Achieving Commercial Operations in Large-Scale PV Power Systems: Page 3 of 6
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The following are guidelines to help ensure an equitable performance test process, free of misunderstandings, that enables ongoing operations:
- Create and maintain a project closeout team that can meet as necessary during testing to solve immediate problems. The team should consist of knowledgeable members representing the EPC team, supervisory control and data acquisition (SCADA) integrator, owner, owner’s and EPC’s engineers, inverter vendor and tracker provider (if applicable).
- Ensure that project team members have access to any information relevant to system commissioning, including array test reports, inverter burn-in test results, module flash test data and manufacturer start-up test reports.
- Use a dedicated performance testing energy model that represents site and plant conditions at the time of testing and incorporates simulation assumptions and parameters mutually derived by the owner, builder and performance engineering personnel.
- Share all the testing model inputs and outputs—including module files (.pan), inverter files (.ond), shading files (.shd), meteorological files (.met), hourly output data files (8,760 exports) and test target derivations (typically spreadsheets)—and performance test evaluation methods.
- Establish standard testing data downloads that all stakeholders can access.
While this degree of transparency is a departure from convention, we have found that it really works. Sharing the means and methods for testing essentially enlists a team of troubleshooters—an extremely valuable tool—to expedite test and project completion. In the words of one owner: “When we all work together, we have fewer fingers pointing and more fingers fixing.”
Planning for commercial operation starts with a thorough understanding of the contract and performance test requirements. These requirements inform the strategy that project stakeholders use to prepare project documentation, evaluate SCADA requirements, specify and install measurement devices and validate sensors. To the extent that the leadership team understands the deliverables in advance, it can have all the documentation and requirements ready for the field team. This guidance ensures that the project team installs the system correctly the first time and accurately documents key information in the process.
Test implementation starts in the back office, with the procurement of the data acquisition system and measurement devices, and continues in the field as the project nears mechanical completion. These general steps in the process can easily mature into a working, dynamic checklist.
Precommissioning. During precommissioning, assemble a dedicated team, representing all the relevant project stakeholders, to lead the performance testing process. As a team, generate the documents needed for performance testing; create a testing model that is separate from the yearly model; and determine the plant-testing configuration, reporting conditions and targets. Next, review the SCADA and sensor installation plans and specifications to make sure these meet the requirements of the performance test standard. Verify the data collection rate and list of data points for the test. Coordinate with the field crew to document inverter and subarray mapping, and validate input channel labeling and reporting.
Start-up and commissioning. Since the activities in this step start the countdown to project completion, it is important to coordinate with all the stakeholders and set the dates and schedule for performance testing. At start-up, commission and validate the SCADA system and sensor accuracy. Next, troubleshoot the inverters and field wiring. Conclude with a final commissioning to close out any punch-list items, run practice tests, validate performance evaluation tools and verify data streams.
Performance testing. Once everything is working, the project team can determine the start and stop times for the performance test. As data come in, run the analysis, disseminate the data sets, compare evaluations and determine test results. Given decent weather, a transparent process and reasonable parties, you will obtain definitive results: The project will pass or the cause of failure will be clear, and the team can try again after fixing the problem.
Project finalizing. Once the plant passes, the team can finalize the project test results, document the process, develop a baseline performance model for the plant and assemble a final punch list for completion. Organized and meticulous documentation at this stage is critical if the project is to achieve sign-off for commercial operations. This documentation also provides the site records that the owners, asset managers, system auditors and operations teams will rely on in the years to come. Most important, good documentation saves everyone time and money.