Operation & Maintenance Best Practices Guidelines (Version 6.0)

Operation and Maintenance (O&M) has become a standalone segment within the solar industry, and it is widely acknowledged by all stakeholders that high-quality O&M services mitigate potential risks, improve the Levelised Cost of Electricity (LCOE) and Power Purchase Agreement (PPA) prices, and positively impact the return on investment (ROI). Responding to the discrepancies that exist in today’s solar O&M market, the SolarPower Europe O&M Best Practice Guidelines make it possible for all to benefit from the experience of leading experts in the sector and increase the level of quality and consistency in O&M. These Guidelines are meant for O&M service providers, investors, financiers, Asset Owners, Asset Managers, monitoring tool providers, technical consultants, and all interested stakeholders in Europe and beyond.

This document begins by contextualising O&M, explaining the roles and responsibilities of various stakeholders such as operations service providers, asset managers, and maintenance providers, and by presenting an overview of technical and contractual terms to achieve a common understanding of the subject. It then outlines the different components of O&M, classifying requirements into minimum requirements, best practices and recommendations.

Health, Safety, Security, and Environment (HSSE)

Environmental problems are normally avoidable through proper plant design and maintenance, but where issues do occur, the O&M service provider must detect them and respond promptly. Environmental compliance may be  triggered by components of the PV system itself, such as components that include hazardous materials and by-products that may be used by the O&M service provider such as herbicides and insecticides. In many situations, solar plants offer offer biodiversity opportunities for agriculture, and are a valuable natural habitat for plants and animals alongside the primary purpose of power production. However, solar plants are electricity generating power stations and have significant hazards present which can result in injury or death. Risks should be reduced through proper hazard identification, careful planning of works, briefings of procedures to be followed, documented and regular inspection, and maintenance. Personnel training and certification and personal protective equipment are required for several tasks. Almost all jobs have some safety requirements such as fall protection for work at heights and electrical arc-flash, lock-out tag-out, and general electrical safety for electrical work, eye, and ear protection for ground maintenance.

Personnel & Training

It is important that all O&M personnel have the relevant experience and qualifications to perform work in a safe, responsible, and accountable manner. These Guidelines contain a skills’ matrix template that helps to record skills and identify gaps.

Power Plant operation

Operation is about remote monitoring, supervision, and control of the solar PV power plant and it is an increasingly active exercise as grid operators require increasing flexibility from solar power plants. Power plant operation also involves liaising with or coordination of the maintenance team. A proper solar PV power plant documentation management system is crucial for Operations. A list of documents that should be included in the as-built documentation set accompanying the solar PV power plant (such as solar PV modules’ datasheets), and a list of examples of input records that should be included in the record control (such as alarms descriptions), can be found in the Annex of these Guidelines. Based on the data and analyses gained through monitoring and supervision, the O&M service provider should always strive to improve solar PV power plant performance. As there are strict legal requirements for security services in most countries, solar PV power plant security should be ensured by specialised security service providers.

Power Plant maintenance

Maintenance is usually carried out on-site by specialised technicians or subcontractors, according to the Operations team’s analyses. A core element of maintenance services, Preventive Maintenance involves regular visual and physical inspections, functional testing, and measurements, as well as the verification activities necessary to comply with the operating manuals and warranty requirements. The Annual Maintenance Plan (see an example in Annex E) includes a list of inspections and actions that should be performed regularly. Corrective Maintenance covers activities aimed at restoring a faulty solar PV power plant, equipment or component to a status where it can perform the required function. Extraordinary Maintenance actions, usually not covered by the O&M fixed fee, can be necessary after major unpredictable events in the plant site that require substantial repair works. Additional maintenance services may include tasks such as module cleaning and vegetation control, which could be done by the O&M service provider or outsourced to specialist providers.

Common Tests and Inspections

Common tests and inspections are integral to ensuring the performance, safety, and reliability of PV systems throughout their lifecycle. These activities involve routine and specialised assessments to detect issues, maintain efficiency, and prolong the system’s lifespan. This chapter outlines the primary tests performed during the lifecycle of PV systems, key inspection methods, and industry best practices based on international standards such as IEC 62446

Revamping and Repowering

Revamping and repowering are usually considered a part of extraordinary maintenance from a contractual point of view – however, due to their increasing significance in the solar O&M market, these Guidelines address them in a standalone chapter. Revamping and repowering are defined as the replacement of old, power production related components within a power plant by new components to enhance the overall performance of the installation. This chapter presents best practices in module and inverter revamping and repowering and general, commercial considerations to keep in mind before implementation.

