@inproceedings{RammHammelKlaerneretal.2017, author = {Ramm, Tobias and Hammel, Carolina and Kl{\"a}rner, Michael and Kruck, Alfons and Schrag, Tobias}, title = {Energy storage and integrated energy approach for district heating systems}, volume = {2017}, booktitle = {Energy Procedia}, number = {135}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1876-6102}, doi = {https://doi.org/10.1016/j.egypro.2017.09.515}, pages = {391 -- 397}, year = {2017}, abstract = {This paper deals with the potential of using the thermal storage capacities within local district heating systems to balance the low and medium voltage grids by the use of heat pumps (HP) and combined heat and power (CHP) plants. The state-of-the-ar of district heating systems as well as the coupling of the heat and power grid is discussed. The research work of the projec NATAR (local heating grids with lowered temperature as provider of balancing power) and the local heating grid of Dollnstein which serves as an use case, are further described. A first analysis of measured data of the district heating system indicates an optimisation potential regarding to the control strategy of the combined heat and power plant as well as the usage of the available thermal storage capacities.}, language = {en} } @inproceedings{VannahmeRammEhrenwirthetal.2019, author = {Vannahme, Anna and Ramm, Tobias and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Comparison of a usual heat-transfer-station with a hydraulic modified version under the aspect of exergy saving}, booktitle = {Proceedings of the 13th International Modelica Conference}, editor = {Haumer, Anton}, publisher = {Link{\"o}ping University Electronic Press}, address = {Link{\"o}ping}, isbn = {978-91-7685-122-7}, issn = {1650-3686}, doi = {http://dx.doi.org/10.3384/ecp19157647}, pages = {647 -- 654}, year = {2019}, language = {en} } @inproceedings{SchragEhrenwirthRammetal.2020, author = {Schrag, Tobias and Ehrenwirth, Mathias and Ramm, Tobias and Vannahme, Anna and Trinkl, Christoph}, title = {Solar energy use in district heating networks}, booktitle = {ICREEC 2019: Proceedings of the 1st International Conference on Renewable Energy and Energy Conversion}, editor = {Belasri, Ahmed and Beldjilali, Sid Ahmed}, publisher = {Springer}, address = {Singapur}, isbn = {978-981-15-5443-8}, issn = {2352-2534}, doi = {https://doi.org/10.1007/978-981-15-5444-5_1}, pages = {3 -- 10}, year = {2020}, language = {en} } @inproceedings{RammEhrenwirthSchrag2019, author = {Ramm, Tobias and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Modelling of the central heating station within a district heating system with variable temperatures}, booktitle = {Proceedings of the 13th International Modelica Conference}, editor = {Haumer, Anton}, publisher = {Modelica Association and Link{\"o}ping University Electronic Press}, address = {Link{\"o}ping}, isbn = {978-91-7685-122-7}, issn = {1650-3686}, doi = {http://dx.doi.org/10.3384/ecp19157567}, pages = {567 -- 576}, year = {2019}, language = {en} } @article{WernerEhrenwirthMuschiketal.2021, author = {Werner, Melanie and Ehrenwirth, Mathias and Muschik, Sebastian and Trinkl, Christoph and Schrag, Tobias}, title = {Operational experiences with a temperature-variable district heating network for a rural community}, volume = {46}, journal = {Chemical Engineering \& Technology}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0930-7516}, doi = {https://doi.org/10.1002/ceat.202100114}, pages = {482 -- 490}, year = {2021}, abstract = {The potential of utilizing temperature-variable district heating systems in rural areas was investigated. A local district heating system in Germany and the related project NATAR are briefly described; measurement data is evaluated. Operational experiences with a seasonal temperature reduction and consequent advantages for different heat generation systems and heat storages are discussed. The analysis of measurement data reveals a high optimization potential for solar thermal systems in case of an integration both into a low- and a high-temperature storage. Furthermore, a combined heat-and-power plant in combination with a CO2 heat pump promises sector-coupling potential and high electricity self-consumption.}, language = {en} } @article{VannahmeEhrenwirthSchrag2021, author = {Vannahme, Anna and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Enhancement of a district heating substation as part of a low-investment optimization strategy for district heating systems}, volume = {10}, pages = {53}, journal = {Resources}, number = {5}, publisher = {MDPI}, address = {Basel}, issn = {2079-9276}, doi = {https://doi.org/10.3390/resources10050053}, year = {2021}, abstract = {In an ongoing project, low-investment measures for the optimization of district heating systems are analyzed. The optimization strategies are collected in a catalog, which is the core of a guideline. The application of this guideline is demonstrated using two concrete district heating networks as examples. In this study, the improvement of an analog controlled district heating substation by an electronic controller is investigated. High supply temperatures and heat losses are often a challenge in district heating networks. The district heating substations have a major influence on the network return temperatures. The comparison of the two substation setups with analog and electronic controllers is carried out by laboratory measurement. It can be shown that the return temperatures can be reduced by an average of 20 K in winter and transition, as well as 16 K in summer. The district heating network losses are calculated for one of both specific district heating networks. They are calculated from the ratio of network losses to generated energy. The generated energy is the sum of network losses and consumer demand. The thermal losses of the network can be reduced by 3\%. The volume flow in the heating network can be reduced to a quarter. Therefore, the pumping energy requirement drops sharply since these changes cubically affect the volume flow}, language = {en} } @article{VannahmeBuschEhrenwirthetal.2023, author = {Vannahme, Anna and Busch, Jonas and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Experimental Study of District Heating Substations in a Hardware-in-the-Loop Test Rig}, volume = {12}, pages = {43}, journal = {Resources}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2079-9276}, doi = {https://doi.org/10.3390/resources12040043}, year = {2023}, abstract = {This study compares two district heating substation systems for implementation in rural district heating networks with non-retrofitted single- and two-family houses. The aim is to determine which system has the potential to provide lower return temperatures and/or lower power peak demand. A hardware-in-the-loop-test rig was utilized to measure the two district heating substations under real operation conditions. This experimental study demonstrates that load balancing of the district heating network is attainable with the district heating substation with storage. This is especially advantageous when there is a high demand for domestic hot water. Overall, both systems yield comparable return temperatures.