The Gemasol solar plant in Spain is the first solar plant in the world to provide uninterrupted baseload power - supplying electricity for 15 hours without the sun.
One of the biggest criticisms of solar energy is its intermittent nature - it can only provide energy when the sun is shining, and supplies the most when the sun is strongest.
Now, that's changing. Thanks to molten salt storage, the solar system will eventually be able to supply electricity 24 hours a day on most summer days, providing more energy a year than most baseload plants - such as nuclear plants.
Operating since May, Torresol Energy's 19.9 megawatt (MW) concentrating solar tower plant, in Seville, Spain, is the first commercial-scale solar plant that stores solar energy in molten salt.
The plant can operate at temperatures over 500°C, allowing for significantly increased efficiency.
The molten salt storage system is used in conjunction with a tower that's over 426 feet tall, and an array of 2,650 tracking heliostats that concentrate solar radiation at a ratio of 1000:1.
The system absorbs 90% of the sun's light and transmits it to the molten salt, which is then used to heat steam and operate the plant's 19 MW steam turbine.
It produces electricity for 15 hours without sunlight, overcoming fluctuations in energy supply and providing energy to the grid based on demand, regardless of time of day.
In the US, a much bigger solar tower project received a $737 million loan guarantee from the Department of Energy - the Crescent Dunes Solar Energy Project. The 110 MW concentrating solar tower plant in Nevada will have 640-foot tower that also uses molten salt as its primary heat transfer and storage medium.
Sponsored by SolarReserve, it will be the first of its kind in the US and the tallest molten salt tower in the world. When it becomes operational, it's expected to produce about 500,000 megawatt hours a year.