Bachelor's thesis Pascal Block

 

Development and implementation of a dynamic control approach for thermal storages in residential buildings

Schematics of the implemented control approach in Dymola/ Modelica Copyright: EBC Schematics of the implemented control approach in Dymola/ Modelica

With the growing share of renewable non-dispatchable energy generation, the challenge of matching electricity production and consumption arises. Residential and commercial buildings, which are accountable for up to 30 percent of Germany’s end energy consumption, could therefore provide flexibility to balance the fluctuating electricity supply. In particular thermal energy storages within residential buildings could be a future option to store excess electric energy from renewable energy generation.

In this work a dynamic control approach for sensible heat storage in residential buildings was developed. Depending on an availability signal of excess electricity generation from renewable energy sources (RES), a heat pump is used to transform the excess electricity into thermal energy, which is then stored within the structural thermal mass of a building and/or a hot water storage tank. To use the storage capacity of a buildings thermal mass and to maximize the amount of stored thermal energy, the room temperatures are raised to limits without compromising thermal comfort of residents. In a first step, comfort conditions and threshold values (i.e. constraints) for the dynamic control approach were defined. Based on those constraints a rule-based control algorithm was implemented.

The performance of the dynamic control approach was then tested with dynamic building simulations and compared with a simple night setup controller. Although the total energy consumption increased due to higher room temperatures and related higher heat losses, we could store and recover a considerable amount of energy within the structural thermal mass of a building. Furthermore, we could raise the ratio of renewable energy at the total electric energy consumption of a building in comparison to the night setup controller. For a well-insulated building, we could cover 86 percent of the consumed electric energy with excess electricity generated from renewable energy sources. In this case, we used around 46 percent more excess renewable electric energy as compared to the basis night setup controller with 40 percent utilization. However, thermal energy storage within the structural thermal mass of a building and within a buffer tank is only profitable when the electricity price for renewable energy is correspondingly low and when their ratio at the consumption is sufficiently high. Otherwise, the energy costs would rise due to the additional consumption. Thus, a future implementation of real-time pricing in combination with smart meter devices will be necessary to achieve potential cost savings.