Are building-energy systems valuable for flexibility markets? A techno-economic analysis under different boundary conditions

Abstract The increasing penetration of non-programmable renewable sources poses new challenges to the stability and reliability of electric power systems. Particularly, as traditional ancillary services from thermoelectric power plants are declining, new flexible actors are needed. This work investigates the potential of a residential house heated by a heat pump to offer flexibility services to the electric grid by leveraging its thermal inertia. An optimisation model is developed to schedule the heat pump operations while minimising the daily electricity costs, providing upward reserve (i.e. reducing consumption when requested) and ensuring occupants thermal comfort. The building thermal behaviour is modelled using a 7R4C network based on a thermo-electric analogy. The developed model is applied to a refurbished single-family house, equipped with an air source heat pump and radiant floor heating system, during a typical winter day. Then, five sensitivity analyses are performed to assess the impact of weather conditions, building age, heating system, electricity pricing, and heat pump type. The base case results show that offering upward reserve primarily shifts the heating consumption throughout the day without large variations in the overall energy use, preserving thermal comfort and with potential economic benefits. However, the sensitivity analyses show a reduced profitability linked to mid-season days, building with lower thermal inertia, lack of heat pump inverter control and time-varying electricity tariffs. In conclusion, results confirm that building-energy systems can provide flexibility services by leveraging their thermal inertia, but economic convenience is highly context-dependent.