A stochastic approach for the water demand of residential end users

Reliable hydraulic modeling of water distribution networks requires a deep knowledge of water demand. In the past few years, technical literature has been enriched with many contributions aimed at realistically representing the residential water demand of end users. The proposed models generally represent water demand through rectangular pulses, describing demand as the sum of the requests from single domestic appliances. This paper proposes a new stochastic model - Overall Pulse (OP) - which allows the generation of the overall domestic demand as displayed at the house water meter. The proposed model allows the taking into account of the randomness of the arrivals rate and the demand persistence phenomenon. The effectiveness of the proposed model has been tested, comparing the generated data series with those measured for residences with different lifestyles. The generation of the synthetic data series has been made by means of the OP model with the Monte Carlo method.     

Water demand time series generation for distribution network modeling and water demand forecasting

Knowledge of water consumption can help water distribution network modeling. Consumption has been studied based on its stochastic and spatial random features. Considering the difficulty to have access to real-demand data, this work presents three methods to generate synthetically water demand time series from observed data, thus producing final demands in different ways. Each method generates a time series that considers either temporal consumption trends or jointly temporal trends and climatic influence. A random forest algorithm is applied to obtain the relevance of each climatic variable. This study uses water demand and climatic data of various Brazilian cities to extract temporal patterns. The final synthetically generated data can be used as input data for water network models, to feed the methods used according to the objectives of each study or project.     

潮汐对水质影响的时空相关性分析

时空相关性分析方法在生态环境空间分异性的研究中具有重要的应用价值.将水质监测数据与空间数据相结合,建立了具有时空特征的水质数据库.基于相关系数矩阵,研究了潮汐对镇江内江水质的影响及水质的时空分布规律.结果表明,镇江内江水质存在着时空相关性,目前这种时空相关性已受到人类活动的强烈干扰,使潮水对水质的净化效果大为降低.     

A data-centric bottom-up model for generation of stochastic internal load profiles based on space-use type

There is currently no established methodology for the generation of synthetic stochastic internal load profiles for input into building energy simulation. In this paper, a Functional Data Analysis approach is used to propose a new data-centric bottom-up model of plug loads based on hourly data monitored at a high spatial resolution and by space-use type for a case-study building. The model comprises a set of fundamental Principal Components (PCs) that describe the structure of all data samples in terms of amplitude and phase. Scores (or weightings) for each daily demand profile express the contribution of each PC to the demand. Together the principal components and the scores constitute a structure-based model potentially applicable beyond the building considered. The results show good agreement between samples generated using the model and monitored data for key parameters of interest including the timing of the daily peak demand.     

Implementation of a cogenerative district heating: Optimization of a simulation model for the thermal power demand

The district heating set up with a cogeneration system, concurs to attain energetic, economic and ambient benefits. It also provides to citizens a new service. The project strategy is based on the idea of supplying a portion of the necessary thermal power through a combustion alternative engine in cogeneration modality. It's also interesting to modulate the load with auxiliary boilers fed by natural gas. This solution allows to save primary energy, create a centralization of the energy production, which contributes to the problem of polluting emissions, through the decentralization of the sources. The first step to assess the technical-economic feasibility of a district heating system, based on a cogeneration plant, is to underline and to characterize the energetic request of the basin of user.The objective of the present work is to develop a model that yields an esteem of the hourly thermal load for every days of the heating season of a complex user, represented by a single neighbourhood.To do this, the present work proposes a new method of simulation of the daily and hourly thermal load trend, known only the value of the power installed in the thermal plant for every user, the seasonal hours of the burner operation and the timetable of the heating service distribution, more than the external mean daily temperature trend.The results obtained using this model, have been verified with the data of seasonal consumptions, confirming the validity of the proposed methodology.The above allows to determine, with more precision, the thermal request peak to satisfy, taking in consideration the contemporaneity of the loads, also of different typology, and to carry out a better sizing of the generation plant.     

