How Does Molten Salt Storage Work?
Molten salts are a heat storage solution with a great potential to help enable the manufacturing industry to transition to carbon neutrality.
The demand for molten salt storage is expected to grow at a compound annual growth rate (CAGR) of 9.4% in 2024, reaching 8.6 billion USD in the same year.
Thermal energy companies are especially interested in molten salts for their applications in the renewable energy industry. However, molten salt applications can extend beyond this industry!
Heat storage materials have limited capacities, which makes thermal heat storage one of the biggest challenges in the renewable energy industry. Efficiency depends on a properly designed system to ensure energy extraction at a constant temperature.
Molten salts are one of the upcoming technologies that will help thermal energy companies succeed.
In this article, you will learn:
- What molten salt storage is,
- How molten salt storage works, and
- The pros and cons of this technology.
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What is molten salt storage?
Molten salt storage uses molten salts as a heat storage medium. This promising technology addresses the challenge of an energy storage that is safe, consistent, and sustainable for several manufacturing processes.
Currently, this technology is primarily used with concentrated solar power (CSP) plants, but it has potential applications in other forms of renewable energy and industrial processes. Molten salt storage can:
- Enhance the efficiency and reliability of CSP plants by allowing them to generate electricity even when it’s not sunny.
- Increase grid stability with a consistent power output.
- Integrate hybrid systems with other renewable energy technologies (solar PV, wind) and energy storage systems (batteries) to maximise energy availability.
- Serve as a backup power source for critical infrastructure, providing energy during periods of high demand.
- Provide a consistent and safe heat transfer for tire pyrolysis.
With plenty of business opportunities available for this technology, it’s essential to understand how molten salt storage works, which will prompt even more research and development.
How does molten salt storage work?
Molten salts, typically a mixture of sodium nitrate and potassium nitrate, have a high heat capacity and thermal stability. They remain liquid even at high temperatures (between 220°C and 560°C), making them excellent for storing and transferring heat.
In CSP plants, molten salt storage works in the following steps:
- Mirrors concentrate solar radiation onto a receiver.
- Molten salts absorb heat from the receiver.
- The heated molten salt is stored in insulated tanks.
- When electricity is needed, the hot molten salt is pumped to a conventional steam generator.
- The steam drives turbines to generate electricity.
Molten salts can store up to 600ºC of heat for extended periods of time, addressing one of the main concerns regarding CSP plants: heat storage. However, despite its many impressive benefits, molten salt storage has some disadvantages.
What are the pros and cons of molten salt storage?
Molten salt storage is a promising technology with significant benefits, particularly in large-scale and high-temperature applications.
- Molten salts have a high heat capacity, allowing for efficient heat storage and thermal energy transfer of around 90%.
- Molten salt storage systems can be scaled up for large operations and are suitable for utility-scale applications like CSP plants.
- Molten salts can store energy for several hours to days, increasing the reliability of CSP plants even when it’s not sunny.
- The materials used to make molten salts (sodium nitrate and potassium nitrate) are inexpensive and commercially available.
- Molten salts are stable at high temperatures, typically from 220°C to 550°C.
- Molten salt storage systems can have a long operational life with proper maintenance, often exceeding 20-30 years.
Despite the benefits of molten salt storage, there are some drawbacks to this technology.
- The upfront costs for setting up molten salt storage systems, including infrastructure and installation, can be high. This can be a barrier in smaller applications or regions with limited financial resources.
- Molten salts can be corrosive to certain materials, necessitating specialised, often more expensive, materials for containment and heat exchange. Molten salt systems require regular maintenance and monitoring to prevent and manage corrosion-related issues.
- Handling and storing large quantities of molten salts pose safety risks, including the potential for leaks and burns.
- The optimal use of molten salt storage is typically in regions with high levels of solar radiation, limiting its applicability in less sunny areas.
- Despite molten salt storage’s high efficiency, some energy is still lost during conversion from thermal to electrical energy, which can affect overall system efficiency.
The advantages and disadvantages of molten salt storage influence its adoption and effectiveness in different applications. As technology advances and more teams invest in R&D surrounding molten salts, these drawbacks could be mitigated, making molten salt storage more attractive for several industries.
Molten salts at Contec
Molten®, Contec’s proprietary technology, uses a commercial mix of sodium and potassium nitrate—a patented technology developed after five years of R&D efforts in close collaboration with the Warsaw University of Technology.
Contec is currently the only company that uses molten salts as a heat transfer medium in end-of-life tire pyrolysis to produce circular secondary raw materials. Molten® has helped to make Contec’s tire pyrolysis process safe, efficient, and environmentally friendly.
At Contec, we’re dedicated to advancing molten salt technology for the circular economy. We provide sustainable and circular products such as recovered Carbon Black (ConBlack®), recovered Tire Pyrolysis Oil (ConPyro®), and recovered Steel (ConWire®), applying molten salts.
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