R. Cobacho

Energy Audit of Water Networks

This paper presents the energy audit of a water network, which is obtained from the energy equation in integral form, and its time integration extended over a given period (day, month, or year). The analysis allows accounting for all the energy in the system, showing that the energy balance is maintained. This balance can be used to obtain performance indicators to assess the system from the energetic point of view. From these indicators, it is possible to identify the improvement actions that will make the system more efficient. This energy audit requires a previous water balance and the mathematical model of the network, both of which are necessary to know the energy flows through the system’s boundaries.

Integrated Water Meter Management

Water meters are the cornerstone of commercial systems for water utilities throughout the world; revenue is directly derived from the, figures provided by meters. Despite this, little attention has been paid, in terms of selection, replacement period and return on investment, to the management and optimization of water meters. Integrated Water Meter Management is a comprehensive reference for engineers and managers alike, providing: Integrated Water Meter Management is an invaluable resource for those involved in urban water management, including water utility managers, engineering technical staff, operations and maintenance specialists, meter-reading personnel and scientific researchers in this discipline. Contents This title belongs to Water Research Foundation Report Series ISBN: 9781843390343 (Print) ISBN: 9781780402253 (eBook)

Graphical Method to Calculate the Optimum Replacement Period for Water Meters

Calculating the optimum replacement period of meters has always been a major concern for water utility managers. Its determination is time-consuming and requires multiple calculations. This note presents a graphical method to obtain, in a simple but accurate manner, the optimum replacement period of installed meters. For this purpose, a chart has been produced, in which the most influencing variables are considered. These variables include the degradation rate of the weighted error of the meters, the selling price of water, the acquisition and installation cost of the meters, the volume consumed by the users and the discount rate. The chart also allows for a quick sensitivity analysis of different options. For example, by plotting straight lines it is possible to determine by how much the optimum replacement frequency of a meter would change if it degrades at a different rate than expected or if the selling price of water increases.

ENERGY ASSESSMENT OF WATER NETWORKS, A CASE STUDY

The complete urban water cycle requires large amounts of energy and so, there is an increasing motivation to optimize its consumption. In addition, the periodic energy crises (the last one, July 2008, brought the price of the oil barrel to 150 USD), the acute worldwide commitments to reduce greenhouse gas emissions and, last but not least, the need to minimise economic losses linked to leaks (including the energy costs) place water-energy issues on the front page of the portfolio’s research. A fact highlighted by the report “California’s Water-Energy Relationship” (CEC, 2005). According to this study, up to 19% of the total California’s energy consumption is related to water cycle, 6.5% associated to water distribution step, the one analysed here. Cabrera et al. (2010) developed a methodology to perform energy audits in pressurized water distribution systems obtained from the integral energy equation and its integration in extended period. Input energy (pumps, reservoirs) is equal to the energy consumed by users (through demanded water) plus leakage and friction energy losses in pipes. Energy audit requires the previous water audit as well as the mathematical model of the distribution network. From the energy audit, context and performance indicators (Cabrera et al., 2010) are calculated in order to assess the energy performances of the system. Furthermore, these indicators will help to identify future actions devoted to improve the network’s energy efficiency. Cost-benefit analysis is required to decide the best strategy to implement in practice. The paper is organised as follows. The fundamentals are firstly outlined and then, a case study to assess a real network from an energetic point of view is presented. The real network supplies Denia city (Alicante, Spain) and the surrounding areas. The whole distribution system supplies water in a very touristic area, close to 100000 people, which is an interesting case study because of current water scarcity and high energy consumption. Both facts explain the high fees paid by the final consumer, compared with those paid in the rest of Spain. Being Denia a hilly city at the east Mediterranean coast of Spain, the energy assessment is an interesting academic exercise although for the utility company (Aqualia) is much more than that –improving water-energy performances is a key objective to be competitive.

Nine steps towards a better water meter management.

The paper provides a comprehensive perspective of the critical aspects to be taken into account when planning the long-term management of water meters in a utility. In order to facilitate their quick understanding and practical implementation, they have been structured into nine steps. Ranging from an initial audit up to the final periodic meter replacement planning, these steps cover three aspects of the problem - field work, laboratory work and management tasks; and each one is developed in detail paying attention to the particular data needed and noting the practical outcome it will yield.

Discussion of “Simulating Nonresidential Water Demand with a Stochastic End-Use Model” by E. J. M. Blokker, E. J. Pieterse-Quirijns, J. H. G. Vreeburg, and J. C. van Dijk

The paper under discussion is one of the few published works related to the stochastic modeling of nonresidential water demand. The model proposed by the authors is of great interest and will help in improving the knowledge of consumption patterns associated with different types of uses. It will also serve as an excellent starting point for future developments in water-demand modeling. The discussers acknowledge that developing such a model is extremely complex due to the large heterogeneity of facilities and equipment and, in general, the diversity in users’ consumption patterns. Therefore, the discussers want to extend their most sincere congratulations to the authors for their study. However, based on the discussers’ experience, it is appropriate to make some clarifications regarding the modeling of water demand in hotels that will contribute to improving future developments in this field. For this purpose, actual consumption data obtained in different measurement campaigns for various hotel rooms is presented. In total, approximately 1,500 full days of measurements were analyzed. Water consumption was recorded with a volume resolution as low as 0.1 L, which allowed for a meticulous data analysis. By means of a specific software tool, the discussers were able to discriminate among the different uses of water in hotel rooms and to classify them into various microcomponents (toilet cistern, shower, and tap). This analysis was possible thanks to the high resolution measurements taken for hot and cold water consumption (Cobacho et al. 2005). As a result, the individual characteristics of the various end-uses present in a hotel room were obtained. The conclusions of this study are used to assess some of the assumptions made by the authors in their work.

Optimal Scheduling of Pipe Replacement, Including Opportunity, Social and Environmental Costs

Professor, Institute for Water Technology, Dept. Hydraulic and Environmental Engineering, Univ. Politécnica de Valencia, C/Camino de Vera, s/n 46022, Valencia, Spain (corresponding author). E-mail ecabrera@ita.upv.es Graduate Student, Institute for Water Technology, Dep. Hydraulic and Environmental Engineering, Univ. Politécnica de Valencia, C/Camino de Vera, s/n 46022, Valencia, Spain E-mail miparpi@ita.upv.es Assistant professor, Institute for Water Technology, Dep. Hydraulic and Environmental Engineering, Univ. Politécnica de Valencia, C/Camino de Vera, s/n 46022, Valencia, Spain. E-mail qcabrera@ita.upv.es. Assistant professor, Institute for Water Technology, Dep. Hydraulic and Environmental Engineering, Univ. Politécnica de Valencia, C/Camino de Vera, s/n 46022, Valencia, Spain. E-mail rcobacho@ita.upv.es.