Heliostat Camera Calibration for Open-Loop Suntracking Accuracy

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Solution Overview

Problem

In central tower receiver solar power plants, the accurate suntracking of hundreds to thousands of heliostats is hindered by manufacturing and installation tolerances, leading to spillage losses and inefficiencies in reflecting sunlight onto the receiver.

Innovation Solution

A system utilizing cameras to acquire pointing samples and estimate heliostat parameters for open-loop suntracking, allowing for precise orientation adjustments to minimize spillage and maximize flux concentration, by modeling heliostat geometry and using a controller to process images and control the heliostats.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If heliostats are manufactured and installed with standard mechanical tolerances, then economic costs are reduced, but suntracking accuracy deteriorates leading to spillage losses

Engineering Contradiction:

Improvespillage lossesVSAvoidmechanical tolerances

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The system performs preliminary calibration by capturing images of heliostats at multiple known positions and pre-computing correction parameters before normal operation. This allows the system to compensate for manufacturing tolerances in advance, enabling standard mechanical tolerances to be used without sacrificing tracking accuracy during power generation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the operational parameters of heliostats by applying computed correction values to their tracking commands. Instead of requiring tighter mechanical tolerances, the system adjusts the angular parameters dynamically based on measured deviations, thereby reducing spillage losses while maintaining economical manufacturing standards

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If heliostats are manufactured with high precision, then suntracking accuracy is improved, but economic costs increase

Engineering Contradiction:

Improvesuntracking accuracyVSAvoideconomic costs

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The system replaces mechanical precision requirements with an optical measurement and computational correction system. Instead of relying on precisely manufactured mechanical components, the system uses cameras to measure actual heliostat positions and computes software-based corrections, thereby achieving high suntracking accuracy without the high economic costs of precision manufacturing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If the number of heliostats is increased, then power generation capacity is improved, but system complexity and calibration difficulty increase

Engineering Contradiction:

Improvepower generation capacityVSAvoidsystem complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The system implements a universal calibration approach where a single set of camera systems and processing algorithms serves all heliostats in the field regardless of their number. The same image capture and parameter computation methodology is applied uniformly across the entire heliostat array, enabling the system to scale to large numbers of heliostats without proportionally increasing operational complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables accurate and efficient suntracking with reduced spillage and controllable flux patterns, improving energy conversion efficiency and reducing the economic costs associated with mechanical tolerances.

Implementation Method 1

Each heliostat has a rigid reflective surface capable of suntracking, that is, the surface takes on orientations throughout the day so as to maintain reflection of the moving sun onto the receiver

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS8104893B2Calibration and tracking control of heliostats in a central tower receiver solar power plant

Publication Date: 2012.01.31 SEPCOIII ELECTRIC POWER CONSTR CO LTD

AI summary

A suntracking system for a central receiver solar power plant includes a heliostat field for reflecting sunlight to a receiver, cameras directed toward at least a subset of the heliostats, and a controller. The cameras are configured to produce images of sunlight reflected from multiple heliostats. The heliostats include a mirrored surface having a settable orientation and have a geometry modeled by a set of parameters. A method of estimating heliostat parameters for open-loop suntracking includes acquiring pointing samples by setting the direction of reflection of the heliostats and detecting concurrent sunlight reflections into the cameras. The method uses the acquired pointing samples and surveyed locations of the cameras to estimate the heliostat parameters. The method accurately maintains the sun's reflection directed toward the receiver open-loop utilizing the estimated tracking parameters.