilized to track the set point of the cargo temperature. The currently used on/off controller is presented and employed as a basis for comparison to the proposed controller. More importantly, the real experimental results under several disturbed scenarios are analysed to demonstrate how the proposed controller can improve performance while reducing the energy consumption by 9% comparing with the on/off controller. The controller is suitable for any type of A/C-R system even though it is applied to an automotive A/C-R system in this paper. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel approach to control CO 2 and H 2 O composition in an enclosed environment. • A cyclic CO 2 adsorption process and dehumidication units are considered. • The mathematical model shows superior performance of the proposed system. • Carbon footprint of the system is discussed with scale-up study. • Influence of parametric uncertainties in the model is discussed. Rapid growth in global energy consumption has raised concern on the environmental impacts such as ozone layer depletion and climate change. Enclosed space, such as commercial buildings, accounts for about 40% of global energy consumption and the demand is constantly increasing due to increasing population, urbanization, and economic development. The energy demands in the building sector calls for strategic measures to develop energy efficient technologies. This paper presents a strategy to decrease energy demands inside buildings by proposing a ventilation system which regulates the enclosed air quality resulting in reduced air conditioning. The system consists of multiple adsorption beds with zeolite 13X monoliths for CO 2 removal, and silica gel for humidity control, inside the enclosed space. The air conditioning system results in decrease in energy requirement and improvement in economics by 55% as compared with conventional ventilation system. The model is scaled up to the size comparable with total office inventory of New York City, and the reduction in carbon emissions by introducing the air composition control system for New York City is equivalent to replacing 57 million incandescent light bulbs by LEDs. This paper concludes that the air conditioning system proposed in this study results in the improvement in performance as compared to a conventional ventilation system and could reduce energy consumption inside commercial buildings. [ABSTRACT FROM AUTHOR]

The American Society for Heating, Refrigeration, and Air Conditioning Engineers (ASHARE) prescribes fixed ventilation rates for the operation of heating, ventilation, and air conditioning (HVAC) systems, which is sub-optimal in terms of controlling indoor air pollutants and energy consumption. This paper relies on a physics-based model of a residential house to predict the concentrations of indoor pollutants such as ozone, formaldehyde (HCHO), and particulate matter (PM) as function of time, outdoor conditions, and indoor emissions. The model captures real-world scenarios such as pollutants entering the house from ambient air through an air handling unit (AHU) and pollutants emitted in the house. A dynamic optimization problem is then formulated and solved to calculate the optimal ventilation rate at each time instant, that minimizes the total energy consumption, while maintaining the indoor pollutant concentrations below or as close as possible to their respective acceptable thresholds. For the considered example day, operation under optimized conditions reduces the peak pollutant concentration by 31%, time of exposure to undesirable concentrations by 48%, and energy consumption of the AHU by 17.7%. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A consolidated advanced adsorbent is studied. • N-butane has the highest relative potential exergy for power generation. • This novel system is multi-function in providing air conditioning/refrigeration/heat pump heat-power generation. • The total exergy efficiency can be improved from 0.15 to 0.31. Abstract The shortage of fossil fuel, greenhouse gases emission, air pollution and global warming have attracted more and more researchers' attention on the adsorption technology, which utilizes low temperature thermal heat of solar thermal energy and waste heat. Moreover, the usage of natural materials as refrigerant such as water and methanol adds to its advantage. However, the low coefficient of performance and specific cooling power limits its further application. This paper proposes a novel combined adsorption system, which can provide the functions of air conditioning/refrigeration/heat pump heating and ammonia/organic expanding power generation. In addition, the consolidated advanced adsorbent is used in this system, the effect of which is investigated. The author also analyzed the most suitable organic for organic Rankine cycle in this system. The results reveal that the organic of N-Butane has the highest potential exergy and the most appropriate work pressure. The cooling exergy efficiency in the working modes of air conditioning, refrigeration and heat pump heating are about 0.18, 0.13 and 0.24, respectively. The simulation results indicate that, compared to the system with only cooling effect, the total exergy efficiency of the combined system can be improved from 0.15 to 0.31, because of the additional expanding power generation effect. [ABSTRACT FROM AUTHOR]

