Main technical occurrences in small-scale photovoltaic systems

Looking to make available increasingly solid and secure real sampling data for the Brazilian photovoltaic solar energy market regarding after sales, we demonstrate in this article, a series of information gathered from the delivery of the post-sales subscription service (DNA Security), directly to end customers who own solar plants, who signal where we should allocate predictive and preventive efforts, as well as technical and educational guidelines for field maintenance teams.

To this end, we select and analyze 600 microgeneration solar plants up to 75 kW in the period of one year in different regions of Brazil, and we established some rules and standards so that the result would not be subject to external interference, such as the low technical quality of the project execution, and non-compliance with current standards to be observed.

Another established rule is that we would not analyze systems with different technologies and applications, therefore, all the projects analyzed have the characteristics listed below:

• On-grid systems;
• String inverters (multi strings);
• MPPT level tracking;
• Microgeneration systems;
• Rooftop installations;
• Layout with stringbox;
• Systems with communication via Wi-Fi;
• Poly/mono/mono-PERC/mono or bifacial modules.

That said, it is important to emphasize that all systems have active remote monitoring via monitoring platform from their respective inverter manufacturers, they also have a post-sales subscription contract that includes the issuance of invoice management and energy balance reports, this gives us clarity on the results to be compiled and shared. 

To organize the data, we listed the seven main occurrences noted and complained about.

occurrences

• Failure or defect in the inverter's AC circuit breaker;
• Loss of data/communication between inverter and Wi-Fi internet;
• Performance/energy generation lower than contracted;
• Infiltration in the roof used to fix the modules;
• Difficulty in understanding energy bills;
• Incorrect operation of the inverter;
• Others.

Based on this list the following proportions, observations and comments were recorded in the table below.

The two main occurrences most noted have direct impacts on customer expectation and satisfaction, since they deliver or demonstrate different results than expected at the end of a cycle (month). If added together, almost half of the customers observed have already had problems of this nature.

Projects of this size (microgeneration) in Brazil, suffer harsh penalties due to the deprofessionalization of the sector, where the workforce in general does not seek adequate qualifications, and every day new companies open offering design, installation, approval services, commissioning and others, forgetting the most important thing: knowledge of the cause.

The result of this is what this article portrays: inefficient projects, poorly informed, poorly guided clients, and frustrated about their solar energy investment. Technically speaking, these two main occurrences can be caused by different reasons:

1. Absence of prior technical visit to assess the site, possible installation layout, space limitations, entry pattern characteristics, cargo handling logistics (equipment), general interferences, structural analysis of the roof, among others;
2. Acquisition of pre-formatted equipment “kits” without technical feasibility analysis and without customization for the client’s particular realities, such as losses involved in the project (orientation, inclination, dirt, voltage drop, temperature, shading, etc.);
3. Failure to communicate assertively with the customer at the time of sale, promising “monthly energy generation” instead of an average annual performance, disregarding the fact that we work with an intermittent energy source that undergoes variations due to the climate, seasons, and unforeseen situations such as cold fronts and layers of hot air that completely alter the behavior or the absorption capacity of sunlight by photovoltaic solar modules, thus generating general dissatisfaction among the customer when in a specific month the energy generation is below that promised in the commercial proposal;
4. Lack of customer guidance regarding the communication system and inverter monitoring platform, making the customer's experience as a very difficult and dependent on constant calls to technical . Many customers even report never having been informed about the existence of a monitoring platform for their own solar system.

Regarding the third occurrence (difficulty in understanding information on energy bills), there is also a point to be made here: better preparation of after-sales teams that are focused on customer relationship and satisfaction.

Well-organized companies have defined processes and clear customer strategies for , monitoring and clarification.

No matter how complex they may seem at first, once well explained, invoices become predictable and easy to assimilate, since the information tends to be repeated, changing only the numerical part of each item.

As for the fourth position, the AC circuit breaker failures There may be several reasons, and each case must be analyzed on a case-by-case basis to reach an accurate and assertive diagnosis. However, with time and experience, we have been able to list the main causes, providing a warning to installation and maintenance teams.

In most cases of systems of the size we are dealing with, the circuit breakers do not exceed 200A, even so, just over 75% are below 80 A of nominal capacity, this information is valid to say that the majority of these circuit breakers are standard and conventional circuit breakers, which we see on a daily basis inside residential distribution s, DIN type thermomagnetic devices that offer thermal and magnetic protection.

Some characteristics of circuit breakers must always be observed from the design stage, such as: sizing based on the load to be installed and the conductors used, as well as the circuit breaker curve.

We will not go into this in depth, but for basic clarification, for each type of load the circuit breaker has a more or less adequate breaking curve, these curves are divided into some categories. The breaking curve is the time in which the circuit breaker s a certain electric current above its nominal current.

Circuit breakers can fail due to poor design sizing, neglect of some parameter to be considered in the voltage drop and conductivity equations of the cables to be used, due to internal manufacturing failure (which may be in the thermal protection provided by means of a bimetallic plate or in the magnetic protection provided by means of a metal coil and piston), among other factors.

There is a line of study and understanding that argues that none of these conventional circuit breakers are prepared or suitable for solar energy system installations.

This thesis is based mainly on the understanding that these devices were not designed to the supply of electrical current uninterruptedly for approximately 12 consecutive hours per day.

The penultimate occurrence is a general situation, since inadequate functioning can refer to many things.

However, in a more detailed internal analysis, we noticed that there is a pattern, a repetition in the complaints, and it concerns the customer's visual perception in relation to the inverter display and the inconvenience caused when receiving or viewing alert messages on monitoring platforms and emails.

The reality is that most of these alerts are transient, temporary, and generally relate to a low DC voltage at the start of the equipment, either at the beginning of the day or at the end of it. Likewise, alerts caused by fluctuating AC voltage levels leaving the equipment temporarily out of sync with the distribution grid. These complaints could be avoided with more proactive and effective after-sales and customer service, informing (and teaching) that not all equipment alarms are related to defects.

Finally, an extremely sensitive issue, which when it occurs can cause great damage. Leaks, when they occur due to carelessness on the part of professionals on the roof, are almost always noticed during the first heavy rain after the installation of the solar modules, and if prompt intervention is not carried out, the customer's assets may suffer damage that is difficult to repair.

These events can be mitigated in a number of ways, firstly by always carrying out a visual pre-inspection of the roof, understanding the construction history in a conversation with the owner, analyzing the type of tile or slab in question, the damage or faults already existing, and in more complex cases or cases of greater uncertainty about the capacity to excess weight, a study must be carried out to obtain a structural report issued by a professional with the competence to do so.

We can conclude that most incidents can be reduced when there is adequate, proactive, agile and assertive after-sales service (whether technical or commercial). Providing the customer with the correct information and knowledge about their own solar investment is the way to go. Likewise, creating a mindset in integrating companies that they need qualification training, improvement and constant recycling is also essential.

We need to forces so that our sector moves towards company certification and employee professionalization. There is no other way to deliver satisfactory results after sales other than this.  

Read also

• Introduction to after-sales culture and customer vision

The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.