Freshkills Park Blog

A Solution to Renewable Energy Storage?


Energy storage is the Holy Grail for renewable energy producers. In an ideal world, they would be able to capture that burst of wind at two in the morning and use it to power your coffee maker when you wake up at seven. A solar project in Arizona called Solana is using an innovative solution for energy storage: molten salt.

Imagine pure salt so hot it looks, and moves, like liquid water. This molten salt is the substance inside large insulated tanks that allows the Solana project to store heat for up to six hours. Most of the solar thermal energy is channeled directly to the steam generator that produces electricity, but some of the heat is diverted into heating up these molten salt tanks whose energy can be harnessed long after the sun has set from the sky.

These molten salt tanks make Solana the largest solar thermal project with energy storage in the world. Using heat to store energy is fairly new; some other solar power plants use expensive batteries to store electricity. While storing energy as heat is not mechanically efficient, the economic benefits of producing energy at peak demand may make the molten salt storage worthwhile.

Solar energy typically does a fairly good job of matching peak demands for electricity during the daylight hours, but can fall short in the early morning when people are getting ready for work or in the evenings after the sun goes down. Energy storage capabilities would allow renewable energies like solar to be harnessed around the clock, making them a more formidable competitor to fossil fuels.

(Photo: Solena Project by Abengoa Solar. Article via: New York Times, “Arizona Utility Tries Storing Solar Energy for Use in the Dark”)

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November 14, 2013 - Posted by | FKP | , ,


  1. Storing energy as molten salt is not new concept – it was developed in the 90s I think. Although it keeps the solar energy as thermal, I’ve read this approach has almost 100% annual efficiency.

    I don’t quite agree about the “holy grail”. Energy storage might be very useful for domestic purposes. In most cases solar plants are connected to the power grid and the energy they produce is utilized somewhere else.

    Comment by George | November 22, 2013 | Reply

    • Thank you for pointing out that molten storage is not a new technology. To clarify, Solena is the first project in the US to use thermal energy storage.

      To your second well reasoned point, while renewable energy is typically transmitted via the grid, with our current infrastructure, about 7% of electricity is lost in transmission, a figure that increases over long distances. As the percentage of renewable energy increases, there is greater need for either increased storage or a smart grid that could smooth out the variability in production and demand across large distances.

      Comment by freshkillspark | December 17, 2013 | Reply

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