Concept and prototype of a spatial decision support system for integrated water management applied to Ichkeul Basin,Tunisia

In this study, we develop a spatial decision support system (SDSS) for water management in a basin characterised by existing and projected dams to satisfy freshwater demand while preserving a particular ecosystem. The territorial and functional interests along with management scenarios were integrated into consistent stages of the SDSS. The developed prototype allowed comparisons of multiple water allocation options to competing users in the catchment by two aggregation methods. Through a simulation modelling exercise and stakeholder's involvement, the main outputs are the development of water management options and a set of criteria/subcriteria to evaluate these options related to socio‐economic, water availability and ecological factors. Both aggregation methods reveal the positive effect of water transfer on overall evaluations. New dam construction would cause an increase in the overall evaluation from the SDSS by at best 34% when water availability criteria are favoured, while a decrease in overall evaluation by at worst 75% is indicated when ecological criteria are favoured.     

Understanding Urban Spatial Structure of Shanghai Central City Based on Mobile Phone Data

Taking Shanghai Central City as its case study, this paper presents an approach to exploring the urban spatial structure through mobile phone positioning data. Firstly, based on base station location data and mobile phone signaling data, the paper analyses the number of users connecting to each base station, and further generates the maps of mobile phone user density through kernel density analysis. We move on to calculate the multi-day average user density based on a time frame of 10:00 and 23:00 at workdays and 15:00 and 23:00 at weekends for Shanghai Central City. Then, through spatial aggregation and density classifi cation on the density maps of 10:00 at workdays and 15:00 at weekends, we identify the ranks and functions of public centers within Shanghai Central City. Lastly, we identify residential areas, business off ice areas, and leisure areas in Shanghai Central City and measure the degree of functional mix by comparing the ratio of day and night user density as well as the user density at nighttime of workdays and weekends.     

西南地区工业遗产时空分布特征及其影响因素

工业遗产承载着人类社会的变革,也记载着城市的历史,对其时空分布特征及影响因子的研究是保护和活化利用的重要依据。西南地区自然地理环境独特,使得其工业发展同中东部地区相比有自身的特殊性。选取西南地区48处国家级工业遗产为主要研究对象,运用GIS空间分析等方法分析工业遗产的时空分布特征及其影响因素。结果表明：1)从时间分布看,西南地区工业遗产具有时间跨度大、历史延续性强、阶段性突出的特征,且以近现代工业遗产为主;2)西南地区工业遗产在空间分布上呈“东多西少”的不均衡态势,其空间分布类型为集聚型,表现出“大集中、小分散”“东密西疏”的聚集特征,形成了“一核一副、带状分布”的分布格局;3)在影响因素方面,西南地区的工业遗产分布受自然地理、社会经济、历史环境和政府政策等多方面因素的共同影响。研究成果形成西南地区工业遗产时空分布及其内在机制的地域特征的前沿探索研究,对西南地区工业遗产研究具有基础作用。     

The use of screening models in determining water supply reliability

Accurate estimation of water supply reliability is often hindered by a paucity of historic streamflow data and the expense of adequate system modelling. A procedure using synthetic streamflow generation and screening models in determining water supply reliability in a cost-effective manner is presented. A series of screening models are developed to evaluate numerous synthetic streamflow data to select from them desired flows for incorporation into an optimization model. Results from the optimization model are used to generate cumulative distribution functions of system reliability. The water supply system serving Seattle, Washington is used as a case study.     

A model of the filling process of an intermittent distribution network

In many countries, private tanks are acquired by users to reduce their vulnerability to intermittent supply. The presence of these local reservoirs modifies the user demand pattern and usually increases user water demand at the beginning of the service period depending on the tank filling process. This practice is thus responsible for the inequality that occurs among users: those located in advantaged positions of the network are able to obtain water resources soon after the service period begins, while disadvantaged users have to wait much longer, after the network is full. This dynamic process requires the development of ad hoc models in order to obtain reliable results. This paper discusses a numerical model used for evaluating this complex process as well as the application of model to an Italian case study. The model agreed with calibration data and provided interesting insights into the network filling process.     

Using water consumption smart metering for water loss assessment in a DMA: a case study

ABSTRACT

In this study we analyse the benefits that may be gained from using a smart metering system to assess water losses at a district level with reference to a real case. Consumptions of all the users of this district metered area (DMA) were monitored at an hourly time step by means of electromagnetic meters. Assuming that information on water consumption was available for only a portion of users, we then estimated the water consumption of the entire DMA and calculated the error committed in this estimation as the number of available users varied. Finally, as the simultaneous hourly pattern of inflow into the DMA was also available, we used the water balance method to assess water losses. The results obtained show that monitoring even only 60% of users makes it possible to achieve an error of less than 2% in the estimation of daily consumption across the entire DMA.     

