Which two types of thermal storage are commonly used?

• A. Pipe and coil.
• B. Liquid and gas.
• C. Tank and cell.
• D. Battery and capacitor.

Answer: (C)

Two common forms of thermal storage are tank-based sensible storage and cell-based latent storage. In sensible storage, heat is stored by raising the temperature of a liquid, typically water, inside a tank; energy is stored as sensible heat and retrieved by cooling or heating the liquid. In latent storage, heat is stored in phase-change materials that absorb or release energy as they change between solid and liquid (or other phases); these materials are often packaged in modular cells, which lets designers scale capacity and maintain a stable temperature during storage and release. These two approaches cover the main ways thermal energy is stored: straightforward, cost-effective storage with tanks, and higher-density storage with phase-change materials in cells.

Pipes and coils are components for moving heat, not storage. Liquids and gases describe states of matter, not storage methods. Batteries and capacitors store electrical energy, not thermal energy.