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The building sector is one of the largest final consumers of energy, especially for air conditioning, and research has shown that there is a great potential for energy savings in this sector. The performance of a chiller can vary significantly depending on system partial loads and evaporator and condenser operating temperatures. The condensers of water-only chillers take the heat of condensation from the refrigerant only through the sensible heat of the refrigerant, leading to significant water flows. The outside air temperature and the intensity of solar radiation directly influence the consumption of electricity on the chiller. Having available the values for the solar radiation intensity I [W/m2 ] and the outside air temperature te [⁰C], with the help of the proposed mathematical model, validated by experimental measurements, the optimal values for the minimum electricity consumption of the system are obtained, under the conditions which the chilled water temperature is 7/12⁰C and the indoor air temperature is 27⁰C [ABSTRACT FROM AUTHOR]

Various advanced control sequences for chiller plants with water-side economizers (WSE) have been proposed in literature, but the evaluation and optimization of those controls is limited. It is possible to maximize energy savings by selecting different sequences and related parameters based on the plant configuration, load, and climate. This paper addresses this gap by developing near-optimal advanced control sequences for chiller plants with WSEs. First, advanced control sequences for chiller plants with WSEs are categorized into condenser water, chilled water, and hybrid controls and representative sequences from each category are identified. Next, 504 different scenarios are optimized. These scenarios represent all possible combinations of two plant configurations, a constant or variable load profile, three advanced control sequences, and seven optimization parameter combinations in six climate zones. The results show the recommended near-optimal sequences can reduce energy consumption by up to 15% relative to the baseline depending on the configuration, load profile, and climate. Specifically, the CW-CHW sequence is recommended for the majority of systems because it is often the most energy efficient and/or reduces the runtime of chillers. The methodology in this paper provides practical guidance for achieving energy savings through near-optimal control of chiller plants with WSEs. [ABSTRACT FROM AUTHOR]

For investigating the effect of the quality composition of CH refrigerant R1270/R600 (0.6:0.4) and (0.7:0.3) on the performance of a dual temperature chiller, the experiment measured at constant in and out temperatures of the refrigeration water. The results indicate that under the condensation and evaporation temperature remain constant, when the quality fraction of low boiling R1270 raises, the maximum total COP of the refrigeration system increases from 3.36 to 7.36, while the maximum COP at low temperatures does not change much, and the maximum COP at high temperatures increases from 2.02 to 5.95. The percentage of 1 evaporator capacity to total refrigeration capacity has decreased from the maximum value of 44.54% to 20.91%. The percentage of 2 evaporator capacity to total refrigeration capacity has increased from the maximum value of 68.52% to 83.19%. The compression ratio decreases. When the operating conditions changed, the maximum COP of the two components occurs at the temperatures of 1 chilled water are the highest and the temperatures of 2 chilled water are the lowest. The maximum consumption of the system compressor power is 0.99KW, and the maximum discharge temperature is 75.81℃. The finding can provide guideline for the application of the units as a substitute for refrigerants. [ABSTRACT FROM AUTHOR]

While forced-air convective systems remain the predominant method for heating and cooling worldwide, radiant cooling and heating systems are emerging as a more efficient alternative. Current radiant cooling systems primarily rely on hydronic chilled water systems. This study introduces direct-expansion radiant cooling as a novel technique that could enhance the efficiency of radiant cooling and reduce its environmental impact. Water (R-718) has been tested as a refrigerant due to its favorable thermodynamic properties and environmental advantages; however, to the author's knowledge, it has yet to be tested in direct-expansion radiant cooling. This research investigated several refrigerants, including water (R-718), ammonia (R-717), R-410a, R-32, R-134a, and R-1234yf, for this application. The findings indicate that water demonstrates efficiency comparable to other non-natural refrigerants, making it a promising candidate, given its favorable thermodynamic properties and substantial environmental benefits. Despite challenges such as a high compression ratio necessitating multi-stage compression, a high compressor discharge temperature exceeding 300 °C and requiring specialized blade materials, and a high suction volume flow rate, direct-expansion radiant cooling operates within a different temperature range. Consequently, the compressor discharge temperature can be reduced to 176 °C, and the compression ratio can be lowered to approximately 3.5, making water a more viable refrigerant option for this application. [ABSTRACT FROM AUTHOR]

In India, air conditioning is essential in the truck driver's cabin during the summer. An air conditioning system powered by the vehicle's engine adds to the engine's workload, resulting in higher fuel demand and more emissions. An adsorption chiller that runs on engine exhaust is designed here to lower the interior temperature of a truck cabin to address the above-mentioned issue. Here, an adsorption air conditioner system's effectiveness is forecast using a lumped analytical technique. During the adsorption process, heat from the adsorber bed is absorbed by cold water and released into the radiator. The desorber bed has been heated using hot water as a heat transfer medium from the engine exhaust heat. The analysis was carried out using the adsorption kinetic equation at adsorption equilibrium. The influence of inlet water flow rate, temperature and switching time (adsorber process to desorber process and vice versa) on adsorption chiller performance has been studied here. According to simulation results, the proposed adsorption chiller can be used to keep the driver cabin cool during summer for operational conditions adopted during the simulation. The adsorption air conditioner's highest coefficient of performance (COP), as determined by this investigation, was found to be 0.214. [ABSTRACT FROM AUTHOR]

Because of the higher efficiencies achieved by polygeneration systems compared with conventional generation systems, they have been increasingly adopted to reduce the consumption of resources and consequent environmental damage. Heat dissipated by equipment can be harnessed and reused in a cascade manner. This study applies the Theory of Exergetic Cost (TEC), a thermoeconomic approach, to a high-performance polygeneration system. The system includes a biogas-fueled internal combustion engine, a water–ammonia absorption refrigeration system driven by the engine's exhaust gases, and a set of photovoltaic panels with a cooling system coupled to solar panels and a hot water storage tank. The pieces of equipment are dimensioned and selected according to the energy demands of a hotel. Then, the temperature, pressure, and energy flows are established for each point of the system. Mass, energy, and exergy balances are developed to determine exergy flows and efficiencies. The main component in terms of exergy and operation costs is the engine, which consumes 0.0613 kg/s of biogas, produces 376.80 kW of electricity, and provides thermal energy for the refrigeration system (101.57 kW) and the hot water tank (232.55 kW), considering the average operating regime throughout the day. The levelized costs are 2.69 USD/h for electricity, 1.70 USD/h for hot water (thermal energy tank), and 1.73 USD/h for chilled water (absorption chiller). The thermoeconomic diagnosis indicated that the hot water tank and the engine are the most sensitive to changes in the maintenance factor. Reducing operating expenses by 20% for the tank and engine lowers energy costs by 10.75% for the tank and 9.81% for the engine. [ABSTRACT FROM AUTHOR]

