Rechnergestützte Analyse und Konzeption industrieller Energiesysteme

• Computer aided analysis and design of industrial energy systems

Augenstein, Eckardt Marc Günter; Lucas, Klaus (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2009)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2009

Abstract

In this dissertation the concept and implementation of a software system supporting the analysis and the design of industrial energy systems is presented. As a basis, a software framework was designed supplying a domain specific object model allowing the description of energy systems as well as the energy auditing projects performed with the software. Moreover, a set of graphical and textual editors needed to model the examined systems is part of the framework. On the other hand, the professional methods for analysis, assessment and optimization of energy systems are implemented in modules integrated into the system via a plug-in interface. The object model whose definition was based on a meta model approach allows the description of network like structures typical to energy systems. In order to keep track of the different work steps performed during an analysis project, these steps are reflected in the object model as "method applications" using a tree as the basic structure of a project. In order to allow the compatibility of information a set of conventions for the evaluation of energy flows and system balances was introduced. Moreover, all data elements used in modules or model components are derived from a central database guaranteeing a consistent usage of terms, descriptions, validity ranges and data types. The single professional modules like simulators or optimization methods access the object model via an appropriate software interface. Moreover, they make use of the framework’s user interface engine by delivering a generic description of dialog screens and result reports. As all modules share the same set of objects modelling the components of the energy system surveyed, the flow of information from module to module can be designed virtually seamless. Compared to a number of stand-alone solutions, this integrated design approach has the advantage that by combining a set of specialized methods an overall solution for complex engineering tasks can be created. The modules implemented up to now form a solution for the computational support of industrial energy audits. Nevertheless, the framework could be used as a basis for other fields of engineering. As an example for a complex module, a simulator for the calculation of industrial energy supply systems is presented. This module allows modelling of supply systems with low effort in order to calculate the annual costs, system efficiency and emissions. Besides technical components for the conversion, storage and transport of energy, other decisive elements like energy tariffs can be modelled. As input for the simulation, time series of the different target energy demands are needed. As detailed design data of the components is usually not available, the model parameters are typically restricted to the data found in technical data sheets. Moreover, typical sample times of energy demand time series will be 15 minutes or higher, so that dynamic effects below this time interval are neglected. For the purpose of analysis it turns out to be advantageous to assess a supply system without the influences of the concrete system control strategy, which means to run the simulation under the regime of an optimal control strategy. Even in cases where the control strategy is to be taken into account, this approach allows a simpler modelling of the system control as aspects with little impact on the system efficiency can be left to the optimizer instead of formulating appropriate rules. In order to allow an operation optimization of machines whose efficiency depends on temperatures in addition to the part load state (e.g. chillers), an optimization method which allows for quadratic constraints was selected. In order to achieve a method most robust towards the large variety of systems structures to be handled, a combination of evolutionary algorithms and mixed integer linear programming was chosen. In order to create supply system models, component models can be chosen from a template library and combined by connecting their external interfaces with bonds representing an energy or medium flow of a certain type. Each model component may contain subsystems leading to a hierarchal model structure. To define the behaviour of the components, a model description language adapted to the mathematical model was developed. The application of the system is demonstrated in an example of use.

Institutions

• Chair and Institute of Technical Thermodynamics [412110]