Search

With the increase in energy demand and carbon emission requirements, energy management and CO2 emission reduction on the user side are significant for integrated energy system (IES) scheduling. This paper constructs a two-stage optimal dispatching model combining active/passive demand response (DR) and reward and punishment ladder-type carbon trading. In the first stage, the electricity/gas load was optimized by adding a logistics function to the active DR model. A passive DR model is built based on the optimized electric load and the heat/cooling–electricity ratio of the cogeneration unit to optimize the heat/cooling load. In the second stage, a multi-objective IES model based on the optimized load and reward and punishment ladder carbon trading was solved by the golden eagle multi-objective optimization (MOGEO). Analyzing the scheduling results from different scenarios, the active/passive DR model can reduce the load peak-to-valley difference and improve user satisfaction and grid revenue. At the same time, the combination of reward and punishment ladder carbon trading makes the system gain more carbon revenue, reduces system operating costs and carbon emissions, and improves energy utilization. [ABSTRACT FROM AUTHOR]

This paper studies the combined heating and cooling thermal performance of a CO2 heat pump system considering the subcooling effect. For such a system without cold thermal energy storage (CTES), the gas cooler outlet temperature normally needs to be controlled to match the cooling load required. However, the integration of CTES would enable the system to be operated under its optimal conditions depending on the ambient temperatures, i.e. a considerable amount of cooling capacity can be generated and stored for later use. A configuration of a CO2 heat pump integrated with CTES is described in this paper. A thermodynamic cycle and a simulation model considering the subcooling effect have been developed. The mathematical model for the pinch point analysis has been newly validated against published experimental data with acceptable agreements. In the case study, the impacts of the subcooling temperature on the optimal combined performance under four ambient temperatures (5 °C, 15 °C, 25 °C, and 32 °C) have been studied. The highest optimal combined COP of 5.38 can be achieved when the ambient temperature is 5 °C. The detailed profiles of CO2 temperatures, heating and cooling loads, and the COPs when the CTES is in operation have been revealed for the first time. It is found when the ambient temperature is higher than the water inlet temperature (plus the pinch point temperature), the optimal cooling COPs can even have a surge without the subcooling effect, due to a lower sCO2 temperature leaving the heat exchanger compared to the ambient temperature. Additionally, performance analysis for the CO2 heat pump system with or without CTES is compared, and it is concluded that all optimal heating, cooling, and combined COPs integrated with CTES surpass those without CTES. [ABSTRACT FROM AUTHOR]

Shallow geothermal heat has the characteristics of wide distribution and huge reserves. However, for northern rural buildings, the heating load in winter is much greater than the cooling load in summer, and thermal imbalance of the soil is prone to occur. This paper takes rural residences in southern Hebei as an example and designs a solar-assisted shallow geothermal energy system. Compared with the original shallow ground-source heat pump system, the indoor and outdoor temperature differences of the target building were first analyzed. Second, the changes in the soil temperature field and the differences in the supply and return water temperature were monitored. Finally, the initial investment and operating costs of the assisted system are analyzed. The results show that the average ground temperature field increases significantly in winter. Through the alternate operation of solar energy and ground-source heat pumps, heat extraction from the ground is reduced, and the imbalance cycle of heat extraction in winter and heat removal in summer is shortened. It alleviates the imbalance of the cold and heat loads for soil throughout the year. The inlet and outlet water temperature and heat exchange efficiency of the buried pipes have been significantly improved. The energy efficiency ratio of the system using the assisted system has increased from 3.40 in 2020 to 4.17, an increase of 0.77. The optimal ratio of the solar- assisted shallow geothermal energy system is a 12.80 m2 solar heat-collection area and one buried hole. The winter heating operating cost of the solar-assisted shallow geothermal energy system is 18.86 CNY/m2. It can save 37% of the annual operating costs of heating, cooling, and hot water compared to a single ground-source heat pump system and 40%–45% compared to traditional heating and cooling modes. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of using a phase change material (PCM)-based latent heat storage (LHS) integrated with an air-conditioning system. The study has filled the knowledge gap regarding the dependence of melting rate and operational time of the AC system on PCM volume. Additionally, the study has examined the influences of important parameters such as inlet velocity and Stefan number on melting rates, outlet temperature, and COP. The results have revealed that higher inlet air velocity and Stefan number have led to shorter melting duration. Specifically, an increase in velocity from 1.6 to 2.14 m/sec has reduced the time required for complete melting by 19.16% at a fixed Ste value and D value of 2. Further increasing the velocity to 2.67 m/sec has reduced the time by 31.59%. However, increasing the volume of the PCM has resulted in a longer melting duration, with the total melting time increasing from 3.35 to 7.11 h. Better COP values have been obtained for low-velocity cases. For all cases examined, the COP of the AC system with PCM has been superior to the COP without the PCM at any given time. Increasing inlet velocity and Ste raised the outlet temperature of the HEX, while PCM volume had little impact. The results have also indicated that lower inlet velocity is suitable for longer working periods and lower AC cooling loads, whereas higher inlet velocity is appropriate for shorter working periods and higher AC cooling loads. [ABSTRACT FROM AUTHOR]

