GE, KGAL bet millions on solar energy with molten-salt storage

How do you harness solar power when the sun isn’t shining? One method involves using concentrated solar power combined with molten-salt energy storage.

It’s not a widespread technology yet — there are only 10 such commercial plants in operation around the world — but it is, pardon the expression, picking up steam. (Concentrated solar power uses mirrors, rather than solar panels, to capture the sun’s energy as heat that is turned into steam to drive a generator.)

Spain was the first country to develop concentrated solar plants with molten-salt storage. And now one of those plants has become the focus of GE Energy Financial Services’ first investment in the technology.

GE and German investment firm KGAL this weeks announced they are investing €111.1 million ($158 million) in Extresol II, a 50-megawatt (MW) concentrated solar plant with molten-salt storage in Torre de Miguel Sesmero, Badajoz, Spain. Completed last December, the plant was develop by Spanish solar-thermal power developer ACS.

ACS has so far built more than €2 billion ($2.8 billion) worth of concentrated solar power facilities with molten salt storage in Spain.

Extresol II uses a system of parabolic trough mirrors to heat a thermal fluid used to boil water for steam. The plant stores additional heat by melting a special salt mixture during the day, then extracts that heat when the sun isn’t shining, to continue producing steam for the turbines.

The molten salt’s heat-storage capacity enables the plant to keep generating electricity for an extra seven hours a day after the sun stops shining. In all, the facility generates enough electricity to meet the needs of some 37,900 Spanish households.