Study on the Impact of Renewable Energy Technology Innovation on Urban Green Development: A Case Study of the Beijing-Tianjin-Hebei Region

Renewable energy technology innovation (RETI) plays a vital role in transforming economic growth models and promoting urban green development (GD). This paper examines 13 cities at the prefectural level and above in the Beijing-Tianjin-Hebei region from 2008 to 2022, assessing the GD levels of these cities using the entropy weight TOPSIS method. The study investigates the effects and mechanisms of RETI on urban GD through fixed effect models, mediation effect models, and threshold effect models. The results indicate that (1) RETI significantly promotes urban GD in the Beijing-Tianjin-Hebei region, a conclusion that remains valid after conducting several robustness tests. (2) The promoting effect of RETI on urban GD exhibits heterogeneity based on urban resource endowments and spatial layouts, with a more pronounced positive impact in non-resource-based cities and core cities. (3) Mechanism analyses demonstrate that RETI indirectly promotes urban GD in the Beijing-Tianjin-Hebei region by facilitating the low-carbon upgrading of industrial structures and the transition to cleaner energy systems. (4) When R&D investment (RD) is lower than 0.0097, RETI has a clear inhibitory effect on urban GD, meaning that for every unit increase in RETI, the level of urban GD decreases by 0.355 units; when RD is between 0.0097 and 0.0375, RETI exerts a clear positive effect on urban GD, meaning that for every unit increase in RETI, the level of urban GD rises by 0.606 units; however, once RD exceeds 0.0375, the positive effect of RETI on urban GD begins to diminish. In this range, for every unit increase in RETI, the level of urban GD increases by only 0.170 units. When the green policy support index (GPSI) is lower than 0.0427, RETI has a clear promotion effect on urban GD, meaning that for every unit increase in RETI, the level of urban GD rises by 0.171 units; when the GPSI exceeds 0.0427, the promotion effect of RETI on urban GD is further strengthened, meaning that for every unit increase in RETI, the level of urban GD rises by 0.221 units.