Phase Change Energy Storage Technology
Heat and Cold storage with Phase Change (PCM) – An Innovation for Storing Thermal Energy and Temperature Control
- What is phase-change energy storage technology?
- Sensible Heat vs Latent Heat
- Phase Change Materials (PCM)
- Advantage of phase-change energy storage
- Economical and Environmental Benefits
WHAT IS PHASE-CHANGE ENERGY STORAGE?
Thermal energy storage (TES), commonly called heat and cold storage, allows the storage of heat or cold to be used later. To be able to retrieve the heat or cold after some time, the method of storage needs to be reversible. Thermal energy storage can be implemented by the storage of Sensible Heat or Latent Heat.
WHAT IS SENSIBLE HEAT STORAGE? AND WHAT IS LATENT HEAT STORAGE?
The most common way of thermal energy storage is as sensible heat. As shown in the figure, heat transferred to the storage medium leads to a temperature increase of the storage medium. Hot water storage for domestic heating & domestic hot water is a common example.
The phase change of solids and liquids by melting and solidification can store large amounts of heat or cold. Melting is characterized by a small volume change, usually less than 10%. If a container can fit the material while it’s in its liquid state, the pressure is not changed significantly. Consequently, melting and solidifying the storage material proceed at a constant temperature. Upon melting, when the heat is transferred to the storage material, the material maintains a constant temperature at the melting temperature. This is also called the phase change temperature. If the melting is completed, further transfer of heat results again in sensible heat storage. The heat supplied upon melting is called latent heat, and the process latent heat storage.
Sensible Heat vs. Latent Heat
Temperature Control During Phase-Change Energy Storage
PHASE CHANGE MATERIAL (PCM)
Inorganic PCM are engineered hydrated salt solution made from natural salts with water. The chemical composition of salts is varied in the mixture to achieve the required phase-change temperature. Special nucleating agents are added to the mixture to minimize phase-change salt separation and to minimize supercooling, that are otherwise characteristic of hydrated salt PCM. Salt Hydrates are characteristic of being non-toxic, non-flammable, and economical.
Bio-based PCM are organic materials that are naturally existing fatty acids such as vegetable oil. Based on their chemical composition, their phase-change temperature can vary. These products are non-toxic, non-corrosive, and have infinite life cycles. They however can be expensive and flammable at high temperatures.
Organic PCM are naturally existing petroleum bi-products that have a unique phase-change temperature. These products are manufactured by major petrochemical companies so their availability could be limited. They can be toxic, flammable, and expensive. They have infinite life cycles and the price varies with changes in petroleum prices globally.
ADVANTAGES OF PHASE-CHANGE ENERGY STORAGE
- Store thermal energy at the temperature of process application
- Store thermal energy as latent heat which allows higher thermal energy storage capacity per unit weight or material without any change in temperature
- Store thermal energy from a thermal energy source or electrical energy source when available and use when needed
- Stored thermal energy is portable and rechargeable
ECONOMICAL & ENVIRONMENTAL BENEFITS
- Store natural thermal energy for facility heating and cooling needs. Reduced energy demand reduces facilities carbon footprint
- Store thermal energy during off demand hours and use during peak demand to save on energy cost and help stabilize grid load
- The shift of heating and cooling load also reduces peak time stress of heating and cooling equipment that can lead to reduced operating & maintenance costs.
- This technology would lead to the sizing of HVAC equipment for average load rather than peak load