This study experimentally analysed the influence of chilled water temperature setpoints on thermal comfort conditions and energy consumption of an office building. Three chilled water temperature setpoints (10 °C, 12.5 °C, and 14 °C) were studied. The indoor environment variables (temperature and relative humidity) which are considered indicators of thermal comfort were recorded with data loggers for three consecutive days for each chilled water temperature setpoint (CWTS). Similarly, energy consumption was used as a metric to determine the system's efficiency. The predicted percentage of dissatisfied (PPD) and predicted mean vote (PMV) indicators were computed and analysed using the Thermal Comfort/ASHRAE 55-2020 modelling tool from the centre for the built environment (CBE). Additionally, computational fluid dynamics (CFD) modelling and analysis were performed using ANSYS Fluent to study the indoor environment conditions of the office at the different chilled water temperature setpoints. A comparison between the calculated, measured, and predicted satisfaction of occupants was done. The results obtained when varying the chilled water temperature setpoints reveal that increasing the chilled water temperature setpoint (by 12%) reduces energy consumption per hour by 2% without compromising thermal comfort. The study demonstrated that the CWTS could be reset between 14 and 15 °C to reduce energy consumption and maintain thermal comfort. Moreover, the CFD model can be used to compare the indoor environmental characteristics of chiller systems. [ABSTRACT FROM AUTHOR]

Due to the hot climate, energy consumption for refrigeration is significantly higher in the subtropical monsoon climate region. Combined with renewable energy and ice-storage technology, a model predictive control model of the regional cooling system was proposed, which was conducive to improving the flexibility of the regional cooling system and the ability of peak shifting and valley filling. In this model, an artificial bee colony (ABC) optimized back propagation (BP) neural network was used to predict the cooling load of the regional cooling system, and the model parameter identification method was adopted, combining utilizing a river-water-source heat pump and ice-storage technology. The results showed that the load prediction algorithm of the ABC-BP neural network had a high accuracy, and the variance coefficient of load prediction root-mean-square error (RMSE) was 16.67%, which was lower than BP, support vector regression (SVR), and long short-term memory (LSTM). In addition, compared with the three control strategies of chiller priority, ice-storage priority, and fixed proportion, the operation strategy optimized by the comprehensive model can reduce the average daily cost by 19.20%, 4.45%, and 5.10%, respectively, and the maximum daily energy consumption by 30.02%, 18.08%, and 8.90%, respectively. [ABSTRACT FROM AUTHOR]

There has been a growing recognition in recent years that Electrofuels (e-fuels), also known as renewable and sustainable fuels, which are produced from hydrogen and carbon dioxide as the primary feedstocks, have great potential to reduce carbon footprint and address climate change. In the present study, contrary to most previous studies in which the sources of feedstock's preparation were considered as block boxes, two stand-alone processes are taken into account and incorporated into the e-fuels production system. H 2 is obtained by a high-temperature electrolysis system having an overall efficiency nearly twice that of a low-temperature electrolysis system. CO 2 is captured from a power plant flue gas stream with a purity of 99.81%. Investigating heat integration potential in such an integrated plant is an up-to-date and interesting topic and has not yet been well explored. Therefore, a heat integration within the three individual processes is implemented to reduce energy consumption. The design of the process-to-process heat transfer section is carried out using pinch design rules. By integrating individual units, approximately 42% of the required cold utility, traditionally supplied by chilled water and refrigerants, is allocated to generate high and medium-pressure steams. Having used the high-temperature steam electrolysis for H 2 production, a process that requires less external electricity compared to low-temperature water electrolysis, a power-to-liquid efficiency of 70% is achieved. Furthermore, the results reveal a carbon conversion ratio of 98.6%, indicating the effective converting the carbon from the feedstock into liquid hydrocarbons. [Display omitted] • Heat integration between e-fuels unit and its feedstocks supplier units is done. • Shell-and-tube and plate-fin exchangers are used to design heat exchanger network. • Required cold utilities in the processes decreases by 42% by steam generation. • Power-to-liquid efficiency is improved by 70% through the integration. • Effective converting carbon from the feedstock into liquid hydrocarbons by 98.62%. [ABSTRACT FROM AUTHOR]

