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Plane orientation modes

The Orientations menu handles the definition of orientations, their kind and parameters.

Each orientation should have one or several associated sub-arrays (PV modules and inverters electrical definitions). If a 3D scene is defined, 3D fields have to be defined, which should be able to receive the PV modules defined in the "sub-arrays".

PVsyst supports simulations with many plane orientation modes:

  • Fixed tilted plane: you just have to define the Plane tilt and azimuth. In the 3D scene, the fixed planes may be of different kinds: single tables, arrays of tables, coplanar multi-rectangles of different sizes, customized polygons, etc.
  • Domes: this is a particular case of fixed planes, with 2 arrays of opposite tilted planes (usually east-west oriented). In the orientations definition, a dome corresponds to 2 coupled orientations.
  • Seasonal tilt adjustment: the plane tilt may be adjusted with two values, for winter and summer chosen months.
  • Unlimited sheds: is a convenient and quick way for defining an array of sheds (rows), taking the mutual shadings into account, without defining a 3D scene.
    This is an approximation, which supposes continuous rows (without spacings between tables) and neglects the edge effects. This should be used when the sheds are rather long with respect to their width.
  • Unlimited sun-shields: is equivalent to Unlimited sheds for arrays of sun-shields on a façade (i.e : taking mutual shadings into account without defining a 3D scene). As with Unlimited sheds, the edge effects are neglected. The yield optimization of sun-shield systems is rather difficult, as the shadings are very important even in the middle of the day. It is only suited for perfectly south-oriented façades.
  • Unlimited trackers: is also equivalent to Unlimited sheds, with the similar advantages and drawbacks. It supposes a horizontal axis, which is usually oriented close to the North/South direction. Therefore these trackers follow the sun from east (morning) to west (evening). Unlimited trackers may use the Backtracking control strategy
  • Tracking, tilted axis: the axis orientation (tilt and azimuth) should be explicitly defined. The axis azimuth will usually be around 0, i.e., near the south in northern hemisphere. The rotation angle is called Phi (value 0 when plane azimuth = axis azimuth), with the same sign convention as for plane azimuth. Mechanical limits on the Phi stroke are required.
  • Tracking, horizontal N-S axis: this is the particular case when Tilt = 0. This is the usual configuration of most big systems involving trackers: if the axis is very long, it is necessarily horizontal. When installed on a hill, the axis may follow the terrain; in this case you should use the option "Tracking, tilted axis".
  • Tracking, horizontal E-W axis: this would follow the height of the sun in the southern direction, i.e. mainly the seasonal variations. This is available in PVsyst, but not pertinent for PV systems. This should never be used except in very special situations. Stroke limits should be defined (here Phi = plane tilt), from lower limit (minimum -90° = vertical north) to upper limit (maximum 90° = vertical south).
  • Tracking, vertical axis: the collector is kept at a fixed tilt, but rotating according to the sun azimuth. This configuration may be used at high latitudes, where the sun height is rather low on horizon, but the azimuth may have a big variation in summer. This is also usable with "dish" arrangements, when a big rotating support holds several rows of modules; or equivalently a floating tracking system following the sun azimuth. This particular case is made possible as the rotating axis of one row may be displaced with respect to the collector.
  • Tracking sun-shields: is a particular case of the Tracking, horizontal E-W axis. It may yield solutions causing difficult optimization between sun protection and PV production. For full efficiency, this should involve a Backtracking control strategy.
  • Tracking, two axes: this stays permanently perpendicular to the sun's rays. The mechanical limit angles of the tracking device (in tilt and azimuth) should be defined and are taken into account during the simulation.
  • Tracking, two axis with frame: the collectors are fixed and rotating within a frame, itself rotating. This is therefore a variant of the 2-axis tracking. Two configurations are available: a frame with North-South axis (and collectors with tracking tilt) or a frame with East-West axis (and collectors tracking according to the sun azimuth).

Calculation and Limitations

The tracking strategy in computed using the solar geometry (so-called "astronomical" algorithms), in order to minimize the incidence angle in terms of the sun's position.

With horizontal or tilted axis trackers, you can also use a strategy that optimizes the irradiance on the tracker. See Tracking strategies.

For sheds, please carefully see the special combination of "Orientation" option and "Near shadings" treatment

Also, be aware that with tracking planes, the mutual shadings of several neighbour tracking units can become very important at extreme angles (see the shed optimization tool with very tilted collector plane). The collector's spacing should usually be very large, so that the horizontal space used is rather low (lower GCR).

The Backtracking control strategy that adjusts the orientation to avoid mutual shadings at any time, may help optimize the electrical shading effects. However, even if there is no mutual shadings for the beam component, the mutual shading on the diffuse and albedo components should be evaluated. This requires the construction of the 3D shading or use of unlimited trackers.