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With the increasing demand for indoor environmental comfort, air conditioning has become an essential electrical device for modern life. To improve the comfort of indoor environment in clean-room and to reduce the operating cost of the equipment, the study proposes an improved Min-Max robust model predictive control algorithm for clean-room air conditioning control strategy. Firstly, for the comfort of indoor air conditioning, the MPC algorithm is investigated to regulate the air conditioning air supply based on indoor temperature and humidity ratio in order to control the indoor comfort of the clean-room. Subsequently, an improved Min Max robust model predictive control algorithm was proposed to control the parameters of the model, and compared and analyzed with the original algorithm. The simulation results indicated that the PMV index of the model predictive control algorithm was 0.66 at the lowest and 0.68 at the highest. The Min-Max robust model predictive control algorithm was 0.73 at the lowest and 4.3 at the highest. The improved Min-Max robust model predictive control algorithm was 0.45 at the lowest and 0.47 at the highest. The experimental data indicate that the improved Min-Max robust model predictive control algorithm has the best performance and has more obvious effect on the comfort control of clean room environment.

In this article, a deep reinforcement learning method is developed to solve air conditioning control problems through human expressions. The main contribution of this article is to design a deep reinforcement learning method for air conditioning control problems with human expressions as the input for the first time. The method aims to eliminate human sleepiness and improve people's work efficiency as much as possible. First, the air conditioning system and deep reinforcement learning methods are introduced. Second, the image processing algorithm for human expressions is described. Third, the deep Q-network method is designed to obtain the optimal control policy for air conditioning systems. Finally, simulation results are given to illustrate the present method that can effectively eliminate sleepiness and improve the work environment of people. [ABSTRACT FROM AUTHOR]

Highlights • Australia's largest appliance level consumption monitoring data set studied. • Actual contribution of air-conditioners to regional summer demand peaks analysed. • K-means clustering performed to categorize air-conditioner usage patterns. • Two scenarios considered for air-conditioner demand response at NSW State level. • Findings suggest possible NSW peak demand reductions of around 4–9%. Abstract Residential air-conditioner loads are known to be a key driver of summer demand peaks for some electricity industries. Such demand peaks occur infrequently but have potentially severe implications for network and peaking generation plant investment, and hence electricity prices for end users. Detailed assessments of air-conditioner peak demand have, however, been hampered by limited residential consumption data, and even when interval meter data is available, the complexities of other household loads and behavior. This study utilizes data from a significant appliance level consumption monitoring project in Sydney, Australia, to analyze the actual contribution of air-conditioners to regional summer demand peaks. K-means clustering is used to characterize air-conditioner load profiles across a large number of households at times of these overall demand peaks. These clustered air-conditioning load profiles, combined with a number of possible load control strategies, are then used to estimate possible peak load reductions from air-conditioner demand response across the Australian State of New South Wales. Our findings suggest that residential air-conditioning presents a significant demand response opportunity, approaching perhaps 9% of total peak demand in some circumstances. [ABSTRACT FROM AUTHOR]

This study investigated the effect of an energy saving device (ESD) on the performance of a split-type air conditioner (SAC). The ESD was fabricated using a moisture-transferring and quick-drying textile (MTQDT), a condensate pipeline, and a distributor. The MTQDT was coated on the shell surface of the compressor to absorb the condensate expelled by a condensate pipeline and distributor to enable evaporative cooling of the compressor. The SAC was tested under various outdoor air conditions (29, 32, and 37   °C; 55% relative humidity) and under a fixed indoor air condition (26   °C; 50% relative humidity), and the performance of the SAC before and after ESD installation was compared. Results demonstrated that the MTQDT effectively improved compressor cooling and the efficiency of the SAC. Compared with the SAC without an ESD under the optimal condition, the shell temperature of the compressor, high-side pressure, and power consumption of the proposed SAC were 15.1   °C, 2.7%, and 9.2% lower, respectively. Moreover, the dehumidification capacity and energy efficiency ratio of the proposed SAC were 25.4% and 7.3% higher, respectively. [ABSTRACT FROM AUTHOR]

When receiving an urgent request from a smart grid, shutting down part of operating chillers directly in the air-conditioning system in a building can achieve immediate power reduction. However, no study has addressed how to determine the number of chillers/pumps to be shut down and how to regulate the load of retained equipment systematically during DR events. This paper presents a new approach to address these issues based on three schemes. A power demand optimization scheme predicts the building cooling demand and the power limiting threshold in response to a received DR request. A system sequence control resetting scheme determines the number of operating chillers/pumps to be retained. An online control/regulation scheme ensures the system power following the expected profile by regulating the total chilled water flow delivered to the building and therefore the chiller load. It also employs a cooling distributor to distribute chilled water to individual zones concerning different sensitivities/sacrifices to temperature increases. Case studies are conducted on a simulated dynamic building air-conditioning system. Results show that, during DR events, the proposed strategy can achieve the expected power reduction (i.e., about 23%) and also maintain acceptable zone temperature even though uncertainties exist in the prediction process. [ABSTRACT FROM AUTHOR]