BACKGROUND: Vacuum packaging has the ability to reduce oxidative deterioration and microbial‐induced spoilage of meat. However, in an oxygen‐free environment, it can lead to the development of an unappealing purplish‐red color and a decrease in the water‐holding capacity of meat, thereby impacting the overall meat quality. Portulaca oleracea L. (POL) is a homology of medicine and food known for its exceptional antioxidant and antimicrobial properties. RESULTS: The aim of our present study was to investigate the antioxidant and antimicrobial ability of n‐butanol phase extract of POL and the effect of POL extract incorporation on the quality (water‐holding capacity, shear force, color, and texture) and physicochemical (pH, total volatile base nitrogen, and total viable counts) attributes of vacuum‐packed seasoned steaks at 4 °C over a 15‐day period. Results showed that the POL extract had excellent antioxidant and antimicrobial capacity. Furthermore, the addition of POL extract significantly inhibited protein oxidation and microbial growth of steaks (P < 0.05), and improved the water‐holding capacity, color properties, and tenderness (P < 0.05). Moreover, there were no significant differences (P > 0.05) in the color, water‐holding capacity, or tenderness between the 0.5 and 1 g kg−1 POL extract treatment groups compared to the sodium nitrite control group. CONCLUSION: These results indicate that POL extract had the potential to replace sodium nitrite due to its ability to hinder protein oxidation and microbial growth of vacuum‐packed seasoned steaks, while enhancing the color, water‐holding capacity, and tenderness of seasoned steaks. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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Urban water systems are potential sources of secondary microplastics (MPs) as well as a distributor of MPs in the environment. In the present study, the presence of MPs in the urban water systems of the Tehran Metropolitan (Capital of Iran) was investigated. In addition, the probable relationship of MPs with different land uses (i.e., residential-commercial, forest, military, and highway) was assessed. The results showed that all parts of Tehran's urban water system in the study area were contaminated with MPs (107.1 ± 39, 37.8 ± 10.5, 48.3 ± 3.1, 46.9 ± 5.6, 59.4 ± 26.5, 1.7, 2.0 ± 0.6, 7.9 ± 1, 1.8 ± 0.2 particles/liter at the residential, integrated, military, forest, highway runoffs, drinking water, groundwater, seasonal river, and the effluent of the wastewater treatment plants; respectively). However, significant differences were found between different land uses. As expected, the residential runoff had the highest rate of MPs pollution, with 107.1 ± 39 particles/liter. According to the obtained results and our estimation, more than five million MPs/day can enter into the water bodies and soil of the study area through the wastewater treatment plants. While there are significant differences in MPs in the different land uses, our findings suggest that residential areas and highways need further attention in controlling the spread of MPs in urban areas. [ABSTRACT FROM AUTHOR]

Inter‐annual precipitation in California is highly variable, and future projections indicate an increase in the intensity and frequency of hydroclimatic "whiplash." Understanding the implications of these shocks on California's water system and its degree of resiliency is critical from a planning perspective. Therefore, we quantify the resilience of reservoir services provided by water and hydropower systems in four basins in the western Sierra Nevada. Using downscaled runoff from 10 climate model outputs, we generated 200 synthetic hydrologic whiplash sequences of alternating dry and wet years to represent a wide range of extremes and transitional conditions used as inputs to a water system simulation model. Sequences were derived from upper (wet) and lower (dry) quintiles of future streamflow projections (2030–2060). Results show that carryover storage was negatively affected in all basins, particularly in those with lower storage capacity. All basins experienced negative impacts on hydropower generation, with losses ranging from 5% to nearly 90%. Reservoir sizes and inflexible operating rules are a particular challenge for flood control, as in extremely wet years spillage averaged nearly the annual basins' total discharge. The reliability of environmental flows and agricultural deliveries varied depending on the basin, intensity, and duration of whiplash sequences. Overall, wet years temporarily rebound negative drought effects, and greater storage capacity results in higher reliability and resiliency, and lesser volatility in services. We highlight potential policy changes to improve flexibility, increase resilience, and better equip managers to face challenges posed by whiplash while meeting human and environmental needs. Plain Language Summary: Inter‐annual precipitation is naturally highly variable in California, and future projections indicate an increase in the intensity and frequency of hydroclimatic "whiplash." This study investigates the potential impacts of these hydroclimatic events to comprehend their implications on California's water system and its level of resilience, which holds critical importance from a planning perspective. We focus on four basins in the western Sierra Nevada, to quantify the resilience of reservoir services provided by the water and hydropower systems in the region. Using downscaled runoff data from 10 climate models, we generated 200 synthetic hydrologic whiplash sequences to represent combinations of extreme wet and dry conditions. Results show that all basins experienced negative effects on carryover storage, with losses ranging from 5% to nearly 90%, consequently decreasing hydropower generation. Flood control is challenged during extremely wet years due to reservoir sizes and operating rules. The reliability of environmental flows and agricultural deliveries varied across basins and whiplash sequences. Wet years tend to mitigate negative drought effects temporarily, and greater storage capacity improved the reliability and resilience of services. We highlight the need for potential policy changes to enhance flexibility and resilience, and equip managers to face challenges posed by whiplash. Key Points: Wet years can temporarily rebound negative drought effects, although challenging flood control due to reservoir sizes and operating rules.Environmental flows and agricultural deliveries oscillated depending on the basin, intensity, and duration of whiplash sequences.Greater storage capacity generally provided greater reliability and resiliency, and lesser volatility in water and power services. [ABSTRACT FROM AUTHOR]

The energy reduction in chillers has been considered an important factor in the energy efficiency improvements of cooling systems, and water-side free cooling is regarded as the key of chiller free cooling technology. Therefore, this research aims to develop a control methodology for the extension of the free cooling operation time in order to improve the efficiency of water cooling-type chillers based on a WSE (water-side economizer) system for a data center and review the proper control conditions through an energy usage analysis of the entire system. The suggested methodology is an increase in the chilled water supply and return temperature according to the increase in the CARH (Computer Room Air Handler) fan air flow and a decrease in the chilled water flow. A case study was conducted according to the application of control through an EnergyPlus simulation. The results of the simulation show that energy usage was reduced by 8.1% under 120% CRAH fan capacity and 100% chilled water flow conditions. When applying the control plan, the free cooling period was extended according to the increased CRAH fan capacity and decreased chilled water flow. However, the increase in the CRAH fan energy must be considered. Also, in the case of a reduction in the chilled water flow, it is necessary to consider a point that can guarantee the cooling treatment heat rate in the heat exchanger. [ABSTRACT FROM AUTHOR]

