Energy optimization of a solar house using model predictive control for an integrated air-source heat pump water heater and radiant floor heating system
This paper presents the application of a model predictive control strategy on an integrated thermal-energy system of a solar house with an air-source heat pump water heater (ASHPWH) connected to floor heating system, to minimize energy consumption while maintaining thermally acceptable indoor conditions in a cold climate. To prevent overheating and enhance overall energy efficiency, the integrated system utilizes preheated air from solarium as an air source for the ASHP and stores the heat for later use through a radiant floor heating system (RFHS). The cooled air from the ASHP evaporator is recirculated to another room for cooling, instead of exhausting it outdoors. A nonlinear model predictive control (NMPC) algorithm was developed for the nonlinear multi-objective optimization problem based on weather forecasts and predefined constraints during a limited prediction time horizon. A case study was conducted in two identical Test Cells at the Future Buildings Laboratory at Concordia University in Montreal, Canada, where one test cell simulated the solarium, where the indoor air temperature was permitted to exceed 28?, and the other test cell was the climate-controlled zone. A low-order thermal network model was developed and calibrated using experimental data collected from March to May 2025. The energy performance of the NMPC was compared with two control strategies: rule-based control and a daytime charging control strategy. By coordinating the operation of the integrated energy system properly, NMPC reduced total daily energy consumption by 87.9% compared to the rule-based control strategy. Moreover, it maintained thermally comfortable conditions for 83.1% of the day on March 23rd, whereas rule-based control achieved 71.7% over the same period. Consequently, this research demonstrates that NMPC provides an effective control approach for the solar-driven ASHPWH-RFHS system, maintaining thermally acceptable indoor conditions and significantly enhancing energy efficiency in solar buildings.