Photovoltaics

Suitable planning, supervision and quality assurance activities are critical at all stages of the PV plant to minimise the risk of damages and outages, optimise the use of warranties, avoid dilution of resources and ultimately optimise the overall performance of the PV plant.

In mature markets, where a substantial capacity of photovoltaic plants has been developed, the issue now is to ensure that they are operated in such a way to maximise performance in terms of productivity and return on investment.

The quality of the technology and the O&M practices so far has been highly variable depending on the players involved and the size of the plants, with some large project developers and EPC firms definitely leading the way in terms of organisation, best practices and quality of their plants’ performance.

As the capacity is hugely increasing in many new geographical areas, attracting more and more global as well as local investors, it will be critical for the soundness of the whole PV industry, which is still relatively in its early years, to share effectively know-how, resources and best practices.

“Fortunately this is already starting to happen through all the possible media, such as conferences, trade shows, training programmes, web sources and social media,” says Francesco Belfiore, Principal and European Power Sector Leader at Golder Associates.

Next Big Thing

As for what is going to take utility scale PV plant development and optimisation to the next level, Joshua S. Stein, Photovoltaic System Analysis at Sandia National Laboratories says the next big development in optimising PV plant performance will be in the area of operations and maintenance. Key questions include: What level of monitoring makes sense? How to maximise uptime and still minimise costs? How to use new technologies, such as power electronics, to keep plants running longer and boost lagging performance from component degradation?

Continuous Improvement

According to Belfiore, based on the recent history of PV plants in Europe, a large overall capacity has been developed in a relatively short time, but will have to be operated effectively for a much longer time, in the order of 20 years, during which period the existence and application of sound plans and practices will be able to effect the expected results of the projects.

The growth in the utility scale PV market will be obtained by continued improvement in equipment technology and operational practices that ensure plant reliability and enhanced performance.

“Specific capacity, skills and equipment are quickly being developed to suitably respond to this possibly overwhelming market demand. As a result of the practical experiences in the last few years, resulting also in deeper awareness of the implications of contractual issues on the ultimate performance of the plants, qualifications of critical operators and suppliers are subjected to an increasing scrutiny by the owners,” says Belfiore.

There will also be room for new concepts and solutions in an ever changing context. For instance, the use of suitable energy storage systems will allow better flexibility in order to match the actual demand in case of either reduction or increase. A mix of different storage technologies on the same plant can also maximise its efficiency.

Inexperience

Management of PV plants is still definitely in its early stages, since the bigger and more advanced plants have not been around enough to create sufficient and adequate experience and knowledge.

Golder’s practical experience in PV plant assessment and supervision over the last few years suggests that many issues emerging during the O&M phase are strongly related to the upstream phases of the project lifecycle (siting, development, design, etc.) and may have very significant effects on the downstream phase (performance, production).

Belfiore says the performance of a solar power plant can be addressed and optimised in the different stages of development of a project, from the initial planning through the operation and maintenance.

“Our experience in managing large scale PV plants has shown that an integrated approach over the entire project lifecycle is key to achieve the maximum benefit. The integration should be accomplished throughout the project lifecycle phases (siting, development, design and operation) and across the different tasks, procedures and operators involved in each phase,” says Belfiore.

For instance, EPC and O&M contracts and activities play a significant role in the final outcome of a plant. Contracts stipulated in the early phase of a project usually set minimum guaranteed production parameters that may be too conservative with respect to the potential performance of the plant, in order to avoid excessive risks for the contractor in defining system warranties, and eventually have an impact on the Return on Investment throughout the entire life-cycle of the project for the final investor.

Third party Owner’s Engineers can play a critical role in complementing the overall view and ensuring that the level of integration of the management practices is such to ensure the success of a project.

O&M issues

Suitable planning, supervision and quality assurance activities are critical at all stages of the PV plant in order to minimise the risk of damages and outages, optimise the use of warranties, avoid dilution of resources and ultimately optimise the overall performance of the PV plant.

Belfioresays many of the O&M issues are closely interlinked with the earlier stages of project development and implementation. They can also be of the most different nature, even apparently not directly related to production, and can be broadly referred to classes such as:

Each of these sets of issues can be suitably addressed in order to improve the plant performance. Citing an example, Belfiore says,“In one case for instance, production was stopped for a few days we had to adopt emergency actions on a site that did not have adequate preventive measures for extreme weather events. Designing the site and associated systems for such an occurrence in advanced would have saved quite a significant amount of money.”

Significance of Data

A decent way to improve the operational performance of a plant would be to collect and process effectively the specific data that may allow to plan and direct the O&M actions towards the most critical components and issues.

Belfioresuggests that SCADA systems should be designed to be suitably supplemented with the relevant acquisition systems.

A typical example is the planning of the panel cleaning activities, which may be related to the weather conditions, panel performance records and historical air quality at the site in terms of dust deposition, in order to be programmed at a more effective time.

The data collection system could be coupled with regular visual inspection of the critical parts of the plant to provide useful criteria for addressing specific issues. “We have developed an effective performance audit protocol, which combines historical production assessment, engineering review, instrumental tests and aerial thermographic imaging to supply a complete picture of the opportunities to improve the plant performance,” says Belfiore. 

A proper balance between the detail and depth of the monitoring systems and the plant size and complexity is critical.

All the relevant meteo data, malfunctioning alerts and component performance data (strings, inverters etc.) should be continuously collected and analysed in order to compare the actual plant performance with the contractual targets and possibly fine tune the programming of O&M activities.

The implementation of an independent auditing programme, consisting of site inspections to assess the physical state of the plant components and measurement of relevant technical parameters may help in improving the overall performance.