Concentrated Solar Power Systems (CSP)

• See Parabolic Trought Plant• See Central Receiver Plant
The main technology which is currently adopted on a commercial scale and which is relatively simple and efficient is called Molten Salts Storage System, referring to a mixture of Sodium Nitrate and Potassium Nitrate kept in melted form in storage tanks. This fluid is also being used as Heat Transfer Fluid instead of synthetic oil. This environmentally friendly innovation from SQM also significantly increases the CSP plant's efficiency.

The heat absorbed by the nitrates is released to keep the plant running even when the sun is not shining, 24/7.

SQM is a worldwide solution partner in concentrated solar power projects.

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Working Principle of a Parabolic Trough CSP Plant

A Parabolic Trough is a type of solar thermal energy collector, constructed as a long parabolic mirror with a receiver tube running its length at the focal point.

Sunlight is reflected by the mirror and concentrated on the receiver tube. The trough is usually aligned on a north-south axis and rotates to track the sun as it moves across the sky. Heat transfer fluid runs through the tube to absorb the concentrated sunlight, which increases the fluid temperature to some 400 °C (752 °F). The heat transfer fluid is then used to heat steam in a standard turbine generator. In the Parabolic Trough plants currently under construction and which use this technology, thermal storage systems with an output of 6 to 8 hours are being implemented. Central Receiver storage systems are being developed to reach even 15 hours.

Schematic Diagram of Parabolic Trough Plant:

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Working Principle of a Central Receiver CSP Plant

This method of collecting energy is based on concentrating the sun's energy onto a common focal point to produce heat to run a steam turbine generator. It has hundreds of large mirror assemblies, called heliostats, which track the sun to reflect the solar energy onto a tower where a black receiver absorbs the heat.

High-temperature heat transfer fluid is used to transport the heat to a boiler where the steam is used to spin a series of turbines, much like in a traditional power plant. This solar thermal storage system improves handling of the central tower plants and considerably increases its capacity factor to 70% or more.

Already back in 1995, SQM supplied thermo-solar salts to the Solar Two Power Tower pilot project in Barstow, California, USA, where they were used as heat transfer fluid and heat storage medium. The data collected in this project has been the main information source to contribute to the development of the CSP plant technology.

Schematic Diagram of CSP Central Receiver Plant:

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