Spare Parts Management

Spare Parts Management is an inherent and substantial part of O&M aimed at ensuring that spare parts are available in a timely manner for Preventive and Corrective Maintenance to minimise the downtime of a solar PV power plant. As best practice, the spare parts should be owned by the Asset Owner while normally maintenance, storage and replenishment should be the responsibility of the O&M service provider. It is considered a best practice not to include the cost of replenishment of spare parts in the O&M fixed fee. However, if the Asset Owner requires the O&M service provider to bear replenishment costs, the more cost-effective approach is to agree which are "Included Spare Parts" and which are "Excluded Spare Parts". These Guidelines also include a minimum list of spare parts that are considered essential.  

Data and Monitoring Requirements

The purpose of the monitoring system is to allow supervision of the performance of a solar PV power plant. Requirements for effective monitoring include dataloggers capable of collecting data (such as energy generated, irradiance, module temperature, etc.) of all relevant components (such as inverters, energy meters, pyranometers, temperature sensors) and storing at least one month of data with a recording granularity of up to 15 minutes, as well as a reliable Monitoring Portal (interface) for the visualisation of the collected data and the calculation of KPIs. Monitoring is increasingly employing satellite data as a source of solar resource data to be used as a comparison for on-site pyranometers. As best practice, the monitoring system should ensure open data accessibility to enable an easy transition between monitoring platforms and interoperability of different applications. As remotely monitored and controlled systems, solar PV power plants are exposed to cybersecurity risks. It is therefore vital that installations undertake a cybersecurity analysis and implement a cybersecurity management system. To evaluate monitoring tools, it is recommended to refer to the Monitoring Checklist of the Solar Best Practices Mark, which is available at www.solarbestpractices.com. 

Key Performance Indicators

Important KPIs include solar PV power plant KPIs, directly reflecting the performance of the solar PV power plant; O&M service provider KPIs, assessing the performance of the O&M service provided, and solar PV power plant/O&M service provider KPIs, which reflect power plant performance and O&M service quality at the same time. Solar PV power plant KPIs include important indicators such as the Performance Ratio (PR), which is the energy generated divided by the energy obtainable under ideal conditions expressed as a percentage, and Uptime (or Technical Availability) which are parameters that represent, as a percentage, the time during which the plant operates over the total possible time it is able to operate. O&M service provider KPIs include Acknowledgement Time (the time between the alarm and the acknowledgement), Intervention Time (the time between acknowledgement and reaching the plant by a technician) and Resolution Time (the time to resolve the fault starting from the moment of reaching the solar PV power plant). Acknowledgement Time plus Intervention Time are called Response Time, an indicator used for contractual guarantees. The most important KPI which reflects solar PV power plant performance and O&M service quality at the same time is the Contractual Availability. While Uptime (or Technical Availability) reflects all downtimes regardless of the cause, Contractual Availability involves certain exclusion factors to account for downtimes not attributable to the O&M service provider (such as force majeure), a difference important for contractual purposes.

Contractual Framework

Although some O&M service providers still provide Performance Ratio guarantees, it is best practice to only use Availability and Response Time guarantees, which has several advantages. A best practice is a minimum guaranteed Availability of 98% over a year, with Contractual Availability guarantees translated into Bonus Schemes and Liquidated Damages. When setting Response Time guarantees, it is recommended to differentiate between hours and periods with high and low irradiance levels as well as fault classes, i.e., the (potential) power loss. As a best practice, we recommend using the O&M template contract developed as part of the Open Solar Contracts, a joint initiative of the Terrawatt Initiative and the International Renewable Energy Agency (IRENA). The Open Solar Contracts are available at www.opensolarcontracts.org.

Innovations and Trends

O&M service providers are increasingly relying on innovations and more machine and datadriven solutions to keep up with market requirements. The most important trends and innovations shaping today’s O&M market are summarised in this chapter, grouped into three “families”: (1) Smart PV power plant monitoring and data-driven O&M, (2) Retrofit coatings for PV modules, and (3) O&M for PV power plants with storage.

O&M for Rooftop Solar

All best practices mentioned in these Guidelines could be theoretically applied to even the smallest solar system for its benefit. However, this is not practical in nature due to a different set of stakeholders and financial implications. This chapter assists in the application of the utility-scale best practices to commercial & industrial, and residential rooftop projects. These are shaped by three important factors: (1) a different set of stakeholders – owners of distributed systems not being solar professionals but home owners and businesses, (2) different economics – monitoring hardware and site inspections accounting for a larger share of investment and savings, and (3) a higher incidence of uncertainty – greater shade, lower data accuracy and less visual inspection.