A tower resides in the centre of the heliostat field.The heliostats focus concentrated light on a receiver which sits on top of the
tower. Within the receiver, the concentrated sunlight heats molten salt to about 540 o C. The heated molten salt then flows into a thermal storage tank where it
is stored, maintaining 98% thermal efficiency, and eventually pumped to a steam generator. The steam drives a standard turbine to generate electricity.
This process, also known as the “Rankine Cycle” is similar to a standard coal-fired power plant, except it is fuelled by clean and free solar energy.
The advantage of this design above the parabolic trough design is the higher temperature. Thermal energy at higher temperatures can be
converted to electricity more efficiently and can be more cheaplystored for later use. Furthermore, there is less need to flatten the ground area.
In principle, a power tower can be built on a hillside. Mirrors can be flat and
plumbing is concentrated in the tower. The disadvantage is that each mirror
must have its own dual-axis control, while in the parabolic trough design one
axis can be shared for a large array of mirrors.
