What type of secondary cooling device functions as a thermal storage device?

The answer is the ice builder. An ice builder is designed specifically to create and store ice, which can later be used as a thermal storage medium in a cooling system. By freezing water during off-peak hours or when excess cooling capacity is available, an ice builder can accumulate ice formation that is then utilized during peak demand periods. This process helps in managing energy consumption effectively and optimizing cooling energy costs.

Chillers are primarily used to remove heat from a liquid via a vapor-compression or absorption refrigeration cycle, but they do not store thermal energy. Heat exchangers facilitate the transfer of heat between two or more fluids but are not designed for thermal storage. Cooling towers are used to dissipate heat from a system into the atmosphere and do not serve as thermal storage devices. Thus, the ice builder stands out as the only option that provides the functionality of thermal storage by leveraging ice.