7. Case study

#### 7.1 Photovoltaic backup systems

In order to better study the impact of the two types of maintenance on the system, Figure 12 shows the frequent preventive and corrective maintenance operations carried out on installed PV backup systems during the period 2012–2015, which were kindly followed.

Figure 12(a) presents the number of preventive and corrective interventions realized on one site within a period of 4 years. This illustration shows the importance of preventive maintenance on PV systems. In effect, the more preventive maintenance are done, the less there are corrective operation realized. It is the case for the years 1, 3, and 4. To estimate the element lifetime before failure, the exploitation of the maintenance files indicated that 25 batteries were damaged on the 82 installed as shown in Figure 12(b); thus, batteries contributed to 64.9% of the breakdowns

Figure 12.

(a) Number of corrective and preventive maintenance per year on a PV systems and (b) recorded breakdowns per elements.

Figure 14.

Figure 15.

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Breakdown tree diagram for detecting breakdowns in a PV system.

(a) Inverters faults versus causes of breakdown and (b) PV module breakdowns versus causes.

On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon

DOI: http://dx.doi.org/10.5772/intechopen.83730

generated during this studying period. This result shows also that batteries are the most sensitive elements of the PV system charge controllers, cables, and inverters, which contribute, respectively, 13, 8.3, and 5.5% of the breakdown registered.

#### 7.1.1 The causes of breakdown at each element

#### 7.1.1.1 Causes of the battery and cable breakdown

Batteries being one of the vulnerable elements of a PV system, the direct causes of their breakdown are due to late interventions and aging. Figure 13(a) shows the causes of the breakdown of batteries. It appears that five battery breakdowns were caused by the lack of control of the good functioning of charge controllers, and four damaged batteries were due to a late refill of the electrolyte. It has also been noticed that the bad sizing of the generator system and the climatic factors (temperature, humidity) which were not adapted to the good functioning of the batteries cause their breakdown. The most frequently observed breakdown causes of the cables are (Figure 13(b)) cable break age and corrosion which lead to short circuits and worn out cables, and great length cables can also cause the voltage drop and energy losses at the end of the system.

#### 7.1.1.2 Causes at the level of the inverter and PV module

Breakdown on inverters is frequently caused by overvoltage (Figure 14(a))). They have as origin the nonfunctioning of charge controllers and the frequent interruption of electricity of the network. For PV modules the most frequent causes

On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon DOI: http://dx.doi.org/10.5772/intechopen.83730

Figure 14. (a) Inverters faults versus causes of breakdown and (b) PV module breakdowns versus causes.

Figure 15. Breakdown tree diagram for detecting breakdowns in a PV system.

generated during this studying period. This result shows also that batteries are the most sensitive elements of the PV system charge controllers, cables, and inverters, which contribute, respectively, 13, 8.3, and 5.5% of the breakdown registered.

(a) Number of corrective and preventive maintenance per year on a PV systems and (b) recorded breakdowns

Batteries being one of the vulnerable elements of a PV system, the direct causes of their breakdown are due to late interventions and aging. Figure 13(a) shows the causes of the breakdown of batteries. It appears that five battery breakdowns were caused by the lack of control of the good functioning of charge controllers, and four damaged batteries were due to a late refill of the electrolyte. It has also been noticed that the bad sizing of the generator system and the climatic factors (temperature, humidity) which were not adapted to the good functioning of the batteries cause their breakdown. The most frequently observed breakdown causes of the cables are (Figure 13(b)) cable break age and corrosion which lead to short circuits and worn out cables, and great length cables can also cause the voltage drop and energy losses at the end of the system.

Breakdown on inverters is frequently caused by overvoltage (Figure 14(a))). They have as origin the nonfunctioning of charge controllers and the frequent interruption of electricity of the network. For PV modules the most frequent causes

7.1.1 The causes of breakdown at each element

Figure 12.

Maintenance Management

per elements.

7.1.1.1 Causes of the battery and cable breakdown

7.1.1.2 Causes at the level of the inverter and PV module

(a) Damaged batteries and their causes and (b) cables breakdown versus causes.

Figure 13.

126

are Figure 14(b): dust deposit, bad fixing on their supports, and accidental cracking. The first two causes which do not lead to the stop of the system decrease the efficiency of the system (output energy), while the third cause leads to the stop of the system which necessarily needs a replacement.