This paper and its future companion papers, were aimed to develop a set of efficient and accurate enough modular tools to build a simulation test bed for the stability analysis of interacting VAV (variable air volume air-conditioning system) control loops. By providing the correlation equations between the heat flow and temperature of the two opposite surfaces, the wall model was expected to link adjacent zones effectively and efficiently. In part 1, the development of an optimal simplified 3R2C (composed of three resistances and two capacitances) thermal network model of building envelope, i.e., the wall model, was descripted. The verification showed that the simplification of one-dimensional heat conduction through a typical wall of heavy construction was acceptable. The accuracy of the optimal simplified 3R2Cmodel was satisfying, and outperformed that of the optimal 4R3C model as well as two 3R2C models which were normally used in practical applications. First and foremost, the room dimensions of the test bed with the boundary conditions in numerical scheme were designed under the principle of similarity. After validation of the numerical scheme with the high-cited scaled experiment, a series of numerical test cases simulating the potential oscillations in practical applications, were conducted. Then, the long neglected concerned frequency range within which heat flow transfer through extern wall, was determined. Finally, the part of solid wall was separated with the part of indoor air, and was developed into a flexible wall module of 3R2C model based on frequency domain regression. [ABSTRACT FROM AUTHOR]

When nuclear power plants are under accident conditions, normal air-conditioning system will cease for safety considerations. However, the equipment still generates much heat and indoor temperature will rise rapidly, which threatens the personnel safety. Therefore, massive concrete envelopes with cooling fins are expected to absorb the heat passively from the indoor air continuously. The numerical simulations were conducted to study the temperature change and distribution during a 72-hour period. The results show that indoor temperature was 298.37 K at the final hour, with the maximal increase of 6.34 K in the beginning. The massive envelopes with cooling fins can be a reliable and effective way to mitigate the temperature rise under accident conditions. [ABSTRACT FROM AUTHOR]

Taking the capillary ceiling radiation air conditioning system in radiation cooling Laboratory of comprehensive experimental building in Shandong Jianzhu University as an example, research the two different control methods which are room temperature control and water temperature control. The roof cooling model was established by using TRNSYS simulation software, two typical summer days were selected to explore the stability of the room temperature and the supply and return water temperature, research the comfort of human body and system energy consumption under two control methods. The results show that the indoor temperature of the two control methods can be stable at the design temperature of 27℃ under outdoor high temperature environment in summer. When the maximum outdoor temperature does not exceed 30℃, the temperature stability of the room temperature control method is better, the comfort of the two control methods can meet the requirements, but the water temperature control method is more comfortable. The room temperature control method is 20% ~ 25% energy saving than the water temperature control method in the two typical selected days, and is 40.5% energy saving in the whole cooling season. [ABSTRACT FROM AUTHOR]

The degree of jet entrainment is affected by the exit conditions and thus affect the air terminal device design. While investigations of jet exit conditions have been carried out by experiments and simulations, it can be considerable advanced by the theoretical analysis. Effect of velocity profile and turbulence intensity at jet exit on jet entrainment are examined based on the field synergy theory by calculating the mass transfer field synergy number, that is the synergy between the velocity vectors and the species concentration gradients for a given jet flow rate. It showed that the entrainment increases with the increase of the mass transfer field synergy number, and vice versa. The mass transfer field synergy number can be changed by the boundary conditions to strengthen or weaken the convective mass transfer of jet entrainment. This work has resulted in a better understanding of the convective mass transfer phenomenon of jet entrainment and give a guide for air terminal device design. [ABSTRACT FROM AUTHOR]

A thorough assessment is critical for understating and enhancing building energy performance. This paper presents a three-level energy performance assessment method for information-poor buildings where very limited energy use data are available. Using this method, the energy performance of a building can be assessed at multiple levels (i.e., building level, system level and component level ) based on limited energy use data and few in-situ measurement and/or catalogue data of air-conditioning systems. The core part of this assessment method is a quantitative energy performance calculation method that consists of two basic energy balances, simplified models of air-conditioning components and an optimization algorithm based on the energy balances within buildings. The proposed assessment method is well validated in a high-rise building in Hong Kong by comparing the energy performance data from the proposed method with that from detailed measurements. Results show that this method can estimate the energy performance indicators quantitatively at three levels with acceptable accuracy. [ABSTRACT FROM AUTHOR]

ABSTRACT Styrene-acrylonitrile copolymer (SAN)/acrylonitrile-styrene-acrylate terpolymer (ASA) blends (75/25, wt/wt) was toughened by blending with impact modifiers including chlorinated polyethylene (CPE), hydrogenated nitrile butadiene rubber (HNBR), and butadiene rubber (BR) and the impact property was tested at four temperatures (-30, −15, 0, and 25 °C). The combination of CPE and HNBR was imported to toughen the SAN/ASA blends, indicating that CPE and HNBR had similar toughening effect at room temperature but HNBR exhibited a better performance at low temperature. When a little HNBR was substituted by BR, the impact strength improved dramatically with the total content of impact modifiers keeping at 30 phr. After 15 phr CPE, 10 phr HNBR and 5 phr BR were employed into blends together, the impact strength reached to a peak of 14 kJ/m2 at −30 °C while the impact strength of the blends individually toughened by 30 phr CPE or 30 phr HNBR was 5 or 12 kJ/m2, respectively. The toughening mechanism showed that the low glass-transition temperature (-108 °C) of BR and the compatibilization between BR and matrix accounted for the improvement of toughness. Simultaneously, scanning electron microscopy, dynamic mechanical analysis, flexural and tensile properties, heat distortion temperature, and Fourier transform infrared spectroscopy were measured. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45364. [ABSTRACT FROM AUTHOR]

