Manuel Castillo (QPV), a solar industry specialist, describes the importance of quality control of PV systems with age.
What does quality control consist of in general?
A quality control system is designed to validate the construction specifications of the photovoltaic installation. It compares actual performance with the expected performance based on the technical characteristics of each component of the whole plant.
To capture the characteristics of the installed plant components, high-precision measurements are taken and then compared against patterns calibrated from other installations and performance data. These measurements include technical parameters such as maximum power, efficiency, thermal behaviour, etc. Once we know them, we are able to compare them with the performance specifications provided by the manufacturers. We can seek replacements or compensation if they are lower than expected. Productivity studies can also be updated with the elements actually installed in the plant. Initial performance studies or expectations are carried out and compared to the specifications provided by the manufacturer. Such field measurements have greater precision and reflect what is actually being achieved after installation.
In addition, a visual and document inspection of the installed elements and the final construction is also conducted. Problems at the regulatory level or bad practices that may degrade or put the operation at risk are identified.
What issues can quality control prevent or reduce?
A range of problems can be avoided by a diligent quality control procedures. The health of the photovoltaic modules is analysed in detail during the process. In the case of low productivity, a complaint can be made to the manufacturer, and replacements or compensation can be requested. The quality of the construction is also checked in detail and improvements or replacements can be claimed from the responsible party. In the same way, other less common issues, such as inverter efficiency, can be analysed identifying other potential problems.
How much money can potentially be saved with adequate inspections and how much could be lost without?
Giving concrete economic figures would involve analysing a specific project, but we can provide figures in relation to energy loss. A low nominal power in the modules can result in up to 5% energy loss in extreme cases, which is an amount that considerably lengthens the return on investment.
Other problems affect the lifetime of the facility, and thus, force a re-investment in the installation, causing an economic loss. For example, issues with modules can lead to accelerated degradation or failure in their operation, forcing their replacement. Similarly, problems in the construction process could result in poor insulation or installations requiring reinvestment a few years after commissioning, as well as possible safety risks.
How often should quality control be conducted?
A complete quality control of the plant is usually carried out at two points in time: at the end of construction or at a purchase and sale transaction. In the first case, quality control validates the entire process, from equipment procurement to commissioning. In the second case, it is a way for each party in the process to understand the current condition of the asset that is being transferred.
Partial quality control can also be carried out at other points in the life of the plant, focusing on one aspect where an operational problem is suspected rather than reviewing the whole installation.
What are common sources of problems for small solar installations used in the AURORA project?
The main problems are usually related to the health of the modules and the quality of the construction. It is common in small projects for modules to have lower power ratings than those specified by the manufacturer, as they are not inspected with the same rigour adopted for large power plants. Inspection of insulation, wiring routing, structural quality and many other factors in the construction process are key to avoiding operational problems and achieving long-lived installations.
How does the location influence the type of quality control and the frequency? How can this apply to the diverse sites used in the AURORA project and any twinning universities?
Location has little influence on the overall quality control processes which will simply take account of the different local legal obligations. The characterisation of equipment is not influenced, as it is directly linked to technology. The construction may differ to meet local regulations and the installation itself will be constructed with different specifications. The quality control process will note these differences, and ensure compliance with local regulations.
Can quality control be undertaken by the owners of the installation or general users using a checklist provided by QPV after the installation?
Quality control procedures are associated with certain international standards, usually IEC standards. In theory, these are public, and a person with sufficient knowledge of the technology can perform part of the quality control.
In practice, it is more complicated. These are complex procedures that require a lot of experience and a strict methodology to ensure performance standards are correctly assessed. In addition, many of the tests require specialised measuring equipment. It is therefore recommended that a full quality control process is carried out by a team of specialised engineers.
However, it is possible to follow good practice and perform certain simpler checks that can help to increase the life and quality of the installation. QPV has already published recommended checks for owners of solar installations to follow. As part of the AURORA project, we will continue to develop these guidelines, defining a methodology to help control the quality and performance of the installations installed as part of the AURORA project.