Methodology to estimate building energy consumption using EnergyPlus Benchmark Models

The evaluation of building energy consumption usually requires building energy profiles on an hourly basis. Computer simulations can be used to obtain this information but generating simulations requires a significant amount of experience, time, and effort to enter detailed building parameters. This paper presents a simple methodology to estimate hourly electrical and fuel energy consumption of a building by applying a series of predetermined coefficients to the monthly energy consumption data from electrical and fuel utility bills. The advantage of having predetermined coefficients is that it relieves the user from the burden of performing a detailed dynamic simulation of the building. The coefficients provided to the user are obtained by running EnergyPlus Benchmark Models simulations; thus, the simulation process is transparent to the user. The methodology has been applied to a hypothetical building placed both in Atlanta, GA, and in Meridian, MS, and in both cases, errors obtained for the estimated hourly energy consumption are mainly within 10%.     

Characterisation of NMHCs in a French urban atmosphere: overview of the main sources

Continuous hourly air quality data involving 37 C2-C9 non-methane hydrocarbons (NMHC) over 4 years are reported for the first time in Lille metropol, northern France, at two urban roadside and background sites. The data have been analysed in two complementary steps: univariate statistics which define the spatial and temporal characteristics of NMHC by constructing the seasonal and daily concentration profiles, and multivariate statistics based on principal component analysis (PCA). A number of important sources have been clearly identified depending on the season: (1) motor vehicle exhaust, which dominates the NMHC distribution and particularly in winter, even for isoprene; (2) wintertime stationary combustion and activities related to fossil fuel consumption in general, such as natural gas leakage of ethane and propane; (3) summertime evaporative emissions from fuel and solvent; and (4) summertime biogenic emissions through isoprene behaviour and their dependence on temperature.     

Stochastic modelling of mean monthly flows of Karasu River,in Turkey

Stochastic modelling of streamflows is vital for planning water resource systems. In this study, a stochastic model of the mean monthly streamflows at 2154 A?a?ιka?dariç Gauging Station on Karasu River was constructed. Studies were carried out using data from the water yearbooks published by chk later onEIE. The modelling procedure for streamflows with constant coefficient autoregressive moving average (ARMA) models was given in detail and indicated models were constructed. Analysis with streamflows at 2154 A?a?ιka?dariç Gauging Station showed that the autoregressive (AR) (1) model is the most appropriate model among the competing models. While selecting the most efficient model the Akaike information criterion (AIC) was used. The Port–Manteau test showed that residuals are white noise series. Using the AR(1) model, 100 synthetic series were generated and the time series generated were found to have the same statistical parameters (monthly mean, monthly standard deviation and autocorrelation) as historic time series within 95% confidence intervals.     

Comparison of Variance-Reduction and Space-Filling Approaches for the Design of Environmental Monitoring Networks

Abstract:   This article focuses on the design of groundwater monitoring networks to detect contamination with nitrates from agricultural origin. This is a problem that has been in the minds of the general public, scientists, governmental agencies, and legislators for some time now. If one looks at European statistics, despite still incomplete data, in 13% of the regions the 50 mg/l European water quality standard for drinking water (Drinking Water Directive, 98/83/EC) is exceeded in more than 25% of the monitoring stations. A compliance groundwater nitrate-monitoring network is developed for a case study in the south of Portugal (Gabbro of Beja aquifer system), using both variance-reduction and space-filling approaches. In the first the variance of the error of estimation obtained by ordinary kriging is used, after building a covariance model, and the objective is to minimize the average kriging variance. In the second approach a criterion for the quality of spatial coverage is used, usually based on a metric. The objective here is also usually to minimize a function of the metric (criterion). The search for a solution is made in an iterative manner, by replacing one station, analyzing the result, and deciding whether to keep the solution or not. Due to the enormous number of possible combinations even for small networks, a structured search method, the simulated annealing method, is used to obtain the final network.     

