•Comprehensive review of mixed-mode buildings studies since 2010.•Assessment of weather-dependent potential for cooling demand reduction.•Analysis of key factors such as simulations inputs, comfort ...standards and schedules.•Analysis of the control methods used for managing mixed mode buildings.
Ventilative cooling technologies have the potential to be an effective measure to reduce buildings energy consumption, by meeting some or all of the cooling requirement of a building without the need for mechanical cooling. Mixed-Mode (MM) buildings utilise both natural and mechanical cooling systems to meet their thermal energy demand. These buildings are able to guarantee that thermal comfort conditions are maintained, whilst exploiting the cooling potential provided by the climate. Effective management of the cooling systems in MM buildings is important to ensure that comfort is maintained and free cooling is exploited when available. While the implementation of hybrid ventilation systems is becoming more common, the current industrial and academic research state-of-the-art provide different and sometimes contrasting approaches to the management and evaluation of MM buildings. The current review provides an overview of studies into MM buildings performed in the last 10 years, analyzing in detail key factors that determine the potential of a building to save energy, including simulations inputs assumption, comfort standard used for evaluation, building and Heating, Ventilation and Air Conditioning (HVAC) systems typologies and control strategy employed. A detailed analysis of the papers which had a focus on methods for control of hybrid ventilation system was undertaken. This highlighted the importance of coordination between systems to ensure operational effectiveness and showing that while the majority of the studies employed classical control techniques, predictive control methods were the most investigated approaches to fully exploit the potential efficiency of MM buildings.
A systematic methodology for the real-time improvement of the overall efficiency of applications using hydraulic servo-axes is presented. The proposed methodology introduces three modules: a ...hydraulic actuator load estimator, a hydraulic energy optimizer and a controlled hydraulic power supply; these are discussed at the theoretical and application level. The proposed approach reduces the power losses across the main elements of the hydraulic circuit, leading to high energy savings and introducing a new guideline on managing and controlling the servo hydraulic actuator. The methodology is applicable to any application using hydraulic servo-axis systems, and therefore it is not tailored to a particular field. Its performances have been evaluated in different industrial case studies (a blanking press, a drawing press and a die-casting plant) through numerical simulations. Conspicuous energy savings, ranging between 59% and 88%, have been obtained in simulation, suggesting that a significant carbon footprint reduction for energy-intensive hydraulic machinery is achievable in a wide range of applications.
•Systematic methodology for the real time improvement of the overall efficiency of a hydraulic servo-axis.•Reduction of the power losses across the main elements of the hydraulic circuit, leading to high energy savings.•High bandwidth controlled hydraulic power supply.•The methodology applies to any application using hydraulic servo-axis systems, and therefore, it is not tailored to a particular field.•Its performances have been evaluated through numerical simulations in different industrial case studies.
Tailing impoundments are sources of high-risk pollution due to the accumulation of mining tailings and wastewater. As a result of thin karst overburden as well as actions of precipitation leaching ...and scouring, pollutants in the tailing impoundment can easily enter the karst aquifer through sinkholes, corrosion fissures and other channels, causing pollution to groundwater and is not conducive to the utilization of groundwater resources. Through the analysis of hydrogeological conditions, the boundary condition, aquifer structure, source-sink term, and hydraulic characteristics of groundwater are generalized, the groundwater flow model and solute migration model were established, and the migration mechanism of the characteristic pollutant (arsenic ions) was analyzed. The research results show that with the passage of time, the area of high-concentration polluted areas showed a decreasing trend, and the area of low-concentration polluted areas showed a decreasing trend; Under the influence of groundwater flow and the pollutant concentration difference, the pollution plume presents an elliptical shape with the long axis along the direction of water flow; The migration law of pollutants is controlled by the direction of groundwater flow, the concentration difference of pollutants and the permeability of the aqueous medium; The direction of groundwater flow determines the migration direction of pollutants, the concentration difference of pollutants determines the diffusion range of pollutants, and the permeability of aqueous media determines the migration speed of pollutants; Through the prediction of the pollutant control effect, it can be found that a reasonable number of pumping wells that do not interfere with each other are arranged around the groundwater flow channel, which can effectively control the migration of pollutants to the target area. The above research reveals the migration mechanism of pollutants in karst groundwater and main control factors, and also provides a scientific basis for the protection of groundwater resources in karst areas.
