The growing interest in the PV market has made the reliability and efficiency of photovoltaic systems the leading topics of investors around the world. Following this lead, in October, the International Energy Agency (IEA) published a Report on the operation and maintenance of photovoltaic panels in seven different climate zones. Comprehensive guidelines, based on detailed analyses, allow for an individualized approach to service and maintenance activities in various conditions, including extreme ones. The report is based on measurement data from photovoltaic systems around the world. They were used to compare possible methods of monitoring, operation, and estimating the efficiency and life span of the panels. The following international standards have been adopted as the basis for operational and maintenance activities:
IEC TS 63049
Appropriate use of this knowledge will allow comprehensive user support. It will be possible by standardizing activities and introducing intelligent solutions.
What are the main purposes of a report writing?
As is well known, photovoltaics has so far been regarded as a low-maintenance solution. Attention was paid only to the decrease in the installation efficiency caused by long-term operation. However, another very important aspect was omitted – climatic conditions, which significantly affect the frequency of failures and the degradation process. This is because both the assembly method and the materials used react differently to external factors, such as temperature, humidity, UV light, rain, wind, etc. The lack of appropriate knowledge and regulation in this area not only limits technological progress but also expose users to huge costs. In an ever-expanding market, it is critical to establish KPIs with relevant environmental characteristics. The text proposes three basic KPIs: Guaranteed Performance Ratio, Guaranteed plant availability, and Response Time. The introduction of the above standards and imposing them on operators will result in the fact that only trusted entities will remain on the market. They are characterized by a holistic approach to implemented investments.
Despite the standardization of the systems, each of them has its own unique characteristics that require different procedures and security standards. Hence the increased demand for maintenance activities characterized by an innovative and fully individualized approach. Due to this, the market striving for “predictive” solutions will be particularly open to partners with a flexible attitude. Previously, when the focus was only on initial maintenance and service, basic testing, preventive inspections and ad hoc corrective actions were performed. However, the obsolescence of modules and significant advances in analytics and artificial intelligence have placed more emphasis on the development of predictive monitoring methods. They will use historical data of the photovoltaic installation obtained from the monitoring system as well as data on environmental conditions. This will allow us to understand some general pattern of plant performance and behavior and to plan appropriate maintenance interventions. The report presents a classification of monitoring systems depending on the breadth of their application and measurement accuracy. According to the IEC61724 standard, the highest quality performance class includes: basic system performance assessment, performance warranty documentation, system loss analysis, grid interaction assessment, fault location, PV technology assessment and precise measurement of system degradation. On this basis, both the parameters and the analysis strategy should be clearly defined already at the design stage to take into account the relevant factors for integration with the photovoltaic installation. This allows tracking, apart from physical parameters, also synthetic parameters determined depending on the characteristics of the plant. Subsequent analysis should include statistical control of the data and assessment of trends in parameters, not specific values.
Despite the growing value of activities on photovoltaic systems, we cannot ignore the aspect of PV power forecasting, which is the basis for optimizing energy management and trading. The basic features of PV power forecasts, depending on the available data, include the forecast horizon, spatial and temporal resolution, and update frequency. In terms of methodology, three segments of forecasting methods have been distinguished so far (physical, statistical, based on artificial intelligence), which are often used in a hybrid way depending on the specificity of the installation. Classic examples of statistical methods and artificial intelligence include the use of artificial neural networks, neural fuzzy systems, support vector machines, hidden Markov models, and regression and autoregression analysis. Currently, the machine learning technique based on the use of data to model parameters and create self-learning patterns accounts for as much as 25% of PV power forecasting methods.
In order to develop an appropriate approach to individual conditions, the Köppen-Geiger Climate Classification was used, which describes five main climatic zones. However, due to the narrow description of the factors, the scheme was only the starting point for creating the final classification for the report.
This climatic zone needs to be assessed primarily in terms of flora and fauna. Small seasonal changes result in the year-round development of wildlife, which very often interferes with the construction of modules, causing mechanical damage. The specificity of these areas is also associated with the rapid development of industry and the resulting pollution.
HOT AND DRY CLIMATE
The regions are mostly desert, with low humidity and sparse vegetation. Extremely infrequent rainfall can cause soil erosion, which will negatively affect the foundation and durability of the installation. An additional challenge for monitoring systems is their extensive distribution.
DESERT CLIMATE AT HIGH ALTITUDE
The main challenges of this area are extreme levels of irradiation, temperature fluctuations and corrosion caused by salt and water condensation. Reducing the impact of these environmental factors will allow maximum use of the region’s solar potential.
HOT AND HUMID CLIMATE
Systems in these areas are primarily exposed to high temperatures and humidity. Frequent and sudden temperature changes have more serious degradation effects than daily fluctuations in desert areas. Additional threats such as pollution or fires have a similar genesis to those occurring in the temperate zone.
REGIONS AT RISK OF FLOOD
Systems in risk areas should be designed based on the history of flooding in the area. However, due to climate change, more and more installations will be affected. Potential damage can be divided into two types: from fast flowing water/impact and from immersion.
The force of the winds attributed to a tropical cyclone can lead to the tearing of the installation or numerous cracks in the structure (caused by strong wind pressure). Static and dynamic wind loads must be considered when designing the system, and additional wind tunnel testing must be performed.
A heavy snow load causes power generation to stop. This is due to limited light transmission to the cells and damage to the modules due to the high pressure of snow layers and icing of the system. On the other hand, snow can also have a positive effect on the energy generation process. It increases the ground albedo, which additionally increases with the angle of inclination of the module.
All the above data show that a well-designed installation is an extremely important aspect, but it does not guarantee a long life. A combination of top quality monitoring and maintenance practices is essential for photovoltaic systems to reach and exceed their full lifespan. But above all, it will be important to forecast, taking into account the climatic conditions prevailing within the module.