Session 7B - Energy (1)

Title:	A Modular Model of Reversible Heat Pumps and Chillers for System Applications
Authors:	Fabian Wüllhorst, David Jansen, Philipp Mehrfeld and Dirk Müller
Abstract:	Vapour compression machines such as heat pumps and chillers are vital for achieving climate goals. Efficiency of both depend mostly on system integration. In order to simulate coupled energy systems, fast and stable simulation models are required. Hence, we implement an open-source model for reversible vapour compression machines. The black-box based refrigeration cycle is replaceable, additional inertia and losses are optional. Furthermore, we model relevant safety controls of vapour compression machines. To show validity of the presented approach, we first calibrate two different black-box models onto measured heat pump data. The table-based model fits both measured temperature and power with minimal calibration effort. Second, we show influences of different model options onto coupled building performance simulations. Computation time increases up to 50 % when enabling all model options. Simultaneously, seasonal efficiency decreases by up to 23 % when modeling all safety controls.
Keywords:	Heat Pump, Chiller, Modular Model
Paper:	full paper / library
Bibtex:	@InProceedings{modelica.org:Wullhorst:2021, title = "{A Modular Model of Reversible Heat Pumps and Chillers for System Applications}", author = {Fabian W\"ullhorst and David Jansen and Philipp Mehrfeld and Dirk M\"uller}, pages = {561--568}, doi = {10.3384/ecp21181561}, booktitle = {Proceedings of the 14th International Modelica Conference}, location = {Link\"oping, Sweden}, editor = {Martin Sj\"olund and Lena Buffoni and Adrian Pop and Lennart Ochel}, isbn = {978-91-7929-027-6}, issn = {1650-3740}, month = sep, series = {Link\"oping Electronic Conference Proceedings}, number = {181}, publisher = {Modelica Association and Link\"oping University Electronic Press}, year = {2021} }

Title:	Modelica Modeling and Simulation for a Micro Gas-Cooled Reactor
Authors:	Huimin Zhang, Erhui Chen, Yangyang Liang, Li Wang, Jun Wang, Shuhong Du, Liping Chen, Fanli Zhou, Ji Ding and Haiming Zhang
Abstract:	Samll size and highly integral micro nuclear reactors which have broad energy advantages in the application of ocean, land, space, and sky, become a hot research topic in the international nuclear industry recently. Compared with a large-scale pressurized water reactor nuclear plant composed of a large amount of subsystems, the integral micro nuclear reactor has fewer subsystems but its subsystems are tightly coupled due to the constraints of the volume and weight. To handle the complexity aroused from this coupling issue and to better predict the reactor dynamic behavior, it is necessary to perform the system simulation across multiple disciplines and domains. In this paper, Modelica language was used in the system modeling and simulation of a micro gas-cooled reactor. The Modelica model was self-developed by China Nuclear Power Engineering Company and the MWorks developed by Suzhou TongYuan was chosen as the simulation platform. Two simulations of a conceptual micro gas-cooled reactor design were carried out, including an extreme accident scenario and a normal load-following operation scenario. The simulation results showed that the reactor has good inherent safety even under the extreme accident, in which the reactor shutdown can be achieved only by the negative reactivity result from the increase of core temperature and the fuels were not damaged since the decay heat was removed by passive air cooling from outside of the reactor pressure vessel. The reactor also has good load-following performance, which can be achieved by simply adjusting the helium inventory (or pressure) and the control rod position, while the core temperature and power generation efficiency kept constant.
Keywords:	system modeling, system simulation, micro-nuclear reactor, load-following
Paper:	full paper
Bibtex:	@InProceedings{modelica.org:Zhang:2021, title = "{Modelica Modeling and Simulation for a Micro Gas-Cooled Reactor}", author = {Huimin Zhang and Erhui Chen and Yangyang Liang and Li Wang and Jun Wang and Shuhong Du and Liping Chen and Fanli Zhou and Ji Ding and Haiming Zhang}, pages = {569--575}, doi = {10.3384/ecp21181569}, booktitle = {Proceedings of the 14th International Modelica Conference}, location = {Link\"oping, Sweden}, editor = {Martin Sj\"olund and Lena Buffoni and Adrian Pop and Lennart Ochel}, isbn = {978-91-7929-027-6}, issn = {1650-3740}, month = sep, series = {Link\"oping Electronic Conference Proceedings}, number = {181}, publisher = {Modelica Association and Link\"oping University Electronic Press}, year = {2021} }