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•The migration law of pollutants in groundwater in karst areas is proposed.•The controlling factors of pollutant migration in karst groundwater are summarized.•Discusses the feasibility of pumping wells to control the spread of pollutants.
In order to improve the risks management and control ability of coal chemical enterprises, this paper studies the dynamic risks management and control model of coal chemical enterprises and develops ...the supporting application software. A dynamic risk classification control algorithm for coal chemical enterprises is constructed by combining the optimized neural network with a control chart. By analyzing the control chart, the optimized neural network is used to predict and early warn the risk development trend of enterprises, and optimize coal chemical enterprises' process flow. Based on dynamic risks hierarchical management and control, the matching application tool, “dynamic risks hierarchical management and control system” is developed. The software was applied in Hongxing company in September 2017, which was developed by C/S mode, and the server developed “Webservice” to connect SQL Server and phone. The system's real time operation through the mobile phone is fast and straightforward, which realizes the dynamic risk classification management and control of coal chemical enterprises, and achieves good results.
•The dynamic risks hierarchical management and control method is constructed.•The risks hierarchical management and control system is designed.•The research is applied experimentally in the coal chemical enterprises.
With the development of the Internet, Internet finance in new P2P modes will face a great many difficulties and opportunities; so, relevant risk early-warning models need to be researched and ...analyzed. The early-warning analysis will not only be helpful for P2P, the new mode, but will also be worth learning by the whole Internet financial industries, and there will be a particular demonstration effect. Deep researches have been made on Internet financial risk precautions mainly through analyzing and researching the risks in the leading P2P online debit and credit model within the scope of Internet finance; therefore, risk factors that influence the development of Internet finance are obtained. Next weighting KNN Internet financial risk management and control algorithm with the variable precision rough set is out forward. Training sets of different categories are divided into positive regions and boundary regions through the upper and lower approximation concept of variable precision rough set, thereby acquiring the affiliation regions of the samples based on the similarity between test samples and the sample center. In this way, the category of samples belonging to the positive region can be directly judged, and that of other regions can be judged through the KNN algorithm based on quantitative weighting. Experimental results have verified the effectiveness of the mentioned algorithm.
Traffic simulation tools are widely used in analyzing and enhancing the forecasting, planning, design, operations, and management of transportation systems. Despite the increasing use of traffic ...simulation through the years, there are still many needs and issues facing transportation agencies and modelers in their use of traffic simulation. These needs and issues have not been sufficiently surveyed and summarized in the literature. The goal of this study is to identify the current applications, needs, and issues of traffic simulation modeling based on a survey of public and private agencies in Florida, U.S. The study conducted an online survey of traffic simulation modelers in Florida, followed by phone interviews with a subset of the respondents to the survey. The survey addressed the types of the utilized traffic analysis and simulation tools, utilized simulation guidance, utilized traffic data and performance measures, calibration processes and resources utilized by agencies, the current practice of future year demand forecasting, and perspective on the simulation of emerging technologies. The results from this study will help understand the present situation of applying traffic simulation and future needs to enhance simulation modeling capabilities and practices.
Power Generation Forecast of Hybrid PV-Wind System Sanjari, Mohammad Javad; Gooi, Hoay Beng; Nair, Nirmal-Kumar C.
