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Potential waste heat integration in low-temperature district heating (LTDH) systems is a main task for future sustainable heat supply. For evaluation of efficient LTDH integration in residential areas, investigations of the typical building stock are useful. In this study, we present an economic and ecologic investigation of two LTDH supply temperatures in multiple typical residential areas. We show which design have the strongest impact on efficient heat supply in terms of electricity usage and low specific heating costs. Therefore, we design nine representative residential areas derived from dwelling types of the German building stock. Within these areas, we investigate LTDH supply performance in combination with decentralized boosting heat pumps. In addition, we compare the results to an individual heat supply by air-water-heat pumps. The results show that the fraction of domestic hot water on total heat demand and the design of decentralized heat pump systems capacities impact LTDH operation efficiency. LTDH network installation with operation temperatures around 60 °C are most advantageous in residential areas with a high share of space heating demand.

With the increasing share of distributed renewable energy sources not only the need for distributed energy storages rises, but also the need to coordinate those storages in the context of their local micro-grid. This publication illustrates the impact of battery energy storages on the overall performance of a district energy system. The energy system is controlled in a distributed way by using a multiagent approach that is scheduled by a market-mechanism. This market-mechanism allows to coordinate many individual agents with only few restrictions. The individual agents are flexible in the internal approach to forecast power supply or demand, allowing easy development of agents using individual algorithms.Besides pure consumer or producer agents, the battery storage forms a prosumer agent that can consume energy in some time-steps while supplying energy in others. By this, battery agents provide flexibility to the micro-grid while also aiming to generate profit for the owner. This approach is therefore attractive to both, the district energy system and the battery storage operator. The presented battery agents use model predictive control to determine the optimal operation strategy/bid for the upcoming time horizon. The determination of optimal strategy does not only assume losses but also takes the resulting degradation of the battery-cells into account. In a case study, we show the impact of battery storages on the overall system performance. As a main part of the publication, a sensitivity study reveals the importance of the individual parameters and how the revenue of the storage agent is affected. By adapting the charging and discharging power by 20 %, the profit can be increased by 33 % for the presented case.

This contribution introduces a new system for distributedmodel predictive control of energy systems. This systemuses multiple agents where each agents optimizes a subsystem.A central instance coordinates the individual agents and takescare of feasibility of the combination of the single solutions. Theadvantages of this approach are increased maintainability andprivacy for the individual agents, thus increasing applicabilityto real-world systems where often multiple parties are involvedin a single energy system. Where adequate, the agents performMPC to control their subsystems. The system and method can bechosen for each agent individually. In order to build this systema framework is developed as existing frameworks lack one ormore required features for the overall system. A small exampleis presented together with first results.

The integration of waste heat into district heating offersthe potential to decrease the environmental impactof the district heating's energy supply. A signi-cant amount of waste heat is available at low temperatures,compared to existing district heating networks.In this paper, we generate a simulation model of a districtheating network from a database and evaluatethe integration of waste heat compared to the originaldesign. Our simulation demonstrates the feasibility ofintegrating low temperature waste heat into an existingnetwork. The waste heat utilization can decreasethe primary energy consumption and CO2 emissionsfor the respective buildings. These results can beimproved further by optimizing the low-temperaturenetwork connection of each building.

