Rethinking wind and solar curtailment: past trends, current situations and future estimations

Wind and solar energy curtailment is seen as one of the most important power system issues in multiple countries, and it will grow in importance for electricity systems that are targeting high shares of renewable energy. International cooperation, under the scheme of the International Energy Agency's (IEA) TCP (Technical Cooperation Programme) Wind Task 25 (Design and operation of energy systems with large amounts of variable generation) and its continuation task, Task 63 (Twenty Fifty Integration of Variable Energy), as well as Tasks 14 (Solar PV in the 100% RES Power System) and 19 (Photovoltaic Integration in Electricity Networks and Markets) of the Photovoltaic Power Systems (PVPS) Programme, have been investigating the global situation of wind and solar curtailment for more than a decade. This joint paper includes four topics: (1) proposing unified curtailment statistics, (2) rethinking and redefining curtailment, (3) updating statistics in various areas / countries, and (4) surveying and summarising future curtailment estimates in various country/areas. Specifically, the paper reviews previous publications and discussions on curtailment and rethinks the definition of curtailment. The paper also makes recommendations to governments, regulators and system operators around the world for uniform statistics on curtailment.