IEEE transactions on sustainable energy,
04/2020, Letnik:
11, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Due to their intermittency and unpredictability, increasing the penetration level of renewable energy (RE) resources to the power system leads to difficulties in operation. Reliable system operation ...requires a precise forecast of generated power by RE units. Photovoltaic (PV) and wind units are the significant portion of RE resources integrated into the power system. This paper proposes a forecast method for PV and wind generated power to achieve good prediction accuracy in different weather conditions. Not only is the relation between the wind and PV output power modeled, but the heat index (HI) is also taken into consideration as a useful meteorological variable to achieve the 15-min ahead precise expectation of PV/wind output power. Moreover, the input data are discretized in such a way that the best accuracy for the PV and wind power forecast is achieved. Comparing the results of the proposed method with the historical data recorded at actual PV and wind plants shows that the proposed forecast method results in high accuracy in PV and wind output power forecast. Moreover, the forecast model performance with HI consideration is compared with the model not using HI as an input variable.
The social and environmental impacts of the petroleum industry have serious consequences and call for sustainable solutions and practices. Embedding sustainability into organisations is vital to ...address these issues, and requires the integration of sustainability into performance management systems. The aim of this paper is to investigate the barriers to, and enablers of, sustainability integration in the performance management systems of an oil and gas company. A qualitative case study has been used to identify the stages and means of integration in the organisation, based on Gond et al.'s (2012) framework depicting the role of control systems in supporting sustainability integration within strategy. The findings revealed that although cognitive, organisational and technical enablers moved integration of sustainability forward in the organisation, certain cognitive barriers considerably affected the attainment of full integration. Institutional pressures provided the impetus for the development of enablers, giving rise to several implications for governments, academics and other parties. The study shows that sustainability integration in performance management systems could lead to better management and control of sustainability performance in organisations. This study provides a more comprehensive approach towards understanding the integration of sustainability in control systems from a socio-technical perspective.
•Parametric comparison of different concentrated hybrid solar PV/T configurations.•Waste heat recovery on PV cell significant improves performance.•Exergetic efficiencies can exceed 40% with heat ...recovery.•Percent of input energy stored as thermal exergy can easily exceed 40%.
Hybrid photovoltaic/thermal (PV/T) devices can simultaneously generate thermal and electrical energy, but have been limited to low temperature applications. This is done to avoid performance degradation of the PV cell at high temperatures. While the low temperature approach limits PV losses, it would be desirable to develop concentrating photovoltaic/thermal (CPV/T) systems which operate at higher temperatures where the thermal energy can be utilized for electricity production. In addition to using more of the sunlight, these systems may help realize low costs as well as dispatchability through thermal energy storage. Presented here are two primary configurations: the first where the PV cell and thermal system are decoupled, and the second where the PV cell acts as the high temperature absorber. The efficiency of these systems and their ratio of thermal to electrical energy produced are reported as a function of architecture, cell bandgap, and thermal system peak temperature. The studies provide a basis to understand and compare the performance of CPV/T at different operating conditions and architectures. The results indicate that the configurations that utilize recovery of waste heat off the PV cell can achieve the highest efficiency at low concentration ratios, but it remains to be seen if PV cells can survive the temperatures necessary. The thermally decoupled case is attractive in terms of efficiency and operating temperature of the PV cell, but requires significantly higher concentration ratios. Both configurations can achieve exergetic efficiencies exceeding 40% and greater than 50% of the solar energy converted to dispatchable thermal exergy.
Self-sustainability and intelligence will be critical features of the next generation of Internet of Things devices. Power management circuits need to be energy-efficient in multiple power modes, ...from nW sleep to mW active, and to support energy harvesting (EH) from multiple environmental sources. This article presents an adaptive and firmware-configurable power supply unit that enables intelligent devices to operate in the sub μW range while achieving self-sustainability through EH. The microcontroller-based design allows efficient conversion from batteries, dc, ac environmental sources, and nA quiescent currents. Source and load power points are decoupled with multiple dc-dc converters aiming to supply loads with adaptive voltage scaling and achieving high reliability. Experimental results show the flexibility and efficiency of this approach: the proposed power supply unit achieves a quiescent current of 54 nA and a maximum peak load current of 300 mA, delivered with an end-to-end power efficiency above 85%.
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