What is the working principle of a thermal energy storage (TES) system?

The working principle of a Thermal Energy Storage (TES) system is to store thermal energy (either heat or cold) during off-peak hours and release it during peak hours to reduce energy costs and improve system efficiency. TES systems shift the energy demand from periods of high electricity prices to periods of low electricity prices. There are several types of TES systems, including chilled water storage, ice storage, and phase change material (PCM) storage. Chilled water storage systems store chilled water in insulated tanks during off-peak hours, typically at night. During peak hours, the stored chilled water is used to supplement or replace the output of the chiller, reducing the chiller's energy consumption. Ice storage systems store energy in the form of ice, which has a higher energy storage density than chilled water. Ice is typically made during off-peak hours using a chiller. During peak hours, the ice is melted to provide cooling. PCM storage systems use materials that change phase (e.g., solid to liquid) at a specific temperature to store and release energy. PCMs have a high latent heat of fusion, meaning they can store a large amount of energy during the phase change. For example, an ice storage system can be used to shift the cooling load from daytime to nighttime, reducing the peak electricity demand and saving money on energy costs. During the night, the chiller makes ice, storing thermal energy. During the day, when the cooling load is high, the ice is melted to provide cooling, reducing the chiller's load or even allowing it to be turned off completely.