<< Click to Display Table of Contents >> Navigation:  Project design > Plane orientation > Orientation optimization

This is a tool aiming to show the best suited orientation for a PV system, or what you loose when not optimally oriented.

The Transposition Factor is the ratio of the incident irradiation on the plane, to the horizontal irradiation. I.e. what you gain (or loose) when tilting the collector plane.

There are 2 tools in PVsyst for doing this:

Detailed optimizing tool

In "Tools" > "Transposition factor", you have a complete and accurate calculation using full Hourly meteo data over one year.

This computes 475 annual FT calculations table for a grid of tilts and azimuth plane orientations. Then, the tool shows  the optimal orientation, and curves of "iso-transposition" orientations for different transposition factors.

Each curve is also labeled with the amount you loose with respect to the optimal orientation.  

Now please observe that the optimization of the orientation depends on the planned use for the PV energy.

Therefore this tool gives the possibility of choosing the optimizing period:  Year, Winter, Summer, or chosen months.

Moreover, the optimization may depend on specific far-shading conditions (mountains): you can define a horizon line, and this will usually result in an azimuth displacement.

Now you can observe that the summer optimization has usually a flat optimum: you have high freedom for adjusting the plane orientation without loosing much, especially when the tilt is low. This means also that the optimum can be displaced towards east or west, with very low differences in absolute values. With hourly measured data, the optimal azimuth may be displaced because specific meteo behaviors like frequent fogs in the morning, storms in the evening, etc.  

As a contrary, specific optimizations, for example in winter, are much more marked (sharp distributions around maximum): the iso-transposition curves are closer to each other, you have less freedom for a good orientation,.  

Quick optimizing tool in the "Orientation" part

When choosing the (fixed) plane orientation, an information panel indicates the corresponding Transposition Factor, the difference (loss) with respect to the optimum orientation, and the available irradiation on this tilted plane.

Clicking the "Show optimization"  button, you can see a graph of the Transposition Factor as a function of the plane tilt and azimuth. These graphs also indicate your actual choice by a violet dot on the curves, showing at once where you are positioned with respect to the optimum.