The novelty of this work is a new type of stack, namely, the parallel wave stack (PWS). In this paper, we study the performance of an air-based standing wave thermoacoustic refrigerator using the PWS. We use small heat pipes with a heat transfer rate of approximately 30 W as heat exchangers for the system. We investigate the effect of the ratio of stack length (Ls) to the distance between stack center and reflector (Xs) on the performance of the refrigerator parallel wave stacks with a blockage ratio (BR) of 67 %, 71 %, and 74 %, and with Ls/Xs ratios of 0.74, 0.96, and 1.20. We tested and compared these under a cooling load (Qc) of 0.5 W to 2 W and a frequency of 150 Hz. The results show that a BR of 71% with an Ls/Xs ratio of 0.96 provides a minimum cold-side temperature (Tc), and a maximum temperature difference (ΔTm), a maximum coefficient of performance, and a maximum relative coefficient of performance. This new type of stack can provide a higher performance. The structure of the stack is also stronger than others. This stack is an alternative and can be used in a thermoacoustic refrigerator. The results obtained from the present study will be very useful for improving the performance of the thermoacoustic refrigerator in the future. [ABSTRACT FROM AUTHOR]

The rapid increase in cooling demand for air-conditioning worldwide brings the need for more efficient cooling solutions based on renewable energy. Seawater air-conditioning (SWAC) can provide base-load cooling services in coastal areas utilizing deep cold seawater. This technology is suggested for inter-tropical regions where demand for cooling is high throughout the year, and it has been implemented in islands with short distances from the coast and the deep sea. This paper proposes adjustments to the conventional design of SWAC plants to reduce implementation risks and costs. The approach is named high velocity SWAC and consists of increasing the excavation depth of the seawater pump station up to 20 m below the sea level, compared to 2 to 5 m in conventional SWAC projects. This allows a twofold increase in the speed of inlet pipeline seawater and cooling load of the plant. The cooling load can be expanded twofold with only 55% capital cost and 83% project costs, compared with the costs of a new system. In addition, this article shows that high velocity SWAC plants with thermal energy storage will have an important role supporting the dissemination of intermittent renewable sources of energy in regions where SWAC is a viable cooling alternative. [ABSTRACT FROM AUTHOR]

This paper presents experimental and thermodynamic investigations of the performance of commercial refrigeration systems with capacities varying from 6 to 26 tons of refrigeration. The analysis considers a critical comparison between the conventional and widely used single-phase approach with the actual multi-phase methodology. The tests were performed under practical conditions with state-of-the-art experimental setups using variable cooling loads. The tests were performed in a climate chamber with advanced ambient temperature and humidity control equipment, where temperature can be raised up to 65 °C, and humidity can vary from 10 to 90%. This enabled us to simulate a wide range of operating modes to validate the performances of the proposed two-phase refrigeration system with theoretical results obtained from single-phase modeling. It was also found that the refrigeration system with a larger cooling capacity exhibited an operational performance close to two-phase theoretical results more than the small refrigeration system capacity. The experimental results were found to comply with the theoretical results with an error of approximately 10% for the two-phase approach compared to an error of approximately 20% for the single-phase approach. [ABSTRACT FROM AUTHOR]

Energy being a precious resource needs to be mindfully utilized, so that efficiency is achieved and its wastage is curbed. Globally, multi-storeyed buildings are the biggest energy consumers. A large portion of energy within a building is consumed to maintain the desired temperature for the comfort of occupants. For this purpose, heating load and cooling load requirements of the building need to be met. These requirements should be minimized to reduce energy consumption and optimize energy usage. Some characteristics of buildings greatly affect the heating load and cooling load requirements. This paper presented a systematic approach for analysing various factors of a building playing a vital role in energy consumption, followed by the algorithmic approaches of traditional machine learning and modern ensemble learning for energy consumption prediction in residential buildings. The results revealed that ensemble techniques outperform machine learning techniques with an appreciable margin. The accuracy of predicting heating load and cooling load, respectively, with multiple linear regression was 88.59% and 85.26%, with support vector regression was 82.38% and 89.32%, with K-nearest neighbours was 91.91% and 94.47%. The accuracy achieved with ensemble techniques was comparatively better—99.74% and 94.79% with random forests, 99.73% and 96.22% with gradient boosting machines, 99.75% and 95.94% with extreme gradient boosting. [ABSTRACT FROM AUTHOR]

Transformer insulation aging is a critical issue for both reliable and economic operations, and for planning of electrical systems. As insulation aging depends on the hottest-spot temperature, transformer management can be improved with a suitable model for temperature estimation and prediction. However, the temperature inside transformers varies dynamically because of changes in both the cooling conditions and the load cycles. Hence, this paper presents an algorithm to estimate and predict the hottest-spot in dry-type distribution transformers, so that their capability and insulation life can be assessed. This procedure is focused on transformers used to directly connect PV-inverters to the grid in order to consider the uncontrolled power generation of distribution PV-systems. To implement the algorithm, it is assumed that records of ambient temperature, PV-system power generation cycle and winding temperature are available. With these data, the parameters of an equivalent thermal circuit are fitted in order to dynamically model the transformer hottest-spot. The method was validated using twelve-day records of a 70 kW p PV-generation system connected to a 75 kVA dry-type transformer. Results show that an enhancement in the hot-spot estimation is reached, and an assessment of the performance in real-time monitoring of the transformer capacity is achieved employing the proposed algorithm. [ABSTRACT FROM AUTHOR]