Abstract Liquefied natural gas (LNG) is widely used in many countries around the world primarily as a mode of transport for natural gas. However, massive amount of energy (around 830 kJ/kg of LNG) is wasted during the regasification process in the LNG regasification terminals. Therefore, the technologies to utilize the LNG cold energy have received significant attention over recent decades. In this paper, we review various studies on the current LNG cold energy utilization systems, including power generation, air separation, desalination, cryogenic carbon dioxide capture, and NGL recovery. Utilizing LNG cold energy on such systems can improve the energetic and exergetic efficiencies significantly. Furthermore, several potential applications to utilize LNG cold energy in the future are proposed and discussed to broaden the perspectives of the researchers in the community. Among these potential applications, recovering LNG cold energy on cold chain for food transportation, data center cooling and hydrate based desalination are very promising. Finally, the limitations and challenges to be addressed for LNG cold energy utilization are discussed in detail. Graphical abstract Image 10764500 Highlights • Abundant amount of cold energy can be recovered during LNG regasification. • A comprehensive review on the state-of-the-art LNG cold energy utilization systems is provided. • LNG cold energy can be utilized for power generation, air separation, air conditioning and desalination. • Technologies to utilize LNG cold energy are analyzed and compared. [ABSTRACT FROM AUTHOR]

As an important subsystem in air-conditioning system, water system connects the chiller and terminal equipment. Therefore, it is necessary to develop an accurate thermal model for chilled water pipe to create the suitable indoor temperature and humidity environment. In this paper, the thermal model of the pipe was considered by utilizing the simplified thermal time-delay state-space model with the mass, energy balance, and heat consumption equations. Based on this improved model, the preview control as control strategy for water pipe temperature was proposed, and its robustness and stability were discussed. Subsequently, the performances of this model and control strategy were tested in a fan-coil system simulating with MATLAB and TRNSYS (Transient System Simulation Program). Explicitly, the results show that this model accurately predicts the thermal characteristic, and the average mean squared errors for water temperature were 11.14% and 12.82%, respectively. Meanwhile, the tracking effect of valve controller was better than the control strategy with no preview control. [ABSTRACT FROM AUTHOR]

Highlights • HVAC system, the objective function, limit conditions in the matrix or vector form. • A universal set of constant parameters, decision variables and limiting conditions. • System analysis and matrix calculation in the optimization of the HVAC system. • A global form of the objective function that captures all HVAC subsystems. Abstract The new complex selection strategy of low energy ventilating or air conditioning system (HVAC system) from a holistic perspective is presented in the paper. The strategy carries out the solution of the whole optimization problem that consists of the HVAC system model, optimization model and optimization procedure. The practical function is the starting point of the optimization problem, whereas the energy optimal variant of the HVAC system is the final stage. Universal sets of constant parameters, decision variables and limiting conditions of the HVAC system were formulated for the mathematical description of the problem. In optimization procedure, the sets of all variants and permissible variants of the HVAC system were defined based on the system analysis with the use of matrix calculation. The objective function was determined by the use of the simulation model of the HVAC system where the algorithms of energy optimal control is determined by dynamic optimization. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a mathematical model to enable a more in-depth understanding of the combined heat and mass transfer processes of a counter-flow indirect evaporative cooler operating in semi-arid regions. A series of simulation was conducted to compare the performances between a single-purge and four-purge configurations. Furthermore, the effect of several parameters on the performance of the single-purge configuration was investigated under the baseline condition. The developed model was validated against experimental data from literature to within 2% discrepancy. Key results revealed that the single-purge configuration produced higher cooling capacity (around 20% higher), as well as higher dew-point effectiveness under the same operating conditions. A parametric study was also made on the single-purge configuration. The results revealed that lower product air temperature and higher dew-point effectiveness were achieved with longer channel length and larger purge ratio. However, the maximum cooling capacity approached its maximum with longer channel length and 35% purge ratio. [ABSTRACT FROM AUTHOR]

