Peak-shaving investigation of a novel flexible two-stage heat pump for heating

Since buildings account for a large portion of global energy consumption and greenhouse gas emissions, several nations are expecting to install net-zero emission buildings. The governors have set a carbon–neutral objective for 2050, which requires that all new construction have net-zero emissions. As heat pumps are considered a substitution for gas boilers, in this study, a thermal energy storage system is introduced to a two-stage heat pump system in a novel configuration. The novel flexible two-stage heat pump has been studied and compared with a baseline two-stage heat pump, as well as the same flexible and baseline single-stage heat pump, in the same working conditions. A control strategy has been defined based on the heating duty, hour of the day, and storage tank status to run the system in different modes: 1- Normal operation, 2- Charging, 3- discharging, and 4- stand by modes. The weather data of Glasgow and Birmingham cities, UK have been used to acquire the variable hourly heating loads of a typical 4-story residential block via IESVE software. Also, to study the effect of heating load profile shape, a sinusoidal daily heating load profile has been created with the same maximum duty of variable load from IESVE. The results show that a flexible two-stage system shows 1.67%, and 5.31% higher seasonal COP (seasonal coefficient of performance) with real variable loads, and sinusoidal loads, respectively. While the maximum 2.1% cut price has been shown with sinusoidal loads, the price cut for the real variable loads is less than that.