Ground Coverage Ratio (GCR) in Solar Power Generation Stations System Design

1. Definition and Importance of GCR

Definition: GCR is the ratio of the total area of PV modules to the total ground area. The calculation formula is as follows:

GCR = (PV Module Total Area) / (Total Ground Area)

Importance: GCR affects the layout and performance of solar power stations. A higher GCR value indicates smaller spacing between PV modules, potentially leading to shading and reduced system efficiency. A lower GCR value signifies larger spacing, which can enhance the utilization of ground-reflected light and improve system efficiency.

2. Impact of GCR on System Performance

Reflection Gain:

A smaller GCR means larger spacing between PV modules, allowing more sunlight to be reflected from the ground, which increases reflection gain. The calculation formula is:

Reflection Gain = GCR × Ground Reflectance

For example, if the ground reflectance is 0.4 and GCR is 0.5, then the reflection gain would be 0.2.

Shading:

Higher GCR values may lead to shading between PV modules, reducing overall power generation efficiency. Therefore, it is essential to strike a balance between enhancing reflection gain and minimizing shading.

Land Utilization:

While a lower GCR increases reflection gain, it also requires a larger land area. Thus, land costs and available space must be considered in the design process.

3. Methods to Optimize GCR

Adjusting PV Module Spacing:

By increasing the spacing between PV modules, the GCR value can be reduced, allowing more sunlight to reach the ground and enhancing reflection utilization. The calculation formula is:

PV Module Spacing = (Total Ground Area / Number of PV Modules) - PV Module Width

For instance, if the total ground area is 1000 square meters, the number of PV modules is 200, and each module width is 1 meter, then:

PV Module Spacing = (1000 / 200) - 1 = 4 - 1 = 3 meters

Increasing Ground Reflectance:

Using high-reflective ground materials, such as white coatings or reflective films, can enhance ground reflectance, thus improving reflection gain:

Reflection Gain = GCR × Ground Reflectance

If the ground reflectance increases from 0.2 to 0.6 while keeping GCR constant, the reflection gain would rise from 0.1 to 0.3.

Optimizing Installation Height:

Raising the installation height of PV modules can minimize shading, enhancing overall system efficiency. However, the impact of installation height on reflection gain is relatively small and typically not a primary optimization method.

The calculation formula for installation height is:

Installation Height = Support Height + Module Thickness

For example, if the support height is 1.5 meters and the module thickness is 0.1 meters, the installation height would be 1.6 meters.

4. Integrated Optimization Strategies

Combining GCR and Ground Reflectance:

To maximize reflection gain, the system performance can be optimized by adjusting both GCR and ground reflectance. The calculation formula is:

Optimal GCR = (Target Reflection Gain) / (Ground Reflectance)

If the desired reflection gain is 0.25 with a ground reflectance of 0.4, then the optimal GCR would be 0.625.

Considering Environmental Conditions:

Local solar irradiance, climate conditions, and seasonal variations affect the optimal value of GCR. The calculation formula is:

Annual Average Reflection Gain = Sum(Daily Reflection Gains) / (Number of Days in Year)

For example, if the summer reflection gain is 0.25 and the winter reflection gain is 0.15, the annual average reflection gain would be 0.2.

Economic Viability:

When optimizing GCR, it is also crucial to consider the economic aspects, including land costs, installation costs, and maintenance costs:

Total Cost = Land Cost + Installation Cost + Maintenance Cost

Economic Benefit = (Annual Power Generation Revenue) / (Total Cost)

5. Simulation and Verification

Using Simulation Software:

Simulation software such as PVsyst can be employed to model system performance under different GCR values, ensuring design validity:

Simulated Reflection Gain = Software Simulation Results

For instance, PVsyst may show that a GCR of 0.5 yields a reflection gain of 0.15, while a GCR of 0.3 results in a reflection gain of 0.25.

Field Testing:

Field testing and validation are essential in practical applications. Installing a trial system and monitoring power generation under varying GCR values provides a more accurate performance assessment:

Actual Reflection Gain = (Actual Power Generation Gain) / (Baseline Power Generation)

6. Case Study

Assumed Conditions:

Total ground area: 1000 square meters, total area of PV modules: 500 square meters, and ground reflectance of 0.4.

Calculation Steps:

1. 1. Calculate GCR:

GCR = 500 / 1000 = 0.5

1. 1. Calculate Reflection Gain:

Reflection Gain = 0.5 × 0.4 = 0.2

1. 1. Adjust GCR to Increase Reflection Gain:

If the target reflection gain is 0.25, the optimal GCR is:

Optimal GCR = 0.25 / 0.4 = 0.625

Adjusting PV module spacing results in:

PV Module Spacing = (1000 / 200) - 1 = 3 meters

1. 1. Economic Evaluation:

Calculating total cost:

Total Cost = Land Cost + Installation Cost + Maintenance Cost

Assuming land cost = 50000, installation cost = 30000, maintenance cost = 10000:

Total Cost = 90000

Calculating Economic Benefit:

Assuming annual power generation revenue = 120000:

Economic Benefit = 120000 / 90000 = 1.33

7. Considerations

Avoiding Redundant Calculations: Utilize intermediate results to avoid repeated calculations and enhance efficiency.

Data Organization: Sort common data and formulas into tables for quick reference and utilization.

Blueprint Annotations: Mark calculated quantities on construction drawings to reduce the time spent re-referencing.

Construction Feasibility: Use “conceptual construction simulations” to analyze the feasibility of each step; ensure accurate recording of tools used for each process.

8. Conclusion

Optimizing GCR is one of the key steps to enhance the performance of solar power generation stations. By reasonably adjusting GCR values, increasing ground reflectance, and optimizing installation heights, we can maximize power generation efficiency while ensuring system economic viability. The calculation methods and case studies provided in this article aim to offer practical guidance to engineers and designers, contributing to the advancement of green energy.

References

• Research on the Power Generation Characteristics of Bifacial Tracking PV Systems: Detailed exploration of the impact of GCR, ground reflectance, and installation heights on bifacial PV power output.
• Design and Construction of Solar PV Power Systems: Insights on the design processes and installation considerations for solar PV systems.
• Analysis of Roof Installed Area Ratio for PV Systems under Green Building Standards: Examination of installation area ratio requirements for different building types under green building standards.

Solar Power Generation Stations: Types, Benefits, and Case Studies