A team of researchers from Utrecht University analyzed offshore floating photovoltaic (OFPV) systems to determine the reasons for the improved performance compared to land-based systems. Based on their research, the group developed two regression models that help predict the return benefits when investing projects.
“While technology and mounting method are also important, our approach aims to develop a model that neutralizes these effects and isolates geography as a determinant of solar PV performance and differences between offshore and onshore power installations,” the team said in their report. Two different methods were used to find the correlation between independent variables and OFPV benefit: Multiple linear regression (MLR) and multivariate polynomial regression (MPR).
Analyzing temperature differences between offshore and inland sites in 20 port cities, the team found that in almost all sites, the water cooling effect resulted in lower module temperatures for OFPV sites that used a steel pontoon structure. In addition, in 70 percent of the sites, the average radiation value of offshore systems was higher than that of land-based systems. The report states that even in areas where the average radiation level of offshore areas was relatively lower, only 20% of them resulted in a negative energy yield gap.
To simulate the expected offshore performance benefits, the researchers selected locations around the world in different continents and climate zones. For each site, they used historical data on irradiance, temperature and relative humidity from the Nasa Power database – collected from January 2008 to January 2018. “We calculated the energy yield benefit equivalent to 1 MWp of panels. For this, an area of about 5,200 m would be needed, all of which would be placed horizontally on top of the various connecting pontoons, assuming we use a 310 Wp module,” the report states.
The average energy yield difference over a 10-year period varied between 20% and -4%, depending on the objects used. “The most important finding of this study about the energy advantage between offshore and onshore power systems is that the energy advantage is clearly site-specific. In addition, we developed a meaningful regression model that quantifies a very clear correlation between several geographic and meteorological values and the energy disadvantages of using solar panels offshore,” the report emphasizes.
The researchers concluded that OFPV is not the most viable option in some places on Earth, and that although the investment and installation costs of OFPV are higher compared to land-based systems, offshore systems do not incur the cost of land.
The paper states that “in some use cases, offshore FPV construction may appear promising, and in such situations, access to a geographic regression model such as this one will help decision makers better understand their options.”
Their findings are available in the research paper “Offshore floating Photovoltaics system assessment in a world perspective”, which has been published Advances in solar power.