• Improving the seasonal performance by increasing heat exchanger size. • R32 drop-in impacts various compressor modulation strategies in distinctive ways. • Oversizing heat exchangers has larger benefits with lower range modulation strategy. • Oversizing BPHX can yield higher performance than improving the compressor motor efficiency. • Variable speed compressor at part load conditions could experience refrigerant maldistribution. The decrease in fossil fuel reserves and high energy consumption by HVAC&R equipment require the use of compressors with better efficiencies and capacity modulation strategies. Usually, seasonal performance studies focus on compressor capacity modulation methods, however the current study explores the idea of improving the seasonal performance of two compressor modulation techniques: a two-stage and a variable speed compressor with different capacity modulation ranges by using larger condensers in an R410A water ethylene glycol chiller system. The analysis shows that oversizing the heat exchangers has larger benefits with the compressor modulation strategy with lower range. Additionally, the seasonal performance estimated according to AHRI 551/591 (2020) of a two-stage compressor with oversized condenser is higher than a basic single speed compressor with a better motor indicating that oversizing brazed plate heat exchanger (BPHX) might yield higher performance than improving the compressor motor efficiency. Due to the high global warming potential (GWP) of R410A, there is a focus on replacing it with low GWP refrigerants such as R32 to reduce CO 2 emissions. This study would also compare the performance when using R32 as a drop-in refrigerant in the two different R410A compressor capacity modulation strategies with comparable cooling capacity. When the refrigerant was changed from R410A to R32, the integrated part load value (I P L V. S I), an efficiency metric for variable speed compressor remains relatively constant at 5.5 while it increases from 3.9 to 4.4 for the two-stage compressor. It is hypothesized that low refrigerant mass flow rate (m ˙ r e f) provided by the variable speed compressor when matching the load at the lower part load conditions leads to refrigerant maldistribution in BPHX and reduced I P L V. S I. [ABSTRACT FROM AUTHOR]

A calcium phosphate solid formed as an unintended consequence of a novel high-pH orthophosphate lead corrosion control strategy in Providence, RI, resulting in some consumer complaints and clogged plumbing. Investigations were carried out at pH levels of 8.9–10.4, at temperatures of 5–60°C, and with orthophosphate concentrations ranging from 0 to 4.0 mg/L as orthophosphate (PO4) to examine this phenomenon. During field testing, the calcium phosphate initially precipitated at orthophosphate doses above about 2 mg/L as PO4, and the extent of precipitation increased with water age and higher temperature. Laboratory-scale tests confirmed that doses above about 2 mg/L as PO4 were required to form the precipitate in the absence of preexisting calcium phosphate solids and that the solid formed quickly at 60°C (upper range for hot water heaters) and tended to dissolve at lower pH. Solubility studies and solids characterization indicate that the particles are a mixture of noncrystalline compounds containing calcium and phosphate. For water systems currently practicing a high pH/low alkalinity corrosion control strategy, orthophosphate dosing can enhance plumbosolvency control without the risk of pH reduction, but formation of this solid can place an upper limit on the maximum orthophosphate residual level in the distribution system. [ABSTRACT FROM AUTHOR]

The paper researches water quality, supply and management system assessment problems of the Montenegrin costal region. A significant problem is generated by seasonal tourism, the main branch of Montenegrin costal economy. The selected performance indicators model has been tested in the water supply system of the city Herceg Novi, as a representative experimental system for the Montenegrin costal area. The city Herceg Novi has 33.000 permanent residents and around 80.000 individual consumers during the summer touristic season. The research activities are based on the seasonal parameters defined by the monitored performance indicators of the water supply system. The study depicts the developed indicators performance model based on the obtained experimental monitoring data. Within the experimental analytical research performance an indicator matrix was established. The coastal area of Montenegro is experiencing over 50 % of water loss. Structure developed in the model applies the performance indicators and results in systematic losses reduction. The model takes into account the principle of seasonality, and the existence of two completely different periods of the year. This type of the experimental research with testing in situ was for the first time performed and implemented in the costal Adriatic region of Montenegro. [ABSTRACT FROM AUTHOR]

Background Holding times for raw materials are relevant since they enable us to understand the allowable time that a raw material can be kept under ideal storage conditions before the start of the manufacturing process without its quality attributes being affected. The quantification of water activity can be used as an indicator of the microbiological, physicochemical, and organoleptic stability of a specimen, since low water activity retards autohydrolysis and microbiological growth. Objective The main purpose of this investigation was to test the stability of powdered raw materials for a maximum holding time of 8 days through water activity measurements. Thus microbiological, physicochemical, and organoleptic measurements were carried out in parallel and simultaneously to experimentally establish a relationship between the status of the water activity of processed raw materials and the microbiological, physicochemical, and organoleptic results. Methods The raw materials were stored for a maximum holding time of 8 days, in accordance with United States Pharmacopeia monographs. For all the raw materials tested, water activity measurements were performed using the dew point chilled-mirror method on days 0, 3, and 8. On days 0 and 8, microbiological, physicochemical, and organoleptic assessments were performed. Results It was established that under these storage conditions, the processed raw materials exhibited water activity below 0.60 during the entire holding time. However, there were statistically significant differences in water activity levels between days 0, 3, and 8 (ANOVA P  < 0.05). Despite observing statistically significant differences between days, the microbiological, physicochemical, and organoleptic features were within specification at those water activity levels below 0.60. Conclusions Water activity below 0.60 does not allow the growth of microorganisms, and the organoleptic and physicochemical features remain unperturbed. The results indicate that water activity can be used as an indicator of the microbiological load and chemical stability of the raw materials tested. Highlights This research provides evidence that corroborates that water activity status may be used as a reliable indicator for the microbiological burden and physicochemical features of pharmaceutical material during stability studies. [ABSTRACT FROM AUTHOR]

Cities around the world are facing increased sensitivity to drought effects. Climate-change-induced drought affects not only the natural hydrology of the broad macroclimate but also those in the urban microclimates. The increasing frequency and duration of droughts are creating challenges for urban water utilities to convey water through distribution systems to customers reliably and consistently. This has led many urban areas like San Francisco, California, to search for unique alternative water supply projects to help bolster the drought resilience of the coupled human and natural water system. This paper focuses on applying the features of resilience (i.e., plan, adapt, absorb, and recover) through a drought resilience matrix to water supply alternatives to analyze how the addition of these projects would increase the overall water system's drought resilience. San Francisco, California, was used as the case study to test the use of this matrix. Three portfolios (modifying existing supply, recycling, and desalination, as well as local approaches) were created and tested in the matrix. Each portfolio is composed of various alternative water supply projects that the San Francisco Public Utilities Commission (SFPUC) is considering for implementation. Results concluded that the local approaches portfolio provided the most drought resilience, with the recycling and desalination portfolio providing the least resilience. The study approach and the presented findings will provide guidance to water utility professionals in supply planning to enhance drought resilience. [ABSTRACT FROM AUTHOR]