Public and commercial buildings tend to overheat and considerable energy is consumed by air-conditioning and ventilation. However, many occupants remain unsatisfied and consequently exhibit thermoregulatory behaviour (TRB),e.g.opening windows or controlling the air-conditioning. This, in turn, might negatively influence the building energy use. This paper hypothesizes that warmth acclimation influences thermophysiology, perception and TRB in a warm environment. Therefore, the effect of warmth acclimation on TRB, physiology and perception is investigated. Twelve participants underwent a so-called SWITCH protocol before and after warmth acclimation (7 days, 6 h/day, about 33°C, about 22% RH). During SWITCH, the participants chose between a warm (37°C) and a cold (17°C) condition. TRB was determined by the number of switches and the time spent in a specific condition. Mean skin temperature was recorded to assess behavioural thresholds. Thermal comfort and sensation were indicated on visual analogue scales (VAS). After acclimation, the upper critical behavioural threshold significantly increased from 35.2 ± 0.6 to 35.5 ± 0.5°C (p ≤ 0.05) and the range of mean skin temperatures at which no behaviour occurred significantly widened (3.6 ± 0.7 to 4.2 ± 0.6;p < 0.05). The total number of switches tended to decrease (p = 0.075). The present study is the first to show that prolonged passive exposure to warmth extends TRB thresholds. [ABSTRACT FROM PUBLISHER]

Various technologies have been applied on roofs to reduce the air-conditioning load in buildings during summer or in tropical areas, including cool paint, roof ventilation, mass and reflective insulation. These technologies help to reduce roof temperatures or heat transmission effectively in summer at different economic costs. It is desirable to evaluate the cost effectiveness of different roofing technologies, especially in the tropical climate. This work analyzes the heat gains of concrete-based roofs combined with different roofing technologies, as well as the cost effectiveness of these technologies in the tropical climate of Singapore. The transient roof temperatures and heat transmissions are predicted using Complex Fast Fourier Transform (CFFT) method, and the impacts of roof ventilation on heat gain are predicted using correlations proposed for convective resistance prediction via computational fluid dynamics (CFD) simulation. The daily heat gains of different roof components are hence predicted, and Life-cycle Cost Analysis (LCCA) is performed to evaluate the payback periods of different roofing technologies, including cool paint, expanded polystyrene foam (EPS), radiant barrier (RB), and roof (natural and forced) ventilation. It is concluded that the application of cool paint on unventilated roof shows the shortest payback period, and the combined use of RB and natural ventilation yields the largest energy savings in the long run. Compared with forced ventilated roofs, those passive roof technologies (cool paint, RB, air gap and EPS foam) without electricity requirement are more recommended, due to their cost effectiveness. [ABSTRACT FROM AUTHOR]

Using wireless sensor networks to collect indoor temperature and humidity data, a monitoring system is built. According to the data of the central processing unit, the state of the current room is analyzed, and the cooling capacity (heat) and air volume of the central air conditioner are calculated. Meanwhile, this system calculates the relevant fees based on the amount of cold (heat) consumed by each user, and provides a more accurate data base for the central air conditioning system for energy efficiency optimization. The results show that this system can accurately reflect the environmental status of the target room. Therefore, it is concluded that the indoor environment monitoring system based on wireless sensor network and embedded technology proposed in this paper is effective and feasible. [ABSTRACT FROM AUTHOR]

As the guarantee of comfort to people, healthy air conditioning (AC) system has been widely used in modern architecture. Meanwhile, AC system needs automatic control technology to ensure that equipment economically runs and indoor environment also gradually improves by the advance of science and technology. There are enormous challenges in automatic control technology; therefore, AC technology is effectively supported by advanced control algorithm, which can produce a variety of advanced AC control systems, and save energy at the same time. In this paper, there is a classified exposition according to the control types, system type and equipment of the AC system; also, the current research studies are analysed. [ABSTRACT FROM PUBLISHER]

Liquid desiccant (LD) dehumidification has attracted increasing attentions and its applications in air conditioning are emerging in recent years. The dynamic characteristics of the dehumidifier are essential to design and tune controllers for LD hybrid air conditioning systems. Existing research on liquid desiccant dehumidifier focuses on steady state condition. There is a lack of a computationally efficient yet accurate dynamic dehumidifier model for the purpose of control and dynamic simulations. This study develops a simplified one-dimensional dynamic model of a counter flow packed-type dehumidifier. The approach to quantifying the thermal mass of packing material and desiccant solution held in dehumidifier is developed for the first time and implemented in the dynamic model. Validation results show that the dynamic model is in better agreement with experiment than the static model. Root-Mean-Square Errors (RMSEs) between the simulation results of dynamic model and the experimental results are about 0.2 g/kg for the outlet air humidity ratio and 0.2 °C for the outlet air temperature. In addition, sensitivity analysis is conducted to investigate the effects of the thermal mass on the dehumidifier dynamics. The dynamic model and the results are valuable to design and tune controllers and dynamic simulations of the LD hybrid air conditioning systems. [ABSTRACT FROM AUTHOR]

