Master's Thesis Philipp Reher


Simulation Study on Domestic Hot Water Heating Systems using Heat Pumps in Existing Apartment Buildings with Dymola/Modelica

Scheme of the System in Modelica Copyright: EBC Scheme of the System in Modelica

The energy demand for building heating is decreasing due to improved construction and insulation
standards, while the occupants are demanding more and more comfort in the area of hot water and therefore have a higher personal energy requirement. In addition, the flow temperature
in the heating circuit for domestic hot water (DHW) heating is prescribed by the corresponding hygiene requirements. Overall, the share of DHW heating in the total requirement of a building
thus increases. The consumption of hot water is associated with high energy consumption. DHW
heating in private households accounts for 4% of total energy consumption in Germany.
The hot water heat pump has become increasingly important in recent years due to the objective
of ensuring domestic hot water heating in the building sector with the lowest possible energy
consumption. Although heat pumps already supply many one- and two-family houses with low
carbon dioxide heat, their use in multi-family houses (MFH) is still rare with 16% in new buildings.
Heat pumps account for less than 5% of existing buildings. About half of the appartements in Germany are in MFHs. The aim is to secure the heat supply for drinking water and space heating in
existing buildings using sustainable technologies. Within the project "LowEx-Bestand-Analyse"
solutions for the use of electric heat pumps in energetically renovated appartement buildings are
to be comprehensively developed, analysed and demonstrated. As a result of the project, an assignment of suitable LowEx system concepts to MFH building types will be created.

The aim of this master thesis is the holistic investigation of different heat pump based hot water
systems for MFH within a simulation study. First, a research on the current state of the art of common DHW heating concepts is carried out. The legal and norm situation regarding system design and drinking water hygiene is also of importance. The overall system is mapped in Modelica/Dymola with all components (heat pump, heat exchanger, storage tanks, pipes, valves, buildings, ...). Existing component models from libraries such as buildings of the Lawrence Berkeley National Labroratory, the AixLib developed at the RWTH Aachen or the LowEx.lib compiled by the Fraunhofer ISE can be used, and if necessary modified and extended. In particular, the study focuses on the investigation of energetic aspects in compliancewith the legal requirements. Different systems will be simulated and different interpretations investigated.