The complexity of irrigation systems and the need to adapt them to uncertainties requires developing approaches to synthesize their performances. This paper reviews performance assessment and indicators for agricultural water systems. It is aimed at finding various methods and indices used for irrigation performance assessment and standard classes for their characterization. The global application of the metrics was also documented. Adopting a systematic review approach, peer‐reviewed journal articles published in the English language in the last two decades (1 March 2001 to 31 December 2020) were surveyed. Case studies were presented demonstrating the application of the indicators. The study revealed a lack of standardization and the use of a wide range of indicators among others, and recommended representing certain indicators as single. However, this review considered one indicator as the best. Suggestions for further studies were made. Highlights: A systematic review of methods and indices for agricultural performance assessments was conducted.Performance indicators are applied globally in small and large agricultural systems under different spatial and temporal scales, scales of analysis, and management types.Some categories of PIs need further studies to come up with a single PI that will represent them. [ABSTRACT FROM AUTHOR]

A variable pressure differential fuzzy control method is proposed based on the online identification method for key parameters and the fuzzy subset inference fuzzy control method of the chilled water system network model. Firstly, a phase plane fuzzy identification method is proposed for the most unfavorable thermal loop. The study focuses on analyzing the trend of room temperature deviation and deviation change in different quadrants in the phase plane. Furthermore, we establish a chilled water pipe network model that recalculates flow variation in both the main pipe and each branch pipe section to eliminate the most unfavorable thermal loop. Finally, the test platform for the fan coil variable flow air conditioning water system was designed and constructed to meet the requirements of energy-saving regulation. Additionally, the network monitoring system for the test platform was completed. The calibration and debugging results demonstrate that the monitoring error is within ±5.0%, ensuring precise control of room temperature at the end of the branch within ±0.5 °C. Results demonstrate that our novel method exhibits superior stability in room temperature control compared to traditional linear variable pressure differential set point controls while achieving energy saving ranging from 4.7% to 6.5%. [ABSTRACT FROM AUTHOR]

Introduction: This work systematically investigates the effect of chloride level, temperature, and the water system's oxidative power on the pitting corrosion performance of stainless steels in pH-neutral environments. Methods: Two test programs were set to a) develop a robust method for constructing the pitting engineering diagrams and b) construct the pitting engineering diagrams based on the obtained method from the first test program. The various electrochemical techniques were selected to assess and understand factors that affect the corrosion behavior of stainless steel. Extensive testing was performed with short-term electrochemical measurements and long-term immersion tests. Results and Discussion: The obtained results demonstrate that the electrochemical methods are sufficient to define pitting diagrams showing the boundaries between pitting and no pitting as a function of chloride concentration, temperature, and the water system's oxidation potential. The laboratory long-term electrochemical test results correspond the best to real applications and clearly underline the importance of an induction time for pit initiation. Accordingly, two sets of pitting engineering diagrams were constructed based on the water system's oxidation potential. Measurements at the applied potential of 150 mV vs. saturated calomel electrode (SCE) correspond to applications in sterile tap water, whereas the applied potential of 400 mV vs. SCE corresponds to slightly chlorinated water or water with some biological activity. Pitting engineering diagrams were proved to be very useful tools to aid material selection in water application. However, it is important to realize that additional factors, such as different surface conditions and the presence of other environmental species, crevice design, or weld will affect the exact position of the boundaries between pitting and no pitting. [ABSTRACT FROM AUTHOR]

Drinking water is vital for human health and life, but detecting multiple contaminants in it is challenging. Traditional testing methods are both time-consuming and labor-intensive, lacking the ability to capture abrupt changes in water quality over brief intervals. This paper proposes a direct analysis and rapid detection method of three indicators of arsenic, cadmium, and selenium in complex drinking water systems by combining a novel long-path spectral imager with machine learning models. Our technique can obtain multiple parameters in about 1 s. The experiment involved setting up samples from various drinking water backgrounds and mixed groups, totaling 9360 injections. A raw visible light source ranging from 380 to 780 nm was utilized, uniformly dispersing light into the sample cell through a filter. The residual beam was captured by a high-definition camera, forming a distinctive spectrum. Three deep learning models—ResNet-50, SqueezeNet V1.1, and GoogLeNet Inception V1—were employed. Datasets were divided into training, validation, and test sets in a 6:2:2 ratio, and prediction performance across different datasets was assessed using the coefficient of determination and root mean square error. The experimental results show that a well-trained machine learning model can extract a lot of feature image information and quickly predict multi-dimensional drinking water indicators with almost no preprocessing. The model's prediction performance is stable under different background drinking water systems. The method is accurate, efficient, and real-time and can be widely used in actual water supply systems. This study can improve the efficiency of water quality monitoring and treatment in water supply systems, and the method's potential for environmental monitoring, food safety, industrial testing, and other fields can be further explored in the future. [ABSTRACT FROM AUTHOR]

In this paper, a solar absorption cooling system with a chilled water storage tank and peak load compression system was considered for cooling the Instituto Superior Tecnico Tower building in Lisbon, Portugal. To fulfill this task, a dynamic simulation of the building was performed using the DesignBuilder software, then a solar collector field was designed. The next step was to build a computational model of the absorption chiller in the Engineering Equation Solver software, which allowed for further simulation of the annual operation of the system supported by the chilled water tank and the backup system with compressed air conditioning. The last stage of the work was the economic analysis of such a system in comparison with conventional compressed air conditioning. The simulation results and economic analysis showed that the solar absorption cooling system could be a beneficial cooling solution for the Instituto Superior Tecnico Tower building. However, it would have to operate with an energy storage system and a peak load compression backup system to be able to cool the building efficiently all year round. Additionally, such a solution could have a significant positive impact on climate through considerable annual savings in electricity consumption. Results revealed that the proposed system meets the cooling demand of the building, mainly by solar-energy-driven absorption chiller. The annual contribution of a backup compression chiller ranges from 20% to 36% depending on the size of chilled water storage tanks. Financial calculations revealed discounted payback periods in the range of 4.5 to 12.5 years depending on the system configuration. [ABSTRACT FROM AUTHOR]

