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The Hidden Sources of Irradiance Measurement Uncertainty

The Hidden Sources of Irradiance Measurement Uncertainty

In solar energy, performance decisions, contractual guarantees, and long-term financial outcomes all depend on one critical foundation: data quality.

While the industry has made significant progress in selecting high-accuracy irradiance sensors, measurement uncertainty does not end once a sensor is purchased. Installation practices, environmental conditions, maintenance routines, and long-term data management all influence the reliability of the data that operators use every day.

In this interview, Ela Jozsef,  Senior Manager, Strategic Communications & Campaigns  at Kipp & Zonen, speaks with environmental monitoring expert Damon Nitzel about the often-overlooked factors that can impact irradiance measurements and, ultimately, confidence in solar performance assessments.
 

Why Small Measurement Errors Matter

Performance ratio calculations depend on several key inputs, including energy production, irradiance, and module temperature. When uncertainty exists in any of these measurements, it directly affects the confidence stakeholders can place in performance evaluations, forecasts, and financial models. 

As Damon explains, many of the most significant sources of uncertainty are not caused by sensor technology itself. Instead, they often arise from decisions made during site design, installation, operation, and maintenance. These issues may develop gradually and remain unnoticed until they appear as performance discrepancies, investigation costs, or contractual disputes.
 

The Four Areas That Influence Data Confidence

During the discussion, Damon highlights four key areas where organisations may underestimate measurement risk:

Installation Discipline

Even small deviations in sensor levelling, alignment, mounting stability, or maintenance procedures can affect measurement quality over time. Multiple minor errors can accumulate and create meaningful uncertainty in performance data.

Environmental Variability

Solar sites rarely experience perfectly uniform conditions. Factors such as terrain, cloud patterns, tracker positions, module location, and soiling can create variations across a site that may not be fully represented by a single measurement point.

Long-Term Data Governance

Reliable performance analysis requires confidence in the history of a measurement system. Documentation of installation, maintenance, cleaning activities, calibrations, and sensor adjustments helps teams determine whether changes in performance are real or simply the result of measurement drift.

Sensor Uncertainty

Manufacturers play an important role in designing and producing high-quality Class A instruments. However, once a sensor is deployed, its long-term performance depends heavily on how it is installed, maintained, and managed throughout its lifecycle.

From Sensor Selection to Risk Management

One of the key themes of the interview is that irradiance measurement should be viewed as a risk-management process rather than simply an instrumentation decision.

Selecting a high-quality sensor is an important first step, but it does not automatically guarantee high-quality data. Site teams must also ensure that sensors remain correctly positioned, properly maintained, regularly verified, and representative of the modules being monitored.

The discussion explores practical considerations such as sensor placement, mounting quality, levelling verification, cleaning frequency, calibration practices, and documentation procedures that can improve confidence in long-term performance measurements.

Watch the Full Conversation

In the video below, Damon shares real-world examples, lessons learned from utility-scale solar projects, and practical recommendations for reducing uncertainty in irradiance data.

Whether you are involved in plant design, commissioning, operations, maintenance, or performance analysis, this conversation provides valuable insights into improving measurement confidence and supporting more reliable decision-making throughout the lifetime of a solar asset.

 
Divya Maria Sunil
Divya Maria Sunil is a Marketing Campaign & Demand Generation Manager at Kipp & Zonen, bringing a systems-driven and impact-focused approach to marketing. With a knack for deriving insights from data, she shapes thoughtful campaigns and narratives that turn complexity into clarity. Her work centers on creating stories that help people make better decisions and drive meaningful outcomes.
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