PV System Commissioning
PV System Commissioning
Commissioning is a process that starts during predesign and proceeds through PV system acceptance. Far more than an inverter start-up sequence, commissioning documents the as-built condition of the...
Before commissioning is complete, verify all torque settings. The author is shown here with a torque wrench verifying the compression of grounded dc current carrying conductors inside a Satcon...
In addition to approving installation practices, like proper conduit support spacing and the tightness of conduit fittings, the commissioning agent should document the installation’s as-built...
An infrared thermometer is often the easiest tool for measuring cell temperature. For performance verification testing, average one set of cell temperature measurements at the beginning and another...
As evidenced by this open-circuit voltage measurement, the same personal protective equipment required for building the PV system is required during system commissioning.
The sequence of steps required prior to inverter start-up includes line-to-line, line-to-neutral and line-to-ground measurements at the ac disconnect.
For best results, measure irradiance and inverter ac output simultaneously. This is most easily accomplished with two people. Alternatively, you can set the pyranometer up on a tripod near the...
After measuring cell temperature, irradiance and inverter output power, the author uses a laptop to verify that system performance is within 5% of expected values.
Keep completed commissioning checklists and forms for internal use. The system owner may also require these as part of the O&M or acceptance documentation.
Inside this Article
PV is simple: Turn it on; have sun; make power.
Commissioning may seem like an unnecessarily time-consuming and complex exercise, but it is a critical part of a well-installed system.
Understanding and paying attention to PV commissioning is important to the industry. If the PV industry is to continue to expand and become a significant part of the US energy portfolio, short- and long-term system performance is critical to maintaining public confidence and goodwill. Already, many interested parties are making concerted efforts to maintain the quality control of installed systems. Power Purchase Agreement (PPA) providers, for example, must protect their investments; manufacturers want to see the PV market grow; and legislators and rebate administrators need to encourage responsible industry growth. Integrators, who play such a large role in the story, must do their part to ensure the safety, quality and performance of installed PV systems.
Commissioning is a way to formalize quality control of installed PV systems. The process ensures that systems are safe and high performing. It encourages integrators to be responsible for their installations and facilitates project closeout and prompt payment. Successful commissioning leads to satisfied installers, employers and system owners. Satisfied customers become repeat customers and lead to new clients. Seen in this light, commissioning is essential to the growth of the PV industry and to the overarching goal of installing more renewable energy systems.
Think this is an overstatement? Consider what commissioning prevents. It protects against fires, shocks and injury. It keeps customers happy and minimizes callbacks. It ensures that a lot of silicon, aluminum, glass, steel, copper, dollars and effort are not wasted on nonperforming or underperforming systems. Commissioning guards against a lack of public confidence in PV and renewable energy technologies.
This article covers the commissioning of both residential and commercial scale grid-tied PV systems in detail. Although it does not specifically address off-grid, battery-backup or vehicle PV systems, many of the same principles apply. Similarly, while large utility scale PV systems are not specifically exemplified, the commercial scale procedures are easily scalable.
THE BUILDING COMMISSIONING PROCESS
The commissioning process is typically applied to entire buildings. To set a framework for PV commissioning, it is useful to examine the total building commissioning process. The Building Commissioning Association (BCA) defines commissioning in its sample specification as: "a quality-oriented process for achieving, verifying and documenting that the performance of facilities, systems and assemblies meet defined objectives and criteria. The commissioning process begins at project inception (during the pre-design phase) and continues through the life of the facility. The commissioning process includes specific tasks to be conducted during each phase in order to verify that design, construction and training meet the owner’s project requirements."
Further, the BCA outlines the basic tasks of commissioning:
- Verify that applicable equipment and systems are installed according to the contract documents, manufacturer’s recommendations and industry accepted minimum standards.
- Verify that installing contractors perform adequate operation checkout.
- Verify and document proper performance of equipment and systems.
- Verify that the operations and maintenance (O&M) documentation left on-site is complete.
- Verify that the owner’s operating personnel are adequately trained.
COMMISSIONING PV SYSTEMS
Typically, system owners have specific goals in mind for their PV system. These might include reducing electric bills by a certain percentage, maximizing the power output from available roof space or maximizing return on their PV investment. These goals are known as the owner’s project requirements. The PV system designers then devise a strategy to meet these requirements. This strategy, including documents describing the intended system components and calculated expected performance output, is called the basis of design, which should help guide the PV commissioning process.