Molten salt as a solar transfer fluid

Working with salt?

An Italian solar plant believes it has found a way to boost efficiency and output for solar power sites; using molten salt as a transfer fluid.

Traditionally an oil called therminol is used to transfer heat collected by parabolic mirrors to the boilers for making steam, but Italian power firm Enel believes salt might be a better alternative.

Salt is generally used at solar sites to store excess heat, but Enel has discovered that by deploying salt as the heat transfer mechanism inside the pipes of parabolic solar thermal parks as well as a storage medium, the efficiency of solar thermal power plants could inch up incrementally, because molten salt retains heat longer than therminol.

As a result, more heat would be harnessed from the mirrors increasing their output, boosting parabolic solar technology, which is failing in the face off new initiatives such as heliostats.

The only drawback to using salt instead of therminol is that it clumps together and piles up, causing problems for the systems.

More heat, more power

Speaking to Green Tech Media, Frank Gilhooly, Director of Global Sales and Marketing for the Power Business Unit of Tyco Flow Control said: "The challenge is that therminol flows rather easily. Molten salt does not, because it sets up. You need to keep it hot enough to keep it flowing."

Tyco has been working on a series of systems to work with molten salt and if it is a success, could be implemented in the massive Desertec Project set to be built in the Sahara Desert.

For now though, molten salt is being trialled at the 5-megawatt Archimede plant in Italy. The site consists of 30,000 square meters of parabolic mirrors and 5400 meters of piping. The molten salt is heated to 550 Celsius, which is higher than some of the new wave solar thermal concepts.

The plant was named after Archimedes, who in the third century B.C. proposed setting ships on fire by transferring solar heat with bronze shields.

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