For single-axis solar trackers operating in regions with high cloud cover, where diffuse irradiance constitutes a significant portion of the total solar radiation, traditional tracking algorithms that focus solely on maximizing direct beam irradiance are less optimal. Instead, algorithms that incorporate both direct and diffuse irradiance in their optimization can improve energy yield.
Key Algorithms for Single-Axis Trackers in High Cloud Cover Regions
1. True-Tracking Algorithm
– This basic and widely used algorithm orients the solar panels to face the sun as directly as possible, maximizing the incident direct beam irradiance.
– It calculates the solar position at every time step and adjusts the tracker angle accordingly.
– However, true-tracking is primarily optimized for clear-sky conditions where direct irradiance dominates, and does not account for diffuse irradiance.
– This makes it less effective in high cloud cover regions where diffuse light is predominant.
2. Backtracking and Slope-Aware Backtracking
– Backtracking algorithms adjust the tracker angle to avoid shading between rows in densely packed arrays, improving overall energy production.
– Slope-aware backtracking further refines this by taking terrain slope into account, optimizing angles for uneven sites.
– These algorithms still primarily target direct beam irradiance optimization but can help reduce losses related to shading.
3. Optimization Algorithms Incorporating Diffuse Irradiance
– Recent advancements focus on maximizing total irradiance collection, considering both direct and diffuse components, to improve performance in cloudy regions.
– By modeling the contribution of diffuse sky radiation on panel tilt and orientation, these algorithms find a tracking position that maximizes overall energy rather than just direct irradiance.
– NREL research shows potential annual insolation gains of up to 1% in certain climates with high diffuse fraction by using such optimization algorithms over conventional direct-beam-only tracking.
– The approach involves analyzing climate-specific diffuse insolation fractions to tailor the tracking control strategy accordingly.
4. Comparative Evaluations
– Studies comparing various horizontal single-axis tracking algorithms indicate that algorithms integrating diffuse irradiance factors can outperform traditional true-tracking under partly cloudy or overcast conditions.
| Algorithm Type | Target Insulation | Effectiveness in High Cloud Cover |
|---|---|---|
| True-Tracking | Direct beam only | Lower effectiveness, optimal in clear-sky conditions |
| Backtracking / Slope-Aware Backtracking | Direct beam with shading | Good for shading reduction, less impact on diffuse light |
| Diffuse-Optimized Tracking | Direct + Diffuse irradiance | Improved energy capture by accounting for diffuse light |
Summary
For single-axis trackers in high cloud cover regions, the most effective algorithms are those that optimize total irradiance — both direct and diffuse components — rather than only minimizing the angle of incidence to direct beam irradiance. These algorithms provide measurable performance gains (0.1% to 1%) by better adapting tracker angles to diffuse lighting conditions typical of cloudy climates. Conventional true-tracking and backtracking algorithms are less optimal under such conditions, as they neglect the diffuse irradiance contribution.
References:
- True-tracking explanation and limitations.
- Slope-aware backtracking concept.
- Optimization for diffuse irradiance in single-axis trackers and performance gains.
- Comparative algorithm evaluation.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-algorithms-are-most-effective-for-single-axis-trackers-in-high-cloud-cover-regions/
