Solar Energy: Improving Power Prediction Accuracy

When developing a utility-scale solar PV project, accurately projecting the site’s power output is crucial. For its 33 MW Kumenan PV project in Japan, Pacifico Energy experimented with publically available data before seeking a more precise measurement solution.

After implementing SRA Systems from Renewable NRG Systems (RNRG)—a designer and manufacturer of decision support tools for the global renewable energy industry—Pacifico Energy increased the accuracy of power output projections at the Kumenan PV project by up to 14%. The gain allowed the company to secure more competitive financing terms to build the PV plant. 

As the utility solar industry continues to grow, the need for solar resource assessment to facilitate more accurate power output forcasting is becoming increasingly important. The most critical parameter used to estimate power output is Global Horizontal Irradiance (GHI).

Because of its direct impact on energy production estimates, miscalculations of GHI can cause critical financial risk for project owners and investors. When Pacifico Energy first set out to determine power output at the Kumenan PV project, they used publically available, long-term GHI data from New Energy and Industrial Technology Organization (NEDO). Such resources are common in Japan, but are not ideal for every project.

In Pacifico Energy’s case, the weather stations used by NEDO to collect GHI data were located too far from the Kumenan PV project to provide accurate output projections. Instead, they selected an approach that aligns with the solar industry’s GHI measurement best practices, integrating the high-quality irradiance data collected onsite with RNRG’s ground-based SRA Systems with long-term satellite data. According to Nate Franklin, who manages Pacifico Energy’s activities in Japan, ”Deploying finance-grade solar assement campaigns like this one is fairly new in Japan, but Pacifico Energy wants to lead the way towards a high-standard approach to PV project development in the country.”  

Pacifico Energy opted for RNRG’s solution because of its exemplary quality, reasonable cost, and its ease of installation and maintenance. The SRA Systems were installed at the Kumenan PV site in 2013 and collected real-time irradiance data for one year. The monitoring station was equipped with best-in-class meteorological sensors that integrated seamlessly with RNRG’s much-lauded SymphoniePLUS3 data logger, providing measured data directly to Pacifico Energy’s control room. The long-term satellite data were later corrected with the records collected by the SRA Systems, providing the most accurate irradiance input to energy production simulation model. “The SRA System configuration that is used here is recommended for utility-scale resource assessment campaigns and solar monitoring applications when measurement accuracy is the top priority,” said Dave Hurwitt, VP Marketing & Product Management at RNRG. “Pairing RNRG’s solution with satellite data ensures that deviations between predicted irradiance and actual site conditions are minimized, which is extremely beneficial for PV project developers.”

Once the solar assessement campaign reached completion, Pacifico Energy concluded that RNRG’s SRA Systems helped improve the long-term GHI estimation by up to 14% when compared with the irradiance data collected by NEDO weather stations alone. The Kumenan PV plant has been in operation since early 2016 and power output has closely mirrored RNRG’s predictions. The impressive resource assessment accuracy at the Kumenan PV project led Pacifico Energy to install RNRG’s SRA Systems at six other projects in Japan. “This way, we can ensure that all of our projections reflect reality,” added Franklin.