Abstract In tropical climates, the energy consumed by ventilation and air conditioning can exceed 50% of the total consumption of a building. Demand for cooling is rising steadily, driven mainly by growing incomes in developing economies, and is expected to also increase with climate change. Tropical, coastal areas with narrow continental shelves are good sites for the implementation of Seawater Air Conditioning (SWAC), a renewable and low CO 2 emission cooling process. This paper presents the existing SWAC projects around the world and gives details on the technology. Data on ocean temperature profiles, ocean bathymetry and world surface temperature are processed with the intent of estimating the world potential of SWAC. The results present the required distance from coast to reach seawater with a temperature of 5 °C or less. This is combined with the potential demand for air conditioning, taking into account surface air temperature and a set SWAC design for cooling from 30 to 20 °C. The pipeline length, seawater depth and capacity factor are then used to estimate the costs of SWAC projects around the world. It is concluded that the locations with the highest potential for SWAC are intertropical islands and some continental locations. Highlights • This renewable source is ideal for tropical coastal areas with narrow continental shelves. • The energy in a m3/s of SWAC can be equivalent to 49 ha of solar PV or 42 MW of wind turbines. • A novel SWAC potential model is developed to identify the most promising sites worldwide. • Capacity factor, pipeline length, depth extraction and cost estimates are presented in detail. • The cheapest SWAC project costs $0.0185/KWh t and is located in Nauru, Pacific Ocean. [ABSTRACT FROM AUTHOR]

Heating and cooling energy consumption of buildings accounts for a large portion of global energy use and is significantly affected by the air conditioning system in the buildings. In order to predict the energy performance of buildings, various energy simulation engines have been developed and recently applied to the BIM data of buildings. However, due to the interoperability between them, estimating heating and cooling energy at the design stage of the air conditioning system, in collaboration with the building model, still lacks of efficiency and accuracy. In this paper a highly efficient design framework with enhancement of interoperability that enables the designing of a variable refrigerant flow (VRF) type air conditioning system in BIM environments and to analyze its energy behavior is proposed. The framework covers i) computing the energy load of a building, ii) designing a VRF system that includes equipment selection, layout and piping, and iii) predicting energy consumption by the system with consideration of the building's thermal properties and annual weather conditions. The novelty of the proposed approach lies in the fact that the layout and piping for air conditioning system are enabled inside a BIM environment to maximize interoperability. We implemented the framework as an add-in program to the commercial BIM software and present its accuracy in comparison with the reference data provided by ASHARE. [ABSTRACT FROM AUTHOR]

Highlights • A novel hybrid desiccant cooling system with a condenser is studied. • Thermal balancing technique is applied for zero and single extraction systems. • A mathematical model of the proposed system using enthalpy pinch method is explained. • The coefficient of performance is improved by 85% using the single extraction. • The investigated hybrid system also produces fresh water as a by-product. Abstract This paper focuses on thermodynamic balancing of the regeneration process in a hybrid liquid desiccant cooling/desalination system. The thermal balancing technique is investigated by adding a single extraction between the system regenerator and condenser. This technique is considered as a potential method to reduce energy consumption and increase the hybrid system performance, dramatically. The mathematical procedure to model the proposed system using enthalpy pinch is outlined to study the effect of extraction on the hybrid system performance. The hybrid system, with a single extraction and without extraction (zero extraction), is analyzed in terms of the normalized entropy generation, local enthalpy losses, the coefficient of performance, and proper extraction location. The results show that at enthalpy pinch of 20 kJ per kg of dry air, single extraction system performance is 85.7% better than zero extraction. In addition, the single extraction produces 103.2 kg of fresh water per hour as a by-product compared to 94.2 kg per hour for the zero extraction system. [ABSTRACT FROM AUTHOR]