This paper investigates the energy-efficient air conditioning supply chain, which is composed of one supplier (MIDEA) and two retailers, i.e. SUNING and GOME. With a view of market share, we measure the impact of retail prices variability in the two-echelon supply chain on the bullwhip effect. SUNING and GOME are assumed to possess the autonomy of choosing prices and separately acquire various market shares, according to which the relationship between the two prices is simply quantified. The order-up-to inventory policy and the moving average forecasting method are respectively employed by the two retailers. Furthermore, we cast light on how factors like price, market share, lead time, and autoregressive coefficient affect bullwhip effect. The results indicate that it’s inadvisable to conduct large fluctuation on price. Besides, demand dates that are more historical may actually reduce the bullwhip effect. We also find that the bullwhip effect will be bigger when the competition becomes fiercer, and there's a necessity for retailers to take measures to reduce the influence of competitors' prices. [ABSTRACT FROM AUTHOR]

Extensive studies have been done on adaptive thermal comfort for naturally ventilated buildings. However, further studies of the adaptive comfort model are needed to develop a control method for buildings with the air-conditioning systems. This study aims to extend the application of the adaptive comfort model by developing an adaptive comfort control (ACC) for air-conditioning systems. Special attention is given to testing the acceptability of the ACC to the occupants of the office buildings. Two extensive longitudinal field studies were carried out that involved 807 office workers and a total of 13,523 individual comfort votes were collected. This study reveals that it is possible to develop statistically and substantively significant adaptive comfort models for the cooling operation of air-conditioned buildings. This field study provides scientific evidence that the adaptive comfort model can be used to control an air-conditioning system without sacrificing occupants’ thermal comfort. Further field studies on air-conditioned buildings are warranted to quantify the energy use implications of the ACC. [ABSTRACT FROM AUTHOR]

The special features inherent in the development of high-temperature deformation and structural evolution in materials are investigated, using a VT22 titanium alloy of the transition class (Ti - 4.74 mass% Al - 5.57 mass% Mo - 5.04 mass% V) subjected to helical rolling + aging as an example. This treatment is found to give rise to an intragrain fine acicular martensite structure with fine inclusions of α-phase particles of size ~1 μm. It is shown that in the alloy undergoing plastic deformation at temperatures approaching the polymorphic transformation temperature, the elongation to failure is in excess of 300%. The high plasticity of the alloy in the conditions considered is likely to be due to vigorous development of phase transformations and intensification of diffusion-controlled processes, including the effects of the evolution of the dislocation structure, growth of subgrains, and formation of new grains in the bulk of the pre-existing ones during plastic deformation. [ABSTRACT FROM AUTHOR]

Previous studies have found that both high temperature and low temperature increase the risk of childhood hand, foot and mouth disease (HFMD). However, little is known about whether temperature variation between neighboring days has any effects on childhood HFMD. A Poisson generalized linear regression model, combined with a distributed lag non-linear model, was applied to examine the relationship between temperature change and childhood HFMD in Hefei, China, from 1st January 2010 to 31st December 2012. Temperature change was defined as the difference of current day's mean temperature and previous day's mean temperature. Late spring and early summer (April-July) were chosen as the main study period due to it having the highest childhood HFMD incidence. There was a statistical association between temperature change between neighboring days and childhood HFMD. The effects of temperature change on childhood HFMD increased below a temperature change of 0 °C (temperature drop). The temperature change has the greatest adverse effect on childhood HFMD at 7 days lag, with 4 % (95 % confidence interval 2-7 %) increase per 3 °C drop of temperature. Male children and urban children appeared to be more vulnerable to the effects of temperature change. Temperature change between adjacent days might be an alternative temperature indictor for exploring the temperature-HFMD relationship. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate a temperature regime ranged from 15 to 30°C on survival, growth, life span and reproductive traits (reproductive period, clutch number, offspring number) of Phallocryptus spinosa from Iran. Newly hatched nauplii (N= 200 and 3 replicates per each treatment) were allocated into containers and maintained at various temperature regimes (at 15, 20, 25 and 30˚C). During trial, the larvae were fed with unicellular algae Dunaliella tertiolecta and Lansy PZ (lipid-enriched yeast). Survival and growth rate of P. spinosa with an interval of 3 days to 18 days were examined. After attaining adulthood, 16 pairs of adult P. spinosa were transferred from all culture vessels into separate containers supplied with 300 ml of brackish water (5 ppt) and similar temperatures to compare their life span and reproductive traits. Based on results obtained, maximum growth at shortest period (13.2±2.0 mm on day 12) was observed at 30°C; whereas, all P. spinosa died before reaching sexual maturity by day 15. Maximum survival (86%) was observed at 15°C; however, minimum growth also was obtained at the same temperature with none of P. spinosa reaching sexual adulthood. On the 18th day, P. spinosa reached sexual adulthood only at 20 and 25°C. Furthermore, a significant difference was observed in most of the reproductive traits especially in total egg production per female at 20°C. Thus, it seems that 20°C is the suitable temperature to rear this fairy shrimp. Future studies should be focused on the feasibility of mass production of this species as a valuable live feed in the aquaculture industry. [ABSTRACT FROM AUTHOR]

