Power control of latent heat thermal energy storage units using a model-based predictive strategy

Latent heat thermal energy storage (LHTES) is used in buildings to enhance building energy flexibility, such as peak load clipping or flexible load shaping. In previous practice, the charging and discharging of LHTES units is always performed according to a predefined schedule, whether fully charged or fully discharged during a given period, lacking accurate control of their charging and discharging rates or power control. As accurate power control becomes important for unlocking building energy flexibility when thermal storage becomes an active player in balancing thermal supply and load demand, this paper explores the issue of power control of LHTES units, aiming to develop an efficient method to control LHTES units to track a desired reference of charging or discharging rates. Several challenging issues are addressed, including modelling and controlling subject to LHTES units nonlinear thermal-hydraulic dynamics and non-uniform temperature distribution. Case studies were carried out to demonstrate the effectiveness of the proposed power control strategy, which showed that with the assistance of a Kalman filter-based state observer, the proposed strategy could successfully control the charging and discharging process of LHTES units to track predefined charging or discharging power profiles.