Role and operation of heliostats
Heliostats are individually tracked mirrors that reflect and concentrate sunlight onto a central receiver atop a tower in power tower systems. Each heliostat moves in two axes to keep the reflected beam aligned with the receiver as the sun moves.
Key functions and features:
- Dual-axis tracking: keeps the reflected ray aimed at the receiver throughout the day.
- Field layout: heliostats are arranged to minimize shading, blocking, and cosine losses while maximizing useful flux on the receiver.
- Control systems: centralized or distributed controllers compute mirror positions based on sun geometry and feedback sensors.
Important design considerations:
- Mirror quality and stability: optical accuracy affects concentration and receiver flux distribution.
- Aimpoint control: heliostats can be aimed to produce an even flux on the receiver surface, improving thermal performance and lifetime.
- Maintenance: cleaning, alignment, and replacement of drives or mirrors are ongoing needs.
Heliostat fields are scalable and allow high temperatures at the central receiver, enabling efficient thermal cycles and thermal storage integration for dispatchable power generation.