A PV array is laid out with three geometric decisions: the tilt of the tables, their orientation and the spacing between rows (pitch). The ratio between table width and pitch is the GCR (ground coverage ratio): a high GCR puts more power per hectare, but increases mutual shading when the sun is low. Near the equator the optimal tilt is low, and for bifacial modules the ground albedo and the table height also count.
What the array layout decides
The PV array is the area where modules are mounted on tables or trackers. Its geometry defines how much power fits on the land, how much irradiance each module receives and how much energy is lost to shading between rows. These decisions are made with the production simulation and the resource of the site, which is estimated with public radiation databases (see the guide on solar radiation atlases and data) and with on-site measurement. The electrical design of strings and cables follows, along with the grid connection of the plant, which follows the local code and the utility requirements.
IEC 62548-1 covers the electrical and mechanical design of the array: DC wiring, protection, switching, grounding and requirements for the mounting structures. The optimal geometry, in contrast, is not set by a standard: it comes from the balance between energy and cost. The design of the complete park is laid out in the guide on solar park engineering and design.
The terms: pitch, table width and GCR
| Term | Definition | What it controls |
|---|---|---|
| Table width (L) | Dimension of the table in its own plane, in the direction of the row spacing | The height of the upper edge and the shadow it casts |
| Tilt (β) | Angle of the table with respect to the horizontal | Captured irradiance, self-cleaning and shadow height |
| Pitch (p) | Distance between equivalent points of two consecutive rows | Mutual shading, maintenance aisles and occupied area |
| GCR | L / p | Power per hectare versus shading losses |
With these data, the height of the upper edge above the lower one is L·sin β, and the horizontal projection of the table is L·cos β. The free space between rows is the pitch minus that projection.
Shading between rows
When the sun is low, each row shades the lower part of the next. The length of the shadow on the ground is the height of the upper edge divided by the tangent of the solar elevation, corrected by the angle between the sun and the row direction. The designer chooses a critical condition, for example a certain hour of the morning and of the afternoon on the least favorable day of the year, and sets the pitch so that from that point on there is no shade.
That rule is only the starting point. A larger pitch eliminates shadows that last a few minutes, but it takes more land, lengthens cables and structures and leaves less power on the same plot. The final decision is made by comparing annual energy for different pitches in the simulation.
The electrical effect of shade. A small shadow can cost much more than its area. The cells of a module are in series, grouped by bypass diodes: when a row of cells is shaded, its diode conducts and the module loses that group. If the shadow covers the lower strip of all the modules in a string, the whole string drops its current. That is why care is taken over how the module is oriented on the table, portrait or landscape, and how strings are arranged with respect to the shadow advancing from below.
- Does the available land limit the project power?
- Yes: Does the extra energy from more modules exceed the loss from shading and inverter clipping in the simulation?
- Yes: Increase the GCR and group in the same strings the modules of the strip that is shaded first
- No: Keep the pitch and review the DC/AC ratio
- No: Use a pitch that avoids shade during the hours of highest irradiance, with less mismatch and less work for the bypass diodes
- Yes: Does the extra energy from more modules exceed the loss from shading and inverter clipping in the simulation?
Tilt and orientation near the equator
Colombia lies between about 4° south and 12° north latitude. Over the year the sun crosses the zenith and spends some months north and others south of the observer, so the tilt that maximizes the annual energy of a fixed table is small. A low tilt also reduces the height of the shadow and allows a smaller pitch.
Self-cleaning sets a practical minimum. With very little tilt, water pools at the edge of the frame and leaves dust and mud on the last cells. Module manufacturers state the minimum permitted tilt in their installation manuals; the design respects it even if the simulation suggests a smaller angle.
As for orientation, fixed tables in the northern hemisphere usually face south. Near the equator the difference between orientations is small, and some designs use east-west tables, with two slopes, to put more power per hectare and flatten the daily curve. This is another decision validated with the simulation.
Bifacial modules and albedo
A bifacial module also converts the irradiance that reaches its rear face, reflected by the ground and scattered by the sky. Its gain depends on:
- Ground albedo: the fraction of irradiance it reflects. Light, dry ground reflects more than vegetation or wet soil.
- Table height: more height reduces the self-shading on the ground under the module.
- GCR: a very compact array leaves less illuminated ground between rows.
- Rear structure: beams and junction boxes that shade the back face.
The International Energy Agency report IEA PVPS T13-14:2021 collects the experience with bifacial modules and systems and the factors that affect their output. Bifacial gain is estimated with rear-side models and confirmed by on-site measurement; data sheets declare the bifaciality factor of the module, not the gain a specific plant will have.
Fixed structure or tracker
The fixed structure is simple, cheap and almost maintenance-free. The single-axis tracker rotates the rows from east to west during the day and captures more energy, especially at sites with a high fraction of direct radiation. In exchange, it adds motors, controllers, communications and a backtracking logic at the end of the day to avoid shading between rows. The choice depends on the resource, the terrain, the design wind and the cost of energy. Tracker types, stow position and operation are covered in solar trackers.
What the array layout hands to the electrical engineering
- Number of tables and modules, and their arrangement on the plot.
- Grouping of modules into strings according to shade and voltage.
- Routes of string cables and main cables to inverters or combiner boxes.
- Location of inverters, such as the Huawei SUN2000 or the Sungrow, transformer stations and aisles.
- Areas for grounding, lightning shielding and the weather station.
We help with the engineering of your plant
With the layout defined, our team does the primary engineering of the plant: strings, DC and AC wiring, medium-voltage network, substation, grounding and drawings for the utility. We do it remotely, worldwide, without travel. Tell us about your project.
Related guides
References
- IEC 62548-1:2023, Photovoltaic (PV) arrays – Part 1: Design requirements.
- IEA PVPS Task 13, report T13-14:2021, Bifacial Photovoltaic Modules and Systems: Experience and Results from International Research and Pilot Applications.
- Module manufacturers’ installation manuals (minimum tilt, mounting and orientation).
Frequently asked questions
What is the GCR of a solar plant?
It is the ground coverage ratio: the width of the module table measured in its own plane, divided by the distance between rows. A GCR of 0.5 means the modules take up half of the space between rows, measured in the spacing direction. The higher it is, the more compact the array and the more mutual shading.
What tilt should solar panels have near the equator?
Colombia, for example, lies between about 4° south and 12° north latitude, so the tilt that maximizes the annual output of a fixed structure is low. In practice a somewhat larger angle is chosen so that rain washes away dust, respecting the minimum tilt stated in the module manufacturer manual. The exact figure comes from simulation with the resource and the geometry of the site.
How is the distance between rows of panels calculated?
It starts from the height reached by the upper edge of the table and from the sun elevation at the most demanding hour to be protected from shade. The horizontal shadow is that height divided by the tangent of the solar elevation, projected in the direction between rows. This sets a minimum pitch, and the final decision compares the energy lost to shading with the energy gained from more modules.