18 May 2017

O.2.3.4 Flexibility offered by residential floor heating in a smart grid context: the role of heat pumps and renewable energy sources in optimization towards different objectives.

The increasing share of renewable energy sources (RES) in the electricity generation mix turns grid balancing into a real challenge due to the intermittent character of RES. Thermal energy storage (TES) can provide flexibility to shift electricity use in time and can contribute to grid balancing. Residential floor heating systems typically combined with a heat pump can be used in this context by storing thermal energy within the floor. This paper assesses the flexibility a floor heating system can provide when controlled by a model predictive controller (MPC), through scenario analysis. MPC formulations with different objectives, such as maximising the renewable energy fraction in provided electricity, are compared. The scenario analysis includes two nearly zero-energy buildings (NZEB) and also compares an air-water heat pump with an electric resistance heater. Besides the current RES share, which amounts to about 12% of total electricity production in Belgium, a few future scenarios assuming a share of 40% RES are analysed as well. The results show that a maximisation of RES is only beneficial in the future scenario, otherwise the increase in energy use is too high to be interesting. Moreover, a more realistic primary energy factor (PEF) between 2.1 and 2.25 is determined for the Belgian context. The PEF is used in energy efficiency calculations of buildings and is currently assumed to be 2.5 in Europe.