CO 2 bubble nucleation on the microrough poly(ε-caprolactone) surface has been investigated using a density functional theory approach. For the considered system, the effect of chemical and morphologic characteristics of poly(ε-caprolactone) on the solubility, surface tension, interfacial density distribution, nucleation free-energy barrier, and critical nucleus radius have been calculated to interpret the nucleation mechanism. All calculations are performed with the universal force field parameters. Some results have been examined by the available experimental data. According to the free-energy barrier and critical radius, the nucleation number with respect to pressure has been estimated under the instant depressurization. As a result, this work provides a theoretical explanation of bubble formation mechanism of polymer foaming at low temperature. [ABSTRACT FROM AUTHOR]

In this paper, we present the application of neuro-fuzzy system-ANFIS for air conditioning systems to reduce electricity consumption. The current buildings have automation systems that provide data on lighting, electrical system, air conditioning system, etc. We studied the air conditioning system, in particular, to reduce energy consumption as air conditioning has a high consumption value. Our main goal in this study is the application of neuro-fuzzy system-ANFIS with the adjustment of the rules made by a decision tree-CART algorithm in air conditioning system. We compared the results of the application of the ANFIS-CART system with the application of PID controllers and fuzzy control system for a central air conditioning. [ABSTRACT FROM AUTHOR]

Abstract: This work is aimed to investigate the regulation problem for thermal comfortableness and propose control strategies for cabin environment of EVs (electric vehicles) by constructing a reduced-scale A/C (air-conditioning) system which mainly consists of two modules: ECB (environmental control box) and AHU (air-handling unit). Temperature and humidity in the ECB can be regulated by AHU via cooling, heating, mixing air streams and adjusting speed of fans. To synthesize the near-optimal controllers, the mathematical model for the system thermodynamics is developed by employing the equivalent lumped heat capacity approach, energy/mass conservation principle and the heat transfer theories. In addition, from the clustering pattern of system eigenvalues, the thermodynamics of the interested system can evidently be characterized by two-time-scale property. That is, the studied system can be decoupled into two subsystems, slow mode and fast mode, by singular perturbation technique. As to the optimal control strategies for EVs, by taking thermal comfortableness, humidity and energy consumption all into account, a series of optimal controllers is synthesized on the base of the order-reduced thermodynamic model. The feedback control loop for the experimental test rig is examined and realized by the aid of the control system development kit dSPACE DS1104 and the commercial software MATLAB/Simulink. To sum up, the intensive computer simulations and experimental results verify that the performance of the near-optimal order-reduced control law is almost as superior as that of standard LQR (Linear-Quadratic Regulator). [Copyright &y& Elsevier]

Abstract: This paper presents an online fault-tolerant control strategy. By correcting the faulty measurements with a final correcting factor, the strategy covers five steps: fault detection, construction of correcting alternatives, performance forecasting, alternatives outranking, and fault correction. System energy, indoor air quality, human thermal comfort, and control efficiency are considered as a whole to evaluate the operating performance. Taking the supply air temperature sensor faults as testing examples, the strategy is tested in a virtual air conditioning system and simulated on TRNSYS platform. The testing results show that a large fault correcting factor is obtained in the first hour, an adjusting phase presents in the next several hours, and the correction factor keeps unchanged finally. High level of calculating accuracy is required for the performance prediction model. Also, for the outranking evaluation model, the thresholds and weight coefficients should be assigned appropriately to meet the requirements of building functions and/or owners. [Copyright &y& Elsevier]

Abstract: Generic simulation models noted as AGM-I and AGM-II for performance and control analysis of variable refrigerant flow (VRF) systems were developed. Firstly, simulation models from component to whole VRF system were addressed. Then the simulation models were validated using experimental data reported in an open literature. The average error percentages to predict system cooling capacity, energy consumption and COP are 4.69%, 4.64%, 1.19%, respectively. Finally, tests were carried out. Results show that the developed models are fast computing and evaporator-number independent. From the computation speed point of view, the AGM-I is more suitable for multi-evaporator VRF system, while the AGM-II is more suitable for the one evaporator VRF system. Test results also show the system models good ability responding to varying conditions, including inlet air temperature of the evaporator, outdoor air temperature, opening of the EEVs and compressor speed, which are all very important variables for the control analysis. [Copyright &y& Elsevier]

Presented in this article is an evaluation of impacts for the multifamily Power Partner (PP) program. This demand response (DR) program is designed to reduce electrical system peak during periods of high grid demand through air conditioner curtailment in apartments. The multifamily sector is evaluated using both logger and automatic meter read (AMR) data. Impacts from the two methods indicate that the multifamily population trends to higher second hour impacts over the first hour of demand response in contrast to single-family and small commercial customers covered in previous internal Austin Energy (AE) studies. Estimated program curtailment values range from 3 MW to 4.5 MW below the current program estimate of 81 MW for the entire single-family and multifamily DR population. Control group method of impact evaluation is recommended as it is noted that extreme days, when curtailments are initiated, may have a different load profile than more moderate hot days used for baseline statistical analysis. Migration from one-way radio controlled thermostats to two-way communicating equipment is also recommended. Equations for estimating program impacts for the multifamily program as a function of temperature and hour of impact are presented. [ABSTRACT FROM PUBLISHER]

