This lesson is a guide for PV professionals and system owners. The lesson will walk you through the basic understanding of the commissioning, operation and maintenance, and monitoring topics that relate to PV systems. This lesson prepares solar professionals to become PV system operators. Similar to any other construction that exists, O&M and monitoring are pivotal aspects of PV systems, and they are key components in driving the PV system to succeed under different operating conditions. Understanding the main concepts of O&M and system monitoring prolong the operation of PV systems and guarantee expected energy production throughout the systems' lifetimes.
At the successful completion of this lesson, students should be able to:
Lesson 11 will take us one week to complete. Please refer to the Calendar in Canvas for specific timeframes and due dates. Specific directions for assignments below can be found within this lesson and/or in Canvas.
If you have lesson-specific questions, please feel free to post to the Lesson 11 Questions discussion forum in Canvas. While you are there, feel free to post your own responses if you, too, are able to help a classmate with a question. If you have questions about the overall course or wish to share and discuss any "extra" course related commentary (interesting articles, etc.), please feel free to post to the General Questions and Discussion forum.
After the installation of any PV system is completed and the inspection is done, the system will be ready to be plugged to the grid to transfer energy. That process is referred to as Commissioning the system. At the same time, the installer will hand the responsibilities to the owner or operator of the system.
There are steps and requirements to commissioning PV systems that vary depending on system size and complexity of design. However, there are general guidelines that apply to most systems.
The system should be checked thoroughly before the commissioning starts.
A highlight of the main electrical items to consider:
A highlight of the main mechanical and structural items to consider:
Other safety items to consider:
When intending to start the PV system the first time, the procedure starts at the array and ends at the point of connection. This will reduce hazards and make the diagnostic and testing of subsystems easier in case there is a problem in the installation.
PV commissioning is a procedure that requires a lot of attention to details. Solar professionals are encouraged to refer to the required reading "PV System Commissioning" available on the overview page of this lesson.
Maximizing the performance of any PV system is one of the priorities of owners and integrators. This can be done with routine maintenance to ensure optimal operation conditions. Since PV systems can be owned by individuals, organizations, or utilities, there must be a set of practical guidelines to operate and maintain these systems to minimize downtimes and maximize the return on investment. The maintenance requirements vary depending on the system size, installation type, and locations. For example, stand-alone systems require more maintenance consideration due to the addition of batteries. Furthermore, manufacturers may provide maintenance guidance or procedure for components.
There are several major O&M approaches that exist in the market today, and each comes with tradeoffs. In simple words, each approach aims to achieve the three key goals of an effective O&M:
There are three main strategies for maintenance: Preventative Maintenance, Corrective or Reactive Maintenance, and Condition-based Maintenance.
This strategy includes routine inspection and servicing of equipment to prevent breakdowns and unnecessary production losses. PM strategies can lower the probability of unplanned PV system downtime. However, the upfront costs associated with PM programs are moderate and requires more labor time, and the increased inspection and maintenance activity contribute to site wear and tear and perversely expedite system malfunctions.
This strategy addresses equipment breakdowns after their occurrence to mitigate unplanned downtime. This strategy allows for low upfront costs, but it brings with it a higher risk of component failure and higher costs on the back end ( negotiating warranty terms). A certain amount of reactive maintenance will be necessary over the system lifetime, but this strategy can be minimized if more proactive PM and condition-based maintenance (CBM) strategies are adopted.
This strategy uses real-time data to prioritize and optimize maintenance and resources and can be done through third party integrators and turnkey providers. Different CBM regimes have been developed by third parties to offer greater O&M efficiency. However, this comes with a high upfront cost due to communication and monitoring software and hardware requirements.
In general, most PV systems share basic maintenance elements such as modules, inverters, charge controllers, and batteries.
A thorough inspection of PV modules can be done visually by the owner or installers. Main signs to look for when inspecting a PV system include:
As we learned in lesson 2, shading can significantly reduce the electrical output of PV array. Even after a careful site evaluation is performed before installing the system, a routine maintenance is recommended to avoid:
Batteries are considered one of the most maintenance intensive components in the PV system. We discussed in lesson 4 that lead-acid batteries are still widely used in PV systems and a special maintenance attention is needed. A careful consideration and review of the manufacturer’s maintenance recommendations is important to ensure safety on the site.
Besides visual inspections of inverters, chargers, transformers, and all other electrical equipment; there are other industry tools that can be used to find the weak points of the system. An infrared (IR) thermometer can be used to find the points where higher temperatures occur, such as circuit breakers, terminals, wires, and others.
A checklist of all required maintenance tasks and their recommended intervals to ensure best economic scheduling is referred to as a maintenance plan. The intervals can vary according to the site condition and system type. For example, a PV array installed in the desert requires more frequent scheduled cleaning of modules due to dust and soil accumulation.
