The implementation limitation of variable renewable energies and its impacts on the public power grid

With the increasing proportion of renewable energy represented by photovoltaic (PV) and wind power in the grid, the existing grid has faced some new challenges owing to is intermittent and uncontrollable characteristics. It is important to evaluate the impact of PV and wind on the public electricity supply system when they are introduced into the grid. We present a new method to predict the maximum penetration of renewable energy and its impact on the public electricity supply system from both qualitative and quantitative perspectives. Based on the residual load duration curve method, the new method combines a renewables capacity credit analysis indicator and dynamic investment payback period (DIPP) to explain the impacts on the reduction of peak load and renewables curtailment. Real data were used from the power grids of Kyushu, Tokyo, Kansai, and Hokkaido in Japan. The results indicate that the capacity credit increases with an increase in PV and wind shares in the grid. However, it seems to be saturated when the share of PV and wind power in the grid reaches 25% and 60%, respectively. Compared with the wind integration in Kansai and Hokkaido, the PV penetration in Kyushu and Tokyo reaches saturation more rapidly. In addition, PV shows more power suppression, which prolongs its payback period compared to wind energy. The significant difference in the results of capacity credit and DIPP is limited by the characteristics of power demand in mixed regions and the relevance of renewables distribution.