The number of on-grid / off-grid solar photovoltaic (PV) systems is expected to increase dramatically over the coming years. As the industry matures and people use more and more solar energy, it will be very important not only to set up new solar power plants but also to maintain and operate the already installed solar plants to perform with maximum possible efficiency and reliability. Operation and maintenance of utility scale solar plants will be key factor deciding the success and failure of any project. As the plant becomes older, Operation and Maintenance (O&M) becomes more and more important for improving the performance of the plant.
With the increasing number of solar businesses in the country, determining a plan and budget for operations and maintenance (O & M) is fast becoming an essential in assessing the up -front costs estimation of a solar plant facility.
In this article, i am going to discuss some of the important aspects of Operation & Maintenance required for solar power plants be it small or large scale. I will be discussing the mechanical and electrical, as well as communication system needs of the PV plants. You can implement these maintenance strategies and operational models to maximize the output of your solar plant on daily basis.
Types of Maintenance
When it comes to maintenance like any other power plants or system in general we can formulate three types of maintenance.
Preventive Maintenance : In this type of maintenance programe we have to anticipate any future breakdowns , system failures that may happen in the future. And how we can avoid that? We can avoid those breakdowns by doing routine monitoring and inspection of all electrical and mechanical equipment and repairing and replacing them on time so as to prevent breakdowns and reduce energy yield losses at large. Preventive maintenance is a scheduled activity. You can devise a strategy to check and monitor the the individual parts like PV panels, panel mounting structures, cables and wires, batteries and inverters, junction boxes, system monitoring system etc and look for any defects in them. Once you find with any defects, then comes the corrective maintenance.
Corrective Maintenance: Corrective maintenance or breakdown Maintenance or reactive maintenance generally includes repair or replacement of defective unserviceable spare parts and equipments. This can only happen after the breakdown occurs due to defects and faulty parts. So this maintenance has to bear the burden of power losses.
Condition-Based Monitoring: It involves monitoring of equipment condition and plant operations on a real-time basis and addresses a potential problem at a very early stage to prevent downtime. This requires a robust plant performance monitoring system like SCADA.
What should you focus on?
A solar PV power plant has several components and each of the sub-system requires different O&M skillsets. A few of the sub-systems and their O&M requirements are mentioned below.
PV module panels are generally placed at a certain angle to the gropund and cover large area. They usually take the form of a canopy and hence are very prone to dust. If not cleaned regularly, the panels tend to accumulate dust on its surface and blocks the sun rays from getting absorbed by the cells.
The module panels basically have a glass/plastic cover which might break if heavy things fall on to that, so proper care has to be taken.
Panel Mounting structures
The panel mounting structures are made of anodized aluminium, which are quite strong to take the load of the panels. however care must be taken while designing the structure system for a large solar plant. The structue system alongwith the mounted panels must be able to withstand wind velocity upto 150 kmph.
Bending of the structures can happen due to the improper design. If left unaddressed, the bending can damage the modules.
Similarly, during rainy season, it has been observed that the top soil gets washed away due to improper drainage system. Caving of the foundation and the structures caused by improper compaction of the ground has also been observed. A pro-active O&M team can address this by visual inspection and take preventive action especially before rains.
Inverter is the most complicated component of the PV plant and can be called the heart of the system. Since Inverters are predominantly electronics devices, they need to be taken very high care due to the extreme hot, humid and dusty conditions of India. World over, the system downtime is very closely correlated to the inverter downtimes. In fact, in a study conducted in 2010 by US based Electric Power Research Institute, the number of breakdowns is the highest by inverters.
Apart from this, it is also important to periodically check the wiring and batteries, if used. Management of batteries is whole another topic. In India, rodents are known to cause damages to the underground cables and it is important to monitor this regularly. Earthing protection also needs to be checked often.
Most of the solar power plants are located in remote places with unreliable communication infrastructure. Most of the remote monitoring systems need an internet connection and in the absence of a reliable connection, there could be problems of lack of data logging for long periods of time. This makes it very difficult to diagnose and rectify problems in a timely manner.
The O&M personnel should have a very clear understanding of the warranty terms from the suppliers. They also need to know the type of defects or problems that are covered under warranty, the duration of the warranty and also the key personnel from the supplier with whom warranty claims can be taken up and enforced in a timely manner.
Spare Parts Inventory Management
The inventory management is critical because this could increase or decrease the cost of the O&M as well as the working capital requirement. It is also essential for the timely completion of the different types of maintenance. The O&M personnel should know very clearly the list of the spare parts available, their quantity at the site warehouse and the lead times for delivery of spare parts from the suppliers.
In our experience in India so far, we have come across some of the problems which are very severe.
- O&M budget – Typically, the O&M budgets are very limited for various reasons.
- Availability of water – Dust accumulation in India is very high and requires frequent cleaning. However, most of the plants are located in arid regions with very little availability of water.
- Skilled manpower – Since the O&M involves people who have the skills in electrical and electronics engineering, it is a challenging task to get people to move to such remote locations to work.
- Local labour – In many places, it is mandated that local villagers need to be employed for O&M. While this is a noble objective and also is important for the economic development of local communities, in some cases the locals form unions and demand wages that make the O&M cost to go very high.
- Theft – Theft of materials (even PV panels) is rampant in some parts of the country. This can be prevented by having a good security system and a good inventory management system.
- Documentation – In many plants, there is no robust remote monitoring system. Instead they have a basic SCADA system which provides real-time information, but does not log the events, alarms and other maintenance issues. In such cases, there is very little documentation which can help the O&M personnel to identify, diagnose and trace the problems.
The importance of O&M is often overlooked by many developers. Considering the fact that the plant has to generate returns over a period of 25 years, a good O&M contractor, a good monitoring system and above all, a very good O&M process is very critical for the success of the plant.