Control of air-conditioner units is essential to achieve satisfactory comfort conditions in buildings while keeping low energy consumption and operation costs. In this paper, a nonlinear multiinput & multioutput model (MIMO) of an air-handling unit (AHU) is considered. After linearization of the state equations around the operating points, an observer and a regulator are designed for the estimation of state variables and disturbance rejection, respectively. A realistic uncertain model is considered which constitutes various uncertainties associated with complex nonlinear model of AHU. In the presence of model uncertainties, a H ∞-robust controller is designed to guarantee robust performance of the air-handling unit. In addition, a simple controller based on pole-placement approach is developed. Indoor temperature and relative humidity are controlled via manipulation of valve positions of air and cold water flow rates. Achievement of tracking objectives is investigated through various desired commands of indoor temperature and relative humidity (including a sequence of steps and ramps-steps). According to results, the H ∞-robust controller guarantees the robust performance of the AHU in tracking of desired set-paths (while using the simple pole-placement controller leads to high oscillatory behavior of the output variables and control efforts). Moreover, using H ∞-robust controller results in less energy consumption in comparison with the pole-placement controller. [Copyright &y& Elsevier]

Abstract: An artificial neural network (ANN)-based dynamic model for an experimental variable speed direct expansion (DX) air conditioning (A/C) system has been developed, linking the indoor air temperature and humidity controlled by the DX A/C system with the variations of compressor and supply fan speeds. The values of average relative error (ARE) and maximum relative error (MRE) when validating the ANN-based dynamic model developed under three different input patterns were 0.33%, 0.27%, 0.27% and 0.89%, 0.99%, 1.15%, respectively, indicating the high accuracy of the ANN-based dynamic model developed. An ANN-based controller was then developed for controlling the indoor air temperature and humidity simultaneously by varying the compressor speed and supply fan speed in a space served by the experimental DX A/C system. The controllability tests including command following test and disturbance rejection test were carried out using the experimental DX A/C system, and the test results showed that the ANN-based controller developed was able to track the changes in setpoints and to resist the disturbances. [Copyright &y& Elsevier]

The integration of three-dimensional spatial distributions into building simulations is of significant interest, and computational fluid dynamics (CFD) analysis is widely employed in building design processes. For example, based on the experience of architects and engineers, CFD analyses are often conducted under steady boundary conditions to determine the degree of attainment of indoor environments. However, CFD analyses have large calculation costs and cannot be often used for simulations with unsteady boundary conditions such as energy simulations in the building design processes. Thus, we developed a method that calculates sensitivities from heat sources to an arbitrary point in an indoor environment and integrates them into simulations with unsteady boundary conditions. In the proposed method, CFD analysis is employed under steady boundary conditions to calculate the response factors, and the resulting sensitivities are integrated into simulations under unsteady boundary conditions. In the present study, the proposed method was applied to optimize the variables of an air conditioning control system. With our method, temperature changes at a sensor over time are calculated from the time series of air supply temperature. In total, 800 calculations were conducted, and the optimal variables that allow the temperature at the sensor to reach the target value quickly were obtained. Except for the time required to calculate the response factors, the optimization in the present study took only a few seconds. If only CFD analysis was used for the optimization, the calculations would take a year. Thus, calculating the sensitivities via CFD analysis and utilizing the results in simulations is a useful approach for solving optimization problems. Moreover, the proposed method is applicable to simulations that require three-dimensional spatial distributions to enhance the accuracy of the calculation such as energy simulations. [ABSTRACT FROM AUTHOR]

Abstract: It is necessary to adopt appropriate control strategies to save energy and improve the indoor air quality (IAQ). On the validated TRNSYS simulation platform, four different control strategies are investigated to examine the indoor air temperature, energy consumption, CO2 concentration and predicted mean vote (PMV) for the variable air volume (VAV) systems in an office building in Shanghai. As an original scheme, Strategy A using constant outdoor air intake fraction shows high energy consumption, low CO2 concentration and acceptable thermal comfort. By using minimum outdoor air ventilation based on dynamic occupancy detection, Strategy B can provide more than 15% energy saving, acceptable PMV value but high CO2 concentration in breathing zone. By using indoor air temperature reset, Strategy C presents the most energy savings beyond 20% reduction, low CO2 concentration but poor thermal comfort. In mild seasons, combining enthalpy-based outdoor airflow economizer cycle with supply air temperature reset, Strategy D can achieve 9.4% energy savings and the lowest CO2 concentration. Taken together, each strategy covers some strengths as well as some weaknesses. How to comprehensively assess a control strategy for all specific objectives should be considered in future studies. [ABSTRACT FROM AUTHOR]

