Achieving Commercial Operations in Large-Scale PV Power Systems

The common goal of PV industry stakeholders is to deliver high-quality, reliable energy assets. But do planning and testing methods support this goal?

A PV project’s transition from the construction phase to the operations phase is a flurry of activity. Project stakeholders must coordinate schedules, materials, trades, troubleshooting and testing while adhering to design documents, contractual requirements and project milestones. As such, the sprint to achieve commercial operations is a busy time with many challenges. The shared goal is to get the project to the commercial operations date (COD), the point at which the asset begins to generate revenue.

As independent engineers, we work alongside all of the project stakeholders—owners, financiers, and EPC firms—to help steward large-scale PV projects to the finish line, the COD milestone. We have participated in projects where partners from all trades and disciplines walked away with a profound feeling of satisfaction. We have also seen some unmitigated disasters, which left all project team members frustrated and at significant financial risk.

The worst-case scenario is when a project falls short of its performance test goals and the remedies are not readily apparent. This performance-related impasse is a precarious place to be at the end of a project. The resolution usually takes place at a conference table—or, worse, in a room full of lawyers—and involves discussions of liquidated damages. When projects get to this point, there is little that we as independent engineers can do to solve the problems. This article’s goal is to help you avoid such an impasse.

Here we share lessons learned from our project completion experiences, both good and bad, and our recommendations for a more elegant path to commercial operations, one that starts with the performance-test milestone in mind. While there are many possible paths for getting a project into operation, we frame our discussion around performance testing because this is the last big step before a PV project achieves COD. Our experience is that a collaborative and transparent performance evaluation process that fairly allocates risk delivers high-value PV assets while minimizing conflict and financial risk. While we are not contending that an open project–delivery model eliminates problems, we can certify that it solves problems much faster than more antagonistic approaches.

Performance Testing

The goal of performance testing is to benchmark system performance against a set of contractually mandated performance parameters such as system capacity, efficiency (performance ratio) and energy yield over time to ensure that a PV asset will meet owners’ performance and financial expectations. A successful performance testing process saves time, money and resources. It also provides valuable baseline information for ongoing operations. (See “PV System Energy Performance Evaluations,” SolarPro, October/November 2014.)

Unrealistic expectations—often based on proprietary energy models, weather data files and evaluation tools—are the most common cause of end-of-project delays. For example, we have been involved in projects that stretched performance expectations for every subsystem to their physical limits, tacitly requiring chronic overperformance to achieve a passing evaluation.

Performance testing is especially onerous when the terms and conditions effectively require that all subsystems must perform at or above expected efficiency; module capacity must exceed nameplate power ratings; modules must be perfectly clean for the duration of the test; dc, ac, inverter and transformer losses must be at or below expected levels; and, most problematically, all measurements must be perfectly representative and accurate with no uncertainty. These requirements are not an exaggeration, but rather an example of what happens when one party dictates all contractual testing and completion terms.

The scramble to meet a nearly unattainable goal is unbelievably expensive. One-sided terms are a setup for disappointment and contribute to an antagonistic project delivery model that we believe is both counterproductive and avoidable. Unreasonable or unattainable goals do not improve system performance.


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