The Solar Heat Gain Coefficient (SHGC) is one of the energy loss factors in buildings, which affects a cooling load significantly. A variety of shading devices and high-performance windows have already been developed and applied to a large number of buildings to reduce a cooling load. However, performance evaluation on these shading devices and high-performance windows has depended on calculation via mathematical models and simulations. These evaluation methods have limits when reflecting heat characteristics of the ever-increasing complexity and development of window systems accurately in a realistic way. Thus, it is critically necessary to verify performance evaluation results through actual measure. The purpose of this paper is to measure the SHGC of various types of windows and shading devices and to analyze the difference between the calculated value and the measured value. The experimental result is as follows. SHGC of venetian blind is lower than SHGC of roll screen and Triple shade. The higher the glass SHGC was, the higher the SHGC reduction rate was under the same condition. The larger the slot angle was, the greater the SHGC performance improved. The analysis result on measured and calculated values showed that a mean different ratio was 4.86 %, which was matched within 5 % of the deviation rate. However, the different ratio tended to increase as the complexity of structures and types of windows increased. [ABSTRACT FROM AUTHOR]

In this paper, 16 cities representing four major architectural climate zones of China were selected, and the heating and cooling loads of office building during the period of 1961–2017 were simulated by using TRNSYS software. Daily extreme heating and cooling loads were determined by percentile methods, and the climate change impact on extreme loads was analyzed. The results showed that the days of extreme heating load of office building significantly decreased in almost all the selected cities, whereas there were no significant changes in the days of extreme cooling load. The daily extreme heating load was dominantly affected by the temperature (R2 = 0.43–0.79), but the daily extreme cooling load was related to multiple climate factors, including temperature, relative humidity, and solar radiation. Single temperature can only explain 3–37% of the changes of daily extreme cooling load, and the combination of multiple climate factors can explain 58–85%. Importantly, the effect of temperature on extreme cooling load showed decrease from the cold to hot climate zones, but the impacts of relative humidity and solar radiation gradually increased. These results suggest that the maximum design capacity of heating systems can properly decrease, and the design capacity of cooling systems may not largely increase with the climate warming. In addition, the combined effect of multiple climate factors rather than the single temperature, as well as the different responses of extreme cooling energy consumption to climate change in different climate zones, should be considered when making measures for improving operating efficiency of air-conditioning system. [ABSTRACT FROM AUTHOR]

PV panels are vastly used for sustainable electricity generation, while they can also help the environment by improving buildings' energy consumption. The best placement for PV panels installation in buildings with flat roofs is the roof. When placed on a building's roof, PV panels affect the building's energy loads by shading the roof surface. However, the shading effect of PV panels could be different depending on the roof's thermal properties and surface materials. The combined effect of shading caused by PV panels and cool materials could significantly change the roof surface temperature, and the building energy demand. In light of the lack of studies considering this combined effect, the present study aims to evaluate the energy-saving effects of different roof materials covered with solar PV panels for a typical residential building in four cities with different climate conditions in Iran. Applying a simulation tool, Ladybug Tools have been utilized for determining the building energy loads and PV panels' power generation. The obtained results indicate that PV panels significantly affect the cooling load of the building, especially during peak times. The hottest city, Bandar-Abbas, benefits the most, with a maximum saved energy ratio (SER) of 3.4%, while the coldest city, Ardabil, has the least SER, 0.5%. Additionally, in cold and moderate climates, the highest SER occurs for the lowest R-value and solar absorption roof, while for hot climates, the highest SER occurs for the roofs with the highest R-value and the lowest solar absorption. Overall, the shading effect of PV panels becomes more significant when solar absorption is high, and the roof R-value is low. Despite the decrease in cooling energy load, PV panels might increase the heating load. Depending on the climate, this contradictory effect of the roof's thermal properties and PV panels shading should be considered in the design process of buildings. Highlights: Cities with hot-humid and cold climates have the highest and the lowest SER, respectively. PV shading is more significant on roofs with high solar absorption and low R-value. The effect of PV panels on heating load varies based on climate. [ABSTRACT FROM AUTHOR]

In this paper, we propose a real-time cooling load forecasting system in order to overcome the problems of the conventional methods. The proposed system is a new load forecasting model that hierarchically combines Support Vector Data Descriptions (SVDDs). The proposed system selects an optimal attribute subset by our cooling load forecasting system that enables real-time load data generation and collection. The system is composed of two layers: The first layer predicts the time slots in three representative forms: morning, midday and afternoon. The second layer performs specialized prediction of each individual time slot. Since the proposed system enables both coarse-and fine-grained forecasting, it can efficient cooling load management. Moreover, even when a new time slot emerges, it can be easily adapted for incremental updating and scaling. The performance of the proposed system is validated via experiments which confirm that the recall and precision measures of the method are satisfactory. [ABSTRACT FROM AUTHOR]

It is crucial to optimize energy consumption in buildings while considering thermal comfort. The first step here involved an EnergyPlus simulation on a trade center building located in Tehran, Bandar Abbas, and Tabriz, Iran. A multi-objective optimization was then performed based on non-dominated sorting genetic algorithm II (NSGA-II) in jEPlus + EA to establish the building in the selected city where would benefit the most from implementing the radiant ceiling cooling system. Efforts were undertaken to choose environmentally-friendly materials. The final solution by Pareto charts resulted in a 52% reduction in energy consumption, a 37.3% decrease in cooling load, and a 17.4% improvement in comfort hours compared to the original design. Annual emission of greenhouse gas reduced as 167.67 tone of CO2 equivalent emission, 25.77 ton of CH4, and 0.2 ton of NO2. The mentioned algorithm was conducted for the first time on a trade center, including a DOAS system and radiant ceiling cooling system. Simultaneously, the environmental-friendly materials were dealt with. The procedure holds significant relevance for the design and optimization of buildings in Iran, especially wherever the climate is hot and humid. This approach offers advantages to the environment by reducing the impact on energy resources and utilizing environmentally-friendly materials. [ABSTRACT FROM AUTHOR]

