Key action fields for nearly carbon-neutral districts: Stakeholder-specific strategies and practice

In accordance with the UN Sustainable Development Goals, many countries aim at nearly zero carbon emissions of their building sector by 2050. The research college EnEff.Buildings.2050 is a collaboration of five PhD students and their supervisors to support this goal. In this paper, five key action fields for transformation of urban districts are described, and decisive stakeholders are identified and linked to the action fields. As a case study, the urban district Mierendorff-Island in Berlin is introduced. Three strategies to support transformation are identified: Firstly, new digital planning tools should be applied to assess and improve the energetic performance of new and existing buildings and to illustrate it to decision makers. Secondly, digital processes should be combined throughout the lifecycle of a building by building information modeling (BIM). This can ensure the energetic quality and enable cost-effective construction, servicing and monitoring. Thirdly, start-ups and contractors need support for development of new business models and technical solutions, which can e.g. enable disruptive technologies. Awareness of stakeholders on the transformational state of a district enables them to identify windows of opportunity to spring into action. Framework conditions and support measures determine if they act in favour of the transformation or not

Equation-based object-oriented languages and tools report on the Workshop EOOLT 2007 at ECOOP 2007

EOOLT'2007 was the first edition of the ECOOP-EOOLT workshop. The workshop is intended to bring researchers associated with different equation-based object-oriented (EOO) modeling languages and different application areas making use of such languages together. The aim of the workshop is to explore common grounds and derive software design principles that may make future EOO modeling languages more robust, more versatile, and more widely accepted among the various stakeholders. At EOOLT'2007, nineteen researchers with diverse backgrounds and needs came together to present and discuss fourteen different concept papers grouped into the four topic areas of integrated system modeling approaches; hybrid modeling and variable structure systems; modeling languages, specification, and language comparison; and tools and methods

Equation-based modelling and simulation of hybrid systems

Equation-based modelling of hybrid systems has to consider dynamical systems consisting of components with continuous and/or discrete behavior. The paper focuses on such systems under special consideration of systems with variable model structure. Some ideas are presented how a simulation of continuous and discrete phenomena can be handled correctly. The main process is a continuing alternation between continuous and discrete simulation phases, where in the discrete phase the changeover can be performed to a new model structure which is valid during the next continuous phase. The paper addresses the problem of finding a new valid model structure as a process within the discrete phase. This new valid model structure has to be found under consideration of the time history of the model’s variables within the preceding continuous phase. To this end, the usage of the Linear Complementarity Problem (LCP) is proposed. After a definition of hybrid systems and the term model structure, different types of events – with and without influence on the model structure – are listed and properties of complementarity are presented. To find the correct switchover from continuous to discrete phase, so-called indicator functions are used. Contrariwise, to find the correct switchover from discrete to continuous phase, the LCP is applied. Some simulation results for an electromechanical system are presented shortly

Dynamic equation-based thermo-hydraulic pipe model for district heating and cooling systems

Simulation and optimisation of district heating and cooling networks requires efficient and realistic models of the individual network elements in order to correctly represent heat losses or gains, temperature propagation and pressure drops. Due to more recent thermal networks incorporating meshing decentralised heat and cold sources, the system often has to deal with variable temperatures and mass flow rates, with flow reversal occurring more frequently. This paper presents the mathematical derivation and software implementation in Modelica of a thermo-hydraulic model for thermal networks that meets the above requirements and compares it to both experimental data and a commonly used model. Good correspondence between experimental data from a controlled test set-up and simulations using the presented model was found. Compared to measurement data from a real district heating network, the simulation results led to a larger error than in the controlled test set-up, but the general trend is still approximated closely and the model yields results similar to a pipe model from the Modelica Standard Library. However, the presented model simulates 1.7 (for low number of volumes) to 68 (for highly discretized pipes) times faster than a conventional model for a realistic test case. A working implementation of the presented model is made openly available within the IBPSA Modelica Library. The model is robust in the sense that grid size and time step do not need to be adapted to the flow rate, as is the case in finite volume models

Dynamic equation-based thermo-hydraulic pipe model for district heating and cooling systems

peer reviewedSimulation and optimisation of district heating and cooling networks requires efficient and realistic models of the individual network elements in order to correctly represent heat losses or gains, temperature propagation and pressure drops. Due to more recent thermal networks incorporating meshing decentralised heat and cold sources, the system often has to deal with variable temperatures and mass flow rates, with flow reversal occurring more frequently. This paper presents the mathematical derivation and software implementation in Modelica of a thermo-hydraulic model for thermal networks that meets the above requirements and compares it to both experimental data and a commonly used model. Good correspondence between experimental data from a controlled test set-up and simulations using the presented model was found. Compared to measurement data from a real district heating network, the simulation results led to a larger error than in the controlled test set-up, but the general trend is still approximated closely and the model yields results similar to a pipe model from the Modelica Standard Library. However, the presented model simulates 1.7 (for low number of volumes) to 68 (for highly discretized pipes) times faster than a conventional model for a realistic test case. A working implementation of the presented model is made openly available within the IBPSA Modelica Library. The model is robust in the sense that grid size and time step do not need to be adapted to the flow rate, as is the case in finite volume models