Headlines: Molten Salt an Answer to Renewable Energy Intermittency

March 7, 2014 – The greatest challenge renewable energy providers face is achieving a sustainable continuous supply of guaranteed power delivered to consumers either through the grid or off grid. That’s the single issue holding back large-scale adoption of renewables.

When driving back from Florida we passed through a portion of Southwestern Ontario teeming with wind power turbines. Some were turning at a good clip while others lay still. What is it like for a utility provider to have to deal with power that can be there in one minute and then not be there? With wind that’s certainly a big problem. That’s why extensive wind studies are done before locating a wind turbine.And with solar, reliability is limited to daylight peak hours and to the interference of cloud cover.

In both cases large-scale energy storage that can be released as needed can smooth out the bumps. That’s what companies like Halotechnics hope to provide. Currently the company is constructing a 1 Megawatt molten salt storage facility in California.

Why molten salt? Because the material stores the excess energy generated during the operational cycle of a renewable plant and converts that energy to heat which using conventional heat pumps can then be converted back to electricity when the wind dies or the Sun sets. Although less efficient than batteries (90%), the use of salts (70%) with properties that allow them to reliably melt introduces a lower cost solution.

Halotechnics have been experimenting with salts and has discovered materials that can be stored at temperatures of 1,200 Celsius (2,192 Fahrenheit). The material development has involved the use of robotic systems which mix the materials and test their properties to achieve a stable heat storage medium. The result is Haloglass RX, a stable oxide-based composite that melts at 450 Celsius, reaches maximum stability at 565 Celsius and can be scaled for use in thermal, wind and photovoltaic solar power plants.

The new plant is a pilot project with funding coming from ARPA-E. If successful, future molten salt storage facilities will be designed with much greater power generating capacity.

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• The Intermittency of Wind and Solar: Is It Only Intermittently a Problem?
• MIT’s Liquid Metal Stores Solar Power Until After Sundown