In this paper, a thermoelectric air-cooling system was used to cool down the airflow window glazing surfaces during summer in hot climates by which cooling load of the indoors and occupant's thermal discomfort near the window reduce. The performance of the proposed system was modeled analytically, in which the models used were validated by the literature experiment results. To determine the thermoelectric system specifications, the three features of the system including the time working interval, the number of modules, and the degree of air temperature attenuation were investigated. The results show that using the thermoelectric air cooling system for the limited time interval within hours of peak cooling load can significantly reduce the energy consumption, while using the system for a longer time interval not only cannot decrease the energy consumption but also may increase. Besides, the results reveal that the thermoelectric system with 15 modules is required to be energy efficient. On the other hand, an increase in the number of modules more than 20 has no considerable effect on energy saving. Furthermore, the percentage of energy saving is 6.5% for 5 °C air cooling and reached a maximum of 7.1% for 7 °C air cooling, while for 10 °C, this value is zero. The mean reduction of the maximum interior glazing surface temperature is 5.9 and 7.4 °C for air cooling degrees of 5 and 10 °C. [ABSTRACT FROM AUTHOR]

This paper evaluates the effectiveness of combining direct load control with a residential zoned-cooling technology in meeting the objectives of reducing peak demand and maintaining home comfort level. In contrast, the traditional approach has been for utilities to smooth summer peak cooling loads, by controlling the cooling load of the whole house. While accounting for weather, dwelling characteristics and demographics, with detailed field data, we are able to develop empirical models to evaluate the benefits of utility control of cooling loads for a residential zoned cooling system during summer peak-demand periods and to compare with non-zoned systems. A zoned house allows for an upper floor cooling interruption without affecting the comfort on the main floor. An upper floor interruption for a full 4 h during the day leads to an average peak air conditioning change of −0.52 kW, approximately 1.6 times the reduction from the curtailment of cooling by cycling the air conditioning serving the whole house. [ABSTRACT FROM AUTHOR]

Birefringent microspheres, trapped in vacuum and set into rotation by circularly polarised light, demonstrate remarkably stable translational motion. This is in marked contrast to isotropic particles in similar conditions. Here we demonstrate that this stability is obtained because the fast rotation of these birefringent spheres reduces the effect of azimuthal spin forces created by the inhomogeneous optical spin of circularly polarised light. At reduced pressures, the unique profile of these rotationally averaged, effective azimuthal forces results in the formation of nano-scale limit cycles. We demonstrate feedback cooling of these non-equilibrium oscillators, resulting in effective temperatures on the order of a milliKelvin. The principles we elaborate here can inform the design of high-stability rotors carrying enhanced centripetal loads or result in more efficient cooling schemes for autonomous limit cycle oscillations. Ultimately, this latter development could provide experimental access to non-equilibrium quantum effects within the mesoscopic regime. By studying levitated optomechanics with birefringent vaterite microspheres in the focus of a circularly polarised light beam, the authors explain the unexpected stability of the trap against azimuthal forces and demonstrate feedback cooling of the residual particle revolutions (limit cycles) in the 2D plane. These findings are a first step towards designing high-stability rotors carrying greater centripetal loads and cooling to the quantum level. [ABSTRACT FROM AUTHOR]

As a building integrated solar thermal system, the dual-function solar collector integrated with building works for passive space heating in cold winter season, and for water heating in warm seasons. In this paper, the study is made on the dual-function solar collector integrated with building when it works in water heating mode with natural circulation. The coupled model of the collector and building's environment is established and validated. A numerical simulation is achieved to show the thermal effect of the novel system on the building in summer. By comparing with the cooling loads of the rooms with or without the novel collector in summer, the results show that when in summer, the novel solar system is available for serving hot water, and it does not have the summer overheating problem, and can even improve the thermal environment of its building slightly. [ABSTRACT FROM AUTHOR]

Buildings sector being responsible for more than one-third of the overall energy consumption is growing rapidly. One of the top priorities of building designers is to minimize energy consumption. This communication presents a multi-framework-based approach to optimize dwelling conditions and energy efficiency in subtropical climatic conditions. In the present work, the thermal behavior of indoor air is assessed by using Ansys Workbench while the Grasshopper plugin of Rhinoceros 3D is used to evaluate the daylighting under different scenarios. The study also involves a survey with a sample size of 289 people to substantiate the various optimization strategies. Further, the work encompasses the validation of respective approaches by comparing the results with measured values. Based on the results, it has been observed that using a ceiling fan and air conditioner alongside during the summer season in subtropical climatic conditions provides better dwelling conditions and reduces cooling load by 20–30% in comparison with an air conditioner alone. While consciously utilizing daylight by ensuring minimal illuminance of 500 lx is having the ability to decrease the lighting load by approximately 27%. Further, the results obtained from the present investigation can serve as a basis for providing better dwelling conditions with optimized energy utilization. [ABSTRACT FROM AUTHOR]