Air conditioners (ACs) are widely considered as good candidates to provide operating reserve. Demand response rebound, i.e., the rebound peak of aggregate power, may exist when ACs are controlled by changing the set point temperature. The rebound peak during the recovery period, named lag rebound, may cause significantly higher demand than that prior to the reserve deployment event. The rebound peak during the reserve deployment period, named lead rebound, is rarely considered in previous researches but will constrain the duration time to a short period (e.g., 10 min), which greatly limits the utilization of ACs. This paper proposes an optimal sequential dispatch strategy of ACs to mitigate the lead–lag rebound, and thus realize flexible control of the duration time from minutes to several hours. To quantify the effects of lead–lag rebound, a capacity-time evaluation framework of the operating reserve is developed. On this basis, ACs are grouped to be dispatched in sequence to mitigate the lead–lag rebound. The co-optimization of sequential dispatch on the capacity dimension and time dimension forms a mixed-integer nonlinear bilevel programming problem, in which the consumers’ thermal comfort is also guaranteed. Case studies are conducted to validate the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper proposes the design, construction, and test of a prototype R141b ejector refrigeration system. It was used as an air conditioner for a hot climate country (Thailand). The prototype machine was designed to work as a water chiller to provide thermal comfort condition for the tested room with the cooling capacity up to 4500 W. It was driven by hot water with temperatures of 90–98 °C. The condenser was cooled by water, which was provided by a cooling tower, with temperatures of 28–32 °C. CFD simulation was also employed to design the ejector. The tested results indicated that the prototype R141b ejector refrigerator working as an air conditioner was satisfactory in operating conditions consistent with a hot climate (Thailand's environment). The temperature of the air conditioned space was around 23 to 25 °C with the cooling load of 4500 W. The coefficient of performance (COP) was between 0.42 and 0.47. [ABSTRACT FROM AUTHOR]

Abstract: A one‐dimensional mathematical model is developed to evaluate the operating and design parameters of the desiccant wheel for air conditioning application. In this paper, dehumidification coefficient of performance (DCOP) and sensible energy ratio (SER) are adopted as a combined performance index to reflect the dehumidification and thermal performance of the desiccant wheel. The analysis of the results reveals that for lower SER, suitable wheel length, wall thickness, channel pitch, and channel height should be 100 mm, 0.2 mm, 3 mm, and 5 mm, respectively. These design parameters have been analyzed under different operating conditions and it was found that for higher DCOP, rotational speed, regeneration temperature, process and regeneration velocity should be 20 rph, 60°C, and 2 m/s. [ABSTRACT FROM AUTHOR]

Real-time optimal control is widely adopted in central air-conditioning systems to improve the building energy management efficiency by adjusting system controllable variables according to system operating conditions. In time-driven optimal control, optimization actions are triggered periodically, which may not be efficient when the operating conditions of central air-conditioning systems are significantly irregular. To overcome this limitation, event-driven optimal control was proposed, in which optimization actions are triggered by “events” instead of a “clock”. In event-driven optimal control, the definition of events are critical because “events” will directly affect the control efficiency and the online computational efficiency. In current literature, however, very few studies can be found on how to systematically establish a suitable event space for air-conditioning systems. This paper therefore presents a knowledge-based method for establishing event space. Case studies that were carried out in a typical commercial air-conditioning system is used to demonstrate the proposed method and its effectiveness, where real measured load and weather data were used. [ABSTRACT FROM AUTHOR]

Personally controlled air movement can maintain or enhance thermal comfort in warm environments and reduce energy consumption. Unlike controlling a personal fan, using a system of fans for multiple occupants is difficult as it is hard to find an appropriate fan speed setting that maximizes occupants' satisfaction. Since limited work has been carried out on this issue, in this paper, a novel cooperative control approach for a system of fans is proposed to provide optimized air movement for multiple occupants. This is the first time that a system of fans is controlled cooperatively in the research of built environment. The proposed approach predicts airflow in a cost-effective manner by calibrating the fans in the real environment. The operation of the fans is optimized by minimizing the worst-case deviation between the actual air speed and the desired air speed, which can be determined based on either the PMV - SET model or the occupants' feedback. This minimax-error problem is formulated as an equivalent linear programming problem which can be solved using standard methods. The proposed approach was tested in two different indoor scenarios respectively by 1) measuring air speed directly in a business conference room and 2) involving human subject surveys in a university classroom. In the first experiment, the measured air speeds after optimization are closer to the target values at all tested temperature levels (26°C, 27.5°C, and 29°C) indicating improved thermal comfort. In the second experiment, only 62% of the occupants (totally 34) are satisfied with slightly increased room temperature (around 26.5°C) before optimization, while this number increased to 94% after optimization. [ABSTRACT FROM AUTHOR]