As we said in the article “Performance Ratio – PR”, at a given location, the electrical output depends on the power losses occurring in the facility. The ASIF (Photovoltaic Industry Association) made a general estimate, provided the most likely PR 70%.
This table indicates that losses are inevitable (PR optimum 90%). However, it can influence the design because the values vary considerably. Today, cases with a PR less than 70% are not generally considered interesting from an economic standpoint.
The loss of a photovoltaic system are:
- Tolerance of the module. The rated power may vary from one module to another. There are brands on the market that guarantee a tolerance of + / – 5%.
- Losses over time. Photovoltaic cells degrade very slowly and progressively. In fact, all quality brands with a warranty of 90% power for the first 12 years, and 80% to 25 years.
- Mismatch. Not all motherboards have exactly the same power, it is necessary to arrange for not limiting the intensity of a string (series of modules) to the lower current.
- Spectral. For the tilt and orientation of the modules, the radiation may not always be perpendicular.
- Dust and dirt.
- Increasing cell temperature. The power module is calculated to temperature conditions of 25 º, but in reality it is much higher. Approximately 0.5% is lost power for every degree above 25 º.
- Shading. Shadows are important. To avoid.
- Cable voltage drops d.c. cable and a.c.
- Yield Investor / Maximum Power Point. There are brands that guarantee investors a return of + / – 5%.
- Unavailability due to maintenance. Responsiveness of the maintenance company to a possible malfunction.
In every one of these games and we played some other way. That is what is a quality issue.
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