Thermal Energy Storage CSP

The obvious drawback to solar energy power plants is the lack of 24hr production potential. So, when the sun goes down the plant must use stored energy to continue to release power to the grid.

A major benefit of using liquid salt is its excellent ability to hold heat. The salt melts at a very high temperature and stays in liquid form at temperatures that would vaporize other materials.

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When a power plant stores the hot salt, it is storing the heat collected from the sun to use whenever the grid requires power.

This reservoir of salt is contained in large well insulted salt storage tanks. An important part of the design of for example a tower system is to have the optimal number of heliostats and appropriately sized storage systems to hold the energy.

The design of the plants is such that during daylight there is enough heat to run the turbines at full capacity and build up a reservoir of hot salt in the storage tank.

There are many engineering challenges using salt at this high a temperature as it can be very corrosive and difficult to handle effectively. However, engineers have been able to meet the challenges involved and solar thermal power plants that can provide 24hr energy production are now practical and in many cases good value for money.

In terms of heat tracing, it is a vital component of the system as the melted salt has about the same viscosity as water and must be maintained at a very high temperature. The system is closed and there is no exhaust to the atmosphere. If a leak or cold spot should develop, the salt would “freeze” (return to solid form) almost instantly causing a huge problem on site, it is almost impossible to effectively clear frozen salt from transfer lines as the heat tracing systems are designed to maintain not raise the temperature.

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