An example of the O&M is shown in the Solar Operations and Maintenance videos produced by the Northern Mid-Atlantic Solar Education and Resource Center, part of The Pennsylvania State University. (The link is located under "Recommended Resources" on the Overview page.)
What is the main cause of system downtime in any PV system?
ANSWER: Inverters
More information about the recommended maintenance strategy practices in terms of frequency for main elements and main causes of downtime are available for students in Table 3 and Figure 2 on the EPRI report on “Addressing Solar Photovoltaic Operations and Maintenance Challenges: A Survey of Current Knowledge and Practices” posted on the Overview page of this lesson.
PV systems consist of different components to transfer energy. Measuring the electrical parameters at certain intervals can help gather more information about system operating status and alert users to possible problems. As we discussed earlier, measuring the output of the system is essential for production-based financial incentives offered by federal and local agencies.
The traditional monitoring method entails simply comparing actual energy generation to that predicted from the simulation software. The advantage of this approach is simplicity, affordability, and reliability. There are multiple levels at which a PV system can be monitored. Depending on system size and type, they can be classified as:
Inverter-level AC and DC monitoring offers insights into an inverter’s status, given the strategic location of the inverter to monitor the performance of the PV system. Nowadays, most inverter manufacturers embed their devices with monitoring functionality.
Going a level deeper into the system, array monitoring involves information from DC circuits located in various sections of a PV array.
A little closer to the modules, string level monitoring narrows the focus even further to individual strings of modules.
Once we reach the module, Micro Inverter Level Monitoring is installed at the PV module level. They are more common in smaller systems than large commercial or utility scale.
An example of monitoring is shown in the video (22:47) produced by the Northern Mid-Atlantic Solar Education and Resource Center, part of The Pennsylvania State University.
Is micro inverter monitoring level suitable for utility scale PV systems?
ANSWER: No, due to the large number of modules. String and Inverter level are more feasible.
Activity | Details |
---|---|
Assignment | Post original entry: In this lesson, we covered PV systems monitoring concepts. Based on previous discussions, we learned that PV systems classification can include more specific market sector, such as:
Post comments: Respond to two different opinions of others' posts. (For example, if you choose Option 1, you need to respond to one post for Option 2 and another post for Option 3 or 4.) |
Requirements, Submission Instructions, and Grading | For more detailed instructions about the discussion component of this course, including how you will be graded, please visit the Discussion Activity [9] page. |
This week, you will begin working on your Final Project. This will be a two-week project.
Activity | Details |
---|---|
Assignment | This final project will highlight the main concepts we discussed in the class. The questions are designed to evaluate your understanding of the basic PV system design principles and the impact that the additional PV might have on the utility grid. Visit the Final Project [10] page for the complete details of this assignment. Note: You will not be submitting this project within this lesson. You will be submitting the entire project at the end of Lesson 12. |
Let's revisit the scenarios from the beginning of the this lesson. By the end of this lesson, you should be able to communicate well with the utility personnel to insure that safe commissioning steps and procedures are followed before starting the PV system. Furthermore, you should be able to address the main O&M and monitoring questions the client asked at the beginning of this lesson. At this point in the class, our solar professionals are loaded with all basic information for design and installation of any PV systems with different sizes and types.
Being a solar professional requires a broad understanding of technologies and strategies in addition to solar design and installation knowledge such as: project management, financial analysis, communication, maintenance scheduling, monitoring networks and communication for data acquisition systems, and the list goes on.
In the next lesson, we will wrap up our class by discussing the impact of PV systems on the utility grid. As more PV are being added to the grid, there must be technical challenges to consider and understand when dealing with utilities to better negotiate and understand their requirements. So stay tuned!! See you next week.
You have reached the end of this lesson. Before you move to the next lesson, double-check the list on the first page of the lesson to make sure you have completed all of the requirements listed there.
Links
[1] http://assets.fiercemarkets.net/public/smartgridnews/1021496AddressingPVOaMChallenges7-2010_1_.pdf
[2] http://www.solarabcs.org/about/publications/reports/operations-maintenance/pdfs/SolarABCs-35-2013.pdf
[3] http://solarprofessional.com/articles/design-installation/pv-system-commissioning?v=disable_pagination
[4] http://prod.sandia.gov/techlib/access-control.cgi/2016/160649r.pdf
[5] http://energy.sandia.gov/wp-content/gallery/uploads/dlm_uploads/SAND2014_20612_PVROM.pdf
[6] http://www.nrel.gov/docs/fy15osti/63235.pdf
[7] https://smartenergyacademy.psu.edu/solar/open-education-resources#OandM
[8] http://www.solarcenter.psu.edu
[9] https://www.e-education.psu.edu/ae868/890
[10] https://www.e-education.psu.edu/ae868/974