page_title: Solar thermal energy
section_title: Molten salt storage
hierarchical_section_title: Solar thermal energy / Heat storage for electric base loads / Molten salt storage
caption_attribution_description: English: Andasol Solar Power Station Español: Planta termosolar Andasol, ubicada en en el Marquesado de Zenete en el municipio de Aldeire (Granada). Promovida, construida y operada por ACS-Cobra Energía Français&#160;: Centrale thermosolaire Andasol, située dans la commune d'Aldeire (prov. de Granade, en Espagne). Planifiée, construite et exploitée par ACS-Cobra Energía, cette centrale utilise la technologie de stockage de chaleur dans des réservoirs de sel fondu, afin de pouvoir aussi produire de l'électricité la nuit ou le jour quand le soleil ne brille pas.
context_page_description: Solar thermal energy is a form of energy and a technology for harnessing solar energy to generate thermal energy or electrical energy for use in industry, and in the residential and commercial sectors.
  Solar thermal collectors are classified by the United States Energy Information Administration as low-, medium-, or high-temperature collectors. Low-temperature collectors are generally unglazed and used to heat swimming pools or to heat ventilation air. Medium-temperature collectors are also usually flat plates but are used for heating water or air for residential and commercial use.
  High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used for fulfilling heat requirements up to 300 deg C / 20 bar pressure in industries, and for electric power production. Two categories include Concentrated Solar Thermal for fulfilling heat requirements in industries, and Concentrated Solar Power when the heat collected is used for power generation. CST and CSP are not replaceable in terms of application.
  The largest facilities are located in the American Mojave Desert of California and Nevada. These plants employ a variety of different technologies.
context_section_description: Molten salt is used to transport heat in solar power tower systems because it is liquid at atmospheric pressure, provides a low-cost medium to store thermal energy, its operating temperatures are compatible with today's steam turbines, and it is non-flammable and nontoxic. Molten salt is also used in the chemical and metals industries to transport heat.
  The first commercial molten salt mixture was a common form of saltpeter, 60% sodium nitrate and 40% potassium nitrate. Saltpeter melts at 220 °C (430 °F) and is kept liquid at 290 °C (550 °F) in an insulated storage tank. Calcium nitrate can reduce the melting point to 131 °C, permitting more energy to be extracted before the salt freezes.  There are now several technical calcium nitrate grades stable at more than 500 °C.
  This solar power system can generate power in cloudy weather or at night using the heat in the tank of hot salt. The tanks are insulated, able to store heat for a week. Tanks that power a 100-megawatt turbine for four hours would be about 9 m (30 ft) tall and 24 m (80 ft) in diameter.
  The Andasol power plant in Spain is the first commercial solar thermal power plant using molten salt for heat storage and nighttime generation. It came on line March 2009. On July 4, 2011, a company in Spain celebrated an historic moment for the solar industry: Torresol’s 19.9 MW concentrating solar power plant became the first ever to generate uninterrupted electricity for 24 hours straight, using a molten salt heat storage.
  In 2016 SolarReserve proposed a 2 GW, $5 billion concentrated solar plant with storage in Nevada.
  In January 2019 Shouhang Energy Saving Dunhuang 100MW molten salt tower solar energy photothermal power station project was connected to grid and started operating. Its configuration includes an 11-hour molten salt heat storage system and can generate power consecutively for 24 hours.
caption: The 150 MW Andasol solar power station is a commercial parabolic trough solar thermal power plant, located in Spain. The Andasol plant uses tanks of molten salt to store solar energy so that it can continue generating electricity even when the sun isn't shining.[58]
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