A grain of SaltX-coated salt is seen under a microscope. (SaltX)

A grain of SaltX-coated salt is seen under a microscope. (SaltX)

When the salt is dry, it retains its potential heat, which is released by becoming wet. (RB)

When the salt is dry, it retains its potential heat, which is released by becoming wet. (RB)

Equipment making up a SaltX heat storage system (SaltX)

Equipment making up a SaltX heat storage system (SaltX)

A chimney billows out steam at Berlin's Reuter thermal power station where salt-based heat storage equipment is being tried out. (AP)

A chimney billows out steam at Berlin's Reuter thermal power station where salt-based heat storage equipment is being tried out. (AP)

Just Add Water

Posted: July 1, 2019

A shiny contraption stands inside a power station in Germany. Its silver pipes and barrels seem out of place in the old warehouse. The machine looks odd. But it holds ordinary stuff. What’s inside? It’s salt!

Vattenfall is an energy company in Berlin. Workers there partner with employees from a Swedish company called SaltX. They try using salt to store heat. If the system works, it could be a salty solution to some big problems.

Do you know where energy comes from? Some comes from fossil fuels such as coal and natural gas. These fuels can produce a lot of power! But they can also cause pollution, so renewable sources such as solar and wind-generated power are increasingly used. But these sources are unreliable. When it’s calm, cloudy, or at night, they produce little or no energy. Under ideal conditions, they may generate more power than is needed, with no way to store the extra.

Renewable energy is “just not constant,” says Hendrik Roeglin. He is in charge of the salt storage project. The new salt plan is simple: Use salt to store heat. Could salt become a dependable way to store energy from wind turbines and solar panels? Mr. Roeglin thinks so! He says, “In theory you wouldn’t need gas or other fossil fuel backups.”

How does the new idea work? The salt system is similar to a battery. Inside a battery, chemical energy changes into electricity. The salt system does not create or store electricity like a battery does. But it does store heat—heat that can be piped as steam into homes or businesses, or used to drive steam turbine generators to produce electricity.

The “salt battery” doesn’t use ordinary table salt. It uses the salt-like chemical calcium oxide, also called quicklime. When quicklime soaks up water there is a chemical reaction. The mixture releases a bunch of heat. This heat can be used for lots of things. When the water is taken away, the substance turns right back into quicklime.

The shiny vats in the Berlin warehouse contain treated salt that can be heated and cooled over and over again. This pilot project can store enough energy to heat 100 large houses.