5th Generation District Heating and Cooling (5GDHC) provides a promising pathway for decarbonising the thermal sector. To quantifying the synergies between heating, cooling, and electricity, complex thermofluid models are required. Modelica offers a potential solution for developing such models but there is a scarcity of accessible and usable models. This paper addresses this gap by presenting a comprehensive set of Modelica models for key elements of 5GDHC systems: prosumers, balancing units, and hydraulic interfaces. The models prioritise usability by facilitating the utilisation of Func-tional Mock-up Interface and Power Hardware-in-the-Loop (PHIL) methodologies. Component design, rele-vant controls and the applicability of PHIL setups are discussed. A theoretical case exemplifies hardware min-imisation, using only heat exchangers to investigate prosumer behaviour. The paper concludes with a discus-sion on the potential use of these models, opportunities for improvement, and the need for further research and experimental investigations in understanding 5GDHC systems.

Given the computationally intensive nature of heat exchanger simulators, utilizing a data-driven surrogate model for efficiently computing the heat exchanger outputs is desirable. This study focuses on developing integrated surrogate models of heat exchangers for a vapor compression system in Modelica. The surrogate models are designed to serve as steady-state equivalents based on an efficient physics-based model which was calibrated using reference data obtained from a more advanced simulation model. Subsequently, the calibrated model was employed to generate the training and testing data for the development of Gaussian Process (GP) and Multi-Layer Perceptron (MLP) surrogates. The obtained findings indicate that GPs exhibit high accuracy when applied to the heat exchanger's outputs with smooth behavior. GPs also demonstrate excellent data efficiency compared to MLPs. In cases where the GP struggles to model specific outputs effectively, MLPs are able to capture the more complex behavior. Moreover, hyperparameter optimization is employed to identify optimal MLP topologies. Finally, the fast and compact surrogate model was integrated into the Modelica/Dymola environment. This adaptation allowed the surrogate models to be directly combined with the physical model of the heat exchanger.

A generic component-based model of an industrial electrode boiler with internal control systems is presented. A mechanistic modelling approach was taken to include as much process and control information as possible and to generate detailed simulation results. The model is intended for qualitative studies of electrode boiler dynamics in the context of district heating generation and power grid ancillary services in collaboration with other electric power consuming units.

An example boiler control scheme is designed and included in the simulation model as this is paramount to the dynamic response of the system. Simulations of standstill, load changes, and startup from hot and cold state show that the strictest ancillary service requirements can be fulfilled when the boiler is kept at operating temperature.