In our original article "Determining Module Inter-Row Spacing," we examined how optimal inter-row spacing in photovoltaic (PV) systems is critical for maximizing energy production, ensuring compliance with building codes, and optimizing economic returns. Fast-forward five years into the future, and now we need to consider how advances in PV technology and updated building regulations necessitate a fresh perspective on these calculations.
These topics are a refresh of the previous thoughts with updated methodologies and considerations for modern systems.
Updated Calculation Methodology
Determine the Height Difference
The height difference between the back edge of the solar module and the mounting surface is essential for spacing calculations.
Formula:
Height Difference = sin(tilt angle) × module width
Example:
For a module width of 39.41 inches and a tilt angle of 15°:
Height Difference = sin(15°) × 39.41 ≈ 10.2 inches
Calculate Initial Row Spacing
Using the solar elevation angle, typically measured at solar noon during the winter solstice, calculate the baseline row spacing.
Formula:
Module Row Spacing = Height Difference ÷ tan(solar elevation angle)
Example:
With a height difference of 10 inches and a solar elevation angle of 17°:
Module Row Spacing = 10 ÷ tan(17°) ≈ 32.7 inches
Adjust for Azimuth Angle
The azimuth correction angle, representing deviation from true south, can impact the final spacing.
Formula:
Minimum Module Row Spacing = Module Row Spacing × cos(azimuth correction angle)
Example:
With a row spacing of 32.7 inches and an azimuth correction angle of 44°:
Minimum Module Row Spacing = 32.7 × cos(44°) ≈ 23.7 inches
Popular Bifacial Products and Their Impact on Inter-Row Spacing
Bifacial solar modules generate power from both sides of the panel, benefiting from reflected sunlight. However, these modules perform best with wider inter-row spacing and high-albedo surfaces. For installations prioritizing high energy yield and reduced LCOE, bifacial modules are an excellent choice, though they require thoughtful design adjustments.
East-West Combined Tilt Systems: A Different Approach
East-west combined tilt systems have gained popularity as a solution for maximizing rooftop or land utilization, particularly in installations where monofacial modules are used. While this design is not ideal for bifacial modules due to reduced rear-side exposure, it offers distinct advantages in specific scenarios.
How East-West Tilt Systems Work
Panels are mounted in alternating east-facing and west-facing orientations at a low tilt angle (typically 5–10°).
This arrangement allows for denser module placement, reducing inter-row spacing requirements.
Advantages of East-West Tilt Systems
Space Efficiency:
These systems maximize the number of modules per unit area, making them suitable for constrained rooftops or small ground-mounted systems.
More Consistent Energy Production:
Unlike south-facing systems that peak at midday, east-west systems produce more uniform power output throughout the day, reducing peak-demand stress on electrical systems.
Simplified Installation:
The low tilt angles reduce wind load concerns and structural requirements, making them easier and often cheaper to install.
Drawbacks Compared to South-Facing Systems
Lower Total Energy Yield:
East-west systems often sacrifice some total energy production compared to optimally spaced south-facing arrays due to reduced sunlight exposure at low tilt angles.
Suboptimal Performance for Bifacial Modules:
Bifacial modules require significant rear-side exposure, which is minimized in east-west configurations. This setup essentially negates the benefits of bifacial technology.
Shading Concerns:
Despite the dense layout, inter-row shading is still a consideration, especially in low-sunlight months. Proper modeling is crucial to mitigate shading losses.
Economic Considerations
Cost Savings:
While total energy yield is lower, the reduced installation costs and higher module density can offset some of the losses, making east-west systems economically attractive in certain cases.
System Choice:
East-west systems are better suited for projects where space constraints are a priority over maximizing energy production, such as commercial rooftops with limited usable space.
Leveraging Modern Tools
Contemporary software and tools have revolutionized how inter-row spacing is calculated. Platforms like HelioScope, Aurora Solar, and PVsyst integrate shading analysis, azimuth corrections, and energy simulations, providing designers with data-driven insights to optimize system layouts.
For follow-up questions or further guidance, please contact Greentech Renewables Design Services. To review the original article, click here.
