Vattenfall has signed a letter of intent (LoI) with Swedish company SaltX Technology to carry out a pilot project that will use salt to store energy.

To be based on SaltX’s large-scale energy storage technology EnerStore, the project aims to discover how surplus electricity generated by windpower and solarpower plants can be stored as heat in dried salt.

Vattenfall’s SaltX project sponsor Markus Witt said: “The energy stored in salt can be kept for weeks or months until it is needed.

“By adding water to the dry salt (calcium oxide) the salt turns into calcium hydroxide. The water starts a chemical process, which generates heat and the temperature will rise to approximately 120°C. If you add hot steam instead of water to the salt, the steam temperature will rise up to 500°C.”

“The energy stored in salt can be kept for weeks or months until it is needed.”

Vattenfall’s combined heat and power (CHP) plant in Berlin, Germany, will perform the project, which will see the installation of a prototype reactor with capability to contain 1l to 3l of salt.

Witt added: “The hot steam can either be added to the Berlin district heating network or be led through a turbine to generate electric power.”

If the initial test results are positive, a full-scale, 5000m³ version will be built.

The pilot plant at Vattenfall’s site is expected to be ready by late next year and is set to undergo testing by 2019.