Bachelor's thesis Thomas Schreiber


Dynamic simulation and evaluation of domestic hot water systems

In the context of a increasing consciousness of our environment and the scarcity of fossil fuels as
well as a related interest of politic, economy and overall society in energy demand decreasing in the
domestic field, this thesis is about systems of domestic hot water supply. By now domestic hot water
takes already around 10% of the energy demand in German households. Due to better insolation of
buildings this share will increase in the next few years. Constructional measures increase the insulation
factor of building envelopes and decrease the energy losses.Modern technical systems decrease
the demand of energy for the daily activities of the occupants. The Energieeinsparverordnung
(EnEV) is a law founded by the German government which was designed to decrease the primary
energy demand in the domestic field and is the core of the climate and energy politic of the federal
republic of Germany. Especially in new and renovated buildings domestic hot water takes a big part
in energy consumption. Claim of this thesis is to model and validate different domestic hot water
systems. The models are written in the object oriented programing languageModelica. Developed,
tested and simulated in the user simulation environment Dymola. The models are inspired by a
renovated existing buildings in south Germany. In this case the heat energy for the domestic hot
water of 10 households are covered by a heatpump with CO2 geothermal probe. The heat transfer
between the heat supply pipe system and the domestic water is decentralised by a heat exchanger
in each flat. Following the real scenario different variations of supply andmaximal user temperature
are distinguished. To this configurations a continuous flow heater will be added behind the heat exchanger
in each flat. This way it will be evaluated which configuration is the most economical one
and if it is worth it to add this electrical resistance to cover the rare cases of energy demand peaks.
We will take a critical view on the pros and cons of the systems and evaluate the energy saving potential.
This waywe found a energy saving potential of 36% in the our case. The losses at distribution
and storage were reduced by 9%. Furthermore we saw that the set temperature were reached much
faster what a increase in comfort causes.