Technology Type

A central tower (CT) solar plant, also known as a power tower or heliostat power plant, is a Concentrated Solar Power (CSP) facility that uses an array of sun-tracking mirrors (heliostats) to focus sunlight onto a receiver at the top of a central tower.

The system works by hundreds or thousands heliostats tracking the sun and reflecting light on a central receiving tower, where the receiver is absorbing concentrated solar energy that is transferred to a heat transfer fluid reaching temperatures of up 1,000°C. Steam generated by heat exchange is driving conventional turbines for electical power generation. Computer systems are continuously adjusting mirror positions.

The key components of a central tower solar plants are:

• Field of heliostats (flat mirrors with tracking systems)
• Central tower (50-100 meters high)
• Solar receiver at tower top
• Heat transfer fluid system
• Steam generation system
• Turbine-generator set
• Control systems for mirror tracking

The system requires large land areas (150-320 hectares), it has higher operating temperatures than other CSP technologies, an improved heat-to-electricity conversion efficiency, and can operate several hours after sunset. It can be combined with energy storage by including thermal storage using molten salts.

The technology represents one of the main concentrated solar power options, with successful implementations including the Solar One and Solar Two projects in California, and the PS10 and PS20 plants in Spain.