• Accurate semi-empirical model for variable speed multi-chiller systems. • Determination of the optimum number of operating chiller units, and their compressor speed. • Energy efficiency as a function of compressor speed and cooling water temperature. • Comparison of energy savings for different operation strategies. Environmental protection drives the replacement of environmentally harmful refrigerants with potentially flammable alternatives, necessitating efficient cooling strategies for varying loads. Legislation limits flammable refrigerant charge, leading to the adoption of multi-chiller systems with smaller charges and therefore also smaller loads per chiller. However, operating such systems requires complex strategies, addressable through fast and reliable models. This study presents a semi-empirical model predicting the behaviour of variable-speed multi-chiller systems. The model focuses on predicting cooling capacity and coefficient of performance (COP) for cooling, with input parameters of evaporation and condensation temperatures, and compressor speed. Experimental validation of the parameterized model shows COP predictions within 3 % for a two-module system using R-290 (propane) under different conditions and compressor speeds. The model assesses various operation strategies, including the conventional mode with fewer chiller modules running at high speed, compared to modes where all chillers run but at reduced speeds. Comparing COP values in these modes reveals energy-saving potentials of up to 14.57 % for constant condensation temperatures. Moreover, strategies involving condensation temperature reduction, or a combination with compressor speed reduction are analysed for energy-saving potentials. Reducing the condensation temperature by 3 K results in savings of up to 13.25 % and combined with the compressor speed reduction savings of up to 23.54 % are feasible. These findings emphasize the importance of considering compressor speed when operating multi-chiller systems to maximize energy savings. The presented model effectively evaluates various strategies and implements variable-load control in multi-chiller systems, serving as a valuable tool for optimising energy efficiency and promoting environmentally friendly cooling practices. [ABSTRACT FROM AUTHOR]

Altered precipitation and temperature patterns from a changing climate will affect supply, demand, and overall municipal water system operations throughout the arid western U.S. While supply forecasts leverage hydrological models to connect climate influences with surface water availability, demand forecasts typically estimate water use independent of climate and other externalities. Stemming from an increased focus on seasonal water demand management, we use the Salt Lake City, Utah municipal water system as a test bed to assess model accuracy versus complexity trade‐offs between simple climate‐independent econometric‐based models and complex climate‐sensitive data‐driven models to average to extreme wet and dry climate conditions—representative of a new climate normal. The climate‐independent model displayed low performance during extreme dry conditions with predictions exceeding 90% and 40% of the observed monthly and seasonal volumetric demands, respectively, which we attribute to insufficient model complexity. The climate‐sensitive models displayed greater accuracy in all conditions, with an ordinary least squares model demonstrating a measurable reduction in prediction bias (3.4% vs. −27.3%) and RMSE (74.0 lpcd vs. 294 lpcd) compared to the climate‐independent model. The climate‐sensitive workflow increased model accuracy and characterized climate‐demand interactions, demonstrating a novel tool to enhance water system management. [ABSTRACT FROM AUTHOR]

Thermal power generation is economical in the current scenario, but it is a water-intensive process, resulting in a high-water footprint. In this research, life cycle water use (LCWU) was assessed for three coal-based thermal power plant in India. The LCWU was found to be in the range of 2.5 to 3.5 L-kWh−1. The results of the LCWU of coal-based thermal power plants in India are higher than the global average of 1.75 L-kWh−1. In order to reduce the dependency on water, air-cooled condenser (ACC) with a novel approach of reducing temperature of air before entering into condenser is purposed using vapour absorption chillers. A 300 MW thermal power plant located in the South India region is chosen to illustrate the application of the proposed system. Initially, waste heat from flue gas is used to run a vapour absorption chiller, and finally a solar-assisted vapour compression chiller is used. Also, in order to utilize large coastal lines in India, an alternate approach of sea water cooling-based thermal power generation is investigated. A 2 MW steam turbine plant utilizing deep sea water is designed and analysed. In seawater cooling system the condenser temperature is reduced, increasing efficiency by 1.9% and power output by 133 kW. It resulted in power generation with multiple benefits, including cooling, desalinated water, and increased plant efficiency. The outcomes of this study provide information on water use in Indian thermal power plants along with its comparative assessment. A study of ACCs and seawater-cooled condensers is also an opportunity to reduce the life-cycle water use in thermal power plants in India. [ABSTRACT FROM AUTHOR]

Uncertainty arising from climate change poses a central challenge to the long‐term performance of many engineered water systems. Water supply infrastructure projects can leverage different types of flexibility, in planning, design, or operations, to adapt infrastructure systems in response to climate change over time. Both flexible planning and design enable future capacity expansion if‐and‐when needed, with flexible design proactively incorporating physical design changes that enable retrofits. All three forms of flexibility have not previously been analyzed together to explicitly assess their relative value in mitigating cost and water supply reliability risk. In this paper, we propose a new framework to evaluate combinations of flexible planning, design, and operations. We develop a nested stochastic dynamic optimization approach that jointly optimizes dam development and operating policies under dynamic climate uncertainty. We demonstrate this approach on a reservoir project near Mombasa, Kenya. Our results find that flexible operations have the greatest potential to reduce costs. Flexible design and flexible planning can amplify the value of flexible operations under higher discounting scenarios and when initial infrastructure capacities are undersized. This approach provides insight on the climate change and techno‐economic conditions under which flexible planning, design, and operations can be best leveraged individually or in combination to reduce climate change uncertainty risks in water supply infrastructure projects. Key Points: We develop a framework to compare the value of combinations of flexibility in water supply infrastructure planning, design, and operationsFlexible operations are more effective than flexible planning or design in addressing climate uncertainty in water‐limited environmentsFlexible planning and design are more useful when initial reservoir capacity is low, discounting is high, or the cost of shortages is high [ABSTRACT FROM AUTHOR]