Refrigeration plays a vital role in ensuring quality and safety of seafood. In a tropical country like India, the seafood industry has a relatively larger cooling load throughout the supply chain due to higher temperature differences between ambient and chilled seafood. The cooling demands in a seafood processing plant are typically at four different temperature levels. Supply of chilled water at 2 °C, ice at − 5 °C, cold storage maintained at − 25 °C, and a plate or blast freezer at − 40 °C. Commonly, a multi-evaporator multi-stage refrigeration system with refrigerants like R22, R404A, or NH3 are used in India. However, R22 and R404A have harmful effects on the environment due to their high global warming potential. This study proposed an all-natural multi-evaporator CO2–NH3 cascade refrigeration system (CRS). For comparison, the refrigeration demands in a surimi (seafood) processing and storage plant located in Mumbai were utilized. The study revealed that CO2–NH3 CRS has the highest COP and the lowest annual energy consumption followed by conventional NH3 system. CO2–NH3 CRS exhibited 6.2%, 12.3% and 3.2% less energy consumption compared to R22, R404A, and NH3 systems, respectively. Similarly, CO2–NH3 CRS also showed the lowest total equivalent warming impact which is 26.8%, 44.3% and 3.2% less compared to R22, R404A, and NH3 systems, respectively. Furthermore, CO2–NH3 CRS also presented relatively better results in terms of annual cost rate and life cycle cost. [ABSTRACT FROM AUTHOR]

The work reported in this paper is focused on the performance of a thermoacoustic refrigerator under various operating conditions. The experiments were conducted with various stack geometries fabricated with epoxy glass and Mylar material. Four stacks with different pore sizes are used to evaluate the performance of the refrigerator. Stack 1 has parallel plates of Mylar material 0.12 mm thick spaced 0.36 mm apart. Stacks 2, 3 and 4 are made of epoxy glass with pores of circular cross-section having 1, 2 and 3 mm diameter, respectively. The entire resonator system was constructed from aluminium material coated with polyurethane material from inside to reduce conduction heat losses. Helium gas was used as a working fluid. The experiments were conducted with different drive ratios ranging from 1.6% to 2% with varying cooling load from 2 to 10 W. For the experiments, operating frequencies from 200 to 600 Hz with mean pressure varying from 2 to 10 bar in steps of 2 bar each were considered. The temperatures of the hot end and cold end of the heat exchangers were recorded using RTDs and a data acquisition system under various operating conditions. The coefficient of performance (COP) and relative COP (COPR) are evaluated. Results show that COP of the refrigerator rises with increase of cooling load and decreases at higher drive ratio. It was also observed that the temperature difference between the hot end and cold end of the stack is higher at 2 W cooling load for 400 Hz operating frequency. The temperature difference between the hot end and cold end of the stack was observed to be 19.4, 17.2, 14 and 12.4°C for stacks 1, 2, 3 and 4, respectively, for 10 bar mean pressure and 2 W cooling load. The temperature difference and COP of the parallel plate stack are better compared with other stack geometries. [ABSTRACT FROM AUTHOR]

An experimental study on use of humidification-dehumidification (HDH) technology for treating chemical milling wastewater containing high concentrations of sodium hydroxide and sodium aluminate has been carried out. Heat pump is introduced to simultaneously supply cooling and heating loads of the HDH system. A parametric study is conducted to investigate influence of operational parameters including frequency conversion characteristics of circulating fan and pump on system performance. Performance parameters including pure water production amount (PWPA), pure water recovery rate (PWRR) and gain output ratio (GOR) are analyzed. Results indicate working frequency of pump and fan is not as high as possible, there is an optimal value. With frequency conversion of fan increases, PWPA and PWRR are increased, GOR shows a trend of first increasing and then decreasing, the optimal value of circulated air mass flow rate is 0.44 kg/s. With frequency conversion of pump increases, PWPA and GOR are increased, PWRR is decreased, the optimal value of inlet wastewater mass flow rate is 0.465 kg/s. When system is operating under optimal parameters, PWPA is 9.77 kg/h, PWRR is 0.58% and GOR is 0.781. Compare the indicators before and after treatment, pH, SS, COD, NH4-N and TP of purified water is 9.2, 4 mg/L, 53.2 mg/L, 0.028 mg/L, 0.278 mg/L, respectively. All these parameters decrease 31.9%, 97.6%, 97.5%, 77. 8%, 94.8%, respectively. Although the purified water has not yet reached the direct discharge standard or reclaimed water reuse standard, but HDH method shows feasible in the separation of highly corrosive solutions. [ABSTRACT FROM AUTHOR]

The widespread availability of high-resolution digital elevation data and high computational capabilities, along with GIS tools, has revolutionized big data processing, management, and interpolation. The present investigation generates high spatial resolution maps of thermal comfort levels, heating (HDD), and cooling (CDD) degree days across the populated areas in Jordan. Results show that areas having indoor apparent temperature (IAT) of 26 °C or above, which represents warm/hot conditions on this thermal index, cover a large portion of the study area during July and August. This thermal zone encompasses a large cluster of the major urban centers in the country. For instance, Amman, Zarqa, and Irbid, which host more than 80% of the population of the country, experience 13, 14, and 19 h of warm to very warm conditions during July and August, demonstrating that cooling needs are required to bring about thermal comfort for dwellings and office buildings. Heavy cooling loads, 1700–2000 CDDs, are restricted to the Jordan Rift Valley (JRV) and other small, low-level urban centers. With the exception of the JRV, the populated areas in the country experience cold to very cold conditions during the three coldest months, December through February. Very cold conditions in winter, IAT ≤ 8 °C, span more than 13–14 h of the diurnal cycle in most urban centers. The HDD range from values close to zero along the JRV to ⁓ 1900 in the southern mountains. Heating loads for dwellings and office buildings are very demanding and represent a pressing financial challenge to bring about thermal comfort to homes and public buildings during winter. The present procedure can be integrated with auxiliary data within a GIS environment to investigate numerous climatological, environmental, and site suitability issues. The present procedure can be used for operational purposes over territorial or regional scales for a wide range of applications. [ABSTRACT FROM AUTHOR]

