Fig. 3
From: Burden on hydropower units for short-term balancing of renewable power systems
Efficiency contour of HPP 2 from interpolation of the efficiency measurements and the operation trajectories during the 24 h. The trajectories are from operation strategies S1–S3 with different operating points and governor parameters (Ep2 and Ep3). The efficiency value is normalized with respect to the maximum efficiency value. The black dots show the locations of the operating points in the index test, corresponding to the blue markers in Supplementary Fig. 7 and Supplementary Fig. 8