Water system management models represent different purposes, such as water supply, flood control, recreation, and hydropower. When building large-scale system models to represent these diverse objectives, their most appropriate time steps for each purpose often do not coincide. A monthly time step is usually sufficient for water supply modeling, but it can be too coarse for flood control, hydropower, and energy operations, where hourly time steps are preferred. Large-scale water management and planning models mostly employ monthly time steps, but using monthly average energy prices underestimates hydropower revenue and overestimates pumping energy cost because these plants tend to operate during times with above- or below-average energy prices within any month. The approach developed here uses hourly varying prices depending on the percent of monthly operating hours. This paper examines an approach that approximately incorporates hourly energy price variations for hydropower and pumping into large-scale monthly time-step water system model operations without affecting water delivery results. Results from including hourly varying energy prices in a large-scale monthly water supply model of California (CALVIN) are presented. CALVIN is a hydroeconomic linear programming optimization model that allocates water to agricultural and urban users with an objective to minimize total scarcity costs, operating costs, and hydropower revenue loss. Thirteen hydropower plants are modeled with hourly varying prices, and their revenue increased by 25 to 58% compared to revenue calculated with monthly average constant energy prices. Hydropower revenue improvements are greater in critically dry years. For pumping plants modeled with hourly varying prices, the energy use cost decreased by 10 to 59%. This study improves system representation and results for large-scale modeling. [ABSTRACT FROM AUTHOR]

Eutrophication and hypoxia represent an ever-growing stressor to estuaries and coastal ecosystems due to population growth and climate change. Understanding water quality dynamics in shallow water systems is particularly challenging due to the complex physical and biogeochemical dynamics and interactions among them. Within shallow waters, benthic microalgae can significantly contribute to autotrophic primary production, generate organic matter, increase dissolved oxygen consumption, and alter nutrient fluxes at the sediment-water interface, yet they have received little attention in modeling applications. A state-of-the-art modeling system, the Semi-Implicit Cross-Scale Hydroscience Integrated System Model (SCHISM), coupled with the Integrated Compartment Model (ICM) of water quality and benthic microalgae, has been implemented in the Corsica River estuary, a tributary to Chesapeake Bay, to study benthic microalgal impact on water quality in shallow water systems. The model simulation has revealed a broad impact of benthic microalgae, ranging from sediment-water interface fluxes to water column dynamics, and the effects are observed from near-field to far-field monitoring stations. High-frequency variability and non-linearity dominate benthic microalgal dynamics, sediment oxygen demand, and nutrient fluxes at the sediment-water interface. Resource competition and supply determine the spatial scope of benthic microalgal impacts on far-field stations and the whole estuary system. Our study shows that benthic microalgae are a significant factor in shallow water dynamics that needs adequate attention in future observation and modeling applications. [ABSTRACT FROM AUTHOR]

Supply chilled water temperature (SCWT) is an important variable for the efficient and stable operation of heating, ventilation, and air conditioning (HVAC) systems. A precisely measured value ensured by the continuous reliability of the temperature sensor is essential for optimal control of an HVAC system because temperature sensor faults can affect the chiller operation and waste energy. Therefore, temperature sensor fault-detection strategies are imperative for maintaining a comfortable indoor thermal environment and ensuring the efficient and stable operation of HVAC systems. This study proposes a fault-detection method for an SCWT sensor using a virtual sensor based on a long short-term memory-autoencoder. The fault-detection performance is evaluated considering a case study under various sensor fault scenarios to evaluate changes in indoor thermal comfort and energy consumption after correcting sensor faults detected by the virtual sensor. The results verify excellent fault-detection performance in various fault scenarios (F-1 scores ranging from 0.9350 to 1.000). After correcting the SCWT fault, indoor thermal comfort is steadily maintained without additional energy consumption (indoor set-point temperature unmet hour reduced by a maximum of 105.7 hours, and energy consumption decreased by up to 1.8%). [ABSTRACT FROM AUTHOR]

This paper summarizes the results of a Special Issue focusing on the practical applications of model predictive control and other advanced control methods in the built environment. This Special Issue contains eleven publications and deals with various topics such as the virtual sensing of indoor air pollutants and prediction models for indoor air temperature and building heating and cooling loads, as well as local and supervisory control strategies. The last three publications tackle the predictive maintenance of chilled water systems. Most of these publications are field demonstrations of advanced control solutions or promising methodologies to facilitate the adoption of such control strategies, and they deal with existing buildings. The Special Issue also contains two review papers that provide a comprehensive overview of practical challenges, opportunities, and solutions to improve building operations. This article concludes with a discussion of the perspectives of advanced controls in the built environment and the increasing importance of data-driven solutions. [ABSTRACT FROM AUTHOR]

Designing urban water systems to respond to the accelerating and unpredictable changes of the Anthropocene will require changes not only to built infrastructure and operating rules, but also to the governance arrangements responsible for investing in them. Yet, inclusion of this political‐economic feedback in dynamic models of infrastructure systems and socio‐hydrology has lagged behind operational feedback concerns. We address this gap through a dynamical systems application of the Coupled Infrastructure Systems (CIS) Framework, which provides the conceptual building blocks for analyzing social‐ecological systems through various classes of infrastructure and the flows of material and information among them. In the model, political‐economic feedback involves three decisions—infrastructure investment, rate‐setting, and short‐term demand curtailment—and each decision is constrained by institutional friction, the aggregation of decision and transaction costs associated with taking action. We apply the model to three cities in the Phoenix Metropolitan Area to compare how institutional friction interacts with a city's water resource portfolio and financial position to determine its sensitivity, or the degree to which its performance (e.g., providing sufficient supply to meet demand) changes given reductions in Colorado River water availability. We find that the slowing effect of institutional friction on investment and rate‐setting decisions can increase the sensitivity of a city's supply, but it can also promote objectives that compete with over‐response (e.g., rate burden). The effect is dependent on the initial operating capacity of the CIS and flexibility within the institutions, highlighting the need to consider political‐economic and operational feedback together when evaluating infrastructure systems. Plain Language Summary: Urban water systems must grapple with accelerating social and environmental change that requires them to not only consider future infrastructure needs, but also, the configuration of decisions responsible for infrastructure investment. Unfortunately, inclusion of political‐economic feedback has lagged behind operational feedback in models that examine water systems response to changing environments. We present a modeling approach to trace the flow of water, information, and investment in a general urban water system that must make three annual decisions: infrastructure investment, rate‐setting, and short‐term demand curtailment. Each decision is influenced by costs to taking action and the flexibility involved in setting action magnitudes. We apply the model to three cities in the Phoenix Metropolitan Area to compare how these institutional constraints interact with existing infrastructure and finances to affect their sensitivity, or the degree to which their performance (e.g., providing sufficient supply to meet demand) changes given reductions in Colorado River water. We find that when institutional barriers to action increase, cities are more sensitive to supply shocks, but such barriers can benefit other objectives like rate burden. The effect is dependent on the presence of redundant supplies, demand growth, and decision‐making flexibility, highlighting the need to consider both political‐economic and operational concerns when evaluating water systems. Key Points: Having sufficient supply redundancy can outweigh the negative effect of slow institutions on a city's ability to address supply shocksThe supplies of cities with institutions that require more stress to act are more sensitive to shocks, but their rates are less sensitiveAdding flexibility to institutions can ease the burden of large investments on ratepayers and improve the reliability of slow institutions [ABSTRACT FROM AUTHOR]

