Energy flexibility characteristics of centralized hot water system in university dormitories

The large-scale application of renewable energy is an important strategy to achieve the goal of carbon neutrality in the building sector. Energy flexibility is essential for ensuring balance between energy demand and supply when targeting the maximum penetration rate of renewable energy during the operation of regional integrated energy systems. Revealing the energy flexibility characteristics of centralized hot water systems, which are an important source of such flexibility, is of great significance to the optimal operation of regional integrated energy systems. Hence, in this study, based on the annual real-time monitoring data, the energy flexibility of the centralized hot water system in university dormitories is evaluated from the perspective of available storage capacity (CADR), recovery time (trecovery), and storage efficiency (ηADR), by the data-driven simulation method. The factors influencing the energy flexibility of the centralized hot water system are also analyzed. Available storage capacity has a strong positive correlation with daily water consumption and a strong negative correlation with daily mean outdoor temperature. These associations indicate that increased water use on the energy flexibility of the centralized hot water system is conducive to optimal dispatching. In contrast, higher outdoor temperature is unfavorable. The hourly mean value of the available storage capacity in spring and winter is found to be around 80 kWh in the daytime, and about twice that in summer and autumn. Recovery time is evenly distributed throughout the year, while trecovery/CADR in spring and winter is about half that in summer. The storage efficiency was significantly higher in spring, summer, and winter than in autumn. The hourly mean storage efficiency was found to be about 40% in the daytime. The benefits of activating energy flexibility in spring and winter are the best, because these two seasons have higher available storage capacity and storage efficiency, while the benefit of activating energy flexibility is the highest at 6:00 a.m., and very low from midnight to 3:00 a.m.