Smart grid energy flexible buildings through the use of heat pumps and building thermal mass as energy storage in the Belgian context

The management of electricity grids requires the supply and demand of electricity to be in balance at any point in time. To this end, electricity suppliers have to nominate their electricity bids on the day-ahead electricity market so that the forecast supply and demand are in balance. One way to reduce the cost of electricity supply is to minimize the procurement costs of electricity by shifting flexible loads from peak to off-peak hours. This can be done by offering consumers time-of-use variable electricity tariffs as an incentive to shift their demand. This study provides typologies of smart grid energy ready buildings within the context of the Belgian residential building stock and the Belgian day-ahead electricity market. Typical new residential buildings are considered, equipped with air-to-water heat pumps that supply either radiators or a floor heating system. Five heating control strategies are compared in terms of thermal comfort, energy use, cost, and flexibility. Flexibility is quantified in terms of load volumes shifted and in terms of procurement costs avoided. The first three are rule-based control strategies, whereas the last two are a smart grid-oriented optimal predictive control strategy responding to a time-varying electricity price profile. The results show that the smart grid control strategies allow reduction of procurement costs by up to 15% and the consumer's cost by 13%. The flexibility, defined in terms of loads volume shifted, is increased by 3% to 14% with the same thermal comfort. The impact of building insulation level and thermal mass is also evaluated. The flexibility for load shifting is higher when shifting from a low-energy (average U-value of 0.458 W/m2K) to a very-low-energy house (average U-value of 0.152 W/m2K).