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While much of the utility-scale PV sector is embracing performance benchmarks in order to assess Operations and Maintenance (O&M) performance and drive up plant availability, a lack of comprehensive standardized performance metrics is limiting potential gains.

Key Performance Indicators (KPIs) help to underpin supply guarantees, provide performance comparisons over time and between plants, and measure the efficiency of O&M services.

“If we can use the same KPIs, we would have additional benefits because we see a lot of consolidation in the market, and all these companies would like a common base to measure and compare the performance of the assets,” Vassilis Papaeconomou, managing director at Alectris, a solar asset management service provider, said.

Papaeconomou was among a group of European industry leaders consulted by SolarPower Europe to produce the ‘O&M Best Practice Guidelines for PV solar plants.’

The guidelines, published in June, propose basic universal performance metrics for professional O&M services. The report collated views from O&M Service Providers, Asset Owners, Asset Managers, Technical Advisors and manufacturers.

Since there is currently no standardized ‘Availability’ calculation, engineers must often review how Availability is defined and calculated in order to establish performance guarantees, according to Heidi Marie Larson, director of Solar Generation at Leidos' Renewable Generation Services division.

Availability benchmarks currently in use typically range from around 95% to 100%, according to industry experts.

“Availability is probably the most common metric that we see in O&M providers' performance measurements, though the industry has not yet standardized how Availability for a PV plant should be determined, and what should and should not be included,” Larson noted.

Full coverage

The European O&M Best Practice Guidelines distinguish between Plant Performance KPIs which “directly reflect the performance of the plant and are under the duties of the O&M Contractor” and O&M Contractor KPIs which “reflect the performance of the service.”

While the Plant Performance KPIs are quantitative and measure the plant performance ratio, plant availability, uptime and energy output, the O&M Contractor KPIs are both quantitative and qualitative.

Performance should be rated against the indictors and translated into bonus schemes and liquidated damages, ensuring the asset owner will be compensated for poor reaction times or availability performance, the guidelines said.

    Examples of Availability-related Bonus Schemes and Liquidated Damages

Source: SolarPower Europe's 'O&M Best Practice Guidelines for PV solar plants'

In addition to KPI formulas, operators have to consider all the O&M activities and events that can't be measured through automated systems to accurately establish performance, Papaeconomou said.

“Automated monitoring systems can be a bit far from reality…It is quite easy to do a calculation, you can do that in a spreadsheet, but what you have to make sure is that the data put into the system is reliable, and you also have to include other activities that are not collected automatically by the system,” he said.

Going forward, O&M performance indicators should include more qualitative data such as response times, resolution times, costs and maintenance tasks, Papaeconomou said.

Effective metrics

Global PV developer First Solar adopts separate KPIs called Effective Availability and Performance Index to provide a comprehensive view of plant performance.

Effective Availability takes into account energy lost due to outages to provide an indication of how the plant is influenced by component quality, plant design, as well as the “effectiveness of the operations and maintenance team,” Kirby Hunt, performance engineering manager in the energy services division of First Solar, told PV Insider.

The Effective Availability of First Solar’s fleet has averaged 99.5% over the past few years, and the company has seen plants built by others “with much worse records,” she said.

The Performance Index is calculated by the measured plant energy divided by modeled energy, and gives an indication of how efficient the plant is working compared to its design.

A Performance Index benchmark should be set at around 100%, according to Hunt. First Solar's fleet had an average of about 101.5% over the last year.

Performance Ratio is another KPI adopted by some operators, but First Solar doesn't use this in the U.S. because it is influenced by ambient temperature, plant location, and other variables that make it tricky to compare data between power plants, Hunt noted.

The International Renewable Energy Agency (IRENA) has predicted that Levelized Cost of Energy from PV plants could fall by 59% by 2025 and cost reductions will be increasingly driven by O&M costs following a sharp fall in solar PV module costs in recent years.

A convergence of performance benchmarks will provide greater transparency for operators as O&M competition intensifies.

By Anna Flávia Rochas