}, language = {en} } @article{VannahmeEhrenwirthSchrag2024, author = {Vannahme, Anna and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Development and application of a guideline for assessing optimization potentials for district heating systems}, volume = {2024}, pages = {131226}, journal = {Energy}, number = {297}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-6785}, doi = {https://doi.org/10.1016/j.energy.2024.131226}, year = {2024}, abstract = {Integrating renewable energies into district heating systems has a large potential to reduce CO2-emissions in the heating sector. As district heating systems offer the possibility of incorporating renewable energies into the heat supply, new systems have to be built and the existing networks must be maintained. This study investigates ways to optimize existing district heating systems in order to ensure economic sustainability in the long-term. Previous case studies have elaborated on a variety of optimization measures. However, to date, these measures have neither been collected nor consistently assessed for a wider application range. Therefore, in the study presented here a system for assessing the ecological and economic benefits of optimization measures was developed and applied. The assessment method utilized showed that optimization of district heating consumer substations and adding of a central buffer storage tank has a high optimization potential in comparison to intermittent operation strategy, which has a significantly lower optimization potential. From this information and the transferability data, a district heating operator can determine which optimization measure should be prioritized, which is shown at the end of the paper on an example case.}, language = {en} } @article{SlonskiSchrag2019, author = {Slonski, Matthias and Schrag, Tobias}, title = {Linear optimisation of a settlement towards the energy-plus house standard}, volume = {12}, pages = {210}, journal = {Energies}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en12020210}, year = {2019}, abstract = {Future buildings will use technologies that are either well-known, innovative, or a combination thereof in order to be environmentally friendly and feasible at the same time. To evaluate and compare such systems through simulation, adaptive tools need to be available. This paper describes a conceived method for planning quarters and settlements. The novelty of this work emerges from the combination of a building simulation with a linear economic optimisation of the energy system, to achieve the energy-plus house standard for a settlement. Furthermore, the tools applied are adaptive or open source. In this article, a hypothetical basic example is given for a predefined idealised settlement, which consists of 132 single-family houses of one building type. The hourly demand for electrical energy and heat is established for three energy-efficiency classes for the building type with a dynamic simulation in MATLAB/SIMULINK using the CARNOT toolbox. This toolbox is also used to calculate the specific electrical energy production by photovoltaics. The components for the energy system of the settlement are implemented in the open source linear optimisation tool URBS. An economic optimum for the energy system of the settlement is found for each of the energy efficiency classes for an accumulated energy demand of the buildings. In this way, a lossless energy hub between the buildings is assumed. The results of the conducted simulations indicate that the optimal ratio of air/water to ground/water heat pumps shifts towards air/water heat pumps with more energy efficient houses. This is due to the lower specific investment costs, which outweigh the operational costs when less energy is required. The lowest costs for the entire energy system are for the one with the most energy efficient settlement. This is the case, as the costs for the higher energy standard of the buildings are not considered in the calculations. The behaviour of the optimisation is tested and discussed through a sensitivity analysis for one efficiency class. By presenting this simple, comprehensible example, an impression of the possible applications for this methodology is conveyed.}, language = {en} } @article{WernerMuschikEhrenwirthetal.2022, author = {Werner, Melanie and Muschik, Sebastian and Ehrenwirth, Mathias and Trinkl, Christoph and Schrag, Tobias}, title = {Sector Coupling Potential of A District Heating Network by Consideration of Residual Load and CO2 Emissions}, volume = {15}, pages = {6281}, journal = {Energies}, number = {17}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en15176281}, year = {2022}, abstract = {The growing share of fluctuating renewable electricity production within the German energy system causes the increasing necessity for flexible consumers, producers, and storage technologies to balance supply and demand. District heating networks with combined heat and power units, Power-to-Heat applications, and thermal energy storage capacities can serve as one of these flexible options. In this context, a simulation model of the district heating network of the rural community Dollnstein, Germany, was built. With the residual load of different regional areas (Germany, Bavaria, Eichst{\"a}tt, Dollnstein) it is investigated, how the heat generators can operate in an electricity market beneficial way. Two different control algorithms were evaluated: Due to a correlation between the residual loads and the CO2 emissions of the electricity mix, the CO2 savings achieved by this control algorithm are determined. Another way to operate electricity market beneficial is to consider the current CO2 emissions of each region. The main outcomes of this paper are, that there is a high potential for sector coupling by shifting the operation times of a CHP and a heat pump according to the residual load. The electricity demand of the heat pump can be met in terms of low CO2 emissions of the electricity mix, while the CHP can replace electricity with high CO2 emissions. These results can be improved, by considering not the residual load but the current CO2 emissions in the control algorithm.}, language = {en} } @article{HaslerHuberLeindeckeretal.2013, author = {Hasler, Ewald and Huber, Christian and Leindecker, Herbert C. and Schrag, Tobias and Stocker, Emanuel and Wartha, Christian}, title = {Bewertung unterschiedlicher Fassadenkonstruktionen unter Lebenszyklusaspekten mit einer Fallstudie B{\"u}rogeb{\"a}ude}, volume = {35}, journal = {Bauphysik}, number = {4}, publisher = {Ernst \& Sohn}, address = {Berlin}, issn = {1437-0980}, doi = {https://doi.org/10.1002/bapi.201310072}, pages = {250 -- 256}, year = {2013}, language = {de} }