This article addresses the adjustment of the tilt of solar modules from an economic point of view. We know that it is possible to increase the tilt of photovoltaic modules by means of adjustment structures. This can provide greater energy gains, but is it economically viable in all cases?
In this study, two systems located in the Campinas region (SP) will be compared. The first with the modules flush with the roof, with a 10º inclination, and the second with the modules attached to a structure “adapted” to the slab, causing the modules to have an inclination of 23 degrees, optimal for the latitude in which it is located.
In both cases, the modules are positioned with the North azimuth. The tested system has 10 400 Wp modules connected to a 3,6 kW inverter, with a single MPPT input. To obtain the value of the energy generated in both situations, the PVSyst software will be used, with the losses of both systems (cabling, mismatch, temperature, etc.) identical. With the annual energy value calculated, we will use the cost of the compensable energy tariff for a B1 customer – residential, which is approximately R$0,65/kWh.
Choosing the inclination of photovoltaic modules in triangular structures
For the cost of the structure, we will use an average of values found on the market – around R$375 for the solution suitable for ceramic roofs and R$1355 for the triangle suitable for slabs that is being “adapted” to correct the inclination of the modules. Therefore, in this example the cost difference between the two systems is R$980.
Energy generation and economic gain
The table below shows the amount of energy generated in each of the systems:
A quick analysis for year 1 shows that the difference in energy generated is small, amounting to only R$196,30. To understand the impact on the economic performance of the system, we need to analyze the impact of the generation differences over the planned 25 years of operation. The year-by-year data was generated using the same software, assuming an inflation in energy costs of 2% per year, and is condensed in the table below.
Analyzed separately, the extra cost of the adapted structure will only be compensated around the fifth year. Over 25 years of operation, the system with the adapted structure will save R$6572 more than the system flush with the roof.
However, the difference in the cost of the structure (R$ 980), the increase in the expenditure of labor hours (1 additional day of work ~ R$ 150,00), which reduces the gain to R$5.442. In other words, in this case, there are financial gains when we analyze this adaptation.
However, close to the total energy savings of the system over the 25 years (R$ 115 thousand for the system close to the roof, R$ 121 thousand for the adapted structure) the benefit becomes insignificant, around 4,5%.
A solution to get around the problem that does not involve “adaptations”, especially in cases where the generation for the system close to the roof is not capable of delivering all the energy required, is to add one more module. The table below summarizes the generation of a system close to the roof with 1 more module, totaling 11 panels, and the same premises as in the previous cases.
Adding another 400 Wp module, considering a slightly larger structure, costs around R$800, which is cheaper than the cost of adapting the structure (R$980) and brings a more advantageous financial return ( difference of R$7.000 over 25 years).
Conclusion
In addition to the low financial return, the recommendation not to install “adaptations” to correct the inclination of modules on roofs is directly linked to the issue of safety.
Modules flush with the roof are much less exposed to pull-out effects caused by winds. The adapted structure, even by its very nature, hardly follows the manufacturer's fixing recommendations and the resistance of the materials to the letter.
O Canal Solar has already reported several structures that collapsed due to the effect of winds or overload, conditions that are much more likely to occur if the natural slope of the roof is not respected. It is also possible to state that more complex installations, with “adjustments” and “adaptations” are more prone to assembly failures. The complexity of the solution, combined with the lack of an assembly standard or manual, leads to more errors, risks of loosening, calls for problem correction and unnecessary risks. Therefore, these adaptations on sloping roofs are not recommended.
Answers of 2
Hello, Mateus Vinturini.
Great work on your analysis.
I still have the following question: could you also add an extra advantage to the project without this adaptation, considering that your panels would suffer less loss of performance throughout their useful life due to the fact that they also produce less on average per panel? In other words, would they be subjected to less effort?
Good afternoon, how are you? If the panels have the minimum ventilation required by the manuals, there should be no significant difference in useful life.