GCR
The GCR (Ground Coverage Ratio) is an indicator of the geometry of your PV array, basically defined as:
However, the GCR cannot be universally defined as it depends on the exact definition of both areas:
- The PV area may be the PV modules' sensitive area only, or the area occupied by the PV modules and their mounting structures (including spaces, inactive bands, etc.). PVsyst uses different definitions of the PV area depending on the purpose of the GCR metric.
- The ground area is difficult to specify in a general way: what area is included around a single table? Around the full system? Should the circulation ways be included? The ground area may be defined in slightly different ways depending on the PV installation type.
Note that the GCR is displayed for your information only and is not used directly in the simulation
PV area definition
PVsyst uses different definitions of the PV area depending on the context, leading to several GCR formulas:
- GCR Module (GCRMod) : The PV area corresponds to the module surface only. No inactive zones, spacing between modules, etc., are taken into account
- GCR Shading (GCRShd) : The PV area corresponds to the area contributing to shadings. It includes the module surface, spacing between modules and some of the inactive bands, depending on the geometry. The exact definitions for each system are given in the table below.
- GCR Backtracking (GCRBT) : This is the GCR value used when computing tracker positions in backtracking mode. By default it is equal to the GCR shading for a given system. However, it can be overridden in the Backtracking Management window by changing the reference pitch used for the backtracking computation.
- GCR bifacial (GCRBifi) : The PV area is the area contributing to ground shading in the bifacial computation. It includes the module surface and all inactive areas (spacing between modules, inactive bands, central gap when defined). It is slightly different from GCR Shading (GCRShd) as all inactive zones are always taken into account.
PV area for GCR shading
Most PV systems used in Pvsyst can be defined with some inactive bands, typically corresponding to mounting structures. However, not all inactive regions create shade on other nearby PV panels. Which inactive bands are included in the PV area definition is listed per system in the table below
| System Type (Orientation) | PV Area Definition (GCRShd) | Comments |
|---|---|---|
| Unlimited sheds | PV modules, intermodule spaces, top inactive band. | bottom inactive band does not contribute to shadings |
| Tracking horizontal axis N-S, Tracking tilted axis | PV modules, intermodule spaces, central gap, average of the right/left inactive bands. | |
| Tracking horizontal axis E-W, Tracking two-axis frame N-S | PV modules, intermodule spaces, top inactive band. | no central gap defined |
| Unlimited Trackers, Tracking two-axis frame E-W, Tracking two-axis | PV modules, intermodule spaces, average of the right/left inactive bands. | no central gap defined |
| Other systems (excluding BIPV) | PV modules, intermodule spaces, both inactive bands. |
Ground area definition
The Ground Coverage Ratio is a relevant metric for regular arrays of trackers or sheds with fixed tilt. It represents the "density" of the PV sensitive areas. The higher the GCR, the higher the mutual shading losses.
Unlimited sheds or trackers
The orientations "Unlimited sheds" or "Unlimited trackers" correspond to a simplified 2D model of a regular array of trackers or fixed tilt PV tables. In this case, the ground area is defined as the area between the base of two consecutive rows, i.e., the pitch multiplied, by the row length.
3D scenes
Arrays
For 3D scenes constructed in PVsyst using arrays of trackers, tables, domes or sun-shields, the ground area is computed from the pitch and length for each array. If several orientations are defined in your project, the GCR will be computed for each orientation separately. Note that none of the GCRs take into account the ground areas between arrays (such as circulation spaces).
Imported scenes
When importing 3D scenes (especially on a terrain), the tables do not necessarily have a regular arrangement. In this situation, the GCR can be hard to define and should be used with caution.
To compute the GCR, PVsyst tries to evaluate the average distance between each table and the next one in the 3D geometry. Cases of double pitches (or more) are rejected when computing the average. This is a fuzzy evaluation: the result may look a little bit strange in some special situations.
The terrain width for each table is the width of the table. Therefore, the eventual spaces between adjacent tables are not taken into account.
This evaluation also doesn't include the circulation areas and should be considered representative of the density of tables.
BIPV Systems
No GCR is defined in PVsyst for building-integrated Photovoltaics (BIPV) installations (such as sun-shields, tracking sun-shields). They are vertical and the ground occupation cannot be defined.