Implications of renewable electricity curtailment for delivered costs

At high penetration levels, the ratio of the marginal: average curtailment of an extra MW of wind is typically 3+ times its average. For a portfolio of on- and off-shore wind and solar PV, the ratio is considerably higher. With increasing methods of using potentially surplus VRE (exports, storage) average curtailment falls but the ratio of the marginal: average curtailment rises. The marginal levelised cost of VRE is inversely proportional to the Marginal Capacity Factor, which falls as marginal curtailment increases, raising concerns that reducing average curtailment may not lower the marginal cost of VRE. This paper proves this is not the case. Reducing curtailment has a magnified effect on marginal curtailment and does indeed lower the marginal cost of VRE. • High variable renewable penetration requires curtailment. • Marginal VRE curtailment is 3+ average curtailment. • Marginal cost is inversely proportional to marginal capacity factor. • Marginal:average curtailment rises as average falls with surplus absorbed. • Marginal cost proved to fall as average curtailment falls.