Soiling losses are easy to assume but difficult to quantify accurately. Many O&M teams attempt to infer soiling directly from raw SCADA data, only to find the signal obscured by sensor noise, poor normalization, or unverified operating conditions. This is where Acceptance Performance Test–level evaluations become essential.
In many cases, the most defensible reference is the model established during solar acceptance testing, when the facility was new, clean, and operating as intended. McHale supports solar plant acceptance test execution and acceptance-based model development as part of project closeout. That baseline can then continue to support operations through simplified periodic evaluations, including a year 1 solar performance test, solar baseline performance testing, and broader 1-year solar monitoring and reporting.
Acceptance Performance Testing establishes a validated performance baseline using calibrated instrumentation, defined normalization methods, and quantified uncertainty. We perform these tests at COD and support follow-up performance evaluations that reuse the same baseline and analytical framework.
Where appropriate, those evaluations can also draw on PVsyst modeling services, a utility-scale PVsyst model, and regression-based methods used for solar performance validation. When supported by project requirements, the framework can align with ASTM E2848 solar testing and other forms of defensible solar performance testing used for owner reporting, contractual review, and commercial risk management.
By reusing the original acceptance model within the SolCertus performance analytical service, current performance can be compared to a known, high-quality benchmark. Module cleaning can then be triggered by measurable degradation that economically justifies the work, rather than by a calendar date alone. At the same time, the same review helps determine whether the observed loss pattern is more consistent with soiling, sensor bias, or equipment underperformance.
This approach turns acceptance work into an ongoing operational tool. Instead of relying on fixed intervals or site impressions, owners can use analytically grounded performance review to decide whether to clean, investigate equipment, or prioritize another corrective action first. That makes SolCertus valuable not only for routine maintenance decisions, but also for solar performance guarantee validation, solar project de-risking, and owner-side oversight.
During periodic evaluations, selected instruments may require field verification or recalibration to ensure data remains comparable to the original acceptance results. This step is critical for maintaining apple-to-apples comparisons over time.
Without this foundation, apparent soiling losses are frequently misattributed. Common root causes include:
- Irradiance sensor bias
- Module temperature measurement errors
- Tracker misalignment
- Inverter operating degradation
- Other underlying equipment issues
By directly comparing current normalized performance with the Acceptance Performance Test results, operators can isolate genuine soiling effects from these confounding factors. When deviations exceed the defined uncertainty bands, they can be acted on with confidence.
Accurate soiling detection is not about adding more sensors or dashboards. It starts with validating the performance model at acceptance—and carrying that rigor forward into operations.
Why it matters
- Supports utility-scale solar performance testing beyond commissioning
- Extends the value of solar acceptance testing into operations
- Improves solar performance troubleshooting by separating soiling from equipment-related losses
- Strengthens solar performance validation with defensible baseline comparison
- Helps busy fleet teams prioritize the right corrective action faster