Abstract: This paper tackles an experimental investigation of a new solar desalination prototype using the humidification dehumidification principle at the weather conditions of Sfax City, Tunisia. The prototype is designed and constructed at the national engineering school of Sfax to conduct this experimental investigation under different meteorological and operating parameters. It is composed of a flat plate solar air collector, a flat plate solar water collector, a humidifier, an evaporation tower and a condensation tower. An economic analysis was conducted, since it affects the final cost of produced water, to determine both the cost of fresh water production and the payback period of the experimental setup. Although a system may be technically very efficient, it may not be economic. The experimental investigation of the dynamic behaviour of the solar desalination unit during summer season (June, July and August) and during a typical day in July was carried to study the temporal evolutions of the temperature of air and water and the relative humidity at the inlet and the outlet of each component of the system. [Copyright &y& Elsevier]

Abstract: It requires more energy to maintain a narrow indoor temperature range than a broader range, in which the building may be allowed to float with reduced conditioning for longer periods of time. A narrow range should presumably be preferable to the building occupants to justify its increased energy cost. At what widths are temperature ranges detected, preferred, or judged unacceptable? Three databases of occupant satisfaction in buildings are used to examine the acceptability of three classes of temperature range currently employed in the ISO and European standards, and proposed for the ASHRAE standard. These are alternatively identified as class A, B, and C, or category I, II, and III, but their specifications are identical. The A class (I category) is found to confer no relative satisfaction benefit to individuals or to realistic building occupancies. In addition, the differences in B and C class satisfaction are small. [Copyright &y& Elsevier]

Abstract: In this paper, a control framework for the air-conditioning system operated in heating mode is proposed. The control framework possesses a cascade structure for dealing with the fast and slow dynamics respectively contributed by the vapor compression cycle and the indoor dynamics. Under the control framework, the control performances associated with two strategies, the condenser superheat regulation (CSR) strategy and the evaporator superheat regulation (ESR) strategy are examined. It is shown experimentally that while ESR strategy demonstrates more superior transient response, CSR strategy is more advantageous in reducing the compressor power at steady state. In order to achieve both transient performance and steady-state power savings, the two strategies are combined in the way that ESR strategy is responsible for the control action during the startup/transient phase of operation, CSR strategy takes over the control when steady state is reached, and a bumpless compensator is used to smooth the control action during control switching. Experiments demonstrate that the combined strategy can simultaneously enhance transient performance and steady-state efficiency. [Copyright &y& Elsevier]

Abstract: This paper presents a robust model predictive control strategy for improving the supply air temperature control of air-handling units by dealing with the associated uncertainties and constraints directly. This strategy uses a first-order plus time-delay model with uncertain time-delay and system gain to describe air-conditioning process of an air-handling unit usually operating at various weather conditions. The uncertainties of the time-delay and system gain, which imply the nonlinearities and the variable dynamic characteristics, are formulated using an uncertainty polytope. Based on this uncertainty formulation, an offline LMI-based robust model predictive control algorithm is employed to design a robust controller for air-handling units which can guarantee a good robustness subject to uncertainties and constraints. The proposed robust strategy is evaluated in a dynamic simulation environment of a variable air volume air-conditioning system in various operation conditions by comparing with a conventional PI control strategy. The robustness analysis of both strategies under different weather conditions is also presented. [Copyright &y& Elsevier]

Abstract: Frost build-up blocks the gap between fins and decreases the airflow rate, and the heating capacity and COP of air-source heat pump become lower. The reverse-cycle defrosting (RCD) and hot-gas bypass defrosting HGBD are the two common methods of frost removal. The comparison between the RCD and HGBD methods on one heat pump were not found by authors up to now. This paper compared the dynamic characteristics during the RCD and HGBD periods on one medium air-to-water heat pump of 55kW. The feasibility of the HGBD method without heat provided to evaporate the liquid refrigerant after melting frost, which was supposed in the danger of the compressor liquid slugging, was especially discussed. The results showed the liquid refrigerant leaving the air cooled coils for the HGBD method was trapped in the suction accumulator and flashed into the saturated gas by the compressor pumping action, and no compressor liquid slugging happened in our tests. The HGBD time was much longer than the RCD time. The amenity for the HGBD method was better than that for the RCD method, due to lower refrigerant noise, smaller indoor temperature fluctuation, and no cold blowing. The suction superheat and discharge superheat for the HGBD method were lower than those for the RCD method. The HGBD could overcome the main disadvantages of the RCD method and deserved the further investigation. [Copyright &y& Elsevier]

In this study, a controlled fuzzy expert system (FES) was designed to provide the conditions necessary for operating rooms. For this purpose, existing operating rooms have been studied to see if there are more useful, reliable and comfortable ones. How an operating room can be controlled with FES and its advantages and disadvantages have also been researched. For a theoretically visible FES to show system’s advantage a prototype operating room was built and a suitable configuration was designed. In this system, heat, humidity, oxygen and particles were used as input parameters, and a fresh air entrance and fan circulation were chosen as output parameters. With the help of an expert, appropriate linguistic expressions and the membership function of these expressions were defined. The sensors were classified and sensor information was transferred to computer by means of an interface designed. In order to transfer the data to the system simultaneously, an interface was written in C#. Whether it provides the most suitable control for the system prototype was determined by simulating the operation with varying numbers of patients and operation personnel. In these trials, input, output and other necessary parameters were collected in the computer. In the study, we obtained excellent results in prototype operating room control with FES. The analyses of the results carried out indicated that the controls performed with FES provide more economical, comfortable, reliable and consistent controls and that they are feasible in a real operating room. [Copyright &y& Elsevier]

