Power Tower


An array of sun tracking flat mirrors called heliostats concentrates irradiation from the sun onto a receiver, atop a central tower. This receiver contains a heat‐transfer fluid (water/molten salts) that upon absorption of highly concentrated thermal energy gets converted to steam which drives the turbine to generate electricity. 

There are three customary arrangements for the collector and receiver systems.

In the first the receiver tower is completely surrounded by a field of heliostats, and the receiver, which is cylindrical, has an exterior heat-transfer surface.

In the second, the heliostats are located north of the receiver tower (in the northern hemisphere), and the receiver has an enclosed heat-transfer surface.

In the third, the heliostats are located north of the receiver tower, and the receiver, which is a vertical plane, has a north-facing heat-transfer surface.


The components fundamental to power tower technology are:

Heliostats -

A Heliostat is a device that reflects its incident direct solar radiation onto a receiver. Its components include a reflective surface, usually in the form of flat mirrors, a supporting structure and a motorized system to track the movement of the sun. The heliostat design must ensure that radiation is delivered to the receiver at the desired flux density at minimum cost.

Receiver –

The enormous amount of energy thus received, produces temperatures of approx. 550°C to 1500°C. The receiver then transfers this heat to a heat-transfer fluid that may either be water/steam, liquid sodium, or molten nitrate salt (sodium nitrate/potassium nitrate).

Various receiver shapes have been considered, including cavity receivers and cylindrical receivers.  For a large heliostat field a cylindrical receiver has advantages when used with Rankine cycle engines while Cavity receivers are advantageous with larger tower height to heliostat field area ratios for higher temperatures, required for the operation of Brayton cycle turbines.

Tower -

The tower acts as a pillar on which the receiver rests. The height of the tower should be such that it rises above the heliostats level to avoid, or at least reduce, shades and blockings.