Master's Thesis Tobias Blacha

 

Analysis of the usage of electric powered supply systems for integration of renewable energy in smart buildings

The transition of energy generation from mostly fossil to renewable energy sources is a great challenge
for the electricity distribution networks. Due to the volatile characteristic of the renewable
generation, the energy input cannot be controlled as easily as in the past. In order to stabilise the
national electricity grid, the integration of flexible electricity consumers and energy storages is required.
About 40% of the German final energy consumption is accounted of buildings. This results
in a great potential for utilisation of inertia and storage capacties in buildings in order to balance
the electric grid load. This potential can be leveraged through the application of electrical heating
systems. Moreover a sinking primary energy factor and the legal obligation towards better building
insulation increases the attractiveness of electrical heating systems. In the light of these circumstances
this work investigates various electrical heating systems through dynamic building simulation.
In the first part of this work the modelling approach chosen for thermal building simulation as well
as the electrical heating system models are described, focusing on the description of heat transport
processes. In the second part simulation results for direct and indirect electrical heating systems are
presented and discussed for several scenarios. Thereby the heating systems’ dynamic behaviour, the
influence of improved building insulation and the integration potential of renewable energy sources
in combination with load shifting is investigated. The simulations are carried out in the modelling
and simulation environment Dymola /Modelica by using a complex physical building model.
Heating systems that emit heat directly are in general only suited for short-term shiftig of heat generation.
Therein, purely convective heating systems are characterised by the lowest potential for
load shifting. These systems only allow for an interruption of heating operation of about an hour.
Additionally 12-14% of the shifted heat load is lost due to ventilation and heat conduction. In contrast
to that, systems that heat mainly by radition allow for an interruption of more than five hours.
Hereby the room air temperature increases just slightly and thus only 8-9% of the shifted heat load
is lost. Load shifting results for all direct heating systems in a higher room temperature for a short
period of time, which might in some case lower the resident’s comfort.
Heating systems, which are integrated in the building mass allow for load shifting of up to several
days. This results in an increased roomtemperatures, which then might also influence the resident’s
comfort. Due to the mostly radiative heat transfer only 11% of the shifted heat load is lost because
of ventilation and transmission.
The conducted examinations show that electrical heating systems are applicable in various ways.
Heating systems which are operated with heat pumps are especially suitable for modern existing buildings as well as for refurbished buildings. This suitability can be accounted to the very efficient
supply of heat and to their relatively low heat demand. For extensively insulated buildings such as
passive houses, which are characterised by an extremely low heat demand, combinations of direct
electrical systems that enable heating without hydraulic installations are more suitable.