基于通断时间面积法的热分摊技术的工程应用

为验证通断时间面积法热分摊技术工程应用的可行性,在石家庄、衡水、邢台、唐山等城市的既有建筑热计量改造中采用了该技术.通过对2010-2011年供暖季实际运行数据的整理与计算,给出了各热用户单位面积供暖耗热量以及各城市单位面积平均耗热量,然后根据历史运行数据以及入户调查结果对数据进行了综合统计分析.结果表明,基于通断时间面积法的热分摊技术能正确表征用户的用热需求大小,可以实现合理、公平的热计量目的.     

A combined Markov-chain and bottom-up approach to modelling of domestic lighting demand

Detailed simulations of distributed generation in residential areas have prompted the need for improved models of domestic electricity demand that are able to reproduce important features of real household loads. The high share and temporal variability of the lighting demand make it of special interest, in particular when the models are to be used in simulations of distributed photovoltaics (PV), which to a high degree is negatively correlated with the lighting demand. In this paper, a stochastic bottom-up model based on domestic occupancy patterns and data on daylight availability is presented. A three-state non-homogeneous Markov chain is used for generation of occupancy patterns and a conversion model transforms occupancy patterns to lighting demand, with respect to the daylight level. Markov-chain transition probabilities are determined from a detailed set of time-use (TU) data in Swedish households and the parameters in the occupancy-to-lighting conversion model are adjusted to make the resulting load curves fit recent measurements on aggregate population level. The performance of the model is analysed by comparison of simulated demand to measured lighting demand. It is concluded that for both individual households and aggregate demand, all relevant features of measured demand are realistically reproduced.     

Spatial and temporal variation in indicator microbe sampling is influential in beach management decisions

Fecal indicator microbes, such as enterococci, are often used to assess potential health risks caused by pathogens at recreational beaches. Microbe levels often vary based on collection time and sampling location. The primary goal of this study was to assess how spatial and temporal variations in sample collection, which are driven by environmental parameters, impact enterococci measurements and beach management decisions. A secondary goal was to assess whether enterococci levels can be predictive of the presence of Staphylococcus aureus, a skin pathogen. Over a ten-day period, hydrometeorologic data, hydrodynamic data, bather densities, enterococci levels, and S. aureus levels including methicillin-resistant S. aureus (MRSA) were measured in both water and sand. Samples were collected hourly for both water and sediment at knee-depth, and every 6 h for water at waist-depth, supratidal sand, intertidal sand, and waterline sand. Results showed that solar radiation, tides, and rainfall events were major environmental factors that impacted enterococci levels. S. aureus levels were associated with bathing load, but did not correlate with enterococci levels or any other measured parameters. The results imply that frequencies of advisories depend heavily upon sample collection policies due to spatial and temporal variation of enterococci levels in response to environmental parameters. Thus, sampling at different times of the day and at different depths can significantly impact beach management decisions. Additionally, the lack of correlation between S. aureus and enterococci suggests that use of fecal indicators may not accurately assess risk for some pathogens.     

A spatio‐temporal measure of spatial dependence: An example using real estate data*

The computation of Moran's I index and his statistics test relies mainly on an exogenous specification of a spatial weights matrix. However, the exogenous weights matrix is usually developed in a strictly spatial context, even when data are collected over time. This paper develops a spatio‐temporal weights matrix and uses the new definition to evaluate spatial dependence using Moran's I index applied to real estate data for Québec City from 1986 to 1996. The results are compared with the original Moran's I index using a strictly spatial weights matrix specification based on Euclidian distance or contiguity. The findings suggest that ignoring the temporal dimension could lead to misinterpretation of the ‘real’ measure of spatial dependence over time. However, the time dimension cannot explain the total spatial autocorrelation since the Moran's I index is still significant even when adjusting for time consideration. The differences between the estimated indices and statistics depend on the structure of the spatial and the temporal weights matrices that are used to construct the complete spatio‐temporal weights matrix.     

基于时空数据模型的历史地图集编制研究

针对历史地图集中编制对象的时空变化,探讨了时空数据模型的构成要素,建立基于时间、位置和对象的历史地图集的时空数据模型,并从时间关系、空间关系、对象关系三方面对历史地图集的编制进行设计,促成了图集编制工作的科学、合理、高效。以宁波历史地图集编制为例,通过地图表达制图区域的编制对象信息,又反映历史时空变化信息,展现了宁波区域历史上各朝代的疆域范围及社会发展状态。