The types of molten salts most commonly used in concentrated solar power (CSP) plants are typically mixtures of nitrate salts, primarily sodium nitrate (NaNO3) and potassium nitrate (KNO3). This nitrate salt blend is favored because it effectively serves both as a heat transfer fluid and a thermal energy storage medium in CSP systems.
Common Molten Salt Types in CSP Plants:
- Sodium Nitrate and Potassium Nitrate Mixture:
This binary or ternary nitrate salt mixture is widely used in CSP tower plants. It has a relatively low melting point (around 131 °C for certain mixtures) and can be heated up to about 565 °C, enabling efficient heat transfer and storage for power generation. The salt mixture flows through the receiver where it is heated by concentrated sunlight, then either used immediately to produce steam for turbines or stored in insulated tanks for later use. - Ternary Nitrate Salt Mixtures:
Some CSP plants use a ternary mixture that includes sodium nitrate, potassium nitrate, and calcium nitrate, balancing melting point, stability, and heat capacity for enhanced performance.
Key Characteristics:
- These nitrate salts can be heated to temperatures typically between 150–350 °C in trough systems and up to around 565 °C in tower systems, enabling effective thermal energy storage and dispatch.
- Molten nitrate salts provide an affordable and stable medium for storing solar thermal energy that can be released on demand, allowing CSP plants to deliver electricity even when the sun is not shining.
- While nitrate salts are most common, their thermal stability limits the maximum temperature, and degradation can occur beyond certain temperatures. Research is ongoing to find alternative molten salts with higher temperature capabilities.
In summary, sodium nitrate and potassium nitrate mixtures are the most prevalent molten salts used in CSP plants today, valued for their heat transfer properties, relatively low melting points, and ability to store thermal energy efficiently for power generation.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-types-of-molten-salts-are-most-commonly-used-in-csp-plants/