Adsorption technologies offer a promising solution for managing high electricity demand in building by leveraging waste heat recovery and renewable energy sources. The prismatic adsorbent bed adsorption water cooling system investigates energy and exergy analyses for cooling application. With hot water temperature of 80 °C, cooling water inlet temperature 30 °C, and chilled water inlet temperature 14 °C, the system achieves an energy efficiency of 45.2% while demonstrating an energy storage density of ≈340 kJ kg−1. As a result, the exergy efficiency reaches 12.2%, and the mass fraction at the end of the adsorption process is a significant value of 0.13kgadsorbate/kgadsorbent. Increasing the water mass flow rate in the evaporator results in a decrease in exergy efficiency, while simultaneously causing an increase in energy efficiency. With an increase in the chilled water inlet temperature of the evaporator and the hot water inlet temperature of the adsorbent bed, there is an increase in the energy storage density, energy efficiency, and exergy destruction due to irreversibility and losses. According to this study, the impact of the chilled water inlet temperature on the energy and exergy performances of the evaporator is more significant compared to the effect of the water mass flow rate. [ABSTRACT FROM AUTHOR]

Water can be redistributed physically and virtually. We explored water allocation optimization to mitigate water stresses by constructing a physical–virtual dual water system and optimizing the 1987 Yellow River water allocation scheme. We calculated the virtual water volume, identified the virtual in-basin, out-of-basin, and export water volumes, and compared the total regional water demand (i.e., combined physical and virtual water volumes) with regional water planetary boundaries to optimize basin water allocation schemes. Virtual water accounted for > 90% of the total regional demands, whereas physical flows did not significantly impact them. Moreover, allocation quotas for Qinghai and Inner Mongolia should be reduced by 0.113 and 1.005 billion m3, respectively, for sustainability. Furthermore, improving the efficiency of water-intensive sectors and limiting virtual water outflows from heavy industry to out-of-basin sectors are vital to water intensification. Increased attention should be directed toward physical–virtual water demands than the current focus on supply-oriented water allocation. [ABSTRACT FROM AUTHOR]

Calcium carbonate deposits from ancient water systems such as aqueducts are a hidden archive for archaeology and environmental sciences. These deposits formed wherever carbonate‐rich water was in contact with a water‐containing structure and recorded water composition, temperature, biological content, the operation or nonoperation of a water system segment, flow discharge and velocity, the shape of disappeared segments of water structures, the number of years a water supply system was active, disruptions of the water supply and water management such as repairs, adaptations and cleaning. Indirectly, urban development, resilience, population‐ and socioeconomic dynamics can be studied through the stratigraphy of carbonate in water systems. Carbonate archives can also give insight into long‐term changes in paleoclimate and on environmental pollution, deforestation, extreme floods, droughts, earthquakes and volcanic eruptions. Archaeological and environmental investigations of carbonate deposits can provide data with up to daily resolution over decades to centuries. Although absolute dating of carbonate from water systems is still problematic, each study on the aqueduct of an ancient city, together with its carbonate deposits, provides its own microstory in Roman life. [ABSTRACT FROM AUTHOR]

Background Phigenics Validation Test (PVT) VIABLE® (Viability Identification Assay by Legionella Enrichment) is a method to detect viable Legionella bacteria in building water systems. Objective To evaluate PVT VIABLE against the ISO 11731:2017 Water Quality—Enumeration of Legionella reference method for the detection of viable Legionella species in potable and non-potable water. Methods PVT VIABLE was tested for inclusivity (n  = 50 strains of Legionella) and exclusivity (n  = 30 non-target strains), robustness, and stability. A multi-laboratory instrument variation study was performed to evaluate the PCR data. The matrix study was performed on potable and non-potable water samples inoculated with Legionella pneumophila at a low (n  = 20) and high fractional level (n  = 5). Samples were analyzed using the PVT VIABLE and confirmed using ISO 11731:2017. Results Statistical analysis showed no difference between PVT VIABLE and ISO 11731:2017 for 100 mL test portions of potable and non-potable water. PVT VIABLE demonstrated high levels of specificity and sensitivity in the inclusivity and exclusivity study. Results of the robustness and stability studies demonstrated the method was sufficiently robust to handle small method changes and met the method claims of stability. Conclusion PVT VIABLE allows the end user to obtain presumptive results for viable Legionella spp. contamination of potable and non-potable water in 2–3 days. Highlights PVT VIABLE provides viable Legionella results in 2–3 days versus 10–14 days for traditional spread plating. This novel diagnostic tool also differentiates between Legionella pneumophila sg1, Legionella pneumophila sg2–15, and Legionella spp. without the need for additional confirmation steps as outlined in ISO 11731:2017. [ABSTRACT FROM AUTHOR]