How heliostats are pointed accurately at the receiver
Aiming heliostats requires precise calculations and control to ensure each mirror reflects sunlight to the central receiver. Calibration and aiming combine geometric algorithms, sensors, and feedback loops to maintain accurate pointing throughout the day.
Typical aiming and calibration steps:
- Sun position calculation: Software computes the sun’s azimuth and elevation at each moment based on time, location, and atmospheric refraction corrections.
- Optical model and aimpoint determination: The control system calculates the mirror orientation needed to reflect sunlight from the heliostat position to the receiver target, considering cosine losses and local terrain.
- Encoder and actuator control: Motors or actuators move the heliostat axes to the commanded positions using shaft encoders or position sensors for precision.
- Calibration and feedback: Field tests, cameras, flux sensors, and alignment checks refine pointing offsets and compensate for mechanical misalignments or wind-induced deformations.
Methods to improve accuracy and reliability:
- Closed-loop control: Sensors at the receiver or intermediate targets provide real-time feedback to correct pointing errors.
- Periodic calibration: Automated routines and periodic optical checks ensure long-term alignment despite structural shifts.
- Predictive correction: Software accounts for mirror panel warping, thermal expansion, and wind loading to preempt pointing errors.
High-accuracy aiming maximizes energy captured by the receiver and protects it from uneven flux. With thousands of heliostats in large fields, efficient and automated aiming systems are essential to plant performance and operational cost control.