Modeling of an ice storage buried in the ground for solar heating applications. Validations with one year of monitored data from a pilot plant

• An ice storage model coupled with the ground that surrounds it is presented.
• The ice storage design is based on heat exchangers that can be de-iced.
• The model is compared with monitored data of an ice storage of 75 m3.
• Simulated results of the main variables are in good agreement with monitored data.

A mathematical model for an ice storage buried in the ground is presented and validated with experimental results of one full operation year of a pilot plant with a 75 m3 ice storage. The ice storage was designed with heat exchangers that can be de-iced and it was developed for heating applications using a combined solar thermal and heat pump system. Because of the inherent coupling between the ice storage and the ground, a ground model was developed and coupled with the ice storage for the validation.The ice storage model is based on a transient one dimensional energy equation derived along the height of the storage with equally distributed control volumes. The ground is solved with a transient heat conduction equation with a heat source term from the ice storage. The physical ground domain is discretized in an axial-symmetrical mesh concentrated in high density gradient regions close to the ice storage. The models are solved in sequence until global convergence is achieved.The model was found to be in good agreement in terms of ice storage temperature and energy exchanged by the heat exchangers. Extracted energy from the storage was very well predicted. However, differences were found in the energy delivered by the wall heat exchangers. Ground temperatures were found to be well predicted below and above the storage, but not at the sides of the storage were over-predicted values, partially due to the simplifications assumed in this region, were observed.