Title:	Energy-based Method to Simplify Complex Multi-Energy Modelica Models
Authors:	Joy El Feghali, Guillaume Sandou, Hervé Guéguen, Pierre Haessig and Damien Faille
Abstract:	Energy production and consumption systems increasingly require more flexibility. The design of new control solutions can be a step, among others, towards flexibility. However, these control solutions often rely on the use of complex models, which are difficult to both manipulate and simulate. This paper presents a solution to reduce the complexity of multi-energy models modeled with Modelica language. This complexity-reducing solution is based on simplifying the model's components that contribute less to the total energy using an energy-based ranking technique. The solution is successfully applied to a complex city district model. A property of the Modelica language further allows replacing low-ranked components without being compelled to fully redesign the model. Criteria verifying the multi-energy reduced model's precision, while respecting physical constraints, are also introduced.
Keywords:	energy-based ranking, model reduction, multi-energy systems, Modelica
Paper:	full paper
Bibtex:	@InProceedings{modelica.org:Feghali:2021, title = "{Energy-based Method to Simplify Complex Multi-Energy Modelica Models}", author = {Joy El Feghali and Guillaume Sandou and Herv\'e Gu\'eguen and Pierre Haessig and Damien Faille}, pages = {577--585}, doi = {10.3384/ecp21181577}, booktitle = {Proceedings of the 14th International Modelica Conference}, location = {Link\"oping, Sweden}, editor = {Martin Sj\"olund and Lena Buffoni and Adrian Pop and Lennart Ochel}, isbn = {978-91-7929-027-6}, issn = {1650-3740}, month = sep, series = {Link\"oping Electronic Conference Proceedings}, number = {181}, publisher = {Modelica Association and Link\"oping University Electronic Press}, year = {2021} }

Title:	A Case Study on Condenser Water Supply Temperature Optimization with a District Cooling Plant
Authors:	Kathryn Hinkelman, Jing Wang, Chengliang Fan, Wangda Zuo, Antoine Gautier, Michael Wetter and Nicholas Long
Abstract:	District cooling (DC) continues to proliferate due to increasing global cooling demands and economies of scale benefits; however, most district-scale modeling has focused on heating, and to the best of our knowledge, researchers have yet to model cooling plants featuring waterside economizers in DC settings. With the popular Modelica Buildings library expanding its capabilities to district scale, this study is one of the first to demonstrate how the open-source models can be used for detailed energy and control analysis of a DC plant. For a real-world case study, we developed and calibrated high-fidelity models for a DC system central plant at a college campus in Colorado, USA, and we optimized the condenser water supply temperature (CWST) setpoint for a DC plant across multiple time horizons using the Optimization library in Dymola. Results indicate that annual CWST optimization saves 4.7% annual plant energy, with less than 1% of additional energy savings gained through daily optimization. This confirms previous studies' findings that high frequency CWST optimizations are not necessary for the studied system.
Keywords:	District Cooling, Optimization, Chiller Plant, Waterside Economizer, Modelica Buildings Library
Paper:	full paper
Bibtex:	@InProceedings{modelica.org:Hinkelman:2021, title = "{A Case Study on Condenser Water Supply Temperature Optimization with a District Cooling Plant}", author = {Kathryn Hinkelman and Jing Wang and Chengliang Fan and Wangda Zuo and Antoine Gautier and Michael Wetter and Nicholas Long}, pages = {587--595}, doi = {10.3384/ecp21181587}, booktitle = {Proceedings of the 14th International Modelica Conference}, location = {Link\"oping, Sweden}, editor = {Martin Sj\"olund and Lena Buffoni and Adrian Pop and Lennart Ochel}, isbn = {978-91-7929-027-6}, issn = {1650-3740}, month = sep, series = {Link\"oping Electronic Conference Proceedings}, number = {181}, publisher = {Modelica Association and Link\"oping University Electronic Press}, year = {2021} }

Title:	Long Term Technical and Economic Evaluation of Hydrogen Storage Technologies for Energy Autarkic Residential Complexes
Authors:	Lucas Schindhelm, Ales Vojacek and Johannes Brunnemann
Abstract:	We present an assessment of different types of hydrogen storages used as long term energy buffers for a local community complex of households in terms of economics and energy autarky. The models used in this study are partly based on the TransiEnt Modelica Library, which is being developed for the dynamic simulation of coupled energy supply systems with high shares of renewable energies. It turns out that dynamic simulations are mandatory in order to optimise the system parameters. Starting from a best case evaluation of a one year linear optimisation we develop a forecast based control logic of the whole energy system, including its physicalities. Based on our results, a storage consisting of pressurized gas bottles has proven to be the most favourite solution in terms of price and level of autarky. A liquid organic hydrogen carrier might be a competitive alternative for larger urban districts.
Keywords:	energy autarky, costs, long term, hydrogen storage, control logic, TransiEnt, linear optimisation
Paper:	full paper
Bibtex:	@InProceedings{modelica.org:Schindhelm:2021, title = "{Long Term Technical and Economic Evaluation of Hydrogen Storage Technologies for Energy Autarkic Residential Complexes}", author = {Lucas Schindhelm and Ales Vojacek and Johannes Brunnemann}, pages = {597--606}, doi = {10.3384/ecp21181597}, booktitle = {Proceedings of the 14th International Modelica Conference}, location = {Link\"oping, Sweden}, editor = {Martin Sj\"olund and Lena Buffoni and Adrian Pop and Lennart Ochel}, isbn = {978-91-7929-027-6}, issn = {1650-3740}, month = sep, series = {Link\"oping Electronic Conference Proceedings}, number = {181}, publisher = {Modelica Association and Link\"oping University Electronic Press}, year = {2021} }