Interactive decision support for operation and energy management of water systems based on multi-objective optimization methods
A constant, secure and area-wide supply with drinking water is one of the most essential tasks of each community. On one side, designers and operators of drinking water systems need to take into account the security of supply and a high water quality. On the other side, a sustainable withdrawal of water and a high energy- and cost-efficiency need to be ensured.
Spending about 29 kWh per resident each year for procurement, treatment and transport of drinking water, the benefit of energy-efficiency becomes apparent. Assuming an electricity rate of 20 ct/kWh and about 80 million residents in Germany, the cost for drinking water supply are at about 460 million € per year which will increase with the increasing energy cost.
One energy-intensive part of drinking water systems is the operation of the pumps. For example the energy cost of the Stadtwerke Kaiserslautern Versorgungs-AG are 600000 € for transport of water, only. Studies on 2500 well pumps have shown that about 37% of these pumps operate under inefficient conditions, because they are not matched to the systems and/or operated correctly. The reasons therefor are very often the complexity, the numerous parameters and the unsteady operation of these systems. This problem is addressed in this research project.
The goal of the project is the development of software for the simulation and optimization of drinking water systems taking into account energetic and economic aspects. The users shall be the operators of these systems as well as planning offices. The software allows an integrated analysis of drinking water systems. All components from the fields procurement, treatment, transport and storage which are important for energy efficiency and their interaction can be analyzed (Fig. 1).
Fig 1: Components to be modeled with the software using the example of water system Rote Hohl, Kaiserslautern, Germany
In combination with modern optimization methods, the system is simulated and optimal components can be specified taking into account not only energy cost, but also other criteria as life cycle cost, operating cycles of pumps, security of supply, avoidance of hydraulic shocks, etc. For this multi-objective optimization problem not only one, but a multitude of solutions exist, which each is the best trade-off for a specific system configuration. Based on these solutions, the user has to make a decision on the configuration of the system. Using a graphical user interface for decision making, the user can analyze interactively each solution and obtain an integrated picture of the operation of the system. Because of the optimization it is assured that only the trade-off solutions are analyzed. Including a database of components as, e.g. pumps, it will be possible to find optimal alternatives to already existing components. A schematic visualization of the software components is shown in Fig. 2.
Fig. 2: Schematic visualization of the software components
The modelling of the waterworks and the network of pipes is the main activity at the beginning of the project. For the waterworks, models of wells, pumps, components for water treatment and storage will be developed. For modelling the network of pipes already existing software as e.g. EPANET and interfaces to commercial software will be integrated in the software. First, the models will be developed using the example two systems of the participating partners. It will be ensured, that the models are parameterized in such a way that latter, arbitrary systems can be modeled through drag & drop using a graphical user interface. In a nationwide survey among operators, technical and economic data will be collected from further operators and included into the software model so that not only the systems of the participating operators can be analyzed with the software. The software is validated by measurements in the systems of Stadtwerke Kaiserslautern Versorgungs-AG and EWR AG Worms, as well as measurements at test rigs in the lab of the Technical University of Kaiserslautern. The integrated analysis of the systems is completed by a life cycle cost analysis which is carried out for each component of the system. For the optimization customized operation methods will be developed and included in the software. For the visualization of the optimization results, a graphical user interface will be developed, showing the trade-offs for each parameter and objective. In a pilot study, the operation of twelve well pumps will be optimized and the capability of the software will be demonstrated.
The consortium consists of a research institute, a Fraunhofer institute, an engineering consultancy and two operators of drinking water systems.
The Institute for Fluid Mechanics and Turbomachinery (SAM) of the Technical University of Kaiserslautern is responsible for the coordination of the project. The research activities of the institute are in the field of hydraulic and thermal turbomachinery as well as in general Fluid Dynamics.
The Fraunhofer Institute for Industrial Mathematics (ITWM) develops models and methods for simulation and optimization in a wide area of applications. The ITWM belongs worldwide to the leading institutes for multi-objective optimization.
The engineering consultancy Obermeyer Planen + Beraten GmbH (OPB) ranks as one of Germany`s largest independent engineering consultancies. The business segment water & waste management has over 50 years experience in planning systems for water distribution and treatment
The SWK Stadtwerke Kaiserslautern Versorgungs-AG (SWK) is a public utility company located in Kaiserslautern, Germany. In the field of drinking water, SWK operates in total 18 waterworks and supplies about 210000 residents in the Kaiserslautern area.
The EWR Netz GmbH located in Worms, Germany is a public utility company supplying drinking water for the cities of Womrs, Bürstad and Lampertheim with in total 119000 residents.