The Kingdom of Saudi Arabia has been in rapid growth in recent years, which resulted in an electricity consumption surge. The building sector consumes approximately 80 % of electricity, and air conditioners (A/Cs) are responsible for 50 % of that because of hot weather conditions. The dominant refrigerants in A/Cs are R22, a phase-out refrigerant yet used in old units, and R410A, which are supplied by different manufacturers and are sold at different prices. Refrigerant manufacturing is a complex process, and any deviation in the composition will have a direct impact on A/C performance. The present work aims to examine the quality of R22 and R410A refrigerants supplied from seven different manufacturers and imported to Saudi Arabia. System testing was conducted according to Saudi Standards, Metrology and Quality Organization cooling testing standards, and gas composition analysis was conducted using gas chromatography. Cooling load and coefficient of performance as well as the chemical composition of all seven refrigerants were tested and compared. Testing results have indicated that there is no cooling performance difference between different refrigerants manufacturers. Nevertheless, chemical composition testing showed slight differences between the tested refrigerants. In conclusion, refrigerants testing is recommended in order to maintain the quality of refrigerants. [ABSTRACT FROM AUTHOR]

Water dispensers are currently one of the essential home items. The international marketplace for water dispensers uses a vapour compression refrigeration cycle, which spends a large amount of energy and uses environmentally harmful refrigerants. In the present work, a numerical and experimental investigation for obtaining hot and cold drinking water using the Stirling cycle is characterized by saving energy, being environment-friendly, rapidly reaching the required cooling or heating loads, and having the highest possible performance. The present work uses a tubular heat exchanger as both a cold and a hot heat exchanger. According to Schmidt's analysis, the optimal water dispenser dimensions is calculated and experimentally confirmed for higher cooling/heating loads. The experimental and numerical results concluded that the machine speed increases the cooling/ heating load at various charged pressure. Also, the increase in the charged mass improves the cooling/heating load. The water dispenser can produce about 3 kW of cooling load and about 7 kW of heating load at 4 bars of charged pressure and 1200 rpm. [ABSTRACT FROM AUTHOR]

A combined cooling, heating, and power integrated system suitable for a residential complex, with two new cycles in hot and cold seasons, is proposed and designed here. By a comprehensive modeling approach (in four aspects of energy, exergy, economic, and environmental), the integrated system is optimized for variable electrical, heating, and cooling loads during a year. Two objective functions (exergy efficiency, η Ex , tot , and relative annual benefit, RAB) and six design parameters are considered for multi-objective Genetic Algorithm optimization. Also, a novel variable operational price method during the system lifetime was applied. Optimization results showed that selecting 14 gas engines (with 912 kW nominal power output) and 9 backup boilers (with a heating capacity of 1450 kW) leads to 74% of overall thermal efficiency and 1.6 years' payback period for the above studied integrated system. Furthermore, the comparison of results in integrated and traditional (buying electricity from the grid and burning fuel in boiler for providing heat) systems showed a 2.46 × 107 m3 year−1 (68% in comparison with traditional system) saving in boiler fuel volume flow rate, a 2.11 × 106 $ year−1 saving in boiler fuel cost, a 4.55 × 108 kg year−1 (87.5% in comparison with traditional system) reduction in CO, CO2 and NOx emissions and a 9.46 × 106 $ year−1 reduction in its corresponding penalty cost. [ABSTRACT FROM AUTHOR]

Energy performance of buildings is an important issue to estimate the energy waste of buildings and their impact on the environment, so designing energy-efficient buildings could improve their energy performance. In this case, the estimation of heating and cooling loads plays an important role in this regard. However, there are few factors with unpredictable influences on the heating and cooling loads. This study has attempted to analyze the eight parameters that can significantly affect the heating and cooling loads through the Neuro-fuzzy logic approach. Accordingly, the eight parameters of relative compactness, surface area, wall area, roof area, overall height, orientation, glazing area and glazing area distribution were considered as inputs and predicting the cooling and heating load changes was regarded as the output of this study. The model was developed and its results were measured in two regression indicators of r and RMSE. Based on the obtained results it was found that roof has the strongest impact on heating and cooling loads (RMSE: 4.3596), moreover, if two factors were concurrently changed, then the combination of relative compactness and wall area can significantly affect the heating and cooling loads (RMSE: 2.6312). The most influential combination of three factors is observed as well for the heating and cooling load and these factors are relative compactness, wall area and glazing area (0.5948). The most influential combination of three factors is observed as well for the hearing load and these factors are relative compactness, wall area and glazing area (RMSE: 0.5948 and RMSE: 1.5769 for heating and cooling load, respectively). However, Neuro-fuzzy logic showed overfitting for more than two inputs, therefore it is not recommended for more than two inputs. [ABSTRACT FROM AUTHOR]

