August 30, 2024 | by Brittany Good | Engineering + Technology, NRG Stories, Solar Resource Measurement, Sustainability + Energy
In the fast-evolving world of utility-scale solar projects, accurate meteorological data is more critical than ever. Last month, we introduced a blog series highlighting the critical role this data plays in successful solar development and operation.
In this blog installment, we explore the various types of irradiance measurements – key indicators that directly influence the financial viability and long-term performance of solar projects in the pre- and post-construction phases. The pre-construction phase involves collecting time series data on Global Horizontal Irradiance (GHI), Albedo, and Soiling over months or years to model and optimize different PV installation strategies for a specific site. Post-construction data, including GHI, Albedo, Plane-of-Array, Rear-Plane-of-Array, and Soiling, are used to optimize energy output by comparing expected versus actual performance. By understanding the role these measurements play in solar development, project owners, developers, SCADA providers, and EPCs can make informed decisions that drive efficiency, optimize energy output, and enhance overall project bankability.
GLOBAL HORIZONTAL IRRADIANCE
Applications: Solar Resource Assessment & Solar Resource Monitoring
Global Horizontal Irradiance (GHI) measures the total amount of solar radiation on a horizontal surface, combining both diffuse horizontal irradiance and direct normal irradiance.
GHI bankability impact:
GHI is essential for accurately assessing the solar resource potential at a given location, aiding in site selection and system design. Accurate GHI measurements help in appropriately sizing PV systems, optimizing panel orientation, and determining the optimal tilt angle to maximize energy capture and improve overall system performance. GHI data is also integral to energy production estimation models, which forecast the expected energy generation of a PV system over time. Precise GHI data ensures that energy yield predictions are aligned with actual performance, which is critical for accurate financial planning, securing project financing, and assessing overall system performance. Typically, higher GHI values lead to increased energy production, which directly impacts revenue generation and the financial success of a solar project.
ALBEDO
Applications: Solar Resource Assessment & Solar Resource Monitoring
Albedo refers to the measure of reflectivity of a surface, indicating the proportion of incoming solar radiation that is reflected back into the atmosphere and is an important factor when considering bifacial performance.
Albedo bankability impact:
Accurate albedo measurements are essential for assessing the reflectivity of surfaces around PV installations, enabling more precise predictions of energy output. These measurements also support optimal system design by informing strategies like minimizing structural shading, optimizing site orientation, and considering surface treatments to increase albedo for better performance. As bifacial solar modules have become prevalent in utility scale photovoltaic power plants, accurate albedo measurements play an increasingly critical role in optimizing system design and performance and maximizing energy capture.
IRRADIANCE IN SOILING
Applications: Solar Resource Assessment & Solar Resource Monitoring
In soiling applications, irradiance refers to the intensity of solar that reaches the surface of solar panels after factoring in losses caused by dirt, dust, and other soiling agents.
Irradiance in soiling bankability impact:
Accurate irradiance measurements in soiling conditions provide real-time insights into the impact of dirt and dust on PV panel performance. This data informs effective cleaning procedures and highlights areas for improvement, guiding decisions on maintenance investments, operational strategies, and system management to maximize financial returns. By measuring irradiance, operators can estimate energy losses due to soiling, which is crucial for understanding energy production reductions and potential revenue impacts over time. Timely maintenance, driven by these insights, helps minimize energy losses, optimize system performance, and extend the lifespan of PV systems, ultimately leading to better financial outcomes.
PLANE-OF-ARRAY
Applications: Solar Resource Monitoring
Plane-of-Array (POA) irradiance measures the total solar radiation, including direct sunlight, diffuse light, and ground-reflected light, that is incident on the front surface of a PV module. POA is typically measured for an operating PV plant to assess the irradiance directly impacting the front of the solar panels.
POA bankability impact:
POA is one of the most critical measurements in solar resource campaigns, directly correlating to PV module power output. Accurate POA data allows for precise calculations of the conversion efficiency of solar panels and may help in optimizing the tilt angle to maximize energy output. By assessing POA, project developers can more accurately compare PV performance against expected values, leading to better financial projections and outcomes. Additionally, accurate POA measurements play a key role in predicting and scheduling maintenance by identifying potential performance issues early, which can reduce maintenance costs and improve overall project reliability and returns.
REAR-PLANE-OF-ARRAY
Applications: Solar Resource Monitoring
Rear-Plane-of-Array (RPOA) irradiance measures the total solar radiation, including diffuse light, ground-reflected light, and scattered light from the atmosphere, that is incident on the rear surface of bifacial solar panels. RPOA is critical for assessing the irradiance that reaches the rear side of the panels, contributing to the overall energy generation in bifacial systems.
RPOA bankability impact:
RPOA is crucial for understanding and enhancing the energy contribution and total energy output of bifacial solar panels. Understanding RPOA at the design phase allows for optimizing factors like placement of panels, tilt angle, elevation, and spacing to maximize energy capture. Accurate RPOA data during operation helps determine the impact of surrounding materials and structures on a PV project, specifically how they affect the amount of reflected irradiance reaching the panels. By accounting for these factors, developers can minimize shading losses, enhance overall project performance, and improve energy yield. RPOA measurements also feed into energy production models, enabling more precise predictions of PV output, which in turn supports better financial planning, ROI calculations, and long-term project viability and returns.
NRG Systems’ Irradiance Solutions
Leveraging 40+ years of resource measurement expertise, NRG Systems has established a comprehensive portfolio of meteorological sensors tailored for successful solar assessment and monitoring campaigns. Our extensive product line includes industry-leading pyranometers, reference cell technology, and sun trackers—each designed to deliver precise, reliable data that is crucial for the bankability of solar projects.
The NRG R2 Pyranometer stands out as a class A sensor offering highly accurate solar irradiance data appropriate for GHI, albedo, POA, and RPOA measurements at a competitive price. Its best-in-class response time, user-friendly design, and integrated diagnostics make it the perfect choice for projects when responsiveness, precision, and timely decision-making are essential for success. The NRG R2 is compatible with NRG’s suite of solar solutions, enabling seamless integration and improved access to your critical data.
Whether you are responding to specific RFP requirements or are looking to implement standardized, Class A measurement systems across your project, NRG Systems offers durable, high-performance sensor solutions that ensure seamless integration and consistent results. Backed by our team of experts, we empower customers to optimize their solar campaigns, maximize energy output, and drive financial success from project inception to operation.
This blog is part of a series that will highlight the critical role of meteorological data in building and operating successful utility-scale solar projects. Be sure to read the first installment HERE and stay tuned for the next post in October.