Are China's renewable energy products complementary with those in the “Belt-and-Road” countries under trade protectionism?

In this study, we first measured the complementary relationship between China and the major Belt-and-Road Initiative (BRI) countries in renewable energy products by adopting Trade Combined Degree, Export Similarity Index, and Trade Complementarity Index based on UN Comtrade data. Then, we conducted a heterogeneity analysis of the complementary factors by using regression and correlation analyses. The results show that: (1) China and the BRI countries have a high degree of trade integration. China has a strong dependence on the BRI country market, with great complementarity differences in different regions; (2) from the perspective of evolution, the renewable energy product trade between China and BRI countries illustrates a weakening complementarity and intensifying competition trend; (3) there is a high degree of complementarity between China and ten BRI countries in terms of renewable energy product trade. The major factors influencing the complementarity are the total population, the gross domestic product of importing countries, renewable energy generation capacity, and energy consumption; and (4) from the perspective of different energy types, solar energy products have the strongest complementarity, while biomass energy products have the weakest complementarity. Finally, we put forward corresponding policy recommendations based on the above findings.