I used to train installers of (mostly residential) PV systems, and tell them that half of the quality of a PV system is in good materials and design, and the other half is in proper installation. For utility solar systems there is even a “third half” (if there is such a thing); maintenance!
A good measure of the quality of a PV plant is the Performance Ratio: it separates “the good, the bad and the ugly” solar systems from each other. Find out more in our whitepaper: 6 key influences that determine PV performance ratios.
Design of a solar plant
The terrain and the immediate environment often dictate the optimal layout of a solar plant. A wide, flat plain is much simpler than an undulating, hilly and rocky topography. Woods, hills, mountains or man-made structures may cause shadows at certain times, influencing the actual yield.
The range of solar elevation angles (declination) at the location during the year, and the seasons at which the optimum power output are required, determine the optimal tilt angle of fixed PV panels and the distance between the rows (due to shading by the row in front).
Good design will minimise these effects, and takes accessibility for maintenance into account as well.
Selection of components of a quality suited to the operating environment and the level of performance required is very important. PV panels, support structures, cables, inverters, transformers and monitoring equipment differ widely in these respects. So, components must be chosen according to the circumstances of the plant; high wind speeds, sand storms, snow, regular dew, salt build-up near the coast, low temperature panel output dependency in hot areas, corrosive pollutants in industrial areas.
Better quality and performance products will, in general, provide a more reliable long-term performance ratio, with lower uncertainty, that is acceptable to the key stakeholders; especially the investors, both short-term and long-term.
There are numerous cases in which something went seriously wrong during the installation phase of utility solar parks. At commissioning, it suddenly appears that:
- the distance between the panel rows is not 7 meters (as designed) but 6, or;
- the tilt of the rows is 15 degrees instead of 20 degrees, or;
- the orientation of the panels is 5 degrees out of the planned direction.
These are human errors that strongly affect the final (actual) yield compared to the reference (design) yield, and thus the Performance Ratio, in a manner for which it is very difficult to make corrections.
Many smaller mistakes, like wrongly interconnected panels or strings, can easily be fixed and will be corrected after installation and at commissioning.
Since the design and construction of a PV plant is a complex process with financing, environmental, technical, safety, procuring, planning and logistical viewpoints; professional, independent support is usually a requirement.
A technical advisor, specialised in solar parks, monitoring the entire process quality will be of great help; sometimes, several technical advisors are involved, representing different stakeholders such as investors, asset managers and EPCs.
To summarise; the theoretical PV plant performance is calculated during planning, design and choice of components, but the actual performance is largely determines by installation and commissioning. It is best to involve an independent technical advisor to keep track of the quality during these phases of the project