The maintenance information required for the grid-connected photovoltaic system is a general feature, and more importantly, it should be based on the owner’s manual and the manufacturer’s recommendations for equipment maintenance. Some simple maintenance work can be carried out by the owner, but most of the maintenance work should be carried out by qualified photovoltaic technicians. Many regions require electrical system engineering (such as photovoltaic systems) to be tested every few years, and installers should be familiar with such local regulations.
The maintenance task contract is generally included in the installation project package: the company has to come back once or twice a year to check and test the system to ensure that it is working properly. The results of these inspections should be recorded in the maintenance schedule and the equipment operation log delivered to the system owner before system commissioning. In addition, the contractor of the maintenance task shall keep a record of the service and repair work, and a copy of it must be retained by the system owner. In the photovoltaic industry, it is important to keep records properly, because the products used have a long warranty period. Logs are particularly useful because historical information will show changes over time, deviations from specifications, and errors that have occurred or are occurring. The most important aspect of maintenance work is performance monitoring, which ensures that problems can be identified when they occur, and errors can be corrected before serious damage occurs (for example, occlusion can lead to hot shifts). It can also provide users with full-year system performance and provide help for future performance comparisons.
1. Maintenance of photovoltaic array
Photovoltaic arrays have no moving parts, so they can usually operate without problems for many years. However, regular maintenance is still very important to ensure the safe and efficient work of photovoltaic arrays. Routine maintenance work includes tilting the photovoltaic module and performing mechanical and electrical inspections. It is recommended that only properly trained service personnel perform PV module maintenance.
Photovoltaic modules are generally self-cleaning; rainwater will wash away all the dust, but light pollution, bird droppings or fallen leaves need to be treated. It is not allowed to use solvents to clean the photovoltaic array. Clean water containing a small amount of soap powder is sufficient. If the components meet the corresponding standards, the snow on the photovoltaic array is generally not a problem; however, if a large amount of snow accumulates for a long time, the owner may wish to remove the snow, as this will obscure the array and affect performance. Before the system owner intends to clean the photovoltaic array himself, he should be informed and consider the danger of working at heights.
It is also important to check that the PV array is not blocked by any trees, including trees that have grown up after the installation of the system; occasional pruning may be required. Trees on neighbors’ assets may also obscure the array. Laws in some areas protect sunlight passability, but there are no similar laws in many areas. It is very important to discuss this issue with your neighbors before installing the system.
Maintenance work performed by qualified photovoltaic technicians usually includes inspection of the support structure to find signs of corrosion that may cause mechanical failure; the attachment points to the roof should also be inspected to ensure that these attachment points are still watertight. Cables and wiring should also be checked to ensure that they are still mechanically sound and weatherproof.
Monitoring photovoltaic systems is also a common method. Although the output power usually decreases over a long period of time, there is a big difference between the measured value and the expected value, indicating that there is a problem that needs to be solved. The most common form of monitoring is to check the output voltage, current and other electrical parameters, which can compare the expected value of the design plan with the measured value during the trial operation, so as to determine whether there is a problem. Many modern inverters include monitoring functions, or external monitoring devices can be used. In some cases, environmental parameters (such as temperature) can also be measured, because this helps designers see the correlation between environmental conditions and system output. It is also possible to monitor the component temperature to ensure that it is within the designed system temperature range.
For display needs, monitoring data must have a certain display method. The basic monitoring system can include small LED displays and indicator lights on the component to check if the component user manual is violated. Most modern inverters have small displays that display measured data, and many inverters can be wirelessly connected to remote displays (such as computers or iPhones). Then, the recorded monitoring information can show long-term performance trends. Users are generally interested in this. They want to know how much power the system outputs and how much electricity bills are saved (or how much money they make under the condition of enjoying the feed-in tariff).
The array maintenance table should be included in the log.
2. Maintenance of the inverter
The maintenance of the inverter generally involves:
Keep the unit clean: clean the container and all vents when needed.
· Make sure that the unit is not invaded by insects and spiders.
·Ensure that all electrical connections are kept clean and tight.
·Check the operation of the inverter.
Inverter maintenance operations and basic repair instructions may be listed in the manual. Any maintenance work on the inverter should be recorded in the system log. Maintenance (except cleaning) and repair of the inverter should be performed by suitably qualified technicians; the system owner should not attempt to perform these repairs.
3. System integrity
The above-mentioned maintenance and inspection work is related to the various components of the system. Since these components work as a system, they need to be interconnected by cables. Therefore, during any equipment maintenance period, it is important to be able to visually inspect the entire system to ensure that there is no potential threat to its performance and/or safe operation. This involves checking and testing various components, including isolation devices, circuit breakers, photovoltaic combiner boxes and wiring.