IEP - Instituto Electrot├ęcnico Portugu├¬s

Associates Area

Inspection for preventive maintenance

 

We are all aware that reducing the emission of greenhouse gases into the atmosphere is a crucial measure to keep the planet habitable. In this reasoning orientation, the progressive incorporation of renewable energy sources is in itself a decisive contribution to this objective, namely those that imply the production of electric energy. In this context, the great growth in number and in the extension of photovoltaic and wind farms, as well as of large water projects installed throughout the world, constitute an extremely important contribution to this great global undertaking.


In 2017, Portugal was at the top of the list of countries whose production of electricity came from renewable sources, namely wind and photovoltaic. Thus, in this framework, we would like to highlight the strong development of photovoltaic production technologies with absolutely consistent economies of scale, which makes the large-scale construction of this kind of power plants with the capacity to supply network (without subsidised feed-in tariffs). For this same reason, it should be taken into account that optimizing the performance of these infrastructures is absolutely critical.

 

Effectively, photovoltaic modules naturally have energy efficiency losses of approximately 1% per year. But surely there are other exogenous factors, such as poor installation conditions, poor transport conditioning to the site of installation and, obviously, constructive problems of the solar modules themselves, which can accelerate their degradation over the useful life. For the reasons given here, the well concerted monitoring of the performance of the solar modules themselves is an extremely important element to validate if the evolution of this same performance is actually expected.


In the framework identified here, we recommend the systematic development of validation tests of the performance of the solar modules through measurements (in STD conditions) of "I-V" curves (flash-test) and electroluminescence tests. This group of tests allows to measure the evolution of the performance / efficiency of the solar modules, as well as to inquire about the possible causes of the eventual unusual degradation.


Obviously, there are also other critical elements commonly known as "BoS" (Balance-of-System), namely, bench supports and tracking systems, wiring and electrical protection elements (string boxes), inverters, or even energy injection conditions in the power grid, without the quality of which the overall performance of the system will be seriously compromised. In this context, a third party, an independent entity from the construction / maintenance service provider, who, with the appropriate human and technical tools, will be able to assess the state of the park as a whole is important.

 

This entity can develop from thermographic inspections to photovoltaic modules, as well as to the BoS, through electrical safety inspections (ground resistances, fuse sizing in strings boxes, transformers and DC and AC wiring). In this way, through the report issued, the construction / maintenance team can be more incisive in the key points to intervene, managing to maximize the full potential of the photovoltaic installation.


It is also worth noting that in parks with an installed capacity of more than 1MWp, it is already possible to make global thermographic inspections of photovoltaic modules in good time, gathering important information to perform an effective maintenance. A regular and detailed inspection by drone, allows for the identification, location and characterization of defects permitting the monitoring of the evolution of these, with unequalled precision and otherwise unviable.


We note once again that the regular (every two years) intervention of an inspection / audit team, in close collaboration with the maintenance personnel, will provide a concise assessment of the performance of the photovoltaic parks. The inspection allows for the maintenance team to focus on the essential, evaluating the priorities of defect corrections, depending on the degree of severity of the found defects. In this way, an independent third-party entity cooperates with developers and maintenance teams in order to maximize the profitability of each solar park, optimizing production, increasing its useful life and, consequently, increasing the company's financial return of investment.

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