One of the most important aspects during the licensing procedure of nuclear facilities is the release of radioactive isotopes. The transport from the origin to the environment is called release chain. In the scope of this work, the spatially distributed fission product release from both spherical and prismatic fuel elements, the transport with the coolant as well as the deposition on reactor internals are simulated in detail. The fission product release codes which were developed at Forschungszentrum Jülich are analyzed, shortcomings are identified and resolved. On this basis, a consistent simulation module, named STACY, was developed, which contains all capabilities of the stand-alone codes and at the same time exceeds the methodology towards new aspects. The physics models were extended, for example to take the radial temperature profile within the fuel element and the realistic time-depending nuclide inventory into account. A central part of this work is the automated treatment of the release behavior of a representative number of fuel elements. This allows for a spatially resolved release calculation, where an individual release rate is calculated for each space region. The coupling with the depletion code Topological Nuclide Transmutation (TNT) allows for conducting an individual depletion calculation for each considered fuel element. It is shown, that the released inventory is representative for a certain number of fuel elements. By using this model, the fission product release is being studied for a reference plant (HTR-Modul). Both the releases from the equilibrium core as well as the release during a core heat-up after a fast depressurization accident are being studied. In comparison to former studies, the cumulative release of long-lived nuclides during the core heat-up phase is lower and the release of short-lived nuclides is about two times higher. The release calculation can also be conducted for prismatic fuel elements (e.g. those of the Japanese HTTR). In this case, for each fuel element the depletion and release behavior of a representative compact is being determined. Furthermore, a new pebble flow model Software for Handling Universal Fuel Elements (SHUFLE) has been developed, which allows for modeling the pebble flow more in detail within the framework of a multi-physics code package. The model describes the movement of smaller fuel element clusters as a sequence of seepage processes. With the help of experimental data, it is demonstrated that the model can depict the pebble fuel in detail.

Los reactores nucleares de alta temperatura refrigerados por gas (HTR) forman una de las ramas en desarrollo para la construcción de los reactores de III+ y IV generación. Se caracterizan por obtener elevados rendimientos eléctricos y la posibilidad de obtener calor de proceso a muy alta temperatura además de una mayor seguridad intrínseca. En el pasado estuvieron operativos varios modelos en Alemania, Reino Unido y EE.UU. los cuales mostraron su viabilidad técnica. Existen diversos proyectos de desarrollo y construcción a nivel mundial y actualmente esta operativo un reactor de pruebas en China de 10MWe. Uno de los conceptos en estudio avanzado es el de lecho fluido, en el cual, la vasija del reactor es similar a un silo de almacenamiento. Dicha vasija esta rellena de esferas de 6cm de diámetro las cuales forman una matriz de grafito refractario. Dentro de las mismas se encuentra embebido el material radiactivo que actúa como combustible en las reacciones nucleares. Para el desarrollo de los nuevos diseños de reactores es preciso conocer el comportamiento de las esferas en el lecho fluidizado así como su movimiento, ya que la carga de combustible nuclear depende del tiempo que tardan las esferas en abandonar la vasija. La gravedad es la fuerza impulsora de dichas esferas, las cuales caen a ritmo controlado mediante un dispositivo de expulsión. Por lo tanto, es preciso conocer con precisión la distribución de tiempos de residencia, así como los perfiles de velocidad y las lineas de corriente. Dado que este comportamiento esta orientado a la etapa de diseño del reactor, se requiere también, que los cálculos sean realizados en el menor tiempo posible y que se fijen unos parámetros que doten de flexibilidad al modelo de cálculo así como de un cierto margen de calibración para el estudio de diferentes diseños. Es posible realizar dicha tarea a través de métodos de computación de sistemas mecánicos, sin embargo, no cumplen los requerimientos de tiempo y flexibilidad, además, suman complejidad y coste. Por lo tanto, y siguiendo una serie de trabajos realizados en el pasado, se contempla como opción mas viable, el desarrollo de un modelo basado en fluidodinámica computacional (CFD) que ya se mostraron eficaces en el pasado. Para realizar dicha tarea, es necesaria primeramente una labor de investigación acerca de los fenómenos de fluido granular, fluidos viscosos, fuerzas de fricción, propiedades de los materiales, características geométricas, así como de los diferentes métodos de cálculo ya realizados. Con todo ello, se pretende acoplar las variables de ambos sistemas y adaptarlas para que sea posible obtener una solución realista y con cierto nivel de precisión. Posteriormente, el modelo ha de ser calibrado y validado con una serie de experimentos realizados. Finalmente se han de calibrar las diferentes variables para poder continuar con los trabajos en el futuro. Con todo lo anterior, se pretende obtener un modelo de comportamiento que pueda ser utilizado en los programas que se comercializan actualmente.