ROPES: Setting standards for better solar forecasting

With hundreds of solar forecasting papers published in scientific journals over the past decade, there is a consensus that this research area has turned into a valid field of its own.

But, according to Yang, there is an urgent need to improve solar forecasting research practices to make the field a truly credible one.

To address this concern, Yang created ROPES, benchmarking guidelines to facilitate comparison, comprehension and communication. ROPES stands for reproducible, operational (related to power-grid operations), probabilistic (and/or physically-based), ensemble and skill.

The shortcomings of solar forecasting research include the lack of basic understanding in interrelated subject matter. For example, forecasting articles written by researchers with a power systems background do not share the same expertise with meteorologists or solar engineers.

Also, the review process may not be rigorous enough because of inadequate understanding of solar forecasting, which is compounded by questionable or outdated citations.

Yang tested ROPES against 79 articles in six energy journals from January 2017 to July 2018. The journals were chosen because they jointly have published the most solar forecasting papers, according to an earlier bibliographic study on solar forecasting literature.

Based on the findings, reproducibility was evident in only four of the papers while operational forecasting was found in 15 papers.

“Solar forecasting needs to be easily reproducible and operational, and so the results show a major pitfall in these areas,” Yang said.

Ensemble was the most achieved characteristic in terms of machine-learning ensembles and forecast combinations, largely the result of the growing popularity of machine-learning algorithms and other software packages. However, Yang said, simple hybrid models that do not advance the field should be avoided.

Source: “A guideline to solar forecasting research practice: Reproducible, operational, probabilistic or physically-based, ensemble, and skill (ROPES),” by Dazhi Yang, Journal of Renewable and Sustainable Energy (2019). The article can be accessed at https://doi.org/10.1063/1.5087462 .