In the public sector the water supply is one of the major consumers of electrical energy. At the same time, for means of pressure control in the water pipelines, energy has to be “destroyed” constantly by converting it into useless noise and thermal energy. The project EWID shows new ways of reducing this energy loss. Turbine-driven pumps (pump as turbine, PaT) assume the function of conventional pressure reducers in the water distribution system and, at the same time, produce electrical energy. Hereby the energy balance in the water system is improved and a contribution to the energy self-supply is made.
The delivery of water follows typical seasonal and daily profiles, which are usually overlaid with current supply fluctuations. This leads to constant pressure fluctuations, especially in the lower areas of the network located in close vicinity to the consumers. Under these conditions, only a part of the pressure energy can be converted to electrical energy if a turbine is “simply” installed in the pipeline. Therefore, one goal of EWID is to design a system that adapts itself to the current situation dynamically and intelligently.
Fig. 1: Height differences for energy production in model region Bavarian uplands
This research project contributes significantly to energy efficiency and energy generation in the water management sector. The intelligent pressure control also contributes to the reduction of material stress and water loss, thereby promoting the sustainable use of natural water resources.
The aim of this project is the replacement or the implementation of the “classic” energy-dissipation-based pressure management in the water distribution system (by means of valves) with an energy-generation-based pressure management. The advantages of this approach are twofold: first, new chances of electrical energy production can be developed; second, new ways of improving the energy efficiency in the water sector can be identified.
In the research project a PaT-System (pump as turbine) will be developed. It is composed of a pressure control unit plus an energy production unit (running backward pump + generator) and a higher-level control for the intelligent pressure management. This system configuration constitutes the testing device. For the different development stages of the PaT-system with its additional components, extensive testing on a test stand (test track and testing facility) is required. The design of this system is accompanied by the compilation of the process principles for the internal control of the unit. Here, algorithms for the optimized pressure control in the distribution network must be developed. In order to define the testing configuration for the system, the boundary conditions of the application partners must be defined and suitable pilot areas must be selected. The network data from GIS and process control systems will be provided by the network operators. If the data are not sufficient, additional measuring must be carried out beforehand. For the comparability of the total recorded data, it must be transferred into a common data structure in a unified way.
The aim here is the decentralized compilation, transfer and processing of data in the network of the water suppliers. Hard- and Software components must therefore be developed. These must enable a secure and efficient data transfer between the communication units (Com-Units) in the network (inclusive cross-communication) and the central control system, through the implementation of different interfaces, as well as the linking of sensors, control units and analog/digital input/output signals to decentralized network stations. Due to the dynamics in the water distribution system, this must happen in “quasi real time”. While the dynamic model adaptation takes place, the transferred information must be used for deriving control logics and commands for the intelligent pressure management for controlling the hydraulic PaT-units (testing device and field tests).
Fig. 2: Technical plant for pressure increase/reduction
The objective here is the link between optimized demand-based pressure control for the distribution system with the maximum energy production performed by the PaT-unit (testing device and later in field tests). The “near real time” modeling of the water network combined with optimization strategies must therefore be tested. Control strategies for the “intelligent” pressure management, based on physical real-time-measured parameters, such as pressure and flow, as well as model-based data have to be developed und validated.
In addition, data regarding potential energy production and investment costs will be collected, and recommendations for the energy use in island operation will be worked out. After the design and validation of the “novel system unit”, it will be installed in a real network. Hereby the system control with installed pressure sensors at critical points must take place, in order to test a decentralized pressure management. After a successful start-up, the system must be calibrated and optimized, and its performance must be adapted for continuous operation.
Based on the results of the testing device and on the verification of the system in a real network, a guideline will be presented by means of a final report, as a practical working tool for professional associations (DVGW), water suppliers, municipalities and planers. For enabling the application of the designed system in other companies in the water sector, a detailed compilation of the technical and administrative boundary conditions will be carried out. Topography, population density, hydrogeology and climate act a decisive part. Also the supply structures (centralized/decentralized) and network size will be considered here.