Purpose: Buildings consume a large amount of energy for space cooling during the summer season, creating an overall sustainability concern. The upfront cost associated with sustainability repels the decision-makers to often end up adopting solutions that have huge operations and maintenance costs. Therefore, the purpose of this study is to assess the lifecycle cost (LCC) implications of optimum configurations of active and passive strategies for reducing the cooling load in buildings. Methods: Several green building active and passive strategies and technologies were assimilated and their thermal performance in a hot semi-arid climate of Lahore in Pakistan using DesignBuilder V6.1 was simulated to obtain the most optimum cooling load configuration. Furthermore, LCC is estimated, and overall efficiency is evaluated to identify the most effective space cooling configuration. Results and discussion: The results suggest that a configuration of EPS for external wall insulation, vertical louvers for external shading, 6 mm blue HRG (low-E soft coated) + 12 mm air space + 6 mm clear glass for windows, polystyrene as roof insulation, cross ventilation through windows, and LED lighting system has the best performance. This is the first-of-its-kind study in the hot semi-arid climate of South Asia with the city of Lahore in Pakistan as the test case and can be generalized for places with similar conditions. The findings will help the decision-makers in selecting the most load-efficient and cost-effective green building technologies to help improve overall sustainability. Conclusion: The implementation of the proposed strategies not only aids in providing user-friendly and effective decision-making but also promotes the adoption of sustainability in buildings by leveraging the existing green building technologies to enhance the environmental and economic aspects. This is a promising approach to facilitate the spread of green building construction in developing countries. It is recommended to utilize the strategies grouped in Scenario 8 to achieve a reduced cooling load and LCC of a residential building throughout its lifecycle. [ABSTRACT FROM AUTHOR]

Early assessment of the energy performance of buildings (EPB) is focused in this study. This task is carried out by predicting the cooling load (CL) in a residential building. To this end, due to the drawbacks of neural computing approaches (e.g., local minima), a novel metaheuristic technique, namely teaching–learning-based optimization (TLBO) is employed to modify a multi-layer perceptron neural network (MLPNN). The complexity of the proposed model is also optimized by a trial and error process. Evaluating the results revealed a high efficiency for this scheme. In this sense, the prediction error of the MLPNN was reduced by around 20%, and the correlation between the measured and forecasted CLs rose from 0.8875 to 0.9207. It was also deduced that the TLBO outperforms two benchmark optimizers of cuckoo optimization algorithm (COA) and league championship algorithm (LCA) in terms of both modeling accuracy and network complexity. Moreover, the TLBO-MLP emerged as the most time-effective hybrid as it required considerably lower computation time than COA-MLP and LCA-MLP. Regarding these advantages, the proposed model can be promisingly used for early assessment of EPB in practice. [ABSTRACT FROM AUTHOR]

Magnetic cooling at room temperature is one of the world's newest technologies that can be considered as an alternative for vapor compression refrigeration systems. Magnetic cooling follows the magnetocaloric effect (MCE) phenomenon, which is justified by the change in entropy with respect to magnetic flux changes. In this research, a computational fluid dynamic (CFD) simulation of the magnetic refrigeration system is conducted in COMSOL Multiphysics 5.5 software with the geometry of sandwiched gadolinium layers and water channels. The magnetic cooling system can be analyzed in two aspects i.e. constant cooling load and zero cooling load. For this purpose, two performance indicators including the exergy efficiency and the minimum achievable temperature, can be defined for constant and zero cooling loads, respectively. Sensitivity analysis is used as a tool to understand the importance of operating parameters such as frequency, passing fluid's velocity, cold heat exchanger temperature, magnetization, or demagnetization time. The parametric study of the zero cooling load simulation reveals that high operating frequency ( f = 0.5 Hz ) besides low fluid velocity ( V = 0.05 m s - 1 ) results in a 51 °C temperature span. In addition, the exergy efficiency can reach the maximum value of 30 percent with respect to various velocity and frequency variables for laminated geometry. [ABSTRACT FROM AUTHOR]

In this study, the cooling capacity and the pressure drop variation in an automobile radiator using nanofluid instead of water with antifreeze that are investigated experimentally. The nanofluid consisted of 50% Ethylene Glycol–Water mixture including Al2O3 nanoparticles with 0.5% volumetric concentration was used as coolant. In all experiments, the inlet temperature of the cooling fluid into the radiator was held constant at 95 C. The tests were carried out at the air inlet temperature between 23.4–28.6 °C, the air velocity between 1.7–4.3 m/s, the cooling loads between 2.5–15 kW and the cooling fluid flow rates between 10 and 25 L/min. Results demonstrate that 50% Ethylene Glycol–Water based 0.5% vol. Al2O3 nanofluid increased the cooling capacity of the radiator up to 15% compared to the fluid with only 50% Ethylene Glycol–Water mixture. Instead of 15% increment, radiator can make with smaller surface area up to 15%, or the flow rate can be decreased for same heat transfer rate, so fluid pumping power consumption can be reduced in order to save fuel as much as pumping power economy. In addition, it has not been observed a remarkable increase in the pressure drop. [ABSTRACT FROM AUTHOR]

Cooling demand is projected to increase under climate change. However, most of the existing projections are based on rising air temperatures alone, ignoring that rising temperatures are associated with increased humidity; a lethal combination that could significantly increase morbidity and mortality rates during extreme heat events. We bridge this gap by identifying the key measures of heat stress, considering both air temperature and near-surface humidity, in characterizing the climate sensitivity of electricity demand at a national scale. Here we show that in many of the high energy consuming states, such as California and Texas, projections based on air temperature alone underestimates cooling demand by as much as 10–15% under both present and future climate scenarios. Our results establish that air temperature is a necessary but not sufficient variable for adequately characterizing the climate sensitivity of cooling load, and that near-surface humidity plays an equally important role. Cooling demand project largely ignores the role of humidity. Here the authors show that in many of the high energy consuming states, projections based on air temperature alone underestimates cooling demand by as much as 10–15% under both present and future climate scenarios, due to the neglected role of humidity. [ABSTRACT FROM AUTHOR]