Abstract-A novel real-time optimization approach for two-way direct load control (TWDLC) of central air-conditioning chillers is proposed. For TWDLC, the main computer in the control center constantly monitors the average controllable load of every customer. For real-time calculations, a computationally fast and effective approach based on linear programming is proposed to determine the shedding ratio of every customer. The proposed optimization approach will minimize the difference between the load required to shed and the load actually shed at each sampling interval. Every customer's contribution to the load shedding is also leveled by the proposed approach. A gateway is installed at every customer's site to coordinate shedding control with the main computer through the Internet. As soon as the gateway receives the expected shedding ratio, it calculates the load required to shed and coordinates all chiller units in operation to conduct load shedding, thereby achieving the load reduction amount. [ABSTRACT FROM AUTHOR]

Abstract: This paper examines optimal control strategies of variable air volume air conditioning system. The control strategies included a base control strategy of fixed temperature set point and two advanced strategies for insuring comfort and indoor air quality (IAQ). The first advanced control adjusts the fresh air supply rate and the supply air temperature to maintain the temperature set point in each zone while assuring indoor air quality. The second strategy controls the fresh air rate and the supply air temperature to maintain an acceptable thermal comfort and IAQ in each zone. The optimization problem for each control strategy is formulated based on the cost of energy consumption and constrained by system and thermal space transient models. The optimization problem is solved using genetic algorithm. The optimization scheme/model is applied to a case study for a building floor in Beirut weather. The thermal space and system component models were validated for the base strategy using Visual DOE 4.0 software [Architectural Energy Cooperation, San Francisco, USA; 2005 〈www.archenergy.com〉]. Energy savings up to 30.4% were achieved during the summer season of four months with the optimized advanced strategies when compared with the conventional base strategy while comfort and IAQ were satisfied. [Copyright &y& Elsevier]

Abstract: In this study, the potential saving of cooling energy by elevated air speed which can offset the impact of increased room air temperature on occupants’ comfort, as recommended in the present standards (ASHRAE 55 2004, ISO 7730 2005 and EN 15251 2007), was quantified by means of simulations with EnergyPlus software. Fifty-four cases covering six cities (Helsinki, Berlin, Bordeaux, Rome, Jerusalem and Athens), three indoor environment categories I, II and III (according to standard EN 15251 2007) and three air velocities (<0.2, 0.5 and 0.8m/s) were simulated. The required cooling/heating energy was calculated assuming a perfectly efficient HVAC system. A cooling energy saving between 17 and 48% and a reduction of the maximum cooling power in the range 10–28% has been obtained. The results reveal that the required power input of the fan is a critical factor for achieving energy saving at elevated room temperature. Under the assumptions of this study, the energy saving may not be achieved with the methods for air speed increase, such as ceiling, standing, tower and desk fans widely used today when the power consumption of the fan is higher than 20W. [Copyright &y& Elsevier]

Abstract: This study has focused on the evaluation of the optimal temperature in each cabin of the Korean maritime patrol vessels. We aptly modified the inland indoor items and criteria of clothing and activities, and then investigated the human factors in the cabins of Korean maritime patrol vessels. The total thermal resistance of clothing in the wheelhouse was 0.097, 0.079, 0.096, and 0.130m2 °C/W and that for the accommodation areas was 0.067, 0.059, 0.084, and 0.101m2 °C/W in spring, summer, fall, and winter, respectively. The metabolic rate was 228.04W/m2 in the training room and above 100W/m2 in the engine room and auxiliary machine room. In the wheelhouse and accommodation, the metabolic rate was 78.14 and 44.45W/m2, respectively. Based on human factors, the optimum temperature was 23°C in the wheelhouse and 29°C in the accommodation. Therefore, 6°C of energy can be saved in case of PMV/PPD-based air conditioning. [Copyright &y& Elsevier]

A building management system (BMS) established to control the system of building services would not incorporate records of occupants' views nor integrate real-time occupants' response for any system fine tuning to satisfy individual demands in a dynamic manner. This study proposes a humanized adaptive baseline information technology (HABIT) algorithm to enable such fine tuning according to the occupants' feedback to optimize the acceptance of the indoor environment. Apart from solving the complaints from occupants, the proposed algorithm also integrates the collective real-time feedback from endusers with a balance of the imposed design conditions to determine the optimum operation condition of the system. In the study, the temperature set point of an air-conditioning system in certain Hong Kong offices was used as an illustrative example to demonstrate the operation of the algorithm. Survey results on occupants' views and indoor environmental conditions of the offices were used to determine the input parameters of the algorithm. With the proposed algorithm, HABIT could be used for updating the design set point of the existing BMS. Practical application: This study provides a new notion of humanized adaptive baseline information technology (HABIT) for air-conditioned spaces of a single temperature set point. The occupants' views and indoor environmental conditions of the offices are used as input parameters of the algorithm in determining the optimum temperature set point for maximizing the occupants' satisfaction. The algorithm could be built into existing building management systems (BMS) for determining the air temperature set point of a centralized air conditioning system. [ABSTRACT FROM AUTHOR]