Introduction

As the world accelerates toward carbon neutrality and renewable integration, long-duration energy storage has become essential for ensuring stable and reliable power supply. Among various technologies, Molten Salt Energy Storage (MSES) has proven to be one of the most promising solutions due to its safety, scalability, and cost-effectiveness.

At the heart of this system lies the Hairpin Heat Exchanger (also known as U-tube or double-pipe heat exchanger), which acts as the thermal bridge that efficiently transfers stored heat into usable steam or process energy. Together, molten salt storage and hairpin exchangers form a powerful combination for the future of clean energy.

What is Molten Salt Energy Storage?

Molten salt storage uses a mixture of nitrates—such as sodium nitrate and potassium nitrate—that remain liquid between 200 °C and 600 °C.

• Charging (heat storage): Solar concentrators or electric heaters raise the temperature of molten salt, which is stored in insulated tanks.

• Discharging (heat release): Hot molten salt flows through a heat exchanger, transferring its heat to water or another working fluid to produce steam for turbine power generation.

Advantages of molten salt storage:

1. Large-scale capacity — from MWh to GWh levels.

2. Long discharge duration — 8–12 hours or even longer.

3. High efficiency — thermal efficiency above 90%.

4. Safe and stable — non-flammable and based on abundant raw materials.

This technology has already been deployed in solar thermal power plants (CSP) in Spain, the U.S., and China, providing stable electricity even after sunset.

What is a Hairpin Heat Exchanger?

A Hairpin Heat Exchanger consists of straight tubes bent into a U-shape, resembling a hairpin. One fluid flows inside the tubes (tube side), while another flows outside (shell side), achieving efficient heat transfer.

Key features of hairpin exchangers:

• High pressure resistance — ideal for high-temperature steam and molten salt.

• Compact and modular — multiple units can be arranged in parallel for large capacity.

• Ease of maintenance — individual tubes or bundles can be replaced without full system shutdown.

• High thermal efficiency — fast tube-side velocity enhances heat transfer.

Hairpin exchangers are widely used in petrochemical, power, metallurgy, and increasingly in renewable energy storage applications.

BOOYO's Contribution to China Energy Storage Industry

At present, Shandong BOOYO Heavy Industry Technology Group is manufacturing two of the largest Hairpin Heat Exchangers in China, designed to serve molten salt energy storage projects. With years of experience in pressure vessel and heat exchanger design and ASME-certified fabrication, BOOYO has become a trusted partner for both domestic and international clients.

By focusing on advanced manufacturing, strict quality control, and global service, BOOYO is committed to supporting the rapid growth of renewable energy and long-duration storage solutions.

Why Hairpin Heat Exchangers in Molten Salt Systems?

Molten salt systems operate under extreme temperature, pressure, and corrosion conditions. Heat exchangers must ensure reliable energy transfer under these demanding environments. Hairpin exchangers are an excellent fit because they:

1. Provide robust mechanical strength at >565 °C and high steam pressure.

2. Support modular scalability, matching different plant capacities.

3. Allow long service life through corrosion-resistant materials and stress control.

4. Offer maintainability, minimizing downtime and ensuring system availability.

In short, molten salt is the “thermal warehouse,” while the hairpin heat exchanger is the “energy outlet.”

Applications and Industry Outlook

1. Solar Thermal Power Plants (CSP)
   Molten salt tanks combined with hairpin exchangers generate stable electricity at night or during cloudy conditions.

2. Industrial Waste Heat Recovery
   Capturing high-temperature exhaust heat in molten salt, later released via hairpin exchangers for process or power use.

3. Hybrid Renewable Systems
   Balancing intermittent solar and wind power, providing flexible and dispatchable energy to the grid.

With global demand for clean energy on the rise, the integration of Molten Salt Energy Storage and Hairpin Heat Exchangers is set to become a cornerstone of long-duration storage solutions worldwide.

Conclusion

Molten Salt Energy Storage provides safe, large-scale, and cost-effective long-duration storage. Hairpin Heat Exchangers ensure this stored energy is efficiently converted into usable power. Together, they form a robust solution that supports renewable integration, grid stability, and the future of sustainable energy.