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Finland-based Vaisala last week released a paper that compares observational data from nearly 200 ground stations across six continents with satellite-derived irradiance records from five different versions of the company’s global solar dataset.
The company said that the results of the study indicate that Vaisala's values for global horizontal irradiance (GHI) — the key variable for PV projects — have a standard deviation of bias error, or uncertainty, of 4.4-4.9 percent, depending on the version of the dataset.
“Vaisala has been working actively within the energy industry since 2009 to quantify and reduce solar resource uncertainty worldwide," Gwendalyn Bender, head of solar services, Vaisala, said in a statement. "Over the years, we have seen how significantly local factors, such as pollution, dust, or seasonal variation, can influence the accuracy of solar resource information — and thus a project's future solar power generation. In India, for instance, aerosol levels have changed dramatically over the past five years."
Bender also noted that these regional differences are often better captured by using a different aerosol or turbidity input or by employing a different irradiance model.
“By providing multiple, validated datasets that are processed consistently across the globe, our clients can now compare the results to find the solar data source that best fits local conditions,” Bender said.