The Importance of Commissioning and Testing on Utility Scale Projects

Utility scale solar projects are years in the making from inception to completion. The process typically includes land development, interconnection studies, environmental evaluations, securing financing, materials procurement, and construction. The final step before a system is fully operational is commissioning and testing. 

This is an integral step as it ensures a proper handoff to the owners of the solar power plant. It establishes the baseline operating levels of the system, checking that each part of the system is operating at the proper specifications. It is critical to the safe and effective operation of a solar power plant while confirming that it meets generation targets for the customer. 

Commissioning is a well-documented and controlled process to initiate the operation of a solar PV plant and record plant capability to meet the designed performance requirements. 

While there isn’t a standard or requirement for exact tests included in every utility scale solar PV plant commissioning process, we will walk through a handful of the most common ones.

Commissioning begins with pre-functional checks which are highly detailed quality checks to ensure that key electrical components are installed properly. This initial step physically verifies that the commissioning team may move on safely to subsequent steps in the process.

Grounding testing and inspections are performed to ensure that the system is safe for people and equipment. When installing solar PV systems, it is important to ground the solar arrays and the equipment. Insufficient grounding is dangerous and increases the risk of electric shock for individuals working on the system. Improper grounding also increases the risk of equipment failure. 

One example of grounding testing is fall of potential testing. This is used to measure the ability of an earth ground system to dissipate energy from a site. On a utility scale site, this is generally done at each equipment pad where the inverters and transformer are located.

I-V curve tracing measures the relationship between current (I) and voltage (V) on each of the strings while the tracer sweeps an electrical load, running various voltages through the string. The data is then used to plot an I-V curve to compare what is expected for each string with the actual output. I-V curve tracers also measure irradiance and temperature so that technicians can compare the module manufacturer’s I-V curve, which is listed at Standard Test Conditions (STC), with the site conditions happening in the field. 

Performance testing typically involves allowing the solar power plant to run for a 72-hour period. Generation data is collected along with real-time irradiation and temperature data. Expected output and actual output are compared side-by-side to confirm that the system can meet the guaranteed capacity requirement specified in the contracts. Performance testing is typically repeated on an annual basis to ensure that the system continues to meet production expectations. 

Commissioning work is always documented using photos, checklists, and data logging sheets. On large sites, this documentation is extensive. It’s important to keep data organized and properly stored as these documents will likely be referenced many times over a site’s 20+ year lifespan. 

Interested in learning more about utility scale commissioning and testing? HeatSpring instructor Andy Nyce has extensive experience in solar engineering, construction, project management, and quality control in the large scale renewables industry. He teaches a course on Utility Scale Solar Construction & Project Management, where he covers the development, design, permitting, construction, and commissioning of utility scale solar power plants, including a deeper dive of the commissioning and testing process.

Additionally, the North American Board of Certified Energy Practitioners (NABCEP) offers a PV Commissioning & Maintenance Specialist Certification which highlights expertise in operations, maintenance, and commissioning. It spotlights the ability to apply verification protocols, critically analyze systems, and implement preventive and corrective maintenance procedures for PV systems.