This study investigates the Neural Network Predictive Control of a vapor compression cycle (VCC). VCC consists of four components, namely the compressor, electronic expansion valve (EEV), evaporator and condenser. Modeling of the compressor and EEV is carried out with the static relationships, while modeling of the evaporator and condenser is performed with the lumped parameter moving boundary method. The established thermodynamic model is validated against the ASPEN model with the same design specifications. The neural network is trained off-line with the input and output signal data of the established model. The solution of the optimization problem for the each time step is achieved with the metaheuristic method called Whale Optimization Algorithm in the predictive controller. Ultimately, performances of the four different controllers, namely the cooling load, first law efficiency, entropy generation and second law efficiency, are compared with each other. The results show that the entropy generation controller achieves the most favorable exergy destruction performance with 0.2% lower than the worst performer cooling load controller. It is also observed that the second law efficiency controller is the best performer in terms of the overall second law efficiency through the simulation time. [ABSTRACT FROM AUTHOR]

Pseudo-single-crystalline zirconium samples were tested in a Bridgman chamber at a temperature of 20, 70, 100, and 300°C under the same loading conditions. The aim of these tests was to examine the possibility of preservation of the metastable ω phase at elevated temperatures. It was found that stable structural configurations emerge in the process of warm deformation as a result of formation of equilibrium interphase boundaries and oriented nucleation and growth of the ω phase. These configurations enhance the stability of the ω phase after cooling and load removal. Disperse zirconium hydride particles of a variable composition (δ-ZrH2 –x) were identified in the sample tested at 300°C. Its high hardness, which is comparable to that of the sample tested at room temperature, is attributable to the presence of these particles. [ABSTRACT FROM AUTHOR]

An analysis of real-world operational data of Tianhe-1A (TH-1A) supercomputer system shows that chilled water data not only can reflect the status of a chiller system but also are related to supercomputer load. This study proposes AquaSee, a method that can predict the load and cooling system faults of supercomputers by using chilled water pressure and temperature data. This method is validated on the basis of real-world operational data of the TH-1A supercomputer system at the National Supercomputer Center in Tianjin. Datasets with various compositions are used to construct the prediction model, which is also established using different prediction sequence lengths. Experimental results show that the method that uses a combination of pressure and temperature data performs more effectively than that only consisting of either pressure or temperature data. The best inference sequence length is two points. Furthermore, an anomaly monitoring system is set up by using chilled water data to help engineers detect chiller system anomalies. [ABSTRACT FROM AUTHOR]

Consumption patterns of residential building in Kingdom of Saudi Arabia (KSA) with specific reference to Qassim region are analysed to establish energy consumption indicators including consumption per dwelling, per capita and per unit area. The average shares of lighting, domestic appliances, water heaters and air conditioning out of total yearly consumption are determined to be 8.5%, 14.7%, 10.3% and 66.5%, respectively. Parametric analysis shows that residential energy consumption is insignificantly influenced by the type of building except that villas have somewhat higher consumption during the hot summer season. However, residential energy consumption is considerably affected by occupant behaviour, meteorological conditions, as well as the technical conditions of both building envelopes and air conditions setting temperature point. Energy efficiency measures are also discussed, and opportunities for energy saving are proposed. Potential energy savings up to 43% in air conditioning cooling load could be achieved by applying the KSA standard of envelope insulation. Total residential consumption savings of 3% could also be achieved by using efficient lighting and savings of 11.1% by adjusting the temperature setting point of air conditioners to 24 °C instead of 22 °C. [ABSTRACT FROM AUTHOR]

The exergoeconomic analysis was conducted theoretically for a steam turbine driving vapor compression refrigeration system using R134a, R410a, R407c and R717 in this study. Dual-purpose system was designed by eliminating the expansion valve to fulfill the demand for the cooling load of the steam power plant. Primarily steam turbine was investigated by changing turbine inlet parameters. Afterward, the effect of input parameters of the steam turbine on the cooling load, the coefficient of performance (COP), the exergy efficiency of vapor compression cycle (VCC) and equipment, both the exergy destruction ratio and the exergy efficiency was determined. Among all examined working fluids, R134a was the best candidate from thermodynamic and thermoeconomic viewpoints. The COP values were determined to be 2.73, 2.29, 1.8 and 1.15 for R134a, R410a, R407c and R717, respectively. Also, the exergy efficiencies of the vapor compression refrigeration (VCR) system were found to be 18.61%, 13.93%, 14.97% and 10.01% for R134a, R410a, R407c and R717, respectively. Conversely, the general exergy efficiency of the whole coal-fired plant was 39.1%. As a consequence of integrating VCC, overall exergy efficiencies of the complete system were 39.36%, 39.32%, 39.27% and 39.21% for four different working fluids, respectively. [ABSTRACT FROM AUTHOR]

In this study, the side effects of high-reflective and ordinary retroreflective materials, used as countermeasures to urban heat islands, are discussed. In addition, two retroreflective materials are proposed in order to avoid these adverse effects. These materials could be applied to roads and building exteriors to reduce their heat absorption from solar radiation. The first proposed type is the directional retroreflective material, which reflects light only during summer; therefore, it reduces the cooling load in summer, reduces the heating load in winter, and prevents light pollution at night. However, its structure is complicated and fragile; thus, it is suited for small areas, such as roofs and walls. The second type is the rough-surface retroreflective material, which shows weak retroreflectivity but can withstand distortion; thus, it is suited for roads. These two types require little maintenance, because they have no moving parts. Hence, these materials would not experience any breakdown, which is a great advantage for roads and building materials. Combining high-reflective, ordinary retroreflective, directional retroreflective, and rough-surface retroreflective materials, and assigning each type to the appropriate application would form an advanced mitigation system against urban heat islands. [ABSTRACT FROM AUTHOR]