Slope Analysis Case Study

Unique use cases are the best way to showcase the capabilities of the software. This slope case study demonstrates how PVcase software solves complex solar engineering issues. The focus is on a solar plant project situated between two hills with potential shading issues.

The challenge for this site is its location in a valley between two hills, which introduces the risk of horizon shading. The site is located in the TOU territory, making a tracker system an ideal option for higher production. However, the initial assessment shows that constructing a tracker system may be challenging due to the site's conformity. Therefore, it is important to compare trackers and fixed-tilt systems to present an alternative solution.

Introduction

The project examined in this case study is in the early stage of development. The land available for development is 171.45 acres (7,468,705 sq. ft). The goal is to determine if the size and production of the solar system are economical and whether the site is feasible for construction.

Another aim is to calculate if the site is buildable and which type of system is more suitable by comparing key values between single-axis trackers and fixed-tilt systems.

First, it is necessary to have topography data and understand the limitations of each racking system. In this case, the preferred racking vendor provides the following slope limitation parameters: 10 degrees for a single-axis tracker and 17 degrees for the fixed-tilt system.

Procedures

To achieve the goal of this study, the terrain mesh feature in PVcase is used. This tool generates a 3D ground surface from topographic data, helping to visualize the site for a more efficient slope study. If topographic information is not available, the PVcase Online Terrain Import feature can be used.

First, a 3D terrain mesh is generated. The Slope setup table allows control over the detail of the terrain mesh and the slope direction to study for a particular system: north-south for single-axis trackers, east-west for fixed-tilt. To break down the slope changes, both systems start at a 0-degree slope. The ending value is set higher at 20 degrees for the fixed-tilt system compared to 15 degrees for the single-axis tracker system, due to each system's limitations. This value is also slightly higher than their limitation to maximize capacity and later utilize the ground grading tool to determine the civil work necessary once the capacity is optimized.

Site Generation and Visualization

With a similar frame preset, there are two types of frames: 26 modules and 13 modules. Each frame has one module in portrait for both fixed-tilt and tracker sites to maximize capacity. The sites are set up with the sun angle at 25.63 degrees on December 21 at noon.

At this point, the layout can be exported to PVcase Yield or PVsyst for production simulation to compare the two systems.

Interpretation

Table 1 outlines the key performance between the two sites. Due to the single-axis tracker system having a low slope tolerance compared to the fixed-tilt system, the fixed-tilt layout has a higher capacity. Despite having a higher specific production and ground coverage ratio (GCR), the tracker layout for this site is particularly challenging. The site limits the tracker layout to 14.405 MW, which is 32.25% less compared to a traditional fixed-tilt system. The fixed-tilt layout experiences lower near shading compared to the tracker layout with backtracking, resulting in a 2.88% higher performance ratio and 25.15% overall produced energy. Additionally, the fixed-tilt site requires 27.96% less land to achieve a higher capacity, making it more cost-effective in terms of land leasing or purchasing.

Based on these production indicators, it is more beneficial for owners to utilize the fixed-tilt layout at this site due to the higher capacity fit and energy export back to the grid. Mechanically, fixed-tilt frames handle higher slope deviation better, making them a better fit for this site. Conversely, the tracker layout is less suitable due to its slope limitation, resulting in significantly less capacity and, despite a 27.97% higher GCR, 25.15% less overall production than the fixed-tilt layout.

Conclusion

The results show that a fixed-tilt system is a better approach for high-level development at sites with higher slope variance. The initial evaluation indicates that using the fixed-tilt approach makes this site a possible buildable site.

The terrain mesh tool, along with other PVcase features, can be used to make decisions at the early stage of project development. In this slope study, the terrain mesh, terrain-based site generation, and PVcase Yield or PVsyst export features were used to help users understand the best fit system for the given site, maximizing capacity and production while eliminating unfavorable or unnecessary risk options.